IMPLEMENTATION OF THE

SURFACE ROUGHNESS

INSTRUMENT (SRI) CONTROLLER

NISTIR 88-3794

PUBLICATIONS

8yj

Howard T. Moncarz

Theodore V. Vorburger

June 2, 1988

issued

September, 1988

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IMPLEMENTATION OF THE SRI CONTROLLER

Howard T. Moncarz

Theodore V. Vorburger

June 2 , 1988

This publication was prepared by United States Government

employees as part of their official duties and is, therefore, a work of the U.S. Government and not subject to copyright.

Certain commercial equipment, instruments, or materials are

identified in this paper in order to adequately specify the

experimental procedure. Such identification does not imply

recommendation or endorsement by the National Bureau of Standards,

nor does it imply that the materials or equipment identified are

necessarily the best available for the purpose.

TABLE OF CONTENTS

Page

I. INTRODUCTION 1

1. WHAT THIS DOCUMENT IS ABOUT 1

2. AUDIENCE 1

3. OVERVIEW 1

II. TOP LEVEL DESCRIPTION OF THE SRI CONTROLLER 3

1. DESCRIPTION OF THE EQUIPMENT (SRI AND ADI) 3

2. LOCATION IN THE WORKSTATION ARCHITECTURE 3

3. MAIN CONTROLLER FUNCTIONS 8

4. WORK ELEMENTS AND STATUSES 8

III. THEORY AND OPERATION OF THE SRI 9

1. THEORY 9

2. OPERATION 12

3. RELATED RESEARCH 14

IV. DATA STRUCTURES 19

1. LOCAL DATA 19

2. AMRF DATA 19

V. TASK DECOMPOSITION 21

1 . irc_sr i 21

2. task 21

3 . surfaces 2 3

4 . points 2 3

5. dial 24

6. sri 24

i
Page

VI. PROCEDURE MODULES 25

1 . sr i_lib 25

2 . gr aph_l ib 2 5

3. display. 25

4. sri_types . 25

5 . sr i_pr ims . 26

6 . readsr i 2 6

7. get_data. 26

8 . rpt_funcs 26

VII. INTERFACE TO EQUIPMENT . 27

1. MODULES THAT INTERFACE TO EQUIPMENT 27

2. DETAILS OF THE CURRENT IMPLEMENTATION 27

3. CHANGES REQUIRED FOR EQUIPMENT SUBSTITUTION 27

VIII. INITIALIZATION AND SHUT DOWN 29

1 . START UP 29

2 . SHUT DOWN 29

3 . ABORT 29

IX. ERROR HANDLING 31

1 .. INTENSITY ERROR 31

1.1. Description 31

1.2. How Handled 31

2. SOFTWARE ERROR 31

2.1. Description 31

2.2. How Handled 31

i i
Page

3. DETECTOR ERROR 32

3.1. Description 32

3.2. How Handled 32

X. USER INTERFACE 33

1. STAND-ALONE OPERATION 33

2. USER COMMANDS 33

XI. FUTURE PLANS 35

1. OPERATIONS 35

2. ROUGHNESS SENSING 35

XII. ACKNOWLEDGEMENTS 37

APPENDICES

A. IWS DOCUMENTATION LIST 39

B. REFERENCES 41

C. GLOSSARY (and abbreviations) 43

D. FLAT FILE SPECIFICATIONS 45

READER COMMENT FORM 49

iii
LIST OF FIGURES

Pa_gje

Figure 1 Photograph showing the IWS robot positioning

a part in front of the SRI 4

Figure 2 Schematic diagram of the optical system of the

SRI 5

Figure 3 Automatic Dial Indicator, 6

Figure 4 Logical Architecture of the IWS. 7

Figure 5 Typical scattering distribution as measured by

the SRI 11

Figure 6 Details concerning optical alignment errors 13

Figure 7 Rq values measured with a stylus instrument vs.

Sjj values obtained from the SRI 16

Figure 8 Control Levels for the SRI Controller 22

iv
IMPLEMENTATION OF THE SRI CONTROLLER

I . INTRODUCTION

1. WHAT THIS DOCUMENT IS ABOUT

This document describes the implementation specifics of the

surface roughness instrument (SRI) controller program. The SRI is

part of the inspection workstation (IWS) in the Automated

Manufacturing Research Facility (AMRF) in the Center for

Manufacturing Engineering at the National Bureau of Standards.

The AMRF and IWS are rapidly developing systems with continually

evolving software. This report describes the SRI Controller

program in place in March 1987. However, certain more recent

features are highlighted where appropriate. This program runs

under the control of the ECS program described in the document

Implementation of the Execution Control System of the Inspection

Workstation [A. 2], The SRI Controller program consists of state

machine modules that "customize" the controller for its particular

app 1 icat ion- - i . e . supervising the SRI.

2. AUDIENCE

Anyone who needs to understand the internals of the SRI software

should read this document. This includes anyone who will continue

the development of the SRI software or make modifications to it.

The document Architecture and Principles of the Inspection

Workstation [A.l] describes the principles that the execution

control system (ECS) and SRI Controller programs utilize. It is

recommended that that document be read first.

3. OVERVIEW

Chapter II gives a top level description of the SRI Controller

(SRIC). It describes the equipment, specifies the location of the

SRIC in the control hierarchy of the IWS, and describes the main

functions the controller performs.

Chapter III discusses the theory that the SRI uses to measure

surface finish.

Chapters IV through X explain the implementation specifics of the

SRIC program. Chapter IV describes the important data structures,

both global to the AMRF as well as local to the IWS. The main

functions that the SRIC performs are specified in Chapter V.

These functions are decomposed hierarchically into separate task

modules, and this decomposition is described in this chapter.

Additionally, the task modules use functions and procedures that

1
SRIC Implementation

are specified in separate procedure modules. These modules are

described in Chapter VI.

The actual interface to the SRI is specified in Chapter VII.

Specific details used in the start up and shut down procedures are

described in Chapter VIII. Errors that can occur during operation

are listed and briefly explained in Chapter IX. Chapter X

describes the user interface to the SRIC.

Finally, Chapter XI discusses future development plans for the

SRIC.

The appendices include further information and implementation

details. Appendix A lists the entire IWS documentation set.

References specific to the SRI are listed in Appendix B. Appendix

C contains a glossary of terms used in this document.

Appendix D specifies the internal file formats used to contain all

the data used for a specific inspection.

Completing the document is a reader/comment form. You are

encouraged to write down your comments and mail the attached form

to the address specified.

2
SRIC Implementation

II . TOP LEVEL DESCRIPTION OF THE SRI CONTROLLER

The SRI Controller (SRIC) supervises the surface roughness

inspection of a part. It controls two pieces of equipment -- the

surface roughness instrument (SRI) and the automatic dial

indicator (ADI).

The SRI monitors surface roughness by measuring the angular

distribution of light scattered from the surface of a part. It

does its job in coordination with the IWS robot. Using the SRI

optical signals as sensory input, the robot properly aligns the

part in front of the SRI so that a valid optical scattering

reading is obtained. Figure 1 shows the robot positioning a part

for an SRI reading.

1. DESCRIPTION OF THE EQUIPMENT (SRI AND ADI)

• _ The SRI consists of two main components: a commercial Rodenstock

RM 400 optical scattering sensor [B.l] and an electronic control

box. The sensor contains an infrared light source and detectors

mounted in a tube (see Figure 2). The light is shined in a

focused beam on the surface of a part. The light scattered back

is measured by a linear array of twenty detector elements. Based

on empirical analysis, a value for rms roughness is estimated.

Additionally, an automatic dial indicator (ADI) is used along with

the SRI to enable the robot to position a part at about 2

millimeters away from the sensor of the SRI. The dial indicator

consists of a spring loaded plunger, that will record the distance

it is depressed, and the electronics to control and monitor it

(see Figure 3). When the robot presses a part against this

indicator, a reading of how far the plunger has been depressed is

recorded and later used for positioning the part in front of the

SRI.

2. LOCATION IN THE WORKSTATION ARCHITECTURE

As shown in Figure 4, the SRI Controller is subordinate to the

Inspection Robot Controller (IRC) and is the supervisor to the SRI

and the ADI. In a future implementation, the SRI Controller will

be able to access the IMDAS (Integrated Manufacturing Data

Administration System), the distributed data system which provides

common interfaces to the AMRF's user programs and underlying

databases [B.17, B . 1 8 ]

3
SRIC Implementation

Figure 1. Photograph showing the IWS robot

positioning a part in front of the SRI

4
SRIC Implementation

IR Led

Collimating

Lens

Measuring

Lens

Surface

Diode Array

Light Scattering

Pattern

Figure 2. Schematic diagram of the optical

system of the SRI

5
Figure 3. Automatic Dial Indicator
SRIC Implementation

Figure 4. Logical architecture of the IWS.

7
SRIC Implementation

3. MAIN CONTROLLER FUNCTIONS

The main functions of the SRI Controller are the following:

Respond to IRC commands and return status information.

Retrieve inspection programs from the IMDAS

Control and monitor the SRI and the ADI . Request the robot to reposition the surface in front of

SRI . the

Analyze SRI data . Report inspection results back to the IMDAS.

Display inspection results on the SRIG's monitor.

4. WORK ELEMENTS AND STATUSES

The SRI Contr

These command

start up/shut

operating in

direct the ma

oiler receive

s are either

down pro toco

ready state)

,

in con troller

s commands from the Robot Contro

transition commands (involved in

1), or work order commands (for

which contain the work elements

functions described above.

1 1 e r . the

that

The work elements executed by the SRI Controller are:

LOAD_PART (loads the data for a part inspection),

READ_DIAL (read ADI and send that reading back to IRC),

INSPECT (directs the part inspection).

Statuses returned by the SRI Controller to the Robot Controller

are : WORKING

,

DONE , ERROR.

8
SRIC Implementation

III . THEORY AND OPERATION OF THE SRI

1 . THEORY

A schematic diagram of the SRI optical system is shown in Figure 2

[B.l]

The source consists of a light emitting diode (LED) that

produces radiation at a near infrared wavelength of 800 nm . This

radiation passes first through a collimating lens, then through

one side of a special measuring lens that focuses and redirects

the radiation, so that it illuminates the surface to be measured

at a slight angle, but very close to the optical axis. The

radiation scattered by the surface then passes through the other

side of the measuring lens and is redirected to a linear

photodiode array which measures a line sample of the scattered

light beam to obtain an angular distribution of light intensity.

If the surface is smooth, the pattern of scattered light falling

on the diode array is nearly the same as the circular pattern of

the incident beam leaving the collimating lens. If the surface is

rough, the scattered radiation pattern is broadened. When the

pattern of marks (lay) left on the surface by the finishing

process is unidirectional, the scattered radiation pattern is

elongated along the roughness direction. Many kinds of finishing

processes, including milling, grinding, and turning, leave

unidirectional machining patterns on the surface and hence yield

elongated scattering patterns. Figure 2 shows the SRI with the

proper rotational alignment for sensing the unidirectional surface

roughness, since the long axis of the array is parallel to the

elongated scattering pattern.

Important parameters of the optical system are the angle of

incidence of the light (a), the angular resolution and angular

range ( <f> ) of the detected scattering pattern, the illumination

spot size y' , and the axial distance of the surface from the

measuring lens. The SRI gauge at the IWS has an angle of

incidence of about 8.4° [B.l]The angular range of the detector

array is ±15° about the center detector. It is determined by the

length of the diode array and the focal length of the measuring

lens. Since there are 20 detectors in the array, the angular

resolution is about 1.5°. The illumination spot size is ~1.8 mm

in diameter. Since the SRI gauge was designed to be insensitive

to misalignment in the axial direction [B.l], the axial distance

of the surface from the measuring lens may vary by ±2 mm without

inducing significant change in the readings obtained.

9
SRIC Implementation

The sensor outputs a light scattering parameter called that

serves as a measure of surface roughness condition. The unitless

parameter Sfj is proportional to the variance of the light

scattering distribution about the mean (M) of the data. Figure 5

shows a typical bell-shaped, 1 i gh t - s ca t t e r ing distribution as

measured by the gauge. The distribution is composed of 20 diode

readings indexed as i = 1,2, •••,20 with intensity values I^.

The mean value M of the distribution with respect to the center of

the array is then given by

20

M = (1/1) l Ii • (i - 10.5)

,

(1)

i = l

where I is the sum of the 20 intensity values of the array and the

center of the 20-diode array is halfway between the tenth and

eleventh diodes (i = 10.5). The light scatter parameter Sfj is

then given by

20

S N = (*/I> l I i ( i - 10.5 - M) 2

. (2)

i = l

where k is a normalizing factor that yields an Sjg value of 100 if

all of the intensity values 1^ are equal.

In general, the value of Sjj increases as the roughness of the

surface increases. As shown in other experimental and theoretical

studies [B.3-B.10], the shape of the angular distribution is a complex function of roughness irregularity heights, height

distributions, and spacings. All these properties cannot be

boiled down to a single parameter. However, for a given type of

surface, the single Sjj parameter may be used to establish a

relative measure of roughness heights. Therefore, we use the S^

value as a comparative estimator of roughness averaging parameters

such as the root mean square roughness Rq or the roughness average

R a [B.ll]. In addition to Sjj, the system also outputs the values

of M and I and the 20 intensity values of the array.

Two calibration checks should be performed on the SRI before using

it with the IWS . These should normally be performed once a week,

unless the SRI results are suspect. In that case, the IWS should

be stopped and the SRI recalibrated. The first calibration is a procedure for nulling the dark current of each detector in the

array. This is accomplished by holding a special light absorbing

cell over the nosepiece of the detector head and following the

manufacturer's instructions for the nulling procedure.

10
DISTRIBUTION

OF

SCATTERING

LIGHT

SRIC Implementation

o'#

n

o

o

Fj

CT» m

ro

iZ.

in

Figure 5. Typical scattering distribution

as measured by the SRI

1 1
SRIC Implementation

Second, a check should be made of the gauge response for a smooth

surface. To accomplish this, a small mirror may be held against

the nosepiece. The angular distribution and Sjj reading are then

recorded and compared with results from the manufacturer's setup

procedure. After this, the SRI is ready to use.

For a flat surface the gauge may be easily aligned to yield an

appropriate Sjj reading. This can be shown by referring to Figure

6 and considering the three angular misalignment errors that can

occur. If the gauge is misaligned by rotation about the x-axis

(Fig. 6a), the misalignment can be sensed and corrected by

rotating the gauge so that the peak of the distribution is at the

center of the array. If rotation around the y-axis is the

problem, the scattering pattern will move off the axis of the

array (Figure 6b) and will result in a value of total intensity I that is less than the maximum. Therefore, the gauge orientation

around the y-axis can be manually corrected to yield a maximum

value for I. Finally, if the gauge is misoriented by rotation

around the z-axis, the radiation pattern falling on the diode

array will appear to be narrower than it actually is (Figure 6c).

Hence, the gauge can be properly oriented by looking for a maximum

Sfl reading as it is rotated about the z-axis.

2. OPERATION

The robot begins the SRI procedure by picking up a part from the

tray. Under the present manipulation constraints in the IWS , the

robot always presents the bottom of the part, as it sits on the

tray to the SRI for roughness inspection.

The axial alignment procedure then follows with the aid of the

dial indicator (ADI) located near the SRI sensor and oriented

parallel to it. The robot moves the part to a position about 25

mm in front of the ADI and then moves the part towards the gauge

in 12.5 mm steps until the part contacts the gauge and a reading

is made of the axial part position. Once this axial alignment is

made, the part is moved in front of the SRI sensor to the optimum

axial position about 2 mm from the nose piece.

After axial positioning, the angular alignments with respect to

pitch, yaw, and roll are made. This is called tweaking.

The pitch correction is performed by first measuring the angular

distribution of scattered light and storing the twenty diode

values in the SRI Controller. Then the SRI program determines how

far the peak of the distribution is located from the center of the

array, and the robot makes a pitch correction of the part to bring

the distribution on center.

12
SRIC Implementation

a. Pitch:

Peak Moves

/

b. Yaw:

I Decreases

c. Roll:

Sn Decreases

Figure 6. Details concerning optical

alignment errors

13
SRIC Implementation

The yaw correction is done next using a peak searching algorithm.

The robot steps the part in a yawing mode in one-degree increments

until a peak in the intensity signal I is located. This position

should closely correspond to the optimum alignment in yaw.

Finally, the part is rolled about the z-axis as shown in Figure 6c

under the direction of a peak- searching algorithm until a maximum

value of Sfl is found. This is done in two stages: first, in tendegree increments to achieve a coarse alignment, then in onedegree increments in the neighborhood of the first maximum to

achieve finer alignment.

After the three-fold alignment, the optimized value of Sjj is

stored as an indicator of the surface roughness condition.

Much of the data used by the SRI Controller for part alignment is

displayed on the SRI console. This includes the Sjg value, the

total intensity I, a dump of the twenty intensity values of the

diode array, a graph of these similar to Figure 5, and the array

positions of the highest three intensity peaks in terms of the

index i. In addition, two graphical indicators showing the

rotation of the part in yaw and roll are also displayed. All of

this information is updated each time the robot steps the part

during the alignment procedure.

After the S$ value is recorded, the robot displaces the part

sideways by about 1 mm, and the alignment procedure is repeated

for a new position on the same surface.

3. RELATED RESEARCH

We are in the early stages of developing a database that will

utilize the readings from the SRI for specification of the

roughness of mechanical parts.

Standard practice in roughness specification is the use of

roughness average R a [B.ll], or alternatively the rms roughness Rq

as ordinarily measured by contacting stylus instruments. In the

future it is possible that the optical scattering parameter S^

itself may also become a standard one in engineering practice or

that ongoing research to obtain geometrical roughness parameters,

such as Rq , from the light scattering distributions in a rigorous

manner will be successful.

At present we are performing comparator studies to relate

values as measured by the SRI with Rq results as measured by a Talysurf 6 stylus instrument.

14
SRIC Implementation

The first set of results has been obtained for hand lapped

stainless steel parts [B.12] with finishes similar to those that

might be obtained on the cleaning and deburring workstation of the

AMRF [ B . 1 9 ] . The results are shown in Figure 7 where Rq values as

measured with a stylus instrument are plotted versus Sjj values as

measured with an SRI model identical to the one at the IWS . These

data are represented by crosses (+'s). A best-fit curve to

describe the correlation between Rq and is also shown.

Two observations constrained the form of the function that we

fitted for Rq vs. Sjg- First, the curve has an asymptote at Sjj = 100. An Sjj value of 100 corresponds to a flat angular

distribution having uniform scattering intensity at all angles.

For a random surface finish, the angular distribution is a bell

shaped curve having its maximum in the specular direction. The

distribution generally becomes broader as the roughness increases,

but it should approach a flat distribution only as the value of Rq

becomes very large. Hence, the asymptote at Sjj = 100.

Second, the geometrical spreading of the optical beam in the gauge

is such that the value of Sjj equals 5 when the rms roughness Rq of

the surface is essentially equal to zero. This situation occurs

when the SRI is tested with smooth optical surfaces. Hence, the

function Rq(Sjg) should pass through the point (5,0).

In view of these constraints, the following formula for Rq was

chosen:

R

q

(#im) = (S N -5) 1 /2 [a + b/(100-S N )], (3)

having the parameters a and b. These were fitted to the data by a linear leas t- squares method. The resulting best-fit values for a and b, rounded to three significant figures, are

a = 0.0138 ± 0.0035 /xm,

b = 0 .257 ± 0 .066 ^m,

(4)

where the uncertainties in the fitted parameters represent

estimates of one standard deviation for each parameter.

The square-root functional model fits the data points better than

a linear model previously described [B.12] while still satisfying

the two constraints.

15
Rq

(

um

)

SRIC Implementation

Rq vs . SN

Figure 7. R

q

values measured with a stylus instrument

vs. SN values obtained for the SRI.

16
SRIC Implementation

Using the function described by Eq. 3 and shown in Figure 7, we

calculated a coefficient of determination r^ [B.13, B.14]. This

statistic is similar to the square of the correlation coefficient

and is a standard approach for expressing how well the variation

in the Rq data is accounted for by the fitted curve. For the

nonlinear model of Eq. (3), the formula for r^ is given by:

A l R

i

, R . qi qi

l R qi

(5)

where n = 25, Rqi is the A set of 25 measured Rq values, Rq is the

mean of these data, and Rqi is the set of Rq values predicted by

the fitted curve. The calculated value for r^ was 0.87,

representing a fairly good correlation between the S jq vs. Rq data

and the fitted curve, considering that the data include points

taken on four different stainless steel materials and with widely

differing surface curvatures [B.12].

Based on the deviations between the data and the model, we also

conclude that the Sjsj data from the SRI, together with the two

parameter model given by Eq. (3), are appropriate for estimating

the rms roughness of lapped stainless steel surfaces and most

likely other lapped materials as well to an uncertainty of +26

percent (1 standard deviation). This is a reasonable uncertainty

for a comparator technique given the variability of both the

stylus data and the optical data and the fact that standard values

for specifying roughness are differentiated by factors of two

[ B . 1 1 ]

.

It should be noted that the Sjj values from the optical sensor of

the SRI depend on the head geometry which is not standardized.

Several types of heads are available with different illumination

spot sizes and angular scattering ranges, shown as y' and <j> respectively in Figure 2. The sensing head used in the IWS

,

with

spot size of 1.8 mm and an angular range of ±15°, is the most

common one

17
SRIC Implementation

. .

'

... #

18
SRIC Implementation

IV . DATA STRUCTURES

1 . LOCAL DATA

In the March 1987 implementation the data required for a surface

roughness inspection of a part are stored locally in disk files on

the SRIC itself. The SRIC is sent the command to 'LOAD_DATA' to

tell it what part needs to be inspected. The LOAD_DATA command is

packaged with two ar gument s - - the part name and the name of the

inspection plan (the latter is an integer). Upon receiving this

command the SRIC prepares itself to access the proper data during

the inspection.

Once the SRIC completes the command to 'LOAD_DATA' , it waits for

the command to 'INSPECT'. After receiving the INSPECT command, it

directs the inspection of the part. As each state machine module

runs, any data required by that module are retrieved from the

local data files as they are required. It is necessary to access

the data locally during the actual inspection to obtain the

response time required.

The local data are stored in a flat file system; each relation is

stored in a separate file. A relation contains key fields that

are used to find the record required. Then, the data fields in

that record are retrieved. The full specification for all the

SRIC flat files is in Appendix D. The description of how the flat

file system is implemented is in the IWS document Implementation

of the Execution Control System of the Inspection Workstation

[A. 2] .

2 . AMRF DATA

In a future implementation the data required to inspect a part

with the SRI will reside in the AMRF IMDAS . This data will be

contained in two separate files. The first file is the part model

file. This contains the geometry and topology data for the part,

including the tolerance specifications. These data are in a neutral format, and are used by all processes throughout the AMRF.

For a complete specification of the part model, see AMRF Database

Report Format: Part Model [ B . 1 6 ] . Supplementary to the part model

data, additional data are required to inspect a part. These data

specify which points on each surface to measure as well as other

data not included in the part model file. These data are included

in the inspection data file.

19
SRIC Implementation

Upon receiving the LOAD_DATA work order, the SRI Controller "task"

module will direct the retrieval of the part model and the

inspection data file from the IMDAS . It will then parse those

files and transfer the data to the local data files described in

the previous section. The structure for these local data files

will remain the same, even when the data originates from the IMDAS

rather than from the SRIC itself (as is currently the case).

20
SRIC Implementation

V . TASK DECOMPOSITION

The state machine modules used to implement the SRI Controller are

shown in Figure 8. Listed in their order of hierarchical task

decomposition (from highest to lowest), those modules are irc_sri,

task, surfaces, points, dial, and sri. (The modules dial and sri

are at the same control level.) "Dial" contains the procedures

needed to access the ADI. Likewise, "sri" contains the procedures

necessary to control and monitor the SRI. These two modules are

directly analogous to the machine module in the CMM Controller

[A. 3].

This section lists each of the state machine modules, including

the two "machine" modules, dial and sri, and provides a general

description of each.

1 . irc_sri

The irc_sri module implements the University of Virginia (UVA)

model [B.15] for interfacing the SRI Controller to the Robot

Controller. This module accepts commands from the IRC and

decomposes those into transition commands and order actions. It

receives statuses from its subordinate, the "task" module, and

returns statuses to the IRC.

2 . task

The module, task, supervises the main functions performed by the

SRI Controller, namely, to read the dial indicator, to retrieve

the data to inspect a part (given the part name and the inspection

plan name), and to supervise the inspection. The work orders for

these functions are READ_DIAL, LOAD_DATA and INSPECT.

The READ_DIAL work order commands the SRI Controller to get the

reading of the dial indicator and to send it back to the IRC. The

command is sent down the task hierarchy through the "surfaces"

module to the "points" module, which actually carries out the

command

The LOAD_DATA work order commands the SRI Controller to prepare

itself so that it will use the proper local data files during the

subsequent part inspection. Eventually, these data will be

retrieved from the IMDAS . The data will then be parsed and stored

in the above mentioned local data files in the same format as the

data that are currently being used.

21
SRIC Implementation

Figure 8. Control Levels for

the SRI Controller

22
SRIC Implementation

When the SRI Controller receives the work order INSPECT, it begins

inspecting the first surface designated by the inspection data.

When that surface has been completed, it continues on to the next

surface until all surfaces in the inspection plan have been

completed. It then signals a status of DONE back to the IRC, and

consequently frees up the IRC to be commanded again by the

Workstation Controller (WSC).

In practice (for the current implementation), only the bottom

surface of each part (as it sits on the tray) is inspected by the

SRI. The robot must reorient the part to present a new surface to

the SRI, and that kind of manipulation has not yet been

implemented in the IWS

3 . surfaces

The purpose of the "surfaces" module is to interact with the IRC

to detect the edges of the surface to be inspected. Based on that

knowledge, the physical location of the designated origin for that

surface can be determined. Subsequently, this module sequences

through the points to be measured on that surface.

Currently, only the sequencing operation is performed; the edges

of the surface are not detected. The point on the surface that is

immediately presented to the SRI is assumed to be the origin for

that surface

4 . points

The main job for "points" is to post position requests to common

memory as called for by the SRI inspection. In addition, "points"

accesses the "dial" module procedure to read the automatic dial

indicator, and posts that reading to common memory as well. It is

up to the IRC to make use of the posted positions and dial

readings to move the part accordingly.

The first time the module, points, is called for each surface, it

is assumed that the point immediately in front of the SRI is the

origin for that surface. "Points" then specifies the offset to

the first point on the surface to be measured and waits until the

IRC has acknowledged that the robot has moved the surface to that

point.

A procedure called tweak_point (contained in the module, sri) is

then called to determine the relative angular orientation from the

current point required for the next reading. The purpose of

tweak_point is to find the orientation that gives the proper SRI

reading for each point. Once the robot moves to the requested

orientation, tweak_point is called again, and the procedure is

repeated. This is continued until the adjustment algorithm

23
SRIC Implementation

implemented in tweak_point signals the module, points, that it is

done. "Points" has then completed the measurement for the current

point and signals the surfaces module that it is DONE.

5 . dial

The "dial" module is the machine level module for the ADI. It

contains the procedures that service the ADI. The main function

accessed during a normal run is ge t_dial_r eading , which returns

the dial reading as a real number. Additionally, this module

contains several procedures that initialize the ADI as well as

divide the ge t_dial_reading into its smaller component parts.

6 . sr

The "sri" module contains the main procedures used to access the

SRI from the "points" module. The main procedure contained in

this module is tweak_point . This procedure implements the

algorithm, discussed in sec. III. 2, to determine the proper

surface orientation to measure the current point with the SRI.

Tweak_point returns two variables, status and pt. If the status

returned is WORKING, then the pt returned is the new point

orientation requested by the SRIC. This orientation is always

calculated relative to the point orientation before the

tweak_point algorithm is first called for each point. When

tweak_poirtt returns DONE, then no further reorientations are

necessary. The correct orientation has been found and the proper

SRI reading taken.

24
SRIC Implementation

VI . PROCEDURE MODULES

The procedure modules required by the SRI Controller (aside from

"dial" and "sri") are described in this section.

1 . sr i_l ib

This library module contains procedures from the HP library that

are not used by the other controllers. The particular modules

included here are used to interface the HP computer to the SRI and

the ADI using the RS232 and GPIO boards, respectively.

2 . gr aph_l ib

This module contains all of the HP graphics modules that are

required for displaying graphics on the HP monitor.

3 . display

This module contains the procedures to interface the graphics

demands of the SRI Controller to the HP graphics procedures

(contained in graph_lib). Included are procedures to plot lines

on the screen as well as to write text to specified positions on

the screen.

Eventually, all IWS Controllers will contain the modules,

graph_lib and display, and any text or graphics shown on an IWS

monitor will pass through the "display" module on the appropriate

controller

4 . sr i_types

This module includes data structure types that are specific to the

SRI Controller, and are referenced by state machine modules as

well as other procedure modules throughout the SRI Controller

program

One data structure defined here is f inish_s tat is t ics . This is the

lowest level data structure used by SRIC that is independent of

any particular SRI. It contains seven components. Five of these

are related to the optical scattering patterns detected. These

are S^, I, peak offset, peak magnitude, and peak spread. The

remaining two are computed values of roughness- -Rq , the rms

roughness, and R a , the roughness average.

25
SRIC Implementation

5 . sr i_pr ims

The sri_prims module contains all of the procedures that directly

interface the HP computer to the SRI. Since this is the one

module that needs to be modified to connect the SRIC to a different SRI, the details are discussed in Chapter 7, INTERFACE

TO EQUIPMENT.

6 . readsr

The main function provided by the "readsri" module is read_sri.

This function takes the raw SRI data retrieved by sri_prims

,

processes them, and bundles them into the f ini sh_s t a t i s t ic s data

structure described in section 4 above.

7 . ge t_da t

This module contains the procedures that search the locally stored

data files to return the data values needed by the state machine

modules as they are running.

8 . rp t_func s This module exports the data structures and functions required for

the SRIC to communicate the new part positions requested of the

IRC during the SRIC inspection.

26
SRIC Implementation

VII . INTERFACE TO EQUIPMENT

1. MODULES THAT INTERFACE TO EQUIPMENT

SRIC supervises both the SRI and the ADI. The only module that

interfaces SRIC to the SRI is sri_prims. Likewise, the only

module that interfaces SRIC to the ADI is "dial".

2. DETAILS OF THE CURRENT IMPLEMENTATION

In the sri_prims module, the following SRI functions are

performed

Initialize the SRI from a cold start, and prepare it to

receive commands from the SRIC and return SRI data to it.

Return the scattering value (S$).

Return the intensity (I).

Prepare to send the individual detector readings Ij^ - - each

one in order, upon command.

Return the value from each of the detector elements.

Additionally, this module specifies the number of elements in the

SRI detector array and the angular spacing between them. The

latter is called the pitch calibration factor in the program.

In the "dial" module, the following ADI functions are performed:

Initialize the ADI from a cold start.

Return the dial reading.

3. . CHANGES REQUIRED FOR EQUIPMENT SUBSTITUTION

In order to substitute a different SRI or different ADI, any

changes to the functions specified in Section 2 above must be

implemented in the sri-prims and "dial" modules, respectively.

27
SRIC Implementation

. ;

.

*

1

28
SRIC Implementation

VIII. INITIALIZATION AND SHUT DOWN

1 . START UP

When the SRIC program is first started, the SRI and the ADI are

both initialized and are ready to receive commands. On receiving

the WARM_STARTUP command from the IRC, variables related to the

tweaking algorithm are initialized, and the SRIC is ready to

receive work order commands.

2. SHUT DOWN

The SRIC reports back DONE when it receives the WARM_SHUTDOWN

command. Nothing else is done. It can be warm started if it

receives a new WARM_STARTUP command.

3 . ABORT

The ABORT command

command is not imp

ire sri to the nex

is used for error handling,

lemented. When the command

t level, task, it is ignored

Currently, th

is passed down

i sfrom

29
SRIC Implementation

JOftfl Jtf; JLJ a -

_ J i 7
SRIC Implementation

IX. ERROR HANDLING

Currently, any error crashes the SRI Controller program, and the

IWS must be restarted. Three types of errors have been observed

with the SRI. We classify them as intensity errors, software

errors, and detector errors.

1. INTENSITY ERROR

1.1. Description

The intensity error takes place when the total signal into the

detector array becomes so large that the intensity value cannot be

properly displayed on the SRI electronics. This error condition

can occur when a highly polished, highly reflecting surface is

measured by the SRI, and the condition immediately goes away when

the signal decreases back to a measurable value. The error

condition is displayed as a "UEL" on the SRI electronics display

unit

1.2. How Handled

At present this error condition can only be alleviated by manual

reinitialization of the SRI electronics unit. Subsequently, the

whole IWS must be restarted.

2. SOFTWARE ERROR

2.1. Description

The software error condition is displayed as "FFF" on the SRI

electronics unit. This is a general condition to describe any one

of a number of different error conditions sensed in the SRI

operation, the key one likely being a breakdown in communications

with the SRIC via the RS-232 interface.

2 . 2 How Handled

At present this error condition can only be alleviated by manual

reinitialization of the SRI electronics unit. Subsequently, the

whole IWS must be restarted.

31
SRIC Implementation

3. DETECTOR ERROR

3.1. Description

The detector error is indicated as "F80." It usually indicates a change in the zero background calibration of the detectors.

3.2. Hov Handled

Recovering from an F80 requires at least a manual recalibration of

the dark current null values in the detector array but may also

require replacement of a fuse or a battery in the SRI electronics.

Subsequently, the whole IWS must be restarted.

32
SRIC Implementation

X. USER INTERFACE

1. STAND-ALONE OPERATION

In integrated mode, irc_sri is the highest level module in the SRI

Controller. It receives commands, via the local network, from the

Robot Controller. If the SRIC is to be run in stand-alone mode,

the operator needs to enter commands directly to the SRI

Controller and have those commands transferred to the irc_sri

module. The interface that provides this connection between the

user and the irc_sri module is the "sritest" module. "Sritest"

simulates the Robot Controller, and allows the user to select

commands for the SRI Controller.

2. USER COMMANDS

The commands available to the user are ABORT, SHUTDOWN, STARTUP,

and EXECUTE. These are the transition commands. The first three

commands do not have arguments. The arguments for the EXECUTE are

the work orders and their respective arguments.

After turning on the equipment, the user must first choose STARTUP

to bring the SRI Controller into the ready state. Next, the user

selects EXECUTE and may select any of the three work orders: Get

Dial Reading, Load Part, or Inspect. For each part, Load Part

must be chosen before Inspect to select the data to inspect a particular part before the actual inspection may begin.

After a part has been inspected, data for a new part may be loaded

and inspected, or else the SRI Controller may be shut down by

issuing the transition command SHUTDOWN.

33
SRIC Implementation

'

'
SRIC Implementation

XI . FUTURE PLANS

The development of the SRI is still in progress. Much research

still needs to be done to take advantage of all of its

capabilities as a roughness sensor. Operational improvements

should also be made as well. We discuss each of these two areas

in the following subsections.

1. OPERATIONS

The automatic alignment procedure has been completed for flat or

nearly flat surfaces. The alignment algorithm may be easily

extended to convex surfaces, such as those produced by turning,

and to surfaces that are slightly concave. For inspection of

cylindrical bores, a different type of SRI head, presently

available commercially, would need to be installed at the IWS in

addition to the one presently used for flat surfaces.

The error recovery part of the SRI operation also needs to be

automated. This will require hardware and software changes to

allow external control of the SRI initialization by the HP

Controller

2. ROUGHNESS SENSING

Section III. 3 discusses the first comparator study of optical

roughness measurement performed for the AMRF . Studies on other

types of materials and other finishing processes will be performed

as part of the ongoing automated manufacturing research program at

NBS . This research will enable us to develop mathematical curves

such as that shown in Figure 7 for each type of finishing process.

As these studies are completed, a database will be accumulating

for estimating rms roughness Rq , and perhaps roughness average R a as well, for different machining processes. We also plan to

include in the database knowledge of the correlations between

surface roughness and product functions.

One limitation, that is apparent from our initial study on handlapped surfaces, is depicted in Figure 7. The range of the SRI

for these types of parts is limited to about 0.3 jum Rq , that is,

to fine lapped surfaces and probably fine ground ones as well.

Therefore, rough ground surfaces are probably out of the range of

the SRI. However, the range limitation depends on the wavelength

of the radiation, fixed at 800 nm , and on the spacings of the

surface irregularities. For roughly machined parts, such as those

produced by facing, turning, or milling, the irregularities from

the machining processes are much more widely spaced than those

produced by grinding or lapping. This circumstance will tend to

increase the range of measurable roughness for those rough

35
SRIC Implementation

machined components. Therefore, one of the principal results of

the AMRF surface scattering research will be to determine the

range of measurable roughnesses for various types of machining

processes

36
SRIC Implementation

XII . ACKNOWLEDGEMENTS

The authors are grateful to B. Borchardt, R. Veale, S. Osella, and

J. Zimmerman for their contributions to the SRI project and for

valuable discussions during the writing of this report. The work

was primarily supported by the U.S. Naval Air and Sea Systems

Commands. Related research on optical scattering from rough

surfaces was partially supported by NASA Langley Research Center.

37
SRIC Implementation
SRIC Implementation

APPENDICES

A. IWS DOCUMENTATION LIST

1. H. T. Moncarz , Architecture and Principles of the

Inspection Workstation . NBSIR 88-3802, June 9, 1988.

2. H. T. Moncarz, Implementation of the Execution Control

System of the Inspection Workstation . NBSIR 88-3787,

May 19, 1988.

3. H. T. Moncarz, T. H. Hopp , P. Lezark Implementation of

the CMM Controller , to be published as an NBSIR, 1988.

4. H. T. Moncarz and T. V. Vorburger, Implementation of

the SRI Controller . NBSIR 88-3794, June 2, 1988.

5. H. T. Moncarz and B. Borchardt, Implementation of the

Inspection Robot Controller . NBSIR 88-3772, April 21,

1988.

6. S. A. Osella, Implementation of the Workstation

Controller . NBSIR 88-3819, July 13, 1988.

7. J. Zimmerman, Inventory of Equipment in the Inspection

Works tat ion . NBSIR 88-3775, May 5, 1988.

8. H. T. Moncarz, S. A. Osella, B. Borchardt, and R.

Veale, Operations Manual for the Inspection

Works tat ion . NBSIR 88-3766, April 21, 1988.

9. J. Zimmerman, Recommended Technical Specifications for

Procurement of Commercially Available Systems for the

Inspection Workstation . NBSIR 88-3779, 1988.

39
SRIC Implementation

'

'
SRIC Implementation

B. REFERENCES

1. R. Brodmann, 0. Gerstorfer and G. Thurn, "Optical

Roughness Measuring Instrument for F ine - Mach ine

Surfaces," Opt. Eng. 24 . 408, 1985.

2. P. Beckmann and A. Spizzichino, The Scattering of

Electromagnetic Waves from Rough Surfaces . Pergamon,

Oxford , 1963.

3. J. M. Elson and J. M. Bennett, "Relation between the

Angular Dependence of Scattering and the Statistical

Properties of Optical Surfaces," J. Opt. Soc. Am. 6 9 . 31, 1979.

4. E. L. Church and J. M. Zavada, "Residual Surface

Roughness of Diamond- Turned Optics." Appl. Opt. 1

. 1788,1975.

5. J. C. Stover, "Roughness Characterization of Smooth

Machined Surfaces by Light Scattering." Appl. Opt. 1

. 1796, 1975.

6. E. C. Teague, T. V. Vorburger and D. M. Maystre,

"Light Scattering from Manufactured Surfaces," CIRP

Annals .30., 563, 1981.

7. T. V. Vorburger, E. C. Teague, F. E. Scire, M. J.

McLay, and D. E. Gilsinn, "Surface Roughness Studies

with DALLAS -Detector Array for Laser Light Angular

Scattering," J. Res. NBS 89_ , 3 , 19 84.

8. D. E. Gilsinn, T. V. Vorburger, E. C. Teague, M. J.

McLay, C. Giauque, and F. E. Scire, "Surface Roughness

Metrology by Angular Distributions of Scattered

Light," in Measurement and Effects of Surface Defects

and Quality of Polish . SPIE Vol. 525, 1985, pp 2-15.

9. T. V. Vorburger, D.’E. Gilsinn, F. E. Scire, M. J.

McLay, C. H. W. Giauque, and E. C. Teague, "Optical

Measurement of the Roughness of Sinusoidal Surfaces,"

Wear 109 . 15-27 , 1986

10. D. Gilsinn, T. Vorburger, L. X. Cao, C. Giauque, F.

Scire, and E. C. Teague, "Optical Roughness

Measurement of Industrial Surfaces," in Optical

Techniques for Industrial Inspection . SPIE Vol. 665 , 1986 , pp . 8-16

41
SRIC Implementation

11. ASME/ANSI B46. 1-1985 . Surface Texture ( Surface

Roughness. Waviness and Lav ) . American Society of

Mechanical Engineers, New York.

12. T. V. Vorburger, D. E. Gilsinn, E. C. Teague, C. H. W.

Giauque, F. E. Scire, and L. X. Cao, The Wind Tunnel

Model Surface Gauge for Measuring Roughness . NBSIR 87-

3586, U.S. Dept, of Commerce, Gaithersburg, Md. 1987.

13. D. V. Huntsberger and P. Billingsley, Elements of

Statistical Inference . Third Ed. , Allyn and Bacon,

Boston, 1973, p. 227.

14. N. R. Draper and H. Smith, Applied Regression

Analvs is . John Wiley and Sons, New York, 1960.

15. D. R. O'Halloran and P. F. Reynolds, Jr. , "A Model for

AMRF Initialization, Restart, Reconfiguration and

Shutdown" , to be published as an NBSIR, U.S. Dept, of

Commerce, Gaithersburg, Md.

16. T. H. Hopp , AMRF Database Report Format: Part Model . NBSIR 87-3672, U.S. Dept, of Commerce, Gaithersburg,

Md. 1987.

17. D. Libes and E. Barkmeyer, "The Integrated

Manufacturing Data Administration System (IMDAS)--an

Overview", International Journal of Computer

Integrated Manufacturing, Vol. 1, No. 1, pp . 44-49.

18. C. Furlani, et al, "The Integrated Manufacturing Data

Administration System (IMDAS)", to be published as an

NBSIR, 1988.

19. K. Murphy, P. Tanguy, R. Norcross, and F. Proctor,

Cleaning and Deburring Workstation Operations Manual . NBSIR 88-3804, June 9, 1988.

42
SRIC Implementation

C. GLOSSARY (and abbreviations)

ADI Abbreviation for the Automatic Dial Indicator.

Automatic Dial Indicator

Instrument used to measure the distance that a spring

mounted stem is depressed.

controller

Supervises the operation of a mechanism, another controller, or both.

ECS Abbreviation for the execution control system.

Execution Control System

Computer program that runs on each controller computer and

implements the AMRF design principles. This program loads

and executes those modules which determine which controller

is actually being run.

IMDAS Integrated Manufacturing Data Administration System [B.17,

B . 1 8 ]

. Inspection Workstation

AMRF workstation that inspects parts for dimensional

tolerance and surface finish.

IWS Abbreviation for the Inspection Workstation.

logical architecture

Specifies the direction of commands and statuses between

controllers and between controllers and equipment.

physical architecture

Specifies the physical connections among the controllers

and equipment.

ready state

The state in which a controller is ready to accept work

order commands. This is the normal state of the controller

during its operation.

SRI Abbreviation for the Surface Roughness Instrument.

SRIC Abbreviation for the SRI Controller.

Surface Roughness Instrument

Machine that measures the optical scattering from the

surface of a part. The scattering can be correlated with

its surface roughness.

43
SRIC Implementation

state machine

Software control unit with outputs dependent on inputs to

it plus its internal state. This is the building block for

the IWS control software.

transition commands

Commands used to transfer the IWS to a new state (specified

by the UVA model).

UVA Protocol

Model, proposed by research group from the University of

Virginia and adopted by the AMRF , that specifies the start

up and shut down sequence for the AMRF as a whole as well

as every controller within the AMRF [ B . 1 5 ]

work element

The part of the work order command that specifies what main

controller function to perform.

work order commands

A command accepted by a controller when it is in ready

state. A work order command contains an action (i.e.

execute, plan, cancel, or stop), a work element, parameters

associated with the work element, an identification number,

and an update number.

WSC Abbreviation for the Workstation Controller.

44
SRIC Implementation

D. FLAT FILE SPECIFICATIONS

This appendix contains the specifications for the flat files used

by the SRI Controller and contained in local disk files. For

details concerning the implementation of the flat file system, see

the IWS document IMPLEMENTATION OF THE EXECUTION CONTROL SYSTEM OF

THE INSPECTION WORKSTATION [A. 2]. For a general description of

what the flat files are used for, see Chapter IV, Section 2.

Each flat file is composed of ASCII characters that are broken up

into records -- each record containing one or more key fields and

one or more data fields. Records are separated by a carriage

return and a line feed. Fields are separated by one or more

spaces . Four types of flat files (also referred to as relations) are used

for the SRI. The tabular information below describes each of

these

This information is presented in the following manner. The

specification for each relation begins with the name of the

relation. The name given here is the same as given in the

computer program, except that in the computer program the name is

prefixed by 'DS_'.

A brief description of the relation is specified next.

This is followed by the name of an example flat file that is

actually used. The examples referenced here contain data to

inspect the pipe clamp, one of the parts commonly manufactured at

the AMRF

The task module from which this relation is retrieved is specified

next

Following that are the descriptions of the key fields and data

fields which contain the data actually found in the flat files.

The key fields are used to find the particular record in the

relation that is required. The names of these fields often

include the underscore character, so that a name will clearly

specify a single field, even if it has more than one word.

However, these names are not necessarily the same as they appear

in the computer program.

Additionally, the data types for the key fields are indicated

after the name (or names) by '

: ' and then the identification of

the type. Many of the fields are of type integer. Comments are

also included in some cases below to elaborate on what the fields

mean. These are distinguished by enclosing them between braces,

' {

' and ' }

'

45
SRIC Implementation

Following the names for the key fields are the names for the data

fields. The names are specified in the same manner as those for

the key fields. Data types and, in some cases, comments are added

here as we 1 1

1.

Inspection_Plan

Description

Given the inspection plan, return relevant inspection data.

Example file name: plan_clp

Retrieved from: task

Key field:

Inspect ion_Plan_Name : integer

Data fields:

Units : character {measurement units for data -- 'I'

for inches or 'M' for mm)

Surf_Plan : integer {specifies which surfaces to measure}

Num_Of_Surfs : integer

{total number of surfaces in Surf Plan}

2 . Surfs

Description

Given the Surf_Name (from the Inspection Plan) and an

index, get the next surface to inspect.

Example file name: sfs_clp

Retrieved from: task

Key field:

Surf_Plan, Surf_Index : integer

Data field:

Surface_Name : integer

3 . Surf_Chars

Description

Specifies the position coordinates to be measured for a

particular surface.

Example file name: surf_clp

46
SRIC Implementation

Retrieved from: surfaces

Key fields

Sur f ace_Name : integer

Data fields:

X_Org , Y_Org : real

{surface origin--in relation to initial location}

NumOfSurfPts : integer

{number of points to measure on current surface)

4. Point

Description

Specifies the next point to be inspected relative to the

origin specified in Surf_Chars . The components of the

point are in SRI coordinates.

Example file name: pt_clp

Retrieved from: points

Key fields

Surface Name

,

Pr ob ing_P t_Nbr : integer

Data fields:

X, Y : real {Two components of point on current surface

To the SRI, these two components are x, y.

To the robot, the two components are z, y.

47
SRIC Implementation

'

.

‘

48
READER COMMENT FORM

IMPLEMENTATION OF THE SRI CONTROLLER

This document is one in a series of publications which document

research done at the National Bureau of Standards' Automated

Manufacturing Research Facility from 1981 through March, 1987.

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BIBLIOGRAPHIC DATA

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1. PUBLICATION OR

REPORT NO.

NISTIR 88-3794

2. Performing Organ. Report No. 3. Publication Date

JUNE 1988

4. TITLE AND SUBTITLE

"Implementation of the Surface Roughness Instrument Controller'«

5. author(S) Howard T. Moncarz and Theodore V. Vorburger

6. PERFORMING ORGANIZATION (If joint or other than NBS, see instructions)

NATIONAL BUREAU OF STANDARDS

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10.

SUPPLEMENTARY NOTES

I | Document describes a computer program; SF-I8S, FIPS Software Summary, is attached.

11.

ABSTRACT (A 200~word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here)

This document describes the theory and implementation of the Surface Roughness

Instrument Controller (SRIC) program. This controller is part of the Inspection

Workstation (IWS) in the Automated Manufacturing Research Facility (AMRF) in the

Center for Manufacturing Engineering at the National Bureau of Standards. The SRIC

supervises the surface roughness inspection of a part. The inspection is data

driven.

The SRIC controls two pieces of equipment — the surface roughness instrument (SRI)

and the automatic dial indicator (ADI). The SRI monitors surface roughness by

measuring the angular distribution of light scattered from the surface of a part.

It does its job in coordination with the IWS robot. Using the SRI optical signals

as sensory input , the robot properly aligns the part in front of the SRI so that

a valid optical scattering reading is obtained. (The ADI is used to help the robot

position the part in front of the SRI for its initial reading.) The SRIC uses

the optical data obtained to compute an rms value for roughness and a roughness

average

12.

KEY WORDS (S/x to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolon s) AMRF; data-driven control; dial indicator; inspection workstation; IWS; SRI;

surface roughness

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