The System Integration and Verification Testing of an

Orbital Maneuvering Vehicle for an Air Bearing Floor

Final Report

Contrac t NAS8-35G3G

February 22. 1966

•»• ..... .5. ,3/5*

ESSEX,

CORPORATIO N

SPACE SYSTEMS GROUP

(90 U^c-cry Drixc • KunuvilLc. Alibtmi 35606
THE SYSTEM INTEGRATION AND VERIFICATION TESTING

OF AN ORBITAL MANEUVERING VEHICLE

FOR AN AIR BEARING FLOOR

Contract NAS8-35636

Final Report

February 22, 1986

PREPARED BY:

Nicholas L. Shields, Jr.

Mary Frances Martin

Karen R. Paulukaitis

John W. Haslam, Jr.

David E. Henderson

CORPORATIO N

SPACE SYSTEMS GROUP

PREPARED FOR:

Teleoperator and Robotics Evaluation Facility

Control Electronics Branch

George C. Marshall Space Flight Center

National Aeronautics and Space Administration

REPORT NO. H-86-02
FOREWORD

This contract final report marks the beginning of an opportunity to

systematically explore human/system interactions and human authority

over remote systems in a sophisticated simulation facility. The

components of this simulation facility are the 4,000-square-foot

precision air bearing floor, the Teleoperator Motion Base, the Target

Motion and Support Simulator, the mock-ups of the Hubble Space

Telescope, Multi-Mission Modular Spacecraft, and the Orbital Maneuvering

Vehicle, the engineering control station, and the remote operator's

Reconfigurable Workstation. The facility was designed and built to

provide Marshall Space Flight Center (MSFC) with unequalled capability

to support remote systems simulations. During the past two years, Essex

Corporation technical staff members have integrated each of these

elements with all the other elements of the laboratory and verified the

operational capabilities of the laboratory through a series of tests.

The result of all the design, fabrication, and technical effort is

reflected in the Teleoperator and Robotics Evaluation Facility (TOREF)

in Building A619 of the Marshall Space Flight Center.

Such a facility would not be possible without the foresight and

dedication of the engineering, technical, and management staff of MSFC

and the innovative and diligent approaches taken by Essex staff members.

The authors would like to recognize several Essex staff members who

contributed to the success of the Teleoperator program: Crystal Sulyma,

Tom Loughhead, Roger Winkler, and Doug Young. Among those NASA

personnel who deserve recognition are E. C. Smith, Wayne Wagnon, Tom

Bryan, and Frank Nola. The following MSFC employees served as subjects

in the test series and their contributions are greatly appreciated:

Elaine Hinman, Mike VanHooser, Michele Roeske, Steve Hall, John Ormsby,

Bridgette McKinley, Bill Jacobs, and Jim Randolph. The assistance of

Dr. Sue W. Kirkpatrick in the areas of test design and data analysis was

a valuable asset. Finally, special appreciation is extended to Fred

Roe, the TOREF facility manager and contract technical monitor for this

effort. His sense of the TOREF's potential benefits and his recognition

of the facility's widely varied applications kept the technical team
enthusiastic and pointed in the same direction for the past several

years.

The contract final report has been organized to reflect the growing

need for documentation as the contract requirements changed. The three

textual parts of this document describe: (1) the Teleoperator and

Robotics Evaluation Facility and its general capabilities to support

Orbital Maneuvering Vehicle (OMV) and other remote system simulations;

(2) the facility operating procedures and requirements; and (3) the

results of generic OMV investigations.

ii
TABLE OF CONTENTS

FOREWORD i

LIST OF FIGURES vii

LIST OF TABLES viii

ACRONYMS AND ABBREVIATIONS ix

PART 1 FACILITY INTEGRATION 1

1.0 INTRODUCTION 2

2.0 SYSTEMS LEVEL LABORATORY DESCRIPTION 4

2.1 Mobility Systems 4

Teleoperator Motion Base (TOM-B) 4

Target Motion and Support Simulator (TMSS) 6

Dynamic Target Simulator (DTS) 6

2.2 Control/Command/Telemetry System 6

Reconfigurable Workstation (RWS) 6

Controls 9

Command/Telemetry Link 9

2.3 Visual Systems 12

Remote Video System 12

Video Equipment 12

Auxiliary Video Systems 12

2.4 Target/Docking Systems 15

Hubble Space Telescope (HST) 15

Multi-Mission Modular Spacecraft (MMS) 15

Orbital Maneuvering Vehicle (OMV) 15

Docking Mechanisms 17

2.5 Data Collection and Recording Systems 18

2.6 Communication System 18

3.0 DOCUMENTATION 19

iii
TABLE OF CONTENTS (Continued)

Page

PART 2 FACILITY OPERATIONS 20

1.0 INTRODUCTION 20

2.0 MOTION SYSTEMS 21

2.1 Teleoperator Motion Base (TOM-B) 21

Pneumatic System 21

Electrical System 24

TOM-B Operating Procedures 24

2.2 Target Motion and Support Simulator and Dynamic 27

Target Simulator

3.0 SUPPORT EQUIPMENT 27

3.1 Flat Floor Equipment Rack 27

3.2 Visual System Equipment Rack 28

3.3 Auxiliary Cameras 28

Approach/Docking Line Camera 28

Control Room Camera 28

Flat Floor Surveillance Camera 28

3.4 Command/Telemetry Unit 28

4.0 CONTROL ROOM 29

5.0 FLAT FLOOR PROTECTION AND MAINTENANCE 29

5.1 Protection 29

5.2 Maintenance 30

iv
TABLE OF CONTENTS (Continued)

Page

PART 3 VERIFICATION TESTING 32

1.0 INTRODUCTION 33

2.0 VERIFICATION TEST PROCEDURES 34

3.0 EXECUTIVE SUMMARY OF VERIFICATION TEST RESULTS 41

4.0 SYNOPSES OF VERIFICATION TESTS 45

4.1 OMV Approach and Docking with Onboard Flood or Spot 45

Lights

4.2 OMV Camera Location: A Preliminary Investigation 48

4.3 Lighting Requirements for Two OMV Camera 51

Locations, Revision A

4.4 OMV Vision Systems: Field-of-View and Light Intensity 57

4.5 OMV Vision Systems: Operator Control of Zoom, Focus, 61

and Iris

4.6 OMV Operation with Reduced Video Frame Rate 63

4.7 The Utility of Stereo Vision for Remote Operations: 67

A Review

4.8 The Reconfigurable Workstation, Short Task Comparative 74

Analysis

4.9 Ground Control Station Design Guidelines 77

5.0 RECOMMENDATIONS FOR FURTHER RESEARCH 82

5.1 OMV Visual System 82

5.2 Video Bandwidth 83

5.3 Command/Response Time Delay 83

5.4 Ground Control Station 83
85

6.0 BIBLIOGRAPHY 85

6.1 General References 86

6.2 Vision Systems 88

6*. 3 Video Bandwidth Reduction 89

6'A Stereo Vision (Annotated) 107

6.5 Ground Control Station (Annotated)

vi
LIST OF FIGURES

Page

Figure 1.1: Teleoperator and Robotics Evaluation Facility 3

(TOREF) Laboratory Layout

Figure 1.2: Teleoperator Motion Base (TOM-B) 5

Figure 1.3: The Reconfigurable Workstation 7

Figure 1.4: The Reconfigurable Workstation Set for a 8

Demonstration of Stereo Vision

Figure 1.5: Camera Adjustment Controls on the Reconfigurable 10

Workstation Auxiliary Control Panel

Figure 1.6: Teleoperator and Robotics Evaluation Facility 11

Command/Telemetry System

Figure 1.7: Teleoperator and Robotics Evaluation Facility 13

Remote Video System

Figure 1.8: Visual System Equipment Rack 14

Figure 1.9: Hubble Space Telescope (HST), Multi-Mission 16

Modular Spacecraft (MMS), and Orbital Maneuvering

Vehicle (OMV) Mock-Ups

Figure 1.10: Three-Point Capture Device Mounted on the 17

Teleoperator Motion Base

Figure 2.1: Teleoperator Motion Base Pneumatic System Fill 22

Ports, Gauges, and Hand Loaders

Figure 2.2: Teleoperator Motion Base Control Panel 26

Figure 3.1: Three-Point Capture Device Docked with Hubble 36

Space Telescope Aft End Mock-up

Figure 3.2: Flat Floor Available Maneuvering Distance, 38

Alignment Angle, and Approach/Docking Zones

Figure 3.3: Hubble Space Telescope Docking Pin and 39

Three-Point Capture Device Claw in Docked Position

Figure 3.4: The Three-Point Capture Device Position of Lights 47

and Cameras

Figure 3.5: Teleoperator Motion Base/Three-Point Capture 49

Device Equipped with Four Cameras

Figure 3.6: Teleoperator Motion Base/Three-Point Capture 53

Device Location of the Pan and Tilt Unit,

Cameras, and Lights

vii
LIST OF FIGURES (Continued)

Figure 3.7: Camera/Target Geometries of Four Positions in a 60

Typical Approach and Docking Scenario

Figure 3.8: Video System used to Produce Reduced Frame Rate 65

Figure 3.9: Piezioelectric Lathanum Lead Zirconate Titanate 68

Stereo Display System

Figure 3.10: Flight Configured Fresnel Stereo Display System 69

LIST OF TABLES

Table 3.1 Test No. 06-85-OMV-03-A Experimental Design 55

Table 3.2 Positions of the RWS (degrees) Chosen by Twelve 76

Subjects

viii
LIST OF ACRONYMS AND ABBREVIATIONS

C&DM - Communications and Data Management Subsystems

CID - Charged Induction Device

CRL - Central Research Laboratories

CRT - Cathode-Ray Tube

CTU - Command/Telemetry Unit

DOF - Degree-of-Freedom

DTS - Dynamic Target Simulator

FAA - Federal Aviation Administration

FCFS - Flight Configured Fresnel System

FOV - Field-of-View

fr/s - Frames Per Second

GCC - Ground Control Console

GE - General Electric

HST - Hubble Space Telescope

MMC - Martin Marietta Corporation

MMS - Multi-Mission Modular Spacecraft

MSFC - Marshall Space Flight Center

MTF - Modulation Transfer Function

NASA - National Aeronautics and Space Administration

NOSC - Naval Ocean Systems Center

OMV - Orbital Maneuvering Vehicle

PLZT - Piezioelectric Lathanum Lead Zirconate Titanate

RF - Radio Frequency

RMS - Remote Manipulator System

RPV - Remotely Piloted Vehicle

RWS - Reconfigurable Workstation

TMG - Target Motion Generator

TMS - Teleoperator Maneuvering System

TMSS - Target Motion and Support Simulator

TOM-B - Teleoperator Motion Base

TOREF - Teleoperator and Robotics Evaluation Facility

2-D - Two-Dimensional

3-D - Three-Dimensional

ix
The System Integration and Verification Testing

of an Orbital Maneuvering Vehicle for an Air Bearing Floor

Contract NAS8-35636

Final Report

February 22, 1986

PART 1 FACILITY INTEGRATION

PREPARED BY:

Nicholas L. Shields, Jr.

John W. Haslam, Jr.

Mary Frances Martin

Karen R. Paulukaltis

David E. Henderson

(ESSEX)

CORPORATIO N

SPACE SYSTEMS GROUP
1.0 INTRODUCTION

From 1971 through 1983, the subsystems necessary for remote

operations were studied in isolated laboratories and evaluation

facilities at the Marshall Space Flight Center. This served a two-fold

purpose: investigators could study the primary contributions of the

major subsystems — displays, controls, mobility units, manipulators,

lighting systems, etc. — toward the human operator's ability to perform

remote, or teleoperated, tasks, and the investigations could be carried

out in small human performance laboratories with relatively simple

equipment.

Studying the primary effects of major subsystems provided knowledge

about the relative importance of, for example, various types of visual

subsystems, without having the information influenced by other factors

such as flight mobility subsystems or manipulator subsystems.

Similarly, the mobility and manipulator subsystems could be studied

without confounding the results with the influences of other subsystems.

As a result of these investigations between 1972 and 1982, over 27

technical reports were published detailing the individual studies of the

major subsystems.

Once the primary effects of the major subsystems were understood,

incremental integration of the subsystems was undertaken. Video

subsystems and manipulator subsystems were combined, as were manipulator

subsystems and mobility subsystems, and so on. Eventually, it became

necessary to integrate all the subsystems into one laboratory in order

to perform system level simulations and evaluations. This section of

Contract NAS8-35636 Final Report details the integration of the

components of the Teleoperator and Robotics Evaluation Facility (TOREF)

into NASA's largest and most versatile remote systems simulation

facility. The facility is centered around a 44 by 88 foot precision air

bearing floor, the largest of its kind. A mobility unit, isolated

control room, and support equipment were integrated into the facility to

provide the means for remote operation simulations. The facility layout

and physical configuration are shown in Figure 1.1.
ORIGINAL PAGE IS

POOR QUAUTY

ORIGINAL Pr.?2 B

FLAT FLOOR

VIEWING AREA

FLAT FLOOR

VISUAL \J

SYSTEM

CONTROL

ROOM

4JFLAT FLOOR

^EQUIP. RACK

{£>0*.v>, i-x-^

Figure 1.1: Teleoperator and Robotics Evaluation Facility (TOREF)

Laboratory Layout
2.0 SYSTEMS LEVEL LABORATORY DESCRIPTION

Six main laboratory subsystems were necessary to perform the remote

operation tasks required for teleoperator simulations. This section

describes the mobility, control/command/telemetry, visual, target and

docking, data collection, and communications systems which were

incorporated into the laboratory. System documentation is provided by

figures in the text and in an appended drawing package.

2. I Mobilit y Systems

Central to the TOREF are three dynamic motion simulator systems.

The Teleoperator Motion Base (TOM-B), the Target Motion and Support

Simulator (TMSS), and the Dynamic Target Simulator (DTS) each provide

the means for simulating spacecraft movement in up to six

degrees-of-freedom (6DOF) toward fixed or dynamic targets. The TOM-B

and TMSS move on precision air bearings over the flat floor, and the DTS

is essentially a robot arm which is operated from the west end of the

flat floor. Different levels of control are incorporated into each

mobility system and each system is equipped with a standard mounting

plate which is compatible with any of the TOREF mock-ups or targets.

Teleoperator Motion Base (TOM-B)

The TOM-B (Figure 1.2) is the most versatile and complex component

in the TOREF. This 6DOF air bearing vehicle may serve as a

maneuvering/docking craft or as a target craft. With self-contained

electrical and pneumatic systems, the TOM-B is capable of completely

remote operation from the control room.

The TOM-B system contains six 3,600 psi air tanks for pneumatic

power, and the pneumatic system can be refilled at the flat floor

service pad. The TOM-B electrical systems are powered by three separate

wet-cell battery packs which can be recharged simultaneously at the

service pad. Thirty-two, 2.81b thrusters, located on eight plena around

the perimeter of the motion base, provide X, Y, and yaw axes of motion.

The remaining three axes of motion—pitch, roll, and Z—are provided by
electric motors and drive trains. A detailed description of the TOM-B

is provided in Teleoperator and Teleoperator Thruster Control, Contract

No. NAS8-34726 Final Report No. H-85-04.

Figure 1.2: Teleoperator Motion Base (TOM-B)
Target Motion and Support Simulator (TMSS)

The TMSS is used on the flat floor to mount mock-ups and targets.

Unlike the TOM-B, the TMSS is not a self-contained mobility unit. The

TMSS pneumatic and electrical systems are powered through an external

umbilical. The TMSS floats freely in the X, Y, and yaw axes on the flat

floor and two motor drives provide Z and roll movements. The TMSS has a

much smaller payload capability than the TOM-B. The TMSS has been

described in Contract No. NAS8-34388 Final Documentation (1982).

Dynamic Target Simulator (DTS)

The DTS is a 6DOF robot arm with a l,0001b payload capability and a

20ft reach over the flat floor. The DTS is mounted at the west end of

the flat floor and can simulate realistic spacecraft motions. The DTS

may be used as a target craft or docking/maneuvering craft with respect

to the TOM-B. Documentation on the DTS is available from Marshall Space

Flight Center, EB24.

2.2 Control/Command/Telemetry System

The Control/Command/Telemetry System provides the equipment

necessary for controlling the remote operation of the TOM-B. This

system is composed of a workstation, system controls, and a

command/telemetry link.

The Reconfigurable Workstation (RWS)

The RWS was designed and built by Essex to meet the requirements of

the TOREF for a general purpose, reconfigurable, remote systems

workstation. The RWS, located in Control Room 1 (Figure 1.1), has been

described in Analysis and Selection of a Remote Docking Simulation

Visual Display System, Contract NAS8-35473 Final Report No. H-84-04.

The RWS provides a primary worksurface which supports the operator's

forearms during hand controller operation, a primary visual panel which

holds two 33cm monitors, and a 91 x 123cm large screen display. The

workstation also has panels for test-specific controls and displays.

The RWS is shown in Figures 1.3 and 1.4.
LARGE SCREEN DISPLAY

SECONDARY

CONTROLS

PRIMARY KEYBOARD

Figure 1.3: The Reconfigurable Workstation
ORIGINAL PASSE IS

OF POOR QUALITY

Figure 1.4: The Reconfigurable Workstation Set for a Demonstration of

Stereo Vision
Controls

The RWS primary worksurface contains two 3DOF hand controllers and

an interactive keyboard. The rotational hand controller (Measurement

Systems, Inc., model 544-G308) is located on the right side of the RWS

primary worksurface. This controller actuates the TOM-B pitch, roll,

and yaw functions. A four-way thumb switch located on the rotational

controller operates the pan and tilt unit for the TOM-B perimeter

camera. The translational hand controller (Measurement Systems, Inc.,

model 544-G510) is located on the left side of the RWS. This controller

actuates the X, Y, and Z axes of the TOM-B.

For check-out or demonstration purposes, the TOM-B may also be

controlled from the engineering console located in the flat floor

equipment rack (Drawing No. 35636-01). This 19-inch rack contains two

3DOF joy sticks and two monitors.

The auxiliary controls currently in use are toggle switches and

thumb wheels. Four, two-way, momentary toggle switches are located on

the left RWS auxiliary control panel (Figure 1.5). These switches are

configured to remotely operate the iris of the TOM-B bore sight camera

and the zoom, focus, and iris of the perimeter camera. Three thumb

wheels, located to the right of the workstation, allow selection of the

images displayed on the three RWS monitors. The interactive keyboard is

an RCA Data Terminal (model UP4801), located in the center of the RWS

primary worksurface. A three-position trigger, a miniature joy stick,

push buttons, and a bar switch are located on the rotational hand

controller and are available for future control configurations.

Command/Telemetry Link

The remote command/telemetry link is shown in Figure 1.6. The

Command/Telemetry Unit (CTU) was designed and built by Marshall Space

Flight Center, EC33. Documentation on the CTU is available from Fred

Roe, EB24. The telemetry portion of this system is not in use at the

present time. The command/telemetry system was installed in the

facility in an interim configuration in order to proceed with the

test and evaluation requirements.
ORIGINAL PAGE IS

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Figure 1.5: Camera Adjustment Controls on the Reconfigurable Workstation

Auxiliary Control Panel

10
Output

from Workstatio n

-< Translational Controller

-< Rotational Controller

-< Auxiliary Controls

Transmit

Antenna Antenna Input

to TOM-B

Thrusters

Motors

Pan and Tilt

Cameras

Feedba ck

Component Specifications

A Hewlett Packard HP 8640B

B Motorola MCR 503-3

C Command/Telemetry Unit

D Electro Mechanical Research Inc. Model 2468-01

E Defense Electronics Inc. Model TR-711

Figure 1.6: Teleoperator and Robotics Evaluation Facility Command/Telemetry

System

11
2.4 Target/Docking Systems

Three mock-ups have been used to simulate docking targets or

remotely piloted vehicles in the TOREF: the aft end of the Hubble Space

Telescope (HST), the Multi-Mission Modular Spacecraft (MMS), and the

Orbital Maneuvering Vehicle (OMV). Docking mechanisms are available to

interface with each of these mock-ups

Hubble Space Telescope (HST)

The HST is a full-scale mock-up of the aft end of the flight HST.

The mock-up is mounted at the east end of the flat floor at a height

compatible with TOM-B docking mechanisms. The aluminum-framed,

paper-covered, lightweight mock-up has three hard-mounted docking points

as well as a standard Remote Manipulator System (RMS) docking target.

The HST is mounted on a rigid stand; however a small yaw and pitch

capacity and a continuous 360 degree roll are built into the mounting

stand. The HST, shown in Figure 1.9, may also be mounted on the DTS.

Multi-Mission Modular Spacecraft (MMS)

The MMS (Figure 1.9) is a full-scale mock-up of a module which is

incorporated in some spacecraft designs, such as the Solar Maximum

Satellite. The lightweight, aluminum-framed, paper-skinned mock-up is

currently mounted on the DTS. The mounting plate is also compatible

with the TOM-B, TMSS, and HST stand mounting plates. The MMS is

equipped with three hard docking points and an RMS docking target.

Orbital Maneuvering Vehicle (OMV)

A full-scale mock-up of the OMV (Figure 1.9) is available for

laboratory use. This generic mock-up may be mounted on the TOM-B, DTS,

and HST stand. The OMV is equipped with a mount for the RMS end

effector and an RMS grapple fixture. The OMV may be used as a target or

as a remotely operated vehicle.

PRECEDING PAGE BLANK NOT FILMED

15
ORIGINAL PAGZ !S

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Figure 1.9: Hubble Space Telescope (HST), Multi-Mission Modular Spacecraft

(MMS), and Orbital Maneuvering Vehicle (OMV) Mock-ups

16
ORIGINAL PAGZ 5S

OF POOR QUALITY

Docking Mechanisms

The MSFC Three-Point Capture Device is currently mounted on the

TOM-B (Figure 1.10). The Capture Device is compatible with the HST and

the MMS. Also available are an RMS end effector, an Essex Three-Claw

Docking Mechanism, and a Docking/Retrieval Mechanism. The RMS end

effector may be mounted on the TOM-B or the DTS for docking with the OMV

mock-up.

Figure 1.10: Three-Point Capture Device Mounted on the Teleoperator

Motion Base

17
2.5 Data Collectio n and Recordin g Systems

A VAX 11/750 computer is provided for real-time simulation and for

data collection and analysis. This computer is equipped with a high

speed printer and keyboard connections.

Video may be recorded with a Panasonic Portable VHS recorder

(NV-8420) and camera. A Panasonic Omnivision II VHS recorder (NV-8950)

is also available for use with any of the laboratory cameras.

2.6 Communicatio n Syste m

The laboratory communication system was manufactured by Clear Com

Systems Inc. The system provides two-channel voice communication

between the flat floor safety technician, test conductor, and flat floor

equipment monitor.

The power supply for the communication system is located in the

flat floor equipment rack (Drawing No. 35636-01). This supply powers

connection/intercom boxes located on the equipment rack and on the flat

floor and control room patch panels. Multiple headset connections are

provided by these boxes. The communication system is documented in

Drawing No. 35636-05 and 35636-06.

Five headsets are available in the laboratory. The safety

technician's headset is equipped with a cord which allows the technician

to communicate from any location on the flat floor. For use during

testing or system check-out, a headset is located at the engineering

console. A headset is also provided for the test conductor in Control

Room 1 with optional connections for the operator or for a technician in

the video equipment room.

18
3.0 DOCUMENTATION

Several of the TOREF subsystems have been documented throughout the

text of this report. Additional documentation is included in a drawing

package which is appended to this report. A list of the drawings is

given below.

Drawing No. Title

35636-01 TOREF Flat Floor Equipment Rack

35636-02 Visual System Equipment Connections

35636-03 TOREF Approach/Docking Line Camera and Light System

35636-04 Laboratory Surveillance Camera

35636-05 Control Room 1 Communications

35636-06 Control Room Patch Panel #2 and Flat Floor Patch Panel #1

19
The System Integration and Verification Testing

of an Orbital Maneuvering Vehicle for an Air Bearing Floor

Contract NAS8-35636

Final Report

February 22, 1986

PART 2 FACILITY OPERATIONS

PREPARED BY:

Nicholas L. Shields, Jr.

Karen R. Paulukaitis

John W. Has lam, Jr.

Mary Frances Martin

David E. Henderson

c

CORPORATIO N

SPACE SYSTEMS GROUP

20
1.0 INTRODUCTION

In order for test personnel to reach appropriate levels of data

production and data analysis at the TOREF, efficient and safe operation

of the equipment and systems in the laboratory is essential. The

delicate and dangerous nature of the laboratory systems dictates a

thorough working knowledge of all system components, human/system

interfaces, and system/system interfaces. Inexperienced or untrained

personnel should be prohibited from operating any of the TOREF

equipment. Specific areas of concern include the motion systems,

support equipment, control room equipment, and protection and

maintenance of the flat floor.

2.0 MOTION SYSTEMS

The motion systems include the TOM-B, TMSS, and the DTS. Safe

operating procedures and routine maintenance are required for each

system.

2.1 Teleoperator Motion Base (TOM-B)

To create dynamic motion simulation capabilities, the TOM-B is

powered by high-pressure pneumatics and high-amperage electronics.

Improper use or neglected maintenance of this system could cause injury

to operators or damage to system components.

Pneumatic System

All TOM-B pneumatic fittings should be secure before tank filling

is attempted. Fittings should be checked for leaks and tightness on a

weekly basis.

Two fill ports with individual shutoff valves are located on the

rear of the TOM-B, and the vehicle can be refilled in approximately

10 to 15 minutes from the flat floor service area. The ports, one for

the thruster system and one for the air bearing pad system, can be

filled separately or together. Pressure gauges are provided for each

tank system. The pneumatic system fill ports, gauges, and hand loaders

are shown in Figure 2.1.

21
ORIGINAL PAGE IS

OF POOR QUALITY

Air Pad Hand Loade r Thruste r Hand Loade r

Air Pad Gaug e

and

Air Pad Fill Port

Thruste r Gaug e

and

Thruste r Fill Port

Figure 2.1: Teleoperator Motion Base Pneumatic System Fill Ports, Gauges,

and Hand Loaders

22
The procedure for refilling the TOM-B air system is as follows:

1. Purge air panel connecting lines and close purge valve.

2. Set air panel dome loader to 3,000 psi (or a lesser

desired pressure).

3. Couple armored air panel connecting lines to TOM-B fill

ports.

A. Open TOM-B thruster and air pad system shutoff valves.

5. Open shutoff valve to air panel connecting lines.

6. Allow tanks to fill to desired level (maximum = 3,000

psi).

7. Close shutoff valve to air panel connecting lines.

8. Close TOM-B thruster air and air pad system shutoff

valves.

9. Purge connecting lines, leaving purge valve open.

10. Uncouple connecting lines and stow.

High pressure air (up to 3,000 psi in this system) can be very

dangerous. Any deviation from the tank filling procedure may result in

injury to laboratory personnel. In case of a line failure, close all

fill valves immediately.

When performing routine line checks on TOM-B plumbing, fill

plumbing system with desired pressure and close valves to TOM-B tanks.

This allows for a high pressure leak inspection with a small volume of

air in the plumbing system. In the event of a ruptured line during

inspection, this procedure would limit the amount of escaping air flow

and the risk of injury to lab personnel.

For further pneumatic system information, see Contract NAS8-34726

Final Report No. H-85-04.

23
Electrical System

Standard caution observed around electrical systems should be used

when charging the TOM-B battery bank system or when working on the TOM-B

electrical wiring system.

The battery bank system is designed to facilitate charging with one

plug for all three battery banks. The procedure for charging the system

is as follows:

1. Turn TOM-B power off.

2. Plug charging system cable into TOM-B receptacle, turn

clockwise, and lock.

3. Turn all charging system power supply voltage and current

controls to zero.

4. Turn on the three charging system power supplies.

5. Adjust Bank No. L charger to <30 VDC, <10 amps.

Adjust Bank No. 2 charger to <36 VDC, <12 amps.

Adjust Bank No. 3 charger to <30 VDC, <10 amps.

6. When current levels drop to 1-3 amps, batteries are

charged.

8. Turn off all charging system power supplies.

9. Unlock and unplug charging system cable and stow.

All electronic devices on TOM-B are wired with a common ground to

the aluminum frame of the TOM-B. Because of this, any positive voltage

applied to the TOM-B ground or frame may damage the electrical system.

For further electrical system information, see Contract NAS8-34726 Final

Report No. H-85-04.

TOM-B Operating Procedures

Initial Start-Up and Check-Out Procedures

1. The facility air handlers should be on unless a test run

is in progress. If the air handlers are not on, they

should be turned on at the breaker box located behind the

flat floor equipment rack (Breaker No. 29).

2. Place flat floor equipment rack breaker No. 34 in the "on"

position.

3. The signal generator should be set at 450 MHz and locked.

4. The pneumatic system of the TOM-B should be filled

according to the procedures in Section 2.1.

24
5. After all control room start-up procedures have been

completed, the power switch on the TOM-B control panel

(Figure 2.2) should be placed in the "on" position.

6. Place the following toggle switches on the TOM-B control

panel in the "on" position: motors, thrusters, transmit,

receive, video 1, video 3, aux 1, and aux 2.

7. Complete a check-out from the flat floor area. Fire

thrusters and move the motors from engineering console

and move the pan and tilt unit from the TOM-B.

8. Complete a check-out from the control room. Fire the

thrusters, move the motors, and move the pan and tilt unit

from the RWS.

9. Place the power and video 3 toggle switches in the off

position until test runs begin.

Test Run Procedures

1. Turn off air handlers and the light above the equipment

rack.

2. Turn air pad hand loader to 40-55 psi and thruster air

hand loader to 100 psi. DO NOT exceed these values.

3. TOM-B should be pushed to the test run starting position.

The TOM-B air pads SHOULD NOT come into contact with the

edge of the flat floor.

4. For dark-side runs, the flood and spot toggle switches

should be placed in the "on" position.

5. Battery and air levels should be continually monitored

by the safety technician when the TOM-B is in operation.

Power levels may by read from the control panel meters

(Figure 2.2). Voltages should not be allowed to drop

significantly below the charged levels. Amperage readings

should not exceed 2.5 amps. The pad air system should not

be allowed to drop below 200 psi. The amount of air in

the pad system must be continually monitored. If the pad

air system level drops below 100 psi, the TOM-B could

become stranded on the flat floor. If levels are not as

specified, the TOM-B should be returned to the service

area for check-out or maintenance.

25
ORIGINAL PAGE IS

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Figure 2.2: Teleoperator Motion Base Control Panel

26
Shut-Down Procedures

1. The TOM-B should be returned to the service area.

2. The air pads should be down loaded to 0 psi.

3. All toggle switches should be placed in the off position.

4. The air handlers should be turned on.

5. The flat floor equipment rack should be turned off.

6. The light above the equipment rack should be turned

on.

7. All other flat floor lights should be turned off.

2.2 Target Motion and Support Simulator and Dynamic Target Simlato r

The TMSS is powered by pneumatics and electronics. The same safety

and maintenance practices observed with use of the TOM-B should also be

applied to use of the TMSS and DTS. Procedures for operating the DTS

are available from Marshall Space Flight Center, EB 24.

3.0 SUPPORT EQUIPMENT

All support equipment should be turned on 30 minutes prior to

check-out procedures to allow for equipment stabilization. All equipment

should be turned off before leaving the TOREF.

3.1 Flat Floor Equipmen t Rack

The flat floor equipment rack is turned on at the breaker box

located behind the rack. Specific equipment settings are as follows:

H.P. Signal Generator Frequency = 450.00 MHz

Left Microwave Transmitter RF = 2287

Local OSC = 2205

Right Microwave Transmitter RF = 2223

Local OSC = 2145

Upper H.P. Power Supply VDC - 28

Lower Kepco Power Supply VDC = 5

27
3.2 Visua l System Equipmen t Rack

The visual system equipment rack is turned on by inserting four

plugs into the sockets of an extension cord. Standard care and

maintenance of the electrical cords and sockets should be followed. The

video connections in this rack are given in Drawing No. 35636-02.

Additional information about the capabilities and operation of this

system is available from Daryl Craig, EB 23.

3.3 Auxiliar y Camera s

Approach/Docking Line Camera

The toggle switch on the power supply located under the

approach/docking camera should be placed in the "on" position. This

will turn on the approach/docking light in addition to the camera. The

reading on the power supply should be 28 VDC. Care should be taken to

insure that the TOM-B does not come in contact with the approach/docking

light or the power supply.

Control Room Camera

The control room camera is activated by placing the toggle switch

on the Panasonic power supply in the "on" position. The power supply is

located next to the visual system equipment rack.

Flat Floor Surveillance Camera

This camera is activated when the flat floor equipment rack is

turned on. Display images are presented on the center monitors when the

appropriate channel is selected.

3.4 Command/Telemetr y

The CTU, located in the Computer Room, is powered by a Kepco

regulated power supply located adjacent to the CTU rack. Voltage

readings taken from the terminals at the back of the CTU should be

5 VDC, +0.25.

28
4.0 CONTROL ROOM

All control room equipment should be turned on at least 30 minutes

prior to a test run in order to allow equipment power levels to

stabilize. All monitors should also be turned on at this time. Picture

selection should be made with the three thumb wheels located at the

right side of the RWS. The RWS primary worksurface and monitors can be

adjusted by carefully loosening the clamps on the supporting shocks,

moving the worksurface and/or monitors, and carefully tightening the

clamps. No excessive weight (including equipment) should be placed on

the RWS primary worksurface. All control room equipment should be

turned off prior to leaving the TOREF.

5.0 FLAT FLOOR PROTECTION AND MAINTENANCE

Protection of the flat floor is an absolute necessity for TOREF

operation. The thin film of air escaping from the air bearing pads on

the TOM-B and TMSS must have a smooth, flat surface on which to ride.

Scratches and indentations in the epoxy flat floor can disrupt the

ability of the motion systems to float on the flat floor. Methods to

repair epoxy air bearing floors have been unsuccessful in the past; this

increases the necessity of keeping the floor free of any damage.

5. I Protection

The 4,000-square-foot epoxy surface, known as the flat floor, was

applied by Essex Corporation in 1983. The care and maintenance of this

surface is critical to its usefulness as a test bed. There is no

demonstrated way of repairing this surface if it becomes damaged. The

epoxy used in preparing the flat floor is still elastic and will remain

so for at least the next ten years. Samples poured by Essex in 1975

still show elasticity, and the technical documentation on the epoxy

suggests that it will become 98% cured in 20 years. For this reason,

loads should not be placed on the flat floor for extended periods of

time. This will result in depressions on the floor which will "capture"

29
the air bearing pads of the TOM-B. For periods of extended rest, the

TOM-B should be removed from the flat floor or moved daily from one

position to another on the service pad area.

No vehicle, other than precision floating vehicles, should ever be

permitted on the flat floor surface. No wheeled carts or trolleys

should be allowed on the floor. If there is a need to move equipment

onto the floor, equipment can be placed on the available suspension

bridge which spans the floor.

Never permit overhead work to be conducted without suitable

protection for the flat floor. Even changing light bulbs involves the

risk of ladders or glass bulbs falling on the floor, either of which

could irreparably damage the floor surface.

Personnel required to walk upon the floor must wear clean room

booties over flat-soled tennis shoes (not over bare feet or street

shoes). It is preferable that persons who will be serving as safety

technicians reserve a pair of tennis shoes strictly for this purpose.

The requirement to have people walk on the epoxy surface should be kept

to an absolute minimum.

When servicing the TOM-B, it should always be placed in the service

pad area or removed from the flat floor. If maintenance is conducted in

the flat floor service area, the floor underneath should be draped if

fluids are being used or if mechanical systems are being moved or

altered. If there is drilling or any activity that may leave scraps in

the TOM-B, the scraps should be blown out with low pressure air to make

sure that no foreign material makes its way to the epoxy floor surface.

5.2 Maintenanc e

Accumulated dust can interfere with the operation of the TOM-B as

it floats only one thousandth of an inch above the flat floor surface.

Consequently, the floor should be damp mopped with alcohol at least once

a week when not in use and before every test session when in

experimental use. The floor should be mopped with soft floor mops

covered with non-lint cloth, the whole of which has been dampened with

190 proof alcohol. When debris has been picked up on the cloth, it

should be replaced immediately with clean cloth. The pattern for

30
cleaning (up and down or back and forth, etc) should be changed

periodically so that the patina does not run only one way on the floor.

The area around the flat floor should be completely vacuumed every week,

and foreign material should be cleaned up immediately.

31
The System Integration and Verification Testing

of an Orbital Maneuvering Vehicle for an Air Bearing Floor

Contract NAS8-35636

Final Report

February 22, 1986

PART 3 VERIFICATION TESTING

PREPARED BY:

Nicholas L. Shields, Jr.

Mary Frances Martin

Karen R. Paulukaitis

John W. Haslam, Jr.

David E. Henderson

ESSEX)

CORPORATIO N

SPACE SYSTEMS GROUP

32
1.0 INTRODUCTION

The purpose of the second phase of the Integration/Verification

contract was to conduct a pilot test series to demonstrate the readiness

of the Teleoperator and Robotics Evaluation Facility to support

investigations in the area of remote operations and to obtain useful

results and conclusions generic to the use of remotely controlled space

vehicles. In order to address a current need for data, the test series

focused on information necessary for the design of the Orbital

Maneuvering Vehicle (OMV). Although the test series revolved around the

OMV, the data obtained contribute to the general fund of knowledge on

the subject of human operation of remotely managed systems.

The test series began in September 1984 with a study comparing the

Reconfigurable Workstation (RWS), which was designed by Essex under a

separate contract (NAS8-35473) for use in the TOREF, with a conventional

workstation. The research effort was then suspended to allow Essex

engineers to modify the Teleoperator Motion Base (TOM-B) motor drive and

air system under contract NAS8-34726 so that the motion base would be

capable of fulfilling the requirements of an OMV simulation which arose

after the original TOM-B was constructed. The test series was restarted

in February 1985 with an investigation concerning the OMV on-board

lighting system and continued until January 1986. During this period, a

variety of research methods were used to investigate the issues of OMV

camera location, lighting requirements, camera pointing, fieId-of-view,

camera lens control by the operator, video bandwidth reduction, the

utility of stereo vision, and ground control station specifications.

The objectives of this section of the contract final report are to

give a summary of the findings from the verification test series, to

provide a detailed synopsis of each test conducted, to outline issues

for future research, and to provide an extensive bibliography for each

topic investigated in this test series for use by future researchers.

This research effort was conducted under the direction of Nicholas

Shields Jr., Essex Teleoperator and Robotics Program Manager. Mr.

Shields has been involved in the Teleoperator Technology Development

Program at MSFC for the past 14 years. Mary Frances Martin served as

test conductor and was responsible for experimental design, data

33
collection and analysis, and publication of test results. Working with

Ms. Martin were Crystal D. Sulyma and Karen R. Paulukaitis. Ms.

Paulukaitis and Ms. Sulyma were instrumental in data analysis and report

publication as well as being responsible for TOREF facility operations.

David E. Henderson designed the TOREF systems necessary for remote

operation of the TOM-B and was responsible for system trouble-shooting

throughout the test program. John W. Haslam, Jr. designed much of the

Essex hardware in the laboratory and was responsible for test-specific

hardware design, fabrication, and installation.

2.0 VERIFICATION TEST PROCEDURES

The experimental philosophy employed in the design of the test

procedures was to use a small number of test subjects, who were

well-trained on a standardized task, in a within-subjects design with

repeated measures. This philosophy was adopted based on the fact that

the OMV operators will be extensively trained through the use of

simulations. In addition, the use of experienced subjects maximized the

available training/testing time and minimized the effects of learning on

test results. The within subjects type of experimental design and

statistical analysis with repeated measures take into account the

variability in each individual's performance which is not a result of

the influence of the independent variables. This type of analysis

determines where statistically significant differences occur while

adjusting for the random variability which is inherent in human task

performance. In this experimental design, each subject makes several

test runs under all of the experimental conditions. The analysis of

variance (ANOVA), which is employed to test for significant performance

differences, is calculated using the mean of each subject's scores on

the dependent variables. An alpha level of .05 was used to determine

statistical significance throughout the test series. Differences which

reached significance at the .10 level were considered statistical

trends.

All test subjects were NASA employees. The subjects were given the

Federal Aviation Administration (FAA) examination for visual acuity at

34
the NASA Medical Center. Only subjects who had normal visual acuity (or

acuity corrected to normal) participated in the test series.

Additionally, selected body dimensions were measured to insure that all

subjects were within the 5th to 95th percentile size range of the U.S.

population. The subjects' average age was 28.3 years, and the number of

men and women who participated in the tests was approximately equal.

Subjects were trained using a successive approximation technique.

This type of training increases the difficulty of the task performed in

small steps. First, the general operation and purpose of the TOREF was

explained to the subject. The subject then used direct vision to

operate the TOM-B from the flat floor engineering console. The

operation of the RWS remote hand controllers was demonstrated, and the

subject operated each TOM-B axis of motion independently in order to

learn the precise outcome of each input on the remote visual image. The

subject then practiced an approach and docking task under normal

laboratory lighting until their performance stabilized. Prior to each

test session, the subject made one to three "warm-up" runs under these

conditions.

The apparatus used in the tests has been described in Part 1 of

this report. Briefly, the TOM-B and the Three-Point Capture Device

constituted the basic OMV simulator. The simulator was equipped with

cameras and lights as required for each test. Subjects controlled the

motion base from the RWS with two 3DOF hand controllers. The target

chosen for these tests was the HST aft end mock-up. This mock-up and

the Three-Point Capture Device were selected for the baseline system

because HST retrieval is one of the OMV design reference missions. The

capture device and target are shown in Figure 3.1.

An approach and docking task was designed for use throughout the

test series. The task began with the motion base placed at the west end

of the flat floor and aligned with the HST target. This alignment was

chosen based on the assumption that the OMV approach control mode would

have achieved translational alignment with the target at the

simulator-to-target distance available on the flat floor (21.3m). Due

to the nature of the test design, the TOM-B pitch and Z motor axes were

set at docking alignment during the first test in the series. In the

remaining tests, the Z axis was offset +20cm from ideal alignment and

the pitch axis was offset +5 degrees at the beginning of each run.

35
ORIGINAL PAGE IS

POOR QUALITY

Figure 3.1: Three-Point Capture Device Docked with the Hubble Space

Telescope Aft End Mock-up

36
An optimal translational alignment angle with respect to the target

was empirically determined by measuring the distance that the capture

device claws could be off alignment with the HST docking pins and still

make a successful dock. Motion base movements outside this angle were

termed translational errors. The time required to reenter the alignment

angle was termed translational error recovery time. The flat floor

available maneuvering distance (21.3m) was divided into approach and

docking zones. The first 75 percent of the range to the target (16.0m)

was designated as the approach zone and the remaining distance to the

target (5.3m) was called the docking zone. The alignment angle and

approach/docking zones are shown in Figure 3.2.

The subject's task was to place the simulator in motion on a signal

from the test conductor, approach, and attempt to dock with the target.

In all tests, a successful dock was defined by the entrance of the HST

docking pins into all three of the capture device claws (Figure 3.3).

The only information provided to the subject during test runs was visual

feedback from the simulator cameras and start/stop signals from the test

conductor. Task illumination was provided by the overhead facility

lights for tests conducted under daylight conditions or by lights on the

simulator for tests in dark-side conditions.

The dependent measures were thruster air expended, elapsed run

time, frequency of translational errors, translational error recovery

time, and Z and pitch axes alignment. Instructions to subjects

emphasized successfully docking with the target and achieving a balance

between accuracy, air consumption, and elapsed time.

37
13

T

1

4 6«

1

JL

.4«

TOH-B

4.1

0.

=Cf?1

• — i

OZ 251 50Z 7

OB 5.3- 10. 7.. 16.

I |

~~~~— ^^

^-^__

"""*»•«» ^

Approach ,

Zone

"

11.7* ^^— — •"""

— — ' '""

SZ 1

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"^"^ --» .

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Zone

^. .

*— --*"""

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Figure 3.2: Flat Floor Available Maneuvering Distance, Alignment Angle,

and Approach/Docking Zones

38
ORIGINAL PAGE IS

OF POOR QUALITY

Figure 3.3: Hubble Space Telescope Docking Pin and Three-Point Capture

Device Claw in Docked Position

39
The following publications document the results of the

investigations conducted during the verification test series.

The main findings from these tests are summarized in Section 3.0.

Martin, M.F., Shields, N.L., Jr., & Rodriquez, R.C. (1984). The

Reconfigurable Workstation, short task comparative analysis (Test

Report No. 11-84-RWS-01). Huntsville, AL: Essex Corporation.

Martin, M.F., Young, D.G., & Sulyma, C.D. (1985). OMV approach and

docking with onboard flood or spot lights (Test Report No.

03-85-OMV-01). Huntsville, AL: Essex Corporation.

Martin, M.F., Sulyma, C.D., & Haslam, J.W., Jr. (1985). OMV camera

location: A preliminary investigation (Test Report No.

04-85-OMV-02). Huntsville, AL: Essex Corporation.

Martin, M.F., Sulyma, C.D. , & Paulukaitis, K.R. (1985). Lighting

requirements for two OMV camera locations, revision A (Test Report

No. 06-85-OMV-03-A). Huntsville, AL: Essex Corporation.

Martin, M.F. & Paulukaitis, K.R. (1985). OMV vision systems;

(A) Field-of-view and light intensity (B) Operator control of zoom,

focus, and iris (Test Report No. 10-85-OMV-04). Huntsville, AL:

Essex Corporation.

Martin, M.F. & Paulukaitis, K.R. (1986). OMV operation with reduced

video frame rate (Test Report No. 11-85-OMV-05). Huntsville, AL:

Essex Corporation.

40
3.0 EXECUTIVE SUMMARY OF VERIFICATION TEST RESULTS

This section summarizes the research findings obtained during the

verification test program. This program focused primarily on the OMV

visual system. Some aspects of the visual system are specified in the

OMV Requirements Document, Revision 2 (1985). This document states that

the OMV Communications and Data Management Subsystem (C&DM) shall

include cameras and lights necessary to accomplish docking and payload

viewing under full daylight or dark side conditions. The Requirements

Document further specifies that a minimum of two cameras will be

included in the C&DM and that at least one camera will have pan, tilt,

and zoom capabilities. One goal of the verification test series was to

conduct investigations regarding these minimum visual system

requirements and to establish visual system design criteria which will

optimize operator performance.

Camera Location

The results of Test No. 04-85-OMV-02 indicated that a

centrally-located camera, which bore sighted a docking target, combined

with a camera located at the outer perimeter of the OMV enhanced

operator performance. This conclusion was supported by previous

research and by observations throughout the remaining tests.

Camera Field-of-View

The effects of field-of-view (FOV) on remote operator performance

were investigated through a review of the past research on the use of

fixed and variable FOV (optical zoom) in the performance of target

acquisition tasks. Based on the available information, it was

recommended that a camera lens which provided a 4 to 55 degree variable

FOV under operator control be considered for inclusion in the OMV visual

system.

Iris, Zoom, and Focus Control

Test No. 10-85-OMV-04-B was conducted to investigate the effect of

placing the iris, zoom, and focus of the OMV perimeter camera lens and

the iris of the bore sight camera lens under operator control. The

41
addition of these controls to the operator's workload did not

significantly affect performance of the approach and docking task. The

results indicated that the addition of the lens controls tended to

improve performance during approach operations. Control of the camera

iris was helpful in reducing overly bright monitor images caused by

light reflected off the target surface.

Camera Pointing Control

Performance on the approach and docking task with and without pan

and tilt was compared in Test No. 06-85-OMV-03-A. The frequency of

translational alignment errors and the time required to recover from

misalignment increased significantly with the addition of pan and tilt.

It was concluded that these differences would be eliminated by

additional practice with the pan and tilt function. The pan and tilt

capability proved advantageous in a series of simulated bore sight

camera failure runs.

Type of Lights

Results of an initial lighting investigation (Test No.

03-85-OMV-01) indicated that a combination of flood and spotlighting

would improve operator performance of the approach and docking task

under simulated dark-side conditions. This conclusion was supported by

results from additional testing.

Light Location

Location on the OMV of individual lights was not used as an

independent variable in the test series. Test No. 06-85-OMV-03-A was

conducted primarily to investigate optimal beam widths; however, the

results also indicated that locating a light with the camera on the pan

and tilt unit was useful to the operators by allowing them to point the

light and illuminate target features for translational alignment. A

light was also located with the bore sight camera throughout the dark

side tests in the series and provided adequate illumination for this

camera image.
Light Beam Width

Four floodlight and four spotlight beam width combinations were

investigated in Test No. 06-85-OMV-03-A. Performance of the approach

and docking task under dark side conditions was enhanced by the use of

a floodlight combination of an 80 x 20 degree beam width at the bore

sight camera location and a 40 x 7 degree width at the pan and tilt

perimeter camera location. Performance was degraded by the use of two

80 x 20 degree floodlights and two 5x5 degree spotlights. It was

concluded that the 80 x 20 degree floodlight at the bore sight location

combined with either the 10 x 4 spotlight or the 40 x 7 floodlight at

the perimeter camera location should be subject to further evaluation.

Light Intensity

Light intensity was the subject of an empirical analysis in Test

No. 10-85-OMV-04-A. Intensity of two beam width combinations (an

80 x 20 degree floodlight at the bore sight camera location with either

a 10 x 4 degree spotlight or a 40 x 7 degree floodlight at the perimeter

camera location) was varied during an approach and docking scenario.

The resulting luminance of both camera images on the remote monitors was

measured and compared with standards drawn from previous human factors

research. The monitor images were also evaluated for subjective picture

quality. Results of the evaluation indicated that monitor luminance

between 95 and 350 candelas/square meter (cd/m2) would present

satisfactory visual cues to the operator.

Stereo Vision

An extensive literature search was conducted on the topic of

stereoscopic (stereo) vision and visual systems. Fourteen sources were

reviewed, most of which compared remote task performance using stereo

display systems with monoscopic (mono) display systems. Based on the

information obtained from the available research, the conclusion was

made that a mono system with two orthogonal views would be most

appropriate for use with the OMV. As a whole, the research did not

indicate a clear enough performance advantage to offset the increased

cost, complexity, and bandwidth required for a stereo, as opposed to

mono, system.

43
Frame Rate

OMV operation with reduced frame rate video feedback was

investigated in Test No. 11-85-OMV-05. It was concluded that use of a

5 frames/second (fr/s) transmission rate would not affect OMV operator

performance if the resolution and gray scale were not degraded below

normal levels. It was recommended that frame rates between 5 and 3 fr/s

should be subject to further investigation in conjunction with the use

of optical zoom and command time delay.

Resolution and Gray Scale

Equipment was not available to vary resolution and gray scale for

evaluation in Test No. 11-85-OMV-05. A review of previous research on

bandwidth reduction revealed that a video system which provided

3.75 fr/s, 256 x 256 pixels/frame resolution, and 1 bit of gray/pixel

did not significantly affect performance of a target acquisition task

using a remotely piloted vehicle. Because the conditions in these

studies were analogous to OMV operation, it was concluded that a system

of this nature should be investigated for the OMV visual system.

Ground Control Station

Guidelines for the design of the OMV ground control station were

developed based on the results of Test Report No. 11-84-RWS-01 and on

observations made throughout the verification test series. The

workstation should be designed to accommodate and optimize the

performance of a wide range of operators. The 5th percentile oriental

female through the 95th percentile U.S. male anthropometry standard was

recommended as the appropriate guideline. The worksurfaces and displays

should be adjustable to individual operator preference. Keyboards

should be located for bilateral operation and adjustable with respect to

the primary worksurface. Full forearm support should be provided for

hand controller operation. Provisions should be made for secondary

displays and controls within the nominal reach envelope and visual cone

of the 5th percentile operator; however the number of secondary tasks

required of the primary operator should be limited.

44
4.0 SYNOPSES OF VERIFICATION TESTS

Presented in this section is a synopsis of each test and evaluation

conducted under the Verification Test Program. The objectives,

background research, apparatus, methodology, results, and conclusions of

each investigation are summarized. The apparatus and methodology of all

tests were similar and are described in Section 2.0. Apparatus and

methodology which differed from this general test procedure are

specified in each synopsis.

4.1 OMV Approac h and Docking with Onboard Flood or Spot Lights

Test Report No. 03-85-OMV-01

The purpose of this test was to investigate the effects of flood

and spotlighting on operator performance of an OMV approach and docking

task under dark-side conditions. The null hypotheses were that the

dependent variables (run success, thruster air consumption, elapsed

time, translational error frequency, and error recovery time) would not

differ significantly due to the type of light (flood or spot) , the zone

of operation (approach or docking), or an interaction effect.

The OMV Requirements Document (1985) specified that the OMV

lighting system must provide sufficient illumination for payload viewing

and docking tasks under full daylight or dark-side conditions. Previous

Essex teleoperator evaluations at MSFC (Shields, Piccione, Kirkpatrick,

& Malone, 1982) indicated the existence of a dramatic interaction effect

between camera line-of-sight, target alignment, and target illumination

on docking success. Researchers also found that on-board floodlighting

was effective for illuminating target shapes and spaces which were

otherwise obscured by shadows in solar illumination conditions (Shields

& Henderson, 1981).

Seven subjects were chosen for training, and subsequently five were

chosen to participate in the test based on training performance. The

two women and three men ranged in age from 21 to 39 years.

The TOM-B and the Three-Point Capture device were equipped with a

Panasonic, WV-3890B, color camera at the bore sight location and a

45
Javelin, model JE2062, black and white camera mounted on the top claw of

the capture device. A General Electric (GE) 80 x 20 degree floodlight

and a 5 x 5 degree spotlight were mounted in adjustable fixtures on

either side of the bore sight camera. Location of the cameras and

lights is shown in Figure 3.4.

On a signal from the test conductor, subjects maneuvered the

simulator toward the HST mock-up and attempted to dock using either the

spot or floodlight. Subjects made three test runs with the spot and

three runs with the floodlight in a counterbalanced order.

A 2 x 2 x 5 ANOVA (type of light x zone of operation x subjects)

was employed for data analysis. Elapsed time differed significantly due

to the interaction of type of light and zone of operation, F(l,4) =

10.79, p < .05. This result was due to performance in the docking zone.

The time required to dock was significantly higher under the spotlight

condition than under the floodlight condition. There was no difference

in approach times. A significant difference in translational error

recovery time occurred due to the type of light, F(l,4) = 13.85,

p < .05. Mean error recovery times for approach and docking were lower

when the floodlight was used than when the spotlight was used. A trend

was evident in thruster air consumption due to the interaction effect,

F(l,4) = 4.58, p < .10. Less thruster air was expended during approach

under the spotlight condition than under the floodlight condition, and

thruster air consumption for docking was lower under the floodlight

condition than under the spotlight condition.

The results indicated that the use of both flood and spotlights

should be considered for the OMV visual system. The finding concerning

thruster air consumption tended to support the alternative hypothesis

that spotlights would enhance approach performance and floodlights would

improve docking performance. The elapsed time and translational error

recovery time performance also supported this hypothesis, but the

results on translational error frequency did not. Subject comments

during debriefing indicated that three of the subjects preferred the

floodlight while two preferred the spotlight. Those subjects who

preferred the floodlight stated that illumination of the target edges

aided in realignment when the simulator was yawed with respect to the

target, and those who preferred the spotlight said that the position of

46
ORIGINAL PAGE 13

OF POOR QUALITY

the spot on the target aided in translational alignment. It was

recommended that a combination of flood and spotlights be investigated

in conjunction with iris control by the operator.

Figure 3.4: The Three-Point Capture Device Position of Lights and

Cameras

47
4.2 OMV Camer a Location : A Preliminar y Investigatio n

Test Report No. 04-85-OMV-02

This test was conducted to investigate the effects of OMV camera

location on operator performance of an approach and docking task. The

null hypotheses were that performance on the dependent variables

(thruster air consumption, elapsed time, translational error frequency

and recovery time, and alignment of the Z and pitch axes) would not

differ significantly due to the camera placement condition.

A search of the NASA Technical Library revealed few studies

specifically concerning camera location for teleoperation. Two studies

conducted in the former MSFC Teleoperator Laboratory addressed this

issue. Shields and Henderson (1981) investigated the effect of

Teleoperator Maneuvering System (TMS) camera location on the performance

of an approach and docking task. No differences in performance occurred

due to the use of a centrally located, bore-sighted camera plus a camera

located on the right side of the TMS or a center plus a left side

camera. In a similar study, the use of a bore-sighted camera or an

off-center, top mounted camera did not significantly affect performance

(Shields, Piccione, Kirkpatrick, & Malone, 1982). The two docking

mechanisms specified for the preliminary OMV design, the Remote

Manipulator System (RMS) end effector and the Three-Point Capture Device

(OMV Requirements Document, 1985), necessitate the inclusion of a camera

bore-sighted on a docking target. Due to this requirement, a

bore-sighted camera was selected for this test as the baseline for the

location of additional cameras. A camera located on the capture device,

a camera located at the outer perimeter of the OMV, and a boom-mounted

camera that would extend approximately 3 feet beyond the perimeter of

the OMV have been proposed for the OMV design. These locations were

selected for investigation in the present study.

Two women and three men were chosen from the pool of experienced

operators. These subjects had participated in the previous test.

Based on the proposed diameter of the OMV (4.75m), the cameras were

located as shown in Figure 3.5 to simulate the four possible OMV camera

positions previously described. A Panasonic, WV-3890B, color camera was

placed in the center of the capture device, and an XES, model 8303, color

48
ORIGINAL PAGE IS

OF POOR QUALITY

3.36m

Extended

Boom

Camera

Perimeter

Camera

Capture

Device

Camera

Bore Sight

Camera

Figure 3.5: Teleoperator Motion Base/Three-Point Capture Device Equipped

with Four Cameras

49
camera was mounted on the capture device claw. The perimeter and

extended boom cameras were black and white Javelin miniature cameras,

model JE2062. The center camera was bore-sighted on the RMS camera

target located in the center of the HST mock-up. This camera provided

the subject with a picture of the entire target at the beginning of the

run, and it was adjusted so that the camera target was in the center of

the monitor when a successful dock was achieved. The capture device

camera was focused on the top claw and provided a view of the docking

pin as it entered the capture envelope. The perimeter camera and the

extended boom camera provided a view of all three claws of the capture

device at docking.

Subjects made five runs under four test conditions: bore sight

camera only, bore sight plus claw camera, bore sight plus perimeter

camera, and bore sight plus extended boom camera. The four test

conditions were presented to the subjects in a counterbalanced order.

At the beginning of each run, the Z axis was offset +20cm and the pitch

axis was offset +5 degrees.

A one-way ANOVA with repeated measures was applied to the data on

each dependent variable for approach and docking operations. Thruster

air consumption, elapsed time, translational error frequency, and error

recovery time were not significantly affected by camera location. Error

recovery time tended to be higher and more variable during approach

under the capture device camera condition. Error recovery time during

docking was most homogeneous under the perimeter camera condition.

Alignment of the Z axis was significantly affected by camera location,

F(3,12) «= 6.57, p <.05, with alignment being closest to ideal in the

perimeter camera condition. Pitch axis alignment tended to be closest

to ideal in the perimeter camera condition, F(3,12) - 3.03, p < .10.

Although a definitive conclusion could not be drawn regarding

optimal OMV camera location, the test results indicated that a perimeter

camera may enhance performance during docking operations. Alignment of

the Z and pitch axes and translational alignment during docking were

best when the perimeter and bore sight camera were used. Three of the

five subjects preferred this combination, and their performance was

consistently better in the perimeter camera condition.

50
No advantage in performance of the approach and docking task was

evident due to the extended boom camera. It was concluded that the

additional hardware complexity of this type of camera would not be

offset by enhanced performance. The perimeter and bore sight camera

combination was recommended for further investigation with added pan and

tilt, zoom, focus, and iris control by the operator.

4.3 Lightin g Requirement s for Two OMV Camera Locations, Revisio n A

Test Report No. 06-85-OMV-03-A

The objectives of this test series were to assess the effects of

adding pan and tilt functions to the OMV perimeter camera and to

investigate lighting requirements for OMV perimeter and bore sight

camera locations. The pan and tilt test was conducted first so that the

pan and tilt function could be used in the lighting test without

confounding the results of that investigation. The null hypothesis was

that placing the pan and tilt unit under remote operator control would

not significantly affect operator performance when compared to the use

of a stationary perimeter camera.

Based on the results of Test No. 04-85-OMV-02, an OMV bore sight

and perimeter camera were chosen for investigation in this test. The

OMV Requirements Document (1985) specified that one of the OMV cameras

would have pan, tilt, and zoom capabilities. The perimeter camera was

equipped with a pan and tilt unit for evaluation with respect to a

stationary perimeter camera in order to investigate the effects of this

requirement on operator performance.

Four subjects (two women and two men) who had participated in the

previous camera location test were chosen for the pan and tilt

evaluation. The fifth subject from the previous test was not available

for this evaluation.

A Vicon, model V3000PT, pan and tilt unit was mounted on the

vertical extension of the capture device at a distance approximating the

outer perimeter of the OMV (2.29m). A Javelin, miniature, black and

white camera and two theatrical light fixtures were mounted on the pan

and tilt unit. The pan and tilt unit was remotely controlled by the

subjects using a four-way, momentary thumb switch located on the RWS

51
rotational hand controller. A control box on the TOM-B allowed test

personnel to adjust the pan and tilt unit prior to each run. Location

of the pan and tilt unit, lights, and cameras is shown in Figure 3.6.

The four subjects made five test runs under normal laboratory

lighting conditions. Prior to testing, operation of the pan and tilt

unit was demonstrated to the subjects, and they practiced manipulating

the camera with the TOM-B in a stationary position. The pan and tilt

perimeter camera was positioned so that the subject had a picture of the

entire target at the beginning of each run. The subjects were

encouraged to manipulate this camera throughout the run in order to

enhance visual cues at a distance as well as to view the docking pins

and docking device at close range. The 20 test runs with pan and tilt

were compared to the 20 test runs without pan and tilt which were made

by the same subjects during the camera location test. After the test

runs were completed, each subject made one run under a simulated bore

sight camera failure condition. Subjects were not aware that they would

lose the bore sight camera picture 16.0m from the target. The test

conductor attributed the loss of picture to equipment malfunction and

requested that the subject attempt to complete the test run using only

the pan and tilt perimeter camera.

The pan and tilt data were analyzed using one-way ANOVAs with

repeated measures on one factor. Translational error recovery time

during docking increased significantly due to the addition of the pan

and tilt capability, F(l,3) - 47.12, p < .01. Translational error

frequency during docking also increased significantly under the pan and

tilt condition, F(l,3) - 25.00, p < .05. No significant differences in

thruster air consumption or elapsed time for approach and docking,

translational error recovery time or frequency during approach, or in Z

and pitch axes alignment at docking occurred due to the addition of pan

and tilt. Results of the bore sight camera failure runs were not

statistically analyzed. All subjects were able to complete the task

using only the pan and tilt perimeter camera with minimal performance

degradation.

Performance on two out of the ten dependent variables

(translational error frequency and recovery time during docking) was

significantly degraded by the addition of pan and tilt capabilities to

52
ORIGINAL PAGE IS

OF POOR QUALITY

Figure 3.6: Teleoperator Motion Base/Three-Point Capture Device Location

of the Pan and Tilt Unit, Cameras, and Lights

53
the perimeter camera. It was concluded that these differences were due

to the additional control activity required during docking. The

subjects had to tilt the camera down at approximately 3 to 4m from the

target in order to view the capture device/target interface. The

subjects were not trained for this addition to their workload. Based on

the fact that OMV operators would be highly trained, it was concluded

that an OMV pan and tilt perimeter camera would not degrade operator

performance. It was also suggested that the ability to point the

perimeter camera and lights might enhance performance as well as prevent

an aborted mission due to a bore sight camera failure.

The second objective of this test series was to investigate

lighting requirements for the OMV bore sight and pan and tilt perimeter

camera locations. Four floodlight beam width combinations and four

spotlight beam width combinations were employed during the approach and

docking task under dark-side conditions. The null hypothesis was that

performance on the dependent variables would not differ significantly

due to the type of light, the beam width combination, or to an

interaction effect. The dependent variables were thruster air

consumption, elapsed time, translational error frequency, and error

recovery time for approach and docking, and Z and pitch axes alignment

at docking.

Three studies conducted at MSFC were the only sources of background

information available on the topic of teleoperator lighting. In an

initial TMS lighting study, Shields and Henderson (1981) found that

on-board floodlighting was effective for close proximity illumination of

target features. A study conducted under simulated solar illumination

indicated that camera line-of-sight, target alignment, and target

illumination interacted to affect operator performance (Shields,

Piccione, Kirkpatrick, & Malone, 1982). Based on the recommendations of

Test Report No. 03-85-OMV-01, OMV Approach and Docking with Onboard

Flood or Spot Lights, both flood and spotlights were chosen for

investigation in this test.

Three women and two men were chosen from the subject pool to

participate in the lighting test. Three of the subjects had

participated in previous tests. The other two subjects completed the

standard training series, and they practiced the approach and docking

task until their performance stabilized.

54
General Electric (GE), sealed-beam lamps were chosen for use in the

lighting evaluation. These bulbs were the closest commercial

equivalents to flight-qualified lighting available. The floodlight beam

widths were 80 x 20 degrees and 40 x 7 degrees, and the spotlight beam

widths were 5x5 degrees and 10 x 4 degrees. These bulbs were

installed in the capture device light fixtures as required by the

experimental condition under investigation. The lights were pointed to

follow the camera line-of-sight as closely as possible.

The effects of flood and spotlight beam width were tested in a

2 x A x 5 (type of light x beam width combination x subjects) factorial

design. Each of the subjects attempted the approach and docking task

three times under the eight conditions shown in Table 3.1.

TABLE 3.1

TEST NO. 06-85-OMV-03-A EXPERIMENTAL DESIGN

Camera Location

Bore Sight

Perimeter

Bore Sight

Perimeter

Bore Sight

Perimeter

Bore Sight

Perimeter

Type of

Floodlight

80 x 20

80 x 20

40 x 7

40 x 7

80 x 20

40 x 7

40 x 7

80 x 20

Light and Beam Widths

Spotlight

10 x 4

10 x 4

5 x 5

5 x 5

10 x 4

5 x 5

5 x 5

10 x 4

55
Two test conditions (one floodlight and one spotlight condition) were

alternately presented in four test sessions with each subject. The

order of presentation was counterbalanced within and between subjects.

Test runs began with the TOM-B aligned with the target. The Z axis was

offset +20cm and the pitch axis was offset +5 degrees at the beginning

of each run. The on-board lights provided the only illumination in the

flat floor facility.

A 2 x 4 x 5 (type of light x beam width combination x subjects)

ANOVA was applied to the data collected during the lighting test.

Significant differences due to the type of lights (flood or spotlights)

were found in thruster air consumption for approach (F(l,4) = 8.34,

p <.05), elapsed time for docking (F(l,4) = 15.35, p < .05),

translational error frequency during docking (F(l,4) = 36.19, p < .05),

and error recovery time during docking (F(l,4) = 15.87, p < .05).

Performance on each of these dependent variables was degraded by the

spotlight conditions in comparison to the floodlight conditions.

Thruster air consumption for docking tended to be lower under the

floodlight conditions than under the spotlight conditions, F(l,4) =

6.21, p < .10. A statistical trend also occurred in translational error

frequency during approach due to an interaction effect of type of light

and beam width, F(3,12) = 2.74, p < .10. This difference was due to

increased numbers of errors in the 40 x 7 bore sight plus 80 x 20

perimeter floodlight condition and in the 5x5 degree bore sight plus

5x5 degree perimeter spotlight condition. Alignment of the Z axis

tended to be further from ideal when two 80 x 20 degree floodlights or

two 5x5 degree spotlights were used, F(3,12) = 2.70, p < .10.

Results of the lighting requirements test supported previous

findings which indicated that floodlighting improved performance during

docking. The results for approach operations were less definitive.

Thruster air consumption during approach increased when spotlights were

used. The frequency of approach translational errors tended to increase

when -two 5x5 degree spotlights or a 40 x 7 (bore sight) and 80 x 20

(perimeter) floodlight combination were employed. Alignment of the Z

axis tended to be farthest from ideal when two 5x5 degree spotlights

or two 80 x 20 degree floodlights were used. No other differences

occurred during approach operations. Based on the test results, the

56
findings of previous research, and subject comments during debriefing,

it was recommended that an 80 x 20 degree, bore-sighted floodlight with

either a 40 x 7 degree perimeter floodlight or a 10 x 4 degree spotlight

be further investigated.

4.4 OMV Vision Systems: Field-of-View and Light Intensity

Test Report No. 10-85-OMV-04-A

The objectives of this investigation were to review the research on

camera field-of-view (FOV) for the performance of remote operations and

to conduct an empirical evaluation of the effects of the intensity of

the on-board OMV lights on the quality of the remote visual image. A

literature search was conducted on the topics of FOV in military flight

operations and teleoperator FOV research.

A series of studies conducted between 1968 and 1972 investigated

the effects of camera FOV and other aspects of cockpit visual systems on

pilot performance of target acquisition tasks. These three studies were

conducted using a flight simulator with experienced military pilots

serving as subjects. The simulator consisted of a terrain model with

three axes of motion and a gimble mounted camera with three axes of

motion. The simulated flights began at a range from the target of

45,000 ft, and the subject's task was to detect and acquire the target

as quickly as possible.

The first study in this series concerned the effects of FOV, target

to background contrast, and target briefing on detection and recognition

(Ozkaptan, Ohmart, Bergert, & McGee, 1968). FOVs of 4.9, 7.3, 9.7, and

14.5 degrees were investigated. FOV did not affect detection or

recognition when the subjects were briefed on the target area before the

test. When the subjects were not briefed on the target area, the

probability of detection decreased as FOV increased. Slant range to the

target increased as target to background contrast increased and FOV

decreased. The results of the study indicated that a narrow FOV

improved performance when subjects were not briefed on the target area

and when high contrast targets were used.

In the same series, Bergert and Fowler (1970) investigated the

effects of 7.3 and 14.5 degree FOVs, target to background contrast, type

57
of background and static or dynamic flight modes on target acquisition.

Larger visual angles were required for detection and recognition with

the 7.3 degree FOV, however significantly fewer targets were missed than

when the 14.5 degree FOV was used. Recognition in the dynamic flight

mode was most difficult when the 14.5 degree FOV was used. Again, the

narrower FOV was most effective for detection and recognition of high

contrast targets.

The third test in the series (Fowler & Jones, 1972) studied the

effect of FOV on a pilot's ability to detect and recognize a TV

displayed target after it had been detected visually through the cockpit

canopy. FOVs of 4.8, 9.6, and 14.5 degrees were employed as the

simulator approached prebriefed target areas. The time required for TV

detection was significantly lower and range to the target was

significantly longer for the 4.8 degree FOV than for the 9.6 and 14.5

degree FOVs.

Grant, Meirick, Polhemus, Spencer, Swain, and Tewell (1973)

evaluated visual systems for the design of the Free Flying Teleoperator

through manipulator and motion base simulations. The authors

recommended a hybrid stereo-monoscopic system with a 9 to 54 degree FOV,

and stated that the ability to reduce the FOV (zoom) increased both

stereo and monoscopic acuity in distance viewing.

FOV was not specifically tested in the verification test series;

however, some observations on the topic were made. An equipment change

resulted in a reduction the the perimeter camera FOV from 44.8 to 22.4

degrees between Tests No. 04-85-OMV-02 and 06-85-OMV-03-A. Four

subjects participated in both these tests, and their remarks during

debriefing indicated that the wider FOV was preferable for the perimeter

camera. The results of OMV Vision Systems: Operator Control of Zoom,

Focus, and Iris (Test Report No. 10-85-OMV-04-B) indicated that a

variable FOV may be advantageous for the OMV perimeter camera.

Based on available information, it was recommended that a variable

FOV in a range around 4 to 55 degrees be considered for the OMV

perimeter camera and that the FOV be placed under operator control. The

width of a set FOV on one camera and the type of control feedback were

cited as issues requiring further study.

58
The light intensity evaluation was preceded by a review of the

human factors research on the effects of monitor luminance and ambient

lighting on operator performance. Six sources of information on this

topic were reviewed and no consensus of recommended luminance or

illumination was found. The range of suggested video luminance was 30

to 170 cd/m2 and recommended ambient illumination ranged from 100 to

7501ux.

Based on the recommendations of Test Report No. 06-85-OMV-03-A, an

80 x 20 degree floodlight at the bore sight camera location with either

a 40 x 7 degree floodlight or a 10 x 4 degree spotlight located with the

pan and tilt perimeter camera were chosen for investigation. The HST

mock-up was chosen as the target for this evaluation, and the RMS camera

target in the center of the mock-up was used as the reference point for

light/camera alignment throughout the investigation.

The effect of light intensity on the remote monitor image was

evaluated by moving the TOM-B through a typical approach and docking

scenario under dark-side conditions while varying the intensity of both

beam width combinations. The approach/docking scenario is illustrated

in Figure 3.7. Light intensity was varied by voltage inputs from 5 to

12 VDC (+ .05 VDC). Intensity at the RMS camera target, the bore sight

and perimeter camera lenses, and the luminance of both camera monitors

were measured at each approach/docking position with a digital

photometer. The monitor images were also evaluated by test personnel

for clarity and for excessive or insufficient target illumination.

The 80 x 20 and 40 x 7 degree floodlights produced a range of 159

to 560 cd/m2 of bore sight monitor luminance and a range of 67 to 441

cd/m2 on the perimeter monitor. The 80 x 20 degree floodlight combined

with the 10 x 4 degree spotlight produced luminance ranging from 165 to

643 cd/m2 on the bore sight monitor and 76 to 502 cd/m2 on the perimeter

monitor. The acceptable range of video luminance for both monitors (95

to 350 cd/m2) was higher than the range recommended by previous

research.

The evaluation revealed several factors which were cited as

requiring consideration in evaluations of the visual system chosen for

flight. The position of the simulator in relationship to the target was

one of the main factors affecting monitor luminance in the study. The

59
distance to the target as well as camera/light/target geometries should

be considered in future evaluations. The nature of the target surface

(reflective or nonreflective) was also cited as requiring consideration.

It was further suggested that a single intensity setting might not meet

illumination requirements in all OMV missions and that a system which

allowed light intensity to be varied by the operator or other personnel

should be investigated.

2.29m

BORE SIGHT

CAMERA

CAMERA

TARGET

Dimension

Position

Maximum distance to target

50 percent of distance to target

75 percent of distance to target

Docked with target

84 deg.

80 deg.

67 deg.

24 deg.

21.4m

10.9m

5.7m

2.5m

21.3m

10.7m

5.3m

1.0m

Figure 3.7: Camera/Target Geometries of Four Positions in a Typical

Approach and Docking Scenario

60
4.5 OMV Vision Systems : Operato r Contro l of Zoom, Focus , and Iris

Test Report No. 10-85-OMV-04-B

This test was conducted to examine the effect on task performance

of placing the iris of the bore sight camera and the iris, zoom, and

focus of the perimeter camera under operator control. The null

hypothesis was that performance on the dependent variables (thruster air

consumption, elapsed time, translational error frequency, and error

recovery time for approach and docking, and alignment of the Z and pitch

axes at docking) would not differ significantly due to the addition of

the camera lens controls to the approach and docking task.

The OMV Requirements Document (1985) specified that one of the OMV

cameras would be equipped with pan, tilt, and zoom functions. A search

of the NASA Technical Library revealed that no studies specifically

concerning operator control of zoom, focus, and iris functions during

teleoperation were available. In a study to gather baseline data on

teleoperator lighting for solar illumination conditions, Shields and

Henderson (1981) recorded remote monitor images in order to evaluate the

effects of target illumination on the visual image presented to the

operator. They found that when an automatic camera iris was used,

intense light reflected off the target caused the image to be overly

bright, and critical target features were obscured. This image

"blooming" resulted because the automatic iris utilized average scene

lighting to determine the iris setting. The result of averaging a black

background and a highly reflective target was that too much light

entered the lens, causing the image to be overly bright. This same auto

iris effect was noted in Test No. 03-85-OMV-01 of the TOREF verification

test series. Both of these studies recommended that placing the iris

under operator control should be investigated.

Three men and two women were selected from the subject pool for

this test. Four of the subjects had participated in previous tests.

The new subject was trained according to standard procedures and

practiced the approach and docking task under dark side conditions until

performance stabilized.

61
The TOM-B perimeter and bore sight cameras were equipped with Canon

motorized lenses. The bore sight FOV was set at 24 degrees and the

perimeter FOV was variable from 4 to 24 degrees. An 80 x 20 degree

floodlight was located with the bore sight camera, and a 10 x 4 degree

spotlight was located with the pan and tilt perimeter camera. Selection

of these lights was based on the results of the lighting evaluation

previously described, and light intensity was set to produce optimal

monitor luminance in accordance with the results of that evaluation.

The iris of the bore sight camera and zoom, focus, and iris of the

perimeter camera were controlled by the subjects using four toggle

switches located on the left RWS auxiliary control panel (Figure 1.5).

The subjects made five test runs under three camera lens adjustment

conditions. In the baseline condition, the camera lenses were set to

provide optimal visual cues, and no adjustments by the subject were

required. The second, or minimal condition, required the subject to

adjust the irises of both cameras as soon as they had placed the TOM-B

in motion. The moderate adjustment condition required the subject to

manipulate the irises of both cameras and the zoom and focus of the

perimeter camera throughout the task in order to optimize visual cues.

The lens controls were set at positions which were not optimal at the

beginning of each run in the minimal and moderate conditions. Lens

settings were determined using a random numbers table.

The data were analyzed using one-way ANOVAs with three repeated

measures on one factor. With the exception of thruster air consumption

for docking, the null hypothesis that added camera controls would have

no significant effect on performance failed to be rejected for all

dependent variables. Thruster air consumption during docking was

significantly greater in the minimal and moderate conditions than in the

baseline condition, F(2,8) «= 6.91, p < .05. Thruster air consumption

for approach tended to decrease as the frequency of camera adjustments

increased, F(2,8) = 3.95, p < .10. Approach thruster air consumption

was lowest in the moderate condition and highest in the baseline

condition. A trend occurred for elapsed time during approach to be

higher in the baseline condition than in the minimal and moderate

conditions, F(2,8) ** 4.39, p < .10. Error recovery time during docking

tended to be lower under the baseline condition than under the minimal

62
and moderate conditions, F(2,8) = 3.93, p < .10. A trend was evident

for alignment of the pitch axis to be closest to the ideal in the

baseline condition, F(2,8) = 3.80, p < .10.

After testing was concluded, a post-test observation was conducted.

This post-test series was conducted in the same manner as the test 'runs

except that the subjects began the runs with optimal visual cues and

used the camera lens controls at their discretion in order to optimize

the remote image throughout the run. During the test runs and the

post-test observation, video recordings were made of the subjects' use

of the camera controls. These recordings were analyzed in order to

describe the subjects' control behaviors. The subjects made only

slightly fewer adjustments in the post-test observation, when they were

allowed to make adjustments as they chose, than they did in the moderate

test condition when they were forced to adjust the lenses. Under both

conditions, the frequency of adjustments made was approximately four

times higher during approach than during docking.

Based on the results of the test, it was concluded that adding

control of the camera irises and perimeter camera zoom and focus control

to the OMV operator's task would not degrade total task performance and

that performance of approach operations would be enhanced. Subjects'

video recorded control behaviors and their comments during debriefing

indicated that the ability to zoom the perimeter camera and to control

both camera irises would be advantageous to the OMV operator. It was

recommended that this issue be further investigated along with all tasks

required of the operator and in conjunction with reduced video

transmission bandwidth. It was also recommended that iris control be

investigated under solar illumination conditions.

4.6 OMV Operation with Reduced Video Frame Rate

Test Report No. 11-85-OMV-05

The objective of this test was to investigate the effects of

reducing the frame rate of the video image presented to the OMV

operator. The null hypothesis was that performance of the approach and

docking task would not be significantly affected by frame rates of 30,

15, 10, 5, 3, 1, 0.5, and 0.1 frames/second (fr/s).

63
The possibility of drastically reducing the the video transmission

bandwidth from the OMV to the ground control station has been foreseen

for OMV operations. The video bandwidth required for transmission is a

function of frame rate, gray scale, and resolution. A reduction in one

or more of these parameters may result in a substantial reduction in the

required bandwidth. Ranadive (1979) investigated bandwidth reduction

for undersea teleoperation. After varying frame rate, gray scale, and

resolution for the performance of two remote manipulator tasks by two

subjects, Ranadive concluded that performance was not degraded when

frame rate was reduced to 3 fr/s, or when resolution was reduced to

64 x 64 pixels/frame, or when a gray scale of 1 bit of gray/pixel was

employed. Studies of reduced video bandwidth were conducted during the

Remotely Piloted Vehicle (RPV) program. The proposed RPV was a remote

assault vehicle, and three studies were conducted using an RPV

simulator. At the conclusion of this series of studies, the researchers

recommended that a bandwidth compression system which provided

3.75 fr/s, 256 x 256 pixels/frame of resolution, and 1 bit of gray/pixel

be implemented in the RPV design. Systems analysis simulations, which

evaluated 10 bandwidth compression systems, confirmed this

recommendation (Hershberger & Vanderkolk, 1976). In summary, the

previous research indicated that a frame rate as low as 3 fr/s would not

significantly degrade the performance of remote tasks.

The frame rates employed in this test were 30, 15, 10, 5, 3, 1.5,

0.5, and 0.1 fr/s. These rates were chosen in order to cover the widest

range of rates which could conceivably be applicable to the OMV visual

system design. Two women and three men served as subjects in the test;

all subjects had participated in previous TOREF tests.

The TOM-B was equipped with an 80 x 20 degree floodlight at the

bore sight camera location and a 10 x 4 degree spotlight at the pan and

tilt perimeter camera location. Two Tektronix synchronizers, driven by

a wave form generator and a pulse generator, were used to store and

display inputs from the TOM-B cameras at the selected rates. This

system, which allowed continuous selection of frame rates from 0.01

through 30 fr/s, is shown in Figure 3.8.

64
n.

Out

D

Remote

Control

Input

Remote j

Control

Jnput J

Component Specifications

A XES Color Camera (TOM-B Perimeter Camera)

B Panasonic Color Camera, WV-3890-B (TOM-B Bore Sight Camera)

C American Data Distribution Amplifier

D Krohn-Hite Wave Form Generator, model 5400A

E EH Research Labs Pulse Generator, model 710

F Tektronix 110-S Synchronizers, model LR37158

G Mitsubishi Color Monitors, model AM-1301

Figure 3.8: Video System Used to Produce Reduced Frame Rate

65
Each subject attempted the approach and docking task five times

under the eight frame rate conditions. The test was conducted under

dark-side conditions, and the frame rate conditions were randomly

presented to the subjects. In order to avoid introducing an

uncontrollable source of variation into the test results, camera zoom,

focus, and iris controls were not used during the test

One-way ANOVAs with repeated measures on one factor were employed

to test for significant differences in run success, total thruster air

consumption, elapsed time, frequency of translational errors, error

recovery time, and Z and pitch alignment. Run success was significantly

degraded by frame rates of 0.5 and 0.1 fr/s, F(7,28) = 43.62, p < .001,

but was not affected by rates of 1 fr/s and above. Only one successful

v

dock occurred in the 0.1 fr/s condition; therefore, data from this

condition were excluded from further analysis. Total elapsed time was

significantly higher in the 1 and 0.5 fr/s conditions than in the 30,

15, 10, and 5 fr/s conditions, and the 3, 1, and 0.5 fr/s rates resulted

in significantly higher total times than did the 15 and 10 fr/s rates,

F(6,24) = 3.12, p < .025. The effects of zone of operation and reduced

frame rate were analyzed using 2x7x 5 (zone of operation x frame rate

x subjects) ANOVAs. The time required for docking was significantly

higher when the frame rate was 1 and 0.5 fr/s than when the rate was 30,

15, 10, or 5 fr/s, F(6,24) = 3.12, p < .025. The analysis revealed no

difference in the remaining dependent variables due to the frame rate

conditions. Although some trends were evident, no conclusions could be

drawn due to the variability of the data.

The test results demonstrated that the frame rate of the OMV visual

system could be reduced to at least 5 fr/s without affecting operator

performance if the resolution and gray scale were not degraded below

normal levels. The 5 fr/s level was slightly higher than the 3.75 fr/s

rate which repeatedly appeared in previous research as the threshold for

performance degradation. It was concluded that this difference in

research findings was due to differences in equipment capabilities

between the present and past studies. Rates between 7.5 and 3.75 fr/s

were not available for investigation in previous research. This

difference indicated that a range of frame rates between 5 and 3 fr/s

should be subject to further investigation. It was also recommended

66
that reduced frame rate be investigated in conjunction with optical

zoom, command time delay, and degraded resolution and gray scale.

4.7 The Utility of Stereo Visio n for Remot e Operations: A Revie w

The purpose of this review was to develop an annotated

bibliography, examine research findings, gather information available on

the topic of stereo vision, and define the relative advantages and

disadvantages for use with the OMV. The annotated bibliography appears

in the reference section of this report (Section 6.A). A literature

search was conducted from the NASA Technical Library utilizing the NASA

RECON System to gather information on stereo vision. Additional

information was obtained from the Essex Corporation in-house library.

The perception of depth will be important for successful docking,

target acquisition, manipulation, servicing, repair, refurbishment, and

similar activities in support of space operations required of the OMV.

Depth perception from a two-dimensional (2-D) image is obtained as an

observer extracts available monocular and coding cues relative to the

depths of displayed objects. Three-dimensional (3-D) depth perception,

or stereopsis, results from binocular disparity, when each eye views a

scene from a slightly different vantage point with the images fused

together.

Three-dimensional video systems for teleoperation utilize

stereo-pair displays in which a pair of images containing lateral or

binocular disparity appropriate for the relative depth of the objects

is presented. Stereopsis is produced through the utilization of

mirrors, prisms, cross-polarized glasses, red and green filter glasses,

lenticular screens, and alternating shutter glasses. The two most

commonly used stereo display systems referred to in the current research

are illustrated in Figures 3.9 and 3.10.

67
Targets

Figure 3.9: Piezioelectric Lathanum Lead Zirconate Titanate Stereo

Display System

68
Convergence

Point

Flight Configured Fresnel Syatera

Cohu Cameras

TarRCts

Figure 3.10: Flight Configured Fresnel Stereo Display System

69
Most research in the area of stereo display systems compares task

performance using a stereo system with performance using a mono display

system. The results of the studies cited in the reviewed literature

varied greatly, with evidence supporting performance advantages for both

display systems. However, one finding consistently occurred throughout

the studies reviewed: that a mono display system with two orthogonal

views produced similar, if not significantly better, task performance

than a stereo display system. The research findings are presented below

in three categories: those who found performance advantages using a

one-view mono system, a stereo system, or a two-view mono system.

Performance Advantage Using a One-View Mono System

Fredrick, Shields, & Kirkpatrick (1977)

Examining the accuracy of operator range estimation using a

Fresnel TV system with a 3-D cursor and two mono systems with a fixed

and moveable ranging cursor, the authors found that the stereo system

produced a higher overall error percentage than either of the two

monoptic systems. In addition, performance using the stereo system

required triple the performance task time of the mono system.

Performance Advantage Using a Stereo System

Merritt (1982)

The author suggested that the absence of hard data supporting

the use of stereo systems was due to the poor quality of the stereo

systems evaluated in comparisons with mono systems and that in most

experiments the stereo system was inadequately set up. Two studies

were cited to illustrate this point. Kama and DuMars (1964) found no

difference in performance of a peg-in-hole remote manipulator task

when either a stereo or mono system was employed. In a replication

of the task using direct rather than TV viewing, Chubb (1964) found

stereo vision to be significantly better than mono vision. The

author stated that the significant difference resulted from

eliminating the confounding variable of display resolution

70
inequality. Although the author assumed direct viewing was an

appropriate method for eliminating the inequality of display

resolution between stereo and mono systems, he failed to recognize

that direct viewing and display viewing cannot be equated. Comparing

a commonly viewed mono display system with one-eyed vision, which is

an unnatural way of viewing for most individuals, is absurd.

Pepper, Cole, Merritt, & Smith (1978)

Performance on the Howard-Dolman Two-Rod Depth Discrimination

test, performance of a depth perception task using Julesz' dot

patterns, and performance of a remote manipulator task were enhanced

when a stereo display system was employed as opposed to a mono

system. In addition, direct viewing produced better performance than

the two stereo systems used in the tests.

Shields, Kirkpatrick, Fredrick, & Malone (1975)

In the first of two studies comparing stereo and mono displays,

the operators' ability to position a variable target at the same

range as a fixed target was evaluated. Results indicated absolute

errors for the mono system were three times that of the stereo

system. In a similar study with varied video system parameters, the

authors found that performance was equal for both display systems

when an angle between the camera viewing axis and motor axis existed.

It was concluded that the angle caused target separation to become a

lateral dimension on the display. Therefore as the viewing angle

decreased, the reliance on stereo display increased.

Smith, Cole, Merritt, & Pepper (1979)

An evaluation of operators' ability to complete remote

manipulation tasks was compared using a PLZT stereo viewer and a mono

display system under three visibility conditions. With experienced

operators as subjects, performance was significantly better when the

PLZT viewer was employed. With inexperienced operators,

no significant differences were found. The authors stated that

stereo performance produced more errors under all visibility

conditions. In a task in which 1/2 inch rope was threaded through

71
two hoops, performance was best when the stereo display was employed,

and the stereo system provided a significant advantage over the mono

display as visibility and task objects become more complex.

Performance Advantage Using a Two-View Mono Display System

Freedman, Crooks, & Coan (1977)

Several alternative video systems were evaluated in terms of

four remote manipulation tasks. The video systems were a black and

white mono system, a color mono system, a two-view mono black and

white system, and a black and white stereo system. The authors

concluded that for a combination of remote operations, the two-view

mono system had a performance advantage over the other display

systems.

Huggins, Malone, & Shields (1972)

The ability to judge depth and estimate distances between

two offset targets using stereo and mono display systems was

examined in this study. The best distance estimation performance was

obtained with two mono cameras located orthogonal to each other in a

horizontal plane. Performance with a one-view mono system improved

when the camera was positioned above the work surface. The authors

also found that the stereo TV system yielded no better performance

than the one-view mono system regardless of the position of the

monoscopic camera.

Tewell, Ray, Meirick, & Polhemus (1974)

Three evaluations comparing stereo and mono TV systems were

conducted. The authors concluded that the stereo permits adequate

alignment of objects regardless of the difference in viewing angles

and object size and shape. For remote manipulator tasks, the mono

system with two orthogonal views was approximately equal to the

stereo system in terms of performance. The authors recommended the

Fresnel stereo display system for teleoperation. Conclusions based

on this research should be made with caution since no inferential

72
statistics were reported. Additionally, due to the fact that the

Fresnel stereo system was developed by Martin Marietta Corporation,

their recommendation of this system for teleoperation could be

biased.

Most of the research recommending a stereo display system over a

mono system resulted from comparisons with a one camera mono system.

Due to the fact that the OMV Requirements Document (1985) specified that

a minimum of two TV cameras would be required for the OMV, the results

from research comparing stereo systems with one camera mono systems were

not applicable in making recommendations for the OMV. However,

recommendations can be made for the OMV based on the results and

conclusions from research comparing stereo displays and mono systems

with two orthogonal views. All research comparing these systems

indicated that the two systems were approximately equal with respect to

their effects on operator performance. To determine whether a stereo

system should be recommended for use with the OMV, the advantages and

disadvantages relative to those of a two-view mono system should be

examined.

Stereo system advantages include the continued presentation of

three-dimensional scenes regardless of camera location and a resistance

to image degradation by poor visibility conditions. The disadvantages

of stereo systems are increased eye fatigue, which is compounded by

viewing of auxiliary displays and controls, the additional maintenance

of the display system, and increased system cost for the display,

calibration, and sequencing of the sensors. Currently, the only

flight-qualified stereo display system requires two cameras and produces

two signals. If the stereo system is the only display system

implemented in the OMV design, the bandwidth required would be equal to

that of a mono system with two orthogonal views. However, if the stereo

system is used in conjunction with another video system, the bandwidth

required would be significantly increased. A greater bandwidth

requirement presents a problem since a reduction in video bandwidth has

been proposed for OMV operation. One bandwidth reduction technique,

which is under investigation, is reducing the video frame rate. The

73
effects of reduced frame rate on a stereo display system have not been

evaluated. Reducing the frame rate of stereo transmissions may cause

greater eye fatigue induced by the flicker associated with slower frame

rates and may eliminate stereopsis due to the alternating visual images

presented through the stereo display.

Further research on the effects of reduced bandwidth on stereo

display systems is necessary before a stereo system is considered for

implementation in the OMV visual system. Based on the information

currently available, a two-view mono system is the most appropriate

visual system for the OMV.

4.8 The Reconfigurable Workstation, Short Task Comparative Analysis

Test Report No. 11-84-RWS-Ol

This test was conducted to compare the RWS with a workstation

design used in previous teleoperator research and to gather baseline

data for the OMV Ground Control Station Guidelines. The null hypotheses

were that task performance and subject reports of discomfort would not

differ significantly due to the two workstations.

The TOREF required a workstation which combined multiple monitors,

a keyboard, and two 3DOF hand controllers for remote docking analyses.

The RWS was designed by Essex Corporation to meet these requirements

while incorporating the most current human factors guidelines on

workstation design. A review of the workstation design research

revealed that workstations which incorporated adjustable worksurfaces,

keyboards, monitors, and chairs reduced operator fatigue and improved

performance. A summary of this review appears as an annotated

bibliography in Section 6.5.

Six women and six men participated in the study. The subjects were

free of visual and motor impairment and were representative of the

subjects who participated in succeeding TOREF tests.

The RWS (Figure 1.3) was designed with a primary worksurface which

was adjustable from +8 to -6 degrees and supported the operator's

forearms during hand controller operation. The keyboard support panel

was located in the middle of the primary worksurface and was adjustable

from +5 to +22 degrees above the worksurface. The primary monitor panel

74
could be adjusted from 90 to 110 degrees. Task performance on the RWS

was compared with performance on a standard workstation. The standard

workstation was based on a configuration used in the previous

teleoperator laboratory, and its dimensions conformed to human factors

design guidelines. Both workstations contained a 33cm Mitsubishi color

monitor, an RCA Data Terminal, low-profile keyboard, a Kraft Systems

Incorporated hand controller and an Emcor chair. A computer-generated

typing and tracking task were performed on both workstations. The

typing task required the subject to input 100 three to six letter words

after they were prompted on the monitor. The tracking task generated

100 random cursor/target positions on the monitor. The subject's task

was to move the cursor to the target and acquire it by pressing a button

on the hand controller. Both tasks were computer scored. The dependent

variables for the typing task were the time required to input each word

and the number of correct letters. The tracking task dependent

variables were the percentage of targets acquired and the average time

per target.

Each subject performed both tasks on each workstation in sessions

which were separated by at least one week. The subjects were randomly

assigned to groups with respect to order of treatment condition

(workstation) and task order (typing and tracking). The tasks were

explained and demonstrated to the subjects by the test conductor. For

the RWS trials, the workstation adjustments were demonstrated and the

subjects were encouraged to adjust the workstation to provide maximum

comfort. The RWS positions chosen by each subject were recorded. After

task completion on each workstation, the subjects completed a comfort

questionnaire which was based on work by previous researchers.

One-way ANOVAs with repeated measures were used to analyze task

performance. No significant differences were found due to the

workstation used. Performance was also analyzed for differences due to

sex and a sex/workstation interaction. Again, no differences in

performance were evident. The only difference in subject discomfort was

that eight subjects reported increased tension in their wrists when

operating on the standard workstation. The positions of the RWS chosen

by the subjects are shown in Table 3.2.

75
TABLE 3.2

POSITIONS OF THE RWS (DEGREES) CHOSEN BY TWELVE SUBJECTS

RWS Worksurface

Primary Worksurface Keyboard Primary Visual Display

\J —5^- U U V

Subject ~"

1

2

3

4

5

6

7

8

9

10

11

12

Range

Median

-4

+4

-6

+2

-3

+6

-4

-2

+1

-5

-5

-2

-6 to +6

-2.5

14

22

14

21

9

6

13

18

14

8

5

16

5 to 22

14

100

97

90

97

102

104

99

110

98

104

93

99

90 to 110

99

The null hypothesis that performance would not differ according to

the workstation failed to be rejected. It was suggested that the short

task duration (approximately 20 minutes) was not sufficient to induce

subject fatigue. Because the RWS was designed for long-term operations,

no difference occurred in the performance of the short duration task.

It was noted that the reported increase in wrist tension might prove to

be significant during the performance of longer tasks, and it was

recommended that the RWS be further evaluated for the performance of

realistic teleoperator tasks with an eight-hour work shift duration. It

was noted that the full range of RWS adjustments were utilized by the

subjects, indicating that the adjustments should be included in control

76
station design because they would be advantageous, especially for

populations of operators with diverse body sizes.

4.9 Ground Control Station Design Guideline s

The workstation design guidelines presented in this section are

based on the remote workstation requirements of the MSFC/TOREF, and as

such, the findings and recommendations are limited to similar

applications. This does not preclude extending the findings to general

workstation issues, but validating the applicability is the

responsibility of the user organization.

The design guidelines address the human engineering issues

associated with the remote control of and feedback from teleoperated

tasks. They are the result of findings and observations concerning

operator behavior in approach and docking studies conducted at the TOREF

from September 1984 through December 1985. The workstation used in the

evaluations, the RWS, was designed specifically for remote operations in

the TOREF. The purpose of the RWS was to accommodate the hardware

required for remote operations involving multiscreen displays,

keyboards, and flight hand controllers. The workstation was designed to

accommodate a wide range of human operators and to be physically and

functionally reconfigurable. The RWS has been described in detail in

Analysis and Selection of a Remote Docking Simulation Visual Display

System, Contract NAS8-35636 Final Report No. H-84-04.

Based on the tasks conducted in the TOREF over the past two years,

the following workstation design guidelines were developed to support

the design and integration of the OMV ground control console.

Operators

During the operating lifetime of the OMV, a wide range of candidate

pilots and payload specialists will be involved in the program. For

this reason, anthropometric data for the smallest to the largest

potential operator should be used as the design basis for the Ground

Control Console (GCC). The Space Station program is working with the

77
range encompassing the 5th percentile oriental female through the 95th

percentile Air Force male. The specificity of the oriental female is

not given, but current recommendations are to use the 5th percentile

Vietnamese female anthropometry based on the regression equations cited

in the Anthropometric Source Book Volume 1, NASA Reference Publication

No. 1024 (1978).

The RWS was not designed with data from the 5th percentile oriental

female but was based on 5th percentile U.S. female data. Modifications

may be necessary in some aspects of the control and display layout to

accommodate the 5th percentile oriental female and the 95th percentile

U.S. male. This is an issue requiring further design analyses.

Normal visual acuity and hand-eye coordination are anticipated

requirements for remote operators. Color discrimination should be

normal, considering the potential applications of polychromatic

displays.

Training will be the most significant variable which an operator

will bring to the GCC, and it is recognized that training in mission

simulations should be conducted at an operational replica of the GCC.

This will have a positive effect on the transfer of skills and knowledge

from the simulations environment to the operational one. This can be

accomplished by training in the Mission Operations Center during

non-operational periods or by having a dedicated training facility.

Primary Visual Displays

For remote operations, the principal means of information display

is through the use of CRTs which can provide a wide range of information

in a variety of formats. The RWS is currently capable of presenting

televised scenes in color or black and white via two 33cm CRTs and a

127cm large screen display. These CRTs are also capable of displaying

alpha-numeric or graphic data in monochrome or polychromatic formats.

Additionally, any of the three displays may be used to present a

stereoscopic scene to the operator through a field sequential mechanism.

Each display has the necessary controls for adjusting contrast, focus,

brightness, hue and chroma, and horizontal and vertical picture

stability. The two RWS primary displays are mounted in an adjustable

panel on the workstation, and the large screen display is above and

78
beyond this panel. The large screen display provides information to the

primary operator as well as to interested technical specialists who can

view the large screen display without interfering with the operator.

The use of the RWS in the TOREF has generated the following general

visual display guidelines which can be applied to other workstations and

remote operating situations:

Providing operators with two primary displays allowed them to

focus on the more critical scene or the "better" picture during a

remote task. This observation held true even when the two CRTs

displayed the same scene. The operator was free to select the

clearer picture or the preferred right or left display. The system

requirement for redundancy is also served by having two collocated

displays.

Operator access to controls for contrast, brightness,

stability, and chromaticity is preferred. A detent in the

control knobs should be provided to indicate the "set-up" position

of the knob to the operator. This is usually halfway between the

extremes of the control range and should be at a 12:00 o'clock

location.

The capability of adjusting the angle of the primary displays

with respect to the operator's normal line-of-sight should be

designed into the display mount. The RWS permitted adjustment from

90 degrees vertical (in relation to the Y horizon) to 110 degrees

and the TOREF subjects utilized the full range of this adjustment.

This adjustment permitted the operators to accommodate for screen

glare produced by ambient lighting, seat height, comfortable

line-of-sight, and other individual and environmental variables.

It is suggested that this degree of flexibility be incorporated

into other remote systems workstations. Beyond the advantages for

individual operators, this would permit two operators to sit

opposite each other and have face-to-face contact when the display

panels were in the lower positions.

The visual display arrangement and location should permit the

full range of potential operators to manipulate the CRT controls.

This was accomplished in the RWS design by having a significant

portion of the primary worksurface cut out to create an alcove,

79
permitting the operator to move into the alcove and be surrounded

by the primary worksurface on three sides.

Primary Control Spaces

The types of manual behavior required at a workstation should be

considered prior to design. The RWS incorporated two-handed operation

as a design criteria. Two hands were required for operation of the

primary controls—the translational and rotational hand controllers and

the interactive keyboard. The significant differences in the RWS as

compared to other workstations are the independent orientation of the

keyboard with respect to the primary worksurface and the full forearm

support provided for hand controller operation. As noted in the

previous section, the TOREF operators utilized the full range of

keyboard adjustment and complaints of wrist fatigue were lower during

RWS operation than during operation with a conventional workstation. It

is recommended that these two features be incorporated into future

workstation designs.

The primary worksurface of the RWS was designed for the primary

controls required in the TOREF test program (keyboard and hand

controllers). Consequently, the RWS did not provide a flat writing

surface, storage space near the primary worksurface, or significant

space on the worksurface for additional primary controls. Future

workstation design should provide for these requirements as necessary.

The RWS primary worksurface was designed to physically support the

operator and to focus their attention in controlling remote activities.

Design generalizations should be made only to similar modes of control

over similar tasks.

Secondary Control Spaces

Provisions were made on the RWS for test specific or other

specialized controls by including two auxiliary control panels to the

right and left of the primary worksurface. These two sloped panels were

detachable from the worksurface either to provide additional work space

or to reconfigure the secondary controls for specific tests or elements

within a test. The auxiliary control panels were within the reach

envelope and normal visual angle of the 5th to 95th percentile operator.

80
The utility of secondary control spaces will be dependent on the

specific tasks performed at a workstation. It is recommended that

provisions for secondary controls be incorporated into any remote

workstation design.

Secondary Displays

Space within the operator's cone of vision should be allocated for

secondary displays, which are collocated with their corresponding

controls. This was accomplished in the RWS design by allocating space

on the wing panels enclosing the workstation. It is generally

preferable to limit the number of secondary controls and displays

monitored by a single primary operator. Provisions should be made in a

workstation design for infrequently used and non-critical controls and

displays, but every effort should be made to reduce the actual number.

If system and subsystem design dictate that a number of secondary

parameters need to be monitored and manipulated, installing these

parameters in an engineering monitoring and control console should be

considered in order to keep the workload of the primary operator focused

on the main control tasks.

Conclusions

The following conclusions were drawn based on the use of the RWS

during TOREF tests and simulations and on research findings:

1. Operators strongly agreed that control of seat height and

attitude, table height and attitude, and display attitude were

important factors contributing to comfort and performance.

Provisions should be made for individually setting each of these

parameters to the operator's preference.

2. Full forearm support should be provided for the operation of hand

controllers. This may necessitate forearm braces, recessed hand

controllers, or some similar engineering solution to provide a

stable worksurface.

3. Keyboards should be located for bilateral operation. This will

generally mean a location directly in front of the operator.

Additionally, the attitude of the keyboard should be adjustable

with respect to the operator.

81
4. The locations and attitudes of the workstation components should

not be fixed or dictated by the location and attitude of any other

component. Each component location should be optimized with

respect to all other components in a systematic, as opposed to

dogmatic, approach.

5. Engineering convenience should not dictate workstation design if

the goal is to accommodate and maximize the capabilities of the

human operator. The mere availability of 19-inch equipment racks

and flat tables does not justify employing them as workstations for

complex, long-duration tasks.

5.0 RECOMMENDATIONS FOR FURTHER RESEARCH

Future research topics were recommended throughout Sections 3.0 and

4.0. These issues will be outlined in this section along with some

additional OMV design issues which require investigation in the context

of human operator performance.

5. I OMV Visua l System

Camera Location - Determine the effects on operator visual

perception and related performance effects of a camera located away from

the geometric center of the OMV and bore-sighted on a camera target.

Investigate possible interactions of this camera location combined with

a pan and tilt perimeter camera.

Camera Field-of-View - Determine the optimal width of the fixed

bore sight camera and the variable perimeter camera FOVs. Determine

whether position feedback to the operator from the variable FOV is

necessary.

Lighting Requirements - Investigate placing light selection

(floodlights, spotlights, and combinations) and light intensity under

operator control. Evaluate the advantages and disadvantages of a light

pointing system which is independent of the camera pointing system.

Stereo Vision - Investigate the effects of reduced frame rate,

optical zoom, and degraded resolution on the stereo image and on

operator performance.

82
5.2 Vide o Bandwidt h

Frame Rate - Frame rates between 3 and 5 fr/s should be

investigated in conjunction with optical zoom and command time delay.

These issues should be evaluated in the context of long-duration tasks

and with respect to possible operator visual fatigue.

Resolution and Gray Scale - After the optimal frame rate is

determined, reductions in gray scale and resolution may be investigated

in an effort to further reduce the video bandwidth required. Degrading

resolution should be evaluated only after the frame rate, time delay,

and task load issues are resolved.

5.3 Command/Response Time Delay

Variable Interval Time Delay - Determine the effects of variable

periods of transmission network caused time delay. The shortest and

longest possible delay periods should be determined and varying periods

within this range should be introduced into the task in a random manner.

Fixed Interval Time Delay - Determine the effects on performance of

the longest predicted time delay period when present at fixed intervals.

Reduced Frame Rate and Time Delay - The optimal frame rate should

be included in an evaluation with best case (short duration and fixed

interval) and worst case (variable interval) time delays to determine

the effects on performance of these combined parameters.

5.4 Ground Control Station

Task Analysis - An item-by-item analysis of all tasks involved in

generic and specific OMV missions should be conducted.

Task Allocation - Based on the task analysis, the number of

personnel required and their responsibilities should be determined. For

example, a primary operator, secondary operator, and engineering console

operator may be required or two operators may be sufficient.

Task Density Workload Assessment - A range of tasks, from nominal

control of the OMV through emergency recovery of a failed system during

docking, should be investigated in simulations to determine the effects

83
of task density on performance by the primary operator and other

personnel.

Task Duration Workload Assessment - A range of tasks should be

compiled to simulate an OMV mission of realistic duration. This

simulation should last long enough for the effects of fatigue to be

evaluated.

84
6.0 BIBLIOGRAPHY

6.1 General References

Haslam, J.W., Henderson, D.E., Martin, M.F., Shields, N.L., Jr., &

Sulyma, C.D. (1985). Teleoperator and teleoperator thruster

control (Contract NAS8-34726 Final Report No.H-85-04). Huntsville,

AL: Essex Corporation.

Orbital Maneuvering Vehicle Task Team. (1985). Orbital Maneuvering

Vehicle (OMV) requirements document, revision 2. Marshall Space

Flight Center, AL: OMV Program Department, National Aeronautics

and Space Administration.

Shields, N.L., Jr. & Martin, M.F. (1984). Analysis and selection of a

remote docking simulation visual display system (Contract

NAS8-35473 Final Report No. H-84-04). Huntsville, AL: Essex

Corporation.

Shields, N.L., Jr., Piccione, F., Kirkpatrick, M., & Malone, T.B.

(1982). Human operator performance of remotely controlled tasks;

A summary of teleoperator research conducted at NASA's George C.

Marshall Space Flight Center Between 1971 and 1981 (Report No.

H-82-01). Huntsville, AL: Essex Corporation.

U.S. Department of Defense. (1981). Military standards; Human

engineering design criteria for military systems, equipment, and

facilities (MIL-STD-1472-C) .

85
6.2 Visio n Systems

Bergert, J.W. & Fowler, F.D. (1970). Target acquisition studies;

Visual angle requirements for TV displayed targets (Contract No.

N00014-67-C-0340). Washington, DC: Office of Naval Research,

Engineering Psychology Branch.

Billmayer, H., Rodriquez, R.C., & Wheeler, S.C. (1983). Terrain edit

system/evaluation matrix processing system (TES/EMPS) human

engineering study (Subcontract No. B21516). Huntsville, AL: Essex

Corporation.

Cakir, A.F. (1980). Human factors of VDU design. In P.A. Kolers, M.E.

Wrolstad, & H. Bouma (Eds.), Processing of visible language 2. New

York: Plenum Press.

Fowler, F.D., Freitag, M., Jones, D.B., & King, B. (1971). Target

acquisition studies; (1) Two dimensional compared with three

dimensional targets (2) Changes in gamma for TV displayed targets

(Contract No. N0001A-67-C-0340). Washington, DC: Office of Naval

Research, Engineering Psychology Branch.

Fowler, F.D. & Jones, D.B. (1972). Target acquisition studies: (1)

Transition from direct to TV mediated viewing (2) Color vs

monochrome TV displays (Contract No. N00014-67-C-0340).

Washington, DC: Office of Naval Research, Engineering Psychology

Branch.

Grant, C., Meirick, R., Polhemus, C., Spencer, R., Swain, D., &

Tewell, R. (1973). Conceptual design study for a teleoperator

visual system (Contract No. NAS8-29024). Denver, CO: Martin

Marietta Corporation.

isensee, S.H. & Bennett, C.A. (1983). The perception of flicker and

glare on computer CRT displays. The Journal of the Human Factors

Society, 23, 177-184.

86
Martin, M.F. & Paulukaitis, K.R. (1958). OMV vision systems: (A)

Field-of-view and light intensity (B) Operator control of zoom,

focus, and iris (Test Report No. 10-85-OMV-04). Huntsville, AL:

Essex Corporation.

Martin, M.F., Sulyma, C.D., & Paulukaitis, K.R. (1985). Lighting

requirements for two OMV camera locations, revision A (Test Report

No. 06-85-OMV-03-A). Huntsville, AL: Essex Corporation.

Martin, M.F., Young, D.G., & Sulyma, C.D. (1985). OMV approach and

docking with onboard flood or spot lights (Test Report No.

03-85-OMV-01). Huntsville, AL: Essex Corporation.

Martin, M.F., Young, D.G., Sulyma, C.D., & Haslam, J.W. (1985). OMV

camera location; A preliminary investigation (Test Report No.

04-85-OMV-02). Huntsville, AL: Essex Corporation.

Ozkaptan, H., Ohmart, J.G., Bergert, J.W., & McGee, R.A. (1968).

Target acquisition studies; Fixed television fields of view

(Contract No. N00014-67-C-0340). Washington, DC: Office of Naval

Research, Engineering Psychology Branch.

Shields, N.L., Jr. & Henderson, D.E. (1981). Earth orbital

teleoperator systems evaluation test report 1979 - 1980 (Report No.

H-81-01). Huntsville, AL: Essex Corporation.

Stammerjohn, L.W., Smith, M.J., & Cohen, B.G.F. (1981). Evaluation of

workstation design factors in VDT operations. The Journal of the

Human Factors Society, 23. 401-412.

Stewart, T.M.F. (1979). Eyestrain and visual display units: A review.

Displays, _!, 25-32.

Woodson, W.E. (1983). Human factors design handbook. New York:

McGraw-Hill Book Company.

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6.3 Video Bandwidth Reduction

Cole, R.E. & Kishimoto, B.H. (1980). Remote operator performance using

bandwidth limited TV displays: A review and proposal (DTIC No.

AD-A100438). San Diego, CA: Naval Oceans Systems Center.

Hershberger, M.L. & Vanderkolk, R.J. (1976). Video bandwidth

reduction/compression studies for remotely piloted vehicles (DTIC

No. AD-A039762). Wright Patterson Air Force Base, OH: Air Force

Systems Command, Aeronautical Systems Division.

Martin, M.F. & Paulukaitis, K.R. (1985). OMV operation with reduced

video frame rate (Test Report No. 11-85-OMV-05). Huntsville, AL:

Essex Corporation.

Ranadive, V. (1979). Video resolution, frame rate and gray scale

tradeoffs under limited bandwidth for undersea teleoperation (DTIC

No. AD-A087129). Arlignton, VA: Office of Naval Research.

88
6.4 Stereo Visio n (Annotated)

Brye, R.G., Henderson, D.E., Pruett, E.G., Shields, N.L., Jr., &

Slaughter, P.H. (1978). Earth orbital teleoperator systems

Evaluation 1977 year end report (Contract No. NAS8-31848).

Huntsville, AL: Essex Corporation.

A study of three camera types for use with a Fresnel stereo system

was conducted. The cameras employed in the study were COHU Model 2000,

General Electric (GE) TN 2000, and GE, Prototype Charged Induction

Device (CID). Five experienced male subjects participated in a target

alignment task. Two targets (fixed and moving) were prepositioned in

one of three distances from the sensor (fixed 198.12, 223.52, and

248.92cm, moving 203.2, 228.6, and 254.0cm), and subjects were given two

trials to align the targets. Data were collected for operator response

time and error magnitude. No significant differences occurred for the

main effect camera type. A significant difference was found for the

interaction of camera type and positions of the fixed target. As a

function of the fixed target position, the Prototype CID camera enhanced

performance time over the ranges investigated.

A second study evaluated two stereoptic display systems, the Flight

Configured Fresnel System (FCFS) and the Piezioelectric Lathanum Lead

Zirconate Titanate (PLZT) stereo viewer. The results were combined with

data obtained in the first study using the Fresnel lens display system

developed by Martin Marietta Corporation (MMC). The procedures were

identical to those used in the previous study. Significant differences

were found for the main effects fixed target position, initial position

of the moving target, and the display system. An interaction effect was

found for the initial fixed and moving target positions. For all target

positions, mean response time was lowest when the FCFS was used,

increased an average of 2.33 seconds when using the PLZT glasses, and

was greatest when the MMC Fresnel system was used. For signed error,

the interaction of display type and initial position of the movable

target was found to be significant. Here the smallest error in

alignment occurred when the operator used the FCFS. From these two

89
studies, the authors concluded that if a teleoperator mission required

depth perception, the best combination of sensor and display systems

seemed to the GE CID camera system and the FCFS.

Fredrick, P.N., Shields, N.L., Jr., & Kirkpatrick, M., III. (1977).

Earth orbital teleoperator visual system evaluation program

(Contract No. NAS8-31848). Huntsville, AL: Essex Corporation.

Two aspects of this study concerned stereoscopy. The stereo

-ranging test evaluated the accuracy of operator range estimation using a

Fresnel TV system with a three-dimensional (3-D) cursor. It was

discovered that the ranging ability of the stereo cursor system resulted

in a higher overall error percentage than either of the two monoptic

systems previously evaluated. Response time as a function of target

range showed a greater time requirement at the two nearest target

ranges. Although disparity increases as a function of range, the change

in linear disparity over a given change in range decreased with

increasing range. The stereo system required triple the performance

task time of the monoscopic system. It was concluded that viewing with

this system should be limited to areas at or slightly beyond the

convergence distance.

The stereoptic test was designed to evaluate an operator's ability

to align 3-D targets using vidicon tube and solid state TV cameras as

part of a Fresnel stereoptic system. No general differences in response

time due to camera type was evident. The effect of fixed target range

was the only significant effect isolated. The controlled target was

generally positioned at a greater range than that of the fixed target.

For target ranges below 225cm, it was shown that response time using the

solid state system was significantly lower than for the vidicon system.

The researchers concluded that the solid state system is preferable for

short distance alignment tasks or tasks where depth judgement was

necessary. Human operator performance seemed to be enhanced using the

vidicon system for alignment of targets at ranges greater than 230cm.

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Freedman, L.A., Crooks, W.H., & Coan, P.P. (1977). TV requirements for

manipulation in space. Man and Machine Theory, 12, 425-438.

The major objective of these studies was to evaluate several

alternative video systems in terms of task performance. These systems

included a black and white monoscopic system, a color monoscopic system,

a stereoscopic system with two black and white cameras, and a two-view

black and white system. Using these video systems, operators were

required to complete four remote manipulator tasks using toggle switches

to control a 4DOF motion mechanism.

The first task was an end effector coupling task which required the

operator to move the tip of the end effector into alignment with a

socket mounted on the end of a stationary cylinder. The second task was

a cylinder docking task, which required a cylinder attached on the

manipulator to be moved into coaxial alignment with a stationary

cylinder. The third task was a precise positioning task in which the

operator moved a small cube from the starting position between two

horizontal surfaces and positioned the cube in a marked location on the

lower surface. The final task was an obstacle clearance task, which

required the subject to transport a large object between obstructing

surfaces with little clearance allowed. Two levels of the visual system

resolution and four scene parameters were used to modify the four

manipulator tasks.

Eight subjects, with normal vision, participated in the study.

Three replications of each trial were made. Results indicated that

overall performance was best when a two-view system was used.

Specifically, the two-view system produced significantly better

performance when the dependent variable was positioning error. For

performance times, the stereo system produced significantly better

performance than using a monoscopic black and white system. Although no

significant differences were found, fewer contact errors (contact x

seconds) were made when a two-view system and a color mono system were

used than for the stereo system and black and white system. Combined

relative performance was best for the two-view system, followed by the

stereo, color mono, and black and white systems respectively. A

significant difference in combined relative performance occurred between

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the two-view and black and white system. The authors stated, "The

overall results of the experiments indicate that for a combination of

remote operations, there will be a performance advantage for the

two-view system as compared to the other TV systems" (p. 438). However

the relative importance of performance as compared with the burden

(cost, weight, volume, power requirements, maintainability and

reliability) of the system will depend upon the mission in which the

remote operation will occur.

Getty, D.J. Introduction: Three-dimensional displays. In D.J. Getty

(Ed.), Proceedings of a Symposium on Three-Dimensional Displays,

Perceptual Research and Applications to Military Systems (pp. 1-4).

Washington, D.C.: National Academy of Sciences.

In an introduction to the proceedings for a symposium on

three-dimensional displays, the author provided background information

on stereopsis and stereoscopic systems. The perception of depth from a

two-dimensional image is obtained as the observer extracts available

monocular and coding cue relative to the depths of displayed objects.

Depth perception of the three-dimensional image, or stereopsis, results

from binocular disparity, where each eye views a scene from a slightly

different vantage point. Two classes of stereopsis-based displays were

described by the author.

The first class is stereo-pair displays, which are generated by

presenting a pair of images containing lateral disparity appropriate for

the relative depth of the object. The images are delivered to the eyes

by means of mirrors, prisms, cross-polarized glasses, red and green

filter glasses, lenticular screens, and alternating shutter glasses.

Use of stereo-pair displays requires the viewer to maintain a fixed

position relative to the images to avoid the occurrence of visual

discomfort. This type of display is used to reconstruct depth without

knowledge of object location and actual depth, such as is required in

remote viewing of a natural three-dimensional scene.

The second class of stereo displays is a volumetric or

space-filling display. These displays are produced by "rapidly rotating

a flat dense matrix of LEDs through a volume, [by] holograms, and [by]

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displays produced by oscillation movements of a flexible, vari-focal

mirror" (p. 3). Use of volumetric displays permits the viewer to

freely move the head and body, within the limits of the display, to

continuously change perspectives of the scene as is done in natural

viewing. This type of display is used in simulations or modeling

application where depth coordinate information is available.

Grant, C., Meirick, R., Polhemus, C., Spencer, R., Swain, D.,

& Tewell, R. (1973). Conceptual design study for a teleoperator

visual system phase II final report (Contract No. NAS8-29024).

Denver, CO: Martin Marietta Corporation

Of particular interest in this report was the section titled

"Stereoptic Sensor Simulations". The objective of these simulations was

to determine the range and limits of stereo vision (by changing the

camera convergence angle, stereo baseline, and field-of-view) and the

effects of these limits on operator performance. Maximum and minimum

lateral disparity acceptable to the viewer was determined using a

special purpose video synthesizer which generated a 2-D spot on the

stereo display. By controlling the lateral disparity, the spot

separation was increased and decreased such that the viewer's eye

convergence angle decreased and increased until the stereo image was

disturbing or could no longer be retained. Results indicated viewers

could not retain the stereo image when the disparity had exceeded their

interpupillary distance.

Studies to define the limits of the sensor baseline and convergence

angle were also conducted. By randomly positioning in space several

three-dimensional objects, the convergence angle was varied over the

range dictated by the maximum and minimum lateral disparity limits.

This was done until viewers found the scene disturbing. At this point

the baseline was changed, and the process was repeated. Next, the

convergence angle was fixed, and the baseline was varied within the

predetermined limits of lateral disparity. Performance was variable

within and between subjects. The authors found that convergence angles

up to and including 15 degrees caused no obvious eyestrain or visual

discomfort. Convergence angles above 20 degrees were found to cause a

93
lack of stereo acuity or were visually disturbing. A study was then

conducted using a Central Research Laboratories (CRL), Model L

manipulator and a task panel. Subjects were to insert an oak block into

a sequence of three holes oriented at 0, 45, and 90 degrees off the

horizontal. The convergence angle was adjusted so that the line of

sight of the two cameras intersected at a distance of 1.81m from the

cameras. The baseline and convergence angle were again manipulated. The

results indicated as the baseline and convergence angle increased, the

task time decreased until the convergence angle was about 15 degrees

with a baseline of 45cm. Angles above 15 degrees caused task time to

rise sharply. Furthermore, the authors stated that as the baseline

increases, stereo acuity also increases until the 45cm baseline is

reached.

Using the same manipulator task as above, field-of-view (FOV) was

varied. The authors concluded, "the minimal image distortion

encountered with a narrow sensor field-of-view is of little importance

in light of the increased stereo acuity and monoscopicxresolution"

(p.IV34). Vertical disparity was examined using both computer

generated scenes and real scenes. A vertical disparity of + 0.076cm

was found to be tolerable for viewers.

The authors concluded by recommending the following stereoscopic

sensor system parameters:

Stereo Baseline: 6.4cm

Sensor Convergence Angle: 6.8 degrees

Field of View: 9 to 54 degrees (variable).

Huggins, C.T., Malone, T.B., & Shields, N.L., Jr. (1972). Evaluation

of human operator visual performance capability for teleoperator

missions. In Ewald Heer (Ed.), Remotely manned systems;

Exploration and operation in space (pp. 337-350). Pasadena, CA:

California Institute of Technology.

The objective of this study was to identify the specific human

visual capabilities that are associated with requirements for

teleoperator satellite retrieval and servicing. The aspects of this

study that dealt with stereoscopy were the operator's capability to

94
judge depth and to estimate the distance between two offset targets.

Five subjects with normal vision were chosen to participate in the

study.

The three types of targets used were 2-D stationary, 3-D

stationary, and 3-D moving. Each subject was presented with a view of

two targets and asked to judge which was nearer and how far apart the

objects were separated along the viewing axis. It was determined that

the best distance estimation performance was obtained with two

monoscopic cameras located orthogonal to each other in the horizontal

plane. The researchers also found that single camera (monoscopic or

stereoscopic) yielded improved performance when positioned 45 degrees

above the work site. Finally, the use of stereo TV yielded no better

performance than a single monoscopic camera in all comparable positions.

Malone, T.B. (1971). Final report; Shuttle teleoperator system human

factors requirements (Contract No. NASW2220). Alexandria, VA:

Essex Corporation.

In a summary of the stereo visual systems for teleoperation, the

author recommended use of a monoscopic system with orthogonal views for

manipulator capture and satellite servicing. This recommendation was

based on the fact that visual discomfort and head constraints are

associated with stereo systems and that a lack of hard data exist

concerning advantages of stereo over mono systems in remote operation.

Merritt, J.O. (1982). Issues in the evaluation of 3-D display

applications. In D.J. Getty (Ed.), Proceedings of a Symposium on

Three-Dimensional Displays, Perceptual Research and Applications

to Military Systems (pp. 145-149). Washington, D.C.: National

Academy of Sciences.

Discussed were many reasons stereo displays have not been proven

superior when compared with mono displays. One of the reasons cited was

that "the stereo system was a poor quality experimental prototype set up

just for the test, while the non-stereo system was a high quality

commercial display" (p. 146). In addition, the author stated that in

95
many cases stereo systems were not appropriately set up. Therefore the

quality of the picture was degraded, causing eyestrain and discomfort.

It was the opinion of the author that only now could conclusive research

supporting the benefits of stereo display systems be conducted because

state of the art stereo systems are now available for use in the

laboratory (systems with visual comfort and resolution equal to

non-stereo display systems).

To demonstrate how poor resolution and visual comfort affect

subjects' performance, three studies were cited. A 1964 study by Kama

and DuMars examined stereo versus mono performance on a simple

peg-in-hole task using a through-the-wall, master-slave, remote

manipulator with force feedback. TV systems produced stereo and mono

images for task performance. No significant differences in performance

were found between the stereo and mono systems. In 1964 Chubb

replicated the Kama and DuMar study but replaced the TV display systems

with direct viewing. Chubb found that performance using two eyes was 20

percent better than performance using one eye. It was reported that

although the novelty of one-eyed viewing may have accounted for some of

the mono performance degradation, unequal resolution and visual comfort

did not confound the results of the study. [The validity of comparing

stereo and monoscopic TV viewing with natural stereo produced by the

human visual system and monoscopic vision produced by covering one eye

is, at best, questionable.]

Also cited were studies by Smith, Cole, Merritt, and Pepper (1979),

which are reviewed in this bibliography. The studies cited illustrated

the theory that performance using stereo systems is significantly better

than using a mono display system. The author concluded by emphasizing

the point that the methodology in comparing 3-D and 2-D systems

(including a quality stereo system and proper setup) is critical for an

appropriate assessment of the costs and benefits of each system.

96
Pepper, R.L., Cole, R.E., Merritt, J.O., & Smith, D.C. (1978).

Operator performance using conventional or stereo video displays.

Optical Engineering, 17 (4), 411-415.

The authors conducted three studies comparing the effects of

monoscopic and stereoscopic video displays on task performance. In the

first study, five male subjects (with normal or corrected vision)

completed the Howard-Dolman Two-Rod Depth Discrimination task which

utilized three modes of viewing (direct, Fresnel, and Field Sequential).

In addition to mode of viewing, the type of viewing (mono or stereo) was

also used as an independent variable. For all modes of viewing, angular

disparity was less for stereo as opposed to mono viewing. Direct

viewing produced the best performance, followed by viewing with the

Field Sequential system, and then the Fresnel system (differences

between stereo systems were not significant).

The purpose of the second study was to compare the relative

performance of the Fresnel and Field Sequential display ability to

provide detail for stereopsis. Utilizing stereograms, which were

reproductions of Julesz' computer generated random dot patterns that

varied in the percent of common units producing depth cues, subjects

made 40 judgements of the position of a three-level square under the

modes of viewing listed above. Binocularity could be varied between 40

and 100 percent, but the range used in the study was not stated.

Stereograms were presented for 15 seconds to maximize stereo cues.

Subjects judgements were correct 100 percent of the time when

binocularity was 60 percent for direct viewing, 70 percent for the

Fresnel system, and 72.5 percent for the Field Sequential system.

A secondary study was conducted to control for resolution loss resulting

from TV imaging. Two subjects were presented the stereograms for a 5

second interval. No significant differences were found between the

Field Sequential and Fresnel systems. The authors concluded that the

Fresnel display appeared to be less prone to picture quality

deterioration than the Field Sequential system, yet greater fatigue

resulted with the Fresnel display due to the rigid, fixed body position

and restriction of the head position.

97
A link task was used for the final study comparing mono and stereo

viewing. Stereopsis was produced using a Field Sequential display. The

authors failed to define their use of the Field Sequential display or

the Fresnel system for this test. Nine subjects (four were experienced

remotely manned vehicle operators) participated in an end effector

positioning, aligning, and closure task using a CRL Model-L master-slave

manipulator. Results indicated that performance was best when the

stereo display was used.

Shields, N.L., Jr. & Henderson, D.E. (1981). Earth orbital

teleoperator systems evaluation (Contract No. NAS8-31848).

Huntsville, AL: Essex Corporation.

Evaluations concerning detectable stereoptic image discrepancy and

the effects of stereoptic image discrepancy on task performance were

made. Four male subjects were tested. Subjects were seated in an

isolated viewing room that was equipped with a Fresnel lens, two channel

TV display and a remote zoom lens control for either the left or right

camera. The subjects' task was to manipulate the size of one of the

images using the zoom control to eliminate any perceived image

discrepancy. It was determined that the mean errors between the two

displayed target areas can be 1.8 percent and still be considered as

being equal by the operator. A trend was also noted in that alignment

error increased at a gradual rate as image discrepancy also increased.

Shields, N.L., Jr., Kirkpatrick, M., III, Fredrick, P.N., & Malone, T.B.

(1975). Earth orbital teleoperator visual systems evaluation

program (Contract No. NAS8-30545). Huntsville, AL: Essex

Corporation.

Two studies were conducted to evaluate range estimation under

monoptic and stereoptic viewing conditions. The objective of the first

test was to determine the operator's ability to position a variable

target at the same range as a fixed target utilizing either a monoscopic

or a Fresnel stereo display system. A 2DOF target motion generator

98
(TMG) was used to align a variable target with a fixed target. The TMG

was controlled from a box containing a two position travel direction

switch and a knob which controlled the rate applied by the direction

switch. Operators controlled the TMG from behind a curtain with visual

input from the display system (Fresnel stereo or a mono system). The

independent variables were target/background contrast, lateral fixed

target placement, fore/aft placement of the fixed target, initial

position of the variable target, and video system modes.

Each of the four subjects received all 72 combination of the

independent variables, with the display modes presented in blocks and

counterbalanced to control for learning. The remaining variable levels

were randomized in blocks. Each subjects was instructed to maneuver the

variable target via the TMG control box. When the subject judged the

variable and fixed target to be aligned, a response key was depressed

which stopped the timer and terminated the display.

Response time and adjustment error data were collected and

analyzed. The grand mean alignment error for both stereo and mono

systems was found to be significantly different from zero (p < .05).

This indicated that there was a tendency to place the variable target

closer to the fixed target or to overshoot the range. The interaction

of camera system type and the side of the fixed target on which the

variable target was located was significant (p < .01). The authors

suggested that a problem of false depth cues while using the mono system

may have caused this significant difference. It appeared that the

subjects utilized brightness cues resulting from a small right-left

brightness difference which could not be controlled in the laboratory.

Using absolute error as the dependent variable, no significant

differences were found, but mean absolute error for the mono system was

more than three times that for the stereo system. For response time, a

significant difference occurred due to the TMG travel distance

relationship which depended on the fixed target position and the TMG

initial position.

A similar study was conducted which employed varied video system

parameters. The camera was placed in plane with the translational axis

but was offset 45 degrees to the left of the TMG translational plane. A

GRC Random Noise Generator was used to introduce radio frequency (RF)

99
noise with the video signal. A Computer Labs analog/digital and a

digital/analog converter was used to provide a 4 bit digital

transmission format, and a narrow band pass filter was installed to

allow transmission to be limited to 1 MHz. The independent variables

manipulated in the study were target/background and target/target

contrast, initial position of TMG target, initial position of the fixed

target, signal/noise ratio and video transmission. The same subjects

who participated in the previous study were involved in this study. The

subjects were signaled to begin, aligned the targets, and depressed the

response key to indicate the task had been completed. Analyses of

variance on mean errors, mean absolute errors, and response time were

computed. Significant differences were found for the interactions of

contrast and signal/noise ratio (p < .05), fixed target position,

contrast, and transmission mode (p < .05), fixed target position,

contrast, transmission mode, and signal/noise ration (p < .05), and

fixed target position, contrast, transmission mode, and initial variable

target position (p < .05). These findings showed that the video systems

tested were quite insensitive to bandwidth reduction on one channel or

to reduction in signal/noise ratio in terms of constant error. For the

dependent variable, absolute error, significant differences were found

for fixed target position (p < .05), transmission mode (p < .05), and

for the interaction of contrast and transmission mode (p <.05). For

response time, significant effects of; the independent variables were

found to be those associated with obvious correlations between the

initial variable target position, the fixed target position, and the TMG

travel speed.

The authors concluded that subjects performed equally well with

the stereo and mono systems when there was an angle between the camera

viewing axis and the motion axis, thus, causing the target separation to

become a lateral dimension on the display. The authors also stated that

reliance on stereoscopic cues clearly increased as the viewing angle

decreased. In addition, the accuracy of the ability to detect the

relative range between two target objects (range resolution) decreased

with increasing viewing angles for both video systems. However, the

decrease would be greater for the mono TV system.

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Smith, D.C., Cole, R.E., Merritt, J.O., & Pepper, R.L. (1979).

Remote operator performance comparing mono and stereo TV displays;

The effects of visibility, learning and task factors (Technical

Report No. 380). San Diego, CA: Naval Ocean Systems Center.

Three experiments were conducted to compare task performance using

stereo versus mono display systems. Apparatus employed in the

experiments included a CRL Model G, master-slave manipulator, a

modulation transfer function (MTF), and a piezioelectric lathanum lead

zirconate titanate stereoscopic viewer. The MTF was used in these

experiments to simulate different levels of visibility. The PLZT viewer

utilized an electro-optic shutter effect that operated on the principle

of alternately blocking and unblocking the perspective view for each

eye.

In the first experiment, subjects were required to position the

manipulator arm to pick up one peg from the starting block at the right

front of the taskboard, grasp the peg, move to one receiving block and

insert it, then place the second peg in the second block, etc. Six

extensively trained subjects participated in 10 stereo and 10 mono tasks

(a different position was used for each task, and each task was

completed under three levels of visibility—clear followed by moderate

then severe). The results indicated that performance time was better

when stereo was used under all visibility conditions (p < .0025). The

authors reported that performance using the mono system might have been

better had the camera been closer to the task so that critical features

were more finely resolved. Although performance was best when the

stereo system was used, reduced resolution, bothersome visual noise, and

loss of stereo when the eye-base was no longer parallel with the

eye-base on the screen also occurred when the stereo system was

employed.

A second experiment was conducted which replicated the methodology

of the first, but inexperienced subjects were used. Sixteen Naval Ocean

Systems Center (NOSC) employees were used as subjects. These subjects

were instructed to place the pegs in the respective hole, being

extremely careful not to drop the peg or make unnecessary contact with

101
the taskboard. A mixed factorial design was used for this experiment

with display type as the between-groups factor and visibility and trials

as the within-groups factors. Significant differences occurred for the

visibility factor for both performance time and errors. No significant

differences occurred between the mono and stereo display systems. More

errors were observed for stereo in all visibility conditions. The

authors stated that due to a lack of sensitivity in the between-groups

design, the high degree of inter-subject variability in performance

across all trials was responsible in part for the lack of a significant

difference between the stereo and mono systems.

The third experiment involved a task designed to represent line

attachment, sample gathering, and certain salvage tasks. In this task,

the taskboard surface was irregularly shaped and embedded with hoops to

represent marine growth and corrosion. Twenty NOSC employees with

previous remote manipulator experience were instructed to thread a 1/2

inch rope through two hoops designated by the researchers. Ten trials

were attempted under severe, moderate, and clear visibility conditions.

Performance times were 50 percent longer when the mono display was used,

and twice as many errors occurred. Significant differences were found

for the main effects mono-stereo and visibility and for the interaction

of mono-stereo and visibility. The authors concluded that stereo

systems provided significant advantages over mono systems as visibility

and task object complexity become more difficult.

Tewell, J.R., Polhemus, C.E., Skidmore, R.A., Grant, C., Meirick, R.P.,

O'Connor, W.J., Rittenhouse, D.L., & Schlaht, A. (1972).

Conceptual design study for a teleoperator visual system: Vol. 1

technical proposal. Denver, CO: Martin Marietta Corporation.

Discussed in this proposal were various visual systems which may be

employed for use in teleoperation. Three major visual systems were

described: direct view, monocular television, and stereo television.

Direct view, as through a window of the Shuttle or Space Station, would

be the most acceptable to a flight crew because it would be a reliable

and natural system. Limitations of direct viewing included a restricted

FOV due to obstructions and the requirement for operators to be

102
physically close to the work site. Monocular TV, which consisted of a

TV system and an optical radar system included for range/rate

information, optimized resolution, bandwidth, power, mass dimensions,

and controls, but allowed no depth information to be relayed to the

operator. Stereo TV was compared to direct viewing, in which all human

visual perception capabilities such as intensity, position, color, and

depth information were realized.

Four types of stereo display systems were described in detail. One

display was the Fresnel Display Screen developed by Martin Marietta

Corporation. This system consisted of two monitors (one of each stereo

image), two imaging lenses, and a Fresnel display screen. Images from

the two monitors were projected through the imaging lenses onto the

Fresnel display screen to produce stereopsis. According to the authors,

the advantages included optimized image illumination, use of no glasses

or other viewing aids, a FOV which could be designed to accommodate

nearly full peripheral vision, no refocusing of the eyes, retention of

all resolution and color information, and a simple and compact system.

The only disadvantage reported was that head movements are restricted to

±7.62cm of vertical movement and ±15.24cm of forward movement.

The second type of stereo display discussed was the Lenticular

Display. This display is similar to the Fresnel system. Linear mixing

grids are placed over the face of each monitor to divide the pictures

into strips. The images are then combined via beamsplitters and imaged

onto the diffuse screen with right and left image lines interlaced. The

lenticular faceplate divided the right and left image line elements into

zones so that a properly positioned viewer could see a stereo image.

The advantages reported for this system were that no glasses were

required, color information was retained, and vision of peripheral

displays and/or instruments were not impaired. The disadvantages listed

for this system were reduced resolution, reduced FOV, and image

brightness which was not maximized.

The Polarized Display was the third type of stereo system

described. This display employed dual monitors that projected images

into cross polarized filters which were used to separate the right and

103
left stereo images onto a monitor. Cross polarized glasses were used to

separate the right and left stereo images. Advantages of this system

included resolution quality and color information which was similar to

that of the Fresnel system. The disadvantages of the Polarized Display

are that the cross polarized glasses caused eyestrain and confusion when

viewing peripheral instruments and displays and poor illumination

efficiency.

The final display system described was the Color Separated Display.

The two images from the monitors were color-coded and electronically

superimposed onto a single color monitor. Color-coded glasses were then

worn to produced stereo vision. The advantage was that if narrow

frequency bandstop filters were used in the glasses, eyestrain would be

minimal in viewing peripheral objects. The disadvantages were that

color information was lost and the stereo image was disturbing due to

the nature of the color-coded glasses employed to produce the stereo

image.

Tewell, J.R., Ray, A.M., Meirick, R.P., & Polhemus, C.E. (1974).

Teleoperator visual system simulations. Journal of Spacecraft,

Ll(6), 418- 423.

Three evaluations comparing a stereoscopic and monoscopic TV

system were conducted for application in teleoperation visual and motion

simulations. The first study evaluated the subjects ability to align

two objects in a common plane. The independent variables were viewing

dimension (stereo versus mono), viewing angle (30 degree vertical and

horizontal offset, and set at the line of motion), and object size and

shape. The stereo system employed in this study was a Fresnel stereo

system. The results indicated that stereo proved to be consistently

better throughout the test. Camera offset had a greater negative effect

on monocular viewing, with the horizontal offset producing the worst

performance. Objects of different size caused greater performance

degradation when a mono system was used.

The objective of the second study was to evaluate performance on

two manipulative tasks in order to compare a stereo system with a

two-view mono system, and to examine the effects of camera location and

104
lighting on task performance. Using a CRL Model L, master-slave arm

with a general purpose alligator jaw type end effector, the four

subjects were to grasp a block in the right hole of a task board, remove

it, insert it in the left hole, then repeat the process to place the

block into the middle hole, and then into the right hole and leave it.

An additional manipulative task required subjects to grasp a drawer in

the top guide of a taskboard, remove it, place it in the bottom drawer,

then in the middle, and then back in the top guide. The independent

variables used in this study were viewing dimension, camera location,

number of views, and lighting. Based on performance, comments and

forced-choice rankings, the authors stated, "the operators would learn

the task so they could eventually perform it with much degraded visual

cues using kinesthetic feedback. Therefore, task times were somewhat

misleading, and subjective comments were more reliable indicators of

task difficulty" (p. 420). It was concluded that stereo was better than

mono for all camera locations, and that one stereo view was preferable

over two mono views. In regard to camera location, a 45 degree offset

to the right was preferable for a one-view stereo system. For a

one-view mono system, camera location was preferable at the line of

motion because angle estimation problems occurred otherwise. No camera

locations were suggested for a two-view system. The authors stated that

lighting was a critical variable in task performance yet failed to

report any definitive findings regarding lighting location and

intensities.

The third simulation was conducted to investigate remote viewing

requirements associated with retrieving a spinning and nutating

satellite. A Martin Marietta Space Operations Simulator was used in

this study. The simulator was a 6DOF servo-driven, computer-controlled

device which used a gimbaled attitude head to produce three rotational

DOF and a moving base to produce three translational DOF. A

mathematical model was appropriately scaled on an analog computer with

the signals applied to the moving base and the attitude head of the

simulator. The moving base was piloted from a control station. The

task was completed in two phases. The first phase consisted of

estimating the nutation angle and rate and to establish spacecraft

alignment with the nutation axis of the satellite. The second phase

105
required the subject to extend and rotate the retrieval manipulator arm

to match the estimated nutation angle and rate, and then a final

tracking of the satellite spin axis was performed. Subjects preferred

the monocular view because it allowed freedom for head movements,

resulted in less fatigue, and provided better resolution. However, the

authors reported that the stereo system produced better alignment.

Conclusions drawn from this study were that stereoscopic systems

permit adequate alignment of objects regardless of differences in

viewing angles and object size and shape. For manipulation tasks a

two-view monoscopic system and a stereoscopic system were approximately

equivalent. The authors recommended a stereo TV system with a Fresnel

display for teleoperation. They further stated that visual systems are

strongly influenced by the tasks required of the teleoperator. Specific

recommendations and results of these studies should be considered in

light of the fact that the recommended Fresnel system was developed by

Martin Marietta Corporation, and the results are based solely on

descriptive statistics and subjective opinions. Due to the lack of

inferential statistics, no generalizations should be made from the test

results.

106
6.5 Groun d Control Station (Annotated)

Anthropometric source book volume 1; Anthropometry for designers.

(1978). Lyndon B. Johnson Space Flight Center, TX: National

Aeronautics and Space Administration, NASA Reference Publication

No. 1024.

This publication provides a comprehensive tabulation of

anthropometric data. Volume 1 covers basic areas of anthropometry and

its application to the design of workspaces, clothing, and equipment.

The document includes dimensional anthropometric data on 59 variables

for 12 selected populations.

Beldie, I.P., Pastoor, S., & Schwarz, E. (1983). Fixed versus variable

letter width for televised text. The Journal of the Human Factors

Society, 2j>(3) , 273-277.

Variable matrix, a character design in which narrow letters (such

as "i") occupy less space than wide letters (such as "m"), resulted in

improved efficiency on two out of three tasks. This design was

recommended for television screens.

Billmayer, H., Rodriguez, R.C., & Wheeler, S.C. (1983). Terrain edit

system/evaluation matrix processing system (TES/EMPS) human

engineering study. Huntsville, AL: Essex Corporation.

The authors evaluated two VDT workstations from a human factors

engineering standpoint. Their recommended workstation dimensions were:

27 in. to 33 in. (685.8mm to 838.2mm) from top of screen to seat; 42 in.

to 51 in. (1066.8mm to 1245.4mm) from top of screen to floor; 25 in. to

30 in. (635mm to 762mm) from floor to table top. The maximum

recommended viewing distance was 27.6 in (701mm) with an optimum

distance of 15.8 in. to 19.7 in. (401.32mm to 500.38mm). The optimum

eye level was found to be even with the top of the screen. The minimum

acceptable lighting level at the workstation surface was 5401x (50 ft/c)

and the recommended level was 7551x (70 ft/c).

107
Bury, K.F., Boyle, J.M., Evey, R.J., & Neal, A.S. (1982). Windowing

versus scrolling on a visual display terminal. The Journal of the

Human Factors Society, 24(4), 385-394.

In most cases, subjects in the "window" display groups performed

significantly faster and with significantly fewer moves than subjects in

the "scroll" display groups.

Cahill, M. & Carter, R.C. (1976). Color code size for searching

displays of different density. The Journal of the Human Factors

Society, JJ3(3) , 273-280.

Twenty subjects searched for three digit numbers in displays

ranging from 10 to 50 items in density and coded in 1 to 10 colors.

Search times increased linearly with density and curvilinearly with the

number of colors. Adding colors to the display reduced search times

until approximately seven colors were used, after which, search times

increased.

Carter, R.C. (1979). Visual search and color coding. Proceedings of

the Human Factors Society - 23rd Annual Meeting, 369-373.

Search time increased by one order of magnitude when the number of

display items in the target's color increased from one to the display

density. Items not of target color affected search time only to the

extent that their color was similar to target color. Personnel

characteristics - ability and experience - were unrelated to search

speed.

Chao, B.P., Beaton, R.J., & Snyder, H.L. (1982). Evaluation of CRT

displayed digital imagery using subjective scaling. Proceedings of

the Human Factors Society - 26th Annual Meeting, 329-333.

Researchers investigated perceived interpretability of two digital

image degradations - blur and noise. Ten scenes, each degraded by five

levels of blur (20, 40, 80, 160, and 320 micrometers) and five levels of

108
noise (200, 100, 50, 25 and 12.5 s/n ratio), yielded 250 images

displayed on a CRT. As perceived by 15 photointerpreters, the blur,

noise, and interaction effects were significant. At the two lowest blur

levels and the two highest signal-to-noise ratios there were no

differences in interpretability. Otherwise, the reduction in

interpretability was more distinct with increased degradation. In

non-noise images, the addition of blur decreased interpretability in a

linear fashion. With noisy images, the impact of adding blur was

lessened.

Christ, R.E. (1975). Review and analysis of color coding research for

visual displays. The Journal of the Human Factors Society, 17(6),

542-570.

A review of 42 studies between 1952 and 1973 found that color

coding may be a very effective performance factor in some cases and

detrimental in others. Color aided both identification and search if

the color code was known in advance and unique to the target. A problem

occurred when color was used in multidimensional displays; specifically,

when colors were added to an achromatic display, the subject's ability

to identify achromatic targets decreased.

Dainoff, M.J., Happ, A., & Crane, P. (1981). Visual fatigue and

occupational stress in VDT operators. The Journal of the Human

Factors Society, 231(4), 421-438.

One hundred and twenty-one office workers reported relatively high

levels of incidence of eye fatigue symptoms and complaints of glare and

lighting. Complaints appeared to be independent of job pressure and

hostility to computerization.

109
Dodson, D.W. & Shields, N.L. (1978). Man/terminal interaction

evaluation of computer operating system command and control concepts.

Proceedings of the Human Factors Society - 22nd Annual Meeting,

388-392.

No significant differences were found between menu, command

key, and multi-display concepts. The authors recommended that some

combination of command key and multi-display concepts would provide the

best definition for an EGOS command and control service scheme in terms

of human-terminal interaction.

Dodson, D.W. & Shields, N.L. (1979). Development of display design

and command usage guidelines for Spacelab experiment computer

applications. Proceedings of the Human Factors Society - 23rd

Annual Meeting, 70-74.

With regard to display density, the researchers found the response

times increased rapidly as display density exceeded 60%. No

relationship was observed between display density and number of operator

errors. Columns that were functionally arranged had lower response

times. There was no difference in response times related to the percent

of dynamic display parameters.

Emmons, W.H. & Hirsch, R.S. (1982). Thirty millimeter keyboards:

How good are they? Proceedings of the Human Factors Society - 26th

Annual Meeting, 425-429.

The study compared keyboard heights of 30, 38, and 45 millimeters

above a table top 72 centimeters from the floor. Performance on the

higher keyboards was significantly superior to the 30 millimeter height.

Questionnaire data showed significant operator preference for the higher

keyboards.

110
Grandjean, E., Hunting, W., & Piderman, M. (1983). VDT workstation

design: Preferred settings and their effects. The Journal of the

Human Factors Society, 2M2), 161-175.

In this field study, 68 subjects employed by four different

companies performed their regular jobs using a workstation with an

adjustable CRT, keyboard, and chair. Subjects were free to adjust the

components at any time during the study. Preferred settings were

consistent across the five days of the study. Seat heights ranged from

44 to 54cm and keyboard heights ranged from 73 to 97cm. The preferred

CRT angles ranged from 88° to 103° with a mean of 94°. Questionnaire

data revealed that complaints of tension or impairment of the neck,

forearm, shoulders, back, and wrists were much lower in the preferred

settings than in a nonadjustable setting.

Habinek, J.K., Jacobson, P.M., Miller, W., & Suther, T.W. (1982). A

comparison of VDT antireflection treatments. Proceedings of the

Human Factors Society - 26th Annual Meeting, 285-289.

Three antireflection treatments - a micromesh filter, a

quarter-wave length thin film, and an etched face plate - did not differ

in terms of effectiveness. All were preferred to an untreated screen.

Isensee, S.H. & Bennett, C.A. (1983). The perception of flicker and

glare on computer CRT displays. The Journal of the Human Factors

Society, 25(2), 177-184.

Results suggested that low to moderate levels of ambient

illuminance (approximately 100-2601x) and moderate levels of video

luminance (65 cd/m2) minimized discomfort due to direct glare, reflected

glare, and flicker. Video luminance appeared to be a much greater

factor in producing flicker and glare than ambient illuminance. A

filter over the face of the CRT was suggested.

Ill
Kirkpatrick, M. , Shields, N.L., Malone, T.B., & Guerin, E.G. (1976).

A method and data for video monitor sizing. Proceedings of the 6th

Congress of the International Ergonomics Association, 218-221.

Analytical methods based on operator performance were used to

establish monitor size requirements for a particular application.

Formulas for determining monitor size as related to viewing distance,

target size, distance from target to camera, and field of view width

were developed. Authors suggested that because viewing distance is not

constant a useful approach is to plot the equations over a range of

viewing distances. The researchers stated that larger monitors will not

produce improved performance due to resolution limits.

Knowles, W.B., & Wolfeck, J.W. (1972). Visual performance with

high-contrast Cathod Ray Tubes at high levels of ambient illumination.

The Journal of the Human Factors Society, J^(6) , 521-532.

Trace brightness required to perform the visual tasks was

primarily a function of the reflectances and resulting background

brightness of the CRT faces. Background brightness was determined by

the reflectance of the CRT face.

Kolers, P. A., Ducknicky, R.L., & Ferguson, D.C. (1981). Eye movement

measurement of readability of CRT displays. The Journal of the

Human Factors Society, 23(5), 517-527.

Smaller characters (70 per line as opposed to 35) and static

page display were preferred for efficiency of reading.

Kopala, C.J. (1979). The use of color-coded symbols in a highly dense

situation display. Proceedings of the Human Factors Society - 23rd

Annual Meeting, 397-401.

Redundant color-coding (both color and shape coded) significantly

reduced response time and error rate compared to color or shape coding

alone.

112
Martin, M.F., Shields, N.L. & Rodriquez, R.C. (1984). The

Reconfigurable Workstation, short task comparative analysis.

(Test Report No. 11-84-RWS-01). Huntsville, AL: Essex

Corporation.

This study compared a standard teleoperator workstation with the

Reconfigurable Workstation (Shields & Fagg, 1984). A keyboard input

task and a hand controller, cursor positioning task were performed by 12

subjects on both workstations. No significant differences in task

performance occurred due to the workstation used. Subjects reported

increased tension of the wrists when tasks were performed on the

standard workstation. The RWS was designed to maximize operator comfort

during long-duration teleoperation tasks. It was concluded that the

task duration of 20-25 minutes in the test was not sufficient to induce

operator fatigue, thus no difference between the two workstations

occurred.

Miller, W. & Suther, T.W. (1983). Display station anthropometries:

Preferred height and angle settings of CRT and keyboard. The

Journal of the Human Factors Society, 25/4), 401-408.

Thirty-seven subjects ranging in anthropometric characteristics

from the 5th to the 95th percentiles of the population were placed in a

work setting with a CRT, keyboard, and chair. The subjects performed a

text input task after adjusting each of the three workstation components

to their preferences. A -0.71 correlation between seat height and

keyboard angle indicated that the standard fixed keyboard angle of 15°

may be inappropriate for operators who prefer low seat heights.

Preferred keyboard slopes ranged from 14° to 25° with a mean of 18°.

Keyboard heights ranged from 63 to 78cm and CRT heights ranged from 81

to 104cm (measured from floor to center of CRT face). The authors

suggested that the CRT angle be adjustable from -5° to 20°.

113
Mourant, R.R., Lakshmanan, R., & Herman, M. (1979). Hard copy and

cathode ray tube visual performance - Are there differences?

Proceedings of the Human Factors Society - 23rd Annual Meeting,

367-368.

In this study, visual fatigue increased as a function of time as

compared to copy. The amount of information processed had an effect on

fatigue. The authors found that larger amounts of information processed

produced greater visual noise in peripheral vision requiring longer rest

periods. Low display contrast was shown to increase fatigue.

Pastoor, S., Schwarz, E., & Beldie, I.P. (1983). The relative

suitability of four dot-matrix sizes for text presentation on color

television screens. The Journal of the Human Factors Society,

25(3), 265-272.

The authors tested characters with four dot-matrix sizes (5x7, 7x9,

9x13, and 11x15). In all tasks, the smallest size elicited the worst

performance. Qualitative performance was equal for all sizes, however,

time varied up to 20%. The 9x13 size (9 horizontal rows of 13 dots

each), which subtended an angle of 17 minutes of arc, was rated

significantly better than the smaller sizes.

Shields, N.L. & Fagg (Martin), M.F. (1984). Analysis and selection of

a remote docking simulation visual system. (Contract NAS8-35473

Final Report No. H-84-04). Huntsville, AL: Essex Corporation.

This report describes the design of the Reconfigurable Workstation

(RWS). The RWS was developed for use in the Teleoperator and Robotics

Evaluation Facility at NASA's Marshall Space Flight Center. The design

was based on findings from human factors research concerning the impact

of workstation design on operator performance. The RWS accommodates

operators ranging in size from the 5th percentile U.S. female to the

95th percentile U.S. male. The RWS provides three CRTs, two hand

controllers, a keyboard, and auxiliary controls and displays. The

workstation is reconfigurable with respect to the individual operator

and to specific task requirements.

114
Shields, N., Piccione, F., Kirkpatrick, M. & Malone, T.B. (1982).

Human Operator Performance of Remotely Controlled Tasks; A Summary

of Teleoperator Research Conducted at NASA's George C. Marshall

Space Flight Center Between 1971 and 1981. Huntsville, AL:

Essex Corporation.

The authors reported that high contrast, analog signals and

adequate signal-to-noise (S/N) separation yield the best recognition of

shapes and patterns. Target to background contrast was determined by

the following formula:

(R of B) - (R of T)

% contrast = 100 x _ ' ^ _

R of B

where R = reflectance, B = background, and T = target.

Brightness discrimination between two targets was enhanced by contrast

values of .25. For size discrimination between two targets, contrast

ratios of .6 should be used. Analog signals were found to enhance

visual acuity, brightness discrimination, and character recognition.

Character recognition was also improved by high contrast and a 32 dB

S/N. The character font recommended was futura demibold with a

character height of 30 arc min., character width of 23 arc min., and

stroke width of 5.5 arc min. S/N below 15 dB significantly degraded

performance while a S/N above 21 dB did not exert a negative influence.

Orthogonal monoptic camera pairs yielded good results in judgment of

separation of targets. Split field stereoscopic systems yielded less

accurate results.

Shute, S.J. & Starr, S.J. (1984). Effects of adjustable furniture on

VDT users. The Journal of the Human Factors Society, 26(2),

157-170.

Fifty-seven telephone operators served as subjects in this eightweek field study of advanced furniture design for VDT workstations. The

advanced work table and chair were characterized by dimensions that were

easily adjustable by users in comparison to a conventional table and

115
chair which provided no means of adjustment or inconvenient adjustments

that could only be made with difficulty. Four combinations of advanced

and traditional components were compared. Although on-the-job

discomfort was reduced when either of the traditional components was

replaced by an advanced component, the effect was far greater when the

advanced chair and table were used in combination. Each adjustment on

the advanced workstation was used by at least 70% of the subjects every

day. Subjects reported statistically significant reductions in discomfort and intensity of discomfort in 8 out of 15 areas of the body. The

authors concluded that because working posture is heavily dependent on

the task performed, the ease of adjusting the advanced station was the

most influential factor in the obtained results.

Sidorsky, R.C. & Parrish, R.N. (L980). Guidelines and criteria for

human-computer interface: Design of battlefield automated systems.

Proceedings of the Human Factors Society - 24th Annual Meeting,

98-102.

The authors devised a format for recasting human factors data

into a form that makes it more digestible for other members of the

design team.

Stammerjohn, L.W., Smith, M.J., & Cohen, B.G.F. (1981). Evaluation

of work station design factors in VDT operations. The Journal of

the Human Factors Society, £3(4), 401-412.

An onsite evaluation at five establishments examined VDT

workstation designs and compared them to recommendations in the

literature. Design factors evaluated were keyboard height, screen

position, illumination, and glare. Ambient illumination of

500-7001x was found to be acceptable. Problems encountered were

excessive keyboard height (75cm from floor to home keys), screen angle

(a 10-20 degree angle was recommended), and reflected glare. The

authors recommend that the keyboard be placed at or below elbow height

to reduce forearm fatigue. Elbow height varies between the 5th and 95th

116
percentiles from 60.5cm to 82.0cm; therefore, the authors recommend a

wide range of adjustability in workstation designs.

Suther, T.W. & McTyre, J.H. (1982). Effect on operator performance

of thin profile keyboard slopes of 5°, 10°, 15°, and 25°.

Proceedings of the Human Factors Society - 26th Annual Meeting,

430-434.

An IBM Datamaster (System 123) keyboard was set at a 5°, 10°, 15°,

and 25° angle on a table top 685.8mm from the floor. Sixteen

experienced subjects typed in each of the four conditions. No

significant differences were found in performance. Subjects reported

that the keyboard was uncomfortable at 5° and 25° and that they noticed

no difference between 10° and 15°. The authors recommended a setting of

Tullis, T.S. (1980). Human performance evaluation of graphic and

textual CRT displays of diagnostic data. Proceedings of the Human

Factors Society - 24th Annual Meeting, 310-316.

Four CRT display formats - narrative text, structured text, black

and white graphics, and color graphics - were evaluated with respect to

speed and accuracy of response. Accuracy did not vary with display.

Initially, response to graphic formats was faster. With additional

practice, response to textual formats was just as fast as response to

graphics .

Tullis, T.S. (1981). An evaluation of alphanumeric, graphic, and

color information displays. The Journal of the Human Factors

Society. 23(5), 541-550.

Speed and accuracy of subjects interpreting alphanumeric, graphic,

and color coded displays were measured. Accuracy did not vary with

format. Response time for graphic formats was consistently shorter than

for the narrative format. No significant difference was found in

response times for black and white versus color graphics.

117