Twisting continuous joint when velocity increases

asked 2017-06-02 07:41:29 -0500

blevesque gravatar image

Hi all, I simulate a robot with two wheels and when target of velocity joint is "too high", joint twists. Here are my joint description :

<joint name="bottom_${side}_engine_to_${side}_wheel" type="continuous">
  <origin xyz="0.0 0.0 ${-BOTTOM_ENGINE_HEIGHT/2.0}" />
  <parent link="bottom_${side}_engine" />
  <child link="${side}_wheel" />
  <axis xyz="0 -1 0" />
  <dynamics damping="0.1" />
  <limit effort="10000000" velocity="100000" />
  <joint_properties damping="0.0" friction="0.0" />
</joint>

Joint controller :

<transmission name="left_wheel_traction">
  <type>transmission_interface/SimpleTransmission</type>
  <joint name="bottom_left_engine_to_left_wheel">
    <hardwareInterface>hardware_interface/VelocityJointInterface</hardwareInterface>
  </joint>
  <actuator name="motor4">
    <hardwareInterface>hardware_interface/VelocityJointInterface</hardwareInterface>
    <mechanicalReduction>1</mechanicalReduction>
  </actuator>
</transmission>

left_wheel_traction_controller:
    type: velocity_controllers/JointVelocityController
    joint: bottom_left_engine_to_left_wheel
    pid: {p: 100.0, i: 0.01, d: 10.0}

Can someone help me ? I don't understand why joint twists, it is only a joint between a motor and a wheel. Thanks for your time

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