1. 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
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CS225B Kurt Konolige

2. 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

3. 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

4. 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

5. 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

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

8. 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

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

10. Elastic Band [Quinlan and Khatib 1996]
Implementation on Care-O-Bot and PR2 by Christian Connette
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CS225B Kurt Konolige

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12. 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

13. Dynamic Window Method [Fox et al.]
Admissible trajectories: braking before collision
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CS225B Kurt Konolige

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

15. 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