CSE-473 Mobile Robot Mapping

Mapping with Raw Odometry

Graphical Model of Mapping u u u 1 t-1 ... x x x x 1 2 t m z z z 1 2 t

Graph-SLAM Idea

Robot Poses and Scans [Lu and Milios 1997] Successive robot poses connected by odometry Sensor readings yield constraints between poses Constraints represented by Gaussians Globally optimal estimate

Loop Closure Use scan patches to detect loop closure Add new position constraints Deform the network based on covariances of matches Before loop closure After loop closure

Mapping the Allen Center

108 features, 105 poses, only few secs using cg. 3D Outdoor Mapping 108 features, 105 poses, only few secs using cg.

Map Before Optimization

Map After Optimization

Rao-Blackwellized Mapping Compute a posterior over the map and possible trajectories of the robot : map and trajectory measurements map robot motion trajectory

… FastSLAM Robot Pose 2 x 2 Kalman Filters Landmark 1 Landmark 2 Landmark N … x, y,  Particle #1 Landmark 1 Landmark 2 Landmark N … x, y,  Particle #2 Landmark 1 Landmark 2 Landmark N … x, y,  Particle #3 … Particle M Landmark 1 Landmark 2 Landmark N … x, y,  [Begin courtesy of Mike Montemerlo]

Example 3 particles map of particle 3 map of particle 1

Rao-Blackwellized Mapping with Scan-Matching Map: Intel Research Lab Seattle Loop Closure

Rao-Blackwellized Mapping with Scan-Matching Map: Intel Research Lab Seattle Loop Closure

Rao-Blackwellized Mapping with Scan-Matching Map: Intel Research Lab Seattle

Example (Intel Lab) 15 particles four times faster than real-time P4, 2.8GHz 5cm resolution during scan matching 1cm resolution in final map joint work with Giorgio Grisetti

FastSLAM – Simulation Up to 100,000 landmarks 100 particles 103 times fewer parameters than EKF SLAM Blue line = true robot path Red line = estimated robot path Black dashed line = odometry

Victoria Park Results 4 km traverse 100 particles Uses negative evidence to remove spurious landmarks Blue path = odometry Red path = estimated path [End courtesy of Mike Montemerlo]

Frontier Based Exploration [Yamauchi et al. 96], [Thrun 98]

Multi-Robot Mapping Robot A Robot B Robot C