How to properly configure wheel links in gazebo and ros urdf to provide proper propulsion?

asked 2016-09-15 03:38:18 -0500

Mahmoud Abdul Galil gravatar image

Hi, My question is regarding configuring the properties of wheel links and the associated joints (motors). I'm building a four wheeled differential car, and i finished my urdf seamlessly, and connected ROS_control too, everything is fine except that the wheels don't provide proper propulsion for the vehicle, so i thought that the properties might not be configured properly. I started messing around to see if i can get it working, but no luck.

<gazebo reference="${fb}_${lr}_wheel">
  <mu1 value="100.0"/>
  <mu2 value="1.0"/>
  <fdir1 value="1 0 0"/>
  <material>Gazebo/Black</material>
  <turnGravityOff>false</turnGravityOff>
  <dampingFactor>0.01</dampingFactor>
</gazebo>

<joint name="${fb}_${lr}_wheel_joint" type="continuous">
  <parent link="${parent}"/>
  <child link="${fb}_${lr}_wheel"/>
  <origin xyz="${translateX} ${translateY} ${base_z_origin_to_wheel_origin}" rpy="0 0 0" />
  <axis xyz="0 1 0" rpy="0  0" />
  <limit effort="100" velocity="100"/>
</joint>

<!-- Transmission is important to link the joints and the controller -->
<transmission name="${fb}_${lr}_wheel_joint_trans">
  <type>transmission_interface/SimpleTransmission</type>
  <joint name="${fb}_${lr}_wheel_joint">
       <hardwareInterface>EffortJointInterface</hardwareInterface>
  </joint>
  <actuator name="${fb}_${lr}_wheel_joint_motor">
    <hardwareInterface>EffortJointInterface</hardwareInterface>
    <mechanicalReduction>1</mechanicalReduction>
  </actuator>
</transmission>

If i move the vehicle forward or backward it works like a piece of cake, but when i try to rotate it, (differentially) the wheels start to skid and the vehicle moves in a strange manner Any one can help me with this? I'd be really grateful

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Comments

Sometimes unexpected motion stems from inertial and mass properties set in the URDF. Not sure if this is the case or not.

JoshMarino gravatar imageJoshMarino ( 2016-09-17 23:32:29 -0500 )edit