dynamixel_control

The ros2_control implementation for any kind of ROBOTIS Dynamixel robots.

• dynamixel_hardware: the SystemInterface implementation for the multiple ROBOTIS Dynamixel servos.
• open_manipulator_x_description: the reference implementation of the ros2_control robot using ROBOTIS OpenManipulator-X.

The dynamixel_hardware package is hopefully compatible any configuration of ROBOTIS Dynamixel servos thanks to the ros2_control’s flexible architecture.

Set up

First install ROS 2 Humble on Ubuntu 22.04. Then follow the instruction below.

$ source /opt/ros/humble/setup.bash
$ mkdir -p ~/ros/humble && cd ~/ros/humble
$ git clone https://github.com/youtalk/dynamixel_control.git src
$ vcs import src < src/dynamixel_control.repos
$ rosdep install --from-paths src --ignore-src -r -y
$ colcon build --symlink-install --cmake-args -DCMAKE_EXPORT_COMPILE_COMMANDS=ON
$ . install/setup.bash

Demo with real ROBOTIS OpenManipulator-X

Configure Dynamixel motor parameters

Update the usb_port, baud_rate, and joint_ids parameters on open_manipulator_x_description/urdf/open_manipulator_x.ros2_control.xacro to correctly communicate with Dynamixel motors. The use_dummy parameter is required if you don’t have a real OpenManipulator-X.

Note that joint_ids parameters must be splited by ,.

<hardware>
  <plugin>dynamixel_hardware/DynamixelHardware</plugin>
  <param name="usb_port">/dev/ttyUSB0</param>
  <param name="baud_rate">1000000</param>
  <!-- <param name="use_dummy">true</param> -->
</hardware>

• Terminal 1

Launch the ros2_control manager for the OpenManipulator-X.

$ ros2 launch open_manipulator_x_description open_manipulator_x.launch.py

• Terminal 2

Start the joint_trajectory_controller and send a /joint_trajectory_controller/follow_joint_trajectory goal to move the OpenManipulator-X.

$ ros2 control switch_controllers --activate joint_state_broadcaster --activate joint_trajectory_controller --deactivate velocity_controller
$ ros2 action send_goal /joint_trajectory_controller/follow_joint_trajectory control_msgs/action/FollowJointTrajectory -f "{
  trajectory: {
    joint_names: [joint1, joint2, joint3, joint4, gripper],
    points: [
      { positions: [0.1, 0.1, 0.1, 0.1, 0], time_from_start: { sec: 2 } },
      { positions: [-0.1, -0.1, -0.1, -0.1, 0], time_from_start: { sec: 4 } },
      { positions: [0, 0, 0, 0, 0], time_from_start: { sec: 6 } }
    ]
  }
}"

If you would like to use the velocity control instead, switch to the velocity_controller and publish a /velocity_controller/commands message to move the OpenManipulator-X.

$ ros2 control switch_controllers --activate joint_state_broadcaster --deactivate joint_trajectory_controller --activate velocity_controller
$ ros2 topic pub /velocity_controller/commands std_msgs/msg/Float64MultiArray "data: [0.1, 0.1, 0.1, 0.1, 0]"

Demo with dummy ROBOTIS OpenManipulator-X

The use_dummy parameter is required if you use the dummy OpenManipulator-X.

diff --git a/open_manipulator_x_description/urdf/open_manipulator_x.ros2_control.xacro b/open_manipulator_x_description/urdf/open_manipulator_x.ros2_control.xacro
index c6cdb74..111846d 100644
--- a/open_manipulator_x_description/urdf/open_manipulator_x.ros2_control.xacro
+++ b/open_manipulator_x_description/urdf/open_manipulator_x.ros2_control.xacro
@@ -9,7 +9,7 @@
         <param name="usb_port">/dev/ttyUSB0</param>
         <param name="baud_rate">1000000</param>
-        <!-- <param name="use_dummy">true</param> -->
+        <param name="use_dummy">true</param>
       </hardware>
       <joint name="joint1">
         <param name="id">11</param>

Then follow the same instruction of the real robot one.

Note that the dummy implementation has no interpolation so far. If you sent a joint message, the robot would move directly to the joints without interpolation.