a distributed microprocessor control system for an industrial robot

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Open Dissertations and Theses

Open Dissertations and Theses

McMaster University Year

A Distributed Microprocessor Control

System for an Industrial Robot

Raad F. Refauli

This paper is p osted at DigitalCommons@McMaster.

http://digitalcommons.mcmaster.ca/opendissertations/2885


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A DISTRIBUTED MICROPROCESSOR CONTROLSYSTEM FOR AN INDUSTRIAL ROBOT

by Raad F. Rafauli . B. Eng.A Thesis

Submitted to the School of Gr?duate Studies,in Par t ia l Fulfilm ent of the Requirements

for the Degree...

Master of Engineering

McMaster Universi tyJune 198:1


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MASTER OF ENGINEERING (.1981)Electrical and Computer Engineering

, ,

McMASTER UNIVERSITYHamilton, Ontario

TITLE:

AUTHOR:

A Distributed Microprocessor Control System for anIndustrial Robot

Raad F. ~ f a u l i , B.Eng. (McMaster University)

SUPERVISORS: Dr. N. K. Sinha, Department of Electrical and ComputerEnginee:ringDr. J. TlustYt Department of Mechanical EngineeringNUMBER OF PAGES: ix, 81, Appendices A-D (60), References (2)

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ABSTRACT

Complex automation systems, such as industr ia l robots, require.a computer-based control system for the effective u t i l i z a t i o ~ of theadvanced technology.

A s t a t e ~ o f - t h e - a r t was studied an d presented in this thesis.A distributed computer control system for a modified Unimate

2000 robot, is presented. The l 6 - b i ~ Intel 8086 microprocessor wasused as the master computer, and th e 8-bit Intel 8748 micrgprocessor as

,th e slave processor.The system is effective and the experimental results agree

with the simulation.

..

i i i


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TABLE OF CONTENTS

CHAPTER 1 - THE I N D U S T R ~ ROBOT1 .1 Introduction1.2 Major Coordinate System

, Page

11

1. 2.11. 2. 21. 2. 31.2.4

Cartesian Work EnvelopeCylindrical Work Envelope\Spherical Work EnvelopeArticulated Work Envelope

3333

1.3 Power Sources "1.4 The Control

1.4.1 Non-Servo Controlled1.4.2 Servo Controlled1.4.3 Manipulator Path

1.5 Command Generation

..

444457

Programming th e Robot1.6

1.5.11. 5. 21. 5. 31.5.4

1. 6.11. 6. 21.6.3

Cartesian InterpolationJo ih t Interpo la tionC ~ b i c Spline InterpOlationConstant Acceleration,Constant V e l o ~ i t y Algorithm

On-Line ProgrammingOff-Line ProgrammingProgramming Languages

v

88

1122222327


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C R A P T E ~ 2 THE CONTROL SXSTEMP 2.1 Introduction2.2 System Architecture2.3 ,Detailed System Functional Description

Page

3032~

\

2.3.1 The Master Cpmputer2.3.2 The Slave Processors2.3.3 The Manual Controller2.3.4 The Interlock Signals2.3.5 The Mechanical Range Limltations andthe Safety Features

2.4 Position Control System

353536373738

3.6.13.6.23.6.33.6.4

( 3.6.53.6.63.6.73.6.8

,

CHAPTER 3 - HARDWARE-CONSIDERAT!ON3 ~ The West-Amp Servo Amplifier3.2 The Elect ro Craft Servo Amplifier3.3 The Electro Craft Servo Motors3.4 The Position Feedback Transducer3.5 The Master Computera.6 The Servo Cards

.Control Board SelectDigital Data, InputDigital Data Output andTransfer AcknowledgeSynchronizationsAnalog Signal GenerationsSystem Protection andManual/Computer SelectThe Positional FeedbackThe Central Processor Unit (CPU)

vi

4343444545464950515355575860


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CHAPTER 3 (continued)3.7 The Manual Controller

CHAPTER 4 - SOFTWARE CONSIDERATIONCHAPTER,5 - CONCLUSION

.APPENDIX A- PLM/86 PROGRAM LISTINGAPPENDIX B - ASM48 PR9GRAM LISTINGAPPENDIX C - SCHEMATIC DIAGRAMS

APPENDIX D- iSBC86!l2A MON;TOR COMMANDS

REFERENCES

v ii

Page

62

69

80


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Figure1.11.21.31.41.5

1.6

1.7

' 1 .8

1.9

1.102.12.2

,2.32.42.5-2.62.73.1

LIST OF FIGURES

Major Robot Coordinate SystemsManipulator Path Con trolQuadratic Interpolation of Joint Posit ionSingle-Axis Point-to-Point Motion Using A SingleCubic Spline F ~ n c t i o nSingle-Axis Point-to-Point Motion Using CubicSpline.FunctionsJSingle-Axis P o ~ t - T o - P o i n t Motion Using A SingleTrapezoidal V ~ l o c i t y ProfileSingle-Axis Point-to-Point Motion Using ATriangular. Velocity' Prof i leVelocity Profi le for Three Joints MotionS ingl e-Ax is Path Con trol Motion Using ATrapezoidal . V e r o ~ i t y ProfileConstant Velocity f o Off-Line ProgrammingThe Five Axes of Motion of the Unimate 2000 RobotThe Distributed Microprocessor Control S y s t e ~Closed-Loop Servo SystemComputer Within the Posi t ional L90PPhotograph of the Velocity Prof i leApproximate Model for One-Joint of the RobotThe Root-Locus for the Positional Servo SystemCommon Bus Configuration

v i i i

Page26

10

15

16

19

1920

21273034

4040404247


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Figure

3.23.33.43.53.63.73.-83.93.10'3.113.123.133.143.153.164.14.2

4.3

) .

Control Board Enable Signal GenerationFunctional Block Diagram of the Servo CardControl Board Select Signal GenerationDigital Data InputDigital Data Output and Transfer AcknowledgeSynchronizing Signals2-Byte Parallel Loading of the DACDigital to Analog Converter , Bipolar OperationComputer/Manual Select and System ProtectionThe Positional FeedbackThe CPU Interface on the Servo C ~ Velocity, Acceleration ControlCommand Velocity GenerationGenerated Command ControllerMiscellaneous Functions GenerationSystem's Software OrganizationPlot of the For tran Simulation fo r one Jointof the RobotControl Program Flowchart

ix

Page

4848495052545656575960636365677074

76

.'


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CHAPTER 1

THE INDUSTRIAL ROBOT

1.1 IntroductionAll industr ial r o ~ o t s i n c l u ~ t hr ee bas ic elements: an art ic-

ulated arm, controls and power source. The arm moves in up to sixd i f f e r e n ~ axes. Three are provided by the arm i t sel f which may rotatein an arc around i ts base and reaches up d o vert ical ly and in andout horizontally. As many as t hr ee o th er motions are added a t the wristwhich allows the hand or gri ppe r a tt ached to i t to rotate, and movein vert ical and horizontal p lanes .

These art iculat ions enable the arm to move to some predeter-mined point in space, work on an object, and then return to the orig-inal position or to a sequence of other points in s p ~ e .

The pattern of movements d e p e ~ d s on the need of the job andthe programming capacity of the controls.

\ /,J /1.2 The Major Coordinate Systems for Industrial Robots

The point in space accessible to a robot depends on i t s de-signed work ~ n v e l o p e . There are four basic design categories:Cartesian, cylindrical , spherical, and art iculated, that carve ou tsl ight ly different geometric work areas in space, as shown in Figure1.1.

1


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2

I '.,

D) ARTICULATED I(3 Ro ta ry Co-o1::ds.)

CAR.TESW(3 Translative Coords.)

B) CYLINDRICAL(1 Rotary.

2 Trans.)

}tOUR MAJOR ROBOTCOORDINATE SYSTEMS

C) SPHERICAL(2 Rotary.1 Trans.)

Figut. 1.1 ~ j o r Robot Coordinatb S 1 ' t ~

t


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1.2.1 The Cartesian work. envelope is created when the horizontal

3

dimensional rectangle.

robot arm is attached to a vert ical column and m o v ~ s uR and down andin and out in relation to this column. The column i t se l f is mountedon a third l inear axis which moves in two directions. These threem&vements combine to g e n ~ r a t e a work e ~ v e l o p e in the shape of a three-

\\

1.2.2 The cylindrical work envelope is created when the horizontalarm is a t ~ a c h e d to a vert ical carriage and moves up and down and in- '"', .and out in relation to this carriage. The carriage i t se l f is mountedon a pedesthl which rotates. These three movements combine to generatea work ehvelope that i s a portion of a cylin

1.2.3 In a 8 p h e r i ~ a l work envelope, the robot is mounted on a ~ b a s esomewhere near i ts midpOint so that i t can t i l t up and down and in andaround i t s support point .combine to generate a work

,The arm extends horizontally.envelope that is a portion of

These motionsa sphere.

1.2.4 In an a r t i c ~ a t e d work envelope, the arm is attached to ap e d e s t a l . t h ~ t rotates. The arm i t se l f is jointed, adding a kind ofelbow movement ',to the art iculations. Thus, as the arm rotates andreaches in the Worizontal and v e r t i ~ a l planes, i t generates a portionof a sphere in space and as the elbow bends, i t enables the robot armto come in ~ l o s e to the base. The jointed act ion enlarges the workarea accessible to ' the robot.


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1.3 Power SourcesPower is de live re d to robots by h y ~ r a u l i c , pneumatic, or

electic motors. Most robot makers have gone the hydraulic route,which is e s p e c ~ a l l y good where heavy loads are involved. Electricmotors have the advantage of being less noisy, cleaner, more accurate,and may be less expens ive . Pneumat ical ly act ivated robots take advantage of the c o ~ r e s s e d a i r supply that is commonly available.

1.4 The ControlsnWhen classi f ied according to the type control ,robots fa l l into,

two general categories:

1.4.1 The non-servo are iess flexible than the servo control led,but are also less expensive and very accurate. In this type of robot,each jo in t moves between two end points that are determined by mechanical stops. When hydraulic or pneumatic power i s delivered to thejo in ts , the motors drive the jo in t u nti l i t reaches a mechanical stop.A l imit switch then signals the power off unti l ~ h program cal ls foranother move. The valves then open and again d eliv er f lu id to thejoints . /

In t he se robots , c ~ n t r o l l e d accelerat ion and decelerat ion1require special designs. The number of different posi t ions to which

the robot can go in sequence i s l imited.

1.4.2 The servo control led robots can do many things the simpler


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ones can' t . They can be programmed to do a more complex sequence oftasks and can have controlled velocity , acceleration, and deceler-ation. A servo c ~ t r o l l e d robot has encoders, potentiometers, re

l ~ solvers or other feedback devices a t each of the joints . These devicesfeed posi tion s ignal s back to the controller which compares them withthe commanded posit ion. The controller then sends correction s i g n a l ~to the hydraulic or electric motors at the joint . This thesis willcon side r t he servo controlled robot s only.

5

1 .4 . 3 Manipulator PathConsider a manipulator consi st ing o f an arm, the end ~ ~ h i C h

is i t s wrist , and an end-effector, which may be a hand or a tool. Theend-effector, is usually attached direct ly to the wrist . The three-dimensional path of the end-ef fector o f a manipulator is described bytwo variables. [ l J

1) End-effector position: The position of a po int fix edv

in the end-effector in & reference cartesian coordinatesystem.

2) End-effector orientation: The orientation of a cartesiancoordinate system attached to the h thatthe system's origin coincides with the end-e ec to r pos i-tion. .The above definit ion of end-effec tor posi tion ~ n orientation

)

is based on attaching a cartesian reference frame to the end-effector.The word "state" is used to represent both position and orientation of


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-an end-effector .

There are two common ways to control an indust r ia l rob ot w ithposit ion servo.

(a) For material handling jobs, a point-to-point controlis suff icient where the joints may s t a r t moving a t thesame time but don' t a l l necessari ly finish moving a tthe same time under program control . When this ~ thecase, the end-effector assumes various sta tes as i t movebetween the two end points and the shape of the path isnot predictable. Figure 1.2a shows th re e tra in ed end-effector posit ions, A through C, in three dimensions andi l lus t ra tes the path t ravelled by the end-effectotbetween these pos itio ns . P oin t- to -p oin t movements arefas t and the shape of the path is irrelevant. , ,but thes ta r t and end points are important.

ADI \I \,

(4 ) Point-Co-point (b ) I n t ~ r p o l a c e d Scraight- (c ) Incerpolated Straight-Segment Path Segment Pach with SmoothTransit ions DetveenSegments

Figure L 2 . Pach Cont:


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a distributed microprocessor control system for an industrial robot

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