10 - Local Path Planning

Question 1

Bug algo assumptions

Answer 1

• Robot is a point in a 2D world
• Robot can execute a trajectory that follows the obstacle boundary
• Robot always knows the direction and euclidean distance to the goal
• initial and goal positions are defined

Question 2

Why bug algos?

Answer 2

• Simple inutitive
• Straightforward implementation
• Guaranteed success
• Assumes perfect positioning and sensing

Question 3

Bug-0 Algorithm

Answer 3

Switching between two simple behaviours
1. Move directly towards goal
2. Follow boundary

• Toward goal
• If obstacle, follow obstacle (either left or right depending on set up) until you can head toward goal again
• Continue

Question 4

Encoder

Answer 4

Provides a feedback signal to determine position, speed etc

Question 5

Bug 1 Algo

Answer 5

1. Head toward Goal
2. If obstacle, circumnaviagte it and remember how close you get to the goal
3. Return to the closest point and continue
4. If robot cannot continue from here, then conclude goal is not reachable

Question 6

Lower and upper bound of distance (D is distance to goal and Pi is the perimeter) in bug 1

Answer 6

Lower: D
Upper: D + 1.5 sum(i)(Pi)

Question 7

Bug-2 Algo

Answer 7

1. Head toward goal on the m-line
2. If obstacle, follow obstacle until reaching m-line again closer to goal (ignore repeated points)
   3) Leave the obstacle and continue with step one

m-line is a line from the start to the goal

Question 8

Lower and upper bound of distance (D is distance to goal and Pi is the perimeter) in bug 2

Answer 8

lower: D
Upper: D + 0.5sum(i)(NiPi)

Question 9

Bug 1 vs Bug2: Search type

Answer 9

Bug1: Exhaustive Search
Bug2: Opportunistic (Greedy)

Question 10

Bug1 vs Bug2: Complex vs Simple Obstacles

Answer 10

Bug1: Complex
Bug2: Simples