BotWheel Explorer ROS2 Package

Work In Progress

This package contains:

• Hardware descriptor (URDF) files for the BotWheel Explorer.
• A launch file that allows to drive the robot around by sending geometry_msgs/msg/TwistStamped messages.

See also: odrive_ros2_control

Architecture

The system launched by botwheel_explorer.launch.py looks like this:

Usage Instructions

This assumes that your ODrives are already configured (with node_id 0 and 1) according to the docs and ready to go.

1. Clone this repository
   • Either into your existing colcon workspace if you have one. In this case run all following commands in your workspace.
   • Or as a standalone directory. In this case switch to the cloned directory and run all following commands from there.
2. Install Dependencies

   rosdep install --from-paths odrive_ros2_control odrive_botwheel_explorer -y --ignore-src
   

1. Build

   colcon build --symlink-install --packages-up-to odrive_botwheel_explorer
   

1. Launch

   source ./install/setup.sh
   ros2 launch odrive_botwheel_explorer botwheel_explorer.launch.py
   

When the system finishes launching (may take a few seconds on a slow machine), the ODrives with node_id 0 and 1 should automatically go active.

When you exit this command, the ODrives disarm if their watchdog was enabled.

1. Inspect that the topics are available

   $ ros2 control list_hardware_interfaces
   command interfaces
           left_wheel_joint/effort [available] [unclaimed]
           left_wheel_joint/position [available] [unclaimed]
           left_wheel_joint/velocity [available] [claimed]
           right_wheel_joint/effort [available] [unclaimed]
           right_wheel_joint/position [available] [unclaimed]
           right_wheel_joint/velocity [available] [claimed]
   state interfaces
           left_wheel_joint/effort
           left_wheel_joint/position
           left_wheel_joint/velocity
           right_wheel_joint/effort
           right_wheel_joint/position
           right_wheel_joint/velocity
   

As you can see, there are two joints (two wheels) that have their velocity command interface claimed (by the DiffDriveController) and provide position and velocity feedback.

   $ ros2 topic list
   /botwheel_explorer/cmd_vel
   /botwheel_explorer/odom
   /botwheel_explorer/transition_event
   /diagnostics
   /dynamic_joint_states
   /joint_state_broadcaster/transition_event
   /joint_states
   /parameter_events
   /robot_description
   /rosout
   /tf
   /tf_static
   

1. Check ODrive feedback

   $ ros2 topic echo /joint_states
   ---
   header:
     stamp:
       sec: 1706131922
       nanosec: 319699404
     frame_id: ''
   name:
   - left_wheel_joint
   - right_wheel_joint
   position:
   - 56.5616569519043
   - .nan
   velocity:
   - 0.004984875209629536
   - .nan
   effort:
   - 9.469995711697266e-05
   - .nan
   ---
   

In this example the right ODrive is disconnected, therefore its feedback shows as .nan.

1. Drive the robot around

   The following command makes the BotWheel Explorer go forward with 0.2 m/s and turn right with 0.3 turns/s.

   ros2 topic pub --rate 30 /botwheel_explorer/cmd_vel geometry_msgs/msg/TwistStamped "
       twist:
         linear:
           x: 0.2
           y: 0.0
           z: 0.0
         angular:
           x: 0.0
           y: 0.0
           z: 0.3"
   

When you exit the command with Ctrl+C, the BotWheel Explorer comes to a halt.

Troubleshooting

• Getting spammed with warnings like:

   [ros2_control_node-1] [WARN] [1706131056.848045848] [resource_manager]: (hardware 'DiffBot'): 'left_wheel_joint/effort' command interface not in available list. This should not happen (hint: multiple cleanup calls).
   [ros2_control_node-1] [WARN] [1706131056.848081755] [resource_manager]: (hardware 'DiffBot'): 'left_wheel_joint/velocity' command interface not in available list. This should not happen (hint: multiple cleanup calls).
   [ros2_control_node-1] [WARN] [1706131056.848096588] [resource_manager]: (hardware 'DiffBot'): 'left_wheel_joint/position' command interface not in available list. This should not happen (hint: multiple cleanup calls).
   

This can mean that the CAN interface could not be opened. Check for Failed to initialize SocketCAN on can0 in the beginning of the log. Make sure the CAN interface exists and is up (check with ip link).