Joint and sensor data spikes

asked 2018-05-29 11:14:21 -0500

jlack gravatar image

I've been having trouble with spikes in force/torque sensor data. There are spikes in the joint velocity data also, but I haven't bothered too much about them until now when i'm trying to wrap control loops around force/torque sensor data. See the attached and labeled screenshot of some plots of the x/y/z forces from a force/torque sensor as well as a joint velocity signal from one of the joints.

Below are a few notes about my physics config that may be helpful,

  • physics iterations: 100
  • sor: 1.0
  • don't believe there are any self collisions happening
  • have tried raising iterations arbitrarily high and it doesn't help
  • have tuned sor and it doesn't help
  • all joints have implicit spring damper at 1

I have tweaked link inertia/mass to see if it's a poorly conditioned system for the physics and nothing i've done has had much of an affect.

If I thought I was just dealing with noise I would just put a filter on it and move on, but these spikes don't look like noise to me and i'm afraid to just ignore them and bandaid it with a filter.

One more note that may be helpful, i'm doing velocity control via the joint->SetVelocity call from the joint API.

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As a further test I remove my gazebo plugins call to joint->SetVelocity so the arms now just go slack and hang down and here's the same plot in that configuration,

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The large spikes are still there in the force/torque sensor data, but the joint velocity is now smooth with no spikes.

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The version of gazebo i'm using is 7.12 FYI

jlack gravatar imagejlack ( 2018-05-29 11:17:24 -0500 )edit

See some explanation of why I think this is happening here:

jlack gravatar imagejlack ( 2018-07-31 13:36:46 -0500 )edit