0
$\begingroup$

Rosanswers logo

Hi! I had a problem with moveit's computeVariableVelocity, which I tracked down to a weird Jacobian matrix in my model. The robot has X, Y and Z prismatic joints, then a Z revolute. But with the joint-states all zeroed out, I'm getting a jacobian

  1.304  0.31889  0.41454        0
  -0.03  0.97173 -0.06256    0.575
0.19219  0.23349  2.48029        0
      0        0        0        0
      0        0        0        0
      0        0        0        1

which looks very wrong in a bunch of ways (not least, 1m of Z joint movement turns into 2.4m of worldspace Z!). Only the final revolute joint looks right.

Stepping into getJacobian, things seem to go wrong around line 1161:

joint_transform = reference_transform * getGlobalLinkTransform(link);
joint_axis = joint_transform * static_cast<const robot_model::PrismaticJointModel*>(pjm)->getAxis();

When I hit this line, getGlobalLinkTransform returns a valid matrix that includes translation. There's nothing in reference transform to cancel this out, so prismatic axis gets rotated and translated, and joint_axis ends up totally wonky.

Is there something wrong with my RobotModel here? Am I misunderstandingt the Jacobian?


Originally posted by Mike Ferenduros on ROS Answers with karma: 16 on 2018-12-12

Post score: 0


Original comments

Comment by gvdhoorn on 2018-12-12:
If you feel this is an issue with MoveIt, I would suggest to report it over at ros-planning/moveit/issues.

If you do, please try to include a reproducable example or nr of steps. That will greatly simplify debugging.

$\endgroup$

1 Answer 1

0
$\begingroup$

Rosanswers logo

Turns out it was indeed a moveit bug, fixed last month. https://github.com/ros-planning/moveit/commit/ece11fe5ebbfb0f9caeb112c0adf9536bbb915ce


Originally posted by Mike Ferenduros with karma: 16 on 2018-12-12

This answer was ACCEPTED on the original site

Post score: 0


Original comments

Comment by gvdhoorn on 2018-12-12:
Thanks for reporting back.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.