Making Joints Easier to Move

Discussion in 'Simulation' started by bhairavm, Feb 10, 2018.

  1. I'm having some trouble getting a particular joint to move without applying excessive force, which causes movement at other DoFs (which is undesirable).

    Are there any general parameters that are often changed to do this? I have attached an excerpt of some relevant code if that can help anyone shine some insight onto this problem.

    The joint of interest is wrist_roll_joint

    <body name="wrist_roll_link" pos="0 0 0">
       <inertial pos="-0.001416 -0.001547 quat="0.988073 0.0424396 -0.0351605 -
    mass="0.761692" diaginertia="0.000811657 0.000766039
    <joint name="wrist_roll_joint" pos="0 0 0" axis="0 0 1" limited="true" range="-1.92 3.67" damping="0"/>
    which I am controlling with a position controller:

    <position  kp="50" name="wrist_roll_motor" joint="wrist_roll_joint" ctrllimited="true" ctrlrange="-120 120" gear="100"/>
  2. Emo Todorov

    Emo Todorov Administrator Staff Member

    Joints become easier to move when you reduce the mass and inertia (as well as damping), or when you increase the gear ratio of your actuators.

    Note that in a multi-joint system there are always interaction forces, so joints are indeed supposed to affect each other. If you want to avoid that, you should put position controllers at each joint to keep it stable.