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DRC Robot splits - possible friction and joint torque issue

asked 2012-12-17 13:55:46 -0600

GoRobotGo gravatar image

updated 2013-07-23 17:22:14 -0600

hsu gravatar image

Interesting results come from running the following line in traj_data.yaml using the example at whole body trajectory tutorial

  - [0.1, "0 0.1 0 0 0 0                   0 -0.1 0 0 0 0                 0    0   0 0   0 0    0    0   0  0   0 0    0 0 0 0" ]

This moves the left and right leg_mhx joints outward. After the motion is completed the feet continue to slowly slip along the ground until the joint motion limit is hit. Effectively the robot does the splits. This brings up two issues:

  1. It seems like the friction between the feet and ground should be sufficient to prevent this from happening.
  2. It seems like the leg_mhx joints should have sufficient torque to prevent this from happening.

This doesn't seem like a critical issue. I wanted to bring it up so it could be considered as the simulator development moves forward.

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answered 2013-07-24 08:54:34 -0600

nkoenig gravatar image

This was a comment from hsu that I move to an answer:

Try turning up number of inner iterations in the physics constraints parameters and see if slip is reduced/eliminated. Alternatively, try turning up P-gains on the leg_mhx joints to add torque to prevent slip, but I am not sure if you'll run into controller stability issues.

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Asked: 2012-12-17 13:55:46 -0600

Seen: 625 times

Last updated: Jul 24 '13