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I am currently working on a project to make a four-wheeled differential drive robot using 4 VESCs with ROS2 as the means of communication. Two vesc will be masters and the rest two will be slaves. I found out the vesc_hw_interface in [sbgisen][1] which I used for one VESC and it was okay. but when I tried to use two of it with some modification in the ros2_control_xacro by including two hardware and two joints, there was an error like the following

Invalid checksum
[ros2_control_node-1] [ERROR] [1693755709.123338959] 
[VescHwInterface]: Out-of-sync with VESC, discarding 49 bytes.
[ros2_control_node-1] [ERROR] [1693755709.128419540] 
[VescHwInterface]: Invalid end-of-frame character
[ros2_control_node-1] [ERROR] [1693755709.128438065] 
[VescHwInterface]: Invalid payload length
[ros2_control_node-1] [ERROR] [1693755709.128448735] 
[VescHwInterface]: Out-of-sync with VESC, discarding 21 bytes.
[ros2_control_node-1] [ERROR] [1693755709.163161253] 
[VescHwInterface]: Invalid end-of-frame character
[ros2_control_node-1] [ERROR] [1693755709.163192823] 
[VescHwInterface]: Out-of-sync with VESC, discarding 8 bytes.
[ros2_control_node-1] [ERROR] [1693755709.203127802] 
[VescHwInterface]: Invalid end-of-frame character
[ros2_control_node-1] [ERROR] [1693755709.203179020] 
[VescHwInterface]: Out-of-sync with VESC, unknown data leading 
valid frame. Discarding 1 bytes

I tried using the controllers (joint_state_broadcaster and velocity_controller), which worked with a single VESC, launching it with two VESCs with two ros2_control tags including two separate actuator-type hardware. I also tried to change the velocity controller to diff_drive_controller and tried the same thing with two VESCs. But it fails every time. I am attaching the screenshot of my configuration and xacro file. Any suggestion will be really helpful.

This is the config file for the controller manager and xacro file for the resource manager that works with one vesc.

controller_manager:
  ros__parameters:
    update_rate: 100 # Hz
    joint_state_broadcaster:
      type: joint_state_broadcaster/JointStateBroadcaster
    joint_velocity_controller:
      type: velocity_controllers/JointGroupVelocityController

# Publish all joint states -----------------------------------
joint_state_broadcaster:
  ros__parameters:
    publish_rate: 100

joint_velocity_controller:
  ros__parameters:
    joints:
      - left_wheel_joint
    publish_rate: 100

The xacro that works with one vesc

<?xml version="1.0" encoding="UTF-8"?>
<robot xmlns:xacro="http://www.ros.org/wiki/xacro">
  <ros2_control name="vesc" type="actuator">
    <hardware>
      <plugin>vesc_hw_interface/VescHwInterface</plugin>
      <param name="port">/dev/ttyACM1</param>
      <param name="gear_ratio">1</param>
      <param name="command_mode">velocity_duty</param>
      <param name="joint_type">continuous</param>
      <param name="num_hall_sensors">3</param>
      <param name="num_rotor_poles">20</param>
      <param name="motor/Kp">0.1</param>
      <param name="motor/Ki">0.01</param>
      <param name="motor/Kd">0.02</param>
      <param name="motor/i_clamp">1.0</param>
      <param name="motor/duty_limiter">1.0</param>
      <param name="motor/antiwindup">true</param>
      <param name="motor/control_rate">100.0</param>
      <param name="motor/enable_smooth_diff">true</param>
      <param name="motor/smooth_diff/max_sample_sec">0.2</param>
      <param name="motor/smooth_diff/max_smooth_step">10</param>
      
      
    </hardware>
    <joint name="right_wheel_joint">
      <!-- <command_interface name="position">
        <param name="min">-1</param>
        <param name="max">1</param>
      </command_interface> -->
      <command_interface name="velocity">
        <param name="min">-1</param>
        <param name="max">1</param>
      </command_interface>
      <!-- <command_interface name="effort">
        <param name="min">-1</param>
        <param name="max">1</param>
      </command_interface> -->
      <state_interface name="position"/>
      <state_interface name="velocity"/>
      <!-- <state_interface name="effort"/> -->
    </joint>
 


  </ros2_control>
</robot>

And these are what I tried.

Config file for controller manager with diff_drive_controller and joint_state_broadcaster

controller_manager:
  ros__parameters:
    update_rate: 100  # Hz

    joint_state_broadcaster:
      type: joint_state_broadcaster/JointStateBroadcaster

    diffbot_base_controller:
      type: diff_drive_controller/DiffDriveController

diffbot_base_controller:
  ros__parameters:
    left_wheel_names: ["left_wheel_joint"]
    right_wheel_names: ["right_wheel_joint"]

    wheel_separation: 0.221
    #wheels_per_side: 1  # actually 2, but both are controlled by 1 signal
    wheel_radius: 0.045

    wheel_separation_multiplier: 1.0
    left_wheel_radius_multiplier: 1.0
    right_wheel_radius_multiplier: 1.0

    publish_rate: 50.0
    odom_frame_id: odom
    base_frame_id: base_link
    pose_covariance_diagonal : [0.001, 0.001, 0.001, 0.001, 0.001, 0.01]
    twist_covariance_diagonal: [0.001, 0.001, 0.001, 0.001, 0.001, 0.01]

    open_loop: false
    enable_odom_tf: true

    cmd_vel_timeout: 0.5
    #publish_limited_velocity: true
    use_stamped_vel: false
    #velocity_rolling_window_size: 10

    # Velocity and acceleration limits
    # Whenever a min_* is unspecified, default to -max_*
    linear.x.has_velocity_limits: true
    linear.x.has_acceleration_limits: true
    linear.x.has_jerk_limits: false
    linear.x.max_velocity: 1.0
    linear.x.min_velocity: -1.0
    linear.x.max_acceleration: 1.0
    linear.x.max_jerk: 0.0
    linear.x.min_jerk: 0.0

    angular.z.has_velocity_limits: true
    angular.z.has_acceleration_limits: true
    angular.z.has_jerk_limits: false
    angular.z.max_velocity: 1.0
    angular.z.min_velocity: -1.0
    angular.z.max_acceleration: 1.0
    angular.z.min_acceleration: -1.0
    angular.z.max_jerk: 0.0
    angular.z.min_jerk: 0.0

joint_state_broadcaster:
  ros__parameters:
    publish_rate: 100

Xacro file for the resource manager with two vescs as actuators.

<?xml version="1.0" encoding="UTF-8"?>
<robot xmlns:xacro="http://www.ros.org/wiki/xacro">
  <ros2_control name="VESCLeft" type="actuator">
    <hardware>
      <plugin>vesc_hw_interface/VescHwInterface</plugin>
      <param name="port">/dev/ttyACM0</param>
      <param name="gear_ratio">1</param>
      <param name="command_mode">velocity</param>
      <param name="joint_type">continuous</param>
      <param name="num_hall_sensors">3</param>
      <param name="num_rotor_poles">20</param>
      <param name="motor/Kp">0.1</param>
      <param name="motor/Ki">0.01</param>
      <param name="motor/Kd">0.02</param>
      <param name="motor/i_clamp">1.0</param>
      <param name="motor/duty_limiter">1.0</param>
      <param name="motor/antiwindup">true</param>
      <param name="motor/control_rate">50</param>
      <param name="motor/enable_smooth_diff">true</param>
      <param name="motor/smooth_diff/max_sample_sec">0.2</param>
      <param name="motor/smooth_diff/max_smooth_step">10</param>
   
      
    </hardware>
    <joint name="left_wheel_joint">
      <command_interface name="velocity">
        <param name="min">-5</param>
        <param name="max">5</param>
      </command_interface>

      <state_interface name="position"/>
      <state_interface name="velocity"/>
    </joint>



  </ros2_control>

  <ros2_control name="VESCRight" type="actuator">
    <hardware>
      <plugin>vesc_hw_interface/VescHwInterface</plugin>
      <param name="port">/dev/ttyACM1</param>
      <param name="gear_ratio">1</param>
      <param name="command_mode">velocity</param>
      <param name="joint_type">continuous</param>
      <param name="num_hall_sensors">3</param>
      <param name="num_rotor_poles">20</param>
      <param name="motor/Kp">0.1</param>
      <param name="motor/Ki">0.01</param>
      <param name="motor/Kd">0.02</param>
      <param name="motor/i_clamp">1.0</param>
      <param name="motor/duty_limiter">1.0</param>
      <param name="motor/antiwindup">true</param>
      <param name="motor/control_rate">50</param>
      <param name="motor/enable_smooth_diff">true</param>
      <param name="motor/smooth_diff/max_sample_sec">0.2</param>
      <param name="motor/smooth_diff/max_smooth_step">10</param>
      
    </hardware>
    
    <joint name="right_wheel_joint">
      <command_interface name="velocity">
        <param name="min">-5</param>
        <param name="max">5</param>
      </command_interface>
      <state_interface name="position"/>
      <state_interface name="velocity"/>

    </joint>



  </ros2_control>
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    $\begingroup$ please don't post pictures of your code but add the code as formatted text. $\endgroup$
    – Christoph Froehlich
    Sep 4 at 14:40
  • $\begingroup$ ... and format the error using code formatting as well. Block quote formatting has rendered the error almost unreadable. $\endgroup$
    – Greenonline
    Sep 4 at 16:41
  • $\begingroup$ Sorry for the inconvenience. It is my first time posting in a forum and I did not have that much idea of code formatting and block formatting. I edited my post as you suggested and it surely looks a lot better for anyone to go through and answer. $\endgroup$
    – Mohammad Tariqul Islam
    Sep 5 at 18:55

1 Answer 1

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I don't see any error in your ros2_control configuration at the first glance. The error messages do not come from the ros2_control framework but from the hw_interface for the VESCs. Maybe you have to ask in their repository, if none of the developers is around here.

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