4 wheel robot differential controller

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I have designed simple a 4-wheel robot and I want to make it move. The controller below is located in "myrobot.gazebo" file and it works with 2 wheels and a caster. Is it possible to modify the controller so it can control 2 wheels on each side?

    <gazebo>
<plugin name="differential_drive_controller" filename="libgazebo_ros_diff_drive.so">
  <legacyMode>false</legacyMode>
  <alwaysOn>true</alwaysOn>
  <updateRate>20</updateRate>
  <leftJoint>left_wheel_hinge</leftJoint>
  <rightJoint>right_wheel_hinge</rightJoint>
  <wheelSeparation>0.4</wheelSeparation>
  <wheelDiameter>0.1</wheelDiameter>
  <torque>20</torque>
  <commandTopic>cmd_vel</commandTopic>
  <odometryTopic>odom</odometryTopic>
  <odometryFrame>odom</odometryFrame>
  <robotBaseFrame>chassis</robotBaseFrame>
</plugin>
</gazebo>