CoppeliaSim forums

Hello,


I create this post because I’m having hard times trying to solve path planning issues on VREP.

I am trying to use the OMPL path planner to find non colliding path in a quite constrained environment.
You can find an extract of my scene here :
https://drive.google.com/file/d/0B2UQEe ... p=drivesdk
(just press play and the robot will go from one dummy to another and you will see sometimes collisions)

The problem is that is doesn’t work every time, I’d say it has 70% chance of working but it is not enough for my project.
Indeed the path planner:
- Sometimes doesn’t find the complete path, it stops before the goal dummy
- Sometimes it creates a path with collision in the middle of the path which is problematic

I don’t understand why sometimes the path planner returns me a path that contains collision along the path. I tried several OMPL algorithm but it didn’t solve the problem. Could anyone help me ?

Thanks in advance,

Julien

Hello,

I think there are 2 things at play:

• if the goal isn't reached, it most probably is because the max. calculation time has been exceeded (edit: new plugin versions can use simOMPL.hasSolution to know if a solution has been found, which may be exact in which case simOMPL.hasExactSolution returns true, or approximate, in which case distance to goal can be checked with simOMPL.getGoalDistance)
• if there are collisions on the way, this is because your checking resolution is too large (the robot can jump over obstacles from one collision-free node to the other). Maybe adjusting things with simOMPL.setStateValidityCheckingResolution can help?

Cheers

Hello,

It looks like it's working now with your two advices.

Thanks a lot !

Cheers,

Julien

Hi, Friends:

Sorry for bothering, Can I have any idea to how to using simOMPL.setStateValidityCheckingResolution?

Thanks for your time, looking forward to your reply!


Yours Sincerely
Jack

As the documentation states, specify the resolution of state validity checking, expressed as fraction of state space's extent . If the extent of your space is 10 meters and your smallest obstacle / robot is 0.1 meter, then specify a value smaller than 0.01

Cheers

Hi, Coppelia:

Thanks you so much!


Yours Sincerely
Jack