Velocity and Position command interfaces don't work when Effort command interface exist

[BarisYazici]

When I add the effort command interface to the test_cart_velocity.xacro.urdf example, the velocity example stops working. I modified the example to reproduce the bug https://github.com/BarisYazici/gz_ros2_control/blob/humble/ign_ros2_control_demos/urdf/test_cart_velocity.xacro.urdf.

[christophfroehlich]

This might be a limit of ignition::gazebo::v6::EntityComponentManager.

But why would someone need velocity and effort at the same time? What should the physics engine do then?

[BarisYazici]

They were not claimed by the controller at the same time. Effort interface was just available in the robot itself that triggered the bug.

[fbottarel]

@BarisYazici I've been stuck on this for a while, I want my simulated robot joints to have both an effort and velocity command interface since that reflects the real robot. Honestly I couldn't solve it so I made different URDFs and I load either one or the other according to how I want to control the joints.

[christophfroehlich]

They were not claimed by the controller at the same time. Effort interface was just available in the robot itself that triggered the bug.

Ah I see. This shouldn't be a problem, maybe there is a bug in the logic of the perform_command_mode_switch. Maybe someone here could have a look into this?

[BarisYazici]

@BarisYazici I've been stuck on this for a while, I want my simulated robot joints to have both an effort and velocity command interface since that reflects the real robot. Honestly I couldn't solve it so I made different URDFs and I load either one or the other according to how I want to control the joints.

Our workaround is also basically the same. Could take a look to perform_command_mode_switch when I find time @christophfroehlich