Dynamixel API
The Dynamixel service allows to control Dynamixel motors.
Its type has access to all common capabilities.
Functions​
| Function name and parameters | Action | Comment |
|---|---|---|
| set_id(self, id) | Changes motor ID | This new Id will be saved by the Dynamixel motor. You have to detect motors again to make it work after this change. |
| detect(self) | Launches a motor detection | You have to run a luos detection to include or exclude new motors. |
| register(self, register, val) | Sets a Dynamixel register value. | This register only manage word size register. Use it only if you know what you do. |
| control(self) | Displays service type graphical interface | Only available using Jupyter notebook |
Variables​
| Variable name | Action | Type |
|---|---|---|
| compliant | - True: disables the motor power, you can use it to move the motor by hand. - False: Enables the motor power. | read / write: Boolean (True or False) |
| target_rot_position | Sets the target rotation position to reach in °. | read / write: Float |
| target_rot_speed | Sets the target rotation speed to reach in °/s. | read / write: Float |
| wheel_mode | Enables or disables wheel mode on motor | read / write: Boolean (True or False) |
| rot_position | Measured position of the motor in °. | read / write: Float |
| temperature | Measured temperature of the motor in °C. | read / write: Float |
| positionPid | Sets position PID used for rotation position mode and translation position mode | read / write: [float P, float I, float D] |
| power_ratio_limit | Max power limit in %. | read / write: Float |
| rot_position_limit | Min and Max rotation position limit in °. | read / write: [Float(min), Float(max)] |
ROS topics​
| Topic name | Message type | Comment |
|---|---|---|
| /dxl_1/variables/compliant/read | std_msgs/msg/Boolean | |
| /dxl_1/variables/compliant/write | std_msgs/msg/Boolean | |
| /dxl_1/variables/target_rot_position/read | std_msgs/msg/Float32 | |
| /dxl_1/variables/target_rot_position/write | std_msgs/msg/Float32 | |
| /dxl_1/variables/target_rot_speed/read | std_msgs/msg/Float32 | |
| /dxl_1/variables/target_rot_speed/write | std_msgs/msg/Float32 | |
| /dxl_1/variables/wheel_mode/read | std_msgs/msg/Boolean | |
| /dxl_1/variables/wheel_mode/write | std_msgs/msg/Boolean | |
| /dxl_1/variables/rot_position/read | std_msgs/msg/Float32 | |
| /dxl_1/variables/rot_position/write | std_msgs/msg/Float32 | |
| /dxl_1/variables/temperature/read | std_msgs/msg/Float32 | |
| /dxl_1/variables/temperature/write | std_msgs/msg/Float32 | |
| /dxl_1/variables/positionPid/read | geometry_msgs/msg/Vector3 | (x=P, y=I, z=D) |
| /dxl_1/variables/positionPid/write | geometry_msgs/msg/Vector3 | (x=P, y=I, z=D) |
| /dxl_1/variables/power_ratio_limit/read | std_msgs/msg/Float32 | |
| /dxl_1/variables/power_ratio_limit/write | std_msgs/msg/Float32 | |
| /dxl_1/variables/rot_position_limit/read | geometry_msgs/msg/Vector3 | (x=min, y=max, z= |
| /dxl_1/variables/rot_position_limit/write | geometry_msgs/msg/Vector3 | (x=min, y=max, z= |
Example code​
Example commands from ROS topics​
Plot the real time angular position with RQT plot:
ros2 run rqt_plot rqt_plot /dxl_1/variables/rot_position/read
Disable compliance:
ros2 topic pub -1 /dxl_1/variables/compliant/write std_msgs/msg/Bool data:\ false\
The motor will move to its saved target.
Switch to wheel mode and set a rotational speed target:
ros2 topic pub -1 /dxl_1/variables/wheel_mode/write std_msgs/msg/Bool data:\ true\
ros2 topic pub -1 /dxl_1/variables/target_rot_speed/write std_msgs/msg/Float32 data:\ 3.14\
The motor will move at 3.14 rad/s
Switch to position mode and set a rotational position target:
ros2 topic pub -1 /dxl_1/variables/wheel_mode/write std_msgs/msg/Bool data:\ false\
ros2 topic pub -1 /dxl_1/variables/target_rot_position/write std_msgs/msg/Float32 data:\ 0.0\
The motor will go to angle zero.
Note: If no motor is connected to the Dynamixel board, the ROS broker will display a warning message and ignore the board.