local control methods global path planning
DESCRIPTION
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 KonoligeTRANSCRIPT
05/06/23 CS225B Kurt Konolige
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
05/06/23 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
05/06/23 CS225B Kurt Konolige
Vector Field Histogram [Borenstein and Koren]
Potential field method
• Workspace obstacles• Obstacle probabilities from Cartesian histogram• Polar histogram of good directions
05/06/23 CS225B Kurt Konolige
Vector Field Histogram [Borenstein and Koren]
Potential field method
• Workspace obstacles• Obstacle probabilities from Cartesian histogram• Polar histogram of good directions
05/06/23 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
05/06/23 CS225B Kurt Konolige
05/06/23 CS225B Kurt Konolige
Elastic Band [Quinlan and Khatib 1996]
Manhattanglobal path
Smoothing byexternal andInternal forces
Obstacle Obstacle
05/06/23 CS225B Kurt Konolige
Elastic Band [Quinlan and Khatib 1996]
Bubbles along a pathInternal forces minimizing length
Exernal forces minimizing contactdistance
05/06/23 CS225B Kurt Konolige
Elastic Band [Quinlan and Khatib 1996]
Bubbles along a path
05/06/23 CS225B Kurt Konolige
Elastic Band [Quinlan and Khatib 1996]
Implementation on Care-O-Bot and PR2 by Christian Connette
05/06/23 CS225B Kurt Konolige
05/06/23 CS225B Kurt Konolige
Dynamic Window Method [Fox et al.]
Evaluating constant curvature path in configuration spaceWindow of values based on one-step accelerationWhen will the robot crash?
dtadtadtavvdtav
vR
cc
vcvc
/
05/06/23 CS225B Kurt Konolige
Dynamic Window Method [Fox et al.]
dtadtadtavvdtav
vR
cc
vcvc
/
Admissible trajectories: braking before collision
05/06/23 CS225B Kurt Konolige
Dynamic Window Method [Fox et al.]
Heading: achieve the goalDistance: avoid obstaclesVelocity: do it fast
05/06/23 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: