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208

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209

INDEX

3D vision sensing 12-21 advantages 12 direct measurements. see Direct range measurement feature extraction techniques in. see Feature extraction techniques image processing in. see Image processing indirect measurements. see Indirect range measurement seam recognition in. see Seam recognition taxonomy 13, 14

A

Acousto-optic deflectors 16, 135 Adaptive Realtime Intelligent Seam Tracker. see ARTIST Allowable tracking error 164 AND operation 33 Artificial Intelligence (AI) 6,27,201 ARTIST

concurrent operations in seam tracking critical period 154 synchronization 152-54

control-cycle period 146, 147-8 estimate 147-8 refming estimate 147-8

hierarchical control structure 131, 140 high-level controller 131 initial path tracking 147 initial system calibration 144 laser range sensor 7 low-level controller 131 range image processing module (RPM) 132, 144 robot

collision detector 137 communication with SCM 138, 142 controller. see under PUMA robot

integration with seam tracker 137 PUMA series 560 l37 see also PUMA robot

robot control module (RCM) l32, l37, 144 robot manipulator 7 seam tracking sequence 144,148-50 shutdown procedures 150 supervisory control module (SCM) l32, l37, 138, 139 system architecture 131, l32, 139 system control software 139 system initialization 141, 144, 145 system operation 144-51 termination of seam tracking 150 torch-sensor assembly 7

ARTIST (seam tracker) 7 ASEA Robotics

adaptive torch positioner 190-2 LaserTrak seam tracker 193-5

Automatix, Inc. 184 Automatix, Inc., vision aided robotic welder 184-7

B

Bad data suppression 36, 92-3 Bad data suppression, heuristics 36 Base coordinate frame 59, 145 Bottom-up seam recognition 39, 186

contour feature recognition 48, 56 contour preprocessing 48-9 contour shape representation 48, 49-55

C

Camera calibration projector camera range sensor 74-5 scanning beam range sensor 66

CCD arrays l36 blooming 34 exposure control 34,35, 139

211

certainty factor 41,42,43 Chesapeake laser systems 66 Chirps (time of flight range systems) 19 CIM 1 CIM, strategy 1 Computer Integrated Manufacturing (CIM) 1 ClWD, abbreviation for Contact tip to work distance 9 cur_scan_cntxt 41,43

D

Data acquisition, range image 89 Deburring, robotic 2 Direct range measurement

time of flight systems. see Time of flight systems triangulation based systems

baseline 15 cameras for stereo vision 15 design tradeoffs 15 field of view 15 measurement accuracy 15 shadow region 15 stereo vision. see Stereo vision systems stereo vision, problems 15 structured light. see Structured light systems

using time of flight 14 using triangulation 14

Direct range measurement 14-18 Discrete model of seam 109 Drive transfonnation 86, 102, 148

Epipolar line 14

E

plane 14, 16,68 EPROMs 145 Error analysis 201 see also Realtime seam tracking ESPRIT 195

212

ESPRIT project on realtime imaging for arc welding 195-6

F

FCAW 11 Feature

geometric properties 36 photometric 37 points 36 relationships 37 size 36,37 surfaces 36,51 surfaces, modeling 51-5

Feature extraction algorithm for vee-grooves 44-7 iterative averaging algorithm 46-7 techniques for welding seam images 32

Feature points detection 36 in vee-joint

coordinates (world space) 99,100-2 defmition 88 error due to range resolution 159

refming coordinates 55 Filter

camera neutral density 15 optical interference filter 92, 186, 195 selective spectrum 16 see also Optical interference filter

gaussian 32 lowpass 47 median 32 smoothing 92 weighted 32

Flux-core arc welding (FCA W) 11

G

Gap filling operation 41,42,43

213

Gas-metal arc welding (GMA W) 11,23 Gas-tungsten arc (GTA) welding 23 Geometric model of seam. see under Seam geometry GMAW 11,23 GTA 23

H

Heat resistant brushes 23 High-level controller 131 Horn concentrator (ultrasonic ranging) 184

I

Image processing AND operation in 33 gaussian filter 32 histogram equalization 32 image segmentation 44 intensity thresholding 33 logarithmic transformation 32 median filter 32 of laser stripe images

least mean square slope detection filter 50 of vee-joint range images 88-102 of vee-joint range images, algorithms 90 spatial filtering 33

Image space 31,44,87 Indirect range measurement

from shadows 20 suitability to realtime applications 19 through focussing 20 using known object geometry 20 using moire fringe patterns 21

Indirect range measurement 19-21 Initial path tracking 147 Intelligent realtime control (IRTC) 27 Intensity image

error in image coordinates 31, 34

214

in measurements 31 intensity profile approximation 33 intensity thresholding in 33 of laser stripes 32, 33 preprocessing 32-4 spatial filtering in 33

Intensity thresholding 33 Interpolating seam coordinate frames 112 Interpretation coordinate frame 86, 93 IRTC 27

K

Krautkramer 3-20 air coupled transducer (ultrasonic ranging) 181 Krautkramer LAM 80/8 sound distance meter 181

L

Lambertian reflectance 17 Laser

gallium arsenide (GaAs) 135 He-Ne 186, 192

Laser proflling gage (LPG) acousto-optic deflector 135 calibration 154-5 ceo 67,82 description 135 exposure control 135 features 133-4 microcomputer-to-VMEbus interface 136 operating parameters 139 operation 141 ppv 67,81,82,83,135,136 range computation 81-4

Laser profiling gage (LPG) 66,81,82, 132 Laser tracking system

for robot endeffector control 91, 178, 179 Laser triangulation 14, 134 Least mean square slope detection filter 50 Least squares polynomial approximation 106, 127-30

215

Light cone calibration (projector camera range sensor) 77-9 steerable 185

Light plane calibration (projector camera range sensor) 75-6 Low-level control

input to robot controller 123-4 pathpoint coordinates 123-4 requirements 114 sensor rotation about torch-axis 120-23 torch positioning on seam

computing orientation 117 computing position 116 during initial path 115 during seam tracking 116-20

two step ahead prediction 120-22 Lowpass filter 47

M

Miller Electric, Deltaweld 450 (welding controller) 144 Miller Electric, S54A (wire feeder) 144 Minimum radius of curvature 161-7 Moire fringe patterns 21

N

Neutral density filter 15

o OAVtripe 41 Optical interference filter 92, 186, 195 Optics, thin lens 19,20

p

PASS (vision sensing system) 187-89 Pattern recognition algorithm 5, 23 Petrinet 151, 152 see also Timed petrinet Programmable Adaptive Sensor System (PASS) 187-89

216

Projector-camera range sensor camera calibration 74-5 camera matrix, coefficients 74 light cone calibration 77-9 light plane calibration 75~ sensor calibration 70-4 sensor matrix 71 sensor matrix, coefficients 73-4

PUMA series 560 robot controller

and auxiliary equipment 137 communication with SCM 138 external alter mode 137 external input signals (WX) 137 external output signals (OX) 137 system terminal 138

PUMA series 560 robot 137

R

RAIL (robot and vision language) 186 Range image

acquisition 89 bad data suppression 36 defmition, scanning beam range sensor 87 error

due to multiple reflections 36 missing data 35

nonsegmentable 45 of dark surlaces 34 of specular surfaces 34 preprocessing 3~ segmentable 44, 45 segmented 44, 93 transformed into Interpretation frame 91,93-8

Range image processing 88-102 Range image processing module (RPM). see under ARTIST Range sensor

and viewing 3D seams 36

217

laser profiling gage. see Laser profiling gage projector-camera. see Projector camera range sensor scanning beam. see Scanning beam range sensor view angle 36, 168--69 view vector 198

Realtime seam tracking accounting for sensor motion 100-2 coordinate frames

Base frame. see Base coordinate frame Seam frame. see Seam coordinate frame Sensor frame. see Sensor coordinate frame Torchtip frame. see Torchtip coordinate frame

gas metal arc (GMA) welding and 23 gas tungsten arc (GT A) welding and 23 hardware enhancements for 23 high-level control 104-5 implementation concerns 131 initial approaches

side-step algorithm 25 tracking planar seams 24--6 tracking sharp curves 2~ 7 tractrix algorithm 25

minimum radius of curvature of seam. see under Welding seam pattern recognition algorithms for 23 piecewise linear motion 160-2 robot motion control. see Low-level control strategies 25-7 tracking error

analysis 201 during tracking path points 160-2 from computing path points 158--60 sources 157-70 upper bound 156,197

Robot calibration Robot control module. see under ARTIST Robot endeffector

control Robot motion control. see Low-level control Robot, accuracy

218

factors affecting 172-6 improvement using closed loop methods 17S-79 issues 172-80 laser tracking system and 179, 180 methods for improving 175-79 open loop compensation and 177-8 robot calibration and 176

Robotic applications deburring 2 grinding 2 parts handling, transfer, sorting and inspection 2 using preprogrammed paths 2 robotic welding. see Robotic welding routing, drilling, honing, and polishing 2 spray painting 2-3 using tactile sensing 2

Robotic welding adaptation table for 187 arc welding 4-6 cameras for 14, 15 environment. see Robotic welding environment first generation systems 5 flXturing errors 4 heat resistant brushes 23 industrial robots for 3 joint sensing

through-the-arc. see Through-the-arc sensing vision. see 3D vision sensing

joint sensing 4 manual welding vs. 3 multi-pass 56, 195, 196 multiple sensors in 200 of circular penstocks 34 part positioning 4, 197 part-fmding 147,184 preprogrammed path 4, 105 second generation systems 5, 105 single pass 195, 196 spot welding 4

219

thennal distortion 4 third generation systems 27-9 torch leadllag angle 198 two-pass system 5 ultrasonic ranging and 184 weld planner 104, 200

Robotic welding 3-6 Robotic welding environment

structured image processing algorithms 38

unstructured feature extraction 38 feature recognition. see Seam recognition techniques seam tracking 84

unstructured 5,38 well-defmed 5

Robots accuracy. see Robot accuracy automation of physical production and 1 calibration 158, 176 compliant wrist 3 Cyro 193 end of ann tooling 158 end of ann tooling, errors 158, 176 GE P-50 process robot 181 general defmition 1 hazardous operations and 1 "ideal" design of 173 inverse kinematic solution 173 IRB 6AW, IRB L6AW 190 joint encoders in 89, 158, 174, 176 "non-ideal" robots 173, 175, 179 pick-and-place 3 PUMA series 560 137 repetitive operations and 1, 3 VAL programming language for 137 with vision sensors 3

RS232C asynchronous serial I/O 143

220

s

SAW 10 Scanning beam range sensor 65,132 Scanning beam range sensor

camera calibration 66-7 defme sensor frame

orientation component 68-9 origin coordinates 67-8

laser profiling gage. see Laser profiling gage range image

defmition 87 resolution 159 transformed in Interpretation frame 87

sensor calibration 65-6 torch-to-sensor coordinate transformation. see Torch-to-sensor

coordinate frame Seam coordinate frame

and seam geometry model 109 defmition 109-112 interpolating 112-13

Seam coordinate frame 59,80, 109, 145 Seam environment model 56-7, 102-3, 141 Seam geometry model, vee-joint

continuous model effect of window size 107 errors 160 polynomial approximation of root curve 106, 108

continuous model 105-9,142 discrete model

defming 109-12 seam coordinate frame and 109

discrete model 105,142 hybrid model

errors 160 hybrid model 105,141,198

Seam geometry model, vee-joint 105-14,141 Seam modeling error 160 Seam recognition techniques (in unstructured environment)

221

bottom-up approach. see Bottom-up seam recognition top-down approach. see Top-down seam recognition

Seam tracking in first generation robotic welding 5,21-22 in second generation robotic welding 5, 22-27 in third generation systems

attributes 28, 29 requirements 27

in unstructured environments 84 intelligent 6,27-9 realtime. see Realtime seam tracking two-pass

advantages, disadvantages 25 vision teach phase 22

two-pass 5,21-22,25 ultrasonic ranging for 8, 181, 183

Seam tracking system. see ARTIST Second central difference operation 50 Second difference operation 50 Second difference operation, window size 50 Segmentation algorithms

for contour representation 51 for vee-groove feature extraction 44-7 hopalong split-and-merge algorithm 51-2 Ramer's algorithm 53 split-dassify-merge-adjust algorithm 52-55

Selective spectrum filter. see Optical interference fIlter Sensor calibration

projector-camera range sensor 70-4 scanning beam range sensor 65-6

Sensor coordinate frame defInition

projector-camera range sensor 70-9 see also Projector-camera range sensor scanning beam range sensor 67-9 see also Scanning beam range sensor

torch-to-sensor coordinate transfonnation. see Torch-to-sensor coordinate transfonnation

Sensor coordinate frame 59,65-79, 145

222

Side-step algorithm, for realtime seam tracking 25 Smoothing fIlter 92 Stereo vision systems

cameras 15 problems 15

Stereo vision systems 14-16 Structured light systems

advantages over stereo vision 18 lambertian reflection and 17 multiple reflections and 18 specular surfaces and 17 using scanning beam 16 using sheet of light 16

Structured light systems 14, 16-18 Submerged arc welding (SAW) 10 Supervisory control module. see under ARTIST Supervisory microcomputer 138 Synchronizing concurrent operations in seam tracking 151

T

Through-the-arc seam tracking bolt-on robotic system 12 control algorithms 11 for planar seams 11 general purpose system 11-12 integrated robotic system 12 weave pattern programming 12

Through-the-arc seam tracking 8-11 Through-the-arc sensing

advantages, disadvantages 10 arc current 10, 11 arc voltage 10, 11 contact tip to work distance (CTWD) 9 economics of 10 flux -core arc welding (FCA W) and 11 gas metal arc welding (GMA W) and 11 self-regulating process in 10, 11 submerged arc welding (SAW) and 10

223

torch weaving action in 9 Through-the-arc sensing 8-11 Time of flight systems

advantages, disadvantages 19 lambertian reflection and 18 using amplitude modulation phase shift 18 using frequency modulation beat 18 using pulse time delay 18 using ultrasonic signals 19

Time of flight systems 18-19 Timed petrinet 151,152 Top-down seam recognition

in realtime seam tracking 39 initial range image evaluation 41,42 model based verification

for fillet joint 48 for split joint 47 for vee-joint 47

model based verification 41,42,47-8 OA V triple 41 overview 40 seam specific algorithm for feature extraction 41,42,44 seam type classification 41,42,43

Top-down seam recognition 38, 39, 40-8, 88 Torch-seam interaction 6,104 Torch-sensor lag 92,148 Torch-to-Sensor coordinate transformation 25,66,69,85 Torchtip coordinate frame

defmition orientation component 62-4 translation component 61-2

defmition 60-4 initial location 85 pointer for calibration 62

Torchtip coordinate frame 59-64,85,145 Tractrix algorithm, for realtime seam tracking 25 Triangulation 14 see also Laser triangulation Two-step ahead prediction algorithm 120-2

224

u

Ultrasonic ranging 181-3 Unimation, Inc. 137

v

VAL robot control language 137,145 Vee-grooved weld joint . see under Welding seam VME bus 132, 136

w

Weld path generation. see Low-level control Welding seam

minimum radius of curvature specifications based on allowable tracking error 163-4 based on range sensor's field of view 164-6 based on torch-sensor assembly design 166-8

types fillet joint 41, 48 split joint 41,42,43 vee-joint 44,45,46,47,56,57,84,88,89,93,99,102

World space 31

225