Controllers

This help page describes the different controllers available for the ur_robot_driver. This should help users finding the right controller for their specific use case.

Available Controllers

• Position and Velocity Control
  • Trajectory-based Control
  • Motion Primitives
  • Streaming Control
  • Controller Compatibility
• Force and Torque Control
  • Joint Torque Control
  • Force Mode Controller
  • Freedrive Mode Controller
  • Force/Torque Sensing
  • Controller Compatibility
  • Examples
• Utility Controllers
  • joint_state_broadcaster
  • speed_scaling_state_broadcaster
  • io_and_status_controller
  • tool_contact_controller
  • tcp_pose_broadcaster
  • ur_configuration_controller

How do controllers get loaded and started?

As this driver uses ros2_control all controllers are managed by the controller_manager. During startup, a default set of running controllers is loaded and activated, another set is loaded in inactive mode. Inactive controllers won’t be usable right away, but they need to be activated individually.

Controllers that are actually writing to some command interfaces (e.g. joint positions) will claim those interfaces. Only one controller claiming a certain interface can be active at one point.

Controllers can be switched either through the controller_manager’s service calls, through the rqt_controller_manager gui or through the ros2 control verb from the ros-${ROS_DISTRO}-ros2controlcli package.

For example, to switch from the default scaled_joint_trajectory_controller to the forward_position_controller you can call

$ ros2 control switch_controllers --deactivate scaled_joint_trajectory_controller \
  --activate forward_position_controller
[INFO 2024-09-23 20:32:04.373] [_ros2cli_1207798]: waiting for service /controller_manager/switch_controller to become available...
Successfully switched controllers

Where are controllers defined?

Controllers are defined in the config/ur_controllers.yaml file.