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NBS SPECIAL PUBLICATION 459

. U.S. DEPARTMENT OF COMMERCE / National Bureau of Standards'
NATIONAL BUREAU OF STANDARDS

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i^'' Performance Evaluation of

Programmable Robots and Manipulators

Report of a Workshop held at Annapolis, Maryland

October 23-25, 1975

Edited by

Thomas B. Sheridan

Thomas B. Sheridan and Associates

32 Sewall Street West Newton, MA 02165

U.S. DEPARTMENT OF COMMERCE, Elliot L Richardson, Secretary

Edward O. Vetter, Under Secretary

Dr. Betsy Ancker-Johnson, Assistant Secretary for Science and Technology

V) . 5. NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Acting Director

Issued October 1976
Library of Congress Catalog Card Number: 76-600057

National Bureau of Standards Special Publication 459

Nat. Bur. Stand. (U.S.). Spec. Publ. 459, 213 pages (Oct. 1976)

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ABSTRACT

The Workshop brought together representatives of industry, academic institutions and

government agencies, including the potential designers, suppliers and users of a new generation of manipulators and robots which include varying degrees of control by both

people and computers. The Conference was motivated by the lack of common bases for com- paring one such device with another in terms of performance, or one task with another in terms of how well a given device will perform it.

The Workshop concluded that there is a need for (1) common definitions of many terms which

now are the source of pervasive confusion, (2) common test codes, (3) checklists, guidelines,

and specifications to help users and suppliers better communicate with one another, and

(4) common tests for demonstration and exhibition of new research and development in this

field. Conference participants emphasized that once these needs were met to allow communication in the field, actual performance testing should be left to the user and supplier

in the free marketplace.

KEY WORDS: Guidelines; industrial robots; manipulator; performance evaluation; programmable

robots; and specifications.

Certain commercial products and instruments are identified in this paper in order to specify

adequately the experimental procedure. In no case does such identification imply recom- mendation or endorsement by the National Bureau of Standards, nor does it imply that the

products or equipment identified are necessarily the best available for the purpose. .

iii
PREFACE

During the past few decades, robot systems have advanced from the imagination

of science fiction writers to the reality of industrial robots and remote control

manipulators at work by the thousands in industry and in Government facilities today.

This new technology of computer controlled automatic manipulators is characterized

by its generality. The same industrial robot that is found loading red hot steel ingots

into forging presses in one industry is found spot welding automobile bodies in another.

The combination of complexity and generality of such systems poses a problem to the potential user. How should he specify the design or performance of such a device

for procurement? Too detailed a specification will result in an expensive, custom

designed system. On the other hand, too loose a description may result in a system

that doesn't perform adequately.

Government agencies face an even more difficult problem in the development of

advanced systems for handling radioactive materials, exploring other planets, mining

offshore drilling and undersea exploration, and handling explosives and other dangerous

materials

.

Today's marketplace for robots and programmable manipulators is characterized by

a lack of quantitative performance measures and even the lack of a basic common vocabulary

for specifying performance.

To address these problems, the Office of Developmental Automation and Control Technology

of the Institute for Computer Sciences and Technology of the National Bureau of Standards

contracted with Thomas B. Sheridan and Associates to organize a workshop that would bring

together selected experts from Government, industry, and academic research groups. Prepared

papers were solicited to address specific aspects of the problem, and a two day workshop

was held to discuss the papers and identify specific problems to be solved.

The papers in this proceedings do not represent the viewpoint or official position

of the National Bureau of Standards. They are the personal opinions of experts in the

field that identify specific needs in developing a common vocabulary, guidelines and

performance measures that will improve the communication in the marketplace for robot

systems and programmable manipulators.

The Office of Developmental Automation and Control Technology develops guidelines,

standards, and performance measures that will assist other Government agencies and

Industry in specifying, procuring, and using computer based automation systems, including

robot and programmable manipulators. We believe that these proceedings, which are one of the ways in which we endeavor to provide this assistance, will be useful to Government, to industry, and to the research community in improving their ability to discuss the performance capabilities of robot and programmable manipulators.

John M. Evans, Jr. Acting Manager

Office of Developmental Automation

and Control Technology

Institute for Computer Sciences

and Technology

National Bureau of Standards

iv
TABLE OF CONTENTS

1. Introductioa

2. Summary of Workshop

2.1 Objectives

2 . 2 Program

2.3 Conclusions and recommendations

3. Review of Presentations and Discussions

4. Quoted Responses of groups and individuals to theme questions

5

5

5

Papers submitted

5.1 General manipulator design and evaluation considerations

5.1.1 Evaluation of tools and tasks: reflections on the

problem of specifying robot/manipulator performance,

T.B. Sheridan

5.1.2 Performance evaluation of manipulators from a kinematic viewpoint, B. Roth

5.1.3 Performance evaluation of ROMANSY (manipulator-robot

systems) from the viewpoints of mechanics and control,

A.E. Kobrinski

5.1.4 Performance measurement and evaluation of general

purpose manipulators, R.L. Paul

5.1.5 Manipulator system performance evaluation: problems and

approaches, N.L, Shields, Jr., T.B. Malone, and M. Kirpatrick

5.1.6 Research on remote manipulation at NASA/Ames Research

Center, W.L. Verplank

5.1.7 Experience and remarks on manipulator evaluation, J. Vertut

5.2,3 Servicing of industrial robots - the modular concept,

M.S. Konstantinov

5.3 Nuclear Applications

5.3.1 Characteristics and evaluation of master-slave manipulators,

D.G. Jelatis

5.3.2 Design and performance requirements for reactor fuel

recycle manipulator systems, J.G. Grundmann

27

39

63

69

83

91

97

5.2 Industrial Robots

5.2.1 Performance evaluation of industrial robots, J.F. Engelberger ^^-^

5.2.2 Robots for automated production of conventional ammunition,

D.A. Morlock

123

5.2.4 A computer-aided robot operation systems design (Part 1), Y. Hasegawa, I. Masaki, M. Iwasawa

141

147

5.3.3 Master-slave manipulators and remote maintenance at the

Oak Ridge National Laboratory, R.G. Jenness & C. D. Wicker

V
5.4 Space, undersea and medical applications

5.4.1 Performance evaluation studies at JPL for space manipulator

systems, A.K. Bejczy 159

5.4.2 Performance measurement for undersea systems, A.J. Pesch

and W,R. Bertsche 175

5.4.3 Contribution to forming criteria for the evaluation of

robots and manipulators, M. Vukobratovic 197

APPENDICES

Appendix 1. Address list of workshop participants 205

Appendix 2. Workshop program 207

Appendix 3. Sample government specification of manipulator 209

Appendix 4. Japanese Industrial Robot Association standardization plan

for industrial robots 215

vi
1 . INTRODUCTION

The designer or supplier of a general purpose programmable robot or manually

controlled remote manipulator (teleoperator) has a difficult problem. He would like his

device to fit a great variety of applications, for its very versatility to adapt to whatever specific job the user may have is what makes it economically viable. Yet he

knows each particular job is different. Beyond the general desire for ever greater speed,

accuracy, strength and reliability he lacks precise specification of an objective

function or performance criterion. He is largely dependent on the programming and

operating skills of his customer in order for his product to succeed.

Similarly, the purchaser of a programmable robot or manipulator has a problem.

He is not clear on how to decide which available system is best for him, for he doesn't

know how best to specify what he needs. If he specifies required performance in terms

of the most recent or the present task, it is not likely that the robot will be

adaptable to other tasks in the future, not that it will perform well with respect to aspects of today's task which he does not understand well enough to specify. Alternatively,

the purchaser can specify for procurement in terms of some "worst anticipated case",

e.g. "pick-up the (heaviest) object in the (most arbitrary) location and orientation, move it (in the least time) and make the (tightest tolerance) assembly to another object

(whose position is poorly known)!' However, requiring that the robot be designed as though it is to work regularly at this rare simultaneous extremum of all the performance

variables is likely to be naive economically. In those rare cases of an extreme in terms of one variable (weight or speed, etc.) some other variable may well be able to give, and the greatest pay-off is likely to come with a system designed primarily for

the kinds of jobs it faces most often. Finally the purchaser can defer judgement until

after he has purchased a robot or manipulator system and had a chance to try it out.

Programmable robots and manipulators are relatively general purpose tools,

intended to be adapted to a variety of future tasks in ways limited primarily by

ingenuity of their programmers and human operators. This fact, however, only aggravates

the problem of specifying performance of devices yet to be built or of evaluating

performance of those already built. It only complicates the process by which supplier

and user can make agreements to which they can be held accountable.

How should performance be measured? In terms of the physical attributes of the

tools, such as geometry, speed, load, controlability , reliability, cost? Or in terms

of various tasks to be accomplished, perhaps "real" demonstration tasks, consisting of

integrated sequences of component subfeasks - or perhaps a battery of discrete

component tasks, each of which can be calibrated and scored separately (for accuracy,

time, etc.), a sort of "aptitude test" or "I.Q. test" for robots? Should robot

capabilities be specified in terms of a "resume" of accomplishments, much as a human

job applicant?

Different governmental or industrial programs already have produced ad-hoc

performance evaluations of a great many specific systems, and there is considerable

experience already gained in terms of types of measures and criteria employed,

types of decision problems faced, etc. Yet there remains little or no consensus on performance measurements and evaluation across sectors of industry and government in

the U.S. (though national "standardization" efforts have begun in some other countries,

e.g. Japan).

The National Bureau of Standards, Department of Commerce (Office of Developmental

Automation and Control Technology) recognizes a need to develop a better understanding

of problems of measurement and evaluation of performance of programmable robots and

manipulators. This should include work to secure agreement on common yardsticks and

language in addressing these problems across relevant research, development, manufacturing

and using communities, including: manufacturing (materials processing, parts handling

and assembly, inspection, warehousing) ; service industries (trash collection, vehicle

loading, building maintenance and construction) ; hazardous environment operations (deep

1
ocean oil drilling, work in high temperature or chemically toxic environments,

nuclear "hot lab" operations, space operations in earth orbit or on the planets); "remoted"

micro-surgery; mining and many others.

Clearly the development of conventional "standards" for use by government or industry

would be premature at this point. The need at' this time is rather to define and

understand the problems, and for a sharing of measurement techniques and evaluation

experience among interested parties.

To this end a Workshop on Performance Evaluation of Programmable Robots and

Manipulators was sponsored by the Office of Developmental Automation and Control

Technology, Institute for Computer Sciences and Technology, National Bureau of Standards,

U.S. Department of Commerce, Washington, D.C. 20234. Through Contract No. 5-35922,

Thomas B. Sheridan and Associates, 32 Sewall St., W. Newton, MA 02165, served as organizer. Dr. John M. Evans, Jr. was contract monitor. The Workshop was held Oct.

23-25, 1975 at Annapolis, Maryland.

Attendeees at the Workshop (full titles and addresses given in the appendix) were:

James Albus National Bureau of Standards

i\nx^nuny uclluglls. National Bureau of Standards

Antal Bejczy Jet Propulsion Laboratory

Alan Case General Electric Co. Jos. F. Engelberger Unimation, Inc. junn r1 . HiVano iNoUxunai. 0ureau or ouanuarus

jaCJv vj . Lrxrunuiuann ueijx i\i.cLgc iNaui.ona 1 LiaDorauory

wxiiiam riamei Oak Ridge National Laboratory

Dennis Hanify ITT Research Institute

Richard E. Hohn Cincinnati Milacron Co. Demetrius G. Jelatis Central Research Laboratory

P, Michael Lynch Charles Stark Draper Laboratory

Gerald Malecki Office of Naval Research

Douglas A. Morlock Picatinny Arsenal, U.S. Army

Richard L. Paul Stanford Research Institute

Alan J. Pesch Eclectech Associates

Andreas Rechnitzer Office of the Oceanographer, U.S. Navy

Bernard Roth Stanford University

Bernard M. Sal lot Society of Manufacturing Engineers

Thomas B. Sheridan T.B. Sheridan Associates

Nicholas Shields, Jr. Essex Corporation

William L. Verplank Stanford University

Jean Vertut Atomic Energy Commission of France

Charles D. Wicker Oak Ridge National Laboratory

2
The following individuals contributea written statements (which are printed in

Section 5 along with the other papers):

Y. Hasegawa

I, Masaki

M. Iwasawa

A.E. Kobrinski

M.S. Konstantinov

Waseda University

Kawasaki Heavy Industries, Ltd.

Oki Electric Industry Co. Ltd.

Academy of Sciences, U.S.S.R.

Central Laboratory of Manipulators and Robots,

Bulgaria

M. Vukobratovic Mihailo Pupin Institute, Yugoslavia

The contributions of Ms. Helen Stottlemeyer , Ms. Marie-France Pierre and Ms. Toni Heller in administrative assistance and typing are gratefully acknowledged.

3

2. SUMMARY OF WORKSHOP

2.1 Objectives

The objectives of the workshop were:

1, to motivate the preparatioa of position papers on robot and manipulator

performance evaluation by key persons representing industry, government

and university, as well as both supplier and user in major application areas;

2, to provide an opportunity for the above persons to discuss each others'

viewpoints and come to a better mutual understanding of current practices and

problems in robot/manipulator performance evaluation;

3, to collect written responses of individuals and small working groups on theme

questions (responses presented in Section 4)

:

Question 1 : How can the specification of performance of relatively general

purpose robots and manipulators be improved (so that the supplier can specify

his product's capabilities and the user can specify his task requirements

and each can be held accountable?)

Question 2 : What terms, tests and indices used for performance measurement and

evaluation can be common across the various types of devices and fields of

application (e.g. manufacturing, mining, space, undersea, nuclear labs)?

Which ones, if any, must be different for different applications?

Question 3 : Should evaluative procedures for new developments and experiments

be different from those for competitive procurement in already proven

application areas? How?

Question 4 : What institutional arrangements should be made to achieve equitable

evaluation and communication of results? Who should do the testing (producer, consumer, government, independent testing agency or consultant, other)?

4, to identify specific terms and performance measures which have been used

successfully or unsuccessfully, and why;

5, to prepare a report on the results of the workshop, including recommendations

for further action,

2.2 Program

The program is given in Appendix 2. The presentations were grouped according to application area; these are reviewed in Section 3, along with salient points of

discussion. Time was allowed for discussion in small groups, where participants were

evenly divided by application area and type of institution into three groups, X, Y, Z, to discuss the theme questions cited above and prepare written responses (Section 4)

.

The full papers are in Section 5.

2.3 Conclusions and Recommendations

The following conclusions and recommendations were drafted by the editor, as being

representative of consensus by workshop participants, and edited by the participants.

5
2.3.1 Need to agree on definitions of terms

There is a need for agreement across the robot/manipulator community on common definitions of terms. Too often terms such as "friction'^ stiction"^ hysteresis", 'backlash'^

"damping", 'stiffness", "strength'^ active'^ "passive", "load carrying capacity", "speed", "blockto-block time", "degrees of freedom'^; "naturalness", controllability", "reliability'j

"maintainability'! "programming ease'^ "specification", "standard'^ and "robot" are not understood

(by people reluctant to admit it) , or misunderstood (by people who understand a different

meaning). One or more efforts should be mounted to compile a glossary or thesaurus

while at the same time gaining agreement and acceptance of terms across the technical

community.

2.3.2 Need to establish common test codes

There is a need to establish commonly accepted test codes or procedures

according to which measures of elemental motions or mechanical, electrical or chemical

properties of manipulators or robots derive meaning and are understood by all parties

to mean the same thing. These test codes complement and extend the verbal definitions

called for in the previous paragraph, giving more precise definition to "backlash",

"positioning accuracy", "load carrying capacity", "deflection under load", etc. Common

test codes are particularly essential for dynamic perfiarmance specification.

2.3.3 Need for checklists and guidelines

There is a need to develop checklists (for thinking about) and guidelines

(for writing) specifications, to help individual users specify clearly what tasks they

need done, to help suppliers provide unambiguous exposition of what capabilities their

tools provide, and to help each ask the right questions of the other. It is up to the user to describe his specific jobs, work-place environments, acceptance tests, etc. but

his use of a more or less standard format (likely to be different for different

industries and areas of application) may be helpful to the supplier. It is up to the

supplier to describe his product by means of performance measurements, resume of

accomplishments, or whatever, but his use of a standardized guidelines and formats which

have potential for semi-standardization should be tested out with cooperation by user

and supplier groups.

2.3.4 Need for common demonstration tests

There is a need to develop certain kinds of tests for demonstration and

exhibition, primarily in research and development activities. These should be described

and compiled along with other similar tests already developed, such that these same

tests may be performed at the discretion of users and suppliers and the measures of

performance of the tests will have a commonly understood meaning. Examples of such

tests are drilling holes, inserting bolts, threading a needle, striking a match,

building a stack of blocks • Measures of performance can include task completion

time, classes of errors, etc.

2.3.5 Performance and design standards inappropriate for now

It is believed inappropriate and premature at this time, and even inhibiting

to research and development in the field, to generate specific pass-fail standards for

performance (speed, accuracy, etc.) on basic design features of robots, or manipulators

(kinematic configuration, power transmissions, control systems, workplace compatability

,

environmental vulnerability). Standards for certain attributes such as safety are of course being motivated by special federal regulatory agencies (though criteria for such

attributes may be included in checklists and guidelines).

6
2.3.6 Appropriate institutional roles

Appropriate roles for professional societies, trade organizations, universities

and government agencies are in:

a) educating the public and potential users as to the advantages and disadvantages in various applications of robots and disseminating information

about recent advances in the field

;

b) implementing 2.3.1., 2.3.2,, 2.3.3., and 2.3.4. above

i

c) considering other areas of standardization such as software for robots

and robot teaching procedures.

Actual performance testing should be left for now to the supplier and user, the

operating parties in the free marketplace.

7

3. REVIEW OF PRESENTATIONS AND DISCUSSIONS

J.M. Evans opened the Workshop on behalf of NBS , He asserted that the interest

of NBS was to help government procurement and the U.S. economy in general, and that NBS

does not wish to force premature standardization. However, quantitative specifications

of products can, in general, improve a competitive marketplace by allowing better

communication between buyer and seller. Voluntary standards, he claimed, are encouraged by economic pressures. In the discussion which followed it was questioned

whether or not it is acceptable to wait and evaluate manipulators "on-the-job". Many

believed it was. Some felt there are always lots of surprises when the real application

begins.

T.B. Sheridan gave an overview paper to introduce three kinds of ideas: the first

included some axioms about evaluation generally (that value functions are scalar, ultimately

subjective, that they may be non-ordinal, that they must be publically accepted and

understood, that completely "fair" social choice on standards is impossible, that perfect

simulation of the future is impossible, that the cost of evaluation must be considered).

He also discriminated between manipulator tasks and manipulator tools. Finally he

suggested a taxonomy scheme for evaluating robots and manipulators.

D.G. Jelatis , having many years of experience in developing master-slave manipulators,

suggested that over the years many manipulator systems failed to survive because they were not the "fittest" - were not rugged enough and were used for tasks for which they were not designed. He proclaimed the importance of "naturalness", and called for some better agreement on terms and measures for "obtrusiveness" , "friction", "elastic

deflection". There were questions raised as to whether in the development of masterslave manipulators specifying of standards was helpful. It was pointed out in response

that often government procurement specifications become standards. There was additional concern about specifying things which aren't needed, but one government

representative cited a case of not having a proper spec and being rewarded by $70K worth

of stripped gears. The concluding discussion called for standardization primarily of

terms and guidelines, where too much standardization of devices themselves may be

stultifying,

B. Roth then presented a systematic way of considering kinematic criteria. He

described how displacement of the free end is the most important variable, that coupling

of rotation and translation depends upon type of joints used, why the number of ways

a manipulator can reach a position is important. He went on to characterize solvability - the ability to find all possible joint angles for a given endpoint position. He said

it is difficult to design to a prespecified work envelope. Finally, he discussed approach

angles, and why the larger the range of approach angle the better. Discussion concluded

on the note that some things do not have to be rigidly specified.

J. Vertut presented his recent work on evaluating master-slave manipulators.

He showed how exact spatial correspondence between master and slave is not important

so long as force feedback or "feel" is good. The evaluation tasks he used included:

1) putting a peg in a hole or a block on a peg, etc; 2) making a wall from lead bricks;

using two arms to lift what you can't lift with one. He showed how different

manipulators (different control schemes) are characterized by significantly different

profiles of log completion times over the various tasks. He asserted that to some

extent certain specifications, such as compliance, must be relative to specific tasks.

J,F, Engleberger made the first presentation in the area of industrial applications.

He expressed skepticism about whether the field is ready for standards t.nd wb.ether

standards would not be too restrictive, that invention is the higher order activity. He

worried that man has been too much the standard, that the object is to replace man and

do better than he does. He also cited the importance of dynamics in evaluation (which some

9
of the earlier efforts to standardize tests have neglected) , In considering performance

descriptors he cited as important: space intrusion and the necessary modification of the

workplace; programming ease and time consumed in teaching; reliability and the interdependence of the robot with other parts of the process. He suggested that robots have

"resumes" of performance qualifications and achievements, much as human job applicants.

R.L. Paul liked the idea that performance of robots and manipulators be evaluated

relative to that of human workers, at least in order to understand what the numbers mean. He cited key differences in actuators, sensors, mass and strength-to-weight ratio. He

emphasized the functional distinction between hands and arms and differences between

compliance and control. Finally, he made some comments regarding evaluation of software

(core requirement, execution time, precomputation, automatic reprogramming, cleverness

at branching as a function of success). In response to a question about discovering

whether hardware or software is at fault, he suggested the best way is to get the

people together. There were further questions about the advisability of using the

human arm as a model; Paul asserted that our understanding of the function of the

human arm-hand complex is primitive and there's lots to learn.

A. Case said that when he talks to manufacturing engineers about industrial robot

application they are apt to ask three questions: 1) will it do the job?; 2) will it be

cost effective, considering that labor may be available but capital scarce, and

considering the whole system and not just the robot alone? ; 3) who will service and

support the robot in the factory? He went on to say that the manufacturing engineer

doesn't want to spend time doing kinematic and dynamic analysis, but needs help in

breaking assembly and other robot tasks down into their parametric elements.

P.M. Lynch spoke next. He outlined the Draper Laboratory approach to the

evaluation of programmable assembly systems for industrial applications. The important

criterion is the cost of assembly per unit of product as a function of execution time,

task failure and system cost. The assembly process can be further broken down into

subtasks and subcosts, all of which bear some allocation of the purchase price of the

system. By changing the assembly task sequences and/or system configuration of the robot

a different lower bound on task time results and a corresponding differential cost. There was discussion about the inappropriateness of a 2 year payoff of robot capitalization

because of the universality. The assertion was made that 8 years would make more sense.

A. Bejczy reviewed the various studies which he has conducted at JPL on requirements

for deep space applications. He cited the definite need for computer-programmed control,

but at the same time the need for man in the control loop as a supervisor, even in the case of long time delay. He spoke of the importance of local sensory feedback from the

wrist or hand (wrist force, touch contact, proximity) and the terminal device design.

Performance measures include "success" or "failure" for effectiveness of control, accuracy

and time for quantity of control, and consumption of resources for quality of control.

He concluded that more systematic work is needed on task description and analysis, that

a "slight" change in the task may be a trap. He also said that the quality of the

breadboard is important, and the hand sensor has a significant effect.

N.L. Shields described the test program and procedures currently being used to evaluate manipulator system concepts for teleoperators . A system can be viewed as an intersection along three orthogonal scales: human operator control, through fully

automated control; fixed purpose, through general purpose manipulator/tool; general^ through

specific tasks and task sites. A test program of ordered manipulator system tests can be utilized to evaluate a wide range of different types of manipulator systems, where the

test order involves going from control of a single degree-of- freedom^ through a hierarchy

of tests to the control of multi-degree-of-freedom task situations. By eliminating

specific candidate manipulator systems which fail to comply with system requirements

at the lower end of the hierarchy, considerable resource savings can be realized (by

eliminating tests on all possible combinations of manipulators and tasks).

(Editor's note: This is equivalent to coping with the "curse of dimensionality" in

optimization theory.)

10
A.B. Rechnitzer then reviewed applications of manipulators to undersea problems and

in association with test vehicles such as Alvin, Beaver, and the Deep Sea Rescue

Vehicle. He emphasized the specific engineering functions which are specified (cutting

of cables, attaching hooks). His colleague, G. Malacki, emphasized that in final end

item procurement the evaluation is essentially "will it do the job?", whereas in

research the performance testing can be more appropriately elaborated into parametric

studies and interactions.

A. Pesch also discussed undersea applications, including object recovery, salvage

(chain and hook applications, cable cutting), scientific operations (coring, collecting

samples) and commercial applications (inspection, cable laying, equipment repair). He

called for better definitions of design and system response variables and widely

applicable measurement schemes, using as illustrations definitions and tests he has

developed. He advocated task analysis as a means of developing performance measures which can discriminate between various manipulator designs on both a whole and parttask basis.

J.G, Grundmann opened the session on nuclear applications. He described the

necessity for fuel recycling plants in the 1980' s to supply fuel for nuclear reactors.

To operate and repair production equipment in large hot-cells of such fuel recycle

plants, a new generation of production manipulators must be developed (as contrasted

to earlier manipulators used for experimental work in small hot-cells). He emphasized

two types of manipulator specifications unique to nuclear applications:

1, All nuclear manipulators must have extremely high reliability because repairs

must be done remotely and this is much slower and expensive than direct (hands

on) maintenance

.

2, Materials utilized for nuclear manipulators must be specified to ensure proper

radiation tolerance, (This is necessary because some common materials

deteriorate when placed in a radioactive environment.)

W.R. Hamel concurred on the future importance of manipulators for nuclear fuel

recycle. He also described the complexity of the production equipment which the

manipulator would maintain and hence the desirability of an advanced computer aided

manipulator to handle intricate maintenance tasks quickly. A need for development work

was indicated, since a suitable computer-aided nuclear manipulator is not now

commercially available.

C. Wicker spoke next, emphasizing again the need for reliability in nuclear

operations and for ease of maintenance of the manipulators themselves - especially

difficult because of the inaccessibility and long time delays before they "cool". He

implored the designers to "keep 'em simple."

W. Verplank's presentation shifted the focus back to theoretical aspects of

performance measurements. He described the research of himself, D. McGovern and G. Starr

of Stanford, using the NASA Ames, manipulator arm under computer-augmented manual control.

His results systematically related task completion time of different manipulators to an information measure of required tolerance as well as a measure of distance travelled.

From these results he inferred standard time measures (like MTM) and methods of predicting

the effect of automating a portion of the task. Current research with Starr is comparing

rate with position control under time delay and/or with automated subroutines. There

was the suggestion that rate control may be preferable under these conditions. Verplank

also suggested the utility of predictor displays in time-delay teleoperator situations.

11
B. Sallot gave the next presentation. He described the efforts of the new Robot

Institute of America to define a robot and provide a medium for exchange of information

on how to use it. He commented that in spite of their high technology no strong

manufacturing base for robots now exists, and that applications-oriented educational

programs are in order. He concluded with the thought that rigid standards would be too

restrictive at this time, but that both standard definitions and evaluation guidelines

are certainly needed.

R. Hohn then gave a presentation, citing the prospects for broader application of

robots in industry, especially in new factories or in conjunction with new products.

He believed that "specification" should be a communication vehicle by which potential

users can assess whether a particular robot meets their needs. He reiterated the notion

that "specs" which become too detailed may hinder more than help. There followed some comments from the floor on the dangers of the robot community talking only to itself.

D. Morelock described the application of robots in a new automated munitions

manufacturing facility to be built, then put in "lay-away" for future potential use. He discussed the problems of justifying new equipment to management, and suggested that

within each category of robot application a list of benefits should be drawn up. He warned not to "tarnish the sophistication of robots, but don't make people think they'll

replace human thinking". He precipitated some discussion among the participants on social effects of robots. Some thought the idea of a "robot" makei people feel anxious.

There was a concern expressed about whether the robot could help in the very fundamental

problems of achieving more equitable income distribution. There was a reminder that

the robot creates wealth, which is the starting point (everyone wants to share in some- one else's wealth). There was a warning of the dangers of too much "bottom line

thinking" - and the need, for example, for people to find fulfilling jobs in any case.

The final individual presentation was given by J. Albus. He described NBS

research on robot loading and unloading of a machine tool, using trajectory calculation

and LED proximity sensors to control the robot's grasping phase. He also remarked about

the concern people expressed over the term "standard", that invention should not be impeded

thereby. His belief was that invention is problem solving, which includes selecting and

defining the problem, and that a "problem well defined is a problem half solved". He

felt that properly selected, a set of standard tests can be enhancing and not impeding,

to channel and order the efforts of the designer. And he reiterated the need for better

definition of terms.

The discussion closed with agreement that we should not standardize too many things - for example a kinematic configuration, while it would be helpful to standardize on ways

to talk about kinematics. It was also agreed that we should work toward common formats

for specifications, common guidelines, and tests, and common language for programming

robots. But we are not yet ready to write them down; there is much work yet to be done.

Then the three small task groups, X, Y, and Z, gave their reports, primarily

in response to the four theme questions cited above. Their responses are presented in

Section 4.

12
4. QUOTED RESPONSES OF OROTTPS AND INDIVIDUALS TO THEME QUESTIONS

4 . 1 Question 1

How can the specification of performance of relatively general purpose robots and

manipulators be improved (so that the supplier can specify his product's capabilities

and the user can specify his task requirements and each can be held accountable )

?

4.1.1-

First, there was definite agreement on the need to clarify and standardize . terminology:

• An accepted set of definitions of different terms or measures is probably the most

important immediate goal we could undertake (e.g. backlash, function, load capacity, tip

orientation, accuracy, statistical variation, etc.). A dictionary or thesaurus is

needed (Group X) . '

• Technical terms should be standardized, e.g. with respect to geometry and coordinate ' system, control techniques (the Japanese Industrial Robot Society has begun this effort).

(Group Y)

• There is need to achieve general acceptance of definitions, e.g. of "compliance','

"accommodation", "accuracy", "repeatability", "resolution", "backlash", "hysteresis",

"lost motion", "stiction", "breakaway", "reversal torque", "ruggedness" , "maintainability".

Maybe the terminology standards exist and these only need to be applied to robotics.

Perhaps the robot field needs a standards committee (Group Z)

.

• A common language must be established including a glossary of terms (e.g. accuracy,

repeatability, resolution, point-to-point control, continuous path control, etc.) before

we can have any specifications on performance. This is not necessarily a difficult

task since many of the terms are defined in the literature. What is required is to extract this information and modify it to be applicable to manipulators/robots, (anonymous)

» Improve the uniformity or standardization of definition of terms - perhaps a standard

glossary of terms could be compiled, (anon.)

• The vendors must standardize terminology pertaining to their systems . Terms such

as accuracy, geometry, load capacity, etc. must be common to the robot manufacturing

industry. All users with similar manufacturing processes must standardize user terminology

for their type of application. Cross communication of vendors and users is obviously

appropriate during the standardization efforts above. (Grundmann)

• Consider the development of standard terms. Define the vocabulary. Limited

examples exist in several areas such as: the NASA Corliss and Johnsen books; JRI

;

Numerical control society; IEEE; Bertsche/Pesch reports on force feedback variable

definitions. Needed is a standard method of describing the work envelopes of systems in

regard to: range, ability to square up to various task surfaces, degrees of freedom

remaining at points in the work envelope, standard kinematics, e.g. Roth's or some coordinate system. (Pesch)

I feel that the greatest contribution that could be made in this area is the

definition of terms. While I don't think we are talking apples and oranges, we are definitely talking oranges and tangerines. For instance, should "degrees of freedom"

13
reflect three rotations and three translations (a total of six max), the number of joints

in the arm (I've seen arms with nine joints), or the arm motions plus mobility

capabilities? Speed specifications should be specified at some known percentage of rated

load (and arm extension for rotations) . Accelerations/decelerations with a known load

should also be specified so that block times can be estimated. Torque capacities at the

joints should be specified as well as load capabilities. Position accuracies and

repeatability should be specified as a function of load, speed, arm extension and

deceleration. Drift due to changes in the ambient should also be specified if significant.

I'm sure I could fill up another two pages but I think you get my point; each manufacturer

interprets and publishes data to optimize the unit he is selling. (Hanify)

4.1.2-

The discussants reminded us that basic problems of definition of robot and

teleoperator persist and must be dealt with:

• Group X felt that the differences between robots and teleoperators are potentially

larger and more significant than the differences between applications of general purpose

robots or teleoperators.

• Group Z pointed out that there will remain those who will claim, with regard to defining robots, "I don't need to define one, I know it when I see it."

• J. Vertut feels that this difference is small in that teaching a robot is similar

to operating a teleoperator.

4.1.3-

Sorae of the comments were to distinguish the different but complimentary

roles which should be played by the user and the supplier in specifying, respectively,

the task and alternative tools for achieving the task.

• The user is to supply function and task requirements and define^ as explicitly as possible, the capabilities needed, including the ranges, task parameters and tolerances

and the environmental conditions in the work area. (This highlights the need for good

job-task analysis early in a program.) The supplier should be encouraged to offer

alternative technical approaches for accomplishing the functions or tasks, including

equipment design options and procedures. It is then the user's job to evaluate the merits

of alternative approaches and to make a decision on the basis of performance versus cost. The users should not specify how the system should be designed - that is the responsibility

of the producer. It is important not to constrain the producer, but to allow for

creativity and inventik/eness , (Group Y)

• Group Z suggested drawing which looked like this:

cu z

0 2<

-< stippLiee,

L U.

• It is necessary to separate tool and task (to the extent man is in the loop for

control or programming) c ontrol specifications; all are orthogonal. We need better experiments

experimental data from labs on all 3. We also need better task analysis from users i and tests and demonstrations of the same tasks by different manufacturers. The j "resume concept" (see below) is very good, (anon.)

14
• There should be separate specification of TASK and TOOL. For example, the materials

and dimensions are TOOL specifications; reach and strength are TASK specifications.

This will encourage flexibility of TOOL specification (leave room for invention). The

problem of specifying "general purpose" remains; the only solution seems to be to specify

a r ange of representative TASKS. (Verplank)

4.1.4.

There were a number of expressions on the desirability of some standardized

format or "guideline" or checklist to be employed by user or supplier or both:

• (Devise a) checklist set of guidelines of important characteristics to be defined

in the specification. These should be in hierarchical arrangement, in order from most

general to most specific, e.g. task environment, load capability, operating volumes,

mechanical impedance, or transfer function. The guidelines would reinforce the

commonality of technical language, and the basis for user-generated "job descriptions"

or "task specifications" and supplier-generated "robot resumes". As part of the format

for conveying information perhaps there should be a standard kinematic drawing to specify ' ~ the shape of the manipulator. (Group Z)

• A format guideline for manipulator/robot specifications would be a valuable tool,

(anon.)

• A large checklist or questionnaire could be developed. This could be structured so that suppliers would have to reveal what their manipulators cannot do (as well as what

they can do), and users can focus on the trade-offs between different systems. If this

list were broad enough a typical sheet would have many "null" entries (e,g, "does not

apply", "do not know"), and this would be a way of giving both supplier and user information that is usually missing, or not asked for until it is too late. Also, this

would be a way for "experts" (i.e. people with a little experience) to help each other,

as well as new users and suppliers, focus on what actually needs to be specified. In addition, this should include a resume of the type distributed by J, Engleberger.

Especially important is the section on task performance. The user should be told exactly

what type of tasks the manipulator has performed; and the user should be force d to specify exactly what type of tasks are minimum requirements, (Roth)

• Improved specifications of Performance - a series of guidelines/manuals should be

developed to aid the communication between users and suppliers. These manuals would be

used by potential users of these systems to determine and define the scope their tasks

and document their functional requirements (tasks) using standardized terms and formats

to provide efficient technical communication of those tasks to suppliers in procurement

specifications. Upon receipt of proposals from suppliers, the user can then evaluate,

using standardized data and procedures, the various proposals received and determine

the best unit/system for his job.

standardized definition of terms for robots/manipulators

standardized manipulator/robot classifications (families by characteristics)

performance tradeoff characteristics

guidelines for determining applications for robots/manipulators

guidelines for writing procurement specifications (user)

- guidelines for writing equipment specifications (supplier)

15
standardized format for procurement specification

standardized format for equipment specifications

4.1.5,

One way suggested for dealing with this question was to look at specific examples

of specifications and try to improve them^ for example as suggested by Wicker:

• Consider the procurement specifications used by ORNL for master-slave manipulator

standard duty specification XSP-239 (reprinted in Appendix 3) and Electro-mechanical

manipulator specification 10017-N-lll-X.

4.1.6.

Many of the responses to this question were directed toward suggesting

particular tasks or tests for evaluating manipulators or robots (note that these also

begin to answer the next question, No. 2)

:

• Perhaps evaluation tasks should be graded with respect to dexterity, speed, load

capacity, sensory communication. Perhaps there should be a standard set of exhibition

stunts: writing, applying lipstick, threading a needle, striking a match, laying bricks.

Perhaps one kind of task should be a survival test, (anon.)

• The specification of manipulators should be in terms of primary functions, i.e.

link specifications (motion limits, strength, acceleration, type of actuator, servos, input and output, backlash, friction and inertia) such that suitability for a specific

task can be evaluated, A resume of tasks that have been accomplished should be provided.

In terms of software, each module should be defined as to its capability, the language

used and the appropriate computer in order to evaluate its suitability for incorporation

into other operating systems and programs. Software should be as modular as possible,

(Paul)

• Devise standard tests, which need not be comprehensive, but might include measures

of backlash, stiffness, friction, pick-and-place speed, simple assembly, complex

assembly. These might also include tradeoffs of torque vs, speed, etc. (Albus)

• First limit tasks to those that have been demonstrated to be performable. Tasks

that have not been demonstrated imply new development. Then list the specifications

that measure the performance of general purpose robots in this range of tasks. It would

be nice to develop a set of evaluation tasks the performing of which could be extrapolated

to real-world jobs. Conceivably the user could merely describ.i the job to be done and

the vendor describe (and prove) capability for doing it, i.e. "robot resume". Weighting

of performance specifications might be useful. (Block to block speed is more important

than machine weight.)

Typical Task-Performance

performance

speed (block to block)

accuracy

manipulative power

space intrusion

reliability

memory capacity

programming case cost

task

die casting

welding

paint spraying

pass

palletizing

plastic molding

16
Note that the specification of performance becomes easier if the product class is limited

to "general purpose robots". If all simple "pick and place" arms are included then all

automation is being examined. As robot sophistication advances, the resume becomes more

and more legitimate as a selection tool. The validity of the resume is tested by

references and by the battery of generic skill measuring tests that users slowly evolve.

(Engelberger)

• There should be developed a series of mutually acceptable and representative tasks

to be completed under strictly controlled conditions, the results of which are specified

in mutually acceptable terms. If we agree that "temperature" is desired measure then we need to specify on which of the available scales we are going to record temperature

and we have to specify the measurement instruments - mercurial, alcohol or electrical.

Methods and apparatus room need to be standardized also, (anon.)

• Instead of specifying only torque, resolution, and other parameters specific to a particular manipulator design, also specify manipulator/robot performance on a set of

standard tasks. This is not to replace basic hardware specs but is to be in addition to them. This gives the user the chance to concentrate on the problem of task definition

for his process and the designer the freedom to design something to accomplish the

specified tasks. The designer can explore what physical properties the manipulator/robot

must have to accomplish the tasks. In the case of programmable assembly, there could

be a set of standard tasks which could be used to infer the performance of an assembler

robot for a range of assembly specifications. For example, if execution time averages

for the following tasks - gross motion (stop to stop), fine motion, grasp and release - were available, then the potential user might be able to form some estimate (albeit

rough) of the assembly time for his product. Refining theestimate further would require

a more detailed study. Such data on standard tasks should be treated in a way similar

to the treatment of EPA highway and city driving mileage figures - roagh estimat;es of

what can be expected in different situations, and a way to compare robot performance.

In any event, such performance figures would be most useful in the preliminary

evaluations. (Lynch)

• As far as the measuring performance of robots and manipulators, I think the factors

which always appear to be missing in any activity which I engage in concerning industrial

robots is a definition of over-shoot and general positional performance. Most robotic

devices depend on the system discrimination and there is not a great deal of attempt

made to measure the actual performance^ either the transient dynamic performance or any

precise and reliable estimate of the final position or accuracy. 5uch factors as drift seem to be taken for granted. All these factors are very important in specifying

the performance of a first generation industrial robot which is dependent on its precision

and accuracy for its final functioning. The performance and relative performance of various

types of actuation does not appear to be too well known^ and also what is the limit to the axis speed which one can attain with different types of actuation, i.e., electrical,

hydraulic, pneumatic, etc. (Heginbotham)

Editor's Note: Professor W.B. Heginbotham of the University of Nottingham did not

attend the Workshop but submitted this response to our theme question by letter.

17
4.2 Question 2

What terms, tests and indices used for performance measurement and evaluation can be common across the variovs types of devices and fields of application (e.g. manufacturing,

mining, space, undersea, nuclear labs)? Which ones, if any, must be different for

different applications ?

4.2.1.

There were many suggestions for tests which can be generic, or common across applications. There was also some agreement on what these should be:

• In defining a "tool", the following generic measures were listed:

1) speed (block-to-block time)

2) accuracy

3) kinematics

4) space intrusion

5) reliability

6) number of program steps

7) programming ease

These measures were proposed for robots, but are generally applicable to teleoperators

as well, particularly if a computer is assisting man in the control loop.

Task specifications are needed for non-proven applications, for example, coping

with misplaced or misaligned objects. A battery of aptitude tests might be developed.

A test for human aptitude for assembly work of picking up and moving an object with

tweezers was given as a simple example. There are existing tests, such as water pump

assembly or pin-in-a-hole tests, but they have not been generally applied. There was one member of the group that disagreed with this. The tweezer test was cited as a test of the

hand, not a task aptitude test. Also, this member felt that more attention should be

paid to tool design, such as link strength, length, design, backload, etc. for various

application areas. (Group X)

• Standardized performance measurement and evaluation can be done in the areas of

reliability (MTBF) , availability, and maintainability:

Specify engineering integrity of the manipulator for the size and weight of the

load to be handled throughout all of the motions of the task, i.e. require sufficient

overdesign of stress points.

Test the load capacity for all orientations, power requirements of the arm and

its actuators, workspace envelope, orientation of end effector within workspace,

reproducibility in returning to the same point in space, accuracy, and performance

correlates (what does it take to obtain that performance level in terms of cost in

money, ease of maintenance, man fatigue, etc.). (Group Y)

• We recommend three different kinds of tests:

a) acceptance tests for individual systems

b) general tests to compare systems, including positioning accuracy and

time to move between points

c) supplier demos to show individual excellence of a product. (Group Z)

18
• I believe certain measures and tests are application invariant. The weight attached

to each measure will vary fran field to field and even between applications in the same

field. My list of important tests, terms, and indices include:

1. degrees of freedom of positioning end

2. zones of operation of end effector

3. zones of operation of each link

4. load capacities (static and dynamic)

5. accuracy, backlash, deflection under load

6. control data under specific standardized test conditions

7. reliability

8. type of joints (Roth)

• Tests and indices which appear to be common to all devices are:

a. diagnostic techniques

b. reliability methods >

c. load test (capacity)

d. cycle time (speed) test

e. working envelope

f. accuracy (Grundmann)

• Manipulators/robots perform tasks in any domain - space, undersea, industry,

and hot lab - even though the manipulator/robot mechanisms and scale may be quite

different. Therefore, performance tests based on tasks are potentially applicable

across various types of devices and fields of application. To the extent that tasks

are similar in different fields of application, common task based performance measures

might be used, as possible. (Lynch)

• At least in the case of a robot, its primary function is positioning. Tests related

to this function should be used for performance measurement. These tests could include

accuracy, repeatability, stiffness, etc. What must be developed is a test code which would

describe the measurement means, machine setup, and measuring techniques to establish

these performance specifications. Also, testing for time to move between programmed

points is important. A simple statement of maximum velocity is not useful in

determining the time to move between points, (anon.)

• We should establish a set of standard test formats to measure the various aspects

of remote system performance. This refers to standard means of measuring rise time, force

fidelity, position accuracy, dead band, force to move, speed of movement, positioned

accuracy/repeatability, etc. We have developed some tests for force feedback. These

may be used as an indication of what may be generally useful. Examples of some tests

currently being applied to define force feedback are in a recent ONR supervised report

by Bertsche and Pesch. Also, consider developing a few standard tasks made up of basic

movement elements, as found in time and motion studies, to serve as "bench mark"

performance tests. There are many pitfalls to this approach since it could drive

design to better perform the standard tasks rather than increase the flexibility of robot

or manipulators in general. However, on the positive side, some of the evidence presented

at the conference (e.g. Verplank's data) suggests that basic time and motion task

analysis seems to hold across a variety of hardware and task applications. (Pesch)

19
• Our experience in undersea testing has been that most tasks can be divided into a surprisingly small number of elements or groups. The two tables in my paper show a rather high level grouping of elements which accounted for 95% of the behavior found in

the eight applied tasks. Similar work in process, evaluating the effectiveness of the

Navy's Work System Package, is using this technique to advantage. The prime advantage

as I see it is the specification of standard tasks for "bench mark" evaluation of

various systems. A great deal .of care must be exercised over the development of the tasks.

Task analysis of real manufacturing tasks, military tasks, hot labs, etc. should be

followed by the. creation of a sample data pool of basic task elements. These require

validation and an estimate of variance prior to issue or use in assembly of new tasks.

An advantage is some standardization of basic movement categories of robots and a task

reference for time and accuracy measures. (Pesch)

• My paper makes some relevant points regarding "zoning classification". (Vertut)

4.2.2

Not all tests can be common across applications. For various reasons some must be different :

• Some tests will be different in as much as they relate to the peculiarities of the

environmental conditions of the different fields of application, as well as the utilities

(values) associated with the several criteria that pertain to the system functions.

(Group Y) ,

• Indices which are not common to all devices. Three obvious bases for differences

are:

a) classification of devices as robots or manipulators

b) robot material specifications for unusual applications

c) interlock and interface equipment

(Grundmann)

• To the extent that an . application field has a problem non-existent in an other

field, tests relating to this problem will be unique to that field. (Lynch)

• Different fields of application normally apply constraints on types of mechanisms

used, i.e. no hydraulics for nuclear applications. These should be summarized for

each field of application. In turn then manipulator specifications could state for

which field of application the manipulator was suitable. (Paul)

• In one sense all, and in another sense no terms, tests and indices should be common. Certainly, definition of terms should be common across all fields of application.

However, some specs which are critical for some applications will be irrelevant to others. Certainly standard tests are by definition task-specific. Each field should

devise its own relevant set of performance tests and each manufacturer expecting to sell

manipulators for that application should demonstrate the performance of his product

under those tests. (Albus)

4.2.3.

There were other comments made in response to this question to emphasize

(i) the need to consider dynamics, (ii) the need to keep tasks and tools separated, and

(iii) the need to organize terms, tests and measures on a scale from general to specific.

• Current robot manipulator specifications tend to be static. Lumped parameter

static specifications are satisfactory for master/slave manipulators because of the slow

speed of operation but robot and some remote control operations demand rapid response

and thus depend upon dynamic performance criteria. Simple slew rates and maximum loads

20
are not adequate dynamic specifications (e.g. Engelberger) , but acceleration and

deceleration factors possibly combined with slew rate and block-to-block time and inertia

and torque factors are needed even for simple transfer applications of robots. We need

some sample tasks to agree on (e.g. Pesch vs. Vertut vs. MIT) to be able to compare

dynamic task data, e.g. transfer, simple assembly vs. complex assembly. Interactions

must be considered (e.g. Vertut's data on hands, degree of force feedback). (anon.)

• Again, performance should (as much as possible) be measured in terms of TASK.

That is, which tasks are to be (or can be) accomplished and what are the relevant

measures which describe the task and performance on the task. For example, TASK: loads,

dimensions, tolerances, variabilities; PERFORMANCE: time, energy, cost (Verplank)

• One should define from the common to the unique rather than emphasize differences.

They each have to be so developed to exclude "area specific forms" even if what we are

forced into doing is developing a thesaurus which lumps closely associated terms. If

you start out proving (manipulators) have to be different you buy problems you don't

need. If things are truly different and unique, they should be the leftovers and the "not elsewhere classifiable". (anon.)

4 . 3 Question 3

Should evaluative procedures for new developments and experiments be different from

those for competitive procurement in already proven application areas? How?

4.3.1.

Some respondents said yes, feeling quite different criteria should apply to new developments vs. proven applications:

• Our group felt that it was important to distinguish between new development and

proven applications. In the context of proven applications it is up to the user to specify the task and up to the supplier to prove that his tool can perform that task. In this context, the "resume" concept was generally agreed to be a very useful concept.

This could be a checklist of capabilities or a list of questions to answer or a list of

successful proven applications and possibly appropriate references.

It was generally agreed that for proven applications tight tool specifications

were useful (leaving open cost, service, delivery, etc.) but that for development work

task specifications should dominate, leaving avenues for invention open to the tool

developer. (Group X)

• Yes, ordinarily, there are differences in evaluation procedures as a consequence

of the distinctly different goals and technical approaches. The test and evaluation

of systems that embody proven technologies can rely upon established engineering

practices and measurement techniques together with quality control methods employed in

manufacturing processes. The guidelines for these procedures would be expected to be

contained in the work statement for the competitive procurement. R&D programs,

on the other hand, employ a different set of tools and techniques, particularly those

concerned with the advancement of theory and/or the extension of a technological base.

Work in this arena tends to be characterized by the formulation of concepts, hypotheses

and models, development of experimental designs and conduct of experiments, the derivation

of lawful relationships between variables under study, and, in some cases, the development

of prototype hardware (or software) . The products of R & D are generally evaluated on

the basis of scientific and technological merit (new knowledge, understanding of phenomena

and relationships, new technologies). Of course, in the progression from fundamental

research to applications the methods of science and engineering will merge and overlap.

(Group Y)

21
• Research projects always seem to have different requirements and objectives than

commercial systems and equipment. Hence, there is no reason to expect any similarity in

evaluation procedures. (Ljmch)

• For new developments evaluation should foster ingenuity. For proven areas specifications can be tight, leaving cost, delivery, service, etc, as variables. In frontier work, the cleverness of proposals, reputation of investigators, background

knowledge should outweigh cost in evaluation. (Engelberger)

• Yes. In development work, task specifications are primary. In proven applications,

tool and control specs are probably more appropriate. In the latter case, a demonstration of the tool for a specific task will often be needed. (anon.)

• Yes. Prior to the establishment of an experience data base sufficiently large to be suitable statistical tool, other methods must be employed to assure the user he is

going to realize his stated functional requirements. (Morelock)

• For well-developed robot applications, the evaluation of the device can be made

by demonstration in an actual manufacturing environment. For new developmental

equipment the specification of equipment design must be in terms of task need; and

design must be proven by final task performance. The user must be intimately involved

in design work, and must communicate with the vendor in terms of detail design parameters.

Cooperative preliminary design work is necessary to reach consensus on whether the

development is worth the risk. (Grundmann)

• Now we are talking apples and oranges. New development areas will nearly always

require a different set of evaluation criteria. First time user guidelines, if

established, should therefore be kept general enough to allow for variation in the

specific requirements of a particular application, even within the same area of use (i.e.

die casting or spot welding, etc.). (Hanify)

• New developments need not meet application constraints if evidence exists to suggest that simple proven changes will enable the manipulator to meet applications area

needs. (Paul)

• Yes and no. Wherever possible, it would be good to use common tests, but new

developments may make some tests obsolete. (Albus)

4.3.2.

Other respondents said "no" to this question or qualified their answers by discussing how new developments shade into proven applications.

• No. (Wicker)

• I don't believe they should. Hopefully the list developed for item 1 would be

broad enough to cover all such conditions. Certainly users would require their own evaluative procedures in any event. (Roth)

• My basic reaction is to consider extending whatever methodology we currently

have to new applications as they appear. Perhaps some basic research should be

extended into the area of measuring "smart" robots" which will be alogical future

development. I'd rather see the funds expended on the technology vs. measurement. The converse is somewhat a case of putting the "cart before the horse". (Pesch)

• Eventually new developments must come under the same scrutiny as off-the-shelf

items or tried-and-true items in order to make decisions on comparable data. One

difficulty which may occur is in deciding the time when new developments become

of age and will be considered and evaluated by the proven item set of criteria, (anon.)

22
• There is a continuum of tasks from research to application to specification to procurement acceptance tests. This is probably the order in which they will develop

(i.e. the capability is first demonstrated by researcher and finally prescribed by

user). This seems a natural evolution (noting that the researcher/designer will also

be looking to the user for candidate tasks) . As tasks accomplished are used to illustrate the particular capabilities of various designs, they become the appropriate

description of that tool, i.e. appropriate to the user for specification;

Suggested Continuum of Tasks for Performance Evaluation of Robots/Manipulators

(Task specification should be independent of manipulator or robot type/design.

Task performance is the prooer evaluation of the design.

Example: TASK: move object held in end effector to all possible positions and

orientations

.

PERFORMANCE: those positions and orientations depicted in appropriate

(standard?) form, e.g. maps of positions reached and solid

angle of orientations at each point (figure of merit, a la Kobrinski)

(RESEARCH) DEMONSTRATION TASKS (a la Paul, Engelberger ' s RESUME)

-assemble water pump, turn crank, solve "Instant Insanity"...

COMPLEX TASKS (a la Vertut, Mullen, Pesch, Ferrell)

-pick and place, stack, follow straight line, etc. (used in comparing

competitive TOOLS)

ELEMENTAL MOTIONS (a la Engleberger, Lynch, McGovern, Pesch)

-reach, position, grasp, etc. (used in predicting performance on more

complex tasks)

MECHANICAL CHARACTERISTICS (see example above)

-speed, accuracy, work envelope, backlash (these should all be stated in terms

of specific tasks, i.e. standard tests, and NBS could create such a set of

standard tasks. (Verplank)

4.4 Question 4

What institutional arrangements should be made to achieve equitable evaluation and

communication of results? ^Jho should do the testing (producer, consumer, government , independent testing agency or consultant, other) ?

4.4.1.

Most respondents felt that the free marketplace had perhaps the most

important institutional arrangement to effect the desired result, but that the

government and professional societies had special roles to play which could certainly

help

:

• The implementation of testing of manipulators should primarily be governed by

the forces in the free marketplace. The definitions and test methods may be developed

by universities, government agencies, or other third parties, but implementation (of

these tests) is between the user and the supplier in the marketplace. (Group X)

• Much of the evaluation will be user-task dependent and will require a joint

responsibility of supplier and user in evaluating the ability of the machine to accomplish

the particular user-related tasks. There is a role for government or an independent

agency to supply some standardization of the terminology and a set of guidelines, or

a checklist, so that a prospective user will ha'^e knowledge, safety factors and other

23
important variables involved. User can either ignore or specify them in some detail

according to how important they are in relationship to accomplishing his particular

set of tasks. (Group Y)

• Society of Manufacturing Engineers, Robot Institute of America, Committees within

professional societies, perhaps with NBS (or other government) funding. (Group Z)

• The most suitable professional societies should become aware of the needs discussed

here and be provided a suitable incentive to do something about the initial groundwork

and guidelines which are needed. Upon a sufficient development of these guidelines, more formal adoption of them may or may not be desirable and efficient and probably

should not be decided at the present time, (Morlock)

• Probably the supplier and user should both do the testing, although some independent

source, such as NBS, industry association, or even ASME-type organization could create a uniformly-accepted set of definitions that participants could agree on and use for legal

precision in contract writing. This could even include some standard task definitions,

such as the EPA mileage tests, (Lynch)

• A group such as the workshop participants and the NBS could develop a list of the

type referred to in item 1, It would also be worthwhile to develop some standard test

tasks. These then could be used by manufacturers as well as users to rate their own machines. Government agencies may be most useful where the interests of third parties

are at stake, and where diverse groups of users must be considered. (Roth)

• It's too early to establish standards. Terminology and guidelines could be

established by the government for government use but I would strongly recommend the

involvement of non-government groups interested in the area such as the Robot

Institute of America and the Robot Subdivision of the Society of Manufacturing Engineers,

both of which are strongly supported by industries and other agencies (IITRI included).

Specific work tasks too big to handle by committee would have to be funded by someone

(NBS?) to gather data, formulate strategies and recommend alternate courses of action

(Hanify)

4.4.2.

A few individuals were skeptical that government or special agencies could

accomplish much of anything by way of standardized testing:

• I see no need for institutional arrangements that do not arise naturally. It is fine

if a testing agency can justify itself to industrial client. Fine, if a government

agency can provide a respected service to client agencies; for example, NBS under the

Brooks Act serves the government through the output of this workshop. Producers are already motivated to provide test data in order to sell their products. Users who

perceive a possible b enefit from using robots are disposed to evaluation testing.

Unfortunately, they are not motivated to disseminate results. (Engleberger)

• Not only is performance difficult to discuss but the government or independent testing agency would make this process even more remote, (Anon,)

• I believe the marketplace will basically determine this issue. For proven

applications, the producer will give the data; for development, the consumer will carry

out acceptance testing. (anon.)

• Apart from a need to define terms used in manipulator specification (backlash,

friction, etc) current institutional arrangements are fine. (Paul)

24
• This is really up to the consumer at this stage until the field studies indicate

that the consumer requires protection. (Pesch)

' My immediate and personal view, being a consultant on such programs, is that you

just let me keep on truckin' , (anon.)

• This question is answered in question 1 - in the attached specifications used

by ORNL for purchase of remote handling equipment. (Wicker)

4.5 Other Issues

There were a few additional written comments not in response to the above four

questions. Two other issues were raised:

• 1. Safety. This may be a valid problem that would generate third party

instrusion in the marketplace by government or labor unions. Possibly some group

such as this workshop should consider developing safety criteria before they are formulated and implemented by non-technically competent parties. (anon.)

• 2. Desired improvements in robot or teleoperator capabilities. A list of

realistic engineering advances could be formulated by such a group as this to spur

and guide future development efforts. (Group X)

• While not on the agenda, one could suggest that it is a higher order activity

to invent than it is to specify or evaluate. The workshop participants could have

taken on the assignment of cataloguing inventions needed - such catalog disciplined

by an understanding of the state of impinging technology. (Cybernetics article, by

way of example, will be submitted.) (Engelberger)

*

25

5.1.1

evaluation of tools and tasks: reflections on the problem of specifying

robot/manipulator performance

Thomas B. Sheridan

Massachusetts Institute of Technology

Cambridge, MA 02139

This paper examines some basic questions of evaluation of programmable general

purpose machines performing complex tasks. It begins with some assertions about

evaluating anything. It continues with some views on why evaluating manually operated

manipulators and programmable general purpose robotic machines is particularly

difficult, mostly because of a confusion over the differences between "tasks" and

"tools". It goes on to suggest ways of breaking this performance evaluation problem

down, and dealing with it both in pieces and together.

I. What is Evaluation?

Evaluation is assigning value, i.e. degree of goodness (badness) to things or events. It is appropriate to ask what specifically is assumed vrtien we talk about

evaluation. Below are some axioms I proffer in this regard.

(1) Scalar "objective function"

Value is a scalar function of all relevant variables within the system being

valued. For example, one can assign value to either manipulator speed or accuracy

independently, and quit here. But if speed and accuracy are to be valued in the same

terms, one necessarily must have a single dependent value function of the two variablesSuch an objective function then yields sets of indifference curves or compromise

functions. On a plot of two independent variables (e.g. speed vs. accuracy) these are

lines of constant value. For three independent variables a constant value magnitude

is a surface. I used to know a colonel who insisted that he wanted the maximum

performance at the minimum cost. If I hadn't been a lieutenant at the time, I would

have told him he was talking nonsense. We hear it all the time, however: "the greatest

good for the greatest number", etc.

(2) Subjectivity of value assessment

Ultimately, the assignment of goodness or badness is the subjective judgement of

a person. There can be an algorithm or an objective function, and in back of that

another objective procedure, and so on, but ultimately it all must be predicated on a subjective order of preferences, or an internal or ratio scale of goodnesses. Number

of products, man-hours, dollars, etc. must ultimately be transformed to a subjectively

produced utility scale which has no physical dimensions. That is, "objective function"

is subjective.

(3) Ordinality or non-ordinal ity of transformation

An objective function, a transformation from a physical dimension to a utility

dimension, can be ordinal or non-ordinal. For example, more manipulator accuracy

and more strength can always be better, all other things being equal; this is an ordinal transformation. But larger size can be better up to a point, then progressively

worse beyond that point. The latter non-ordinal transformation is called a "folded-scale"by

psycho-physicist Clyde Coombs. It makes analyses more difficult.

27
(4) Operational ity of choice process to permit comparison

The evaluation of music, sex and some other things may be private affairs,

judgements of individuals which are of no business to other persons (beauty is in the

eye of the beholder, etc*). But when an evaluation is the proper business of a community

of people, and wrtiere it is desirable to have common agreement (social choice) on the

relative worth of certain things and events, the procedure and/or reasons leading up

to one person's subjective judgement should be as operational as possible. That is,

there should be some basis for explaining how one arrived at his judgement which is

open and understandable to other persons in the correnunity so that they can have discourse,

test their assumptions against one another, and perhaps come to a consensus.

(5) Impossibility of social choice which is both equitable and reliably transitive

Let three machines - A, B, and C - be preference ordered by three judges.

Judge 1 orders them A, B, C. Judge 2 orders them B, C, A. Judge 3 orders them C, A, B. Applying majority rule, the social choice is A > B, B > C, and C > A, which is

inconsistent (intransitive). This is but one example of the probl«n characterized

by Arrow's impossibility theorem, iwhich formally proves that given some reasonable

assumptions of fairness in judging preference order, there is no procedure which yields

a fair social choice without intransitivity some of the time. If one considers worth

assessment on a continuous (cardinal utility) scale, there are other theories about the

impossibility of insuring that one person's scale is commensurate with another person's

scale. Thus, given that in a democracy we feel obliged to come to some social choices,

there are times when either we allow partial intransitivity or disagreement, or we allow

arbitrary means to be employed to resolve intransitivity or disagreement*

(6) Imperfect simulation of a future context

Usually the purpose of making an evaluation of past (present) performance is to

predict performance in the future* However, the circumstances of the future are likely

to be different from those under which the evaluative data were measured* This is

especially true if what is being evaluated has not yet been put in its "real working

environment"* In this case it is typical that the eventual "real working environment"

is simulated* But simulator tests are usually deficient both because it is too

expensive or impossible to include all the relevant variables in the simulation and

because some of the most significant future conditions cannot be anticipated* Thus,

when a design for a machine is optimized based upon performance in a simulator, it is

often suboptlmal relative to its performance in the "real world"* For this reason

factors of safety and benefit/cost discount factors have become common practice in the

interpretation of evaluations of prototypes in laboratory tests.

(7) Economic compromises in doing evaluation

Evaluation, like all other activity, has its cost. So there is always the question

of how much effort should be expended to make an evaluation, at what point the marginal

benefit is less than the marginal cost. There is a way of deducing the relative benefit

of evaluation activity itself if one can specify approximately! the costs of making

different kinds of performance tests C. in sifflulated conditions; the probabilities of

p(Rj^|R.) of getting different results Rj^, given the eventual on-the-job performance R.; the costs of various actions which one might take C. ^ the probabilities of different ^ levels of performance on the job p(R.); and the eventual benefits or payoffs of having

certain performance under various conaitlons of deployment, V. .. Figure 1 illustrates

the decision tree for manipulator evaluation in a simple case of deciding whether to

do no test and evaluation before deployment action, do a simple performance test, or do

a more complex performance test* For simplicity of illustration, there are only two

test outcomes, two alternatives for action which depend upon test outcomes, and two

levels of eventual performance in the real world* The calculation of the information

value preposteriori (i*e. what is the test worth before I know the test results) is

28
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Figure 1. Calculating the expected benefit of alternative tests or no test at all

29
given in the figure. This "evaluation of the evaluation" gives a rational basis for

deciding »rtiich test to make, if any.

II. Special Problems of Evaluating Programmable Robots and Telemanipulators

The ultimate evaluation of a robot or manipulator is not the marketplace, but the

subjective judgement of history. In the somewhat shorter run, however, the marketplace,

whether in terms of commercial sales or government project approval, is the prime

evaluation.

In the development of complex expensive technical systems of any kind, there

are various stages of test and evaluation which necessarily precede the market test.

One may say these are for the purpose of predicting both market performance and judgement

of history.

The following are three problems which make evaluating robots and manipulators

especially difficult at these early stages

t

(l) The problem of evaluating something which is "general purpose"

The designer or manufacturer of a programmable robot or manipulator asks the

question, "Vrfhat, specifically, should it be designed to do?" The answer may be a wry

smile, an evasive "we don't know yet" or a not-so-helpful generality such as "everything

the human worker can do, only faster and with greater precision". The designer is left

frustrated, since rational design tradeoffs demand precise specification of the objective

function or performance criterion.

Similarly, the purchaser or user of a programmable robot or manipulator has a problem. He is not clear on how to decide which available system is best for him,

for he doesn't know how best to specify what he needs. If he specifies required

performance in terms of the most recent or the present task as he understands it, and

the robot is designed specifically for that task, it is not likely that the robot will

be adaptable to other tasks in the future, nor that it will perform well with respect

to aspects of the task he does not presently understand well enough to specify.

Alternatively, the purchaser can specify for procurement in terms of some "worst

anticipated case", e.g. "pick-up the (heaviest) object in the (most arbitrary) location

and orientation, move it (in the least time) and make the (tightest tolerance) assembly

to another object (vrfiose position is poorly known)." However, requiring that the

robot be designed as though it is to work regularly at this rare simultaneous extremum

of all the performance variables is likely to be naive economically. In those rare

cases of an extreme in terms of one variable (weight or speed, etc.) some other

variable may well be able to give, and the greatest pay-off is likely to come with a system designed primarily for the kinds of jobs it faces most often.

What the purchaser/user and the designer/supplier need is a more explicit

basis for communicating, some better framework in terms of which the one can say what

he needs and the other can say what he can provide and both can be held accountable

for what they said.

30
(2) The problem of evaluating the machine without the iman

Programmable robots and manipulators are relatively general purpose tools, intended

to be adapted to a variety of future tasks in ways limited primarily by ingenuity of

their programmers and human operators* This dependence upon progrartmers or human

operators aggravates the problem of specifying performance of devices yet to be built

or of evaluating performance of those already built.

Can the devices be evaluated apart from their programmers/users? The answer must be a partial yes and a partial no. The problCTi is not unlike that of evaluating

the performance of an aircraft apart from its pilot.

The aircraft can, for sure, be evaluated independently in terms of the limits or envelope of its performance when "properly operated" - speed, altitude, climb, gross

turn and stall characteristics. But then there are other characteristics which have

meaning only in terms of a closely coupled man-machine control loop. That is, the

control or "handling quality" (for flying nominal maneuvers with random disturbances)

can only be solved if the pilot is characterized quantitatively in terms of the same variables as are used for the aircraft. There has been considerable progress in this

direction, and quite satisfactory mathematical models now exist, differential-difference

equations in few variables.

Of course, these "objective" performance equations are only part of the story.

Methods for determining pilots' subjective ratings of handling qualities as a function

of the aircraft's control system parameters are now relatively refined and often used.

Perhaps the same approach should be taken with robots and manipulators,

evaluation in terms of: 1) gross performance parameters of the machine only, operated/

programmed by experts or under ideal conditions; 2) combined man-machine performance

based upon nominal-task simulator tests or in-situ tests using ordinary operators in

the hot lab or mine, shop-floor reprogramming, or actual working conditions; 3) subjective

ratings by users correlated with system parameters.

(3) The problem of confusion between "tasks" and "tools" in specifying and

evaluating

Perhaps the most important "special problem" concerns what may be called the

"task-tool problem", and has to do with wrtiether one's viewpoint is of what needs to be

done (task) or vi^at is needed to do it (tool or instrument). It is the difference

between predicate and subject. It may even have roots in the classical mind-body

and yin-yang dichotomies. The point is that you need both tool and task, tool to do

and task to be done, to make sense. Viewing from one side alone gives only part of the

picture. In order to deal properly with evaluation, one first has to specify what is

the task and/or what is the tool.

Specifying the task alone . On the task side (Figure 2) one starts with a product

specification, a description of physical configuration wAiich one wants to achieve.

The product specification is of the desired central tendency as well as the variability

(tolerances), perhaps with differential value given for products whose dimensions or perfoxmance or reliability approaches the ideal.

There may be many different ways to produce the product. They will probably

Involve the steps oft 1) storage/transport; 2) materials processing; 3) assembly;

4) test/inspect. These are the gross necessities of the task. Considering, for example,

an industrial assembly task, it is clear that for specification of the initial condition

(as assembly begins) size, shape, position and orientation (and other attributes) of

the two or more parts to be assembled must be characterized probabilistically. The

same is true of the specification of the final conditions - what the subassembly must

end up to be - but with hopefully a lot tighter relationship between parts.

31
TASK TOOL

Product design specification

- geometry tolerances

" materials

Production specification

- storage/transport

- materials processing

- assembly

(initial conditions)

parts storage/transport/presentation

inspection/identification

arm/hand + table manipulation

(final conditions)

- test/inspect

Tool conf iquration specification

- geometry of structure tolerances

- sensors

- motors

- software

- human operator interface

- factory environment

- management constraints

I

Tool performance specification

- geometry envelope

- speed of movement

- accuracy and precision of movement

- range of forces which can be

applied

- interoceptive sensing capability

- exteroceptive sensing capability

range

resolution

frequency characteristics

geometrical characteristics

- software capabilities

(including accommodation, etc.)

- failure data

- ease of teaching

ad-hoc program specification

models and descriptors

of manufacturing

tasks to measure tools

tools to measure tasks

theory of control and^

computation

etc.

Figure 2. Relationships between task and tool

32
Between the Initial and final conditions of a particular subasswnbly task lie

the assembly task operations required* All the steps here more or less fall into one

of three categories: l) parts storage/transport/presentation; 2) inspection/

identification; 3) manipulation of one part relative to others (not necessarily in

order). Constraints on 1) and 2) may be determined by a given factory environment, or there may be very few constraints.

One could make a finer breakdown of elements (not shown in Figure 2) into

envelopes, or rates through state-space of gross and fine positioning movements and

application of force between parts. These are trajectories of the possible ways to

put the parts together as constrained only by the geometry and materials of the product

design.

Notice we have not yet made anything depend upon the tools (subjects). We have

only dealt with tasks (predicates) - what we need done.

Specifying the tool alone . Now let us jump to the other side of the ledger - tools. A robot tool consists of a hardware configuration and a software configuration

(and possibly constraints due to factory environment, human operator interface and

management or union rules, safety standards, etc.>). The hardware consists of sensors, motors, electronics, power transmission mechanisms, supporting linkages, bearings

and frame. This is specified in much the same way the product is (materials and

geometry) except for the software.

Akin to the hierarchy of required steps (and trajectory envelopes) for

manufacture of the product is a similar hierarchy of performance specification of the

tool - vt^iat it can do (not as before what must be done to it).

Motor performance can be specified by envelopes of possible speed and accuracy

(and precision, which is different from accuracy) and load and geometry. Interoceptive sensing (of positions and forces within the arm and joints) can be specified

separately, but usually is considered part of motor performance.

Exteroceptive sensing (of positions and orientations of external objects and

patterns of externally applied force) similarly can be specified in terms of

performance envelopes! dynamic range and resolution in magnitude and time and space.

Touch sensors (on the surface of the hand) are always exteroceptors; wrist force

sensors usually are if what is being learned is primarily about what is outside and

what to do about it.

Specification of software as programs is easy enough, but "performance

capabilities" of software ntust be specified in terms of program limitations (memory,

word length, speed for certain standard executions, etc.). Specification of

reliability is awkward here except in terms of large categories of failure events.

Accommodation, whether active or passive, is a tool property, though the

manipulator may apply and sense forces through a grasped object. It is an integrated

and high level activity involving stored program, exteroceptive sensing and interoceptive feedback control of position to proceed in some direction wdiile backing

away to relieve forces in other directions. So too are other control strategies which

close the loop through exteroceptive sensingt edge following, techniques to center

•nd align a peg with a hole, techniques to align jaws over an object, or to insure

that both jaws contact the object simultaneously when grasping, etc.

But, so far in specifying the performance limitations on the tool, we have

not had to be concerned with how best to do any particular task.

33
Selecting and further specifying a tool for a taskt ad hoc proqramnlnq* Both task

and tool are usually constrained only to a degree, leaving wide latitude for exactly

how the parts are moved or the tool Is controlled. Life gets interesting when matching

tool to the task or vice versa*

One can have several objectives or motivations in effecting this match. Examples

aret

1. Select and augment a given tool (by ad-hoc software) so that it will accomplish

a given task.

2. Find the least sophisticated tool to do a given task.

3. Find a most sophisticated task to show off the capabilities of a given

tool or software.

4. Change the task so that a given tool will suffice (through product redesign

or production technique)

Objective 1 above is expected to be most common. It starts by confirming that

the tool is capable of accomplishing the task, i.e. that the set of potential tool

capabilities and task requirements overlap in a Boolean sense. Then, one further

specifies the tool by programming to Implement that potential.

If one has a choice about tool, considering only the given task, one wishes to

minimize cost by choosing that tool for which initial cost plus additional programming

is minimized (Objective 2).

Objective 3 is to be expected when research and marketing of tools is the goal.

And, finally, objective 4 is where the whole field should eventually be spending

much more effort.

Tasks and tools as measures of each other . An obvious point is that one measure

of a task is the performance specification of the tool required to accomplish that task.

And similarly a measure of a tool is a task. In each case, as occurs in science

frequently, the measuring instrument is applied from outside the system. Thus, one might conceive of a standardized battery of tasks by which assembly tools may be

graded and compared with one another, or a standardized battery of tools by which tasks

may be compared.

III. A Suggested Taxonomy For Specifying/Evaluating Robots and Manipulators

In this section, a taxonomy is suggested for viewing the specification/evaluation

problem - a way of organizing the components of "tool" and keeping these separate from

"task", and of sorting out the "man" from the "machine", as well as the generality of

purpose of the various aspects of evaluation discussed earlier.

Figure 3 shows at left a converging tree of system attributes of "performance

to be specif led/evaluated" which combine to form (progressively left to right in six

stages) larger integral attributes and finally produce the attribute called here "total

performance". There is no assertion intended that this is the only set of terms and

combinations. It does intend to assert that one might usefully keep in view how, at

34
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each stage (environmental sensing combining with manipulator, robot-manipulator

hardware combining with software and environmental aids, complete hardware combining

with human operator, and manned system or "complete tool" combining with task) there

must be a new objective function for evaluating the combination in terms of the

component attribute parameters.

As indicated at the right of Figure 3, there are two processes by which

components of performance or total performance (i.e. pieces or all of the attribute

tree at left) become specif ied/evaluated. One process is that of the supplier of

the robot/manipulator, and the other that of the user. Each consists of a temporal

sequence of steps. The first step (expression of need) by the user sometimes triggers

the first step hy the supplier, sometimes not. Typically, at any one time the supplier

has advanced further with the specif ication/evaiuation steps than the user. The

supplier is usually quite interested in learning the results at various user steps,

for these tend to change the supplier's specification/evaiuation. This is suggested

by the feedback loop.

At any given lettered stage of either supplier or user, specification/

evaluation of any combination of attributes of the attribute tree can be characterized

by a number and letter. Some examples are given in Table 1. Some of these are

specifications or tests of raw limits on performance (of materials strength, torque

output on motors). Others might be relatively simple calibration tasks where several

hardware subsystems cooperate but without software or human operator. Still others

might require the complete prograiraned or human operated system performing a battery

of "robot I.Q. tests". Some might concern early stages of design and development.

Others might make sense only at the last stages. Others may be tools designed to measure the difficulty of tasks.

There are additional questions which are conconsnitant with developing

satisfactory means for specification/evaluation of tools and tasks within a particular application area. The first is whether a test in that one application

area can be generalized to the others, perhaps to all robot/manipulator applications.

The answer to that question will best be answered by experience and consensus after

some further effort* The second question is what kind of institutional arrangement

is most appropriate for promoting improved and perhaps standardized procedures for

conmuni eating results to the interested conmnunity, and possibly even for administering

tests. Should there be a government agency, a not-for-profit agency analogous, to the

Educational Testing Service) or no agency at all - leaving the problem primarily

to negotiations between supplier and user? Hopefully, the resolution of this

question can come out of our Workshop.

36
ample of Tests

capability limits (e.g. structural strength of a member, no load angular

velocity of a joint, maximum stall torque of a joint, minimum or differential threshold of a sensor, effective stiffness coefficient,

gross movement envelope)

calibration task (e.g. hold end effector position constant against varying

force, move end point in arbitrary straight line, move as quickly as possible and hold within end point tolerance)

general "I.Q." test (e.g. stack blocks as rapidly as possible, assemble

certain size peg and hole, follow surface and maintain contact with

maximum speed)

perform some real undersea, hot-lab, or industrial task

satisfy fail-safe criteria (e.g. shut off and hold when servo error suddenly gets large, avoid destructive collision with suddenly appearing

obstacle)

assess promise of new transducer concept (subjective assessment of usefulness in various design applications)

difficulty of task (e.g. capability of a given robot to perform task as more and more degrees of freedom are locked out, accuracy of position

sensor or servo gain required to complete assembly)

37

5.1.2

PERFOR^WJCE EVALUATION OF MANIPULATORS

FROM A KINEMATIC VIEWPOINT

by

Bernard Roth

Department of Mechanical Engineering

Stanford University

Stanford, CA 94305

ABSTRACT

The number of links and joints, as well as their types and sequence, determine

the kinematic geometry of a manipulator. In this paper it is shown that it is possible

to predict aspects of manipulator performance from this geometry. The effect of

manipulator geometry on each of the following is discussed: displacement of the free

end, coupling of position and orientation, number of ways to reach a given position,

solvability, working spaces, and approach angles.

I. Introduction

The purpose of this paper is to summarize the kinematic theory of mechanisms

as it is applied to manipulators. The question kept in mind throughout the writing

of the work was: what should the manipulator designer know about kinematics in order

to produce the best kinematic configuration? Of course those interested in evaluating

a manipulator or enunciating standards of good design would require the same knowledge.

This work represents a first attempt to bring together material which ranges in age

from two days to two hundred years. Much is known, and yet throughout this writing

I was aware of many still unanswered questions. Kinematics is today a rather active

field, so I ask the reader to keep in mind that what was unknown on August 17, 1975

may no longer be so when this work is read.

The term kinematics as used herein is in reality geometrical kinematics, i.e., we are interested in those properties of the manipulator motion which depend only on the geometry of its construction. We do not deal with properties which depend upon

the time duration of its movement; such properties are properly treated from the viewpoints of manipulator dynamics and control. No mention is made of force (although

static forces and moments are closely related to geometrical kinematics, and perhaps

should have been included).

II. Kinematic Notation

From the kinematic point of view, notation is very important. Manipulators

are commonly described by names (e.g., Unimate, Scheinman Arm) which carry no kinematic

information. Even such descriptions as elbow flexion and wrist rotation are often

ambiguous and sometimes meaningless. The same criticism can even be leveled at such

"scientific" standbys as pitch and yaw. What we seek is a standard notation which

does not rely on a manipulator being analogous to the human arm, or its free end moving

39
along special directions, or any restrictions other than those imposed by the design

itself. With this in mind, a meaningful kinematic notation for manipulators is the

one Gorranonly employed by spatial mechanisms.

The kinematic notation gives the following information about the linkage: the

type of joint between each link, and the order in which the joints are connected.

Associated with this notation is a set of parameters which give the kinematic dimensions

of each link.

The notation is based pn a single capital letter representing each joint. The

following are more-or-less standard:

R - for revolute joint, symbolically

P - for £rismatic joint, symbolically

H - for helical, symbolically

C - for cylindrical, symbolically

S - for spherical (or G - for £loboidal),

F - for Hat planar, symbolically

These joints are used to join rigid bodies, called links, in such a way as to allow relative motion between the members at the joint. The R joint is a simple hinge.

The only possible relative motion between the paired members is a rotation about the

joint axis. This is the most commonly used joint in manipulators. All members joined

in this way can easily be driven by any type of rotary actuator (motors, vane type,

gear type). Also pulleys and gears work naturally with R joints. The joint is formed

basically from one (or two) cylindrical holes and a matching cylindrical rod (usually

bushings or bearings, and end retainers are also used but these do not affect the (ideal)

kinematic behavior).

The second most commonly used manipulator joint is the P joint. This is a simple

sliding joint in which no relative rotation occurs between the jointed members. The

only relative motion is a pure (rectalinear) translation along the slide direction.

This joint is useful in connection with linear actuators, since no conversion to rotation is necessary. The name prismatic comes from the cross-sectional shape of the

joint which usually has a prismatic shape in order to prevent rotation, A common

shape is a rectangular tongue-and-groove arrangement.

The other types of joints are rarely used in manipulators because they are difficult to power. However their effects can be obtained by special combinations of

R and P joints. The H joint acts like a screw-and-nut arrangement. It can be substituted

for by a coaxial R and P joint with a constant ratio of rotational to translational

displacement, but even in this form it is not generally used in manipulators.

40
The C joint is in effect a revolute without the end constraints, i.e., sliding

takes place along the revolute axis. This joint can be formed by a coaxial R and P joint, and it is in this forrr, that it generally exists in manipulators. The R and P are independently powered and controlled. We will use the symbol RP (or PR) to denote

that the joints are coaxial and function therefore as a C joint.

The S joint can be formed by a spherical ball-and-socket arrangement. The

relative motion is spherical which means that all joints remain at a fixed distance

from the center point of the joint. In manipulators the effect of this joint is

obtained by three non-coplanar independently powered R joints. These joints are each

connected to one of the others and are aligned so that their axes always intersect

at the point which is to act as the center of the S joint. We will use '^R^ or the

symbol 3^ to denote such an arrangement. Symbolically we will show it as:

The F joint can be thought of as two flat planes sliding and turning on each

other. For manipulator purposes it can be constructed as two non-parallel P joints

and an R joint perpendicular to the directions of both P joints.

There are other possible joints, but those above are the most important. In this paper we will treat configurations with R, P, RP, and 3^ joints.

The only significance of links (i.e., rigid bodies), from a kinematic perspective

is that they maintain fixed configurations between their joints (and also their other

points and lines). In manipulator work we are usually only interested in the joints.

Hence, the dimensions of a link with, for example, two revolute joints are kinematically

significant only in so far as they fix the relative positions of the two revolute

axes. The important idea here is that regardless of the actual location, shape, or

size of the physical link it may be completely represented by the skeleton diagram

shown below. Its only two significant (kinematic) dimensions are, a , the shortest

distance between the R axes, and, o( , the angle between the axes in a plane perpendicul

to a. It is customary to call a "the length" and oc "the twist" of the link.

41
Generally two links are connected at each joint axis. This axis will have two

perpendiculars to it: one for each of the links. The relative positions of two such

connected links is given by their distance, S, along the common axis, and their angle,

6 , measured in a plane normal to this axis. S and 6, are called respectively the

distance and angle between adjacent links. The sketch illustrates these ideas.

a

Here there are two links. Link 1 has axes 1 and 2, and link 2 has axes

2 and 3, Their lengths are a^ and a respectively.

The distance between link 1 and 2 it is the directed distance ^2'^2'

2

is S,

9.xis 1

The directed angle from ^2*^1^ *° direction O^P

10 "

is e. It is customary to use a single

subscript to associate S ana 6 with a given axis; we have in this sketch S^, ©j' both

measuring the position of link 2 relative to link 1.

The symbol of the joint type (as well as the actual physical actuators) can be

placed anywhere along the axis. It is redundant to use more than one joint of the

same type to connect the same two links, hence the joint symbol for axis 2 will usually

be placed at either point 0- or P-. With this in mind if joint 2 is a R-pair then S2

is called the off-set (or tne bend, or the kink) in link 1, and 6^ is called the

rotation in the joint. If joint 2 is a P joint then is called the displacement

in joint 2. In R joints, 0 varies during motion but S is fixed by the construction;

for P joints the opposite is true.

42
The result of all this is that there are four parameters, a, oc , S , G

associated with each manipulator link. If we provide a sign convention for each of these

we have a (minimal) set of parameters which is sufficient to completely and uniquely

determine the kinematic configuration of a manipulator. It should be kept in mind that

n the parameters come in pairs: two (a, <x ) \ determine the structure of the link,

1 and two (S, 6) determine the relative

position of a neighboring link.

If we add the further conventions that: we list first the manipulator axis fixed

to the frame, and then, moving from left to right in our listing, add neighboring

joints until we come to the end-effector, we have the basic tools to classify a manipulator's structure. For example, the manipulator shown in the sketch has four

moving links, and four revolute joints. Such a manipulator is of type 4R.

All 4R manipulators have roughly the same general capabilities from a kinematic point

of view. If their values of <x.» 3j^» S. (i = 1, 2, 3, 4) are identical, they are kinematically identical regardless of tfteir actual constructional details. However,

if special values are assigned to some of these parameters (e.g.,oc= 0 or TT , or

a = 0, or S = O), some properties of the general type 4R are usually lost. The motion

parameters for the 4R are 6^, i = 1, 2, 3, 4.

As another example, consider a manipulator with a revolute joint between its

first moving link and the frame, followed in order by a revolute, a prismatic, and

then three revolute joints. The sketch shows this manipulator drawn in two forms which

are kinematically identical; its type is 2RP3R, and its structure depends upon

1' ^1' ^2' 2' ^2' 3' 3' ^3' 4' °^4' ^4' ^5' 5' ^5' 6' 6' ^6' 7*

The motion parameters for this sytem are G, , 0., S., G , G , G,.

43
We have then a notation which allows us to identify and compare different designs

from their geometric-kinematic structure. In terms of evaluation two rules will be shown

to follow; all other things being equal:

1. The greater the number of joints of a given type the more versatile

the manipulator (since it has more freedoms).

2, The greater the number of non-zero parameters, the greater and the more general) the number of possible link and end-effector positions.

The most general six degree-of-freedom systems, with either all revolutes

(i.e., the 6R) or with three or more revolutes and the rest prismatic, has 18 kinematic

design parameters (for the 6R: a^, Oc., S. + 1; i = 1, 6). Most manipulators

have six (or less) degrees-of-freedom, and so the study of kinematic manipulator-designand-evaluation is essentially the study of what happens when we assign specific values

to these 18 parameters. For additional freedoms, we gain three design parameters, and one motion parameter, with each freedom. For less than six, we lose three design

parameters with each freedom. Basically, for f freedoms we have 3f design parameters,

and f motion parameters. In the following sections we discuss the effect on performance

due to specialized values of the design parameters.

III. The effect of oc= 0 (or Tr )

When oc= 0 (or it) the link has no twist. Hence, if the two joints are revolutes,

the relative motions between its neighboring links must be so-called coplanar motions.

This means they always move in parallel planes. In the sketch, link 2 has two parallel

R joints.

Holding link 1 fixed, it is clear that

all joints in link 3 generate planar

trajectories in planes perpendicular to

the two parallel R axes. If the two R

axes were skew (i.e., / 0 or -TT ) then instead of a point such as A being confined

to a flat plane its locus relative to link 1 would be a 4th order surface called a scew (or general) torus — this will be discussed in more detail later. From the point

of view of simply maintaining a point of link 3 in a special plane relative to link 1,

the use of two parallel R joints is wasteful. Either of the joints is sufficient to give, for example, point A a trajectory in the plane. However, with two parallel joints

the point does have the fre-dom to be anywhere (within a given range) on the plane,

while if the axes are skew it can only lie on certain curves (two circles) in the plane.

If one of the parallel joints is prismatic, the relative motion of link 3 to

1 is exactly the same as if the R joint is replaced by a RP (i.e., a C) joint. The

trajectories of points on link 3 relative to link 1 are all on right circular cylinders

with the R joint as axis. The location of the parallel-axis P-joint is totally

irrelevant (from kinematic criteria). If instead of 0 or 41"

, = ~ '~2~ then the effective displacement is exactly the same as for two parallel R joints.

44
If the two parallel joints are both prismatic, the relative motion of link 3 to link 1 is exactly the same as with one P joint. Hence using two parallel P joints

is generally wasteful.

As a general conclusion: Unless special reasons exists (such as limited actuator

motion, or special workspace shapes), manipulators should not be designed with no-twist

links or with a 90 twist for RP (or PR) links. The result of such designs is simplified

and less general relative motion possibilities between the links connected to the

parallel joints.

IV. The effect of a = 0

If a = 0 in addition toOt= C (or'TT ) the two joints coincide, and the link can be

considered a null link. Its effect is the same as if we directly join its two neighbors

together with a single joint having the same freedom as the original two (now coinciding)

joints. In this way we can consider an RP joint as a null link with two one-degreeof-freedom joints, or as a single two-degree-of-freedom C joint.

If a = 0 andoCf^ 0 or'tl', we do have a link; it has the special property of having

no kinematic length. If the intersecting joints are revolutes the relative motion is

called spherical. This term is used because, as can easily be seen from the sketch,

all points on link 3 move so that, relative to link 1, they lie on concentric spheres

centered at 0, the intersection point of the axes. Also, the relative positions of

link 3 are limited to those which can be reached by pure rotations about axes through

point 0,

For a prismatic axis, a = 0 has no special meaning. In fact, a has no kinematic

significance when measured to or from a P axis: any P joint moved to any parallel

position gives exactly the same kinematic constraints! The same straight line

trajectories exist regardless of where the axis is physically located, all that matters

is its direction.

V, The general screw displacement

When cx/ 0 (or ft ) and a ^ 0, the link is considered to be general. The recson

is that with its two revolute joints along skew axes, link 2 can produce a general

relative displacement (within the range of its motion) between links 3 and 1. By general, we mean what is usually called a screw displacement. So, any displacement

of 3 relative to 1 can be obtained by rotating it about an axis fixed to link 1 (not

generally of link l*s joint axes) and translating it along this same axis. (When the

revolutes intersect or are parallel this translation is absent, and the rotation axis

always passes through the same point.) This axis,. along which the translation and about

which the rotation occurs, is called the screw axis. Furthermore, the magnitude of

the translation along the screw is proportional to a^sin (X^, The distance of the screw

axis from axis 2 is proportional to a„ (as shown on the sketch).

45
e.<^ut vaLe.i^ir screed ^or a. di spL cic€.rr\^y\t of Unk 3

lreiLa.ti\/e. to Unk 1

A

Thus, the larger a, the larger the translational displacement associated with

any changes in ®3» Clearly, when ot^ = '^/2 we have the greatest translational

effect due to link twist.

The value of for R joints in no way changes the relative displacement for

a given change in 62 and G^; it does, however, effect the final position of points

attached to link 3,

If one of the joints (of link 2) is prismatic the relative displacement will

be a screw displacement, but the screw axis will always be parallel to the R joint

(of link 2).

If both joints (of link 2) are prismatic, the relative displacement is a pure

translation; clearly the values of 6^ and 6^ do not effect the relative displacement

of link 3.

In this and the preceding two sections, we have used the relative displacement

of link 3 to link 1 to illustrate how the parameters associated with the joints of a link (link 2 in this case) effect the relative displacements of the links they join.

The conclusions are clearly equally valid regardless of where the three links are located in the manipulator chain.

The requirement for locating the free end of a manipulator can generally be

stated in terms of its position and orientation. So, as shown in the sketch, we

are often confronted with the problem of bringing a point A on the last link of the

manipulator into a specified position A*, while the orientation of this link, given

VI. Decoupling of position and orientation

46
by directions x, y, z fixed in it, changes to x', y', z*. In general three degrees

of freedom are needed to bring point A into any position, and three other degrees of

freedom to orient the last link. It is convenient to speak of these as though they

were three translational and three rotational requirements, respectively. Most manipulators however are not constructed to yield decoupled motions. Some however are. The orientation and position do decouple when the last three R joints (toward the free

end) have axes which intersect in a common point. In this case these three freedoms

essentially determine the orientation and all other joints, be they R or P, essentially

determine the position.

A six-degree-of-freedom manipulator with any ordering of three revolute and

three prismatic joints has the orientation of its end completely decoupled from the

displacement in the three P joints. Moreover, the orientation depends only on the three

rotation angles, 6^^, and the directions of the R axes — their relative locations

(i.e., their a's and S's) do not effect the orientation of the last link. Hence the

following are identical in regard to orienting the last link:

3P3R, 2PRP2R, 2P2RPR, 2P3RP, PR2P2R, PRPRPR, PRP2RP, P2R2PR, P2RPRP, P3R2P, R3P2R,

R2PRPR, R2P2RP, RPR2PR, RPRPRP, RP2R2P, 2R3PR, 2R2PRP, 2RPR2P, 3R3P.

If the first, second, and third revolute axes in each of the above are respectively

parallel, the same joint rotations in any of the above yield exactly the same orientations.

Also, if the P's are respectively parallel, in any order, between any of the above,

the same displacements along parallel P's yield the same displacement for point A. However, unless the R axes all intersect at one point, the locations of the R axes

do effect the displacements of A and so the end point trajectories will generally be

different for each of the above.

Knowing the position and orientation of the last link of a manipulator is

equivalent to fixing its position in the coordinate system of the frame. This means

that in any one position we can regard the last link as being fixed to the frame. As illustrated in the sketch for the 6R manipulator, this situation is identical to the

configuration of a closed loop linkage with its input crank in a known (fixed) position

relative to the fixed link.

VII. The manipulator as a closed loop mechanism

Cihka^e- input47
For our present purposes we can ignore the question of what type of joint exists at A; since the position of link 6 is known the joint type is of no interest. Taking this

approach we can consider a 6R manipulator, with a known end-link location, as a 7R

or a 6RP,(or a 6RX, where X is any joint) mechanism with its input crank (link 6)

in a known position relative to the frame (link 7).

This technique allows us to convert a manipulator system with n moving

links into a n + 1 link closed-loop linkage. Furthermore, if we know the location

of the last link of the manipulator, we know the input crank position (for the linkage)

and the dimensions of the fixed link. Using this idea, since we know the number of

ways a linkage can be assembled at a given crank position, we can immediately know how

many ways a given manipulator type could be positioned so that its last link has a given location and orientation.

All other factors being equal, manipulators with more possible ways to obtain

a given end position are better than manipulators with fewer ways. The general rule is

that the more general the link parameters the more ways there are to reach a given

position and orientation. For example, if we take a 6R manipulator we find that (all

other parameters being non-zero)?

if a^ .= a^ = a^j = 0 there are at most four ways

if a^ = = 0 there are at most eight ways

if a^ = 0 there are at most sixteen ways

if none of the parameters is zero there are - it is believed, although not

entirely verified - at most 32 different ways to reach the same position

and orientation.

In general using P joints instead of R joints halves the number of possible

ways. So, for example, it is believed, although not yet confirmed, that the general

5RP manipulator can reach a given end link position and orientation in 16 different

ways. When we go from an RP to an R^ construction, oc and a go to zero, and the number

of configurations also halve. Thus the 2R^2R manipulator has at most eight ways to

reach a location, while the 2R?RP has only four, and the SR?* has at most two. This

halving is not a universal rule, but it is a useful qualitative (if not quantitative) measure of which changes in a design tend to make things better or worse in regard

to obtaining more ways to reach a given location.

If we consider six-degree-of-freedom systems, the following list covers manipulators with at most two prismatic joints.

Maximum number of ways to reach

a given position and orientation

(provided the chain has no zero link-parameters)

Manipulator types

4 RPRrI'R, RRPRRP

8 2RP2R, R2RPR, RpgRRP, RP2RR^, 2RRPRP,

2RPR^, PRRP2R, RPRP2R, '^RPR,^2RRPR,

RRPP2R, 2RPR>R, PR?3R, RPRP2R, RP3RP,

RPP3R, 2P4R, P3RR^, 4R2P, 3R2PR, P4RP

48
12 3RPRP, PRP3R, 2RPRPR, RP3RP, P3RPR

16 2RP2RP, P2RP2R, RR?3R, 2RRP2R

16 (?) 3RP2R, P5R, 5RP, 4RPR

32 (?) 6R

(The question marks indicate that the last two lines contain results which are,

as yet, not completely verified.)

The above numbers are for the maximum possible ways to reach a location. For

any given manipulator the actual number of ways depends upon the particular location

and the manipulator's parameters. Clearly for every manipulator there exist locations

which cannot be reached. Hence, the actual number of ways will vary from zero, for

locations outside the zones of operation, to any number up the maximum given in the

above listing. Generally, the actual configurations exist in pairs, so we can expect

0, 2, 4, 6, ... ways. However, at a boundary of a zone of operation a pair amalgamates

into a single configuration, and so odd numbers of actual ways are also possible.

VIII. Solvability

If the motion parameters are given the position and orientation of any manipulator

link can easily be calculated. One convenient way to do this is to develop a coordinate

transformation matrix for each link and then multiply these matrices to obtain the

desired location measured in the coordinates of the fixed frame. In general this is

a very simple procedure to execute with even a small computer. P joints are simpler

than R joints, but the amount of computation is not significant even in the most

general case.

On the other hand, the problem of determining the motion parameters necessary to

obtain a given position and/or orientation is still not completely solved. A manipulator will be called solvable if the motion parameters can be determined by an algorithm

which allows one to determine all the motion parameters associated with a given

position and orientation. This definition implies that we know all possible

configurations which allow the manipulator to place a given link in a given location.

It seems likely that soon all systems will be solvable. However, at the moment, to be soljVable a six-degree-of-freedom manipulator must have at least two prismatic joints,

or a RP joint, or two pairs of intersecting R joints. In other words the 5R, IP combination (with the P in any position in the chain) and the 6R manipulator are not

solvable unless they have certain of their parameters equal to zero.

When manipulators are not solvable they can be treated by use of one of several

iterative techniques which break a displacement down into a series of small incremental

displacements. Of course an iterative incremental-displacement technique can also be

used with solvable designs. The major drawback of the iterative techniques is that

they generally yield only one of several possible configurations associated with a given location. For certain displacements there also are difficulties in getting the

iterations to converge. In addition, iterative techniques are generally more time

consuming then computations using the properties of solvability; this is especially

true for large displacements.

49
Manipulators with less than six-degroes-of -freedom may be considered as degenerate cases of six-degree-of-freedom systems and so they are all solvable.

Systems with more than six freedoms can often be treated as six-degree-of-freedom

systems with the "extra" motion parameters chosen either arbitrarily or according

to some scheme to make the motion more efficient.

Whenever we use a solvable technique the computation time depends upon the

maximum (and not the actual) number of possible ways to reach an arbitrary orientation.

Hence, the listing in the preceding section is in order of increasing computation

time.

IX. Working Spaces

The spaces associated with possible positions and orientations of the last

link of a manipulator can be considered its working spaces or zones of operation.

In determining the working spaces we ask two questions: which points can be reached?;

at each point which can be reached, what orientations can be obtained? The answers

to these questions give a measure of the efficiency of the design. For some designs

the answers are self evident, while for others they are extremely complicated.

Consider first the relatively simple case of a manipulator in a plane. If we use revolutes, we need a 3R manipulator to cover all possible positional and

orientational freedoms of the last link. From the sketch it is easy to see that

+ + a^ will be the furthest distance of A from 0, and that la^ + 33

is the closest distance when + s.^ ^ a positional working space within a distance

'1 - {a^ + '3' 0.

. . Hence if we want the maximum possible

D from 0 we need: a^ + a^ + = D,

The result is that ~ ^^'^ ^2 ^ ^3 ~ 2~ ' orientation, all possible

orientations of x, y are possible (but not at every position of A). The result is that

we have a manipulator which position-wise totally covers a circular shaped work space,

centered at point 0, with diameter 2D, but does not at each position have total

orientation freedom.

Similarly, if we use a 2PR manipulator in the plane, the workspace can be a rectangular shape with rounded ends; total orientation in parts of the space is

possible, if 0^ can vary from 0 to 2ff , Planar RPR, P2R and 2RP manipulators also give

combinations or circular and rectangular zones of operation.

TTTT

Y

t

^3

50
In general we require a six dimensional workspace consisting of three trans

lational and three rotational dimensions. The structure of such a space is very

complex. In studying such spaces it is best to start with the relative motion of two

links connected by a RR link. For the 2R manipulator shown, A has a workspace which

is a fourth order surface called a torus.

In a plane which contains axis 1 the workspace has an egg-shaped cross section if

0: . a2<aj and S2 ^ >-

1 — 1 _da—

H

When $2 / 0, if a^y the shape becomes one with banana-shaped sections,

If a^ is large enough we get overlapping regions. The effect of the various

parameters on the shape of the region is shown by the following figures for the case

S2 = 0.

51
Singulor Torus. I conicoi pcinl

10 20 30 40 50 60 70 80 90

From a structural point of view, it is worth noting that the same torus can be generated, about axis 1, by four different sets of 2R manipulators each having

different link parameters.

The orientation (x, y, z-axes) is completely coupled to the position of A, In order to obtain any possible orientation and a toroidal positional space, we need to

add three revolute joints which all intersect at the position of A:

The distance D of A from the origin 0 is given by D =

+ 2a^a2COse2, clearly the extremes are at 0^ = 0 and IT .

We can make this configuration slightly more general,

change in nomenclature in the sketch. Now D is given by

2 ^ _2 ^ 2 ^2 2 ^1

This is shown, with a slight

2 2 2 2 2 D ~ ^2 + ^2 ^2 ^ ^1 ^ 2a ja2Cos02+Za,3i^S'n-(A^5iii0^ + 2S2S2Cos''^ , and the extremes occur at

= tan

-1 fV^"^2

52
Substituting this value into D we get the conditions on a^^, a^i S^j S^* «2

torus to extend a given distance from 0 and approach within a given distance to 0,

If we use a,12and to meet these conditions, cX,

1 and the quantity

/a^ / 2 +

, S^sm -.2 . 2 ^

may be used to adjust the toroidal shape.

The actual coordinates of point A (with origin at 0, Z-axis along axis l) are

X: S2(cos6j^sine2sin oc^ + sinGj^cosGjCos c>:^cos + sinQ^ sinot^sin ^i^)

+ ajCcosO^cosQ^ - sin9^sin©2COSCt|^) + a^cose^ + S^sinS^sin c>(

Y: S2(sin9^sine2sinc^ - cose^cose2COSC<|^sino^ - cos6^sin(^cos c^)

+ a2(sin0j^cose2 + cose^sin92Cosoi^) - S2Cose^sino<^ + a^sin6^

Z: S2(-cose2sino<^sino<^ + cosix^coso^) + a2sine2sin«:j^ + S2C0Scx^

If we add an additional link, at the frame-end (called link 0, for convenience)

point A is no longer restricted to a surface. The working space of point A is the

volume swept out by the foregoing torus

Op, " "T as it is rotated about the newly added

\ TfT /n/ ^ ~ 1 I axis, axis 0,

A

(We have departed from the usual nomenclature in an effort to make it clear that the

torus generated by holding axis 1 fixed is the one that envelopes the working volume.)

Hence, by tilting the toroidal axis by ck^ and rotating about 0 we can get any point

in the work space; its coordinates, in terms of X, Y, Z given before we added axis 0,

and referred to a system with origin at 0^ and z^-axis along axis 0, are

X = Xcose - Ysine cosoc + ZsinG sinoc + a cos9

o 0 00 0000

y = Xsin9 + YcosO cosoc - Zcos9 sincx + a sin9 '0 0 oci 0000

Ysincj^ + Zcosoc + S

From these equations we can determine the shape of the working volume in terms

of its limiting dimensions. For example, the distance from 0^ to A is

/ 2 2 2 /2

v'x. + y^ + z , while the distance from axis 0 to A is /x + y o ' 0 differentiating and setting the result to zero yields the extremes.

53
With such a configuration we can reach every point in the working volume. Adding

two intersecting R joints at A allows us to reach these points with any given orientation.

As we add generality (or links) the problem of determining the work spaces becomes

much more complex. For any given manipulator the results can, in time, be computed and

plotted out, but this does not lead to a priori design rules or bases of comparison.

The problem in all its generality has never been solved, but many useful special cases have been analyzed. The most fruitful approach has relied on geometrical arguments.

Using such an approach, the following table of 120 special 6R manipulators was constructed.

The manipulators are identified by their non-zero parameters. Hence, the first one which

is listed as s^S^ has the following restrictions aj = a^ = a^ = a^^ = a^ = = = = = = 0.

The rCTnark column tells us if the configuration is: Degenerate, D, in which case in

addition to being solvable it can be put into an orientation at every reachable position;

and whether it has restricted orientation, R, or not, G, within its working volume.

Also the letter S or N indicates if a solvable set of analysis equations exists or not.

X. Approach Angles

The question of orientation of the last link is intimately related to the notion

of approach or working angles. If we assume a "terminal device" (which can only open

and close) is rigidly attached to the last link of a manipulator, and if point A is the

center of a hypothetical object to be grasped by this terminal device, it follows that

the orientation of the link determines the angle at which the object is approached.

Furthermore, if the object is stationary,

point A can be assumed attached to the

fixed frame of the manipulator.

We now return to the earlier concept of the manipulator being equivalent to a closed

loop mechanism. However, now instead of the entire last link being fixed, only its

endpoint, A, is fixed. There are several possibilities depending on the shape of the

object to be graspedo The shape dictates what type of joint we can assume exists at A. It is usually assumed that we have a revolute joint, at A, with its axis normal to the

plane of the terminal device's profile. However on occasion a spheric, cylindric, or prismatic joint might be more representative of a given service requirement.

With these concepts the range of orientation of the last link focuses on its

useful aspects, namely the angles at which the terminal device can approach an object.

Returning to the planar 3R configuration, and using these concepts, we see that the

manipulator can be considered as a 4R closed loop linkage, provided we hold the position

of A fixed. The question of link orientation then becomes one of determining the range

of rotational displacement of link 3 about fixed pivot A. This range can be called

54
Solubility and Orientation Restrictions in 6R Manipulators

MANIPULATOR REMARK MA>;iPULATOR REMARK MANIPUIATOR REMARK

1

1 ^^2 D 16. a2S3 D 31. =4^4 D

2. ^1^2 D 17. ^2^3 S G 32. S4S5 D

3. a s

1 3 D 18. 3234 S G 33. ^4^5 D

4. ^1^3 S G 19.

2 4 N R 34. 3435 D

5. S G 20. 3235 S R 35. ^4^5 D

6. ^1^4 s G 21. ^2^5 s R 36. S535 D

7. D 22. S333 D 37. ^1^2^2 D

8. 3^35 D 23. S3S4 S G 38. ^1^2®3 D

9. 8222 D 24. 3334 S G 39. ^ X

^ 2 ^ 3 S G

10. S2S3 D 25. S3S5 S R 40. ^1^2^4 S G

11. S G 26. 3335^ s R 41. ^1^2^4 S G

12. S2S4 S G 27. 3334 D 42. 3 2^ S 2

S ^ D

13. 3234 S G 28. 3334 S G 43. 3^3^33 D

14. S2S5 D 29. 3333 S R 44

.

^1^2^3 D

15. ^2^5 D 30. i— 3335 S R 45. ^1^2''3 S G

55
MANIPULATOR REMARK MANIPULATOR REMARK MANIPULATOR REMARK

46. ^1^2^ S G 63. ^V5 S R 80. ^2^4^4 S G

47. ^1^2^4 N R 64. 318335 D 81. S2S4S5 s G

48. 313235 S R 65. S232S3 S G 82. ^2®4^5 s R

49. ^1^2^5 s G 66. ^ 2^ 2^ 3

s G 83. ^2^4®5 s G

50. ^1^3^3 s G 67. ®2^2^4 s G 84. ®2^4^5 s R

51. ^1^3^4 s G 68. S23234 N R 85. ^2S"5 D

52. 318334 N G 69. ^2^2'5 s R 86. 3 2 ^3^3 S G

53. 31S3S5 S R 70. 823235 s R 87. ^2^3^ S G

54. s R 71. ^2^3^3 s G 88. 328334 N G

55. s G 72. S2S3S4 s G 89. ^2^3^5 S R

56. N R 73. S2S334 N R 90. ^2^3^5 S R

57. 3133S5 N R 74. ^ 2

^ 3^ 5

S R 91. 323384 s G

58. ^1^3^5 N R 75.

i

^ 2^ 3 ^ 5

S R 92. 323334 N R

59. ^lV4 S G 76. S G 93. ^ 2^ 3 ^5 N R

bO. ^^4^5 s R 77. 823334 N R 94. 323335 N R

61. ^lV5 s R lis. 52^335 N R 95. ^2^4^4 N R

52. s R 79. 823335 N R 96. 328485 N R

56
MANIPULATOR REMARK MANIPUIATOR REMARK MANIPUMTOR REMAK.'C

97. a s a

2 4 5 N R 105. 338/^3/^ S G 113. 333435

\ S R 1

98 . aoa , s - 2 4:) N R 106. 338/^33 S R 114. a.a,s_

J 4 D

S R

99. a. a. a. 2^3 N R 107. 338435 S R 115. 333433 S R

100. a2S-a^ S R 108. 833^83 S R 1 16 . 338333 S R

101. 33335^ S G 109. 833^33 S R 117. s , 3 , s c 4 5 D

102. s^a^a^ S G 110. S3S333 S R 118. 8,3,3- 4 4 D D

103. 833335 S R 111. 338/^33 S G 119. 3^8535 D

104. 533333 S R 112. 338483 S R 120. ass

4 5 5 D

57
the service angle; it is the angular range over which link 3 can approach point A in

the given position. In terms of the service angle, "^f* , it is possible to define a service coefficient at each point A (we use in general the total solid angle at A

f or y )i

and by integrating over the entire positional space, v, of A, we can define a service

coefficient for the manipulator

0 = — jf X edv

V *'(v) The service coefficient varies from 0 to 1, and is a measure of manipulator usefulness.

It affords a way of evaluating different designs.

If OA is R, and if a^a^^ we find there are three distinct zones as we vary the length of R.

The results are:

0= (d,^aL^f-(^-a.3f

To apply these ideas in general we would like to know the effect of all the link

dimensions — not only the fixed link — on the range of crank rotation. This is a relatively new subject and there are as yet few results to draw from. The basic

result is for the planar four-bar, it is called Grashof's criteria. Phrasing_it in

terms of manipulators we have: If OA is less than all the lengths a, and if OA plus

the largest a is less than (or equal to) the sum of the other two a's, any approach

angle is possible at this position. The only other possibility for a total range in

approach angles requires that a„ be the shortest length and that its length plus the

58
largest of OA, a^, be less than (or equal to) the sum of the other two lengths.

For this manipulator, if the variation is less than 2'rc(in the plane) at any A,

the approach angle has two separate ranges each less than -fr . These arc segments are symmetrically located with respect to line OA.

Similar, although much more complicated results are known for the RRPRRP

(with = O) and the ^RRPR (with S„ jiianipulatorsj^ The spatial manipulators for

which most such results exist are the RRRRRRR, the ^RRRRRR, R^R, ^RR, RRRRRP,

pr1?rrr.

Before leaving this topic, it is pointed out that the spherical indicatrix

yields necessary conditions in regard to the angular aspects of displacements. Often

it yields sufficient information for the entire analysis of approach angles. A spherical indicatrix is the figure formed by drawing images of the R axes of a manipulator, where all the axes remain parallel to their actual positions but are displaced so that they intersect^ in a common point. So, for example, the spherical

indicatrix of the closed loop 3RPR mechanism (formed from a 3RP manipulator with its

terminal device rotating about a fixed point A) is shown in the sketch together

with the original system. Connecting these image-revolutes, in order, yields a spherical four-bar. By drawing this four-bar on the unit sphere we can determine the

limit positions for the third link which is the end-effector. The general rule is

that if the spherical linkage formed from the indicatrix has a limit position, the

actual link cannot rotate beyond that position.

3

1

this Jc'rzcjt'ion.

3"

59
REFERENCES

For Section II: The kinematic notation described herein was originated by J,

Denavit and is described in the last chapter of the text by Hartenberg and Denavit (l). Its first application to manipulator seems to be due to Pieper (2), and Pieper and

Roth (3).

For Sections III, IV, and V: For a modern discussion of screw displacements

see Roth (4), and Tsai and Roth (5).

For Section VII: The idea of considering a manipulator as a closed kinematic

chain seems to have originated with Pieper (2), and Pieper and Roth (3). The

tabulated results follow from many sources, good bibliographies and many new results

are given by J. Duffy, J. Rooney, and co-workers (6, 7, 8). The results marked with

(?) are due to Roth, Rastegar and Scheinman (9).

For Section VIII: The notion of solvability is due to Pieper (2), and Pieper

and Roth (3).

For Section IX: The figures showing the torus geometry are due to Fichter and

Hunt (lO), the equations and tables are from Pieper (2),

For Section IX: The idea of service coefficients (and the figure for 0 vs. R) comes from A.E. Kobrinski and his co-workers (11). Grashof's rule is described in (l);

for some spatial versions see, for example, (12, 13, 14), The spherical indicatrix

is an old concept, for a recent discussion see (8).

1. Hartenberg, R.S. and Denavit, J., Kinematic Synthesis of Linkages , McGraw-Hill

Publishing Co., 1964.

2. Pieper, D.L., The Kinematics of Manipulators Under Computer Control , Ph.D.

Dissertation, Stanford University, 1968, pp. 157.

3. Pieper, D.L. anc: Roth, B., The Kinematics of Manipulator Under Computer

Control," Proceedings 2nd International Congress on The Theory of Machines \,

and Mechanisms , 1969, Vol. 2, pp. 159-68.

4. Roth, B., "On the Screw Axes and Other Special Lines Associated With Spatial

Displacements of a Rigid Body," Trans. ASME , Series B, Vol. 89, No. 1,

1967, pp. 102-10.

5. Tsai, L.W. and Roth, B., "Design of Triads using the Screw Triangle Chain,"

Proceedings 3rd World Congress for the Theory of Machines and Mechanisms , 1971, Vol. D., pp. 273-286.

6. Duffy, J. and Rooney, J., "Displacement Analysis of Spatial Six-Link 5R-C

Mechanisms," Trans. ASME, J. of Applied Mechanics , Sept. 1974, pp. 759-66.

7. Rooney, J. and Duffy, J., "On the Closure of Spatial Mechanisms," ASME paper

No. 72-MECH-77, 1972.

, - . I

I

60
8. Duffy, J. and Rooney, J., "A Foundation for a Unified Theory of Analysis of

Spatial Mechanisms," Trans. ASME , Vol. 97, 1975.

9. Roth, B., Rastegar, J., and Scheinman, V., "On the Design of Computer Controlled

Manipulators," On the Theory and Practice of Robots and Manipulators , Springer Verlag, Vol. 1, 1974, pp. 93-113.

10. Fichter, E.F. and Hunt, K.H., "The Fecund Torus, its Bitangent-Circles and

Derived Linkages," Mechanism and Machine Theory , 1975, Vol. 10, pp. 167-176.

11. Vinogradov, I.E., Kobrinski, A.E., Stepanenko, Y.A., and Tives, L.I.,

"Details of Kinematics of Manipulators with the Method of Volumes," (in Russian)

Mexanika Mashin , no. 27-28, 1971, pp. 5-16.

12. Parmadi, P.R. and Freudenstein, F., "On the Motion of a Class of Five-Link,

R-C-R-C-R, Spatial Mechanisms," Trans. ASME , Vol. 97, 1975, pp. 334-39.

13. Gupta, V.K. and Radcliffe, C.W., "Mobility Analysis of Plane and Spatial

Mechanisms," Trans. ASME , 1971, pp. 125-130.

14. Freudenstein, F, and Kiss, I.S., "Type Determination of Skew Four-Bar

Mechanisms," Trans. ASME . Vol. 91, 1969, pp. 220-24.

61

5.1.3

PERFORMANCE EVALUATION OF ROMANSY*

FROM THE

VIEWPOINTS OF MECHANICS AND CONTROL

A.E. Kobrinski

Academy of Sciences

Moscow, U.S.S.R.

1. Robots and manipulators being highly functional are capable of reproducing

a wide range of motions and movements. Their functional system is ensured by a large

degree of freedom of the actuators, i.e. by considerable motion redundancy.

High functionality and motion redundancy are vital features of robot and/or

manipulator systems (RMS) which largely determine the contents of the problem of

performance evaluation under discussion.

I agree that this problem should be discussed from various standpoints and,

therefore, propose to deal with questions of mechanics and control bearing on it.

We know that the existing methods enable us to analyze every particular

motion of the robot and to obtain its geometrical, kinematic, accuracy, control and

dynamic characteristics. But this is not sufficient to make a complete appraisal

of RMS qualities. For this purpose global appraisals are required, appraisals that

would cover the general properties of the whole of its configuration space and the

entire plurality of its motions in this space, and not merely separate conditions of

the system. In other words what we need are appraisals that would be adequate to high RMS functionality, that would help compare the different systems and reveal

their advantages and weaknesses. The examples given below will give an idea of the

ways that make it possible to obtain such appraisals.

2. Let us assume that we want to appraise the design of the manipulator hand,

to see whether the chosen length of the elements, the combination of rotary and

translation joints and limitation of motions in these joints, are expedient. To put

it in a nutshell, we want to know how good the structural and geometrical properties

of the hand really are and if it is possible to improve them.

Besides, we do not yet know the concrete motions the hand will be required

to perform in the execution of work operations. We only know that its gripper will

have to pick up, lay down, move from place to place, turn, unscrew, and insert various

objects, etc., which may be located at various points of the manipulator work space

and may be oriented in various ways at these points. In other words, we are eager

to secure answers to our questions without looking into infinite pluralities of motion

tasks and work operations for which the given robot may be used.

How are we going to get these answers?

Let us place the manipulator gripper in a point in its work space (P, see drawing below).

* ROMANSY - Robot and/or manipulator systems (RMS)

63
Fig. 1

Do you agree that the greater the freedom of movement enjoyed by the gripper

around this point, or to be more exact, the greater the space angle f which the

gripper can describe around it the better will be the performance of the hand? Naturally, we are dealing with only one point at the moment*

As we see it, it is difficult to raise serious objections to such a hypothesis.

Assuming that this hypothesis refers to an arbitrary point, it would be

correct to say that the size of space angle V or the sizeless value Q= y^y^-rr

proportional to it may serve as a criterion for the appraisal of hand performance in

any point of the given work space.

And now it will be easy for us to obtain the global quantitative appraisal

of performance we need, for instance in the form of

as a mean value of performance 0 established for the entire configuration space of

the manipulator hand. It appears obvious that the greater this value is, the better

is the hand and its performance* and the broader are its functional potentialities.

It follows herefrom that it would be advisable to use this criterion in design and in

comparing various models. '

64
Value (l) may be given a natural statistical interpretation. It will

characterize the probability with which the gripper of the manipulator may be oriented

in a random direction at a random point in the work space (it is assumed that random

distributions are uniform). It is again obvious that the greater the probability

the higher the performance of the hand.

3. Global appraisals such as the appraisal of performance may be used as characteristics of other RMS properties.

For instance, in the case of industrial robots the accuracy of positioning

of the gripper (in position control systems) is highly important. The same is true

of the accuracy ensured in the reproduction of the set trajectory (in a continuous

control system). It should be noted that the information on the accuracy of the

available systems produced by the firms or quoted in descriptions are of a most

approximate nature.

It appears obvious that the accuracy characteristics of one and the same robot are different in different points of its work space. It is only a global

appraisal obtained for the entire work space that will give an adequate probability

characteristic of accuracy as a means of comparative analysis of various design models.

As a rule, RMS actuators are open kinematic chains of the rod type. This

considerably lowers the rigidity of the system and causes low frequency components to

appear in the frequency spectrum. This circumstance is complicated by gaps in the

mobile joints, extended hydraulic and pneumatic communications and finally by the

elasticity of the elements themselves. It should be pointed out that the length of

these elements is many times greater than the width. In the face of these circumstances

it is both interesting and of practical importance to study the dynamic characteristics

of RMS. It is obvious that these characteristics may be different in different

positions. It appears that to compare the vibration characteristics of the different

systems global appraisals are again required.

I cannot say what other appraisals are necessary to secure the client's

confidence in new automation means and to get him to use it in industry. It is probable

that these questions will be discussed at the present Seminar or at other seminars of

this kind. At the same time I am of the opinion that the method of appraisal dealing

with robot characteristics independent of concrete external actions* may be used not only in the study of hardware, but also of the software, particularly when it concerns

so-called animated robots.

The progressive idea of supervisory control (W.R. Ferrel, T.B. Sheridan)

has confirmed the validity of the conception of the tri-une operator-computer-robot

complex. The artificial intelligence system supporting this complex should ensure

effective cooperation of the operator and the computer with the robot and between

themselves and contain information that would provide automatic control of the robot

in intervals of self-contained performance.

* This method is similar to that applied in the theory of oscillations. In keeping

with it the free oscillations of a system characterizing its own properties are studied

above all.

65
In other words, the robot should be provided In advance with a v^ole set of

"behaviours". It will be necessary to determine the criterion of these behaviors so that

the robot could be guided by them in automatic performance.

It is not the object of this paper to give a detailed analysis of the existing

or possible artificial intelligence systems. But you can hardly deny that one of the

important tasks of the theory and practice of robots is to compare different approaches

and principles in their organization* I hope that the examples quoted below will give

some idea of what is meant here.

4, We have already mentioned above the considerable motion redundancy of the

robot which is intended to ensure tremendous motion potentialities* Though the

actuator of the robot or its gripper may be designed to perform a wide range of tasks,

though the principles for the organization of the artificial intelligence system may

vary widely, the function of one of its levels (let us term it the motion forming level)

will remain unchanged* This level determines the laws of motion of all the links in

the system (with the exception of the gripper whose motions are determined by the

assignment). To accomplish this task it will be necessary to devise a general and

rational method to overcome motion redundancy.

3 Permit me to explain how we approached the solution of this matter.

I shall begin with quoting a simple example to explain the idea which forms the basis

of this method.

Let us assume that we have a two-dimensional two-link kinematic chain

(see Fig. 2 below). We wish to shift the end point of that chain from position A to position A. There are many ways In which this can be achieved*

Fig* 2

For instance, the motion of the two link unit may be effected in a way to

make its end point move along the straight line A A (bearing in mind that a straight

line is the shortest distance between these points)*

However, we took a different course of action* Our requirement was to ensure in the process of the shift from A to A a minimum sum i Tz ) turning

angles described by the links of the kinematic chain* We feel that it is precisely

such movements that are most economical and, therefore, rational* The fact that, owing

to the non-linear character of the system, the end point will move along a gentle

curve instead of a straight line only shows that economical rational movements should

be soft and smooth, and by no means rigid or angular* That is precisely how the

ballet dancer, gymnast and efficient operator shape and execute their movements.

The natural grace and beauty of their movements is hardly in contradiction with

economy of energy*

66
In generalizing the idea of a mechanism of infinite complexity we formulated

(in 3.) a special functional of the type of

fl'l f]fJ^)\ ^

(II)

-

M^ich we named "volume of motion". This functional helps form criteria for the appraisal

of certain "qualities" of a trajectory in the space of system configuration.

If the system redundancy is considerable, this idea can also be used in cases

of free motion of the gripper and also »^en its motion has been planned in advance

by the higher levels of the artificial intelligence system. This having been done,

it may be considered that the robot has been provided with a rational (from our viewpoint) element of motion behaviour. The robot will uniformly use it in the accomplishment

of various motion tasks.

Other approaches to the solution of the problem of overcoming redundancy

are quite possible and they in fact exist. It would appear to me that it would be most

interesting to compare them,

5, In discussing questions bearing on the construction of robot and manipulator

motions it would be impossible to ignore the task of surmounting obstacles. In designing robot motions in a medium with obstacles, in addition to conditions one, arising from the set motion of the gripper, and two, determined by criteria of

optimallty of motions of all the other links in the system, a new group of conditions

appears which is created by the external medium (environment). I do not intend to

discuss the numerous ways in which tasks of overcoming obstacles are posed. I shall

only set forth our approach to its accomplishment^''

It is based on the modelling of a quality that is inherent in simple living

organisms. It is know as tropism. By this we understand purposeful movement of an organism resulting from the effect of unilateral stimuli on it.

In the case of a technical device the role of such a "stimulus" would be

played by information on the mutual positions of the robot and an obstacle in its work

space. By "tropism" we mean the movements of the robot away from the said obstacle.

It is noteworthy that such motions are effected, thanks to the robot's motion

redundancy.

The mutual positions of the robot and the obstacles are characterized

in 4, by the function of the distance

^ being the distance between the two points in the work spacei the lower edge being

formed by any two pairs of points, one of which belongs to a link in the kinematic

chain and the other to obstacle D, If the distance between robot link and any point

of an obstacle becomes dangerously small, the latter intruding into the safety zone, the system of tropism starts to function,

Overcming redundancy and surmounting obstacles are relatively simple elements

of motion behaviour. At the same time I would like to emphasize once more that in our work on these elements we sought as always to apply the same method which has enabled us to look into the qualities of the robot (its artificial intelligence) regardless

of the character of external stimuli, regardless of the concrete motion assignment

and concrete form of obstacle.

67
As in the past reference is being made to the free qualities of the robot.

The characteristics of these features are essential for the appraisal of the quality

of the system which the designer may offer the client on presentation.

The motion behaviour of a "skilled" robot must include more complex elements.

Thus* tropisM will not always ensure success in surmounting obstacles. Then the need

arises for such elements as motion adaptation and self-training.

In emphasizing the importance of appraising the qualities of an artificial

intelligence syston I had in view the discussion of the structure and contents of the

"library" comprising the motion behaviour elements of the robot, the qualitative and

quantitative criteria of such behaviour and, of course, their effectiveness in the

solution of the practical problems of automation.

A philosopher of antiquity taughtt "Know your own self." In the stem area

of automation this wise thought could, perhaps be enlarged t "Know your own self and

your creations." The better we know them, the greater will be their potentialities.

This will enable us to explain them in more accurate and clear terms to the wellwishing listener and increase the chance of winning him over to our side. This is the

ultiaate objective of our Seminar. If our ideas do not coincide at first contact and

if our hearts do not beat in unison, it really does not matter. However, even at first

contact it would be preferable to have nothing to do with faultfinders.

Permit me to express my gratitude to the organizers of the Seminar for

granting me the opportunity to speak on a matter of great importance to robots and

manipulators.

REFERENCES

1« Vinogradov, I.B., Kobrinski, A.E., Stepanenko, Y.A., Tyves, L.I. Method of Volumes

and Manipulator "Service". Mashinovedeniye , No. 3, 1975.

2. Kobrinski, A.E. Volumetric Criteria in Service Analysis of Manipulators. Advances

in External Control of Human Extremities . Belgrade. 1970.

3. Kobrinski, A.A., Kobrinski, A.E. Formation of Motions in A Manipulation Systems*

Papers of the U.S.S.R. Academy of Sciences. Vol. 224, No. 5. 1975.

4. Kobrinski, A. A., Kobrinski, A.E. Formation of Motions in a Manipulation System

in a Medium with Obstacles. Papers of the U.S.S.R. Academy of Sciences. Vol. 224, No. 6, 1975.

68
5.1.4

PERFORMANCE MEASURENENT AND EVALUATION

OF

GENERAL PURPOSE MANIPULATORS

Richard L. Paul

Stanford Research Institute

Menlo Park, CA 94025

I. Overview

This paper will evaluate the performance of general-purpose manipulators by

comparing them to our only true general-purpose manipulator, the human arm. In this

comparison, some fundamental differences will be demonstrated. These differences, which

facilitated the initial development of mechanical manipulators, now limit their further

development. By changing the design perspective to eliminate these differences, a more truly general-purpose manipulator can be created.

First, we will define the performance of a general-purpose manipulator through

a functional definition of the human arm: weight, strength, actuators, control. In terms of this definition, we will consider available manipulators in order to isolate

key differences and equivalences. This will lead into a discussion of the high-tolerance

machine-tool approach as opposed to the sensory feedback, multimode computer servosystem. Finally, we will attempt some performance specifications for the sensory

feedback system,

II. The Human Arm

In this section we describe the human arm as if it were a mechanical manipulator.

This description serves as the basis for a comparison with existing mechanical manipulators. All tasks can be performed by the human arm and hand either alone or in

conjunction with an appropriate tool. Our evaluation is based on the assumption that

the arm performs most tasks, with the exception of holding and pushing, by using a tool.

By restricting ourselves to the "arm and hand-holding tool" model, we can greatly simplify the problem of evaluation. Many mechanical systems can be compared

to suchj^a model, whereas no system can be compared to the human hand itself. To quote

Bejczy

:

(1) The hand is both a powerful and delicate tool , and also a sensory organ through which information is received and transmitted.

It is difficult to evaluate the relative importance of the hand as a tool and as a sensory organ; functionally it is both or either.

(2) Philosophically, the hand can be regarded as one of the

major determining factors of human evolution. Together with man's

brain and binocular vision, the hand enabled him to be a tool user

and tool maker, and to explore, manipulate and change the physical

environment.

69
(3) The function of the arm is to position the hand (the

terminal device), act as a mechanical connection, and as a power

and sensation transmission link between the hand and the human.

The full meaning of the arm is revealed by the hand.

While we are considering the hand only when it is holding a tool or grasping

an object, we are interested in it as a "terminal device" to which forces and vibrations

are transmitted through the tool it is grasping. We are not interested in digital

manipulation tasks in which the fingers play a key part, such as picking a small nut

out of a bin and starting it on a screw; we would use a feeder and tool to perform

such tasks.

The human arm is, as a first approximation, a six-degree-of-freedom manipulator

consisting of two links — the upper arm and forearm — with all revolute joints.

It is lightweight and strong, with a strength-to-weight ratio of approximately five

to one. Each link of the arm consists of bone, is strong, rigid, and resistant to

damage. The joints connecting the links are almost friction free, but require the

exertion of maintaining forces between the links. The actuators are muscles and work

in opposing pairs, acting on the links through tendons. The difference in force of the

two tendons appears as a torque acting on the joint, while the sum of the forces acts

to maintain joint closure. The forces of the joint are no more than necessary for any arm configuration and task.

Such an actuator system is back-drivable, since motion at the joint can be in

either direction in response to both internal and external torques exerted at the joint.

We will refer to this characteristic as "compliance". This has important self-protective

features in that as the external force increases, the joint moves in response. (In

contrast, systems such as worm-gear drives cannot be back driven and mechanical failure

may occur.)

The muscle actuator system of the human arm has great overload capabilities

and rarely works at a constant power level so characteristic of mechanical systems.

The muscles have lovj inertia and no backlash.

The joints are instrumented for force, velocity, and position, but in a non- linear manner, being very sensitive to small changes. Position control is such that

the hand vibrates around plus or minus one millimeter.

An interesting arm control theory is that most tasks are learned, and are executed

by controlling the timing of the switching on and off of different muscle sets. This

form of control results in high-energy efficiency.

Finally, the muscles provide a shock-absorbing cushion for the links and joints

in case of collision.

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III. Existing Manipulators

Existing manipulator systems fall into two main classes:

. Remote-handling teleoperators

. Robots

Remote handling teleoperators are characterized by the full-time interaction

of a human operator. They are frequently master-slave systems with bilateral servos allowing the operator to feel the forces that are being exerted. Vision is one of the

primary control input signals that the operator uses in an intelligent manner to accomplish a given task. A powerful method of control uses an exoskeleton that surround

the operator's arm. Such a system, coupled with a bilateral servo, implies a manipulator kinematically resembling the human arm.

These systems are, however, tools and will not be considered further.

The second class of manipulators, robots, are an attempt to replace human

manipulative abilities v;ith some form of mechanical arm and artificial neuromuscular

control. Two major problems arise: first, humans normally have two arms; and second,

humans have mobility. The lack of a second arm may be partially compensated for by

providing jigs and clamps to perform as an elementary other hand, or by attempting

only clearly defined one-handed tasks. Many tasks currently handled by robots are of

the materials handling type (such as unloading a press) for which one hand is quite

sufficient. When task complexity increases, the lack of a second arm becomes more

apparent.

The problem of lack of mobility usually results in a basic redesign of the arm. The replacement of one or more rotary joints by prismatic joints maintains the number

of degrees of freedom of the arm while adding some limited form of mobility. It is hard

to seal prismatic joints compared to rotary joints and difficult to pass control and

actuation signals through them to outer joints.

Mechanical manipulators usually have six degrees of freedom. They have two or more links with a combination of revolute and prismatic joints. The strength-to-weight

ratio is considerably less than unity. Each link of the manipulator consists of metal,

which is strong and rigid. The joints are bearings, which are strong and precise.

IV. Comparative Evaluation

The actuator systems of mechanical manipulators show the first major divergence

from the human arm model. A mechanical substitute for the muscle-tendon combination

has not yet been found. The actuators in mechanical manipulators are either hydraulic

or electric. The hydraulic systems are strong and rugged but, unlike the human arm, are not back-drivable. Electric systems, although rugged, are heavy and require gear

reductions with attendant backlash. These systems have high static friction and low

back drivability.

In speed and acceleration, hydraulic manipulators perform comparably to the

human arm, but because of their greater structural mass, greater forces are involved,

making them dangerous. Electric-motor-powered manipulators are generally slower and

weaker than the human arm.

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Position sensing of the manipulator is accomplished by measuring the Joint . angles; such methods using resolvers and encoders have led to high accuracy, linearity,

and resolution.

Joint velocity is normally measured by a tachometer generator, either on the

motor shaft of electric-motor-powered manipulators, or geared to the joint in hydraulic

manipulators. Joint torque is usually measured by strain gauges mounted in the links

themselves.

Joint torque is closely related to motor current in electric-powered manipulators

whereas in hydraulic manipulators velocity is related to servo valve opening. Thus

these variables may be inferred rather than measured.

The main differences between our prototype general-purpose manipulator, the

human arm, and available mechanical manipulators appear to be the followingj

. The actuators of the human arm are direct, lightweight, low inert'ia,

friction free, and strong; their rest state is free. Hydraulic actuators

are stronger, but they are heavier and their rest state is rigid.

Electric actuators are heavy, weak, suffer from backlash, and have

high static friction.

. The human arm has sensors that are very sensitive, particularly to small

changes. Mechanical manipulators* position sensors are linear, with

high resolution.

. The mass and inertia of the human are low; it has the capacity for

high-speed actions. In mechanical arms, the mass and 'inertia are high,

leading to slow actions in electric powered manipulators and to excessive force in hydraulic manipulators.

With these differences in mind, we now consider the development of the mechanical

manipulator and the compensation necessary to provide an apparently equivalent system

to the human arm.

V. Manipulator Development

The first major area of application of manipulators was in the field of material

handling. These tasks were predominantly position defined, that is, in such tasks

as unloading a press, where the position of the press and the conveyor relative to the

manipulator remained constant. Manipulators were able to handle such tasks by taking

advantage of the high-resolution, accurate position sensing, and high-speed performance

of hydraulic actuators. In material handling work, the manipulator is run as a positioning device and a program consisting of a series of positions is repeated

continously. Servomechanisms or linkages force the hand to take a prescribed

trajectory in space and are blind to what and where things are in" the environment.

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The differences between the manipulator and the human arm are not important

in this case; no compliance between the manipulator and the workpiece is required. The

only sensors required are position sensors. The mass of the manipulator is masked

by the strength of the hydraulic drive. The weight of the drive is not significant

as the system is not mobile. The fact that such a manipulator required a tremendous

power input was unimportant because of the availability of cheap energy coupled with

the lack of mobility, which obviates the need to carry a portable power supply.

This same technique has been extended to such tasks as spot welding, spray

painting, and continuous-path arc welding, all of which are position-controlled tasks.

Not until assembly tasks were attempted did the position-controlled approach

present problems. In order to insert a pin into a hole, by position control, the

absolute position of the pin must be maintained coaxial with the hole axis to within

the clearance between the hole and shaft. For most assemblies, this tolerance is of

the order of a thousandth of an inch. This presents a problem in manipulator design.

Even where the joint position control is accurate enough, structural deflection and

thermal effects often far exceed the required precision. The only solution for a position-controlled device is to redesign the manipulator along the lines of a machine

tool in which these high tolerances can be met.

The resulting manipulator would be costly, massive, and thus slow, and would

lack the ability to reach into odd corners — a desirable feature in manipulators.

Despite these drawbacks, such a system may prove optimal for the assembly of numerically

controlled machined parts in which the maintenance of tolerance must be carefully

controlled. For the large mass of goods assembled not only is tolerance poorly maintained, it is unnecessary. For example, the four holes used to hold an inspection

cover on a machine may have a clearance of a few thousandths of an inch but may be

located only to within a tenth of an inch of nominal. Such an item cannot be assembled

by any machine that relies on the maintenance of high tolerance.

VI. Sensory Feedback — Example

How can a task such as that described above be accomplished with existing manipulators? The following excerpt from "The Use of Sensory Feedback in a Programmable

Assembly System" describes such an existing system performing the assembly of a pump,

"The arm has six joints (five rotary and one sliding) and it is possible to

place the hand at any position and at any orientation. Each joint is powered

by an electric motor which is under computer control. The joint positions

are measured by potentiometers and are read into the computer via A/d

converters. Similarly, the joint velocities are read into the machine via

a/D converters from tachometer generators. A real-time program (the servo

loop) directly controls the joints' forces and indirectly controls joint

velocities and positions. Every sixtieth of a second the servo reads the

position and velocity information and determines the joint output torques

from the difference between the observed and planned values ^A more detailed description of the servo loop can be found in Reference 3.

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"There is a set of equations based upon the kinematic structure of the

arm which relates the force, position, and velocity of the hand to the

combination of forces, positions and velocities of the six joints.

These equations ... are solvable on the computer even though they

contain some degenerate sub-cases. The solution routine is currently

part of the planning section and is used to compute the forces required

to compensate for the weight of the arm and any load it may be carrying.

These compensating forces are always applied when the arm is in motion.

Thus, if all the brakes are turned off the arm will not fall; it will

remain stationary, but will be free to be moved manually in any direction.

"If we want the hand to exert a force in some direction, the solution

routine can be used to compute the required joint forces. When these

forces are added to the normal compensating forces the arm will exert

the specified force.

"Normally, when we have the arm exert a force, we want the hand to be

free to move in the direction of the force. Sometimes it is important to

provide some additional freedom so that the arm can comply with external

constraints. For example, if we want the arm to slide an object across

an essentially horizontal surface, we want to allow the arm to move up

and down so that it can conform with the surface as it moves across it.

This freedom is achieved by servoing all the joints except one joint

which provides for a vertical motion. This one unservoed joint is

called a 'free* joint. Free joints can also provide the freedom to spin

about some axis. In the pump assembly, for example, after the pump has

been located and picked up, it has to be placed in a standard position.

The standard position is defined by a rectangular corner formed by a pair

of aligning blocks. The first step in this alignment involves positioning

a straight edge of the pump base along a surface of one of the blocks.

This is accomplished freeing the joint which allows the base to spin so that it can align itself with the surface . (See Figure 1.)

"... A motion of the arm then consists of a trajectory, some compensating

forces, and possibly a force to exert and some joints to free. In addition,

the termination of the motion has to be specified. It can be defined as a position to be reached, a force limit to be reached, an activation of a touch sensor, etc. Thus, the arm can be told to screw in a screw until

a certain torque is reached, or it can be told to insert a shaft until a certain force limit is reached (indicating that the shaft has been seated).

The next section will explain in detail how the arm is programmed to

perform this type of feedback.

"The positioning of the pump base relative to the arm is not accurate enough

to allow the arm to insert a pin in a number 10 screw hole reliably. Therefore, to increase the reliability, a spiral search is used to try all nearby

locations if the initial insertion attempt has failed.

Figure 2 shows the arm inserting a pin in a hole. The first insertion

attempt fails because the pin lands on the top of the base (see Frame B in

Figure 2). The second attempt succeeds,

"Three things can happen when the arm is trying to insert a pint (l) the

pin can go in the hole, (2) the pin can miss the hole and land on the top

of the base beside the hole, or (3) the pin can miss the hole and also miss

the top of the base. To test for these three possibilities the insertion

is broken into two parts:

74
75

.A. Try to insert the pin part way ... if it fails to go in

part way, it must have landed on top of the base beside the

hole, so continue around in the spiral and try another spot.

If it went in part way, go to step B.

B. Try- to seat the pin in the hole (i.e., move down a short

distance and expect to meet some resistance as the pin seats

in the hole)... if no resistance is felt, the pin must have

missed the hole and the top of the base, so continue around

in the spiral. If resistance is felt, the pin is properly

seated.

"What follows is a hand language program to carry out this algorithm. It

Is included along with a detailed explanation of the various instructions

in order to show the current level of programming required by the

system.

"The position of the hand to pick up the pin is referred to as P. This

position is defined by moving the hand to .where the pin is located and

typing 'HERE P.* The program reads the current position of the hand

and stores it In P. Similarly the hand (holding the pin) is moved to

the position for insertion and 'HERE T' is typed. Manually moving the

arm- to define positions and orientations is the easiest way of programming some assembly operations. It is a form of 'programming by doing' or 'learning by doing'.

MOVE P CLOSE 0.1

MOVE T SEARCH .07

MOVE T STOP [0 0-50] • FREE X, Y

CHANGE[0 O-ll 0.6

SKIP 23

AOJ LI STOP [0 0-50]

FREE X, Y CHANGE [O O-l] 0.6

SKIPN 23

AOJ LI SAVE H OPEN .5 CLOSE 0.1

OPEN 1

GO TO THE PIN

GO TO THE HOLE

GO TO THE HOLE

; TRY TO GO DOWN WITHOUT MEETING RESISTANCE

; SHOULD MEET SOME RESISTANCE

; AND CHECK THAT IT IS STILL THERE

"The first instruction generates a trajectory from the current location of the

hand to the position 'P.*. The hand is then in position to grasp the pin.

The next instruction, 'CLOSE 0.1', causes the fingers to close until they

grasp something. Every time the hand grasps anything, the minimum thickness

must be specified, and forms an implicit inspection check. If the grasp is

made and the check indicates that the opening is less than the minimum

specified, the arm will stop operation and indicate the error.

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"With the pin now in hand the arm moves to the insertion point at

'T'. The 'SEARCH .07' instruction sets up counters to conduct a spiral search of .07 inch steps. We now enter the insertion loop

at label LI, a move is made to 'T' and the hand is directed to move

down 0.6 inches by the CHANGE instruction. The numbers within

square bracket '[O 0-l\ ' indicate the direction and the scalar

•0.6', the distance to move. The previous instruction 'STOP o[0-50]

will cause the arm to stop if the force in the downwards direction

exceeds 50 oz. during the 'CHANGE'. Now the relationship between

the position 'T' and the hole is such that if the pin is inserted in

the hole it will meet no resistance during the 0.6 inch motion.

If the pin is beside the hole and lands on the top of the pump, the

force will quickly reach 50 oz. and the hand will stop. If the hand

fails to stop on the force limit, indicating that the pin is either

in the hole or has missed the hole and the top of the base, an

'ERROR' state is generated. In this particular case, the error is error 23. The instruction following the 'CHANGE', 'SKIPE 23' will cause the next instruction to be skipped if the error occurred,

indicating in this case that all is well.

"If the pin has landed on the top of the pump, missing the hole, the

force limit is reached and the arm stops without generating an error

state. When the SKIPE 23 instruction is executed no skip occurs and the

AOJ LI instruction is executed. AOJ is a mnemonic for 'add and jump'

The adding that occurs is the addition of the search step to the current

position. The jump is to the label, LI, and the spiral search continues.

The arm will stay in this loop, searching around 'T' in 0.07 inch steps

and trying to insert the pin in the hole until the pin moves down without

meeting resistance.

"After the pin has successfully been inserted part way, the stopping force

is set to 60 oz. and the hand is driven down 0.6 inches. If the pin

is in the hole, the hand will stop before going 0.6 inches and no error

will occur. The error test is a 'SKIPN 23' instruction which causes a skip if error 23 does not occur. If the pin has missed everything, the

'AOJ' is executed and the spiral is continued.

"The 'SAVE H' instruction saves the position that the hand was in when it

inserted the pin. Thus, to return to that position, the following

instructions could be executed:

MOVE T RESTORE H

The 'RESTORE H' modifies the position T by the saved difference H,

"The last two instructions double-check the pin placement by making

sure that the pin remained in the hole after the hand released it.

More is said about this type of checking in the section on touch

sensing."

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VII. Sensory Feedback — System

The method of manipulator control used in the pump assembly task differs in

two key respects from conventional methods of manipulator control. The two control

functions are compliance, which is the ability to exert arbitrary force, including

zero force, at any joint, and the ability to change servomodes as a function of the

algorithm.

The electric-motor-powered manipulator has back-drivability characteristics

that give it some compliance. The use of a computer with sensory inputs, position,

velocity, and output torque would give it the ability to change servomodes.

In the hydraulic manipulator, velocity output is characteristic, and forcesensing servo loops must be included to provide the necessary joint compliance. Such

systems are, however, vulnerable to damage if the rate of application of external

force exceeds the rate of response of the servo loop.

If force-sensing elements are to be used, either to provide compliance in

a hydraulic manipulator, or to increase compliance in an electric manipulator, the

force-sensing elements may be placed either in each link to control the appropriate

joint, or between the manipulator and the hand. In each case, a matrix calculation

must be performed to relate joint forces to hand forces, or vice versa. By locating

the force sensors in the links, a simple analog servo loop can exist between link

and joint. By locating the sensors at the hand, the effects of link inertia can be

eliminated because the force measurement is made between the arm and the hand.

If we could exert forces at the hand, then, by bringing the arm to bear on

some elastic material and by varying the force, we could achieve very fine motions.

Such a mode of operation, coupled with the ability to detect small changes in position

or velocity, would make many fine compliant tasks possible with low precision

manipulators.

VIII. Computer Requirements

Computing requirements are split into two systems: training and execution.

A training system is normally highly interactive, has no real-time requirements

other than good operator response, aand is used infrequently. Such systems can be

written in high-level languages and run on large computers under time sharing. They

range from very simple to highly complex. A simple system records manipulator

positions and has some elementary editing and program branching abilities. A large,

complex system relies on a symbolic data base to interpret input statement|, such as "FIT enginehead ONTO engineblock" to generate entire manipulator programs.

Execution programs also vary from simple to complex. A simple program outputs

only set points to a hardware servo; a complex program performs transformation,

processes sensory input data, and makes control decisions. Execution programs have

severe real-time requirements, are usually written in- machine language, and use

limited amounts of memory.

As the execution program must be run every time the task is performed and

the training program only once, considerable effort is devoted to precomputing during

the training phase in order to reduce the complexity, size, and rate of computation

79
of the execution program. Such precomputation efforts are to some extent contradictory.

For example, to precompute all alternative courses of execution in response to some test, results in a simpler, shorter execution program, but a program that has more

data and is larger than one in which the alternative courses of execution are computed

as required.

As task variability increases, more and more computation must be performed

during execution and less during training. The training phase then consists of providing

the necessary task description and relevant data to the execution program in an appropriate form.

Execution programs are in effect software servo systems, even where hardware

servos exist, as they must perform an effective servo computation in order to interpret

manipulator performance in terms of program execution. Bandwidth is directly related

to sampling frequency of the execution program, as is cost of the execution computer

whose cycle time must decrease also. Even with the advent of cheap minicomputers,

this presents a major problem. One solution to this problem is to provide hardware

servos, but, due to the load and manipulator -configuration-dependent dynamics, this

solution is not simple.

As manipulation programs tend to be a mass of detail relating to any given task,

compilation, or automatic programming techniques, would seem appropriate to the correct

generation of such programs. Such techniques rely heavily on a symbolic data base,

which at present must be input by hand but which will become available with the

development of CAD/cam systems. Currently, a problem exists in the lack of a high-level

language in which to describe multimode, complaint, servo tasks. The major drawback

of such high-level systems is the difficulty of inputting direct experience to the

system in order to modify the manipulator program. Programming tends to be performed

in the front office, not in the factory where the direct experience of the problem

exists.

Another approach to generating manipulator programs is to develop task-oriented

systems in which the program understands the task gnd can meaningfully interpret

signals, both during training and later execution. Such an approach, although lacking

the apparent generality of the high-level system, will provide real systems to perform

real tasks out of which the foundation for more general-purpose systems can be

securely laid.

IX. Manipulator Specifications

The kinematic design of the manipulator should be evaluated in terms of its

modification from the human arm. Evaluation should start with the human arm and then

consider each successive modification, evaluating its effects, changes, and limitations

at each stage until the proposed . design is reached. In this manner, the effects on generality of additional or fewer degrees of freedom, prismatic joints, and different

arm geometry can be ascertained.

Each link, starting with the link immediately before the hand and working back

toward the shoulder or base, should be evaluated for structural strength and deflection,

resonant frequency, and strength-to-weight ratio. The weight of the link includes all

actuators, sensors, and instrumentation. As each successive link is evaluated, all

links out to the hand are included as part of the link under consideration.

80
The ratio of maximum torque to minimum or free torque is a key parameter. The

links must be compliant, either naturally or by some torque servo loop. If a torque

servo loop is used, then its speed of response must also be evaluated. No backlash

should exist, as any backlash or hysteresis at a detectable level markedly degrades

manipulator performance. Joint motion should exhibit no cogging from gears, commutation,

or other factors.

Each joint should have a high bandwidth torque servo in which output torque

is linearly controlled. Each joint should also have a high bandwidth velocity servo.

In either mode, torque, velocity, and position must be accessible to the computer.

Position servoing can be a software servo loop in conjunction with the velocity servo.

If the hand or tool has sensory signals available for local control, these signals

should also be available to the computer for task algorithm execution and decisionmaking.

X. Conclusion

We have an excellent prototype of a general-purpose manipulator in the form of

the human arm.

The basic differences between current manipulators and the arm are compliance

and control. While the computer appears to be capable of solving the control problem,

if provided with all sensory input signals, current manipulators do not exhibit any

compliance at all.

A manipulator with torque- servoed joints would have the necessary compliance.

REFERENCES

1. Antal K, Bejczy, "Remote Manipulator Systems, Technology Review, and Planetary

Operation Requirements" JPL 760-77 (July 1, 1972).

2. Robert Bolles and Richard Paul, "The Use of Sensory Feedback in a Programmable

Assembly System," Stanford Artificial Intelligence Laboratory, Memo AIM-220

(October 1973).

3. Richard Paul, "Modelling, Trajectory Calculation and Servoing of a Computer

Controlled Arm," Stanford Artificial Intelligence Laboratory, Memo AIM-177

(November 1972).

4. Raphael Finkel, et al., "AL, A Programming System for Automation," Stanford

Artificial Intelligence Laboratory, Memo AIM- 243 (November 1974).

5. C.A. Rosen and D. Nitzan, "Some Developments in Programmable Automation," SRI

Technical Note 100 (January 1975).

81

5.1.5

MANIPULATOR SYSTEM PERFORMANCE EVALUATION!

PROBLEMS AND APPROACHES

Nicholas L, Shields, Jr. Thomas B* Malone

Mark Kirkpatrick

Essex Corporation

Huntsville Facility

11309-E South Memorial Parkway

Huntsville, Alabama 35803

Essex Corporation

201 North Fairfax Street

Alexandria, Virginia 22314

I» Introduction

IDuring the past four years, Essex researchers have been actively seeking some answers to critical questions related to the National Aeronautics and Space Administration

(NASA) Earth Orbital Teleoperator System (EOTS). In a graduated program of experimental

investigations each major subsystem of EOTS is being evaluated. The research approaches

have dealt most particularly with measures of system and subsystem performance in remote

manipulator tasks where the human operator is the principal mode of system control.

While manipulator performance evaluation in teleoperators must of necessity

address human performance as an evaluation item, the other system components remain

very similar to those in programmable systems. Indeed, it has been pointed out that

the only significant system feature which differentiates robots and teleoperators

is the presence of autonomous control for the robot, versus the operator- in-the-control

loop for the teleoperator. Several significant problem areas will be discussed and a review will be made of workable approaches to those problem areas taken by Essex

researchers. It is felt that the on-going efforts to develop an effective and reliable

evaluation program for teleoperators should complement those same efforts being carried

out in programmable robotics.

II. Problem Statement

As is true for any system evaluation, a manipulator system evaluation program

must address two distinct considerations! (1) what to evaluate, and (2) how to

evaluate it. Thus, an evaluation program is primarily concerned with measures (the

what) and methods (the how). Each of these two separate considerations has its unique

problems.

The problems usually encountered in selection of evaluation measures concern

questions of evaluation general izability, standardization of measures, and applicability

of measurements.

83
The degree of evaluation generalizability is the extent to which the measures

employed are appropriate to a wide range of manipulator systems, task requirements, and

operational conditions. The evaluation approach having some minimum degree of

generalizability is one which is developed for a specific manipulator, a particular task,

or a unique set of conditions. However, even a specific evaluation approach has some inherent generalizability due to a basic commonality which presumably exists among

manipulator systems. All manipulator systems contain the same classes of subsystems!

structures, actuators, sensors, control system, and end effectors. All manipulator

systems perform the same basic functions, which are:

. Position and orient the end effector at the worksite

Maintain the position and orientation of the end effector

. Move the end effector in three-dimensional space

. Apply forces and torques at the end effector

. Detect and avoid obstacles

. Perform work at the worksite using the end effector, which includes grasp,

release and other manipulations of external objects.

It must be borne in mind that we are concerned here with a generally applicable

manipulator evaluation approach, and not with general purpose manipulator systems as such. The generally applicable evaluation program should be equally appropriate for

assessing both general purpose and special purpose manipulator systems.

The development and validation of generally applicable measures of manipulator

performance is a requirement for a number of reasons. For one, different manipulator

systems can only be compared with one another when they have been evaluated on tasks

involving general performance measures. Secondly, the availability of validated

generalizable evaluation measures relieves the system developer of the task of

developing and validating measures specific to his system. Finally, a set of generally

applicable measures provides the personnel responsible for an evaluation with

guidance on what must be evaluated.

These requirements for generally applicable measures are closely related to the

requirements for standardized measures. Standardization impacts the degree to which

evaluations share identical measures and tasks, and it adds an element of control to

the generalizable measures. Without standardized measures the comparison of the

results of different manipulator system evaluations is virtually impossible beyond a qualitative description of differences. Standardization of measures also demands

standardization of methods selected to obtain data on the specific measures. With such

standardization, communication among personnel in the manipulator community will be

greatly enhanced, since all will be speaking in terms of a common language.

Some of the difficulties experienced with evaluation of manipulator system

performance can be traced to using an adequate performance evaluation approach for

inappropriate purposes. There are evaluation programs more sensitive to certain

attributes of one manipulator system than others, and if we, as users, ignore this we

do a disservice to the evaluation program and to any subsequent decision concerning that

manipulator system. Malone (1973) has suggested that performance evaluations generally

accomplish the following items:

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. Engineering feasibility of a concept - can it be made to function?

. Operational feasibility of a concept - will it function as desired?

. Environmental feasibility of a concept - will it function in the environments

to which it will be subjected?

. Identification of problems of specific designs

. Providing the basis for candidate concept selection

. Providing information for future design criteria

It is not proposed that any one evaluation program accomplishes all items, or that any one item can be appropriately evaluated with all available performance

evaluation programs.

The inappropriate application of specific performance evaluations or the inappropriate conclusions drawn from performance evaluations are two types of problems

which could be solved with a standard approach to performance evaluation. Standardized

evaluations could be classified by functional area if necessary, i.e., engineering

feasibility, specific design problems, and hopefully would be useful with all types of

manipulator systems by functional area. Even without such functional classifications,

a single acceptable evaluation instrument would permit more appropriate and comparable

conclusions to be drawn from the data while testing across all functional areas - operational, environmental, engineering, feasibility, etc.

In an investigation of the problems associated with evaluation methods it is

important to establish the overall objective of the methods. The evaluation methods

are implemented to maximize the degree of reliability and validity of the acquired data.

Data reliability is a derived measure of the consistency or repeatability of the

acquired data. Reliability varies as a function of the degree of error in the test

results. High reliability indicates that the variance in performance noted in

experimenter evaluations is true variance and therefore enables predictions of the limits

of system performance capability in the operational environment. There are generally

two types of error which can affect data reliability: sampling error and experimental

error. Sampling error refers to biases inherent in the data due to inappropriate

selection of subjects, systems, or test conditions. Experimental error applies to

spurious effects due to uncontrolled events or conditions.

The degree of success in predicting behavior in the operational environment

is a function of the extent to which the empirical investigations reflect the type of

tasks to be performed in the real world. The degree to which an evaluation program

measures what it purports to measure, the degree to which it reflects the operational

environment, is the validity of the measure. Validity varies as a function of fidelity

of the experimental conditions to the real world situation and requires that test

conditions be representative of the range of conditions expected in the real world.

While validity can really only be assured by comparing test performance with performance

in the real world situation, it can be approximated by correlating results of different

evaluation programs.

85
The overall control applied within an evaluation will enhance the general

acceptance of a performance measure by specifying the conditions under which the measure was taken, the levels of those conditions, the conditions under which the

findings are valid and recording the conditions which must be reproduced in order to

retest the hypothesis covering the initial findings. These several outcomes are derived from test control and ensure a degree of reliability with respect to the

findings.

One of the major sources of sampling error in manipulator system evaluation

programs involves the element of "system conviction". System conviction refers to the

tendency to develop an evaluation procedure with a particular manipulator system as

a model or to emphasize one class of systems over others (anthropomorphic manipulators

versus non-anthropomorphic, special purpose versus general purpose, operator-in-the-loop

versus automatic control). System conviction is really experimenter bias in a functional

sense, but with a tone of vested interest. The elimination of system conviction from

evaluation programs and statements of performance capability for manipulator systems

is necessary prior to the development of an acceptable evaluation system scheme.

Presently, when this bias has not been eliminated, it clearly needs to be recognized

for its influence upon performance findings. This is not to suggest that all evaluation

programs are biased in one way or another; it does suggest that lacking a generally

acceptable evaluation program with demonstrated reliability it is prudent to examine

not only the data, but the method behind the data. Quite often manipulator systems

are designed to meet specific requirements for a particular task or situation. Data

from an evaluation approach that examined how well that particular system performed

on a specified task for which it was designed would have to be viewed somewhat

differently than data taken on a general performance or "aptitude" type of examination.

Another source of sampling error in manipulator evaluations has been the inability

of performance evaluations to discriminate relatively small differences within classes

of manipulator systems while discriminating larger differences between classes of

systems. Performance criteria would, in the best of all possible worlds, indicate the

best of several candidate systems, say, anthropomorphic systems, as well as indicating

the relative differences between anthropomorphic and non-anthropomorphic manipulator

systems.

Making the instrument as broad or as general as possible also helps to eliminate

sampling bias which may tend to favor one or another system. While both the potential

for a reduction of evaluation bias and the broad applicability among different

manipulator systems tend to indicate that a general type of performance evaluation

measure is preferable, one serious drawback is apparent. This is the possible insensitivity of the evaluation measures to detect small differences, as a consequence of

employing gross measures of manipulator performance, and the relatively gross measure

might not then be meaningful in the operational, decision-making environments where

finer discriminations are required as a function of economics, task requirements and

similar specific constraints.

In order to reduce evaluation insensitivity one may develop evaluation criteria

for each manipulator system which test that system to each of its engineering and

performance limits. An especially designed, tailored evaluation is certainly the most

sensitive type of testing - one designed to fully evaluate the unique system. This

approach which runs counter to general izability is appropriate where the performance

86
of only one manipulator is in question. Difficulties may arise when attempts are made

to compare findings with dissimilar systems. This comes about when comparable measures

are not being taken, or when measures which can be compared are taken in different

ways under differing circumstances. Individually designing test instruments for

manipulator systems is also an expensive way to proceed when more than one system is to

be evaluated.

While evaluation bias, insensitivity , limited utility and inappropriate application

may not seem to be the most severe problems which must be dealt with in the development

of acceptable performance evaluation programs, they constitute the most persistent. When

the first small inquiries were made into subsystems performance of the EOTS, these were

some of the first questions dealt with and continue to be the stimuli for enthusiastic

debate over four years later.

A final problem area which warrants attention pertains to the degree of experimental

error in the evaluation results. During test sequences it is not at all uncommon for

system parameters to be slightly altered out of necessity, and the interaction of a number of these changes often significantly impacts the manipulator system performance

without apparent reason. Engineering models of manipulator system are often used in

concept feasibility and verification and due to the prototype nature of these manipulators,

they require frequent maintenance and repair, sometimes repair or replacement with newer

subsystems. When using programs and programmable systems, new instructions, new decks,

even a new programmer may have subtle effects which are measurable (but not altogether

explained) when they interact with other variables.

It is critical in any evaluation system to maintain the strictest of all possible

controls over any variables which may have an effect on the test outcome. These

variables not only need to be controlled, but the levels at which they are set need to

be specified. It is assumed that not every variable which may affect the outcome of a performance evaluation is going to be recognized or necessarily identified, but a complete examination of the environment and system needs to be made to detect as many

control variables as possible prior to testing.

The immediate outcome rigorous control will have on data obtained in empirical

evaluations is to reduce the degree of experimental error thereby ensuring maximum

reliability of the data.

III. Approaches

What procedures and programs can be used with a wide range of manipulators and

still yield discriminating information? What approaches can be taken to reduce

experimenter bias, or system conviction? What means are there to insure the appropriate

application of evaluation instruments in investigating system performance? To what

extent is it necessary to record changes and list control variables in reporting all

performance measures?

It is suggested here that some approaches taken by Essex researchers in the

evaluation of non-programmed or program-assisted, operator-in-the-loop manipulator

systems might be of more general utility and apply to evaluation problems associated with

programmed robots and manipulators.

87
To that end of increasing the overall utility or the degree of generalizibility

of performance measures, it was determined that several appropriate f igures-of-merit

derived from dependent measures taken on specific tasks might yield information which

would allow comparisons among similar and dissimilar manipulator systems which were

capable of performing the specified task. A series of task modules was designed to measure tip positioning accuracy, minimum position change, tip orientation, and force

and torque application. It is assumed that these tasks can be accomplished with virtually

any manipulator system and are relatively free from bias in terms of particular

manipulator systems. As an example of deriving f igures-of-merit, the minimum position

change requires that the manipulator tip be moved from the center of a one foot square,

smooth surfaced module, to a target disc on the module surface, which is a fixed distance

away from the center of the module. The target discs to which the manipulator is . commanded vary in diameter, thereby varying the accuracy requirements of the task. The

amount of time to accomplish the move and the accuracy of the movement can be given

as one type of figure-of -merit, and utilizing information developed by Fitts and Posner

(1967) for manual operations, a f igure-of-merit can be derived which considers accuracy

and time simultaneously. Fitts determined empirically that the mean movement time for

hand movements was a logatdthmic function of the ratio of movement amplitude (a) to

tolerance (w) of final positioning. Utilizing information theory Fitts derived:

ID = log2

Where ID is the index of difficulty measuring the relative accuracy required by

a particular movement which influences the time necessary to complete the movement.

Fitts' Law is one f igure-of-merit which has been found to correlate with data

in manipulator performance evaluation (Kirkpatrick, et al, 1975). The tip positioning

task module requires that a tip position be maintained by the system for a specified

period of time. By using contact discs, the frequency and amplitudes of excursions

from that commanded position can be studied. This might indicate control instability,

inadequate braking, whatever, but it provides a measured basis on which to compare

many systems.

The measures taken on the task modules are readily taken on any manipulator

system and can be taken with a degree of accuracy to permit fine discriminations

between two very similar systems. Rather than develop a test approach which exacerbates

the problems of general utility and discriminating sensitivity, the Essex approach

was to examine very general types of manipulator system behavior in a test situation

and permit the sensitivity of the dependent measures and derived f igures-of-merit

to discriminate between manipulator systems.

The problems created by experimenter bias, while not always apparent, can most

satisfactorily be controlled by a rigorous experimental method. This is one other

important reason for control of experimental variables. It reduces the influences of

experimenter bias at best, and at the least, specifies the conditions and levels under

which any possibly biased data were acquired. The relation between bias and

experimental control is complementary in that bias can be reduced or identified with

rigorous controls, or it can be amplified with loose or no significant experimental

controls.

2A

W

88
The approach most frequently taken by Essex researchers in controlling the effects

of bias is to go to the experimental or testing situation only after clearly and

specifically identifying the test objectives. A written test plan and procedure is

prepared prior to actual conduct of any test and this test plan is reviewed by the

research team. This allows everyone to make comments and suggest changes before time

and effort av^e expended in any inadequate data collection. It also permits a hard copy

document on which to record any change if it becomes necessary to vary any level of any

condition in the test program. The requirement for a prepared written document prior

to data collection has been a very helpful one during the extended test program. It has been instrumental in assuring test consistency during such influential occurences

as staff and personnel changes, customer changes and requirements, equipment changes,

and management changes which could otherwise ruin a well thought out test and evaluation

program.

Malone (1973) has prepared a listing of steps which need to be taken to maximize

the effectiveness of an evaluation program and which help to control problems associated

with experimenter bias or failure to control influencing variables:

. Clearly and concisely identify test objectives

. Assess system performance requirements associated with functions

to be evaluated

. Establish evaluation criteria

- parameters to be investigated

- range of conditions to be sampled

. Specify the minimal levels of fidelity of the experimental situation

to the real world situation, and identify the effects of failure

to meet these levels

. Identify conditions to be systematically varied and controlled

(independent variables) and those to be only controlled (control

variables)

. Assess effects of failure to apply rigid control over all conditions

. Identify performance measures (dependent variables) to be evaluated

. Develop specifications for mockups, software, procedures, and

experimental control

. Identify methods of acquiring data on performance measures and on experimental conditions during the test

. Identify statistical analyses to be used to assess system performance

in terms of performance measures and as a function of experimental

conditions

. Develop a checklist for assessing degree of control and fidelity of the

experimental situation once mockups, equations of motion, procedures,

etc., are completed and implemented prior to testing

89
IV. Summary

From an experimental standpoint, the most recurrent problems, and at times the

most difficult with which to deal, include the choice of representative tasks, the way

in which testing is accomplished, and the application of the findings. More often than

any other problems, these have been addressed to the extent that it can be presumed

they represent general concerns within the evaluation process.

It may be too much to expect that any one evaluation program is going to be able

to accommodate the problems of general izability, standardization, system conviction,

appropriate control, test sensitivity, and test applicability. It is not, however,

beyond reason to expect that some significant difficulties which are shared in

manipulator system evaluation programs can be reduced by a stringent methodology,

generally applied by evaluation teams.

REFERENCES

Fitts, P.M. The information capacity of the human motor system in controlling the

amplitude of movement. J. Exp. Pschol ., 1954, 48, 483-492.

Kirkpatrick, M. , Shields, N.L. Jr., Frederick, P.N., and Brye, R.G. Earth Orbital

Teleoperator Manipulator System Evaluation Program, Essex Corporation, Alexandria

Virginia under contract NAS8-30545, February 1975.

Kirkpatrick, M. , Shields, N.L. Jr., Malone, T.B., Frederick, P.N., and Brye, R.G.

Manipulator System Performance Measurement. Paper presented to the Second

Conference on Remotely Manned Systems, July 1975.

Malone, T.B. Remote Manipulator System Evaluation Criteria, Essex Corporation,

Alexandria, Virginia, March 1973.

Malone, T.B., Kirkpatrick, M., and Shields, N.L. Jr. Manipulator System Man-Machine

Interface Evaluation Program, Essex Corporation, Alexandria, Virginia, under

contract NAS8-28298, January 1974.

90
5.1.6

RESEARCH ON REMOTE MANIPULATION AT NASA/AMES RESEARCH CENTER

i

j William L. Verplank

! Stanford University

j Stanford, CA

I

' At Ames, facilities have been developed to explore human performance in computeraugmented remote manipulation. The facilities include the Ames Arm (Vykukal, 1973) with

a "master -brace" which the human operator can wear to command slave-arm position through

DC servos. There is no force- feedback to the master. Joint positions (both master and

slave) are monitored by and positions (of the slave) can be commanded by computer

(IBM 1800 with A/D and D/A converters).

I Under a grant to Stanford University (NASA Grant NGR-05-020345) , supervised by

f, W. Verplank, two doctoral students have used the Ames facility.

I. Augmentation and Detailed Analysis of Peg-in -Hole

Dou;;las McGovern has completed a dissertation entitled: "Factors affecting control

allocation for augmented remote manipulation." The abstract is appended. The special

form of augmentation considered (switching control back and forth between human and

computer) is proposed for space applications where time delay is significant and the

human operator would be available (continually monitoring) to resume (reassume) control

from the computer. One task (peg-pick-up) and one augmentation scheme ("GROPE": using

two touch sensors on fingers to automatically center jaw on peg) were considered,

(Hill, 1973.)

Of significance to performance evaluation are several aspects of McGovern 's work:

1. Using two different manipulators, McGovern applied Fitts' index of

difficulty (see Fig. 1) (Fitts, 1954, 1964) to two tasks, "pick-up-peg" and "put-pegin-hole", varying distance (A) and tolerance (B-C) . Roughly, completion times are equivalent for the two tasks; tasks of the same difficulty (I,) take the same length of

time, and average completion time (T ) is proportional to difficulty (I^) • The same relationships were shown to hold for the two manipulators (Ames and SRI-Rancho) and for

the unencumbered hand (see Fig. 2), The proportionality of time and difficulty (with

different slopes for different systems) supports the notion of using the ratio of

completion times (manipulator vs. hand) as a key performance measure. At least, the

ratio seems to be constant over a range of task difficulties, McGovern found one

ratio for two different tasks and a different ratio for each manipulator system;

Pesch (same workshop) uses the same ratio of completion times to compare systems, but

found different ratios for different tasks, requiring a variety of tasks for manipulator

comparisons. This seems an appropriate outcome. The interesting thing from McGovern '

s

work is finding that there are two tasks with the same ratio and that the ratio is

constant over a range of task difficulties.

91
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92
2, Predetermined time systems (e.g. MTM) also seem an appropriate methodology

for extension to manipulators. Detailed analysis of recordings of position vs. time

indicate that the peg-in-hole task can be divided into two phases as in MTM: "reach"

and "position". The "reach" phase is from start to within 1.5 cm of the hole. "Reach"

j time is linearly related (fig. 3) to distance and independent on final tolerance.

I "Position" time is independent of distance and best modelled as a linear function of

the logarithm of the tolerance. (Fig. 4)

3. Two methods of predicting the effect of automating a portion of the task

("GROPE") were explored. One method, using Fitts' law, takes the automatic subroutine

' as reducing the difficulty of the task as seen by the human operator. The second uses

the two phases and takes the automatic subroutine as replacing one phase ("position")

.

The latter is most direct and does not rely on extrapolating Fitts' Law to very low index

of difficulty. No data were available to compare the prediction with actual performance

using the automatic subroutine.

II. Rate Control with Time-Delay

A second doctoral dissertation using the Ames facilities is nearing completion.

Greg Starr is examining rate control and position control with time delay. It is

suggested that rate control may be advantageous (better than position control) with

time-delay or in the situation of trading control with automatic subroutines. There

are several important aspects of this work.

1. Ferrell's result for position control extends to rate control; that is, since

the human operator uses a move-and-wait strategy, task completion time can be predicted

from a simple model of "open-loop" positioning accuracy,

2. The MIT (Draper Lab's) 6 d.f. control stick is being used and resolved-motionrate-control (Whitney) is being extended to the 7 d.f. Ames Arm. The tasks used by

Mullen (MIT) will be used at Ames.

III. Vision Systems

Head-Mounted Stereo TV and Predictor

James L. Jones, of Ames, has implemented stereo television with a helmet -mounted

display and head-aimed camera. In addition, he has developed high-speed hardware for

edge detection and line-construction to compute range information directly from the

video signals. Such a system connected to a computer-graphics display can provide

enhanced views for the human operator (for example, rotated), or might be used in robot

applications where the machine responds directly to the scene without human intervention.

Another area of on-going display development of potential value in remote

manipulation with time-delay is a predictor. The current implementation uses the Evans and Sutherland LDS-1 display to compute a picture of the slave-arm from the

joint angles on the master-brace. This computation is simplified considerably by the

hardware matrix-multipliers of the E & S computer because the arm coordinates can be

represented as successive multiplications of 4 x 4 matrices, one for each joint. The

picture computed from the current position of the master -brace is superimposed on the

delayed television picture of the slave-arm, providing direct display of the "future"

position of the arm.

93
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94
REFERENCES

Ferrell, W.R. , "Remote Manipulation with Transmission Delay," IEEE Trans, on Human

Factors in Electronics , vol, HFE - 6, Sept. 1965, 24-32.

Fitts, P.M., "The Information Capacity of the Human Motor System in Controlling the

Amplitude of Movement," J . Exp. Psychol ., vol. 47, June 1954, 381-91.

Fitts, P.M. and Peterson, J.R. , "Information Capacity of Discrete Motor Responses,"

J. Exp. Psychol. , vol. 67, 1964, 103-12.

Hill, J.W. , and Sword, A.J., " Studies to Design and Develop Improved Remote Manipulation

System , Stanford Research Institute, Menlo Park, California, NASA - CR - 2238, 1973.

Vykukal, H.D. , King, R.F. , and Vallotton, W.C. , "An Anthropomorphic Master-Slave

Manipulator System," in Heer, E., ed.. Remotely Manned Systems - Exploration and

Operation in Space , California Institute of Technology, 1973.

APPENDIX

"Factors Effecting Control Allocation for Augmented Remote Manipulation" by Douglas

E. McGovern, Ph.D. dissertation, Design Division, Department of Mechanical Engineering,

Stanford University, 1974,

Abstract

This thesis develops a method for predicting the effectiveness of an augmented

remote manipulator system. Such a system represents the combination of a manipulator

with a human operator and a small computer. Both the human and the computer have the

capability for generating commands to control the manipulator.

The performance of the integrated man-machine system can be predicted through the

combination of manual control data with a model of the augmentation scheme. This

involves the description of human behavior in a form which allows comparisons of the

time required by the human to perform a task with and without augmentation.

A set of experiments was conducted to generate the necessary human performance

data. Results are reported for a simple positioning task performed using two different

manipulator systems under manual control.

Two levels of task description are used in the discussion of the experimental

results. The first deals with the entire positioning task. The time required to complete the task is described by several models, including Fitts' index of difficulty,

relating the distance moved to the final tolerance.

The second type of task description breaks the task into two phases, as determined by the performance of the operator. The time to complete these phases is

expressed in models based on either the distance moved or on the final tolerance of the

task.

Results from these experiments are used to investigate some aspects of task

description and manipulator rating as well as establishing the form of human performance.

The end result of this thesis is to demonstrate how the experimentally derived

manual control data can be used to predict the performance of an augmented remote

manipulator system. A number of examples of augmentation are discussed and one is

modeled in sufficient detail to illustrate the effect of various factors on the

overall results. It is seen that such things as the type of human performance, the

exact nature of the computer subroutine used in the augmentation, and the speed of the

manipulator are all instrumental in determining whether augmentation decreases the

time to perform a task. qr

5.1.7

EXPERIENCE AND REMARKS ON MANIPULATOR EVALUATION

J. Vertut

Coromissariat de 1 ' Energie Atomique

France

This experience was based on the force reflecting (master slave) manipulators

widely used in nuclear research. My remarks then reached to unilateral arms in various

applications, then our experience is now getting improved by v7ork on bilateral servo arms

and manipulator programming.

I. Basic Factors to Be Considered in Evaluation of Manipulator

1 . Mechanical Characteristics

They are observed as classical mechanical measurements.

A first set is

solid friction (force to start a motion)

visquous friction (more important in servo)

deflection

backlash

inertia as applied to the manipulator terminal

balance

Remarks : The same characteristics can be considered for evaluation of a total system^ or for mechanics and control of an arm or for only the mechanics of an arm.

In the particular case of force-reflecting master-slave these factors are considered between master and slave arm, or reflected to the master (balance, inertia

and friction)

.

In a second set we can identify

maximum load capacity

pay load

duty cycle (payload could depend on duty cycle)

maximum speed

acceleration

frequency response

all three depend on load

A third set is related to combinations between the first and second set through

control characteristics

97
position threshold (minimal possible motions)

minimal speed

precision

repeatability, etc.

Such factors are closer to the later "global" evaluation factors.

In a fourth set we can place reach and coverage which are generally only considered

in addition to some of the second and third set.

Some others also never considered are:

zoning of the coverage (ref, 1). This means the interaction of position of the

terminal with available orientation capabilities of the object)

zoning of maximum force and velocity

zoning of payload and inertia, etc.

Remarks : To qualify a manipulator at least certain evidence can arise that the first set of characteristics might be as homogenous between different DOF as possible to not

disturb their combinations.

It will seem that this leads to many conditions which are close to those found

in computer control: discontinuities of speed or inertia are corresponding to matrix

singularities, and not found when the articulated system is solvable and not redundant.

A certain level of evaluation will appear in the fourth set of characteristics.

It is possible to keep the inertia ellipsoid at the terminal of a manipulator with an excentricity around two in any position. The same is for the maximal load capability

which is represented by parallelpiped and varies with the position of the terminal device.

A very important characteristic which will be emphasized in this note is reversibility.

In case of mechanical reversibility force feedback is obtained via the position

actuator used as force sensor like in mechanical master-slave.

2. Control Characteristic

Manipulator systems are extremely different in performance depending on these

characteristics which are the basis of a manipulator classification; two different

levels can be identified:

a functional level related to the man in the loop^ kinesthetic control or not

a morphological level related to the system, integrated control or not

The following classifications can be submitted:

I

98
(a) Full kinesthetic control (and feedback)

integrated bilateral force reflecting system: an example is the

master-slave arm with man in the loop in real time. Another example can be a timedelay force reflecting manipulator with computer assistance to both master and slave sides.

Close to this example falls an adaptive programmed robot executing a program, but

teached via kinesthetic control. In this particular case global pwedoemance of the man- plus-manipulator system is showing that large distortion is very easily overcome by

the operator without slowing performance (see II. 1), This applies to kinematic lack of

isomorphism as well as non-linear force feedback. Another fully kinesthetic control is

found in vehicle control like aircraft control with force feedback corresponding to speed or acceleration. The same can be considered with a resolved motion rate control

if with force feedback,

(b) Semi-kinesthetic control

It corresponds to a certain loss of easiness for the operator, with a certain loss of time efficiency. This can occur in two ways:

If the loss is morphological we find a semi -integrated force feedback control

like with two or more sticks to control one arm or one vehicle. Systems with these

controls are reversible or bilateral as far as the action on the control handle operates

the slave terminal, and action to the terminal operates the handle.

If the loss is functional we can have integrated position or speed control with

limited or no force feedback, or indirect force feedback (sound visual display, etc.).

Here with the loss of force feedback we lose the bilateral property but keep a comprehensive

control of the number of combined DOF. Here can be placed the resolved motion rate

control as applied now. The control itself is kinesthetic but the feedback is indirect - viewing, etc. , no force or dynamic feedback.

(c) Non-kinesthetic control

Here are push button and individual- stick rate controls with various forms

of non-kinesthetic feedback.

(d) Systems with sensory transfer

Here can be placed viewing display of touching sensors, etc.

II. Global Evaluation Criteria

1 . Remote Manipulators - time efficiency tests

Such tests were carried out some years ago (ref. 2) with all available nuclear

manipulators. The attempt was to get a time efficiency factor between the direct hand

operation and the time used by the same man with a given manipulator. We suggested

four standard tasks, all needing adaptive capabilities to cope with external

conditions (obtained by bilateral control or compliance in open loop)

.

1 - block - on-peg , pick-and-place task (see picture 1)

2 - simple assembly task (see picture 2)

3 - plug test -\ , . ^ „v

, . ., } (see picture 3) 4 - turning valve test -*

99
Fitting 0.5-kg block on pin after lifting-off left pin. Fig, 1 Pick and Place Pins Task

Removing 1 kg block from left side to fit on right pin.

After fitting the pin on left block, remove peg without

Start disassembling by removing lock pin. ^^^-^^ 5. ^^^^ 5 removed. Fig. 2 Assembling Test

1. large hole block 4. fixed block \

2. locking pin 5. movable block

3. 1.27cm peg 6. same as 4 and 5 but with a recess

100
Fig. 3 Turning Valve Test and Electric Plug Test

1. valve with flat knob

2. electric plug

3. rotary lock ring

101
Table I is giving data from that previous work. Our recent work has been extensively

devoted to sharpen our evaluation on tong effect, booting effect and handles effect.

We found different figures than with previous tests for some of the tasks as shown

in Table II. This method is still ineffective to reach absolute figures but it gives

good relative data. We a? so introduced a fatigue test in addition to the previous ones. This test does not include much external constraint. We used this test ten years ago

as liability test for mechanical master-slave arms. The load is fixed as the maximum load

of the manipulator (usually not differentiated from the pay load). This load is made

from lead bricks and the test consists in building it again on a second location 0.5 meter

aside, and back. Here the data given in Table II is obtained from tests executed with

the same manipulator MA 11 (see fig. 4) with the same handle we developed recently but

with different tongs. On the last line are figures with the MA 22 electronic master-slave

(ref. 3) - see fig. 5. Our new type of arm MA 23 (ref, 4) - see fig. 6 - will be

tested the same way soon.

The first column shows liigher figures because of the load which asks for the maximum

squeezing force. Some tongs being slippery also give higher figures. A second reason

is due to carrying the load itself. Figures with MA 22 are similar even with the 1/3

force feedback.

The turning valve test (high column) shows two data. In the first column

are manipulator completion time versus hand time using the same strategy as with the two parallel fingers tong; half turn by half, turning the whole hand. In the second

column, we used the normal procedure hand time, turning with three fingers in opposition.

This shows a strategy factor of 1; 5.

MA 22 is slower in the assembly test because of the backlash which makes it very

difficult to assemble this small pin.

On the valve test MA 22 performance is limited by the maximum velocity in tong

rotation.

Figure 7 shows the fatigue effect data of different handles with the same MA 11 arm in the stacking lead brick wall test. The classical CRL handle uses a natural

squeezing action between two fingers (thumb and index). It gives worst time and fatigue

(done with two hands), this is mostly due to two additive factors: squeezing force is

poor, thus more fatigue; and lifting is difficult because two squeezing fingers are bad

and the three others had to hold the handle.

All other pistol handleswith a trigger squeezing are better because of their

higher squeezing force and because of interactive squeezing and lifting. The best

is our last model PSM 2 because of the best size (PSM 1 is too big hand).

The last curve shows the MA 22 performance, where fatigue appears around three

times later, with 1/3 force feedback. Ma 11 with all pistol handles is capable of

1.5 tons, moved 0.5 meter; MA 22 is capable of 4,5 tongs in Ih 40 minutes before fatigue.

An improvement period is common to all curves.

The same test will be applied now to the MA 23 new arm in programmed mode. It

is expected to reach to a higher speed than by hand, from accelerated playback of a tape

recording made in master-slave mode. This will also be used to test the am liability.

Figure 8 is our previous general chart comprising force reflecting master-slave

and other unilateral modes. This chart will be perfected with future tests. The

large range between real- time^ man-in-the-loop performance versus modes is very

impressive.

102
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103
TABLE II

TONG EFFECT ON TIME EFFICIENCY

: MA 11 :PSM handle

12 lbs

brick wall

IF, times

Pick and

place on pins

Simple

assembly

Plug fitting

Va]

with same strategy

.venatural

hand

strategy

: PEM rubber

: fingers

3,1 2,7 2 2 2,4 3,8

: PEM metal

: fingers

3,2 3 2,4 2 2 ,6 3,9

: SORIGE rubbei 3 ,4 2,4 2 2 2,7 4

: CRL RCD

: rubber

6 2 ,3 1,9 1,8 3 4,5

: SORIGE metal

: fingers

XX 6,9 2,4 2,1 2 ,2 2 ,5 3,8

strategy factor 1,5

: MA 22

: electronic 3 , 15 2,7 2,6 2,1 4,7 7

: CRL

: SRL HD tong

X lack of parallelism of fingers with this load makes lost time when the brick pivots.

This is specific of the tested tong.

XX Fatigue by lack of squeezing force and slippery fingers.

This data is still more relative than absolute, see table I.

104

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106
107

Figure 8

Time -Efficiency Proposed General Chart

1.5 2 _l L

10 20

I

50

100 500

time factor

^. ^^^^^

\

\

\

, RMRC ,

, RC ^OOC,

I 1 I —

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-I h

PP pick and place LD light duty master slave SA simple assembly HD heavy duty bilateral master slave NA normal assembly PC position control-unilateral often called master slave RMRC resolved motion rate control (MIT) OOC on-off control RC rate control

109
2 , Programmed manipulators and manipulators with time delay

Programming (teaching) a programmable manipulator (first generation robot) is

closely like remote handling. Up to now except for a few machines (Trallfa, ref. 4 and 5),

teaching is always carried on by push button mode. It looks to be no problem of time to program but I expect that it will be necessary to teach faster soon. Up to now, performances of a robot are only as given in 1,1. About the close future, a first level

of self -adaptivity can be based on force to position - like it works via man in the

loop using a force reflecting master slave. Evaluation of such ability might be based

on the force errors accepted during the task completion. This error in our servo master

slave (ref, 4) is a figure of 3 to 5% of the payload, and make possible to operate selfadaptive work even on small parts, using manually a reversible manipulator. The work

carried in Draper Laboratory with high accuracy force transducers will certainly bring a very interesting knowledge in that field. Roughly the first level of adaptivity

will provide to cope with position errors up to tong opening size, A next level of selfadaptivity now also in development is related to reaching known objects out of the tong

size clearance by using proximity sensors. To evaluate such systems time performance

versus distance, and maximal distance perception a»"e to be considered. To larger

distances and unknown objects the eye-hand automatic system is needed - evaluation will

follow the development itself.

III. Conclusion

1. Classification - definition

So many manipulators (teleoperators and programmed manipulators) are needing first

to be classified in categories. This is still early development ("robot" Is stilF

not defined) so I prefer to use the other name to develop a language to help developers,

makers and users to communicate.

2. Testing

It is urgent to bring out methods to measure performance and to analyze the

factors reflecting to performance to get standard evaluations by improving exchanges

between specialists.

3. It is also necessary to explore new concepts to evaluate general capabilities

of advancing systems. One concept I would like to propose is transparence: a transparent

teleoperator system between man and any hostile environment makes possible to be in

symbiosis with it, the man doesn't feel the system. This optical analogy is clear

with the force-reflective bilateral manipulator. The fully transparent system does not

bring performance reduction; the time efficiency factor is like the inverse of transmittance.

Another notion is the ability to face unpredictable environments. It is a combination

of versatility (ref. 6) and automaticity , as illustrated in Figure 9.

These notions are not clear up to now, but might lead to measurable figures in the near future.

4. Possible proposal of a standard set of characteristics for a force-reflecting

manipulator system:

friction: i 3 to 57o of payload

-2 deflection :< 2-5 10 m under max. load

110
FIG. 9 TRENDS IN MANIPULATOR PROPERTIES

/

^.4

//

/

Versatility 100 *fc

1. Lifting devices from non-powered to powered

2. Lifting devices to powered open-loop manipulators to position servo manipulators

with sensors but without force feed-back to operator

3. Mechanical master-slave to servo force-reflecting master-slave with sensors

(2nd generation)

4. Unilateral manipulators to specialized manipulators

5. specialized manipulators to remote manned spacecraft

6. 2nd generation force-reflecting manipulator to remote manned spacecraft

7. 2nd generation force-ref lecting'manipulator to 3rd generation (with eye-hand

coordination and pattern recognition

8. regular machine tool to automatic production lines

9. automatic production lines to NC machine tools

10. NC machines to programmed manipulators (1st generation robots)

11. 1st generation programmable manipulators to 2nd generation (position to force adaptivity)

12. 2nd to 3rd generation programmed manipulators (position, force, pattern recognition

adaptivity)

13-14-15. to ideal automatic manipulator (this at last can be called "robot")

111
inertia ^507o payload

pay load ^507o maximum load

duty cycle 1007o at payload

507o at max. load

no load acceleration ^20m,s. (2g)

acceleration with payload ^10 m.s. (g)

_ 2 max. load 1 m.s. ( O.lg)

max. speed 1 m.s. ''"or total range in 1 s

angle between velocity vector and force vector ^2°

-3 -1 minimal speed 10 m.s. or total range in 1000 s -4 -4 minimal displacement 10 m. or 10 total range

-4 backlash 10 m

frequency response 4 to 8 Hz (no load)

2 to 4 Hz (pay load)

All first ones are already possible with the MA 23 system, the last ones are expected. All this proposal is highly subject to revision,

REFERENCES

1. J. Vertut and al, "Analytical Zoning of Manipulator Coverage," Proc, 21st Conference

on Remote Systems Technology, p, 28, 1973.

2. J, Vertut and al, "Contribution to Define a Dexterity Factor for Manipulators"

Proc. 21st Conference on Remote Systems Technology, p. 38.

(1.2, See also J, Vertut and al. First ROMANSY Conference, Udinc, 1973)

3. J, Vertut; C. Flatau, and a.1, "MA 22 Compact Bilateral Servo Master-Slave Manipulator"

Proc. 20th Conference on Remote Systems Technology, 1972, p. 296.

4. J. Vertut, P. Coiffet, "Bilateral Servo Manipulator MA 23, in Direct Mode and Via

Optimized Computer Control," 2nd Remote Manned Systems Conference (to be published),

Los Angeles, 1975.

5. J. Vertut (C.E.A.), P, Moreau (Ateliers et Chantiers de Bretagne) , "Le Robot Alpha I,' on request,

6, J. Guittet, "Robotique Industrielle et Medicale," Bulletin de Liaison de la Recherche

en Informatique et Automatique^ IRIA n 19 - October 1975, on request.

112
5.2.1

PERFORMANCE EVALUATION OF INDUSTRIAL ROBOTS

J.F, Engelberger

Unimation, Inc.

Shelter Rock Lane

Danbury, Conn. 06810

It's just possible that attacking the question of "performance evaluation of

programmable robots" is premature. Robotics is still in its technological infancy

and too much structure early on could stifle healthy growth. There is obviously much

innovation and invention still ahead. Roboticists* thinking should be allowed to soar

for awhile longer before being circumscribed by specifications.

Some newcomers to the field plunge into product development and attempt to make

contributions to the art; others less happily try to synthesize something of value

out of dubious data on feeble early prototype experiments. To date this synthesis

has been counterproductive. Synthesizing projects carried out by SRI and IITRI in

the U.S.A., IPA in Germany and Waseda University in Japan served to mislead would-be

entrants into the industrial robot field as well as to confuse potential users to the

point of frozen inactivity.

There have been something over 200 attempts worldwide to develop products which

their developers wishfully dubbed "robots". The Japanese Industrial Robot Association,

JIRA, and Warnecke and Schraft in "Industrie Roboter" have made the most exhaustive

compilations of projected performance specifications. The data base permitted

extraction of trend information such as:

Drives: 39% pneumatic, 515^ hydraulic, 10% electric

Controls: 575^ against stops, 25% analog, 18^ digital

Also kinematic descriptions showed what articulations different developers

espoused.

So what? Where does this leave the manufacturers who are potential users?

In a more fruitful line of enquiry, IPA examined robot specifications from

the point of view of the working place. However, it is this author's considered

opinion that the analysis failed to be useful largely because of inexperience on the

part of the investigators with the subtleties of the working place. This is the kind

of data better accumulated by roboticists vrtio have struggled with the problem of

replacing a human operator with a robot operator.

By way of example:

At the Third International Symposium on Industrial Robots, Dr. G. Herrmann,

defending the IPA survey, reported that he had found 150 jobs in Daimler Benz that

could be done by relatively simple robots with but 4 articulations and 10 steps of

memory. He was confronted with the observation that there were 11 such "simple" robots

113
on exhibit and asked why these quite inexpensive machines were not being used by Daimler.

He replied, "There seems always to be some facet of the work which needs human attention."

So, the developer who dutifully produces a machine to match the requirements

outlined by IPA is probably heading for disappointment. And, a majority of the 200

or so developers around the world have already tasted that disappointment and abandoned

the field.

A workshop on performance evaluation of programmable robots would probably do

well to ignore most products touted as being robots. These "limited sequence" devices

are really automation components. They may be fine ones indeed and they may be

destined to broad, profitable acceptance? but, they are part of the modular, adjustable

automation field. Robotics is another branch of Automation.

(This is the proper place for introducing a succinct definition of "robot"

but I will demure; I can't define robot, but I know one when I see one.)

With the warning flag raised, it is time to return to the assigned task. Just

how do we evaluate performance of programmable robots, be they exciting or conjectured?

The jumping off point for the president of Unimation, Inc. has to be the Unimate

Industrial Robot.

The Unimate is unabashedly sophisticated and its manufacturer is dedicated to

increasing that sophistication wherever technically and economically feasible.

This is the direction for Robotics.

At this writing there are approximately 1000 Unimates in the field and they have

accumulated over 5,000,000 hours of field experience. With cavalier discounting

of "limited sequence", or "pick and place" devices, I can opine that Unimation Inc.

is the world's only viable robot manufacturer. There is no other builder that

profitably produces a general purpose, programmable industrial robot. (There are,

of course, some interesting and competent designs making tentative entrance into

the marketplace.)

The Unimate had its origins in 1956. It started with the raw idea that a robot

should be useful to industry and that a performance spec should be created against

which design concepts could be evaluated. With much of the naivet* that has been

laid at the doorstep of IPA et al, a group of young engineers studied jobs in all of

the major automotive companies and in a variety of other industries. Figure 1 is a typical data sheet of the time.

A product appeared in 1959 and it finally went to work in 1961. That was the

beginning of a long agonizing refinement of the data base. Every application tried was shot through with surprises. Both product (robot) and application instructions

underwent continual change on the way to a satisfactory fit. Fortunately, the

product specification changes pointed toward a universal product design (hence,

vindication of the company name, Unimation, a contraction of UNIversal AutoMATION).

Unimation Inc. is completely sanguine in defending the concept of a universally

applicable robot over the more widely promoted "limited sequence" devices.

It happens that Unimates are built and bought to a specification; but, it must

be admitted that it takes some imaginative extrapolation to go from that spec to assurance that the robot will be effective in any specific job. Moreover, the spec is

hardly adequate to prove that the machine is sufficiently robotic to be obsolescence

114
CONSOLIDATED CONTROLS CORPORATION

UNIMATION SURVEY DATA SHEET

DATE; ^-/^ -^^6^

OBSERVER M XM>

LOCATION

TYPE OF WORK PERFORMED ;

SEQUENCE OF PRESENT OPERATION :

APPROXIMATE CYCLES PER MINUTE ; ' 'A < on

MAXIMUM NO. OF SEQUENCES ; Horizontal Vertical Rotary

ACCURACY AND MAXIMUM SPEED:

Horizontal Traverse : ^j;/; /^j /o^^

Vertical Traverse: t^>n,

Rotary Traverse: /g^"^. "foyi^^

HAND ACTION REQUIRED :

APPROXIMATE WEIGHT OF PART :

NO. OF OPERATORS :

PROCESS MODIFICATION REQUIRED :

AVAILABLE AREA ;

5/2/56

FIGURE 1 - TYPICAL DATA SHEET

115
proof - that is, versatile enough to succeed in a variety of job assignments.

The gap is filled by application data sheets, films, etc., that demonstrate

the broad capability. Physical characteristics are enumerated in the specification.

"Show and tell* is the method for communicating information on the robot's talents.

Could a more elegant method be devised for evaluating any industrial robot's

performance? Well, it might be useful to think of the robot as an artificial

human being and rate the robot accordingly. One might then generate a resumft comparable to that submitted by human job applicants. Figure 2 is a prototype Job

application form, including appropriate responses of a Unimate.

The more sophisticated robots become, the more likely it is that the resumfe will become a practical means for evaluating performance against potential applications.

Still, there are many who would continue to feel more comfortable thinking of

the industrial robot as a machine. Clear specifications on machine characteristics

then become the evaluation base. For a sophisticated robot, specs would have to be

quite exhaustive to tell the story. The data sheets in "Industrie Roboter" which

show little more than spatial command, number of articulations, kinematics, accuracy,

load rating, and control mode, are so limited as to be almost useless.

Perhaps the most glaring omission in most robot specification sheets is

dynamic data. Usually slew rates and maximum strokes are given for all articulations.

This is of marginal value in estimating how long a particular robot would take to carry

out a specific task. One would like to interrogate the specification as followss

"For each discrete motion required in this task, considering the loads Involved,

and presuming critically damped action, what is the elapsed time?"

It's not easy to create a specification that would be simpler than a complex

multiple input nomograph to provide a reasonably accurate answer. Even though we

in Unimation Inc. recognize the importance of dynamic criteria, we avoid a generic

specification in our product literature. Rather we use trained application engineers

to examine a work station and estimate total cycle time. We also give customers a very crude rule of thumb to make a preliminary appraisal. "For any load less than

rated assume that all steps will average out to 0.8 seconds per step." From experience we have learned that the mix of short and long steps in a typical program will defend

this average.

At this juncture it is proper to report that IPA has recognized the gap in previous

reportage and is suggesting that "point-to-point" time should be made up of th^ree ATs* - acceleration At, deceleration A T, and slew rate AT.

For one robot task, spot welding, Unimation Inc. does provide a more precise

tool for estimating time to carry out a complex task. This is an 18 page document!

It is worth using because it permits very accurate estimating of the number of spot

welds that a Unimate can place while a car body is in station before it. Robots are expensive. Knowing beforehand how many are needed to complete a body in the allotted

time is a key factor in payout analysis.

116
Figure 2 APPLICATION FOR EMPLOYMENT

NAME Unimate 2000B SOCIAL SECURITY NO. None

ADDRESS Shelter Rock Lane, Danbury, Connecticut 06810

AGE 300 hours (by software extension - 5,000,000 hours)

SEX None HEIGHT 5 ft. WEIGHT 2800 lbs.

LIFE EXPECTANCY 40,000 working hours (20 man-shift years)

DEPENDENTS Human employees of Unimation Inc.

NOTIFY IN EMERGENCY Service Mana ger, Unimation Inc. (203/744- 1800)

PHYSICAL LIMITATIONS Deaf, dumb. blind, no tactile sense, one armed

,

immob i 1 e

.

SPECIAL QUALIFICATION Strons(100 lb. load), untiring 24 hours per day

,

learn fast , never forget except on command, no wage increase demands, accurate to 0.05 " through'

out sphere of influence, equable despite abuse.

HISTORY OF ACCIDENTS OR SERIOUS ILLNESS Suffered from Parkinson's

Disease (since corrected), lost hand (since re- placed), lost memory (restored by cassette)

hemorrhaged (sutured and fluid replaced)

POSITION DESIRED Die cast machine operator

OTHER POSITIONS FOR WHICH QUALIFIED Forging press, plastic molding,

spot welding, arc welding, palletizing, machine

loading, conveyor transfer, paint spraying,

Investment casting, heat treatment, etc . SALARY REQUIRED $4.00/hour

RE.LATIVES IN THIS PLANT Five 2000A Unimates in forging departnfcut

LANGUAGES Record-playback, assembly, Fortran

EDUCATION On the job training to journeyman skill level for all

jobs listed above.

REFERENC ES Ccnoral M otors, F ord, Cat erpll ] a r , B n b c o c k V.' i 1 c o >:

.

Xerox an d 65 other major ma nu facturers

117
Using the estimating document, the application engineer is able to consider

"squeeze, weld, and cool" time, robot motion time for adjacent welds, time to make

large motions to new operating zones, time to approach work piece, time to retract

arm from work piece, and the impact of weldgun size and type on these times.

It will not be easy to create a crisp, dynamic performance standard that would

be generically applicable to all industrial robots.

An important philosophical aside comes from one of Unimation's customers. This

customer settled for a rough average of number of spots that could be placed per minute

and then assigned robots at an 80% efficiency factor. When the production line went

on stream, the equivalent of an MTM study was done and the excess robots were pulled

off the line to be assigned elsewhere.

The circumstances above pertain to a production line wherein the single largest

capital investment is in robots. A 20^ variation in number used did not significantly

change the economic attractiveness of the system. And, being robots rather than

special purpose automation, the Unimates could readily be used on other jobs. In the

case where a robot is assigned to an expensive piece of capital equipment, timing can be very critical. A 10^ loss in production when robotized could completely scrub the

application.

The performance specification problem is easily compounded by cataloging other

robot attributes for which one would like to have a quantitative evaluation.

1. Manipulative power - This is approached qualitatively by describing the

number and range of articulations in the robot arm and wrist. But there is application

significance to the coordinate system used, to interaction between articulations, if any, and to space intrusion of the forearm, wrist and end effectors.

2. Programming ease - Complex jobs can consume much high skill progrartming

time. How much is heavily dependent upon programming methods available. Discounting

every method less sophisticated than infinitely adjustable record-playback prograrrening,

there are "joy-stick" operations, computer generated sub-routines, and feedback

assistance to think about. Adding sensory perception further complicates the issue.

3. Interface compatibility - Robots are not "stand alone" machines. They interface with equipment, parts, people, and systems much as do humans. Ideally specificatio

would predict performance in the modern factory environment which would include DNC

equipment, automatic warehousing, group technology and computer-aided manufacturing, etc

4. Reliability - Possibly this factor could be sufficiently covered by

historical evidence of MTBF, meantime between failure, and MTTR, meantime to repair,

for different factory roles. (One gets different figures for forging applications than

for plastic molding applications.)

5. Sensory perception - Do rudimentary eyesight and/or tactile sensing provide

orientation data, recognition data or physical interaction data? What quantitative measures can be applied?

118
6. End effectors - Does a robot have a general purpose end effector (i.e., hand)?

How flexible is it? What dexterity and what range of strength?

7. Mobility - If the robot is not stationary, how is mobility performance

evaluated? Speeds, random walking, umbilical cords, spatial awareness, terrain

capability, etc.

8. Self-diagnosis - "Robot heal thyself." The ability to offer nostrums for

its own performance lapses will be a valued robot attribute. Diagnostic skill will be

hard to quantify.

9. Cost effectiveness - Robot hourly cost versus human hourly cost should be

added to classical standards such as payback, return on investment, and discounted

cash flow.

10. Inherent safety - What confidence factor can be applied to a robot with

respect to each of Asimov's three laws of Robotics?

In the foregoing catalog only some of the stickier issues are enumerated.

There are no problems with power consumption, weight, floor space required, load

capacity, slew rates, reach, memory size, accuracy, interlocks, time delays, random

program selection and such, which already appear in commercial product spec sheets.

One final complication can be added to industrial robot performance evaluation

and that is the matter of the work place. An argument can be made for evaluating

(and changing) the work place as well as the robot.

If the work place is rationalized, the robot performance requirements could be

alleviated. Where parts are oriented in pallets, the robot might forego eyesight,

for example. Thus, Unimation engineers instinctively evaluate work places against the

limited performance available in their current product. Sometimes there's a fit,

sometimes process changes can be recommended, and sometimes we simply throw up our hands in utter dismay.

The industrial robot concept is gaining a grudging acceptance. As this

acceptance mounts, there is every reason to expect the work place to be bent to the

robot qualities available. Meanwhile, roboticists can strain to more closely match

robot attributes to those offered by humans.

A cocked ear at the foregoing finds support for the opening conjecture. It may be too early to solidify robot performance specifications. So much performance

and projected performance is tenuous. There are many wide open performance objectives

to which engineering contributions may be made - even without concise problem

statements. One may literally depend upon "gut" feelings in selecting development

projects.

Tom Sheridan in setting forth the problem statement thinks one of the options

is an "I.Q. Test" for robots. Somehow this has appeal over a machine specification.

Ultimately, the resumfe, sumnarizing available skills, should be the more useful

document to employers who contemplate hiring artificial human workers. The employers

of robots need only higher order performance standards. Roboticists, for their part, can look introspectively for worthy design goals. Robotics is still that far from

its destiny of providing mechanical workers to take over for homo sapiens in the

factory.

119

5.2.2

ROBOTS FOR AUTOMATED PRODUCTION OF CONVENTIONAL AMMUNITION

Douglas A. Morlock

United States Army Materiel Command

Office of the Project Manager for Munitions Production Base

Modernization and Expansion (AMCPM-PBM)

Dover, New Jersey 07801

The Army Materiel Command is currently modernizing and expanding its conventional

munitions production base. Modernization and expansion makes use of modern process

automation and process control technology to complement existing munition production

capabilities for future forecasted potential needs. The scope of the products range

from small fuze parts to large steel forming machines. New technology in chemical

processes for the manufacture of propellants and explosives, load, assemble and pack

items, automated testing, warehousing, inventory control, and also field test-production

traceability is actively sought. Some of the demanding design goals for these new

facilities directly impact on the purpose and objectives of this Workshop. Some time

spent on discussion of these goals will serve as background for further discussion on more

specific areas.

The maximizing of production line availability is of critical importance for obvious

reasons, since the product demand for these facilities is of strategic importance. Most

of the succeeding criteria directly or indirectly relate back to this point. All process

and process control hardware must therefore exhibit strong reliability in order to provide

suitable operation. Closely related to this point is that system operation and component

interaction must be such to assure safe system operation under normal and abnormal

operating conditions. The system safety and process security area contains two major

divisions due to the hazardous atmospheres associated with the munitions production

processes. The propellants and explosives manufacturing buildings and areas for assembly

of these products to their associated metal parts are rated as hazardous and must be

protected as are petrochemical and other similar industries. The protection measures

which must be employed to assure that electrical energy above certain specified levels

cannot exist within these hazardous areas is therefore of prime concern in munitions

production plant design. The use of intrinsic safety hardware and procedures, fluidics,

optics, pneumatics, and hydraulics is therefore being emphasized. The operational

safety aspects implementable within the process and process control design are also

being emphasized.

The minimization of operating staff exposure to the processes, especially in

hazardous areas, is also being emphasized. This goal not only strives to save human

life, but can be traced back to the concern for line availability by minimizing human

decision requirements during abnormal crisis periods. The minimization of human

dependence for tasks which can best be pre-programmed and performed by machine while

not de-humanizing the operator because of a feeling of non- importance and involvement

are considered heavily in systems design. Process and process control systems must

exhibit a certain degree of flexibility in order to incorporate any process improvements

affecting product uniformity or production cost. As with all industry today, we are also

committed to the conservation of natural resources and the minimization of pollution

to our atmosphere and waterways. And of course, all of this must be accomplished with

the minimum capital investment possible.

So far the munitions production business appears similar to many other industries

using process and process control equipment. We have, however, one quite unique problem

not faced by many others. Most industries produce a product having a fairly defined,

uniform demand or demand cycle. Conventional munitions are only required in volume

during a time of conflict or war. However, we cannot build the required production

121
capability at that time for obvious reasons. Therefore, the strategy is to maintain

our production facilities in a state of readiness (layaway), being able to recommission

them upon demand which is usually considered to be within ninety days from notice*

Ehiring this period the stockpile reserves are used in place of the production. This

layaway period is considered to be from five to fifteen years for design purposes.

Leaving the general area to deal with items manufactured and past and future

applications of robotics requires that the functional areas of munitions production

be segregated. These major areas arei metal parts manufacture; load, assemble, and

packing; and warehousing and inventory control. Each of these areas contains several

different categories of application and I will touch on as many of these areas as possible and therefore by necessity will not go into great depth on any of them.

Metal parts manufacture covers the large area from small caliber ammunition

to artillery shells to small fuze parts. Robotics could efficiently be applied to

the packing of small caliber ammunition by transferring the finished product from

the material handling equipment to the shipping boxes. A manipulator could be

used to transfer a sheared, heated billet from a conveyor to a forming machine and

another used to position the drawn shell for machining, while yet another performs

gaging functions on the finished product. The artillery shells in question range

from the 105mm to the 8 inch rounds. The physical data on these items can be found

in munitions handbooks. The gaging and assembly of fuze parts eliminates the

human dependence within the operation, assuring a uniform product.

Plans are currently under consideration for using robots for remote sample

extraction of propellants and explosives within the manufacturing process. In certain areas, on-stream analyzers are being employed for in-process analyses; however, where analyzers are not available, samples must be extracted* in liquid or solid state, and be transported to laboratories for analysis. Applications in the

packing areas where finished products are placed in cans and boxes are also possible.

The loading of explosive into artillery shells involves the melting, pouring,

and controlled cooling of the explosives. Due to the expansion characteristics of

explosives when heated, funnels are placed in the top of the shells to be poured which

are subsequently removed after cooling. These operations are likely candidates for

manipulators. After being poured, shells are X-rayed to detect possible voids

present in the pour. Shells exhibiting these defects must be extracted from the line

and transferred to alternate rework lines. This transfer is a function which could

be performed by a manipulator. The shells then progress to the assembly area where

fuzes or fuze plugs are inserted and the shell is mated to the cartridge case and placed

in boxes to be palletized and warehoused. Certain materials handling functions in

this area could use manipulators.

Efficient automated warehousing would make use of non-stationary robots for

product placement and subsequent shipment by identified lot numbers upon demand.

From this overview, it can be seen that the potential application of robotics

to munitions production is quite broad with some unique design requirements. We are embarking within the MOD/EXP program on a large scale documentation standardization

program to aid in more efficiently identifying systems requirements, more efficiently

specifying those requirements, to better identify costs, and to aid in the re- commissioning from layaway problem. In summary, we are dedicated to using evolving

technology in the accomplishment of our task and desire to include all pertinent

specification guidelines generated as a result of this Workshop into our overall

documentation package. We require continued feedback from industry in order to make

this interface more efficient and thereby enable us to make use of the available

technology.

122
5.2.3

SERVICING OF INDUSTRIAL ROBOTS - THE MODULAR OJNCEPT

Michael S. Konstantlnov

Central Laboratory for Manipulators and Robots

Sofia, Bulgaria

I. Abstract

The problem of on-site servicing of industrial robots lies in the field of

interest of modern automation. Whilst successful use of robots depends on their

positioning accuracy, reliability, ease of servicing and security, measuring of their

performance in terms of reliability versus ease of servicing indicates that there are very good reasons for the development of "modular robots". This paper shows that

the modular design approach is successful and profitable. The new modular robot

system "Matador" is described in detail.

II. Introduction

Whilst the control system design of a programmable robot or manipulator generally

determines its positioning characteristics, it is the mechanical design that principally

dictates its rigidity, load carrying performance and ease of servicing. If the robot

does not operate or its positioning accuracy fails, production is down. Successful

robot users have set up their o»m servicing departments for robots. They stock their

own set of spare parts. But what of the smaller, short run manufacturer that doesn't

have his own trained servicing personnel? He is then dependent on having to send across the country, or around the world for spares. In view of this, it is pertinent

to look at the modular concept in relation to the design of present day robots.

The concept of modular standardized control systems is not new. The technique

is well established in the solid state electronics field, where it is accepted that

ease of servicing and trouble shooting result in favourable economics. In the fluid

control systems such techniques are less well established. Concerning the mechanical

design of a programmable robot or manipulator, there is over the last few years a conflict of opinion between the "modular robot" concept and the "universal robot"

philosophy. Unimation Inc. (and now Unimation Limited) has borne the universal

industrial robot for considerably more than a decade. Today, the battle lines are drawn and both camps have set down their ideas and thoughts, but the long awaited

"boom" is far behind the clouds.

This position paper outlines the author's experience on the subject of measuring

performance of relatively sophisticated robots in terms of reliability and servicing.

The lessons learned indicate the advantages of the modular concept and determine the

rational tradeoffs of a new modular design and assembly system for industrial robots

and all kinds of manipulators.

III. Characteristics and Attributes of Robots

Industrial Robots (IRs) are divided into three categories of increasing

complexity on the basis of capital cost and capabilities . Load, speed, positioning

accuracy, range of motion, dexterity, control quality, program memory capacity and

robot-to-process line control logic are salient operating characteristics that must be

defined as guidelines for the selection of the proper robot system. Consideration

should be given to the intrinsic and to the logged reliability, the ease of its

123
servicing, and the security of such a machine. The best selection of a robot depends

on the combined effort of both designer and user.

1. Positioning Accuracy

This characteristic is closely related with motion speed and handling weight.

Positioning accuracy limits the usage of robots, and this is especially true for machine

assembly «ork. As motion speed and handling weight are also important robot

characteristics, these must be examined simultaneously with the positioning accuracy

ite;m.

2. Reliability

There are two concepts to be considered in an examination of this attribute,

one is "Mean Time Between Failure" (MFBF), and other is "Mean Dovm Time" (MDT). No less an authority than Joe Engelberger, President of Unimation, Inc., envisages a2relationship

between the time interval between failures and the total amount of down time . But

he states that the correlation is not proportional because there is the additional

variable of time of repair. Thus, an otherwise satisfactory MTBF could result in

unacceptable downtime if the time to repair is excessive. According to this roboticist,

industrial experience indicates that for most applications, uptime must exceed 97^ to

satisfy most users of IRs. And, he continues, "this rule of thumb is somewhat dependent

upon the specific application; in a glass manufacturing plant, for instance, there

may be need for uptime of 99.556."

In this connection, the German roboticist, 0. Gengenbach, suggests the correlation

for uptime (in %)

B (mittlere Verfugbarkeit) =» —_______ MTBF + MDT

Two typical examples are givent

Example 1 » To predict the failure rates for all the components in a Unimate,

a USA organization relied upon notebooks which were prepared under U.S. government

contract to aid prediction of reliability of space vehicle systems. For electronics

ccwiponents, the Rome Air Development Center Notebook, TR-67-108, was used and for

mechanical hydraulic components the organization used U.S. Navy's Failure Rate Data

(FARADA) Notebook. Both of these references were cross-correlated with other similar

data banks. Since field experience is crucial to determine true reliability, the

robot was placed in the field and the experience results fed back into a reliability

control system. In the case of one 2000 Series Unimate, the opening experience produced

an MTBF of 145 hours and was slowly brought over the ensuing three years of production

up to 415 hours.

Example 2 « It considers downtime. If we assume that servicing is done by

local service personnel, and that the IRs are working on a two shift basis, and that the

service can always offer next-day help, then the most likely MDT per incident would

be eight hours. Of course, the situation could be more complex.

It is clear from the above considerations and examples that robot reliability

is a very complex issue.

124
3, Ease of Servicing

To evaluate servicing, In general, it is useful to look at past failures and

defects that occured on the robot already built and on other robots of the same model.

Recently an effort has been made at COMSAT Laboratories to classify failures in terms

of reliability. Accordingly, a "design" failure occurs early in life. Its identification

shows that the reliability was not as high as planned. This can result from actual

design or from quality control. A "random" failure may occur at any time. Its occurence

does not change the estimate of the attribute reliability. A "wearout" failure occurs

late in the design life of the robot; it may be actual wearing out. Four types of

failure or defects could be distinguished: reparable, difficult reparable, probably

reparable and no reparable. Thus "reparable" is an estimate of whether a failure is

serviceable. This depends on how much of the robot is built to be serviceable.

Furthermore, failures in electronically programmable robots and manipulators

with hydraulic actuators could be classified in two main groups, (a) part failures only:

electronic/electrical and mechanical/hydraulic. The non-part failures are system

failures due to tolerance build-up, critical interface tolerances, customer abuse,

environmental problems, etc. This type of failure occurs in robot systems at a rate

proportional to the complexity of the system.

Generally servicing is defined as preventive maintenance and repair of equipment.

Given the working conditions, one must consider that on site servicing is cost effective

for long term robot operations when compared either with robot replacement or with

robot removal and assignment of a human operator. Robot servicing on site could be

accomplished either by local service personnel or by the user's trained personnel. So

too, even where training of a user's personnel is minimal, a robot could be "repaired"

through telephone consultation, "remote control" of the personnel.

In fact, the servicing personnel has to perform the following tasks:

- permanently

(a) preventive maintenance

(b) early preventive diagnostics

(c) running repair

- incidentally (when a failure occurs)

(a) arrangements for a clear of purpose servicing

(b) diagnosis of the failure (part or non-part)

(c) part disassembly or elimination of the non-part failure cause, i.e.

environmental hazard (ambient temperature rise, radiant heating, shock,

electrical noise, etc.)

(d) part repair or spare part exchange

(e) part(s) assembly

(f) short service test

(g) disassembling of servicing facilities

Ease of servicing means facilitating the above tasks in order to gain time and

cost. Ease of robot's servicing is closely related with robot design. IR can be

designed so that failed or worn-out parts can be replaced in a few minutes while the

robot remains on site. In addition to cost, such a mode of servicing offers the

possibility of improved service and can improve robot's reliability in both concepts,

KTBF and MDT.

125
4, Security

The necessity of sharing the robot environment with people, as well as other

equipment, forces designers to give more than the usual amount of attention to identifying

potential failures which could "be destructive to people and equipment. Evaluation of

this physical attribute of an already built IR necessitates a step by step structural

analysis of each robot linkage and a kinematical and dynamical analysis of the robot

hardware in terms of some "worst anticipated cas*". These should be followed by

engineering speculations to identify all possible failures or malfunctions in the robot

that could be destructive to people and to equipment. For instance, the multiple

degrees of freedom are a great advantage for the robot versatility and dexterity but

they carry with them an equally great responsibility to reduce the potential for

destruction.

IV. Measuring Performance - Reliability Versus Ease of Servicing

In 1969-70, IRS were introduced on the European market and three years thereafter

a manufacturing company in this country bought such a programmable manipulator. The

type of robot selected, still in the forefront today, was just emerging and gaining

acceptance. It is equipped with 5 degrees of freedom and Is of the relatively

sophisticated universal type, offered as a completely self contained device, well

designed and made. The manufacturer claimed that it was thoroughly tested, with

industrial machine life expectancy, a minimum of maintenance and down time.

In fact, the manufacturing people of this company were not familiar with IRs. Furthermore, local service and local stock of spare parts were not available. Therefore, it was decided to begin with the education of the company people on what an IR

is and how it is to be used and progranvned. The lack of spare parts and of a local

service was also considered and it was not envisaged to put the robot in their production,

at least for a performance test period.

As a first step in bringing the users in direct contact with the robot a so- called "flexible automatic manufacturing cell" was installed. Such a system constitutes

the linking of one numerical controlled machine tool with an industrial robot and

a magazine for workpieces. Thus, a service test was made under simulated conditions

of use.

1, Performance Evaluation

The robot worked on a two shift basis. Generally speaking, MTBF was satisfactory

but resulted in unacceptable downtime. Two "design" mechanical/hydraulic part

failures occured and another electrical/electronics non-part failure, due to ambient

temperature rise, worsened the positioning accuracy during the test period. Whilst

the non-part failure was easily identified and removed by an electronics serviceman

of the same plant, the part failures caused considerable troubles to the manufacturing

people. No spares were available on site and the robot repair turned out to be a complicated issue, despite the fact that the first incident was due to a relatively

simple failure in a hydraulic throttle valve. The operations of diagnosis and

identification, part disassembly, spare part provision, exchange and assembly were

painful and a great deal of time was taken up to this end. The completely selfcontained-device design worsened the situation. The second part failure showed almost

the same picture; the time to repair was also too excessive and both failures resulted

in a higher rate of downtime.

126
In conclusion, the manufacturing engineers and the plant managers stated that

the most serious disadvantages of this robot are: (a) its low reliability; (b) completely

self contained design; and (c) its non-standardized component parts. Finally, it was decided not to install the robot into full production, since it is not easily

serviceable even by skilled personnel.

The lessons learned with this relatively sophisticated robot indicate that there

are very good reasons for the development of modular robots, especially for short run manufacturers who can really benefit from the use of only a few robots.

V. The Modular Robot Concept

Recent efforts in the design and development of modular IR systems have resulted

in some interesting, new and unique designs.

The basic configuration approach adopted groups the standardized sub-systems

into four main modules: the manipulator, the controller, the power pack and the

application gripper. In many cases any, if not all, of these main modules are also

modularized, so that all modules including those of the application gripper and the

sensor modules (if any) are replaceable in the event of malfunction, wearout, or the

availability of an improved version. Studies of the potential economic benefits of

the modular approach have consistently shown lower emergency repair costs and time

and, therefore, a minimization of the MDT. The exchange operations are made on site,

while in a normal repair activity on a sophisticated industrial robot, the whole unit

would be disconnected and moved to a safe distance. It must be emphasized also that the

more sophisticated a robot is, the more important is maintenance and the more skilled

must be the type of mechanic or electrician engaged upon it. Robot repair must

be kept simple! This is particularly true when the robot is installed in a plant where

no high-grade maintenance and servicing personnel is available. A practical approach

is to design the modules so that their removal and exchange can be effected very simply.

The modules can be repaired and re-used, so that additional savings accrue.

The number of modules used in a system is a design variable. Two contradictory

factors operate. Weight minimization is favored by using a few modules. On the other

hand, preventive maintenance on a group of modular robots is favored by using many

modules since each is then replaceable. Mechanical modules can contain parts of

kinematic chains; elemental chains of the manipulator can have the actuator elements

in the module or can have them spread over several modules.

A survey of modular industrial robots identified different system concepts

that exhibited a range of versatility, complexity, and capability to accept a wide

range of workpiece and tool operations characteristics. VERSATRAN (U.K.), MANTA (GFR),

ELECTROLUX - MHU (Sweden/GFR) are a few european examples. The number of robots

offered in modular form in Japan is noticeable. Of the six on show at the International

Industrial and Materials Handling Exhibition in Tokyo (18-23 November, 1974), two,

the Kayaba Industries KMR-2, and the Tokyo Keiki IA2, were hydraulically powered, the

remainder being driven pneumatically.

127
VI, The Matador Concept

Several mechanical IR modular systems are in present use and development as an important part of IRs. The extent of modularization ranges from complete sub-system

autonomy (ROBITUS - Japan) to simple movement modulesi rotary and translatory modules

(MANTA - GFR), Studies led to the conclusion that all known IR modular systems are serviceable, with some weight and volume penalties but with relatively low cost

penalties* affected by the extent of modularization. Positioning accuracy and security

are limited when the extent of modularization is increased. MDT is improved in all cases.

There are two fundamental concepts in robot R&D. In the one, the structure

and all functions and characteristics are compared with real man. On the other ^and,

it is not necessary to think of human beings as the ideal target. The "Matador"

concept was borne by the marriage of both concepts.

Analysis of IR structures and their kinematics (the arms) established in a very

simplified approach two types of joints: R (revolute) and P (prismatic) ones. One

of the stipulations for IR modules states specifically that they shall form an open

multi-link chain, which kinematically connects a moving body to a "fixed" frame.

The mechanical modules require a mechanism which incorporates high operational and

volumetric efficiency plus high reliability. With this requirement as a guide, the

objective is therefore the synthesis of an open modular linkage, used to move a further

member (the gripper or end effector) through many arbitrary positions in the space

(workzone). The basic "Matador" concept is the synthesis of required modules in the

form of linkage elements. Synthesis of binary links for both finitely and inf ihitesimally

separated position problems has previously been extensively studied by Professor B. Roth

of Stanford University. In addition to presenting a new and unified approach to the

modular design and assembly problems in the field of robotics, the "Matador" system

presents an entirely new type of binary link ("dyads"). The new binary links are with revolute (R), prismatic (P) and R-P "half "-joints. Thus, we may regard a R or P joint as the combination of two "half" joints interconnecting their respective dyads.

Thus, following modules (dyads with "half" joints) are definedt l/2 RR module, 1/2 RP module, and 1/2 PP module. The frame link and the output link are 1/2 R or l/2 P modules.

Now, to the mother nature. Analysis of the human arm structure establishes a two-link chain comprising an upper link (upper arm) and a lower link (lower arm),

wrtiich are used to move a member (hand) through a hemispherical workzone. Kinematical

analysis shows that in order to reach the envelope of the hemisphere with the outstretched two-link chain (arm) the upper link requires two degrees of freedom with v

regard to the frame (shoulder). To accomplish contact with the frame by the member

(hand), the links of the chain are of equal length, which requires one degree of

freedom. In such a manner the member could be placed at any point within the

hemisphere (workzone) by a RRR linkage.

In IRs design the arm (regional) linkage just described can be provided with

the following joints' combinations

t

RRR RRP RPR PRR

RPP PRP PPR PPP

Most present-day equipment utilize RRR (spherical coordinates), RPP (cylindrical

coordinates), and PPP (Cartesian coordinates) joints.

As an example, the arm sub-system (regional structure) of an IR working in

cylindrical coordinates comprises a series of l/2 R - 1/2 RP - l/2 PP - l/2 P "Matador"

modules.

128
VII. Conclusions

The development of modular low cost serviceable robotic devices needs a significant amount of engineering effort to better satisfy the needs of the smaller,

short run manufacturer. Performance measurements of specific modular systems should be

made, especially in terms of their physical attributes, such as reliability and ease

I of servicing. International "standardization" efforts will, among others, reduce

I production costs and improve the servicing of industrial robots.

REFERENCES

1. Bryant,. S., Came, E.B. "Some Observations on the Economics of Complex Industrial

Robots", paper No. F2, pp. F2.9-F2.20, Proc. 2nd Conference on Industrial Robot

Technology, Univ. Birmingham, (March 27-29, 1974).

2. Engelberger, J.F. "Three million hours of robot field experience", The Industrial

Robot , Vol. 1, No. 4, June 1974, pp. 164-168.

3. Gengenbach, 0. "Zuverlassigkeit , Instandhaltung, Arbeit ssicherheit". 5 Arbeitstagung

des IPA • Erf ahrungsaustausch Industrieroboter '75, Vortrag Nr. 35.

4. Konstantinov, M.S. "Inertia forces of robots and manipulators", paper presented at the Second Conference on Remotely Manned Systems (June 9-11, 1975), University of

Southern California, Los Angeles, USA.

129

5.2.4

A COMPUTER-AIDED ROBOT OPERATION SYSTEMS DESIGN (Part l)

Yukio Hasegawa (Waseda University)

Ichiro Masaici (KasawaJci Heavy Industries Ltd. ) Masatiiro Iwasawa (Oki Electric Indust3~y Co., Ltd.)

PALS Committee of Japan Industrial Robot Association

ajnd Japan Metal Stamping Association, JAPAN

System Science Institute, Vaseda University

Sh.injuku-ku, Tokyo l60, JAPAN

ABSTRACT

In industrial robot operation systems design, there are many

conditions to be considered such as work pieces, fabricating

machines, dies, peripheral equipments, layout, cycle time,

and so forth. For developing more systematic and logical procedure to design the robot operation systems, we applied a conversational type computer technique and refined the procedxire. It was started fram system elements construction of

metal stamping operations as static state and proceeded of

dynamic characteristics determination of the system. The

paper introduces the outline and the early stage of the reseaxch.

I . INTRODUCTION

In the robot application field, most of the robot operation

systems are designed by robot application engineers. In order

to obtain good results, we need to have good engineers and

methodology. The application technology of the industrial

robot is composed of need ajialysis for the new robotized production system, the selection cind synthetic combination of

hard wares such as fabricating machines, robots, conveyors,

peripheral devices and so forth. Up until today, the robot

application technique has depended on the implicit acciimulation of an engineer's practical experience, and we had no systematically orgsinized technique.

So we need majiy man-hoiirs of proficient engineers for the

robot systems design work. ¥e are anxious that the shortage

of engineering man-power and the high cost of the robot

application soft ware will be a serious bottle neck when we

introduce large numbers of robots into production lines in

the future. For solving the above problems we started a re- search project to develop the computer-aided robot operation

design systems, so-called CAROD (Computer-Aided Robots and

Robot Operation Systems Design). As a practical foundation

to develop the system, we applied metal stamping operations.

Fig. 1 shows the general view of our CAROD system development.

reprinted from Proc. 5th Intl. Symposium on Industrial Robots,

Chicago, Illinois, Sept. 22-24, 1975, pp. 203-213 (with permission)

131
II. OUTLINE OF CAROD

CAROD is composed of two phases. One is the static phase and

the other is the dynamic phase (DP-CAROD) of the system. The

static phase (SP-CAROD) hajidles the layout of the robot

operation systems, the motion pattern of the robots and so forth. The CAROD robot operation systems design is done by

following the procedure shown in Fig. 2.

computer application to the robot operation sygtems design

'il V ^

Develop the new design logic

by computers

Make easy and speedy dea ign work by computers

Introduce the computer simulation

model for developing

1 new robots

^' Rationalization of

t he des ign me thodoloery Improvemen t of the robot development

procedure

t \lr Better robot operation systems design by CAROD

Fig. 1 General view of CAROD development

V CUE—)

Fig. 2 General flow of CAROD

132
In the SP-CAROD, the design result is d.ra\m by a plotter that

is connected with CPU. The design procedure is executed by

conversation form. If a designer thinks that the design

alternative that comes out from the plotter is undesirable,

he can re-design the model by utilizing the local feed-back

loop. After a designer gets a desirable result of SP-CAROD,

he proceeds to DP-CAROD. In DP-CAROD the designer inputs the

results of SP-CAROD and the dynamic characteristics of the . system elements into the CPU an.d generates dynamic characteristics of the integrated robot operation systems.

If the designer thinks the result (dynamic characteristics of

the robot operation systems) is not appropriate, he modifies

d>-namic characteristic of the system elements and re-designs

the DP-CAROD. In this case the designer cannot accept the

result by using the local feed-back loop, and also it is

anticipated that there is some problem in the static phase

design, then he must return to SP-CAROD through the general

feed-back loop. By following the above procedure he can get an elevation and plain figure (projected on the cathod ray

tube) of the system.

The CAROD is also useful for robot selection and development.

For instance, in SP-CAROD, if we caxi make statistic data of

robot operation systems design restrictions, those are to be

used for input into the CPU; then the designer finds statistically the appropriate type of robots for particular conditions .

Ill, . STATIC PHASE CAROD

In SP-CAROD, the designer exchanges conversation with CPU

through the tele-typewriter. Then he chooses an appropriate

robot that has suitable motion patterns. The CPU outputs the

layout drawing through the plotter. ¥e need to classify the

main components and restrictions for forming the robot operation system patterns. For instance, we classified the robots

into eight categories, the two classes by press machine frame

type, diesets into two types by having front guide posts or not

the peripheral devices into two parts by feeding methods, and

the layouts into two patterns by longitudinal and side long

restrictions

.

By combining those patterns we can classify the robot operation

systems into 128 types as shown in Fig. 3. As you see in the

figure, for instance, the robot operation system pattern No .

1

is composed of a multi-armed robot, a C type frame press

machine, a no-front-guide-posts dieset, a continuously fed

type peripheral device, and longitudinal type layout. In

this research, we constringed from 128 to 36 patterns.

IV . DYNAMIC PHASE CAROD

In DP-CAROD, we analize aind inspect the behavior of a robot

operation system by feeding in information about the system

into the CPU as shown in Fig. 4. Ve feed in such information

as SP-CAROD design specifications, dynaanic characteristics of

the robot and the press machine which are used for the operatLon system, and display operating conditions on a cathod ray

tube in the computer system.

133
l i-i:'-^" irobot pattRms

press fnachlr frim- type• layout space

C type stra

stdc

irht

t >pe H

longiludtnal type. side long

•vpe "-.^

double ''arms ^

longitudi- nal type.^

--IT-'-,

side long

type single '

. ' double

b.inds '

longitudl- ml type^

side lon«

type ^

s mflle '

.' single .

h.Tnd type

longitudinal type^

side long

type

•

double

, robots , type $Plongi tud I

- rial type^ »^Side long

type ^ hand

*• chute

type 8f:|f4?

longitudl

-

nal type.

is 5°

side long

type -"^^

double'

^ -phase hand type

longi tud i

-

nal typo. side long

type ejecting

perlphera

1

rlevlce type

longitudl

nal type. side long

type

"Op

tp

V-'

Front Guide Posts

Fig. 3 Classification of robotized

press operations

Fig. 4 General flow of DP-CAROD

Cdi.pur b«h*»ior or tb« \

robot optfrntlon »rmfm I

y... X.. —7

\.r .... ,.b.. .,..../

134
The designer inspects moving pictures in the cathod ray tube

display by referring to the related materials, and determines

appropriate conditions. If the designer considers that dynamic characteristics of the operating system are inadequate

and there is some possibility to change the dynamic characteristics of the robot or the press machine, he again displays

the behavior of the robot operation system.

At the start the designer inputs the dimensional data which

are based on SP-CAROD design result and calculates the co- dominant area. A "co-dominant area" is an over-wrapping area

of robot ajid press machine slide movements, and if matching

movements are inadequate, a crushing accident will be probable in this area. From dynamic characteristics of the robot

and "co-dominant area" dimensions, the designer can calculate

the time that the robot does not intrude into the "co-dominajnt

area". This time is the one when the press machine slide can

intrude into the area without crushing against the robot.

Therefore, the time is called' "possible intrude time of press

machine slide".

Then from the fundamental dyncimic characteristics data of press

machine slide and the dimension of "co-dominant area", the

designer calculates the time when the press machine slide has

to intrude into the area ("necessary time of press machine to

intrude into the co-dominant area"). As shown in Figs. 5 & 6

the designer adjusts the "necessairy press machine slide intrude time" coming at the middle of "possible press machine slide

intinide time" by matching both movements, and determines the

stopping (waiting) time at upper dead-end point of the press

machine

.

From the above data processing work the designer can display

the behavior of the robot operation system. In the case of the

robot development and allied aspects, the analysis of the dynamic characteristics is the most importamt problem. In the

above case we can utilize CAROD as a simulator. For instance,

dynamic characteristics of the robot is limited by characteristics of actuaters and control mechanisms and it also has

particular speed curves as synthesis of the characteristics.

By giving these data to DP-CAROD with other dyneimic characteristics of the robot, the designer can get useful data for

designing and selecting robots in each case.

V. CAROD APPLICATION CASES

Fig. 7 shows aja example of conversations between the designer and the computer system in SP-CAROD. In these Q & A type

conversations, the computer system asks questionnaires through

the typewriter output and lets the designer input simple

answers through the typewriter, too.

In these questions and answers the designer has received the

following instructions.

1) As to drawing scale, there are two choices of

1:25 and 1:50.

2) As to the ^id-dth of the work piece, it must be

shown with the maximum width of raw material

ajad the finished stage.

135
Fig. 5 Co-domina_n.t area of the robot

and press machine

o-E

Is

> A

s u

right arm

for unload lag

movement in movement in movement in

" co-dominant area"! "dis co-doml nant area" "^co-dominant area*

common movement

for both arms work piece work piece

up ^ right swing ^ down ^ release j ^ loft •wing ^ down ^ grasp

left arm

for loading

movement in movement In movement in ^dis co-donlnant area"

^ "co-do-Tilnant area" j "di » co-dominant area* ^

pos9 Ible press slide

intrude time

necessary

press slide intrude time

poss tbie press slide

Intrude time

1 1 necessary

press slide

intrude Cime

1 1

movement of press machine

movement tn movemonl In movefflvnt In -dis co-domlmmt area" -co-dominant area" "dls co-doalnant ar»a- « —T

, >—r-J *

slide stop at upper slide lower dead slide

up dead point down point up

Fig. 6 An example of time chart

\

1 -^fi
WHAT IS THE SCALE Cr 0M= TO "*«- IN ORA'.VING ? PLEASE '.JRITE "***".

50WHAT IS THE MAX, WIDTH CF THE WORK? "***-Mn.

500 WHAT IS THE CAPACITY OF THE PRESS MACHINE? "***"TO''l. 300

THE FRAME OF THE PRESS MACHINE IS THE " STRAIGHT TYPE ".IS HOT IT?

YETHE FRAME Or THE PRESS MACHINE IS THE "STRAIGHT TYPE

IS THE ORAUIMG OPERATION MORE IMPORTANT THAN THE OTHER OPERATIONS?

NO

THE WORK ATTACHS TO THE LOVER DIE. DOES NOT IT?

YETHE WORK ATTACHS TO THE LOWER DIE. IS IT ADMITTED TO DESTROY THE ORIENTATION Or THE UORX?

NO

IS THE TYPE OF THE ROaOT DETERMINED?

NO

IS THE CYCLE TIME MORE IMPORTANT THAN THE COST?

YE"CAM THE R030T TRANSFER THE V.ORK TO THE MEXT STAGE DIRECTLY?

YE"M'JLTt ARMS ROTARY TYPE R330T"IS USEOiIS -lOT IT?

"MULTI ARMS ROTARY TYPE R030T"IS USED.

THE MATERIAL IS FEEDED CONTINUOUSLY TO THE SYSTEM. IS NOT IT?

YE"CONVEYSR-PCSI TIONER SYSTEM'IS USED. IS NOT IT?

YE"COMVEYOR-POSI TIONER SYSTEM"IS USED.

531Fig. 7 An example of SP-CAROD conversation

«xjt HORIZONTAL LAYOUT ««« N0.S31 11/50)

WTO mn:t* le.i

anir.tm iuti

'srSO n^CH'NE . JTRMOiI 510E

300 ION

«ca3T . THf irxi! am; nar'.ar ti»f dCBOT Fig. 8 An example of SP-CAROD layout

draiving made by the plotter

137
3) As to the capacity of the press machine, the

designer has to calculate the tonnage of the

machine in advance.

4) As to the frame type of the machine, there are

two choices: "C" type and "straight side" type.

5) In the case of the "C" type frame machine, the

existence of hazards such as front guide posts

and tie rods ajid so forth influence motion patterns

of the robots.

6) ¥hen there is no guide post in front of the dies,

the computer asks the above type of fabrication

by asking the importance to think of the drawing

operation. Because in the case of the no drawing

process, the possibility of the finished work

pieces sticking on lower die is very great.

7) As to the possibility of destroying the orientation

of the work, if we do not need to keep the

orientation, we can simplify the unloading

operation by using low-cost devices.

8) As to the type of the robot, the designer is asked

only to answer whether he has already decided on

the selection of the robot or not.

9) As to the relationship of the investment cost

and the operation speeds the author is only

asked to answer by the word "yes" or "no".

10) As to transferring work pieces from the robot

to the next stage, the condition is expressed

by using the word "yes" or "no". If the designer

answers "no" , he needs two robots to one operation for loading and imloading.

11) As to the robot type some alternatives are proposed to the designer based on the former

conversation. Then the designer makes the

decision about the robot type selection.

12) As to the raw materials feed type, there are

two possibilities: continuous or batch.

13) As to the use of the feeder, there are two

types of answers: "yes" or "no".

14) As to the layout restriction, the answer is

limited to one or two: longitudinal or side

long to the production line.

15) Finally, the computer system automatically selects

the most suitable system pattern by pattern

number and output layout drawing through the plotter.

Fig. 8 is a system pattern example selected through the above

mentioned conversation of the designer and the computer system.

In DP-CAROD based on the design result of SP-CARODj the computer

system displayed the output of dynamic conditions the designer

determines the dynamic characteristics of the robot and the press

machines

.

138
VI . CONCLUSION

In this research., the authors could accomplish the rdlowing

targets

:

1) To develop a logical procediire of designing a robot

operation system by using the computer systems, and

optimization of the design result.

2) To develop a simulation model by using the computer

system and making dynamic analysis of the robot

operation systems. Also, to generate the data for

future robot development.

3) To introduce the computer systems into robot operation

systems design, and to save engineering man-power ajid

also the application engineering cost of industrial

robots

.

For the above targets the authors developed SP- and DP-CARODs

.

But it is just on the starting line based on metal stamping,

operations. The field to be applied is yet narrow and we shall have to refine the technology and spread the application

field of the technique.

ACKNOWLEDGEMENT

This research has been done based on a research project called

"Pressing and Allied Operations Labour Saving & Safety Promotion Project." The project was sponsored by Japan Industrial

Robot Association and Japan Metal Stamping Association, and

received financial aids from MITI. The actual research work

was done at the System Science Institute of Vaseda University

londer the management of PALS committee, while the several

working members from both associations stayed at the institute.

Also we would like to express our hearty thanks to the

Industrial Safety Research Laboratory of Bureau of Labor

and Mechanical Engineering Laboratory of MITI, who gave advice

and facilities' conveniences, ajid to the members of the above

committee and associations who encouraged and gave advice.

REFERENCES

1. Y. Hasegawa (PALS Committee), Industrial Robot Application

Models Design for Labour Saving and Safety Promotion in

Press Operation, Proceedings of kth. International

Symposium on Industrial Robots, 197^

2. Y. Hasegawa, An Approach to Industrial Robot Application

Research, Proceedings of 2nd International Symposium on Industrial Robots, 1972

3. Japan Industrial Robot Association, The Report on Research

Project of Industrial Robot Application Models Design for

Labour Saving and Safety Promotion in Press Operation,

197^

139

5.3.1

CHARACTERISTICS AND EVALUATION

OF

"MASTER-SLAVE MANIPULATORS"

Demetrius G. Jelatis

Central Research Laboratories, Inc.

Red Wing, Minnesota 55066

I. Introduction

The author and his organization have been involved for about 25 years in the design

and fabrication of a class of remote handling devices known as "Master-Slave Manipulators".

Based on the seminal developments in the late forties and early fifties of Ray Goertz

and the Remote Control Engineering Division, directed by Harvard L. Hull, of the Argonne

National Laboratory, some six to seven thousand of these devices are currently in use throughout the world. Most of them are used in shielded "hot cells" for handling radioactive materials. Details and surveys of their design, characteristics, and applications

(both achieved and proposed) have been presented at technical conferences and in numerous

reports and publications. The basic attributes of these "Master-Slave" devices which

have made them indispensable in the nuclear field, serving as effective extensions of

a human operator's hands and arms into a hostile environment have been variously described:

by Goertz (l) as "Force-reflection"; by Johnsen and Corliss (2) as "Spatial correspondence"

and "Sensory correspondence"; and by Jelatis (3) as "Naturalness, Feel, and Compliance".*

Yet, in spite of widespread successful use and extensive literature, these basic masterslave attributes are not only unknown to many equipment designers and potential users,

but are often unappreciated by users and even denigrated by designers who may feel that

the all-too-obvious increases in cost and complexity will outweigh the less readily

quantifiable benefits of improved performance.

It therefore seems desirable to look at what it is that sets "master-slave"

manipulators apart from other manipulators and programmable robots, as a prelude to

a discussion of the evaluation of their performance.

II. What is a "Master-Slave" Manipulator?

Master-slave manipulators are:

general purpose mechanical devices, used by a human operator in a normal environment, to extend his

hand and arm manipulative capacity into a more-or-less remote

hostile environment with the aid of direct (or indirect)

visual observation , with movements characterized by

naturalness , to obviate the need for extensive training,

feel , to reflect the elastic characteristics of task

objects and forces exerted on them,

and compliance to follow task-constrained paths or orientations at substantial misalignments with

operator-applied forces.

To the extent that" a master-slave manipulator approaches the nirvana of perfection, it

sheds the mundane mechanical burdens of infertial mass, friction, elastic deflection.

141
and finite strength; it becomes invisible and impalpable to the operator whose hand

is thus magically transported into the remote hostile environment.

It is in this spirit that the poet-pilot, Antoine de Saint Exupery, described

the airplane as "The Tool" with which a pilot works in his "Wind, Sand and Stars",

written about 35 years ago:

".... Startling as it is that all visible evidence of invention should

have been refined out of this instrument and that there should be

delivered to us an object as natural as a pebble polished by the waves,

it is equally wonderful that he who uses this instrument should be able

to forget that it is a machine.

There was a time when a flyer sat at the centre of a complicated

work. Flight set us factory problems. The indicators that oscillated

on the instrument panel warned us of a thousand dangers. But in the

machine of today we forget that motors are whirring: the motor,

finally, has come to fulfill its function, which is to whirr as a heart

beats—and we give no thought to the beating of our heart. Thus,

precisely because it is perfect the machine dissembles its own existence instead of forcing itself upon our notice."

Ideally, then, the master-slave manipulator, as an extension of the human hand,

should be used not as the tool itself, but as the hand which holds and euides the

tool: not to weigh an object directly, but to place it on a balance pan and

manipulate the controls; not to turn a nut, but to hold a wrench or impact driver and

apply it to the nut; not as a pry-bar, but to apply and operate a pry-bar; not to drive

a nail, but to hold and swing the hammer; not as a crane, but to apply the hook and

guide the work; not as a stored-program machine to do a repetitive job (except in very

unusual cases), but as a maintenance and intervention device to repair or assist a malfunctioning automatic machine. This ideal, of course, is seldom attainable. A masterslave manipulator is often the only accessible general-purpose tool in a critical

facility and in an emergency may be abused in undreamed-of-ways.

A wide variety of mechanically-coupled master-slave manipulators have been

designed as real-life approximations to the ideal based on various trade-offs and

compromises with economic and performance constraints. A number of these are described

in Ref. (2) and in a 1970 survey by Jelatis (4). To overcome the constraint of direct

mechanical coupling, electric servo-motors and position transducers at widely-separable

master and slave arms connected only by multi-conductor cables were first introduced

by Goertz and his group at Argonne National Laboratory (5). This work and other

comparable developments are also described in considerable detail in Ref. (2) and in

the published proceedings of two 1964 seminars on Remotely Operated Special Equipment

(6) and (7). The last Argonne Development, the "ANL Mark E4A Electric Master-Slave

Manipulator" is described in Ref. (8). A commercial version of this device has been

manufacturer by Central Research Laboratories, Inc., designated as their Model M

Electric Servo Master-Slave Manipulator. A computer-controlled Model M with independent

Master and Slave power supplies, coupled only by a two-way 10 KHz digital data link,

has been built and demonstrated at the American Nuclear Society exhibit in Washington,

D.C., in November, 1974.

As to potential applications and problems, the author is happy to stand pat

with his 1970 speculations (Ref. 4).

142
III. Performance Evaluation

Armed with this brief historical and definitional diversion, we return to the

main program. It is of course a truism to state that everything we need to know

about performance evaluation is implicit in the initial defining paragraph of the

preceding section: since a perfect master-slave manipulator is invisible and

impalpable, the measure of perfection is simply unobtrusiveness . Anything that

obtrudes on the operator's consciousness and veils the sense of "presence" of the

master hand in the slave environment can be ranked or graded and scored against the

device being evaluated. The "best" manipulator is obviously the one with the fewest

black marks against it. Alas! This obvious and simple evaluation method has at least

three flaws; we can ask: what is the task that the manipulator is expected to perform?

how do we grade the degree of obtrusiveness? what is the role of the human operator?

To some extent we can idealize the situation, abstract what we can identify as relevant

characteristics, and construct a "model" conforming more-or-less to the real world,

then derive numbers describing our abstraction. But we must be on guard lest we deceive ourselves into believing that our abstract model can tell us "the whole truth,

and nothing but the truth" without verification by experience which, except for

adequate statistical data on a sufficiently large population exposed to carefully

controlled conditions, may be exceedingly hard to come by.

This problem of performance evaluation is of course not unique to the manipulators under consideration, but is instead characteristic of a "small" population

of any complex mechanical device used for a variety of non-standardized tasks, in

highly variable conditions, by a variety of operators. Here is a closely analogous

situation in the field of aviation: (excerpt from The Aviation Consumer , Nov., 1972,

article "Who Says Your Airplane is Airworthy?").

" The Quantity of Quality

Much of the testing that goes on with a new airplane is qualitative.

This means that it depends on such things as feel, experience, sixth

sense, or what have you, of the person making the test. The test

pilot, particularly, has to make an abundance of qualitative decisions.

Only part of the tests he makes can be measured in quantitative

parameters — i.e., numbers. Assessing the handling qualities of an airplane is axiomatically a qualitative judgement. Likewise, some of

the limitations of the airplane require qualitative assessments.

Test pilots also have to judge the airworthiness of certain qualities

of an airplane in terms of the capabilities of the pilots who will be

flying it. Understandably, such a judgement is wide open to all sorts

of varieties of opinions."

The subjects of performance criteria and performance evaluation have been

discussed at considerable length by the author in a 1962 paper (9) (included with

the NBS Workshop Paper) and need not be repeated. We should, however, look into the

specific questions illustrating the flaws in our initial method of assessing

"obtrusiveness". First, what is the task the manipulator is expected to perform?

This calls attention to one aspect of performance evaluation that may not be

immediately obvious: the suitability of the manipulator for its intended task. This

is discussed in detail in Ref. (9), p. 158, under Load Ratings ; the uncertainties

associated with an absolute numerical load rating are discussed and some arguments

advanced for the alternative concept of adaptability or suitability to function based

on a comparison with the evolutionary process of development of common hand tools.

However, the value of numerical data of adequate statistical significance in guiding

the design and improvement of individual mechanical elements is emphasized.

143
The second question, how do we grade the degree of obtrusiveness?, is also dealt

with in great detail in Ref. (9), in the section headed " Responsiveness" , starting at the bottom of p. 159. The mechanical transfer function of an idealized three-parameter

model, characterized by a lumped inertia, deflection, and friction, is considered

adequate for describing the usual deliberate actions carried out by master-slave

manipulators. Practical methods of measuring these parameters are described, and the

diagnostic value of a mechanical hysteresis-curve, obtained by plotting displacement

vs. an applied cyclic load is pointed out. These are, in fact, objective parameters

that are useful not only for quality-control acceptance tests, but also (in simplified

forms) for routine performance evaluation to determine need for maintenance and to

evaluate the results of maintenance operations after repairs, etc.

The third question, regarding the role of the human operator, brings us back to the difficult subjective realm and is also briefly discussed in Ref. (9). Considerable

work has been done on various factors affecting task performance, and comparing the

times required by direct manual contact, under various lighting conditions, use of aural

cues to determine contact, etc. Although statistically significant data may be obtained

under carefully controlled conditions, the choice of test procedure can greatly bias

the results for or against a particular manipulator configuration. Indeed, it is

possible to select a task that can be easily accomplished by a manipulator (A) and

nearly impossible with manipulator (B), and another task that can completely reverse

this ranking.

The advent of high quality servo-coupled master-slave manipulators presents the

interesting capability of carrying out a standardized task with a single manipulator

and various operators while varying the parameters of the mechanical transfer function.

Thus the effects of controlled amounts of friction, backlash, inertia, springiness,

etc. on standardized tasks could be useful in establishing acceptable limits for various

"obtrusive" parameters. One dramatic demonstration of the value of force feedback is

easily achieved by cutting off the power which provides the reaction forces of the

"master" handle to the operator of an electric servo manipulator. This experience too

is fearfully portrayed by Exupery in the chapter of "Wind, Sand and Stars" entitled

"The Elements" in which he describes a flight along the Atlantic seaboard of the

Patagonian Argentine. He has been spat out to sea sixty feet above the waves and five

miles from shore by a cyclonic gust and is fighting his way back to shore into the

gale with a plane that has a top speed of 150 miles per hour:

"One has a pair of hands and they obey. How are one's orders

transmitted to one's hands?

I had made a discovery that horrified me: my hands were numb.

^4y hands were dead. They sent me no message. Probably they had been

numb a long time and I had not noticed it. The pity was that I had

noticed it, had raised the question. That was serious.

Lashed by the wind, the wings of the plane had been dragging and

jerking at the cables by which they were controlled from the wheel, and

the wheel in my hands had not ceased jerking a single second. I had

been gripping the wheel with all my might for forty minutes, fearful

lest the strain snap the cables. So desperate had been my grip that

now I could not feel my hands.

What a discovery! My hands were not my own. I looked at them

and decided to lift a finger: it obeyed me. I looked away and issued

144
the same order: now I could not feel whether the finger had obeyed

or not. No message had reached me. I thought: "Suppose my hands were to open: how would I know it?" I swung my head round and

looked again: my hands were still locked round the wheel. Nevertheless,

I was afraid "

After an hour and twenty minutes, still five miles out, he had managed to climb

to 900 feet, and in another hour made the five miles to shore and finally reached

his destination, where, he concludes:

"I came away with little booty indeed, with no more than this

meager discovery, this contribution: How can one tell an act of the will

from a simple image when there is no transmission of sensation?"

To those who doubt the value of force reflection in manipulation, one can do

little better than to echo Exupery: "How, indeed?"

IV. Conclusion

A functional definition of a "Master-Slave Manipulator" is presented and evidence

adduced for the value of its special attributes of NATURALNESS resulting from a design

configuration providing substantial positional and motional corresDondence between the

master handle and the slave tong, FEEL resulting from the use of low-friction lowinertia and high performance bilateral coupling elements, and COMPLIANCE to follow paths

of operation or orientational constraints imposed by the slave environment, even though

forces applied by the operator to the master handle may be grossly misaligned with

the slave constraints. The importance of sensory feedback has been emphasized.

Numerical ratings of LOAD CAPACITY were shown to be rather tenuously based and subjective;

the equally subjective suitability or adaptability to intended function are deemed to

be generally more valid indicators of capacity. The easily-quantifiable mechanical

transfer function of a simplified three-parameter model utilizing lumped inertia,

friction, and deflection (preferably as a hysteresis loop responding to cyclic applied

forces) is presented as an excellent objective evaluation and diagnostic tool.

Comparisons of times to accomplish "standard" tasks are described as too subjective

(especially in task selection) to be of much value except under strictly controlled

and standardized conditions with careful planning to validate statistical reliability.

Suggestions are made for procedures to seek correlations between "performance" of

properly-planned standard tasks by electric-servo master-slave manipulators and

intentional measured alterations of the mechanical transfer function parameters; resulting

"sensitivity" functions for different types of degradation would be useful in costbenefit analyses.

Finally, an important evaluation tool not heretofore mentioned is the "application

feedback" from users who invariably find flaws undreamed of by the designers and who

may also quite often make suggestions for improvements. Both of these are helpful in

guiding the evolutionary development of retro-f ittable modifications or even new models.

145
REFERENCES

lo R.C. Goertz, "Fundamentals of General-Purpose Remote Manipulators", Nucleonics , Vol. 10, No. 11, pp. 36-42 (November, 1952).

2. Edwin G. Johnsen and William R. Corliss, "Teleoperators and Human Augmentation",

NASA SP-5047, Washington, D.C., December, 1967. U.S. Govt. Printing Office

(LC Cat. Card No. 67-62098).

3. D.G. Jelatis, "Design Criteria for Heavy-Duty Master-Slave Manipulator",

Proceedings of Seventh Hot Laboratory and Equipment Conference, Cleveland, Ohio,

April 7-9, 1959, (American Nuclear Society).

4. D.G. Jelatis, "Where Do We Go From Here with Master-Slave Manipulators?",

Proceedings of 18th Conference on Remote Systems Technology, 1970, (American

Nuclear Society).

5. R.C. Goertz and W.M. Thompson, "Electronically Controlled Manipulator", Nucleonics , Vol. 12, No. 11, pp. 46-47 (November, 1954).

6. Edwin G. Johnsen, Seminar Chairman, "Proceedings of the 1964 Seminars on Remotely

Operated Special Equipment", Vol. I, CONF - 640508, AEC Hqtrs., Germantown, MD,

May 26-27, 1964.

7. Ibid, Vol. II, CONF - 641120, Jackass Flats, Nev., Nov. 4-5, 1964.

8. R. Goertz, J. Crimson, C. Potts, D. Mingesz, and G. Forster, "ANL Mark E4A

Electric Master-Slave Manipulator", Proceedings 14th Conf. on Remote Systems

Technology, 1966, (American Nuclear Society).

9. D.G. Jelatis, L.W, Haaker, and R. A. Olsen, "A Rugged-Duty Man-Capacity MasterSlave Manipulator", 10th Hot Lab Proceedings, Nov. 1962, (American Nuclear Society).

146
5.3.2

DESIOJ AND PERFORMANCE REQUIREMENTS

FOR

FUEL RECYCLE MANIPULATION SYSTEMS*

J.G* Grundmann

Oak Ridge National Laboratory

Oak Ridge, Tennessee 37830

I. Introduction

Remote material-handling and maintenance techniques have been investigated and

remote systems successfully developed over the past 25 years. These systems rely on mechanical master-slave manipulators for replacement of human arms and hands to carry

out tasks in radioactive environments. The human hand equivalent is the slave hand

(called "tong"). This tong is remotely controlled by steel tape drives through

shielded walls (Fig. 1). Although the main feedback to the operator of the manipulator

is visual, force feedback through the cable drives gives a sense of "feel" to the

master arm and aids in determining the location of the tong for grasping objects.

The operations in a hot cell can be seen through a radiation attenuating window

(several feet thick) that is in the wall of the hot cell. Systems such as the one shown in Fig. 1 have worked well for remote execution of research tasks, but speed of

execution is limited by the rate at which an operator can complete a task. Typically,

such units can be operated at about 0.1 the speed of a person performing the same task without such mechanical aid. Although this low rate of operation may be

satisfactory in research cells, it is unacceptably slow for tasks related to remote

work in production cells which support the reactor-fuel recycle processes. For the

latter work, new remote handling systems are needed that have greater mobility, faster

speed, and better operator visual feedback. Such systems are not commercially

available and must be developed.

SLAVE

MASTER

Fig. 1. A research facility mechanical master-slave manipulator

(courtesy of ANL^).

* Research sponsored by the Energy Research and Development Administration under

contract with the Union Carbide Corporation.

147
In this paper we will first discuss some basic areas where development is

necessary to improve remote handling systems, then describe an example of an improved

production manipulator system, and finally consider some remote handling syste*

performance and construction standards. All of the standards are tentative, and

expect their modification as new development experience is evaluated.

II. Basic Development Necessary to Upgrade Remote Handling Systems

1. Mobile Manipulators

Compared with research equipment, production equipment requires more space to

handle the high throughput rates of a reactor fuel-recycle process. Thus, the floor

area in production cells must be larger than in research cells. To operate a manipulator over large floor areas, it is necessary to provide manipulator moveniMtt

to any location in a production cell area.

Mobility is available in many commercial forms. Typical mobile manipulator

arms are shown in Figs. 2-4. The nuclear industry has used all these types, but the

bridge-mounted, overhead system is preferred because it allows utilization of tht

entire floor space in a cell for production equipment. Furthermore, even on equipmentcrowded hot-cell floors, the overhead manipulator usually can be lowered into position

Fig. 2. Manipulator mounted on a vehicle which rides on rails or treads.^

Fig. 4. Wall-boom mounted manipulator.

Fig. 3. Manipulator mounted

overhead on a bridge carriagehoist. ^ 148
to do the work. Wall-boom manipulators also do not require cell floor space, but they

carry less weight per dollar invested and lack the ability of the overhead manipulator

to reach all equipment on a crowded floor.

2. Master-slave control

The mechanical master-slave manipulator (Fig. 1), with force feedback (is

bilateral), has demonstrated its excellent dexterity and is a model of performance for

future manipulators. ^Sgveral mobile, electric, bilateral master-slave manipulators

have been constructed ' (Fig. 5), but none are designed for use in production cells

without being modified (Sect. 3.2).

Mobile electric prototype manipulators are needed for development of production

fuel-recycle facilities. These new units need (as minimum performance requirements)

a sense of feel and dexterous master-slave control.

Fig. 5. Typical mobile, electric, bilateral master-slave manipulator

(A modified ANL illustration^).

149
3, TV Viewing

To manually operate a manipulator, the operator must have a clear view of the

tong and its movements. Tests indicate that master-slave manipulators can perform

very delicate tastes when the operator can see close-up what he is doing. (Even

threading a needle has been done.^) In most research hot cells« the operations are viewed through shielded windows (several feet of window thickness plus clearance for

the swing of master and slave arms). For this arrangement, the minimum viewing

distance is about 183 cm (6ft). At this distance, tasks with tolerance less than

0.32 cm (l/8 in.) are difficult because of inadequate visibility.

A television camera with a zoom lens inside a cell can enable an operator outside

the cell to observe the work from an apparent distance of only a few inches. Although

depth perception has been insufficient in the past, new stereo television systems, with

two cameras that view at different angles and three-dimensional (3D) TV systems are available. The 3D-TV systems have been improved rapidly, and one systgm now gives closeup images that are so accurate that it is used to perform eye surgery.

Uise of TV viewing for hot-cell work is increasing, and its advantages are being

realized in production hot cells with equipment -crowded floors. Without TV systems

in such cells, some equipment cannot be seen by the operator through the fixed, shielded

windows, and other equipment may be visible, but only at a distance. To enable remote

maintenance by manipulators to crowded and distant hot cell equipment, mobile closeup vision must be available. TV systems are most practicable for this purpose.

4. Minicomputer control for increased speed of operations

7 Minicomputer control of manipulator systems will be necessary for production

processing. Miniccmiputers can be used in at least five ways* all of which will

effectively increase the speed at which manipulator tasks (which support production

and maintenance operations) can be completed.

(a) production i to increase the speed of routine material transfers during

production processing, automation should be utilized, such as the "industrial robot

teach and playback" technique. By this technique, each repetitive production task

is learned as a point-to-point or as a continuous path trajectory, and then the

"learned" trajectory is played back when needed during plant operation. Since such

automation is faster than an operator's slow movements (slowness is the result of

vision and dexterity limitations), tasks are completed in less time.

(b) manual maintenance s many maintenance tasks in hot cells will be non- routine and nonrepetitive, and these will be accomplished most efficiently when done

manually. Even though manual operation of the manipulators will be utilized for most

maintenance, a minicomputer could decrease the time in which the manual tasks are completed, as explained in the following discussion of four features.

- automatic robot traverse executlont mobile manipulators, cranes, and TV

cameras could be equipped with automatic traverse control. Hence, for manual

maintenance, all necessary equi|»nent could be brought to the maintenance location

automatically and in less time than manual traverse of the equipment would require.

Automatic traverse would be accomplished by defining work stations at all anticipated

in-cell maintenance locations, and then programming the trajectories between the

stations by the robot teach and playback technique. The traverses could be played

back when needed during production operations. ^

150
- automatic TV camera sighting and focusing: considerable time is lost

during manual maintenance operations because the operator must sight and focus the

TV cameras on the work area. A minicomputer could do this much faster by calculating

a camera sighting and focusing vector from information provided by position transducers

on in-cell equipment. Servo loops, mounted on the camera, would "lock" onto the

calculated sighting and focusing vector and control the camera angle and focus.

- automatic robot tool changes: tool changing takes too much time during

manual maintenance operations. With tools mounted in tables at known locations, all

tool changes could be made automatically by the industrial robot teach and playback

technique.

- monitoring in-cell devices for collision avoidance: since production

hot cells will be crowded with process equipment and mobile handling devices

(manipulators, TV cameras, and cranes), the operator will have to work slowly to avoid

errors and collisions. If a minicomputer were available to check for collisions, the

operator could concentrate on his work and accomplish it more rapidly. To avoid

collisions, a minicomputer would have to be on line to monitor the positions of all

in-cell devices, periodically utilize the position data to update device position

vectors, and then compute algorithms to compare the position vectors with stationary

in-cell topography (in storage). If the computer determined that a collision were

impending, it would stop the operations that would result in a collision and would

sound an alarm.

III. Production Fuel-Recycle Manipulator System and Specifications

1. A Prototype Production System

An improved system for refabrication of ;^uel for the High-Temperature GasCooled Reactor (HTGR) has been proposed by ORNL (Fig. 6).

This system has equipment within the hot cell as described in Sect. 2. Briefly, this equipment includes:

- a mobile electric master-slave manipulator with automatic robot, automatic

rapid traverse, and autwnatic collision avoidance capabilities.

- a mobile crane that can be operated manually, with automatic robot, automatic

rapid traverse, and automatic collision avoidance capabilities.

- two mobile TV cameras with automatic sighting and focusing, automatic rapid

traverse, and automatic collision avoidance capabilities.

2. Design standards for manipulators, cranes and TV cameras

The major design standards for HTGR fuel refabrication environments are summarized

as follows:

- All movements should be actuated by electric or pneumatic motors. Hydraulic

fluids are usually not allowed in the hot cell radiation environment.

- All devices in hot cells should be constructed simply and be disassembled

easily. All components should be modular if possible, with easily released connections

to other assemblies.

151
- Reliability of in-cell equipment is of great importance because remote

maintenance is much slower and much more expensive than direct maintenance*

INTERRUPTS

/a M

BC

1 D N

/a 1

B C

y

C

D 0

°/ M /A

B P "/

C U D T

E

8C R

D

BINARY INPUTS

OPERATOR CONTROL

PANEl CAMERA MANUAL

CAMERA MANUAL /

MANIPULATOR MANUAL / CRANE MANUAl /

CABLE IDENTIFICATION SERVO COMMAND BCD POSITION FEEDBACK, COMPUTER COMMAND

MANUAL COMMANDS

6 C 0 E M MASTER COMMANDS

INTERRUPTS EtNARY (SELECT CONTROL) INPUTS VIDEO INPUTS

Fig. 6, An improved, reactor fuel-recycle, remote manipulator system

proposed for HTGR fuel ref abrication.

152
The HTGR fuel recycle process is divided into two stages. The first stage is

called fuel processing and the second stage is called fuel refabrication. Since the

author is involved in the design of manipulator systems for the second stage, comments

made below regarding effects of nuclear particles and radiation upon the proposed

manipulator system (Fig. 6) apply only to the refabrication environment. However, the

I manipulator system could also be used in the first HTGR recycle stage (or any other fuel

j recycle process) if proper materials were selected which could withstand the particular

I nuclear environment involved.

j Radiation levels cannot be accurately determined for hot cells within an HTGR

fuel refabrication plant because the levels will depend on the floor layout, and floor

I layout at this time has not been determined. However, preliminary guesses of "worst

j case" radiation levels are available and they are suitable for manipulator design. We

! estimate that there will be two primary radioactive difficulties within HTGR fuel

refabrication hot cells:

(a) First, there will be alpha particle contamination. Since these particles

have little penetration capability, sealed equipment will not be damaged. However,

if the equipment is not sealed, materials such as rubber and lubricants will deteriorate.

Since alpha particles are also harmful to humans if inhaled or swallowed (some are lethal

in extremely small amounts), the alpha particles must be removed by decontamination

reagents prior to direct maintenance. Decontamination is faster and more effective when

equipment is sealed (water tight) in smooth containers.

(b) Second, there will be gamma radiation. Since gamma radiation is very

penetrating, it often requires lead shielding to reduce the radiation to tolerable

levels. Additional radiation resistance results from the use of special "hardened"

materials which withstand larger radiation dosage than "standard" materials before

deterioration (radiation deteriorates common igsulations, plastics, greases, solid

state electronic devices, optical glass, etc.) . Fortunately, gamma radiation

intensity rapidly decreases as the distance from the source is increased. If in-cell

HTGR manipulator equipment is no closer than 6 in. from a gamma source, the radiation

level will be less than 300 R/hr. Although such a radiation level would deteriorate

most standard devices, it could be tolerated with properly shielded and "hardened"

equipment.

3, Performance standards for electric, bilateral master-slave manipulators

We recoiTBTiend the following performance standards for this class of manipulators:

(a) Six degrees of freedom: three translations at the wrist—reach, lift,

and sweep; and three rotations of the hand at the wrist—twist (roll), tilt (pitch),

and turn (yaw).

(b) The entire manipulator should be mobile on overhead rails for movement to

any location.

(c) The manipulator speeds required for natural action of master-slave control

are: wrist translations of 75 cm/sec and hand rotations of 10 radians/sec.

(d) Most fuel recycle process equipment designers specify a load capacity of

75-100 kg per manipulator arm. (Unfortunately, current commercial electric masterslave manipulators lift only 25 kg.)

(e) c,The accuracy of manipulator jaw positioning under automatic control should

be 0.25 cm.^

(f) The feedback elements should be high reliability synchros or resolvers.

153
4, Performance standards for TV viewing systems

Few current performance standards for TV systems are available. Recently the

picture quality of TV monitors has greatly increased, and remote controls for in-cell cameras have become more convenient. Since these TV equipment improvements have been

rapid, current performance information is sparse.

It would be beneficial to the industry and users if such information were

collected and published as it becomes available. Object recognition is one of the

most significant measures of the merit of a TV viewing system, and object recognition

can best be determined by human factors studies. The Marshall Space Flight Center

(MSFC) has sponsojgd several human factors studies to evaluate various stereo and

3D-TV systems. ' They have several additional studies now in progress.

REFERENCES

1. R.C. Goertz, "Manipulator Systems Development at ANL," Proc. 12th Conf. Remote

Sys. Technol., Amer. Nucl. Soc, Nov. 1964, p. 123.

2. "Advanced Handling and Inspection Systems," Programmed and Remote System

Corporation, St. Paul, Minnesota.

3. R.C. Goertz, J. Crimson, C. Potts, D. Mingesz, and G. Forester, "ANL Mark E4A

Electric Master-Slave Manipulator," Proc. 14th Conf. Remote Sys. Technol., Amer.

Nucl. Soc, Nov. 1966, p. 117.

4. C.R. Flatau, "Compact Servo Master-Slave Manipulator with Optimized Communication

Links," Proc. 17th Conf. Remote Sys. Technol., Amer. Nucl, Soc, Nov. 1969.

5. D.P. Mullen, "An Evaluation of Resolved Motion Rate Control for Remote

Manipulators," M.S. thesis, MIT (Jan. 1973).

6. J.F. Butterfield, "Developrntent of a Surgical Stereo-Video Microscope," SPIE

Seminar No. 7, Aug. 21, 1974, San Diego, California.

7. J.G. Grundmann, "A Proposed Master-Slave and Automated Remote Handling System for

High-Temperature Gas-Cooled Reactor Fuel Refabrication," Proc. 5th Int. Symp.

Industrial Robots, Chicago, Sept. 1975, p. 533.

8. Radiation Effects Symp., vols 1 to 6, sponsored by Air Research and Development

Command, USAF, Lockheed Nuclear Products, Lockheed Aircraft Corporation,

Georgia Div.

9. M. Kirpatrick, T. Malone, and N. Shields, Jr., Earth Orbital Teleoperator Visual

System Evaluation Program, Report 1, Essex Corp., Huntsville, Ala., for Marshall

Space Flight Center (March 1973).

10. M. Kirkpatrick, T. Malone, and N. Shields, Jr., Earth Orbital Teleoperator Visual

System Evaluation Program, Report H-4-2, Essex Corp., Huntsville, Ala., for

Marshall Space Flight Center (Jan. 1974),

154
5.3.3

MASTER SLAVE MANIPULATORS AND REMOTE MAINTENANCE

AT THE

OAK RIDGE NATIONAL UBORATORY*

R.G. Jenness & CD. Wicker

Oak Ridge National Laboratory

Oak Ridge, Tennessee 37830

Abstract

The volume of master-slave manipulator maintenance at Oak Ridge National

Laboratory has necessitated the establishment of a repair facility and the organization

of a specially trained group of craftsmen. Emphasis on cell containment requires the use of manipulator boots and the development of precise procedures for accomplishing

the maintenance of 283 installed units. To provide the most economical type of preventive

maintenance, a very satisfactory computer-programmed maintenance system has been

established at the Laboratory.

I, Introduction

Master-slave manipulators were developed because a need arose for a tool that

could operate in hostile environments behind barricades or through shielding walls.

This tool must be capable of making all the manipulations that could be performed

by a human hand. The resulting master-slave manipulators have proven to be a very

useful device for research activities, particularly in the nuclear energy field. Early

handling techniques included tongs, over-the-wall mechanical devices, and other simple

techniques to minimize personnel radiation exposure.

Remotely operated manipulator-type work started at Oak Ridge National Laboratory

in 1953 with the installation of a CRL Model 4 unit in the Solid State Division hot

cells. Since that time, the number of manipulators has increased to 283 (see Table 1).

To provide the necessary maintenance for this number of manipulators, the Laboratory

has developed a specially trained crew of one foreman, eleven millwrights, and one

electrician.

The contents of this paper will be limited to the maintenance history and the

available information used at the Laboratory for procuring present-generation

manipulators and manipulators' booting.

With the advent of reactor fuel recycle systems and the environmental impact

of waste handling, it is conceivable that we are at the threshold of an entirely new

generation of remote handling devices.

* Research sponsored by the Energy Research and Development Administration under contract

with the Union Carbide Corporation.

155
II. Facilities and Equipment

The manipulator repair facility at ORNL has approximately 6000 square feet

of floor space, which is divided into four areas of operation. Two of these areas are used for contaminated repairs, and the other two are used for clean repairs and boot

fabrication.

The units weigh from 140 to 450 kilograms and are awkward to handle; so it was necessary to design and fabricate all the handling equipment for the dual purposes of

cell installation or removal and transportation to and from the repair facility. The

Laboratory has fabricated six portable dollies of a modified "A" frame design that

incorporates a hydraulic cylinder. The dollies are designed so that they become part

of the unit for transportation purposes. When taken to the repair shop, the manipulator

is placed in a glove box for cleaning or decontamination, and the dolly is then

available for other service.

III. Manipulator Boots

The special emphasis on cell containment at ORNL requires that all manipulators

be equipped with boots to seal the cell opening for the manipulator. This requirement

has enlarged the maintenance problem in that, with booted units, 50 to 60 percent of

the maintenance lies in replacing worn or damaged boots. Therefore, in 1961 the

Research Services Department instituted a development program to provide a material

and means of producing boots that would meet the needs of the Laboratory. This

investigation resulted in a spray method of boot fabrication in which liquid urethane

rubber is used.

From a maintenance standpoint, the protection afforded a manipulator by the use of boots has prolonged slave-end bearing life and has considerably decreased

mechanical failures.

Since the number of manipulator removals for boot changes needed to be reduced

and since nearly all boot failures occurred in the gauntlet area, a two-piece boot

is now in use in many hot cells at the Laboratory. This two-piece boot is fabricated

so that the lowerjSection, including gauntlet, can be remotely removed and replaced

by a manipulator . Also, because the activities at ORNL involve transuranium elements

and because of rigid safety requirements for handling these materials, a double-layered

boot is fabricated for 12 Model F manipulators in the Transuranium Processing Plant

(TRU).

IV. Programmed Maintenance

Until 1961, all manipulator maintenance work was performed on an "as-needed"

basis. Machines remained in operation until a failure occurred and the unit was

inoperable. Experience had shown that if minor adjustments could be made from time to

time, the more serious difficulties could be alleviated. To minimize cell downtime

and to achieve more efficient manipulator performance, a computer programmed maintenance

system was introduced. This program includes a two-week to one-month check on each

installed manipulator. Tape and cable tensions are measured and adjusted, all motions

are checked for possible malfunctions, and linkages are inspected for wear or out-oftolerance conditions. A preventive maintenance program of this type has proven very

satisfactory at the Laboratory, and an approximate 30% savings in maintenance costs

has been realized. Prior to programmed maintenance, the average unit was taken to the

manipulator repair facility twice per year for complete overhaul; after the programmed

I

156
{ system was established, the units now average one trip per year to the maintenance

I facility for these extensive repairs.

In general, statistics available from the programmed maintenance activities

1 show that annual costs of manipulator repairs will vary from $800 to $1200 per unit,

I excluding booting. The cell downtime due to manipulator removal and installation will

I vary from five to ten days per year. It should be noted, however, that the maximum

j time required to remove or install a unit is three hours. The five-to-ten days figure

is acquired by using an accumulation of the total time required for each service call.

Another interesting statistic shown by programmed maintenance is that the right-hand

manipulator requires twice as many repairs as the left-hand unit. This may indicate

that when designing an in-cell system, consideration should be given to a right

handed operation.

Discussions with OEINL hot-cell operators reveal that the presently available

manipulators are generally satisfactory for their research-type activities. Improvements

could possibly be made in feedback information such as feel, temperature, etc.; but

for their research, which is nonrepetitive in nature, present units provide the needed

dexterity. These units are detailed in ORNL specifications 10017-N-lll-X, XSP-239,

and MP-200. However, for scientific personnel designing fuel recycling systems or waste handling systems, presently available manipulators are not satisfactory. It appears that programmable modules to work in conjunction with automated equipment

are rapidly becoming a requirement in this remote handling area.

Unfortunately, units available on the open market are in no way adequate to

be considered for these needs. Also, the criteria for such programmable units are

incomplete.

As a result of the techniques and facilities described in this paper, it is

felt from both the maintenance and research viewpoint that a very satisfactory

manipulator maintenance program has been established at ORNL. This program will

be continuing since the number of manipulators is increasing and since the demands

on the functions are broadening.

V. Future Needs

VI. Conclusion

Table 1

Master-Slave Manipulators

Type Model Units

MSM

MSM

MSM

MSM

MSM

MSM

MSM

MSM

MSM

MSM

4

7

8

A

D

EFG

H

L

5

12

114

Electro Mechanical

49

742

14

23

4

2

11

157

5.4.1

PERFORMANCE EVALUATION STUDIES AT JPL

FOR SPACE MANIPULATOR SYSTEMSDr. Antal K. Bejczy

Member of the Technical Staff

Jet Propulsion Laboratory

California Institute of Technology

Pasadena, California 91103

I. Manipulators in Space

Space missions in the shuttle era will involve a large number of manipulative

handling tasks never before performed by man-machine systems in space. E.g., cargo

handling in the shuttle, assembly of structures and satellite servicing in earth orbit,

exploration of lunar and planetary terrains, or sample analysis in sealed space

laboratories will require the extension and augmentation of man's manipulative

capabilities by employing remotely operated manipulator systems. Remote manipulation

implies operating conditions which exclude or greatly impair the direct visual or other

human sensory (e.g. force) contact between the operator and the manipulator, and impose

various information and control communication limits.

As indicated above, the spectrum of projected applications of manipulators in space

ranges from various operational tasks to primarily exploratory or research tasks.

Operational tasks involve the handling of artifacts under prepared or known conditions,

while exploratory or research tasks will also involve the handling of natural objects

under partially unknown or unpredictable conditions.

The various space applications logically dictate various requirements for the

manipulator's size, work space, load lifting capability, and effector dexterity, feedback

sensors, control system, and system interfaces. Further, the variety of space

environment characteristics (local g-level, radiation hazard, dust, communication distance,

etc.) impose different constraints on the design and use of manipulators in the projected

space missions. An overview and some technical details for the performance requirements

of several space manipulators can b e found in Refs. 1 and 2. Manipulator performance

requirements for unmanned exploratory or research missions (e.g., to explore the martian

terrain using a roving vehicle equipped with a manipulator) have been outlined in detail

in Refs, 3 through 10.

Despite the variety of the mechanical, control, system interface, or environmental

characteristics of manipulators required for various future space missions, improved

efficiency in remote control and improved man-machine interface are common requirements

for all space manipulator systems. Therefore, the problems of remote control and man- machine interface have been selected as central issues for performance evaluation studies

at JPL,

* This work represents one phase of research carried out at the Jet Propulsion

Laboratory, California Institute of Technology, under contract No, NAS7-100,

sponsored by the National Aeronautics and Space Administration,

159
II. JPL Breadboard Systems

The JPL performance evaluation studies are of experimental nature and utilize two types of breadboard systems: a teleoperator (or man-machine) breadboard and a robot

breadboard,

1. The man-machine breadboard for remote manipulator control is organized into two separate areas: the work room and the remote control station. Table 1 lists the present

elements and the operational status of the man-machine breadboard system.

Ta1;le 1. Elements of JPL Teleoperator Breadboard

WORK ROOM RFIJOTE CONTROL STATION

Humanoid Slave Arm (0) « ILAWorvt-J.t-U'—'it ijCloL':--!- /\ ,L 1 U V, ^

. "CURV" Linkage Arm (0-D) Tin T VP T-o p 1 Pnnf"7"nl P;^np1 (Vi^ Parallel Jaw Hands (0) « Convt? t" t i b 1 e Hand Controller (0)

Swinging Hand (0) TV P^T) Tilt 7c)nm ronfrol ( Ci^ Humanoid Hand (0) Stereo

. Stereo TV Cameras (0) > TV Displays (0)

. Mono TV Camera (0) Mono J

Proximity Sensors (0) . Audio and Digital Displays for Four

. Touch Sensors (B-L)) Proximity Sensors (0)

Force/Torque Sensor (D) Visual Display for Multipoint

Minicomputer, Interdata M70 (0) Proportional Touch Sensor (0)

Control Programs (0) Force/Torque Sensor Display (D)

. Six-Wieel Flexible Vehicle (0) Teletype for Computer Command (0)

Four-lsTieel Rigid Vehicle (0) Voice Command System (D)

Notes

:

(0): Operational; (E) : Bench Model; (D) : Development

Fig, 1 shows the JPL/Ames anthropomorphic manipulator with the master arm worn by

the operator, manual control console, Interdata M70 minicomputer dedicated to manipulator

control, and TV cameras for stereo aiv-i mono viewing of the work scene. The arm (see

also Ref. 11) has eight degrees of freedom: seven revolute joints for arm motion, each

joint driven by d.c. torque motors through hamonic drive gears, plus one motor for

driving the end effector. The slave arm can be position controlled in three ways: from

the master arm, from the manual control console (one control per joint), or from the

dedicated minicomputer. Fig. 2 shows part of the interior of the remote control station

with stereo and mono TV displays, the operator in the master arm, and various control

input and information display devices.

Fig, 3 shows the JPL/CURV linkage arm. As seen in this figure, the arm is mounted

to a turret on a vehicle. The turret can be rotated and elevated. The arm (see also

Ref. 12) has seven degrees of freedom (six for arm motion and one for end effector opening

160
161
Figure 2. Remote Control Station Interior
or closing) and is driven by hydraulic actuators. The arm has two interesting features:

it provides true linear extension by the use of an idler gear, and wrist disorientation is

eliminated during changes in elevation and extension of the arm by the use of a double

parallelogram added to the linkage. The arm is also equipped with a full force/torque

sensor (built by Vicarm Inc. , Mountain View, CA) mounted between the end effector and

last wrist joint.

The new control system of the JPL/CURV arm, developed at JPL, includes proportional

servo valves, position feedback at each joint, interfaces to the Interdata M70 minicomputer,

and a universal control panel shown in Fig. 4 together with the stereo and mono TV displays.

The panel is a combined control and switch board and has been designed with the specific

purpose in mind to develop, study, and evaluate various schemes and capabilities of

distributing control functions between man and machine. The control can be fully computer

control, partly computer and partly manual control, or fully manual control. But even

manual commands can be addressed to the computer. Of course, manual commands can also be

addressed directly to the servo system. Manual inputs can be position or rate commands

for each joint individually, or rate commands combined for several joints using two threedimensional joysticks.

Fig. 5 shows the breadboard of a multipoint proportional tactile sensor with visual

display. The sensor is built from two diagonally arranged nets of electrodes separated by

conductive rubber. In the breadboard, the electrodes form a 4 by 8 matrix pattern, and

the intersections of electrodes (the "sensitive cells") possess diode characteristics

so that the pattern of pressure distribution can be found by electronically scanning

the state of the sensitive surface. The tactile sensor is flexible, and can be wrapped

around a curved body.

2, The JPL robot breadboard is organized around the concept of an "information

gathering mobile laboratory system." The manipulator, mounted on a surface roving vehicle,

is part of the system and is fully computer controlled. The elements of the robot

breadboard are listed in Table 2.

Table 2. Elements of JPL Robot Breadboard

Stanford Electric Arm

. TV "Eye" with Pan-Tilt Control

Laser Range Finder

Four-wheel Vehicle, Independent Drive, Dual Steering

Expanded Minicomputer (SPC-16)

. Link to PDP-10 Computer

. IMLAC, TV Displays

Key-boards for Computer Com-mands

Large Amount of Computer Programs for

Arm Control

Scene Analysis

163
Figure 4. JPL/CURV Arm Universal Control Panel

PROPORTIONAL

TACTItE SENSOR

4 , $ 37 "OTS

Figure 5. Proportional Tactile Sensor with Visual Display

164
Fig. 5 shows the vehicle-arm-TV- laser system of the robot breadboard in two views.

The two racks on the vehicle contain part of the system electronics. The package at the

center rack contains the gyro compass for vehicle guidance and navigation. More on the

robot breadboard and the manipulator can be found in Refs. 13 through 15.

Further literature on the JPL teleoperator and robot work, respectively, are

listed from Refs. 16 through 36 and from 37 through 53.

III. JPL Performance Study Objectives

The teleoperator (or man-machine system) performance studies at JPL are organized

around the following specific objectives:

Study the effect of local sensory feedback, end effector design, and man-machine

information/control interface on remote manipulator control performance, and

complement the study by the development of mathematical models for predictive

performance evaluation of remotely controlled systems to the extent it is feasible.

1. Local sensory feedback includes proximity, tactile, and force/torque sensors which supplement the visual information for manipulator control. In this area,

two items are of particular interest: (a) the type and quality of sensor information

required for an efficient control, and (b) the properties of schemes for

integrating information from different sensors for various tasks.

2. The end effector design study is aimed at the development of efficient multifunctional terminal devices for remote operation and investigates the following

specific areas: (a) the number, articulation, and control of "fingers", and

(b) the integration of the end effector with proprioceptive and exteroceptive

sensors.

3. The man-machine information/control interface design study is aimed at the

evaluation of the human operator's interaction with the remote manipulator control

with or without a computer in the control system. The study is being conducted within

the framework of a "supervisory control system" (see Ferrell, W.R. , Sheridan, T.B.,

"Supervisory Control of Remote Manipulation", IEEE Spectrum, October 1967, pp. 81-88)

and is centered around two main items: (a) Formulation of a computer control language

for remote manipulation, that is, formulation of the human input end of the

control algorithms which should be able to combine positional or directional

coordinates with information generated by proximity, tactile, and force/torque

sensors mounted to the end effector, and (b) convenient display of relevant sensor information to the human operator, using also computer algorithms for display

purposes

.

4. The development of mathematical models for predictive performance evaluation of

remotely controlled manipulators serves two purposes: (a) .to rationalize the

empirical data in a quantitative framework, and (b) to reduce the dimensionality

(or number) of performance experiments required to evaluate alternative systems.

165
Figure 6. JPL Al Robot Breadboard

166
IV, Control Performance Experiments and Results

The teleoperator control experiments so far have been concentrated on the problem

of terminal phase control of manipulator motion: approaching, finding, contacting, and

grasping various regular or irregular objects using different terminal devices and

proximity sensors attached to the terminal device. The proximity sensors have been

developed at JPL and are described in Ref. 32. The proximity sensor produces a voltage

signal when the sensor's sensitive volume -- which is permanently focused at a distance

of about 10 cm in front of the sensor head --"touches" a solid surface as the end effector

approaches the surface.

The end effector-proximity sensor configurations employed in the control performance

experiments are shown in Figs. 7 and 8. Fig. 7 shows a parallel jaw end effector mounted

to the JPL/Ames arm and equipped with four proximity sensors, two sensors on each finger.

Fig, 8 shows a humanoid hand (the Belgrade prosthetic hand) mounted to the JPL/Ames arm

and equipped with three miniaturized proximity sensors.

Control performance experiments have been conducted both in manual and computer

control modes. In the computer control experiments, the operator can specify four

voltage levels (or five "distance regions") to be "recognized" by the computer programs

which automatically guide the manipulator's motion. The programs can presently use

signals from four proximity sensors. The operator specifies the control meaning of the

sensor signals for each task. Typical computer control experiments were: locate an object for grasping; stop the manipulator's motion at a given distance from an object;

avoid obstacles by a specified maneuver; etc.

In the manual control experiments, the information from four proximity sensors

was directly presented to the operator through four different audio tones. Each sensor

was connected to a different loudspeaker. The four loudspeakers are arranged at the corners

of a two by two meters vertical quadrangle around the operator. The pitch of the tone

generated by the voltage output of the sensor indicates increasing or decreasing distance

between sensor head and objects. The manual control experiments were designed to test

the operator's ability to integrate the information content of the proximity sensor

signals with incomplete visual feedback and perform remote manipulator control tasks

which are very difficult or nearly impossible under a given visual feedback arrangement.

Typical tasks were: find a block hidden in a box; locate critical parts of the work

scene (e,g,, edges, balls, blocks); etc.

Both the computer control and manual control experiments with proximity sensors

are described and evaluated in detail in Refs, 20 and 21, and are shown in a movie,* As

an illustration. Fig. 9 shows two task arrangements. The two tasks were:

Task 1 : Move from standby position to the rectangular block at "A", pick it up, and place it on top of another rectangular block located at "B", and align

the two blocks. The two blocks are of equal size. See the left part

of Fig, 9 for the physical dimensions of this task.

* "Crossing Visual Barriers in Remote Manipulator Control," Jet Propulsion Laboratory

Sound Movie, No, 1015, 16 mm. May 1975,

167
DOWNWARD"

Figure 7. Parallel Jaw End Effector with Four Proximity Sensors

Figure 8. JPL/Ames Arm with Humanoid Hand Equipped with

Three Miniaturized Proximity Sensors

MONO TV MONO TV

8

I Figure 9. Arrangements for Performance Tests Using j Proximity Sensors

168
Task 2 : Move from standby position and pick up a partially obscured irregular

object (a rock). See the right part of Fig. 9 for the physical

dimensions of this task.

Table 3 summarizes the information feedback conditions and performance data for

tasks 1 and 2.

Table 3. Performance Data for Tasks 1 and 2

Visual and Sensing Conditions

Mean time of

experiments

ten

Csec)

Standard

deviation (sec)

Task 1 Task 2 Task 1 Task 2

1. Only visual information; stereo

plus mono TV

z4 25 2. 3 3. 2

2. Stereo TV plus two front sensors 25 24 3,1 3.1

3. Stereo TV plus two do\m sensors 27 25 2.9 2,9

4. Stereo TV plus all four sensors 31 32 4.2 4.6

5. Mono TV plus two front sensors 22 24 1,9 3,0

6. Mono T\' plus two down sensors 23 21 2.0 2.8

7. Mono TV plus all four sensors 30 29 3.8 3.8

8. Only mono TV information 36* 39+ 6.1 5.9

9. Only stereo TV information 38*''= 38++ 7.4 6.1

*

+++

Two mistakes or bad alignments

Four mistakes or bad alignments

Three mistakes

Five mistakes

As seen in Table 3, tasks 1 and 2 could be successfully performed using visual

information alone provided that the operator had access to two different views simultaneously as shown in Fig, 9. When the operator had access only to one view, stereo front

view or mono side view, systematic success could not be achieved. Several attempts

ended with mistakes or bad alignments, and whenever the operation was successful, it

took about 507= longer time to achieve success as compared to the performance time with

two different simultaneous views. But control performance was always successful using

oae view (mono or stereo) combined with proximity sensor infomation, and the performance

time was nearly identical to the performance time with two different simultaneous views.

It is also noted that dealing with one view combined with audio information from

proximity sensors resulted in less mental stress for the operator than handling two different views simultaneously.

Fig, 10 shows a few real task scenes compared to the TV views presented to the

operator.

The main conclusions of the control performance experiments can be summarized as

follows: (1) Automated proximity sensor control can result in faster, safer, easier,

and more economical operation. But the operator must have a clear a priori notion on

the expected outcome of an automated proximity control loop as applied to a given task

before he can confidently initiate the use of that automatic loop. (2) Proximity sensor

169
REAL SCENE TV DISPLAY TO OPERATOR

Figure 11. Handling Irregular Objects with Articulated Adaptive

Hand Interfaced with Proximity Sensors

170
I information can replace or supplement part of the visual information required for control,

i (3) Control tasks which cannot be performed using visual information alone can be performed

I by a combined use of proximity sensor and visual information. (4) The number of

independent proximity sensor signal displays affects the operator's control performance.

(5) Control performance is strongly influenced by the location of the proximity sensors

I on the end effector. (6) In general, handling irregular objects requires considerably

I more information and control effort than handling regular objects. But the effort on

I the conscious level can greatly be reduced by employing an articulated and adaptively

' controlled end effector ("hand") as illustrated in Fig. 11.

The remote manipulator control experiments have shown so far that a realistic

performance evaluation requires the simultaneous consideration of at least three somewhat

I overlapping performance measures: (a) The binary categories of "success or failure"

i for evaluating the effectiveness of control. (b) The combination of "accuracy and time"

i for evaluating the quality of control. (c) The integrated "consumption of resources"

' for evaluating the cost of control.

The control experiments have also shown that the performance evaluation studies will

} have an important effect on the definition and development of computer-aided remote

manipulator control technology. In fact, this technology is still in the early state of

j development (or, better, in the early state of "inventiveness"). Therefore, at the

,j present time, the real significance of the performance evaluation studies lies mostly

in assisting the development of computer-aided manipulator control.

The performance evaluation studies allow three concluding remarks. (1) It became evident that more systematic work is needed on task analysis and "mechanical"

task description. (2) The quality of breadboard hardware has a significant impact on practical performance evaluation studies, (3) It is established that proximity

sensors mounted to the end effector have a significant effect on the control performance

of remote manipulators.

Ongoing and future performance evaluation studies at JPL include: (1) The use

of both tactile and force/ torque information in both manual and computer control modes.

(2) Integration of TV and other external sensory information within a variable video

frame. (3) Display-oriented control. (4) Development of a new type dexterous end

effector integrated with proprioceptive and exteroceptive sensors. (5) Development

of a convenient and versatile "supervisory control language."

REFERENCES

1. Heer, E., Ed., " Remotely Manned Systems, Exploration and Operation in Space ," Proceedings of the First National Conference, California Institute of Technology

Publ. 1973.

2. Proceedings of the Second Conference on Remotely Manned Systems, Technology and

Applications, University of Southern California, Los Angeles, California, June 9-11,

1975.

3. Heer, E., "Remotely Manned Systems for Exploration and Operation in Space -- An

Overview," JPL Internal Report 760-81, 1 July 1972,

4. Heer, E,, et al, "Summary Report -- Advanced Teleoperator/Robot Studies for Planetary

Surface Roving Vehicles," JPL Internal Report 760-75, 1 July 1972,

171
5. Choate, R. , and Jaffe, L.D. , "Science Aspects of a Remotely Controlled Mars Surface

Roving Vehicle," JPL Internal Report 760-77, 1 July 1972,

6. Bejczy, A.K. , "Remote Manipulator Systems, Technology Review and Planetary Operation

Requirements," JPL Internal Report 760-77, 1 July 1972.

7. Anthony, V.F. , "Motion Control Requirements for Planetary Surface Roving Vehicles,"

JPL Internal Report 760-78, 1 July 1972,

8. Jaffe, L.D., "Problems of Previous Scientist/Machine Operation Interfaces," JPL

Internal Report 760-79, 1 July 1972,

9. Seifert, H,S., "Analytical/Experimental Definition of Man-Machine Interface Characteristics in Remotely Manned Systems," JPL Internal Report 760-80, 1 July 1972.

10. Bejczy, A, K. , "Advanced Automation Systems for Manipulator Control," JPL Internal

Report 760-93, December 1972.

11. Vykukal, H.C., et al, "An Anthropomorphic Master-Slave Manipulator System," in , Remotely Manned Systems -- Exploration and Operations in Space , E, Heer, ed, ,

' California Institute of Technology Publ., Pasadena, California, 1973.

12. Uhrich, R.W, , "NUC Manipulators',' Ocean Technology Department Contributions to IEEE 1971 Ocean Environment Conference, NUC, San Diego, California, September 1971,

13. Dobrotin, B.M. , Scheinman, V,, "Design for Computer-Controlled Manipulator for

Robot Research," Third IJCAI, Stanford, California, August 1973,

14. Lewis, R.A, , Bejczy, A.K. , "Planning Considerations for a Roving Robot With Arm,"

Third IJCAI, Stanford, August 1973.

15. Whitney, W.M. , "Human vs. Autonomous Control of Planetary Roving Vehicles,"

IEEE Symposium on Systems, Man, and Cybernetics, Dallas, Texas, October 1974.

Further References on JPL Teleoperator and Robot Work

A. Teleoperator Project

16. Alsberg, H. , "An Augmented Active Image Transmission System for Visual Man-Machine

Interaction," 1973 IEEE Conference on Systems, Man, and Cybernetics, Boston,

November 5-7, 1973,

17. Alsberg, H. , and Nathan, R. , "Man-Machine Interactive Imaging and Data Processing

Using High Speed Digital Mass Storage," Proceedings of the Human Factors Society,

18th Annual Meeting, October 1974.

18. Ancker, Jr., C.J., "Stochastic Modelling of Remotely Manned Systems," JPL Internal

Report 760-116, December 1, 1974.

19. Bejczy, A.K. , "Machine Intelligence for Autonomous Manipulation" in Remotely

Manned Systems, Exploration and Operation in Space , E. Heer, ed., California

Institute of Technology Pub., Pasadena, California, 1973.

20. Bejczy, A.K. , "Environment-Sensitive Manipulator Control, " Proceedings,

IEEE Conference on Decision and Control, Phoenix, Arizona, November 1974.

172
21. Bejczy, A.K, , "Effect of Hand-Based Sensors on Manipulator Control Performance,"

Proceedings of Second Conference on Remotely Manned Systems, Technology and

Applications, University of Southern California, Los Angeles, California.

June 9-11, 1975. (To appear in a special issue of "Mechanism and Machine Theory.")

22. Bejczy, A.K., "Algorithmic Formulation of Control Problems in Manipulation,"

Proceedings of the 1975 IEEE International Conference on Cybernetics and Society,

San Francisco, California, September 23-25, 1975.

23. Bejczy, A.K. , "Distribution of Control Decisions in Remote Manipulation,"

Proceedings of the 1975 IEEE Conference on Decision and Control, Houston, Texas,

December 10-12, 1975,

24. Bejczy, A.K. , Johnston, A.R. , "New Techniques for Terminal Phase Control of

Manipulator Motion," JPL Internal Report , 760-98 , February 1974,

25. Deutsch, S., and Heer, E., "Manipulative Systems Extend Man's Capabilities in

Space," Astronautics and Aeronautics, June 1972.

26, Freedy, A,, "Remote Manipulation by Means of the Autonomous Control Sub-System,"

Final Report, Jet Propulsion Contract No. 953402, Perceptronics , Inc., August 24, 1972.

27. Heer, E., "Teleoperators : Status and Technology Requirements," Presented to SAE

Aerospace Control and Guidance Systems Committee, September 23, 1971.

28. Heer, E. , "NASA Developments and Their Spin-Off to Undersea Applications,"

Presented to Navy Workshop on Undersea Manipulator Operator Performance,

Williamsburg, October 26, 1971.

29, Heer, E., "Remote Control of Planetary Space Vehicles, " IEEE '73 INTERCON,

New York, March 26-30, 1973,

30, Heer, E,, "Remotely Manned Systems for Exploration and Operation in Space,"

Proceedings of the First International Symposium on Theory and Practice of Robots

and Manipulators, Udine, Italy, September 5-8, 1973.

31, Heer, E,, Bejczy, A.K. , "Teleoperator/Robot Technology Can Help Solve Biomedical

Problems," JPL TM 33-271, January 1, 1975.

32, Johnston, A.R. , "Optical Proximity Sensors for Manipulators," JPL TM 33-612,

May 1, 1973.

33, Johnston, A.R. , "Proximity Sensing for Manipulators and A Laser Rangefinder for

a Robot," Third International Joint Conference on Artificial Intelligence,

Stanford, August 1973,

34, Johnston, A.R. , "An Experiment in Manipulator Control with Proximity Sensors,"

JPL TM 33-678, April 1, 1974.

35. Johnston, A.R. , "Proximity Sensor Technology for Manipulator End Effectors,"

Proceedings of Second Conference on Remotely Manned Systems, Technology and

Applications, University of California, Los Angeles, California, June 9-11, 1975.

36, Tippins, H,H. , Johnston, A.R. , "Application of Multiple Detector Arrays to Optical Proximity Sensors," JPL Internal Report 760-128, August 8, 1975.

173
B, Robot Project

37. Bejczy, A,K. , "Robot Arm Dynamics and Control," JPL TM 33-669, February 15, 1974,

38. Dobrotln, B.M. , "JPL's Robotics Program as an Extended Control System," SAE

Control Meeting, April 1973.

39. Dobrotin, B.M. , "Robots for Space Exploration," IEEE Symposium on Systems, Man and

Cybernetics, Dallas, Texas, October 1974.

40. Feldman, J., Yakimovsky, Y., "Design Theory and Artificial Intelligence:

A Semantic-Based Region Analysis," Artificial Intelligence Journal 5 (1974).

41. Hong, J. P., "Registration of Points," Princeton Conference on Information Sciences

and Systems,

42. Hong, J. P., Liporace, L. , "A Terrain and Object Model Derived from Range

Data and Useful to a Robot," Sixth International Conference on Systems Sciences.

43. Hooke, A.A. , et al, "The Impact of Robots on Planetary Mission Operations"

International Telemetry Conference, Los Angeles, California, October 1974.

44. Levine, M.D. , "Digital Processing of Stereoscopic Image Pairs," Proceedings of the

1973 IEEE International Symposium, Toronto, Canada,

45. Levine, M.D., "Scene Analysis for a Breadboard Mars Robot Functioning in an Indoor

Environment," JPL TM 33-645, September 1, 1973.

46. Lewis, R.A. , "Autonomous Manipulation on a Robot," JPL TM 33-679, March 15, 1974,

47. Markiewicz, B.R., "Analysis of the Computer Torque Drive Method and Comparison with

a Conventional Position Servo for a Computer-Controlled Manipulator," JPL TM

33-601, December 1972,

48. Mathur, F.P., "Phase I Report on A Cognitive Operating System for JPL's Robot,"

JPL TM 33-568, September 15, 1972,

49. O'Handley, D.A. , "Scene Analysis in Support of a Mars Robot Rover," Computer

Graphics and Image Processing.

50. Yakimovsky, Y,, "A Semantics-Based Decision Theoretic Region Analyzer," Third IJCAI,

August 1973,

51. Yakimovsky, Y,, "Boundary and Object Detection in Real-World Images," IEEE Conference

on Decision and Control, November 20-22, 1974, Phoenix, Arizona; JPL Technical

Memo 33-709, November 15, 1974.

52. Yakimovsky, Y., "Extracting 3-D Information for 2-D Images Using Multi-camera

System," presented at Milwaukee Symposium on Automatic Control.

53. Yakimovsky, Y,, "Computer Software Using Artificial Intelligence A.pplied to Pattern Recognition," Proc. 2nd Intl. Joint Conference on Pattern Recognition,

August 1974,

174
5.4.2

PERFORMANCE MEASUREMENT FOR UNDERSEA SYSTEMS*

Alan J. Pesch

William R. Bertsche

Eclectech Associates, Inc.

North Stonington, Conn. 06359

I. Introduction

Remote manipulators have found increasing application in the undersea

environment for the past two decades. The earliest systems were basic in design

and were utilized primSrily for object recovery and limited scientific tests. More

recent systems, however, have been designed to perform complex work. Undersea

remote manipulators are now deployed which can drill holes, operate impact hammers,

wire cutters, and a host of special interchangeable tools and scientific equipment.

The interest in the efficient utilization of the increased capability of the latest

generation of manipulators has led to the study and documentation of manipulator

design factors which potentially affect an operator's ability to utilize the

manipulator to perform undersea work assignments. The testing and measurement

procedures adopted to evaluate these systems are of a pra^natic design such that

results may be directly applied to undersea remote manipulators by the various

individuals and agencies involved in manipulator design*

This paper presents an overview of a measurement and testing methodology

wrtiich has been effectively used to evaluate the performance of numerous types of

undersea remote manipulators. It is the opinion of the authors that for the types of

undersea remote manipulators described, this methodology allows a comprehensive

comparison of system type and performance and provides guidance in design of new

systems. The methodology has been utilized to experimentally evaluate four rate

controllers and two position controllers on the same manipulator. The methodology

has recently been expanded for the evaluation of force feedback manipulator systems.

II. Remote Underwater Manipulator Systems

The majority of the manipulator systems utilized underwater are of a similar

design with respect to operator interface characteristics. Below is a general

description of the systems to which this paper is addressed. Figure 1 illustrates

the relation of the basic components.

* This paper is based on research supported by the Office of Naval Research,

Engineering Psychology Programs.

175
176
- Slave Arm: work is achieved in the water environment by an articulated

slave arm. This arm is hydraulically and electrically powered. The arm payload

is medium (50 pounds) to high (200 - 300 pounds). Control signals to the slave arm components are generally electrical. The slave arm is usually mounted on a maneuverable

submersible vehicle.

- Controller: the operator utilizes a controller to generate analog or discrete

command signals for the slave arm. The controller may consist of push buttons,

switches, joystick, anthropomorphic harness, or an end effector grip. The master

controller is located in a submersible or on a surface ship.

- Operator Interface Problems: the operator controls motion, position, and in some instances, force of the slave arm. This is accomplished by operating the

controller while observing the results of his control actions remotely through a viewport, on closed circuit TV, or on various electronic displays. Lack of visual

depth cues is a prevalent problfem in all viewing methods. Visual distortion is greatest

when using only the viewport due to the air-glass-water interface for any uncorrected

optical or TV system.

- Work Requirements: underwater work varies from light to heavy tasks. Light

work includes sample gathering , rigging cables and hooks, and operating scientific

equipment. Heavy work includes wire cable cutting, drilling steel plates, retrieval

of heavy objects. The water environment can vary from clear to turbid. Underwater

auxiliary lighting is usually required.

The critical design requirements which set underwater remote manipulators

apart from hot lab remote manipulators are massiveness, water seal of the slave arm,

and the remote position and conditions under which the operator exercises control of

the slave arm. Design of these systems must necessarily be directed to account for

these effects.

III. Measurement/Testing Methodology

Rate and Position Controller Manipulators

There are two portions of the measurement/testing methodology. The first is

simply a method of determining the definition and nature of the variables which

comprise the system under test. The second is the method of testing, documenting,

and evaluating the work potential of the system with an operator in control. Each

is discussed below.

1. Definition of System Variable

Preliminary comparison of underwater remote manipulator systems may be made

by comparing plans and specifications of the various systems. Required is a comprehensive and standard set of variables to allow comparison. Table 1 indicates

a set of proposed variables v*^ich may adequately specify a rate or position control

remote manipulator. The upper set of variables in Table 1 indicates measures of the

manipulator's static and dynamic response to standard input signals. These data

are measures of the tip response of the articulated arm, not individual actuators.

177
Table 1. System Variable Definition for Rate and Postion Control Remote Manipulators

RESPONSE VARIABLES

It is recommended that these variables be specified for each of the 6 degrees of

freedom in polar coordinates. The response variables are those of the "tip" of the

articulated arm.

Rise Time

Setting Time

Overshoot

Slew rate

Time delay

Bandwidth

Dead Band

Droop: Compliance

Minimum Motion

Drift

Time required for the output response to a step input to rise

from 10 to 90^ of its final value

Time required for the output to reach and maintain the final

value + 10^, for a step input

The percentage of signal change the output exceeds its final

value in response to a step input

The maximum constant velocity a joint will attain

Time the output response is displaced from the corresponding

input response

The range of frequencies over which the system will respond

satisfactorily

The positional difference the master controller may move before

the slave begins to track

Droop is a measure of how much the tip of the manipulator is

deflected from no load to full load conditions (inches).

Compliance is droop divided by the full load (pounds)

The minimum distance a joint may be reliably moved

The displacement of a joint over an arbitrary time increment

divided by the time of the increment

178
Table 1. (Continued)

DESIGN ALTERNATIVES

Operational Envelope A definition of the working volume of the slave arm

Degrees of freedom The number and arrangement of rotatable or extendable joints

Anthropomorphic or Terminus design is an arbitrary arrangement of joints to spatially

terminus design position wrist and hand joints in the X, Y, Z space. Wrist joints

provide pivoting and rotations of the hand. Anthropomorphic

design is a one for one match of joints to the corresponding joints

of the human arm

Motion range

Linear extension

The number of degrees (inches) a joint is free to move

Implies that the articulated arm can extend or contract in a straightline fashion

Continuous rotation Implies that a joint may be rotated continuously in one or the other

direction

Tool design Includes design provisions for handling and utilizing special tools

MASTER CONTROLLER POSITION CONTROL

Exoskeletal strapon Refers to postion controllers that strap onto operator's arm. Joints are matched one to one to the arm

Exoskeletal harness Refers to position controllers into which the operator inserts his

arm. It is loose fitting and joints are approximately matched to the operator's arm

Terminus grip Refers to a terminus configured position controller. The operator

touches only the hand grip and inputs all motions to the grip

Individual controls A particular arrangement of controls for ordering the position of

individual joints

MASTER CONTROLLER RATE CONTROL

Pushbutton/switch

controls

Variable rate

Programmed motions

Bi-directional or unidirectional switches to control joint motions

individually or in combined motions

Displacement controls which control the rate and direction of

individual joint motions

Controls which provide automatically coordinated motion of several

joints

179
The lower set of variables indicate selected examples of several typical design

alternatives which the system may incorporate. A manipulator system under consideration

might incorporate any practical combination of these design alternatives.

The variables shown in Table 1 were defined during the research program in order

to define the nature and characteristics of the various manipulator systems which were

examined. The interest in system variable definition and measurements resulted from

the requirement to define a set of independent variables which may be related to

dependent measures of operator performance in applied undersea work tasks. The

variables listed in Table 1 are meant to serve as primers to an encompassing set of

definitions required for widespread application.

Measurement of the response variables in terms of arm tip motion is recommended

to provide a common set of data for comparison. Previously, only the response of

individual actuators was commonly specified. Systems were difficult to compare when

the articulated arms were vastly different, e.g., terminus configuration vs. anthropomorphic configuration. Documentation in polar coordinates is recommended because

study of existing articulated arm manipulators indicates many of the polar coordinate

motions are controlled by single actuators, thus simplifying the experimental procedure

required to measure responses. Additionally, location of the tip in its motion range

does not usually change the actuators controlling polar coordinate motion. Figure 2 illustrates the polar coordinate motions.

Measurement of the response variables in an orthogonal set of axes, X, Y, Z,

Wx, Wy, Wz, is not recommended because of several inherent problems. Motion of the

tip of the manipulator in any of the axes directions almost always requires the co- ordinated movement of several actuators. Additionally, the position of the manipulator

tip in its motion range may change the actuators which contribute to the motion of

interest. Figure 2A illustrates that motion in the X direction may be controlled

wholly by two different actuators, depending on the tip location.

2. System Performance Evaluation

The above set of variables can be utilized to identify differences between

candidate systems. This knowledge, however, is not sufficient to judge how well each

system can be utilized to perform underwater work. Performance evaluation is achieved

by performing a set of prognostic tests, evaluating the test results, and documenting

the relative and potential performance of each system.

The prognostic tests selected to evaluate underwater remote manipulators

are unique in several ways. First, the tests are conducted in a simulated underwater

environment to closely replicate the distorted visual feedback path presented to the

operator. Then, a series of selected tasks representative of both light and heavy

work, typical of underwater tasks, are performed. The tasks range in difficulty from

simple to a high degree of difficulty. All of the tasks are of an "applied" nature,

that is, they are identical to realistic tasks that may be performed at-sea. Each

test is designed to require certain basic control and behavior response on the part

of the operator. These responses were selected as basic elements of underwater work

from time-motion studies.

t

I

180
z

Wz

CJ^ W;

TIP NOTION

LINEAR EXTENSION

JOINT

TIP MOTION

<}=={>

ROTATION JOINT

A. ORTHOGONAL AXES SYSTEM

B. POLAR COORDINATES

Figure 2. Coordinate Systems For Response Variables,

Six Degrees of Freedom

181
The prognostic tests are performed repeatedly under controlled conditions by

groups of operators to determine average performance times and eliminate learning

trends. Data are collected during the various elements of the prognostic tests.

Data are generally a time measurement. Accuracy of work, operator comments, and the

subjective opinions are also recorded. The data are compiled and analysed and presented

in three forms.

(a) Completion time of each test.

(b) Average time for basic behavior elements.

(c) Accuracies of test performance.

Completion times of applied tasks are shown in Figure 3 as ratios for the

comparison of manipulator performance to direct work by a diver. These data appear

in D/R matrices (diver times/remote manipulator times). Data collected in this format

are shown for four rate controlled manipulators and two position controlled manipulators.

The larger numbers in the denominators of the ratios indicate in multiples how much

longer the manipulator took to perform the work than the diver. Careful study of

the data indicates that certain manipulator systems were better for specific types

of tasks, but not necessarily all tasks. An important property of this matrix is

that these data are indicative of the ability to sequentially perform basic control

responses in the execution of a complex task in the environment.

Average completion times for the behavior elements of all the work are plotted

in a second matrix. The data points are D/R ratios (diver/remote) of completion times.

Figure 4 illustrates these data compiled for the four rate controllers and two position

controllers. The behavior elements selected from time-motion studies represent common

control responses performed time after time in various combinations to perform the

prognostic tests. These data are particularly important in the design of a system

for specific work. A system or combination of systems may be selected which best

perform selected work elements if the work can be broken down into behavior elements.

This procedure may then be termed "projective" and may be useful for designing systems

in the future with some prior knowledge of performance.

The third set of data recorded during the prognostic tests are various measures

of accuracy. These measures record the success of performing certain of the prognostic

tests. For example, drill hole angle in the drilling task indicates the success with

which operators held and moved the drill bit perpendicular to the drilled surface.

Figure 5 illustrates data collected for drill angle for the two position control

manipulators. This type of data may be considered by the designer where behavior

sequences and particular related tasks are contemplated.

3. Application of Methodology

The measurement and testing methodology described in this section has been

utilized to evaluate four rate control and two position control underwater remote

manipulators (data in Figures 3, 4, and 5). The testing methodology documents changes

in system performance as system specifications are changed. These data should be

useful in extrapolating from performance measures to system design.

182
D/r Matrix for Applied Tasks

RATE CONTROL POSITION CONTROL

Discrete

Switches

Actuator

, buttons

Combined Actuator

Joystick

Discrete

Position

Combined

Position

PBFR Fixed

Rate

PBVR

Variable

Rate

JSFR

Fixed

rate

JSVR

Variable

rate

Knobs

dials

Anthropomorphic

harness

Sample

Collection 1/14 1/12 1/14 1/11 1/15 1/5

Valve

Manipulation 1/10 1/9 1/9 1/9 , 1/10 1/3

Rigging chain

hooks 1/16 l/i6 1/20 1/19 1/19 1/8

Bolt removal

tool

1/9 l/<5 1/12 1/10 l/l5 1/6

Tapping 1/1.5 1/1.3 1/1.4 1/1.4 1/1.8 1/1.1

Threading l/lO 1/9 1/8 l/lO 1/13 1/9

Drilling 1/1.6 1/1.6 1/2.8 1/2.5 1/2.3 1/1.6

Connect/

disconnect 1/27 1/29 1/24 1/31 1/24 1/11

PBFR Pushbutton fixed rate

PBVR Pushbutton variable rate

JSFR Joystick fixed rate

JSVR Joystick variable rate

Figure 3. D/R Matrix For Applied Tasks

183
D/R Matrix for Behavioral Elements

RATE CONTROL POSITION CONTROL

Discrete Actuator

Switches, buttons

PBFR Fixed

Rate

Simple Travel l/l2

Complex

Travel

Simple grasp

Alignment

Tool Use

1/12

1/36

1/18

1/1.2

PBVR

Variable

Rate

1/10

1/9

1/31

1/20

l/l.l

Combined Actuator

Joystick

JSFR

Fixed

Rate

1/13

1/36

1/26

1/2.1

JSVR

Variable

Rate

1/11 1/9

1/12

1/34

1/22

1/1.8

Discrete

Position

Knobs

dials

1/9.8

1/10

1/48

1/43

1/1.8

Combined

Position

Anthropomorphic

harness

1/3

1/4

1/15

1/17

1/1.6

Figure 4. D/R Matrix for Behavior Elements

184
10 1

D/R

1/2.9

6 -

4

-

2 -

Degrees

D/R

1/1.4

D/R

3.4

KNOBS HARNESS DIVER

CONTROL SYSTEMS

Figure 5. Drill Angle Performance

185
The question remaining is how to utilize the methodology in the future to add

to the existing data base. One direct solution is to replicate the tests in this paper

and simply continue compilation of data. This is a viable solution where identical

facilities exist. A second approach is to utilize the methodology but change the

specifics of the tests. Resulting data, although not directly comparable, should be

of equal value, if interpreted properly. The methodology is summarized below to serve as a guide for developing similar tests.

Measurement and Testing Methodology, Rate and Position Controlled Manipulators ;

1. Determine system specifications according to the standard format.

2. Perform prognostic tests which have the following features:

(a) tests represent the entire range of typical tasks

(b) tests are performed under simulated conditions

(c) tests range from simple to difficult

(d) tests are selected to repeatedly require basic control responses

to be exercises in various combinations

(e) a reference set of data is compiled for continued comparison.

Reference data might best be recorded for man performing the

tasks directly to maintain a continuity of the human sequencing

of tasks, and to provide a common element for interpreting various

sets of data.

3. Evaluate and document data collected during prognostic tests:

(a) Times to complete tests.

(b) Times to perform typical behavior elements within those tasks.

(c) Accuracy and quality of test performance.

Utilization of this methodology to evaluate other types of rate and position

control manipulators (e.g., hot labs, space) is straightforward. The simulated

conditions change, the types of tasks change, and the reference data base changes.

These changes, however, do not affect the basic methodology.

186
IV. Considerations for Measurement of Force Feedback Systems

Evaluation of undersea remote manipulator systems with force feedback

capability is more complex than the evaluation of rate and position control systems.

The basic testing methodology, however, is essentially the same: system variables

are determined and a series of prognostic tests are conducted.

The task of determining system variables here is technically more difficult

than that for ordinary rate and position controlled manipulators. System response

must be measured in terms of both force response and position response. Additionally,

force and position responses must be measured from the master to the slave and from

the slave to the master in bilateral systems. Design alternatives of force feedback

systems are expanded due to the various system configurations and hardware concepts

developed. Table 2 presents typical variables and alternatives which are available.

Where definitions are similar or Identical with those in Table 1, they are so noted.

It is important to note that the variables listed in Table 2 are intended as an indication of the scope of variables and alternatives. The acceptance of standard

definitions and testing methods is required to permit meaningful comparisons to be

made between systems.

Prognostic testing of remote force feedback manipulator systems requires

increased data collection. Tests are chosen from time-motion studies of typical underwater work with particular emphasis on force control behavior required by the test.

Data collection during these tests reflects not only completion times and accuracy,

but also force control responses. Research presently being conducted by the authors

is investigating the effectiveness of performance measures such as integrated, maximum

and average forces exerted by the slave arm during selected force control behavior

elements. The objective of this research is to establish a data base and an effective

set of performance measures which will be meaningful in comparing system designs in

terms of operator performance and in projecting performance of similar systems in the

future.

An example of one type of test is given in the Appendix. The test in this case

is concerned with the production of electrical signals proportional to the torque

exerted by the slave (which in turn determines the torque applied to the master).

V. Summary

An overview of the testing and measurement methodology has been presented to

provide an understanding of its application to undersea remote manipulators. The

intent of this paper is to present the methodology for an open discussion of the merits

of the approach as it relates to a standard set of measures for remote manipulators

and programmable robots. The implications of the methodology are as follows:

1. System variable definition

Comparison of similar or diverse manipulator systems requires a standard method

of variable definition over the various systems. One set of definitions and

terminologies for all specifications should be applied across all the manipulator

design fields. A standard set of coordinate axes or conversion techniques between

dissimilar axes should be accepted across all manipulator design fields. Standard

testing methods for system response should be established across the various manipulator

design fields.

187
Table 2. Definition of System Variables, Force Feedback. Manipulator Systems

RESPONSE VARIABLES*

SAME AS IN TABLE 1

Rise Time (position)

Settling Time (position)

Dvershoot Time (position)

Slew Rate (position)

Time Delay (position)

Bandwidth (position)

Dead Band (position)

Droop: Compliance

Minimum Motion (position)

Drift (position)

Rise Time (force)

Settling Time (force)

Dvershoot (force)

rime Delay (force)

Band Width (force)

''linimum Force (force)

Drift (force)

Feedback Ratio: The ratio between slave and master forces. It is denoted as slave:master

3acklash: The measure of the force at the master (slave) which must be reversed

before the slave (master) force will begin to reverse.

Force to Move The force required to move at a constant velocity. A Figure of Merit

Dr Viscous is the force divided by the velocity.

Friction:

Effective The mass of the system sensed when operating the system.

System

Inertia:

It is recommended that these variables be documented for each of the 6 degrees of

freedom in polar coordinates. For bilateral systems these variables must be

documented for master-to-slave response and slave-to-master response.

188
Table 2. (Continued)

DESIGN ALTERNATIVES

Operational Envelope:

Degrees of Freedom

Anthropomorphic or Terminus Design

Motion Range

Linear Extension

Continuous Rotation

Tool Design

Master Controller

Position Control

Exoskeletal Strap On

Exoskeletal Harness

Terminus Grip

Master Controller Rate

Control

Joystick Controls

Variable Rate

Programmed Motions

Signal Conditioning and

Enhancement

SAME AS IN TABLE 1

Velocity Damping:

Friction "V reduction J Electronic \:

counterbalancing)

Computer with"

supervisory

control

Feedback Type

Visual/Auditory:

Tactile \:

indications;

Proportional

force

reflections

Examples

Position rate signals are utilized to provide damping.

Positive feedback reduces force to move.

Generation of signals to automatically support the dead weight

of the arm. Intelligent computer control of forces exerted by the system.

Examples

Force Feedback information provided on visual and/or audio displays.

Touch information presented to the operator via vibration or air

jet pulsations.

Proportion forces are produced at the master and the slave. Passive

at brakes, reactively via actuators or motors. Proportional force

sensation created via subcutaneous neural stimulation.

Force Detection Method Examples

Position ServoV'. error Force

transducei;rsy

Mechanical

transmission J Transducer \-

location J

Forces are generated in the master and slave proportional to the

position error. Forces generated are measured directly by transducers. Strain gages

or leds and photo cells.

Direct transmission of force via mechanical linkage or incompressibl

fluid.

Transduces one-to-one in joints or all loaded into one compact multi

axis unit.

189
System Performance Evaluation

The basic approach of the prognostic testing described in this paper is that of

time and motion studies (i.e., how long does each simple element of a complex task take?).

The number of behavior elements in the example research, although limited, imply that a complete breakdown of manipulator behavior elements will provide a standard for comparison

of the performance potential of various manipulator types. This method of cwnparison

was chosen over other methods for the following reasons:

(a) The data provide a direct measure of work performance.

(b) The data are collected in an undersea environment to directly account for

the complex man-machine-environment interface.

(c) The data are indicative of the ability to variously string simple tasks

together in the performance of a multifaceted task.

(d) The data are easily and readily comprehended by individuals asked to

design or select undersea remote manipulator systems.

(e) The data base documents man-machine performance differences as a function

of changing basic design aspects of the manipulator. Generally, the data are indicative of how well specific "types" of remote manipulators can be

utilized to perform work. As such, data need not be collected on every

system if data exist for an equivalent "type" of system.

(f) The data base serves as a reference from which the designer may project

the potential of a new system (provided data are documented for that type

of system).

3. Application of Methodology

The methodology described in this paper has been utilized to examine a selected

number of variables listed in Tables 1 and 2. Resultant data have closely interrelated

system performance in applied undersea contexts to various design alternatives and

response variable values. It is this methodology of interrelating independent engineering

variables with operator performance data which is offered towards the development of

performance evaluation standards for remote manipulator systems.

190
APPENDIX

Signals Generated

Purpose: The tests determine the ability of the system in producing signals proportional

to an external torque applied to an effector. The system is not under motion. Maximum

input torque, backlash, linearity, rise and settling times, and tracking are determined.

Procedure:

1. In this test, torque is applied to an effector and the input signal to its

bilateral pair effector is measured. The torque is added in 203$ increments of the design

payload until payload is reached. Torque is then reduced in increments to zero. Torque in the opposite direction is now applied in 2C% increments until zero torque

is being applied. At each increment, the proportional signal generated is measured.

Between increments, sufficient time must be allowed for the signals to settle to a fixed value. The proportional signal is recorded on a strip chart recorder to determine

rise and settling time. The loading procedure is repeated to determine repeatability.

2. Tracking of force variations is now measured using an identical set-up to Procedure 1.* 753$ of the payload torque is applied to the effector. An incremental

torque of 203^ payload is removed, the proportional signal measured. The 20% increment

is then re-added, signal measured. Continue removing and replacing increments of 403^ and 60^ of payload measuring the proportional signal at each iteration.

Data Format: Backlash is the amount the control must be moved in the opposite direction

before the commanded variable begins to respond. It may be a measure of force or position.

Example: The following curves were determined for a sample joint of the experimental

manipulator. The test configuration for Procedures 1 and 2 was as follows:

191
Note:

1. For bilateral force systems, data is also collected for the situation where

the master actuator is loaded and the signal to the slave actuator is

recorded.

2. The slave actuator is oriented so as to remove any torque produced by the

effect of gravity on the actuator mass.

The following data was derived from the example curves:

Hand Joint: Master

Generated Signal

Data

Source

Payload

Signal backlash

Full scale error

Repeatability

Signal Rise Time

Signal Settling Time

Tracking Error

20% Torque Increment

40% Torque Increment

60% Torque Increment

4.5 Ib-ft

.3 Ib-ft

10%

A%

.4 sec

.7 sec

10

0

5

Figure Al

Figure Al

Figure Al

Figure A2

Figure Al

Figure Al

Figure A3

Figure A3

Figure A3

192
J

o

2

Is

1 X 3 4- y

-f- 3

1

»

-2. ~T" 4

193
194
3.0-

2

41) J

>-

<

6.5-

V)

c

o

» Z 3 4. 5

195

5.4.3

CONTRIBUTIONS TO FORMING CRITERIA FOR THE EVALUATION

OF ROBOTS AND MANIPULATORS

M. Vukobratovic

It is in any case clear that forming criteria for the evaluation of robots

and manipulators depends on many factors. First of all, the fact should be admitted

that every criterion is of conditional character and hence has a limited value. Then

it becomes more evident that here cannot be spoken about some general criterion,

according to which the performances of various types of robots and manipulators would

be estimated. To begin with, one must mention robots and manipulators, which are used

industrially, in underwater explorations, on other planets and in outer space. Robots

are also present in rehabilitation activity of handicapped persons, and similar.

Each of these robot types requires careful analysis from the viewpoint of its

validity. It follows that the structure of the criterion itself must have various

marks in function of the mentioned classes of robots.

Something should be said already at the beginning, and this is that all robots

do not have, at the present state of development, full economic justification,

understood in the conventional way. Consequently, it is my opinion that the economic

index should not have some decisive influence on the evaluation criteria of robots and

manipulators, except in some cases of mass production applying industrial programmed

robots.

Because of this statement, let the structure of the evaluation criterion be

considered, or at least our standpoint be presented, what the same should look like

when the rehabilitation robots class is in question.

First of all, rehabilitation robots are in the initial phase of large-scale

application. It follows that there must be determined some parameters which would

participate in the evaluation formula of such robots. What are these parameters?

Even more, a unique criterion cannot be synthesized even for one class of robots.

Consider hand prostheses (under-elbow amputation) . There are some fifteen makes

existing on the world market today from the most perfected concerning imitation

of a human hand (fig. 1) to the simplest ones, performing the similar functions (Fig. 2). To what extent a criterion for assessing the validity of devices of that type can

lead to surprising results is amply illustrated by the fact that the prostheses of

the second mentioned version have found application with handicapped persons, whilt^ the

first ones practically stayed without regular users, in spite of the fact that they

were produced seven years ago. One is without doubt here: in the case of forming some criterion of validity post factum the sole parameter valuable is the acceptance of the

prosthesis by the patients-users. If the said criterion had been formed earlier, it

is probable that it would include such indeces as cosmesis, multifunctionality of

movements, reliability, etc . It is propable that the weight would be neglected, or at least its role underestimated. Experience has shown, however, that this factor is

very important, and that the weight of such a prosthesis should not be much greater

than the weight of the missing part of the human arm.

Let now let a more complex case of rehabilitation robots be considered, that of

a rehabilitation manipulator which is intended to enable a tetraplegic or very high

bilateral amputee certain manipulation activities. Here, too, we can judge

197
the quality of the assistive device only by the number of accepted ones. It must be

said here that none of some fifteen developed prototypes in many countries, have

profited of broad application. Why is this so? In any case not because it is not

possible to produce a dependable and precise manipulator, but for the reason that the

behaviour of man, coupled with an assistive device is practically unpredictable. Let

here one statement be stressed illustrating the impossibility to form some criterion

via technical parameters. Namely, it is unlikely that a handicapped person will really

use the manipulator if he has one healthy arm left. There is a limited number of

operations a person must perform with both arms simultaneously, when the class of

heavily handicapped persons is in question. That means, into the criterion for

evaluation of the rehabilitation manipulators must enter such a non-technical category

as indispensability and purposefulness . Only after that can enter some technical data,

as weight, reliability, precision, simplicity or the control system, energetic

autonomy, autonomy of using, total system cost , etc. Surely these technical data have

a great influence on acceptability of the device.

It follows that only when the human factor has been eliminated, i.e. his

attitude towards the active assistive device from the standpoint of its indispensability,

which for itself can frequently present a purely subjective category, one can proceed

to the judgement of the system from the standpoint of the above-mentioned technical

parameters.

?ig.l i.Iulti-functional pro- ?ig.2 Simple prosthetic hook

s the tic hand

198
The situation is similar in the case of the most complicated rehabilitation robot - the active exoskeleton (Fig. 3). How to fom some criterion, which weighs out the

performances of such a complex assistive device? When the youngest member of the family

of rehabilitation robots is concerned one must start again from the fact that this sort of robot has still not been applied and accepted broadly. For the moment handicapped

persons of the paraplegic type are still using the wheelchairs and from time to time leg

braces, which are blocking their flaccid joints to enable motion by means of crutches.

Here, as in the preceding examples, the patient has two alternatives for the same

activity. There exists big difference between the two ways of locomotion, but the common

feature is that they serve only to enable changing place in the environment. Both can perform this task in an non-anthropomorphic way , consuming great physical power,

especially in the case of the brace-crutches combination. Both are very limited from the

aspect of surmounting obstacles in the form of various terrain configurations. On the

other hand, active exoskeletons enable anthropomorphic (huraanoid) motion with minimal

participation of physical efforts from the patient's side and give possibility to surmount

various configurations of the living and working space (e.g. gait on staircases).

Consequently, it follows that as the first technical factor of qualitative

character must be adopted the factor or degree of anthropomorphicity . Directly to that

can be connected the factors of fatigue, reliability, dimensions (bulkiness) , weight , energetic and control autonomy , i.e. the degree of the same, then autonomy of using the

device (degree of autonomous "dressing" or "undressing" the exoskeleton) , complexity

of the control mechanism, degree of dynamic system stability , degree of unification of

exoskeleton construction (by means of assembling standard modules), and, finally, price

of system in function of the production series .

As can be concluded, with rehabilitation robots one cannot speak about some more

fixed exclusively technical criteria. The human factor is included here to such a degree

that the technical parameters alone have little influence on the final judgement of the

system.

The case is somewhat different when criteria of other type robots and manipulators

are concerned. All devices of these types present practically without exception purely

technical categories, and as such can be treated by technical criteria when evaluated.

Each class of robots, notably industrial type manipulators, have their specificities.

Let now some types of robots be enumerated and the specific demands discussed, imposed

by the same.

Rough division of these robots could be as follows:

robots for underwater explorations;

robots for unexplored environments, e,g, other planets;

robots for activity under irregular terrestrial conditions;

industrial robots of non-anthropomorphic type;

industrial robots of anthropomorphic type.

Without entering closer into the differences, i,e, their specificities, let some

common properties of the same be displayed, present to a more or less expressed degree

in concordance with the demanded performances. These same properties influence

implicitely or explicitely on forming the criteria for the evaluation of a rather broad

class of robots and manipulators.

Consecution of the discussed properties will not mean their rating in the criterion

for evaluation of the performances of robots and manipulators.

199
As one of the interesting properties could be underlied the degree or factor of

intelligence . Here it is intended to define the artificial intellect as a set of algorithms,

oriented towards performing some definite control task. It is evident that the

intelligence factor is directly dependent on the size of this set, which means there

exists no mystification in that notion. The robot is made capable to immitate certain

situations, memorized in the simulator, or being calculated in real time by means of a processor in the scope of the control system. The algorithmic level is connected to a set of various type sensors, from tactile and distancemeters , to force and pressure

transducers. The algorithmic complex incorporates the supplied information about the

environment by means of the sensors and the processor into the outputs (control signals),

defining the new state vector of the system (robot). According to our opinion, this

would be a sufficiently broad definition of intelligent robots from the technical aspect.

Examples of intelligent robots in the broader sense are rather few. As one of

such examples can be mentioned the six-legged walking machine (Fig. 4). It possesses

multi-level control, starting from the level of optimal trajectory choice, as the highest

one, to the level controlling placing of the feet to form a stable configuration of

the supporting polygon, as the lowest one. The robot inspects the environment, chooses

favourable passes, adapts itself to local obstacles on the chosen path and realizes a stable configuration of the supporting polygon. The machine is equipped with videosensors, tactile sensors and distancemeters. The processor gets the necessary information

and takes decisions about the further motion strategy.

The next property is directly connected to the first one, and is the adaptability

of the robot . Adaptability of the system can be defined in the broadest sense as capability of choosing algorithms for surmounting new situations, conditions and

working regimes. Consequently it is evident that adaptability is a necessary condition

for the existence of artificial intelligence and that the A.I., with respect to its

possibilities, is directly proportional to the broadness of the adaptability. Beside

the examples as represented by the six-legged machine, possessing a separate

adaptation level for solving the task of passing over obstacles of various forms in

the scope of its geometric dimensions and kinematic constraints, the property of

adaptation can be connected to some other robotic activities, too, as for instance the

process of pattern recognition.

200
Pattern recognition is today a largely developed scientific category, connected

to the theory and robot application in the broader sense. In this occasion we would

like to stress one dilemma concerning pattern recognition. This activity, evidently

initially developed with the goal of military objects (predominantly flying) recognition,

was transferred to some other cases. Thus in essence industrial manipulation was

started with the development of pattern recognition algorithms. There appeared even

some works connected with rehabilitation manipulation, where it could be easily proven

that such investigations have practically no sense. Not too great a technical sense

have also investigations of pattern recognition for industrial manipulators. What

would be profitable is if information about the pattern, or form, by means of algorithms

for pattern recognition, when every such machine is equipped with a TV camera, were

used for other purposes in the process of industrial manipulation. There exists some- thing else, which should be developed as well in rehabilitation robotics, and in

industrial use, and that i& the adaptive algorithms in the range of one class of objects

or holes. That means for some noted object one must dispose, on the basis of distancemeters and tactile sensors, along with the information about the forces between the

gripper (hand) and the object, also with algorithms capable to perform in the scope

of one characteristic class of objects (balls, cones, prisms, pyramids, openings of

various depths and forms) the necessary scalings with respect to geometry, distribution

of tactile sensors, values of forces in the contact points, the needed adaptation to

changed parameters of some object in consideration, which cannot be distinguished

precisely by the more rough video sensors. That means one handles here some "microrecognition" of objects or forms, in the general case for a certain class of the same, leading to full adaptation in the scope of a certain tolerance in geometry and the

control forces. Such property of adaptation can find its full justification in

in strial manipulation, as well as manipulation in the rehabilitation field.

The next property which could be included into the criterion could be

denominated the minimum of the control system . It is a very delicate question to

discuss this robot property as control process. Namely, it is known that certain

robot properties in the broader sense depend on mobility, dimensions, capability, even

the price of the control mechanism, the central part of which is represented by a processor in conventional cases. First steps in this direction have been made during

the last years. They reflected in passing over from general type computers to

specialized processors, made capable to perform some particular type of control task.

However, this is not enough to carry out on-line calculation of new dynamic states,

even at the present high level of technology development. As proof of this statement

can be cited the example of exoskeleton type anthropomorphic robot, dedicated to restoring

basic locomotor acts of handicapped persons. The fact is known that a robot of this

type is an inherently unstable configuration and that during gait the problem of dynamic

equilibrium must be solved continuously. Let for a moment be imagined that in real

time the solution of a system should be found, the same system consisting of differential

nonlinear equation with variable coefficients. Regardless of the adopted computer

language, the time for solving such a system is few seconds. It follows that every

pertubation (let it be large) would demand the mentioned time interval. This interval

can be shortened by means of special organizations of calculations on the hierarchical

principle, which on its side leads to a technical absurdity if it is known what is the

final use foreseen for that robot. In the same time the question can be posed, if the

biped robot can "wait" so long in some unstable pose for the processor to give the new

solution? Comment is not necessary here.

201
To surpass such or some similar situation it was arrived at the idea to prepares

solution, or nominal working regimes, for a set of initial conditions or characteristic

control parameters. Thus it has been arrived to the possibility, by memorizing offline calculated trajectories, to synthesize a simulator of the robot operation

in a certain range of characteristic control parameters. Such a control concept has

been realized for the first time in the case of biped gait control via the exoskeleton

(Fig. 3). Unacceptable duration of the calculation time intervals via some processor

is in this case reduced to time intervals smaller by a whole magnitude of order.

In the concrete case the time for choosing some new control parameters lies in the limits

of 0.1 - 0.2 sec, which is essential, if it is known that the half-period of an artificial gait step is approx. 1 sec. In order to clear this up thoroughly, the time

interval of 0.1- 0.2 sec. in fact represents the time needed for the choice of some corresponding set of memorized trajectories, at the basis of the measured state vector

due to perturbations, together with the reaction time of the system actuators. In some other types of robots, where the time of information processing is not so critical,

as in the preceding case, some half-way version of control can be adopted. Namely,

the simulator, or programmer of the nominal (stationary) working regimes, could be

broadened by some supplementary operative memory, capable to perform in some limited

scope calculations of the model, by which a certain flexibility of the control system

would be obtained.

The next important property of the robot influencing the evaluation of its

capability could be nominated structural kinematic adaptivity . This property is directly

expressed via the possibility, for instance when multi-legged walking machines are concerned, to modify the length of the "legs" according to the terrain configuration.

Such adaptivity would also reflect in the variation of some other parameters, as for

instance, step length (stride), vehicle track and velocity, introducing supplementary

(emergency) supports in critical situations of the terrain, and sim, (Fig. 4). As

direct consequence of this property, there appears a feature which could be called

multifunctionality of robot . It designates here capability of the robot to perform

several types of activity. So for instance a vehicle-robot with special wheels or legs,

if equipped with manipulators, has evidently greater possibilities. Such a vehicle

is not only used for reconnaissance, but can perform also some other actions, as for

instance detecting artificially impaired advancing (in military applications), or taking

samples of the soil (if unexplored environments are in question). A robot of that type

can have special manipulators - cutters, enabling to clear up trespassing of very dense

vegetation. Manipulators on flanks could load some cargo on the robot - transporter.

Imagination of such a complex multi-functional robot is given in Fig. 5. Such multifunctionality could be achieved with industrial robots, too, in the case of manipulators,

where they would be equipped with various types of terminal devices in order to be

capable to perform more complex manipulation tasks in some sequence and without delay.

Multifunctionality can be noted with underwater robots, too, where exploration of the

sea bed is performed in combined actions of a vehicle and manipulator (Fig. 6).

Goal of this discussion has been to prove, at least as opinion of this author,

to what extent the question of performance evaluation of robots and manipulators

presents a delicate matter. I am convinced that only some functionally simpler robot

types can be treated more precisely, with which their performance can be clearly

identified and some correlation established between the same and the factors on. the

basis of which this performance is being evaluated. Only in these cases there can be

attained somec^uantif ication of the evaluation criterion. In the other, more complex

cases, when still new unique realizations are in question, both of industrial and

rehabilitation robots, as already seen only some functional relations can be established

between the performances in the broader sense and some properties having larger

meaning. Hence such criteria, if they can be called that way at all, have only a qualitative character .

202
However, it is clear that discussion regarding this matter display much sense,

and they should be observed as actions, intended to create some order in some questions

of robotics, which evidently is in full growth.

203

APPENDIX 1

ADDRESS LIST OF WORKSHOP PARTICIPANTS

Dr. James Albus

Inst, for Computer Sciences

National Bureau of Standards

Washington, DC 20234

Dr. Demetrius G, Jelatis

Vice President and Director of Research

Central Research Laboratories

Red Wing, Minnesota 55066

Dr, Anthony Barberra

Inst, for Computer Sciences

National Bureau of Standards

Washington, DC 20234

Mr. Paul M. Lynch

C.S. Draper Laboratory

77 Cambridge Pkwy.

Cambridge, MA 02139

Dr. Antal Bejczy

Jet Propulsion Laboratory

4800 Oak Grove Drive

Pasadena, CA 91103

Mr. Gerald Malecki

Office of Naval Research

1800 North Quincy St.,

Arlington, VA 22217

Mr. Alan Case

Bldg. 37

General Electric Co,

Schenectady, NY 12345

Mr. Joseph F. Engelberger, President

Unimation, Inc. Shelter Rock Lane

Danbury, CT 06810

Dr, John Evans, Jr. Inst, for Computer Sciences

National Bureau of Standards

Washington, DC 20234

Dr. Jack G. Grundmann

Experimental Equipment Engr.

Oak Ridge Nat. Laboratory

Oak Ridge, Tenn. 37830

Mr. William Hamel

Oak Ridge Nat. Laboratory

Oak Ridge, Tenn. 37830

Mr, Dennis W. Hanify, Manager

ITT Research Institute,

Mechanical Systems Dept.

10 West 35th St.

,

Chicago, Illinois 60616

Mr. Richard E. Hohn

Manager Industrial Automation R&D

Cincinnati Millacron Co. Cincinnati, Ohio 45209

Mr, Douglas A. Morlock

Control Systems Support Branch

Technical Support Directorate

US Army Picatinny Arsenal

Dover, NJ 07801

Dr. Richard L. Paul

Artificial Intelligence Center

Stanford Research Institute

Menlo Park, CA 94025

Mr, Alan J. Pesch, President

Eclectech Associates

PO Box 178

N. Stonington, Conn. 06359

Professor Bernard Roth

Mechanical Engineering Department

Stanford University

Stanford, CA 94305

Dr. Andreas V. Rechnitzer

Office of the Oceanographer of the Navy

Hoffman Bldg,

200 Stovall St.

,

Alexandria, VA 22332

Mr. Bernard M. Sallot

Executive Director

Robot Institute of America

20501 Ford Road

Dearborn, Michigan 48128

205
Dr. Thomas B. Sheridan

32 Sewall St,

,

West Newton, MA 02165

Mr, Nicholas L. Shields, Jr. Essex Corporation

201 N, Fairfax St,

,

Alexandria, VA 22314

Mr. William Verplank

Room: 3-351, MIT

Cambridge, MA 02139

Dr, Jean Vertut

Commissariat de I'Energie Atomique

Department de Protection

Boite Postale 2 91190 Gif -sur-Yvette, FRANCE

Mr. Charles D. Wicker

Oak Ridge Operations Service

Holi Field

Oak Ridge, Tenn. 37830

ADDITIONAL CONTRIBUTORS

Prof. Y. Hasegawa

Waseda University

Tokyo 160 JAPAN

with I. Masaki

Kawasabi Heavy Industries, Ltd.

and M. Iwasawa

Oki Electric Industry Co., Ltd.

Prof. A.E, Kobrinski

Academy of Sciences of the USSR

ul Griboedova 4 Moscow Center 10100 USSR

Prof, M.S. Konstantinov

Head of the Central Laboratory for Manipulators and Robots

19 February St.

,

Sophia C BULGARIA

Dr. M. Vukobratovic

Institut Mihailo Pupin

PO Box 906

Beograd YUGOSLAVIA

206
APPENDIX 2 WORKSHOP PROGRAM

Thursday, October 23

4;;30 Registration

5::00 Reception

6::00 Dinner

8::00 Goals of the workshop, overview (Sheridan, Evans)

Summary Remarks: manipulator design and evaluation

Jelatis

Roth

Vertut

Discussion

Friday, October 24

8 : 30 Summary remarks : industrial automation (first session)

Engelberger

Paul

Case

Lynch

10:00 Coffee

10:30 Summary Remarks: space and undersea applications

Be jczy

Shields

Malecki

Rechnitzer

Pesch

Discussion

12:15 Luncheon

1:30 Summary Remarks: nuclear applications

Grundmann

Hamel

Verplank

Wicker

Discussion

3:30 Small group sessions

Saturday, October 25

8:30 Summary Remarks: industrial automation (second session)

Sallot

Hohn

Morelock

Albus

Barbera

10:00 Coffee

10:30 Reports of small groups and plenary discussion

12:00 Luncheon

1:00 Concluding discussion

3: 00 Adjourn

207

APPENDIX 3. PROCUREMENT SPECIFICATION No. XSP-239

Oak Ridge National Laboratory Date 5-20-66

Operated by

Union Carbide Corporation, Nuclear Division

MASTER-SLAVE MANIPULATOR -- STANDARD DUTY

1. SCOPE

1.1 This specification covers normal and extended reach Model-8 standard-duty

master-slave manipulators for remote handling of materials in radioactive

hot cells and caves.

1.2 Type, principal dimensions, and special requirements shall be as specified

in the attached Manipulator Data Sheet.

2. PERFORMANCE REQUIREMENTS

2.1 Tone Capacity - 20 pounds minimum in all positions and motions (except 18

pounds minimum in twist) at all points within the operating volume and at extreme Y position. Tong squeeze, 20 pounds minimum.

2.2 Operating Volume - As specified in Data Sheet.

2.3 Electrically Driven Indexing Speeds - Carrying the rated load specified in

paragraph 2.1, indexing speed shall be infinitely variable or step variable

In at least four steps, from zero to:

X motion: 3 1/2 degrees per second

Y motion: 10 degrees per second

Z motion: 2 inches per second

2 .A Balance and Frictioa

a. X Motion: With manipulator mounted on rollers and boom fully extended,

the force required to move the manipulator at a constant slow speed

shall not exceed 2 ounces, measured at the differential wrist joint

vith the manipulator near its rest position.

b. Y Motion: With boom fully extended, the force required to move the

manipulator at a constant slow speed shall not exceed 2 ounces, measured

at the differential wrist joint with the manipulator near its rest

position.

c. Z Motion: The force required to raise or lower the boom at a constant slow

speed shall not exceed 12 ounces. The difference in force to raise and

lower the boom shall not exceed 3 ounces.

d. Elevation Rotation: The torque required to raise or lower the hand and

tong shall not exceed 18 inch-ounces, measured about the differential

gear axis, excluding the torque created by the weight of the handle

and tong.

209
e. Twist Rotation: The torque required to twist the handle and tong shall

not exceed 18 inch-ounces

.

f. Azimuth Rotation: The torque required to rotate the manipulator in

azimuth shall not exceed 21 inch-ounces.

g. Balance: With master and slave arms parallel, the counterweights shall

be adjusted so that, for all positions of the Z motion, the manipulator

will either retain any angular position (in both the X and Y planes)

up to 30 degrees, or return to vertical (within + 10 degrees) in no less

than 5 seconds

.

2.5 Rigidity and Lost Motion - With booms fully extended, extension of extended

reach fully retracted, and tong anchored to prevent motion in any direction:

a. Maximum deflection with 20 inch-pounds torque applied to hand about the

longitudinal axis of the boom for azimuth and about the differential

gear center for elevation and twist:

Azimuth : 2 degrees

Elevation: 3 1/2 degrees

Twist: 3 3/4 degrees

b. Maximum deflection with 20 pounds force applied perpendicularly to the

boom axis at a point 90 inches from the shoulder pivot:

X motion: 2 1/2 inches

Y motion: 3 1/2 inches

Z motion: 1/8 inch

2-6 System Slack and Operating Smoothness - With the tong carrying a 400 ml

beaker filled with water within one mm of the top, a competent operator shall

control the tong to describe an approximately square pattern, 2 feet on a side, in an approximately horizontal plane, starting from rest and accelerating to approximately the full speed specified in paragraph 2.3 on each side

of the pattern, without spilling more than 10 ml, as determined by weighing

the flask before and after the test. If electrically driven indexing is

specified in the Data Sheet, the test shall be repeated with electrically

driven indexing.

2.7 Hand Rigidity - With a block installed in the track to limit ratchet

motion so that the finger tubes are restrained in an approximately parallel

position, and with one finger tube rigidly anchored, a 10-pound load applied

perpendicularly to the other finger tube shall produce a maximum deflection

of 7/32 inch;, a 24-pound load shall produce a maximum deflection of 5/16

Inch; as measured by the distance between the finger tubes.

3. EQUIPMENT REQUIREMENTS ^

3.1 Power Supply - A multistep or infinitely variable speed-control rheostat

and extension cord for operation from a 110-V, 30-amp A.C. receptacle shall

be provided. Cap shall be NEMA Type 5-15P in accordance with NEMA Standard

WDl-1965.

3.2 Hand

a. Ambidextrous, ratchet locking with ratchet release and lock-out, with

totally enclosed wrist joint, pistol grip handle, and closed finger

tubes. When electrically driven indexing is specified a finger controlled

trigger switch, operable without removing the operator's hand from the

handle, shall be provided for indexing speed control. Grip sensation

shall be proportional to tong squeeze.

210
b. Indexing selector switch shall be mounted on the rear of the boom no more than 8 inches above the wrist. Selector switch shall have off

position and one position for each electrically driven motion, with

indicator light(s) to show which motion is in operation.

c. Hand shall be wired to connections within the boom by means of a male

and female electrical connector with locking nut, one member of which

shall be rigidly attached to the boom at a point no more than 4 inches

above the wrist.

3.3 Tone - Remotely removable Argonne Laboratories RDC type with non-replaceable

fingers. Coiled tension springs are preferred for finger opening; maximum

expansion of coil spring shall be 1/20 of the relaxed spring length. If

torsion springs are used, maximum rotation shall be 20 degrees. Tong castings

shall be Almag 35 or ASTM B108, Grade GM-70b. Springs, pivots, and side links

shall be stainless steel.

3.4 Cable Tension - Azimuth cables shall have spring-loaded dash-pot tension

devices mounted between the cables and the adjusting turnbuckles. Azimuth

cables shall be adjusted to 8 pounds tension, + 1/4 pound, before making

performance tests. Cables shall be stainless steel aircraft type cable.

All cable adjustments shall be on the master boom.

3.5 Tapes shall have no visible slack when prestressed to operating tension.

Twist and elevation tape tension shall be 12 pounds + 1/4 pound for performance tests. Tapes shall be 3/16 inch X 5 mil Elgiloy or CRL Flexendur.

All tape adjustments shall be on the master boom. Tape pulleys shall be

crowned to minimize tape and pulley wear.

3.6 Booting - Construction shall permit booting of the slave end; boots will

be furnished and installed by the Company at the installation site.

3.7 Locks - When motion locks are specified in the Data Sheet, a minimum number

of locking clamps to provide the locking actions specified shall be furnished.

All locking clamps shall be located on or adjacent to the master boom within

8 inches from the bottom of the non-telescoping portion of the boom. Clamps

shall lock the specified motions with tongs unloaded and with tongs carrying

the full load specified in paragraph 2.1.

3.8 Gears and Pulleys - Master and slave wrist drums and gears shall be stainless

steel. Other gears and pulleys shall be chromium plated carbon steel or stainless steel. Master arm boom tube rollers shall be nylon.

4. TEST AND ACCEPTANCE

4.1 With his bid. Seller shall furnish three copies of:

a. A certified test report showing performance characteristics of a manipulator

of the same type, showing values for all performance requirements specified

in paragraphs 2.1, 2.3, 2.4, 2.5, 2.6, and 2.7.

b. A schedule and procedures for testing to confirm compliance of the completed

manipulator with the requirements of Section 2, including a description

x>f measuring devices, including sensitivity, to be used for acceptance

tests

.

4.2 Seller shall assemble, adjust, and test the manipulator prior to shipment and

shall notify the Company at least 10 working days before the start of test to permit witnessing should the Company elect to witness the tests. The Company

may elect to accept a certified test report in lieu of witness tests. In any

event, the Seller shall submit a certified test report for Company approval;

test report must be approved by the Company prior to shipment.

211
4.3 .Final, acceptance shall be at the installation site at Oak Ridge, Tennessee,

-following inspection, installation, and operational testing in accordance with

the procedures furnished by the Seller.

5. MANUFACTURER'S DATA

5.1 Seller shall furnish manufacturer's data, test procedures, and test reports as specified in attached Company form UCN-3296.

MANUFACTURER'S DATA REQUIREMENTS

Oak Ridge national Laboratory

VNION CARSIOE CORPORATION

•UClCtI DlflSIOII

WORK REQUEST

SPEC. NUMBER XSP-239

REQ. NUMBER

P. O. NUMBER

ITEM:

MASTER SLAVE MANIPULATOR

9 /,

REMARKS

Assembly drawings

Electrical and control schematics

Electrical wiring diagrams

Each part shall be described

Parts list, including recommendations for and identified to permit

spare parts to be stocked.

procurement from the

original manufacturer.

Operating and service manual

Outline dimension sketches

Operating characteristics and test report

Schedule of materials

Test procedures and schedule of tests Approved by Company

prior to shipment.

Acceptance test report

Dimensional sketch showing coverage of slave 3

arm

212
MANIPULATOR DATA SHEET Requisition No. Requisition Date_

Requisitioner

MODEL 8 MASTER-SLAVE MANIPULATOR - STANDARD DUTY XSP-239

Mounting wall Mounting Sleeve Barrel Pivot to Pivot

Installation Thickness 36 in. diameter, 10 in. Length 78 in.

Dimensions + 1/16 in.

Height of through-tube

axis above operating

floor 127 + 5 in.

Height of through-tube

axis above cell floor 148 + 5

Overhang

Operating Side 24 in.

Overhang

Cell Side 18 in.

Maximum vertical projection of

counterweight above master pivot 21 in.

Shielding

:

Lead Equivalent

Max. Open Area

m.

%

NOTE:

Operating volume is outlined by the areas indicated by cross marks.

Cell Floor SECTION AA

72" .36"

Cell

Ceiling

»

.

•''.>.'

• 'v'.'b

72"

Operating Area

Operating

Floor

187'

104"

oor —t ii21"

SECTION BB

Operating Volume

One or the other equal reach tongs

shall be operable in any position

or motion at all points within the

MSL - Minimum Slave

arm length See Sketch

X See Sketch

Y See Sketch

Z See Sketch

Other dimensional requirements

Separation See Sketch

Special

Features

Other

Requirements

Extended Reach [7] Mounting: Roller Tube Q ; Universal Roller Mount Q

Electrically Driven Indexing: X [7] ; Y [7] ; Z[7]i Lateral Rotation

Motion Locks: X0; Y [7] ; Z [7] ; Twist [7]; Azimuth [7] ; Elev|7] Squeezel?]

Tong replacement jig required [7] ; Hood adapter and fixture required | [

* Roller Track Mounts

213

APPENDIX 4.

Japanese Industrial Robot Association Standardization Plan for Industrial Robots

reprinted from Industrial Robot , Intl. Fluidics Services Ltd., Carlton, Bedford,

MK 43 7JS England, March , 1975 (with permission)

A Standardisation Plan for I Rs

Editorial Note

:

It was thought that the Japanese draft proposals

for standardisation would be of interest to readers. The more that common terminology and standards are discussed and adopted the more likely will it be that Industrial Robots will spread their irifluences. Some

dialogue is therefore necessar\' and it is hoped that the

following proposals will provlke comment from

readers . Any commeius should be sent to:

Ivlr. Kanji Yonemoto

Executive Director J.I.R.A.

KikaishinJco Biiildicg 3-5-8 Shibakoen Minato -ku TOKYO

Japan

1 . Reason for and Purpose of the Study

The shortage of labor, a sharp increase in wages, the need for improvement in v/ork place en- vironments and human welfare in Today's industrial world have drastically enhanced the need for labor saving by safe automated systems. Therefore the rapid development of industrial robots where research

and development and the development of the technologies necessary to utilize them can lead to rapid progress

in application.

The rapid growth and increasing importance of

industrial robots as mentioned above deserves special

attention being paid to their standardization thus form - Ing a basis on which the need for such studies can be

explained :- 1) As it wiU be almost impossible to standardize them after they will have been widely applied, and if such standardization will be forcibly imposed then, the growt; of the industrial robot manufacturing industry as well as Japan's in- dustrial structures could be seriously affected.

2) The standardization of industrial robots will

lead to a more applicable operation of such

robots and contribute to the safety of workers.

3) Such standardization will reduce maintenance

costs of industrial robots and improve Dheir maintenance

.

4) Such standardization will improve and stabilize the quality and performance of industrial robots and reduce production costs.

5) Such standardization will enable the industrial robot manufacturing industry to establish a Arm

basis for specialized production of parts and complete systems.

6) Such standardization will enable industry to allocate its targets for technological develop- ment, leading to further technological progress.

7) The standardization of industrial robots will enable Japan's industries to orient themselves toward labor saving. Therefore, such standardization should be examined on a national basis

.

In view of such a need for standardization, this study will aim to improve and stabilizing the quality and performance of industrial robots, reducing production costs, establishing systems for specialized

production, improving their maintenance, as well as

achieving labor safety and advanced technological

development . By doing so, the study is intended to contribute widely to labor saving, by automation and promote safety in the industrial world

.

2 . Period for the Study

From April 1974 to March 1977 (to be conducted for three consecutive years from fiscal 1974).

3 . Contents of the Study

Ouring Fiscal 1974:

(a) Study on standardization of fundamental

terminology and figure signs or symbols.

(a)-l Extraction of fundamental terminology

concerning hardware, functions, and

systems, their systematization and definition . (a) -2 Extraction of figure signs and their systematization

.

(b) Study on various actual functions and analysis

of fields and ranges of actual utilization.

(b) -l Study on actual working functions such as moving functions, holding functions, locomotive functions, etc . as well as

control functions such as moving control

functions, learning functions, information exchanging functions, sensing functions, etc

.

(b)-2 Analysis of fields and ranges of actual

utilization.

215
(c) Study on applied technologies

The study will be conducted so as to understand

the optimum relationships for the function of robots and to be carried out (to find optimal

conditions for cost performance) by selecting four working processes such as cutting, punching, etc.

During Fiscal 1975:

(a) Complementary study on fundamental terminology and s>'mbols for industrial robots and a study on related terminology

(a)-l Complementing fundamental terminology and extraction, definition and systematization of related terminology.

(a)-2 Working out a draft for unifying figure

signs or symbols.

(a) -3 Study on and extraction of letter signs.

(b) Study on standardization of functions

(b) -l Complementary' study on various actual

functions and complementary analysis

of fields and ranges of actual utilization. (b)-2 Study on standardization of testing methods

(b)-3 Classification of functioiis and study on

indicating methods.

(b)-4 Study on methods for indication functions, and study for standardization of functional and electrical couplings, interchangeable

adaptors for intercha»-gable wrists, and elements consisting of robots.

(b) -5 Studies on electrical signal systems and

standardization thereof between robots and

control devices, robots and machines, and robots and work . (c) Study on applied technologies

(c) -l Study will be conducted for grasping

optimum relations between the functions

of robots and matters to be handled (to find optimum conditions for cost performance) by selecting five to six working

processes which were not selected in the study during fiscal 1974.

(c)-2 Study on standardization of safety measures

(c)-3 Study for standardization of minimum

necessary functions of robots in accordance with their working environments

(for heat resistance, dust prevention,

etc).

rXiring Fiscal 1976:

(a) Study on robot modules

(b) Overall coordination of study results conducted

in the first and second years

4)5) Committee for Study on Functions (20 memh>ers)

Committee for Study on AppUed Technologies

(20 members)

4.

5.

Organization to Conduct the Study

]ap>an Industrial Robot Association

Structures of Study Committees

In order to conduct this study, the following

general committee and four sf)ecialized committees

will be established:

(1) General Committee for Study on Standardization (Main Committee) (30 members)

2) Specialized Committee on Study (20 members)

3) Committee for Study on Standardization of Terminology and Signs (20 members)

Budget for Study

Fiscal 1974

1975 1976

¥15, 000, 000.

20. 000, 000.

15, 000, 000. Toul:

£21, 000

£28, 000 £21,000 £70,000

¥50, OOP, OOP

Terminology and definitions for Iixiustrial Robots

.

I. Terminology for classification of industrial robots

.

(Classified by sequential information)

(1) manual manipulator : See later.

(2) single purpose : Manipulator the constit- ution of which fixes its function. It cannot be modified into another

robot by a supplementary

control unit.

(3) repeatable robot : Manipulator which repeats its function in compliance with the pre -memorized program

.

(3)-l single programmed : fixed program is defined

repeatajjle robot as a program of working

cycles tnat cannot easily be modified (example:

the robot programmed

with a cam or relay circuit) variable program 1 = program of the working

cycle can be changed

easily, and the working

sequence depends on its program . (example

:

the robot programmed

with pin-board, tape or cards).

variable program 2 = program of the working

cj'cle can be changed

easily, and it has

facility for branch

functions in its cycle,

(example: the robot programmed with pro- grammable logic controller)

(3) -2 multi -programmed : one that has more than repeatable robot two working cycles and

the command program

can select an optional

cycle, (example: the robot programmed with

9 mini -computer or programmable logic controller)

(4) intelligent robot : Robot which can decide its behavior by it- self through its sensing and recognizing capabilities .

216
manipulacor "Nlanipulator " has a

function similar to

that of human upper

limbs and has itself more than two of the motion capabilities such as revolution,

out -in, up -down,

right -left travelling,

swinging or bending, so that it can spatially

traMport an object

by holding, adhering to. and so on.

(5) robots with ether coordinates types

(Classified by input information and teaching)

(1)

(2)

manual maniDuLator

:

sequence robot

(2)-l

(2)-2

(3)

fixed sequence

robot

variable sequence

robot

playback robot

(4)

(5)

N.C. robot

intelligent robot

(Classified by motion form)

(1) Cylindrical : coordinates robot

(2) polar coordinates

robot

(3) Cartesian

coordinates robot

(4) prosthetic robot

Manipulator whose arm's

operate in a universe

defined by other sets of coordinates

.

(Classified b\" degrees of freedom)

(1)

(2)

(3) Manipulator which is directly operated by man.

Manipulator the working step of which operates sequencially in compliance with the preset procedure,

conditions and posit- ions . Sequence robot as defined above, the preset

information of which

cannot be easily

changed

.

Sequence robot as defined above, the preset

information of which can be

easily changed. At first, man teaches the manipulator the working

procedure through operating it, so that the robot it- self memorizes the procedure, then it can continuously repeat its operation. Manipulator which can execute the commanded operation in compliance with numerically loaded working

information about position, see previous page.

Manipulator whose arm's

operate in a universe defined by cylindrical coordinates . Manipulator whose arm's

operate in a universe defined by polar coordinate system

.

Manipulator v. hose arm's

operate in a working uni- verse defined by orthogonal coordinates

.

Manipulator which has an

articulated arm

.

robot with one de- gree of freedom

robot with two de- grees of freedom

robot with n de- grees of freedom

Manipulator which has the functional degree of free- dom of 1 . (note: open -shut

of the hand and on -off of the vacuum cap are defined as one degree of freedom)

Manipulator which has the

functional degree of free- dom of 2

.

Manipulator which has the

functional degree of free- dom of n.

(3)

(4)

(5)

medium scale robot

small scale robot

micro(mini) robot

(Classified by operating space and holding weight)

(1) giant robot : Robot which can transport more than 1000 kg.

(2) large scale robot : Robot which can transport 100 to 1000 kg, or the vol- ume of whose working space

is more than 10 m.

Robot which can transport

10 to 100 kg, or the volume

cf whose working space is

1 to 10 m.

Robot which can transport

0-1 to 1 kg, or the volume

of whose working space is 0-1 to 1 m.

: Robot which can handle

less than 0-1 kg, or the volume of whose working

space is less than 0-1 m.

II. Fundamental terminology for the function of an

industrial robot working function : Functions in the working

operation of robot,

moving function : Functions in spatial motion such as of arm or wrist.

holding function : Functions in grasping and

holding actions of fingers locomotive function : Functions of pedestals or wheels which enable the robot to travel. arm : Its purpose is to move the hand which holds the object. unprosthetic arm : .^rm which has no articulation, (example: arm

which has only linear motion eg. a hydraulic

in/out actuator

.

prosthetic arm : Arm which has articulat- ions . w'rist : It locates at the tip of arm

and its function is to hold

the hand. hand : Both fingers and thenar

.

finger : It is a part of the lund.

217
control function

moving control

function

playback

motion control

sequencial mode

control teaching

teaching function

teaching methods

direct teaching

indirect teaching

method

operation method

for teaching

lumped teaching

method

separated teaching

method

memory

memory storing

method

lumped memory

storing method

separated memory

storing method

position memory

sequencial mode

memory

and its function is to grasp and hold the work . (As some work needs to be

held by otiier means than

grasping, the form of the finger should lie clearly

described). Functions in the control

of robot

.

Functions which control

the working operation of robot to be effective. To read the recorded in- formation according to the demand, so as to trans- mit certain commands

to the actuator

.

Control functions mainly

in the mechanical field. Functions in the control of

the operation sequence. Recording of the information by man which is required to operate the

robot. Functions in teaching the working program

.

Methods of information

handling at the time of teaching. To teach the working in- formation to the machine

by directly of)erating the robot

.

To teach by inputting the working information in the form of numerals or language

.

Methods in teaching

operation. To teach the whole in- formation at each working step in one lot. To teach each information such as positions, sequence or speeds

separately

.

To retain the taught in- formation for a required

period. Methods in the storage

of taught text

.

To store the whole in- formation in one memory device

.

To store the information

separately in more than two memory devices. To memorize the positions to stop or change

actions of each axis,

(example: potentio- meter method)

; To memorize the operational step sequence of each axis . (example

:

pin -board method)

measuring and : recognizing capdbility measuring capability:

internal measuring :

external measuring

recognizing capability

shape recognition

speech recognition

'Functions (Capabilitie

IXjnctions* in the mi.asur(jmcnt and tlic recognition of the robot. Measuring functions of robot

.

Functions in measuring

the state of the robot it- self. Functions in measuring

the conditions of the object. Functions* in the recognition system of the robot

.

Functions* in the recognition of the shape of the

object

.

Functions* in the recognition of speech

.

s)

111 . Fundamental terminology on characteristics or

capability of an industrial robot. up -down turning of the arm

up -down of the arm

in -out of the arm

right -left turning

of the arm (rotating

of the arm)

right -left traverse

of the arm

revolution of the

bending of the hand

(swing of the hand)

revolution of the hand

grip, clamp

operating space

operating distance

operating angle

travelling performance

maximum speed

bp -down turning of the arm in the vertical plane

of robot

.

Up-down parallel movement of the arm in the vertical plane of robot. Movement along the longitudinal axis of the arm . Turning of the arm

around the vertical axis.

: Right-left parallel movement of the arm in the horizontal plane of robot

actuation.

: Revolution of the arm

around its longitudinal axis

.

: Swinging of the hand alone around the wrist

.

: Revolutionary movement

of the hand relative to the arm

.

; Open-and-shut function to hold the work

.

: Volume space where the robot can operate.

: Motion range of the movement in each degree of freedom

.

: Angle range of the movement in each degree of freedom

.

: Travelling functions of the robot with its pedestals or wheels

.

: The maximum velocity of

the given part of robot under the given conditions,

(example: no load maxi- mum speed, rated load maximuni speed -part and

condition should be clearly

described-).

218
positioning accuracy

repeatability

playback accuracy

degree of freedom

freedom of motion

memory capacity-.) storage capacity ) number of setting

points external synchronizing

Interlock signal

: Degree of agreement betv.een the commanded

position ar.d tlie actual

position, (example: -axis ±E/L -L is stroke-).

; Accuracy in reproducibility.

: Difference betv-een teaching and play back posit- ions.

: Measurement of the flexibilat%' in the control or

the operation,

(note : the Qexibility in the control is, for ex- ample, storage capacity- of position, time and sequence)

: Number of linear movements, & revolutions

: Amount of the loadable information.

: Number of the settable points in each axis

.

: Signal which is transferred betw-een the robot and other machines so

that the robot is to be synchrorized with them

.

: To s\--chronize m.ore than two signals so that w hile one operates the other is not to operate whenever

any input is accessed. The maximum w eight of the work which the robot can handle in its normal

performance

.

Program which is to be

repeatedly executed by

the main program

.

Function which yields more than two programs

to be selected. To corxrol the robot by

recording the operation

path in a continuous for- mat, (CP. control) To control the robot by

recording the operation

path in the form of the coordinates of finite positions. (P.T.P. control)

Figure signs. Symbols

First proposal for questionnaire on figure signs and symbols.

(I) One can roughly classif>' the figure signs and symbols relating to industristl robots as follows.

(1) The figure signs and symbols relating to industrial robots that are used in the flow - charts for manufacturing process.

(2) The figure signs and symbols relating to industrial robots that are used in the layout

of m.anufacturing process

.

(3) The figure signs and symbols showing tlie

holding weight,

(pay load)

sub -program

branch function

contimious path control

point to point

structure and the function of an industrial robot itself.

(4) The figure signs and symbols relating to peripheral equipments.

(II) The present questionnaire is connected to (I)-(l) and (I)-(2) among what were mentioned above, and the following is the proposal made by the committee on symbols. Please let us know your remarks on this proposal and if there are some

figure signs or symbols relating to (I)-(l) or

(I)-(2) which have been already used in your company, show us them also.

(III) Proposal made by the committee on symbols

(1) Figure signs for flow -chart.

(i) Figure signs of industrial robots entered

in a flow-chart of manufacturing process .

1 : Symbols of coordinate system of arm are

entered. (In the case of prosthetic t^'pe its symbols (unfixed) are entered).

2: Mechanisms and functions required with this robot are entered. (Or only the symbol of the robot is entered).

Figure sign of driving source of arm

(Fig.l-c) is entered. Figure sign of driving source of wrist

(Fig.l-c) is entered.

Figure sign of driving source of finger

(Fig.l-c) is entered. (However, in the case where the driving source is common to

all, only 3 is entered . If the driving source

of the wrist is in common with that of the arm, 3 is entered as the representative of those two. Similarly, 4 is entered if the driving source of wrist is in common with

that of the finger, and 3 is entered if the driving source of arm is in common with that of the f nger).

6: In the case that there are several arms, arm

signs as m.any as their number are entered.

7: This indicates a control system, where required functions are entered. (Or only the symbol of the control system is entered).

If the articles mentioned above are too m.any, or

if entering of the articles is too complicated due

to the size of the system, only the symbols of the robot and the control system are entered and the

details are collected in an additional table

.

(See Ex.l-b)

(ii) AUied symbols

(a) Industrial robot LR

In the case chat there are n robots in the flow -chart, lR-1, IR-2, ---IR-n,

(b) Control system for robot COXT. CONT-1, CONT-2, ---CONT-n

(c) Symbols relating to coordinate system

The coordinate systems of industrial robots' arm are fixed as in the following figures.

The swing axis of a robot's arm is regarded

to be the Z-axis. The origin 0 is fixed on

the Z -axis

.

The original line coincides with the neutral

line of the arm

.

219
Positive values for 6 are measured clockwise toward the direction of positive Z. (Right- hand system) Zo is tJie height of the origin from the datum

surface of the robot.

Polar coordinate system whose origin is the swing axis of tlie arm and whose original

line is the neutral line of the arm

.

Zo is the height of the origin from set surface of the robot

.

Polar coordinate system

In the case of an orthogonal coordinate system,

a right-hand system whose origin is fixed on the robot

is used and its X-axis is coincidal with the shaft line of the arm . Zo is the height of the origin from the datum surface of the robot.

Svmbol Coordinates

CvLindrical coordirate system C r, e, Z, Polar coordinate system P r, 9, Q, Orthogorul coordinate s\'Stem R X, y, z, (Prosthetic type) unfixed Note . In the case of combinational Di^pe, the additional coordinate is suffixed by a small

letter to the symbol of the main coordinate system

.

Example: In the case where the Z-axis is added to the Polar coordinate system, Pz

(d) Symbols relating to degrees of freedom Freedoms of Freedoms of Freedoms of arm motion wrist motion hand (finger) motion

F: + / + / +

Optional degrees of freedom are entered

( ). Each number of freedoms is entered in Example: F: 3+(l)/2/l

(e) Symbols relating to paths CP: Continuous Path PTP : Point -to -Point Example for indication of (1)

Industrial Cylindrical The range needed for the r axis robot coordinate is 700 2000. system The range needed for the 9 axis

is -H20°- -100". The range needed for the z axis

is 0 100. Zo is 700. There is only one arm hydrauUcally driven. The freedoms of the wrist are:- rotation and up -down (option).

It is hydra ulically driven. The fingers are driven pneumatically . Onoff grip

.

The path is Point -to -Point.

(2) Figure signs for layout

These arc th_- figure signs of robots used in a

layout of mjnufjcruring process, and the chief purpose is to show the whole range of motion of the robot finger

.

(i) Cylindrical coordinates type ^max • Length between the origin and

the finger tip when the arm is

fully extended

.

^min • Length between the origin and

the finger tip when the arm is

fully retracted. +9 : The maximum swing angle of

the arm in the positive direction.

- 9 : The maximum swing angle of the arm in the negative direction, +z : The highest position of the arm

.

-z : The lowest position of the arm

.

20 : Height of the origin from the set surface

.

rbmax Ths most protruding position of

the back end of the arm when

the arm is fully retracted. The range of motion is described with a fiiU Uns. The dangerous region is described with a broken line

.

(ii) Polar coordinates type ^max- 'min- '^bmax ^^e defined

in the same way as (i). + Q ; The maximum value of Q in the

positive direction.

- Q : The maximum value of Q in the negative direction.

(iii) Orthogonal coordinates t>'pe

Example for indication of (2)

r

0: ±120"

z: 0-500

Zo: 300

rb max : 600

Space for remarks

Please write down in the following space the figure

signs on (2) already used in your company. Example 1

Please write down in the following space the figure

signs and symbols on

(1) already used in your company

220
^4a^1e of company

LX.'partnicnt for Address

correspondence N;imc of Dep. tcl.( ) Writer of tins Name

cluestionnaire MEASUREMENTS OF CHARACTERISTICS OF INDUSTRIAL ROIXJTS

OBJECTS

(1) Robots witli electric drives, 1 frecdom(arm)

3 types

(2) Robots with pneumatic drives, 3 freedoms(arm),

cylindrical coordinate, 2 types

(3) Robots with hydraulic drives, 3 freedoms(arm),

cylindrical coordinate, 2 types

(4) Robots with hydraulic drives, 3 freedoms(arm),

polar coordinate. 2 types

All the Industrial Robots described here are on the markets, and their type is point-to-point.

ITEMS OF MEASUREMENT

(1) Checking of dimension; Data of catalogues or

technical reports are checked.

(2) Operating space

;

(3) Operating time; Operating time of linear movements are measured. The results are shown in the Figure. In this measurement, the "stop action" is not clearly defined.

(4) Acceleration;

(5) Accuracy of positioning; In cacli case, measurements should be repeated until the randomness of data are confirmed. Parameters used here arc as follows: stroke: full, half quarter, etc. load: full, half, zero, etc.

(6) Resolution; Factors described below are ex- amined,

the minimum of setting distance in operating,

the minimum of inching distance available

(7) Drift; deviation distance in "stopped state".

(8) Overrun; The time intervals between "command"

and "stop" in emergency stop-motion are measured.

(9) Holding ability in "rest state "; The travelling distance of arm when all parts of the Industrial Robot are in "rest state".

ITEMS OF PENDING (because measurements are too

difficult or way of measurements are not decided yet)

(1) Operating time in non-linear movement cases;

(2) Warming up time

;

(3) Exchangeability; exchangeable to another or not.

(4) ReUabiUty against atmosphere

;

(5) Convenience; Whether the Industrial Robots are

well adopted for use.

(6) Noise

;

(7) EXirable year

;

(8) The actions caused by electric power failure;

221
NBS-114A (REV. 7-73)

U.S. DEPT. OF COMM. 1 . PU B L IC A TION OR R F. POR T NO . 2. Gov't Accession BIBLIOGRAPHIC DATA No. NBS SP-459

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

Perfomance Evaluation of Programmable Robots and

Manipulators — Report of a Workshop held at Annapolis,

Maryland October 2>25, 1975

5. Publication Date October 1976

6. Performing Organization Code

7. AUTHOR(S)

Edited by Thomas B. Sheridan

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No. 6006111

11. Contract/Grant No. 5-35922

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Under Contract 5-35922 with

Office of Development Automation & Control Technology

Institute of Computer Science and Technology

National Bureau of Standards, Washington D. C. 20234

13. Type of Report & Period Covered Final

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

Library of Congress Catalog Card No. 76-600057

16. ABSTRACT (A 200-word or less factual summary ol most significant information. If document includes a significant bibliography or literature survey, mention it here.) The Workshop brought together representatives of industry, academic institutions and

government agencies, including the potential designers, suppliers and users of a new generation of manipulators and robots which include varying degrees of control by both

people and computers. The Conference was motivated by the lack of common bases for com- paring one such device with another in terms of performance, or one task with another

in terms of how well a given device will perform it.

The Workshop concluded that there is a need for (1) common definitions of many terms

which now are the source of pervasive confusion, (2) common test codes, (3) checklists,

guidelines, and specifications to help users and suppliers better communicate with

one another, and (4) common tests for demonstration and exhibition of new research and

development in this field. Conference participants emphasized that once these needs were met to allow communication in the field, actual performance testing should be left

to the user and supplier in the free marketplace.

17. KEY WORDS (six to twelve entries; alphabetic al order: capitalize only the first letter of the first key word unless a proper name: separated by semicolons)

Guidelines; industrial robots; manipulator; performance evaluation; programmable robots;

and specifications.

19. SECURITY CLASS

(THIS REPORT)

UNCL ASSIFIED

21. NO. OF PAGES

213

20. SECURITY CLASS

(THIS PAGE)

UNCLASSIFIED

22. Price $3.40

18. AVAILABILITY Unlimited

I For Official Distribution. Do Not Release to NTIS

I y I Order From Sup. of Doc, U.S. Government Printing Office Washington, D.C. 20402, SD Cat. No. CI3.1Q!459

I I Order From National Technical Information Service (NTIS)

Springfield, Virginia 22151 USCOMM.DC 29042-P74

"U.S. GOVERNMENT PRINTING OFFICE:1976 240-848/9 1-3


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