[ros-users] replicating pr2_arm_kinematics for 6-DOF arm

[David Feil-Seifer]

I finally gave this a try and it did not work for me. Here is a
rewritten version to get joint bound info from the URDF file and to
get joint names from the urdf description as well. I've attached a
revised version.

I tried this on both the PR2 and the Bandit model, and I kept getting
and "ik solver fail" error. This would occur even if I gave the
robot's current end-effector position. Attached are two files, on is a
revised goto_cart.cpp and another is a file that sends a test message.
To run on the pr2 model in gazebo:

./goto_cart _root_name:="l_shoulder_pan_link" _tip_name:="l_wrist_roll_link"
./cmd_ik

Are you using a version of kdl newer than what is being used in
cturtle? Have I messed something up with updating your file?

On Sat, Jul 17, 2010 at 11:37 AM, Morgan Quigley
<mquigley at cs.stanford.edu> wrote:
> Hi Dave,
>
> The Orocos KDL library is great. I just switched to it last week; my
> code is pretty ugly, but it's using the KDL::ChainIkSolverPos_NR_JL
> class, which has joint limits:
>
> http://stanford-ros-pkg.googlecode.com/svn/trunk/openarms/control/goto_cart.cpp
>
> The ik_tool() function is what you're after. You set the joint limits
> when you construct the ChainIkSolverPos_NR_JL object; search for
> "ik_solver_pos" in that .cpp file to see the exact syntax.
>
> (sorry about all the commented code... it's a work in progress)
>
> HTH,
> Morgan
>
>
> On Sat, Jul 17, 2010 at 10:43 AM, David Feil-Seifer
> <david.feilseifer at gmail.com> wrote:
>> I am trying to replicate the IK-functionality of pr2_arm_navigation
>> for our humanoid robot, Bandit. I have attached a xacro file for it's
>> arm. I have it rendering correctly, and am able to have it mimic the
>> movements of a real Bandit with joint_states_publisher and a
>> /joint_states message. I seem to have correctly ported
>> pr2_arm_ik_solver and pr2_arm_kinematics by simply changing all 7's to
>> 6's and changing the names of the root and tip links
>> (bandit_torso_link and left/right_hand_link). However, I'm having
>> trouble with pr2_arm_ik.cpp. Clearly, the math here was meant for a
>> 7-DOF arm, and I don't really know what algorithm is being used here,
>> so I'm having trouble translating that to a 6-DOF arm. I have figured
>> out that in the init function, that I needed to change the
>> link_offsets for the shoulder_upperarm_offset, elbow_wrist offset, and
>> upperarm_elbow_offset values. Those are now correct. I am just having
>> trouble making computeIKShoulderPan and computeIKShoulderRoll to a 6
>> joint arm. Can anyone give me some guidance on how to proceed?
>>
>> I did look at the KDL examples on their website, but they were pretty
>> vague about creating an IK solver with joint limits.
>>
>> Thanks for your help.
>> -Dave
>>
>> _______________________________________________
>> ros-users mailing list
>> ros-users at code.ros.org
>> https://code.ros.org/mailman/listinfo/ros-users
>>
>>
> _______________________________________________
> ros-users mailing list
> ros-users at code.ros.org
> https://code.ros.org/mailman/listinfo/ros-users
>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: goto_cart.cpp
Type: text/x-c++src
Size: 8959 bytes
Desc: not available
URL: <http://lists.ros.org/pipermail/ros-users/attachments/20100720/1b6d1585/attachment-0010.cpp>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: cmd_ik.cpp
Type: text/x-c++src
Size: 1019 bytes
Desc: not available
URL: <http://lists.ros.org/pipermail/ros-users/attachments/20100720/1b6d1585/attachment-0011.cpp>