ROS1 Common Problems and Solutions

When using ROS1 to control the MyCobot Pro 450, you may encounter some common problems. Below is a list of common errors and their corresponding solutions for quick troubleshooting.

1 Environment-Related Issues

• Issue 1: Running ros2 launch results in the error package 'mycobot_pro_450' not found
  • Cause: The ROS workspace was not compiled correctly or the environment variables were not loaded
  • Solution:

    cd ~/colcon_ws
    colcon build
    source install/setup.bash
    

2 Network Communication Issues

• Issue 1: Error: "Trying to connect to real MyCobot Pro450... Timeout"

  • Cause: The PC and robot are not on the same network segment, or the IP address is incorrectly set

  • Solution:

    • Confirm that the robot's default IP address is 192.168.0.232

    • Set the PC network card to the same network segment, for example, 192.168.0.100

    • Test connectivity:

      ping 192.168.0.232
      

3 Python API/Library Issues

• Issue 1: Runtime Error ModuleNotFoundError: No module named 'pymycobot'

  • Cause: pymycobot is not installed in the Python environment

  • Solution:

    pip3 install pymycobot
    

  • Issue 2: Runtime Error ImportError: cannot import name 'Pro450Client' from 'pymycobot'

    • Cause: pymycobot version is too low

    • Solution:

      pip install -U pymycobot
      

  • Issue 3: Runtime Error RuntimeError: The version of the pymycobot library must be greater than 3.9.9 or higher. The current version is 3.9.7. Please upgrade the library version.

    • Cause: Pymycobot version is too low

    • Solution:

      pip install -U pymycobot
      

      Note: Version must be greater than 4.0.0

4 ROS Node Operation Issues

• Problem 1: Model not displayed after opening in rviz

  • Cause 1: robot_description not loaded correctly

  • Solution:

    • Check that the ros2 launch command is complete

    • In the terminal, enter:

      ros2 param list | grep robot_description
      

      If you see the /robot_description parameter, the model has been loaded.

    • Please check that the joint_state_publisher and robot_state_publisher are running properly.

    • Use the ros2 topic list command to confirm the existence of /joint_states, /tf, and /tf_static. These are necessary topics for model display and motion.

• Problem 2: After opening rviz, the model is incomplete, and the terminal continuously outputs a warning message similar to: Warning [Invalid frame ID "base" passed to canTransform argument target frame frame does not exist rviz2-2] rviz2-2 at line 133 in /tmp/binarydeb/ros-foxy-tf2-0.13.13/src/buffer core.cpp

  • Cause 1: Robot communication is abnormal and angle coordinates cannot be read normally.

  • Solution:

    • Is joint_states being published (a message will be printed)?
    • In the terminal, enter:

    rostopic echo -n 5 /joint_states
    

    If /joint_states does not output anything, it is likely that the robot communication or the mycobot service is not receiving data.

  • Please check that joint_state_publisher and robot_state_publisher are running properly. - Use the ros2 topic list command to confirm the existence of /joint_states, /tf, and /tf_static. These are necessary topics for model display and motion.

  • Check the robot's communication status. For details, see Python Exception Handling

  • Check whether the robot can read angles and coordinates normally.

    from pymycobot import Pro450Client
    mc = Pro450Client('192.168.0.232', 4500)
    
    if mc.is_power_on() != 1:
    mc.power_on()
    
    print(mc.get_angles(), mc.get_coords())
    

• Problem 3: Error message: [WARN]: Coordinate control disabled. Please press '2' first.

  • Solution: First enter 2 on the keyboard control interface to return the robot to its starting point, then resume coordinate control