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Robot twitches in simulation

asked 2013-10-07 12:00:55 -0600

mortonjt gravatar image

updated 2013-12-14 14:26:03 -0600

I'm been trying to simulate differential drive on my robot and I'm having trouble making the robot move smoothly. I've put in all of the friction coefficients and tried to apply torque to the wheels, but my robot just twitches. If I apply commands to one wheel, the robot will turn in a 360, but it'll take several minutes to do so.

I specified the motors as follows

  <transmission name="wheel_left_tran">
    <type>transmission_interface/SimpleTransmission</type>
    <joint name="to_wheel_left"/>
    <actuator name="motor1">
      <hardwareInterface>EffortJointInterface</hardwareInterface>
      <mechanicalReduction>1</mechanicalReduction>
      <motorTorqueConstant>10</motorTorqueConstant>
    </actuator>
  </transmission>

  <transmission name="wheel_right_tran">
    <type>transmission_interface/SimpleTransmission</type>
    <joint name="to_wheel_right"/>
    <actuator name="motor2">
      <hardwareInterface>EffortJointInterface</hardwareInterface>
      <mechanicalReduction>1</mechanicalReduction>
      <motorTorqueConstant>10</motorTorqueConstant>
    </actuator>
  </transmission>

I haven't built the differiential drive plugin, so I'm using the following plugin to validate the physical characteristic of my robot

  <gazebo>
    <plugin name="gazebo_ros_control" filename="libgazebo_ros_control.so">
      <robotNamespace>/redblade</robotNamespace>
      <alwaysOn>true</alwaysOn>
      <updateRate>20</updateRate>
    </plugin>
  </gazebo>

Has anyone seen this problem before? Any thoughts would be greatly appreciated!

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answered 2013-10-10 11:11:54 -0600

nkoenig gravatar image

Your inertia values seem strange, everything has a mass of 1Kg and 1 for each of the diagonal elements in inertia matrix.

There are also many links that have visuals, inertia, but no collision. That may be what you want, but it's not very common.

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Comments

Okay. That makes makes complete sense. I modelled the inertia matrix for the wheels as a cylinders and it seems to have fixed the motion problem. Thank you so much for taking the time to look at my code and help me fix this problem!

mortonjt gravatar imagemortonjt ( 2013-10-10 16:54:07 -0600 )edit
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Asked: 2013-10-07 12:00:55 -0600

Seen: 374 times

Last updated: Dec 14 '13