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[kallaspriit]

Hey, seems to be a nice library, trying to use it to control a differential drive robot but not entirely sure how to use it.

Managed to compile it and launch it with

os2 launch odrive_bringup odrive.launch.py enable_joint1:=true

Also managed to subscribe to the joint states topic.

ros2 topic echo /dynamic_joint_states

How would I go about controlling the motor velocities etc? Some documentation about using the library and some examples would help the package :)

[borongyuan]

Hi,

sorry for the missing document. We will add more examples and instructions after various tests.

The current launch file use velocity controllers by default. Of course you need enable_joint1 if you want to use both joints. The three basic controllers (position, velocity, effort) are inherited from forward_command_controller. They accept std_msgs/Float64MultiArray as input. You can try following command to set velocity of joint0.

ros2 topic pub -r 100 /joint0_velocity_controller/commands std_msgs/Float64MultiArray "layout:
  dim:
  - label: ''
    size: 1
    stride: 1
  data_offset: 0
data: [1]"

For differential drive robot, a better solution is to use diff_drive_controller. This controller handles two joints using velocity interface. It subscribes cmd_vel and publishes odometry. Please refer to DiffBot in ros2_control_demos for configurations.

[kallaspriit]

Hey, thanks for the info.

I can enable both joints by launching with ros2 launch odrive_bringup odrive.launch.py enable_joint1:=true.

I can also now control the individual wheel speeds with

• ros2 topic pub -r 100 /joint0_velocity_controller/commands std_msgs/Float64MultiArray "data: [1]"
• ros2 topic pub -r 100 /joint1_velocity_controller/commands std_msgs/Float64MultiArray "data: [-1]"

Etc. I have not used ros2_control before and I haven't quite figured out how to use the diff_drive_controller to drive the odrive through this library. Any example would be much appreciated as this is probably a pretty common use-case for the odrive board.

[kallaspriit]

Managed to implement a joystick-controlled differential drive robot using diff drive controller and this package.

Not a tutorial as such but maybe the codebase helps someone (work in progress). https://github.com/kallaspriit/rosbot/tree/main/ros

Documentation for future users would still be welcome, not trivial to figure it all out by oneself :)

[borongyuan]

documentation added