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Configuration Spaces for Translating Robots Minkowsi Sum/Difference. David Johnson. C-Obstacles. Convert robot and obstacles point and configuration space obstacles. C-space robot and obstacle. Workspace robot and obstacle. Translating Robots. Most C-obstacles have mysterious form
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Configuration Spaces for Translating RobotsMinkowsi Sum/Difference David Johnson
C-Obstacles • Convert • robot and obstacles • point and configuration space obstacles C-space robot and obstacle Workspace robot and obstacle
Translating Robots • Most C-obstacles have mysterious form • Special case for translating robots • Look at the 1D case -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 robot obstacle
Translating Robots • What translations of the robot result in a collision? -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 robot obstacle
Minkowski Difference • The red C-obs is the Minkowski difference of the robot and the obstacle -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 robot obstacle
Minkowski Sum • First, let us define the Minkowski Sum
Minkowski Sum B A
Applet The Minkowski sum is like a convolution A related operation produces the C-obs Minkowski difference Minkowski Sum Example
Back to the 1D Example • What translations of the robot result in a collision? -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 robot obstacle
From sets to polygons • Set definitions are not very practical/implementable • For polygons, only need to consider vertices • Computationally tractable
For obstacle O and robot R if O - R contains the origin Collision! Properties of Minkowski Difference
The closest point on the Minkowski difference to the origin is the distance between polygons Distance between polygons Another property
Example • Applet
Discussion • Given a polygonal, translating robot • Polygonal obstacles • Compute exact configuration space obstacle • Next class – how will we use this to make paths?