Assignment #4

Provide a short discussion of each of the assigned papers (listed under Course Materials). Below are some questions to think about:

RRT-Connect
Optional section: 4 (but try to understand what is being proved)

• Why don't we just use A* search?
• How is the simple one-directional RRT different (and preferable to) a "random walk" in the configuration space?
• What happens in this algorithm if a collision-free path does not exist?
• There is no explicit "heuristic" in this search, why does it work well (it does)?
• The authors mention "path smoothing", what is that and why is it important in this context?

Factored-Transition Systems

• Make sure that you watch the videos. Look for subgoaling, that is, doing something to enable some other goal, as opposed to being "reactive".
• Can we just frame this as an RRT search in a bigger configuration space that involves the poses on the robot and the objects?
• Why are conditional samplers needed?
• This approach can be implemented on a real robot (video) for some tasks. What is being assumed about the task? Think about the environment classification from Russell & Norvig.

Contact-Invariant Optimization

• Think about the connection between Section 1.1 in this paper and the ideas in the "Factored Transition" paper.
• What are the advantages/disadvantages of sampling-based methods vs optimization-based methods for planning motions?
• Compare and contrast Sections 4.3, 4.4 in this paper to STRIPS planning and Sims's evolutionary approach.
• How would this approach scale to doing manipulation in the presence of many objects, as in the "Factored Transition" paper?
• No one has managed to get this approach to work on a real robot; what do you think might make that hard?

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