Robot falls down with custom controller

[fafux]

Environment

• OS Version: Ubuntu 24.04
• ROS2 version: jazzy
• Binary build: ros-jazzy-gz-ros2-control : 1.2.3-1noble.20240611.144029

Description

• Launching gz_sim.launch.py and create to spawn the urdf, parsing the xacro in which <plugin filename="gz_ros2_control-system" name="gz_ros2_control::GazeboSimROS2ControlPlugin"> and <plugin>gz_ros2_control/GazeboSimSystem</plugin> are contained, I am able to spawn the robot and start the simulation. Nevertheless, launching a custom controller, which is passed to the plugin through the yaml file, does not command the joints. Specifically, the controller sets the command interface for the joint velocities without obtaining any corresponding velocity in Gazebo. No errors are given. While the simulation is running, with the command ros2 control list_controllers I obtain the following output:

  cartesian_velocity_controller[robot_controllers/CartesianVelocityController] active    
  joint_state_broadcaster[joint_state_broadcaster/JointStateBroadcaster] active 

  With the command ros2 control list_hardware_interfaces:

  command interfaces
  joint_1/position [available] [unclaimed]
  joint_1/velocity [available] [claimed]
  joint_2/position [available] [unclaimed]
  joint_2/velocity [available] [claimed]
  joint_3/position [available] [unclaimed]
  joint_3/velocity [available] [claimed]
  joint_4/position [available] [unclaimed]
  joint_4/velocity [available] [claimed]
  joint_5/position [available] [unclaimed]
  joint_5/velocity [available] [claimed]
  joint_6/position [available] [unclaimed]
  joint_6/velocity [available] [claimed]
  state interfaces
  joint_1/position
  joint_1/velocity
  joint_2/position
  joint_2/velocity
  joint_3/position
  joint_3/velocity
  joint_4/position
  joint_4/velocity
  joint_5/position
  joint_5/velocity
  joint_6/position
  joint_6/velocity

  The robot in any case falls down in simulation due to the gravity. How can I solve this problem? Thanks.

[christophfroehlich]

Is the controller sending commands to the plugin? Do you have the same behavior if you just use a forward_command_controller like velocity_controllers/JointGroupVelocityController?

[fafux]

Yes. The controller is sending commands to the plugin through the command interface (in this case velocity). With velocity_controllers/JointGroupVelocityController I have the same behaviour.

[fafux]

There was a problem in the xacro definition of the robot. The joints property was defined as <limit lower="-1.658" upper="2.705" effort="0" velocity="3.054" />. The problem is the effort limit that was 0.