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I have run through the new arm planning wizard (arm_navigation version 1.0.2) and everything went smoothly to generate a set of configuration and launch files for my 5-dof Dynamixel arm.

Now I am trying to run the move_arm_joint_goal.cpp example found here. I had to substitute arm_navigation_msgs for move_arm_msgs but otherwise the sample code compiles and runs fine. The only trouble is that when I try specifying a simple joint goal (like all joint positions = 0 which has the arm pointing straight out from the robot), I always get the error message:

[ERROR] [1312993060.885707724]: Starting state is in collision, can't plan

and the arm does not move. It doesn't matter how I initially position the arm, the goal attempt always fails with the same error. My Dynamixel controller node publishes a valid set of joint positions on the /joint_states topic as I can verify in RViz.

UPDATE: After more testing, these are my consistent findings:

  • after running the wizard in easy mode, the planning visualizer cannot find IK solutions for any attempted positioning of the end effector.

  • When connected to the real robot and sending a move_arm_joint_goal with the arm initially straight out and slightly down, planning fails, reporting that the finger and thumb links are in collision with the base link even though both links are about 4 inches away from the base (including the collision envelopes around the links).

  • Moving the arm to any position further away from the base solves the problem: a planning solution is found and the arm moves perfectly.

  • Disabling collision checking between the base link and finger and thumb links also solves the problem but of course is not ideal since the thumb and finger might fairly often come into collision with the base during operations where the hand reaches for something on the ground


Originally posted by Pi Robot on ROS Answers with karma: 4046 on 2011-08-10

Post score: 0


1 Answer 1


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This particular problem was caused by a scaling error on COLLADA meshes in arm_navigation that has been rectified in the newest debs - update and things should be good (and check out the sweet new wizard logo).

Originally posted by egiljones with karma: 2031 on 2011-08-24

This answer was ACCEPTED on the original site

Post score: 1

Original comments

Comment by egiljones on 2011-08-25:
Yeah, I just managed to beat Qt into allowing resizing all the way down yesterday - I'll release in the next couple days.

Comment by Pi Robot on 2011-08-25:
Nice new wizard logo! Only one glitch--on my 1280x800 laptop screen, the wizard dialog box now runs off the bottom of the screen so that I do not have access to the buttons. I can hit Return at the right places to get the wizard to work, but I can't resize the window to allow me to see the buttons at the bottom.

Comment by Pi Robot on 2011-08-24:
Cool--will give it a try this weekend.


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