Moveit planning pipeline and its error conditions

[Tim Steuer]

Hi,


I just started my work with a Baxter robot and moveIt. So far everything works well but I have some basic questions regarding the move planning. I am new to robotics and I would be very grateful if you guys could help me to get a better understanding of what’s happening.

Sometimes I get a “ABORTED: no motion plan found” error message. The detail log states either something like “IK failed” or “Unable to sample any valid states for goal tree”. Does this mean it exists no trajectory given the current state of the robot and the environment? Or does it mean that the planner could not find a trajectory in the current run but maybe find one in the next run? Is there a way of knowing if there is a chance to find a way in another run (by some parameter or return value)?

In addition, I wonder if it is useful to switch to another planner (e.g from LBKPiece to RRTConnect) if the first one does not find a motion plan or if this is useless.


Thanks,

Tim

 

[Dave Hershberger]

"IK failed" means that it can't find any configuration of the arm that puts the end-effector in the goal pose. Often this happens because the goal is not in the workspace of the arm. If this is really the case, then the arm physically cannot reach the given pose, so using a different planning algorithm will not help.

I realize the error message is a bit non-intuitive. Maybe it would be clearer if it said "Arm cannot reach goal". However, "IK failed" is actually more precise, because there can be problems with IK algorithms where they fail even though the pose is physically reachable.

Dave
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From: moveit...@googlegroups.com [moveit...@googlegroups.com] on behalf of Tim Steuer [steue...@gmail.com]
Sent: Monday, May 26, 2014 7:53 PM
To: moveit...@googlegroups.com
Subject: Moveit planning pipeline and its error conditions