Example 4: Industrial robot with integrated sensor
This example shows how a sensor can be integrated in a hardware interface of system-type: A 2D Force-Torque Sensor (FTS) is simulated by generating random sensor readings.
To check that RRBot descriptions are working properly use following launch commands
ros2 launch ros2_control_demo_example_4 view_robot.launch.py
Getting the following output in terminal is OK:
Warning: Invalid frame ID "odom" passed to canTransform argument target_frame - frame does not exist. This happens because
joint_state_publisher_guinode need some time to start. The
joint_state_publisher_guiprovides a GUI to generate a random configuration for rrbot. It is immediately displayed in RViz.
To start RRBot example open a terminal, source your ROS2-workspace and execute its launch file with
ros2 launch ros2_control_demo_example_4 rrbot_system_with_sensor.launch.py
The launch file loads and starts the robot hardware, controllers and opens RViz. In starting terminal you will see a lot of output from the hardware implementation showing its internal states. This is only of exemplary purposes and should be avoided as much as possible in a hardware interface implementation.
If you can see two orange and one yellow rectangle in in RViz everything has started properly. Still, to be sure, let’s introspect the control system before moving RRBot.
Check if the hardware interface loaded properly, by opening another terminal and executing
ros2 control list_hardware_interfaces
command interfaces joint1/position [available] [claimed] joint2/position [available] [claimed] state interfaces joint1/position joint2/position tcp_fts_sensor/force.x tcp_fts_sensor/torque.z
[claimed]by command interfaces means that a controller has access to command RRBot.
Check if controllers are running
ros2 control list_controllers
joint_state_broadcaster[joint_state_broadcaster/JointStateBroadcaster] active fts_broadcaster [force_torque_sensor_broadcaster/ForceTorqueSensorBroadcaster] active forward_position_controller[forward_command_controller/ForwardCommandController] active
If you get output from above you can send commands to Forward Command Controller, either:
Manually using ROS 2 CLI interface.
ros2 topic pub /forward_position_controller/commands std_msgs/msg/Float64MultiArray "data: - 0.5 - 0.5"
Or you can start a demo node which sends two goals every 5 seconds in a loop
ros2 launch ros2_control_demo_example_4 test_forward_position_controller.launch.py
You should now see orange and yellow blocks moving in RViz. Also, you should see changing states in the terminal where launch file is started, e.g.
[RRBotSystemWithSensorHardware]: Got command 0.50000 for joint 0! [RRBotSystemWithSensorHardware]: Got command 0.50000 for joint 1!
Access wrench data from 2D FTS via
ros2 topic echo /fts_broadcaster/wrench
shows the random generated sensor values, republished by Force Torque Sensor Broadcaster as
header: stamp: sec: 1676444704 nanosec: 332221422 frame_id: tool_link wrench: force: x: 2.946532964706421 y: .nan z: .nan torque: x: .nan y: .nan z: 4.0540995597839355
Wrench messages are not displayed properly in RViz as NaN values are not handled in RViz and FTS Broadcaster may send NaN values.
Files used for this demo
Launch file: rrbot_system_with_sensor.launch.py
Controllers yaml: rrbot_with_sensor_controllers.yaml
ros2_controlURDF tag: rrbot_system_with_sensor.ros2_control.xacro
RViz configuration: rrbot.rviz
Hardware interface plugin: rrbot_system_with_sensor.cpp
Controllers from this demo
Joint State Broadcaster(ros2_controllers repository): doc
Forward Command Controller(ros2_controllers repository): doc
Force Torque Sensor Broadcaster(ros2_controllers repository): doc