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Lane Detection for DEXTER, an Autonomous Robot, in the Urban Challenge

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Lane Detection for DEXTER, an Autonomous Robot, in the Urban Challenge Lane Detection for DEXTER, an Autonomous Robot, in the Urban Challenge by SCOTT MCMICHAEL Submitted in partial fulfillment of the requirements For the degree of Master of Science Thesis Adviser: Dr. Wyatt Newman Department of Electrical Engineering and Computer Science CASE WESTERN RESERVE UNIVERSITY May 2008 CASE WESTERN RESERVE UNIVERSITY SCHOOL OF GRADUATE STUDIES We hereby approve the thesis/dissertation of _____________________________________________________ candidate for the ______________________degree *. (signed)_______________________________________________ (chair of the committee) ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ (date) _______________________ *We also certify that written approval has been obtained for any proprietary material contained therein. Table of Contents Table of Contents ................................................................................................................ 2 Table of Figures ................................................................................................................... 6 1 ‐ Abstract .......................................................................................................................... 8 2 ‐ Introduction ................................................................................................................... 9 3 ‐ Background .................................................................................................................. 11 4 ‐ Hardware Platform ...................................................................................................... 14 4.1 ‐ DEXTER .................................................................................................................. 14 4.2 ‐ Cameras ................................................................................................................. 16 4.3 ‐ Laser Scanners ....................................................................................................... 19 4.4 ‐ Infrared Cameras ................................................................................................... 20 4.5 ‐ Computers ............................................................................................................. 21 5 ‐ Software Architecture .................................................................................................. 22 5.1 ‐ Overview ............................................................................................................... 23 5.2 ‐ Lane Detection System .......................................................................................... 25 5.2.1 ‐ Sensor Fusion Theory ..................................................................................... 26 5.2.2 – Steering Command Chain .............................................................................. 28 6 ‐ Road Detection Modules ............................................................................................. 29 6.1 ‐ Rake Edge Detector ............................................................................................... 31 2 6.2 ‐ Color Roadbed Detector ....................................................................................... 31 6.3 ‐ Texture Road Detector .......................................................................................... 33 6.4 ‐ Side Camera Road Detectors ................................................................................ 33 6.5 ‐ LIDAR Road Detector ............................................................................................. 34 7 ‐ Edge Crawler ................................................................................................................ 34 7.1 ‐ Curve Extraction .................................................................................................... 35 7.2 ‐ Curve Filtering ....................................................................................................... 37 7.2.1 ‐ Simple Filtering ............................................................................................... 38 7.2.2 ‐ Curve Breakup ................................................................................................ 38 7.2.3 ‐ Curve Fit Filtering ........................................................................................... 40 7.2.4 ‐ Expectation Filtering ....................................................................................... 41 7.3 ‐ Confidence Estimation and Formatting ................................................................ 43 8 ‐ Road Tracker ................................................................................................................ 43 8.1 ‐ Get Context Information ....................................................................................... 44 8.2 ‐ Line Tracking ......................................................................................................... 46 8.2.1 ‐ Line Input ........................................................................................................ 46 8.2.2 ‐ Line Maintenance ........................................................................................... 46 8.2.3 ‐ Line Merging ................................................................................................... 47 8.3 ‐ Line Identification ................................................................................................. 49 3 8.4 ‐ Centerline Estimation ............................................................................................ 53 9 ‐ Lane Observer .............................................................................................................. 55 9.1 ‐ Map Query Sequence ............................................................................................ 55 9.2 ‐ Sensor Filtering ...................................................................................................... 57 9.3 ‐ Source Selection .................................................................................................... 59 10 ‐ Test Site Performance ................................................................................................ 64 10.1 ‐ Case Quad ........................................................................................................... 64 10.2 ‐ Squire Valleview Farm ......................................................................................... 68 10.3 ‐ Beachwood .......................................................................................................... 69 10.4 ‐ Plumbrook ........................................................................................................... 70 10.5 ‐ National Qualifying Event ................................................................................... 77 11 ‐ Analysis and Future Work .......................................................................................... 80 11.1 ‐ Edge Crawler ....................................................................................................... 80 11.2 ‐ Road Tracker ....................................................................................................... 82 11.3 ‐ Lane Observer ..................................................................................................... 84 11.4 ‐ Future Development ........................................................................................... 85 12 ‐ Conclusions ................................................................................................................ 86 13 ‐ Appendices ................................................................................................................. 87 Appendix A – Common Algorithms ............................................................................... 87 4 A1 ‐ Line Fit Difference Calculation ........................................................................... 87 A2 ‐ Polynomial Fitting............................................................................................... 87 A3 ‐ Line Fit Merging .................................................................................................. 87 A4 ‐ RANSAC Line Fit .................................................................................................. 91 A5 –Path Divergence Detection ................................................................................. 93 Appendix B – Sensor Calibration ................................................................................... 93 Appendix C – Coordinate Frames .................................................................................. 95 Appendix D – Position Shift Steering............................................................................. 97 14 ‐ References ............................................................................................................... 100 5 Table of Figures Figure 1 ‐ DEXTER as received by Team CASE.. ................................................................. 14 Figure 2 ‐ DEXTER as it competed in the National Qualifying Event.. .............................. 16 Figure 3 – Lane detection sensor diagram. ....................................................................... 18 Figure 4 ‐ Computer usage by the lane detection system. ............................................... 22 Figure
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