[ros-users] Problem with PR2 Simulator IK Tutorial

[Gal Peleg]

Hi guys, I hope all is well.

My classmate and I are relatively new to ROS.  In our attempts to run
through the "Moving the arm through a Cartesian pose trajectory using
inverse kinematics <*
http://www.ros.org/wiki/pr2/Tutorials/Moving%20the%20arm%20through%20a%20Cartesian%20pose%20trajectory?action=fullsearch&context=180&value=linkto%3A%22pr2/Tutorials/Moving+the+arm+through+a+Cartesian+pose+trajectory%22
*> " tutorial, we ran into some difficulties.

We managed to get all the files/packages to compile as outlined in the
tutorial, but were unable to execute the last step. In particular, the
turoial asks you to execute:
python scripts/test_ik_trajectory_tutorial.py
 after running:
bin/ik_trajectory_tutorial
which fails.  The script says that the trajectory failed, but the actual
reason for failure appears to be a segmentation fault due to a null pointer
in ik_trajectory_tutorial.cpp after the line:
     bool ik_service_call = ik_client.call(ik_request,ik_response);
when the code tries to access the data stored in ik_response.
      solution[i] = ik_response.solution.joint_state.position[i];

The addresses appear to be valid, but actually accessing any value within
position leads to the segfault.  We attempted to trace back the calls
through pr2_arm_ik_node, pr2_arm_ik_solver, and pr2_ik_arm, but were unable
to determine exactly what went wrong when trying to convert the Cartesian
coordinates in joint space.

Any help is appreciated. Really, all we are trying to do at the end of the
day is become familiar with a working implementation of an IK solver for the
PR2 arms. So if anyone knows of a better (working) tutorial, that would be
great as well.

Thanks again!

Gal & Sam
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