prepared by xiaoshan pan
DESCRIPTION
Interactive Navigation in Complex Environments Using Path Planning Salomon et al.(2003) University of North Carolina. Prepared By Xiaoshan Pan. Content. 1 st section (3/4) Pre-compute a global roadmap Graph search (ini goal) in real-time Display motion 2 nd section (1/4) - PowerPoint PPT PresentationTRANSCRIPT
Interactive Navigation in Complex Environments Using Path Planning
Salomon et al.(2003) University of North Carolina
Prepared By Xiaoshan Pan
Content
1st section (3/4)– Pre-compute a global roadmap– Graph search (inigoal) in real-time– Display motion
2nd section (1/4)– User-steered exploration
Basic Idea
Preprocessing phase
Runtime algorithm
Precomputation: Sampling
Gravity
•Shooting rays
Random Rays
Precomputation: Sampling
Gravity
•Shooting rays
ө ө
•Walkable surface
•Construct roadmap
-Max # of samples
-Min dist between samples
•Connectors - Rc > Rg
Rc
Guards & Connectors (C-space)
•Reachability (vs. visibility)
Rg
•Guards - guards can’t see each other
- yes reject c, goto while
c
- no! c becomes a Guard, connect to connectors (if any), goto while
Algorithm (build_roadmap)
While (map_coverage < P_cover), do // map_coverage = guards_reachable/entire_space
Return roadmap
Connector
GuardGuard
Connector
GuardGuard
Connector
GuardGuard
2. Can c be a Connector? See any Guards in Rc? - Yes then connect, goto while (else goto 3)
1. Pick a random config. c
c
3. Can c be a Guard? See any Guards in Rg?
c
Be a Connector Be a Guard Be rejected
Search for a path: init goal Initial position (Rc radius)
ini
goal
Goal position Graph search…
Display Motion: Smooth Path Walk along the path
ini
goal
Smoothing path (cutting redundant corners while walking)
User-steered exploration (local walk)
User has control– A directional vector
Robot always stays on a walkable surface
– In free space– Surface within a tolerance
angle– Steps ok, cliffs NO!!
Robot do not penetrate objects
Local Walk Algorithm
Follow the directional vector, if- Goal is reached, stop
- Collision, project along obstacle edge
- New surface, step up/down (not a cliff!)- Edge, step up/down or project along the edge
Discussion
Can deal with complex environment– Because it pre-computes a global roadmap.
Still…– Pre-computation could be time consuming.– Walking along line segments does not look
natural. Overall assessment: Pretty good