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