Robot Rolls and Flies Unexpectedly When Publishing cmd_vel with VelocityControl Plugin

[MALIKMUHAMMADWAQAR]

Hello,
I'm working on simulating a 4-wheel robot in Ignition Gazebo using the [X1 Config 5 model from Fuel] https://app.gazebosim.org/chumbus/fuel/models/X1%20Config%205 which I converted to URDF format.

I attached the following plugin to the robot to control its velocity:
<plugin filename="ignition-gazebo-velocity-control-system" name="ignition::gazebo::systems::VelocityControl"> <topic>cmd_vel</topic> </plugin>
When I publish velocity commands to the /cmd_vel topic (especially with an angular velocity), instead of rotating in place, the entire robot body starts to move forward and eventually rolls. Additionally, when the terrain is slightly sloped, the robot doesn't move down naturally — it instead lifts off or flies upwards.

I've attached the URDF file for reference.
I would really appreciate any help in identifying the cause of this behavior.

our_robot.txt

[arjo129]

Additionally, when the terrain is slightly sloped, the robot doesn't move down naturally — it instead lifts off or flies upwards.

velocity-control-system bypasses physics and sets a global velocity in the global frame.

For your usecase you probably want the diff drive plugin not the velocity control plugin:

[MALIKMUHAMMADWAQAR]

Thank you for help @arjo129. I got it.