[ros-users] Problem with PR2 Simulator IK Tutorial

Sachin Chitta sachinc at willowgarage.com
Wed Mar 10 01:02:57 UTC 2010

Hi Gal,

That tutorial is outdated. Sorry about that. You can have a look at more
recent tutorials for working with the ik at:

We are in the process of releasing the kinematics code with a new ROS api.
The api changes include an update to the name of the stack, so the tutorials
will move to

Expect the api changes to happen within the next few days. I will send an
email to the ros-users list with more information when we are ready and


On Tue, Mar 9, 2010 at 4:39 PM, Gal Peleg <galpeleg13 at gmail.com> wrote:

> 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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> ros-users at code.ros.org
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Sachin Chitta
Research Scientist
Willow Garage
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