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Why does the velocity limit also limit effort?

A low <limit> velocity </limit> in the URDF also limits the effective effort a joint can apply.

I am loading robot arms from a urdf xacro with a hardwareinterface/EffortJointInterface using a roslaunch script. I am spawning an effortcontrollers/JointPositionController for each joint. I am commanding the arms "straight out":

With a high effort limit (3000) and low velocity limit (20) on each joint the arms droop: image description

With the same effort limit but a larger velocity limit (50) the arms successfully reach their goal position: image description

My best guess is that the controller outputs a large effort which leads to a large velocity, and this velocity is clipped before gravity terms are added.

i.e.

vel_limit(controller) + gravity = 0

instead of

vel_limit(controller + gravity) = "upwards motion"

Asked by bsaund on 2018-02-15 12:56:09 UTC

Comments

Is the argument paused false when you bring up the empty world?

Asked by lakehanne on 2018-09-10 08:17:11 UTC

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