Calibration of Industrial Robot Manipulators

The book mostly focuses upon the calibration of industrial robot manipulators. It describes the reasons for calibrating robots, the complete process, the situation in industry today, and future prospects. It takes the scientific aspect as a basis, but linked with the industrial world through practical methods and follow-up. To help with the general understanding, it explains from an historical point of view, how the evolution of technologies has enabled us to reach the current level of knowledge. Through the successes and failures of industrial examples it provides the reason calibration is a major aspect for fulfilling the requirements of an innovative automated manufacturing line.

Table of Contents:
Introduction 13 Chapter 1. Historical facts 17 1.1. Introduction 17 1.2. History of technologies 19 1.2.1. Men and the first technologies in search of time 19 1.2.2. From the time to the mechanical automatons 22 1.2.3. From the wheel to the speed of light 26 1.2.4. Electricity: a giant step ahead 27 1.2.5. When the mechanical automatons gave way to automation 32 1.2.6. Towards the computer 35 1.3. History of robotics 38 1.3.1. Social considerations 38 1.3.2. General technical information 38 1.3.3. The beginning of hydraulic in robotics 39 1.3.4. Birth of industrial robotics 40 1.3.5. Spot welding and evolution of the assembly lines 42 1.3.6. The introduction on a large scale of the robots on assembly lines 44 1.3.7. Electric robots at Unimation 45 1.3.8. And Europe? The battle of painting 46 1.3.9. First world major objectives 48 1.3.10. The industrial beginning of the electric robots 49 1.3.11. The battle lost by the hydraulic robots 50 1.3.12. The reasons of the victory of the electric robots 52 1.3.13. The parallel structures, their effective entrance in the industry 60 1.3.14. The robotic industry today in short 62 1.3.15. The robotic industry in France and its chaotic course 63 1.3.16. Numbers and statistics 64 1.3.16.1. Analyzes by geographical areas: 66 1.3.16.2. The worldwide market: almost 1 million robots 67 1.3.16.3 2007: a growth of 10% 67 1.3.16.4. Future: a strong growth 68 1.3.16.5. Conclusion 69 1.4. History of the robot programming 70 1.4.1. Programming by teaching from an absolute reference point 70 1.4.2. The contribution of the reference frames 71 1.4.3. The specification of the programming of painting robots 71 1.4.4. The awakening 74 1.4.5. In the pain the Off line Programming (OLP) began essential 75 Chapter 2. Robot manipulators, Off Line Programming and calibration 79 2.1. The robot manipulators 79 2.1.1. Terminology and definitions 79 2.1.2. Advantages and disadvantages of the various types of robot manipulators 86 2.1.3. Representation of the robots structures 87 2.1.4. Serial robot manipulators 91 2.1.4.1. The anthropomorphic structure 92 2.1.4.2. The SCARA structure 92 2.1.4.3. The cartesian structure 94 2.1.4.4. The spherical and cylindrical structures 95 2.1.4.5. Specification of some current serial structures 96 2.1.5. Parallel robot manipulators 98 2.1.5.1. The plane structures 99 2.1.5.2. The Delta structures 99 2.1.5.3. The hexapod structures 101 2.1.5.4. Other structures 103 2.1.5.5. Applications of the parallel structures 106 2.1.6. Reference frames used in robotics 111 2.1.7. Criteria of performance of the industrial robots 112 2.1.7.1. Characteristics of robot poses 113 2.1.7.2. Calculation of the repeatability, the absolute accuracy and the robot compliance 117 2.1.7.3. Characteristics of robot trajectories 125 2.1.8. Definition of the singular configurations of the manipulating robot 126 2.2. The Off Line Programming and its limits 129 2.2.1. The programming of industrial robots 129 2.2.2. The Off Line Programming (OLP) 130 2.2.2.1. Programming languages 131 2.2.2.2. CAD/CAM robotic systems 131 2.2.3. Limitations and error sources of OLP 136 2.2.4. Sources of errors degrading the robot pose accuracy 138 2.2.4.1. Systematic sources of pose errors 138 2.2.4.2. Random pose errors 139 2.2.5. Real position of the OLP 139 2.2.6. Improvement of the OLP 140 2.2.6.1. On the CAD/CAM level 140 2.2.6.2. On the robotic cell level 141 2.3.1. Definitions of the calibration of the industrial robot manipulators 144 2.3.1.1. Restrictive definitions limited to the robot 144 2.3.1.2. Definition widened (industrial) 144 2.3.2. Targets of the industrial calibration 145 Chapter 3. General principles of the calibration 147 3.1. The various levels of calibration 147 3.1.1. Level 1: joint calibration 148 3.1.2. Level 2: geometrical calibration 149 3.1.3. Level 3: non-geometrical calibration 149 3.2. The various methods of calibration 150 3.3. External methods of calibration 150 3.3.1. Global method 151 3.3.1.1. Principle 151 3.3.1.2. Stage of modelling 151 3.3.1.3. Stage of measurements 154 3.3.1.4. Identification 163 3.3.1.5. Compensation and verification 179 3.3.1.6. Advantages and disadvantages 181 3.3.2. Independent axis calibration method 182 3.3.2.1. Principle 182 3.3.2.2. Advantages and disadvantages 184 3.3.3. Error mapping calibration method 186 3.3.3.1. Principle 186 3.3.3.2. Advantages and disadvantages 187 3.4. Self-calibration method 187 3.4.1. Under constraint calibration method 187 3.4.1.1. Principle 187 3.4.1.2. Types of constraints used 188 3.4.1.3. Advantages and disadvantages 190 3.4.2. Fully autonomous calibration methods 191 3.4.2.1. General principle 191 3.4.2.2. Calibration by addition of proprioceptive sensors 191 3.4.2.3. Calibration under singularities 192 3.4.2.4. Advantages and disadvantages 194 3.5. Limits of the geometrical calibration 195 3.6. Non geometrical calibration 196 3.6.1. Compensation of elastic deformations 196 3.6.1.1. Elasto-geometrical modelling 196 3.6.1.2. Elasto-geometrical modelling by using elastic beam elements 198 3.6.1.3. Elastic and elasto geometrical calibrations 208 3.6.2. Compensation of backlashes and transmission error effects 214 3.6.3. Compensation of the temperature effects 215 3.7. Carrying forward of the calibration results, memorizing and follow-up 215 3.8. Conclusion 217 Chapter 4. Calibration of the serial robots 219 4.1. Specificity of the serial robot calibration 219 4.2. Geometrical calibration 220 4.2.1. Modelling 220 4.2.1.1. Modelling of 0Tn 221 4.2.1.2. Modelling of -1T0 and of nTn+1 227 4.2.1.3. Modelling of -1Tp 227 4.2.1.4. Modelling of -1Tn+1 228 4.2.1.5. Property of a good calibration model 228 4.2.1.6. Example: the TX-90 Staubli robot 228 4.2.2. Measurements 232 4.2.3. Identification 235 4.2.3.1. Linear identification 235 4.2.3.2. Non-linear identification 243 4.2.3.3. Example 245 4.2.4. Compensation and verification 246 4.3. Non-geometrical calibration 246 4.3.1. Compensation of the robot elastic deformations 246 4.3.1.1. Example 248 4.4. Conclusion 254 Chapter 5. Calibration of the parallel robots 257 5.1. Specificity of the calibration of robots and machines having parallel structure 257 5.2. Geometrical calibration 258 5.2.1. Modelling 258 5.2.1.1. Inverse geometrical model 258 5.2.1.2. Direct geometrical model 260 5.2.1.3. Properties of good models 261 5.2.1.4. Example: the Gough platform 262 5.2.2. Measurements 268 5.2.3. Identification 271 5.2.3.1. Direct method 271 5.2.3.2. Inverse method 273 5.2.3.3. Example: the platform of Gough 275 5.2.3.4. Comparison and synthesis 283 5.2.4. Compensation 287 5.3. Non-geometrical calibration 288 5.3.1. Compensation of the elastic deformations 288 5.4. Conclusion 296 Chapter 6. Innovation and calibration 299 6.1. General information 299 6.2. Universal examples of innovations 300 6.2.1. Wind turbine and windmill 300 6.2.2. Thermal engine 302 6.3. Some great innovators 304 6.3.1. Archimede: A genius of antiquity 304 6.3.2. Leonardo da Vinci: A genius of the Renaissance 305 6.4. The innovation: how to run it? 307 6.4.1. The innovation in robotics 307 6.4.2. Successes and failures 308 6.4.2.1. Successes 308 6.4.2.2. The deplorable practice to fire people of experiment 316 6.4.2.3. Bitter failures 317 6.4.2.4. Conclusion 322 6.4.3. The Innovation through the robotic calibration 322 6.4.4. An innovating standard approach 325 Conclusion 327 Appendices 331 A. Characteristics of some current industrial serial structures 331 Bibliography 341