Motion Vision - Design of Compact Motion Sensing Solutions for Navigation of Autonomous Systems

Contents......Page 8
Preface......Page 14
List of abbreviations......Page 20
Symbols......Page 22
Typographical conventions......Page 26
Acknowledgements......Page 28
1 Introduction......Page 30
1.1.1 Inputs and outputs......Page 31
1.1.2 Real-time motion estimation......Page 32
1.1.3 The motion estimation algorithm......Page 34
1.1.4 The prototype sensor......Page 36
PART 1 – BACKGROUND......Page 38
2.1 Basic concepts in probability......Page 40
2.1.3 Event......Page 41
2.1.5 Conditional probability......Page 42
2.1.8 OR......Page 43
2.1.9 AND......Page 44
2.1.13 Random variable......Page 45
2.1.15 Cumulative Distribution Function (CDF)......Page 46
2.1.16 Joint distribution functions......Page 47
2.1.20 Random or stochastic processes......Page 48
2.1.21 Stationary processes......Page 49
2.1.23 Variance......Page 50
2.1.25 Likelihood......Page 51
2.2.1 Linear regression......Page 52
2.2.2 Solving linear regression problems......Page 55
2.2.3 The Hough transform......Page 56
2.2.4 Solving Hough transform problems......Page 57
2.2.5 Multiple linear regression and regularisation......Page 58
2.2.6 Solving the membrane model......Page 62
2.2.7 Location estimates......Page 68
2.2.8 Solving location estimation problems......Page 69
2.2.9 Properties of simple estimators......Page 71
2.3.1 Outliers and leverage points......Page 72
2.3.2 Properties of robust estimators......Page 76
2.3.3 Some robust estimators......Page 79
3 Motion estimation......Page 92
3.1 The motion estimation problem......Page 93
3.2 Visual motion estimation......Page 94
3.2.1 Brightness constancy......Page 95
3.2.3 Gradient based motion estimation......Page 98
3.2.4 Displaced frame difference......Page 105
3.2.5 Variations of the OFCE......Page 108
3.2.6 Token based motion estimation......Page 110
3.2.7 Frequency domain motion estimation......Page 114
3.2.8 Multiple motions......Page 116
3.3 Temporal integration......Page 124
3.4 Alternate motion estimation techniques......Page 125
3.5 Motion estimation hardware......Page 127
3.6 Proposed motion sensor......Page 129
PART 2 – ALGORITHM DEVELOPMENT......Page 130
4.1 Frequency domain analysis of image motion......Page 132
4.2 Rigid body motion and the pinhole camera model......Page 135
4.3 Linking temporal aliasing to the safety margin......Page 138
4.4 Scale space......Page 140
4.5 Dynamic scale space......Page 142
4.6 Issues surrounding a dynamic scale space......Page 143
5.1 Assumptions, requirements and principles......Page 146
5.1.2 Data sources......Page 147
5.1.3 Motion......Page 150
5.1.4 Environment......Page 152
5.2.1 Inputs and outputs......Page 153
5.2.2 Constraint equation......Page 154
5.2.3 Derivative estimation – practicalities......Page 155
5.2.4 Effect of illumination change......Page 160
5.2.5 Robust average......Page 161
5.2.6 Comparing our robust average to other techniques......Page 166
5.2.7 Monte Carlo study of the LTSV estimator......Page 175
5.2.9 Dynamic scale space implementation......Page 182
5.2.10 Temporal integration implementation......Page 183
5.2.12 Simulation results......Page 185
5.3 Navigation using the motion estimate......Page 193
PART 3 – HARDWARE......Page 200
6 Digital design......Page 202
6.2 How do I specify what my FPGA does?......Page 203
6.3 The FPGA design process in a nutshell......Page 204
6.4 Time......Page 206
6.6 Introducing VHDL......Page 207
6.6.1 VHDL entities and architectures......Page 208
6.6.2 VHDL types and libraries......Page 211
6.6.3 Concurrent and sequential statements......Page 219
6.6.4 Inference......Page 228
6.7 Timing constraints......Page 230
6.8.1 Synchronisation and metastability......Page 233
6.8.4 Tristate buffers......Page 235
6.8.5 Don’t gate clocks......Page 236
6.8.10 Use of hierarchy......Page 237
6.8.12 Bit width......Page 239
6.9 Graphical design entry......Page 240
6.9.1 State machines......Page 241
6.9.2 A more complex design......Page 250
6.10 Applying our design method......Page 259
7 Sensor implementation......Page 260
7.1.1 Image sensor......Page 261
7.1.2 Range sensor......Page 263
7.1.4 PC......Page 265
7.2 FPGA system design......Page 266
7.2.1 Boot process......Page 267
7.2.2 Order of operations......Page 268
7.2.3 Memory management......Page 269
7.2.4 RAMIC......Page 273
7.2.5 Buffers......Page 279
7.2.6 Data paths......Page 282
7.3.2 Aligning the camera and range sensors......Page 299
7.3.4 Moving camera – effect of barrel distortion......Page 302
7.3.6 Moving camera – image noise......Page 305
7.4 Implementation statistics......Page 306
7.5.1 Dynamic scale space......Page 307
7.5.3 Temporal integration......Page 309
7.5.6 Extending the hardware......Page 310
PART 4 – APPENDICES......Page 312
A System timing......Page 314
A.1 Timing for a 512 × 32 pixel image......Page 315
A.2 Control flow for a 512 × 32 pixel image......Page 316
A.3 Timing for a 32 × 32 pixel image......Page 317
A.4 Control flow for a 32 × 32 pixel image......Page 318
A.5 Legend for timing diagrams......Page 319
A.5.1 Note 1: image data clobbering......Page 323
A.5.4 Note 4: the first frame......Page 324
B.1 Powerup sequence......Page 326
B.3 Write cycle......Page 327
C.1 Summary of design components......Page 330
C.2 Top level schematic......Page 335
C.3 RAMIC......Page 336
C.4 Buffers......Page 347
C.4.1 Camera data path......Page 362
C.5 Laser and PC data paths......Page 369
C.6 Processing......Page 373
C.7 Miscellaneous components......Page 389
C.8 User constraints file......Page 397
D Simulation of range data......Page 406
Bibliography......Page 424
Index......Page 446