Local Control Methods Global path planning Expensive to plan in a dynamic world Dealing with dynamics of the robot is difficult => Global planner + local control method 4/27/2017 CS225B Kurt Konolige

Local Control Methods Potential fields Vector Field Histogram [Borenstein and Koren] Elastic Bands [Quinlan and Khatib] Elastic Strips [Brock and Khatib] Trajectory sampling Dynamic Window [Fox et al.] Trajectory Rollout [Gerkey et al.] Local gradient + lookahead control 4/27/2017 CS225B Kurt Konolige

Vector Field Histogram [Borenstein and Koren] Potential field method Workspace obstacles Obstacle probabilities from Cartesian histogram Polar histogram of good directions 4/27/2017 CS225B Kurt Konolige

Vector Field Histogram [Borenstein and Koren] Potential field method Workspace obstacles Obstacle probabilities from Cartesian histogram Polar histogram of good directions 4/27/2017 CS225B Kurt Konolige

Vector Field Histogram [Borenstein and Koren] Issues Width of robot, safety margin Cost function for handling tradeoffs: safety, progress, etc. Trajectory and dynamics Oscillation 4/27/2017 CS225B Kurt Konolige

4/27/2017 CS225B Kurt Konolige

Elastic Band [Quinlan and Khatib 1996] Smoothing by external and Internal forces Manhattan global path Obstacle Obstacle 4/27/2017 CS225B Kurt Konolige

Elastic Band [Quinlan and Khatib 1996] Bubbles along a path Internal forces minimizing length Exernal forces minimizing contact distance 4/27/2017 CS225B Kurt Konolige

Elastic Band [Quinlan and Khatib 1996] Bubbles along a path 4/27/2017 CS225B Kurt Konolige

Elastic Band [Quinlan and Khatib 1996] Implementation on Care-O-Bot and PR2 by Christian Connette 4/27/2017 CS225B Kurt Konolige

4/27/2017 CS225B Kurt Konolige

Dynamic Window Method [Fox et al.] Evaluating constant curvature path in configuration space Window of values based on one-step acceleration When will the robot crash? 4/27/2017 CS225B Kurt Konolige

Dynamic Window Method [Fox et al.] Admissible trajectories: braking before collision 4/27/2017 CS225B Kurt Konolige

Dynamic Window Method [Fox et al.] Heading: achieve the goal Distance: avoid obstacles Velocity: do it fast 4/27/2017 CS225B Kurt Konolige

Trajectory Rollout [Konolige et al.] DWA Issues Computation Evaluation function tuning: small openings Longer paths / lower acceleration Using the global path Desired velocities: 4/27/2017 CS225B Kurt Konolige