spot_ros2_control

spot_ros2_control

This is a ROS 2 package designed to communicate with Spot's joint control API through ROS 2 control. It uses the hardware interface provided in the spot_hardware_interface package to connect to the robot (and also supports a mock hardware interface that forwards commands directly to state). By default, it loads a standard joint state broadcaster and forward position controller provided from ros2_control. An alternative controller from spot_controllers that forwards position, velocity, and effort commands at the same time is also available.

On-robot

If your parameters for authenticating with your robot are set in the environment variables BOSDYN_CLIENT_USERNAME, BOSDYN_CLIENT_PASSWORD, and SPOT_IP, run:

ros2 launch spot_ros2_control spot_ros2_control.launch.py hardware_interface:=robot

Login information can also be set in a configuration file, the same as in the spot_driver launchfile. For example, if you have a config file spot_ros.yaml containing the following information:

/**:
  ros__parameters:
    username: "username"
    password: "password"
    hostname: "00.00.00.00"

You can then run the launchfile with the following command:

ros2 launch spot_ros2_control spot_ros2_control.launch.py hardware_interface:=robot config_file:=path/to/spot_ros.yaml

Joint level gains can also be specified in this same config file under the parameter names k_q_p and k_qd_p. If you do not specify these parameters, the default gains from the spot-sdk joint control examples are used during command streaming. The example below shows a valid configuration for a robot with an arm as each list contains 19 elements. More information on how these gains are used by Spot can be found here.

/**:
  ros__parameters:
    k_q_p: [624.0, 936.0, 286.0,  624.0, 936.0, 286.0, 624.0, 936.0, 286.0, 624.0, 936.0, 286.0, 1020.0, 255.0, 204.0, 102.0, 102.0, 102.0, 16.0]
    k_qd_p: [5.20, 5.20, 2.04, 5.20, 5.20, 2.04, 5.20, 5.20, 2.04, 5.20, 5.20, 2.04, 10.2, 15.3, 10.2, 2.04, 2.04, 2.04, 0.32]

If you wish to launch these nodes in a namespace, add the argument spot_name:=<Robot Name>.

This hardware interface will stream the joint angles of the robot at 333 Hz onto the topic /<Robot Name>/low_level/joint_states.

Commands can be sent on the topic /<Robot Name>/forward_position_controller/commands. This will forward position commands directly to the joint control API through the hardware interface. The controller expects the command array to contain the list of positions to forward for each joint on the robot.

An alternative feed-forward controller provided by the spot_controllers package can be used to specify the position, velocity, and effort of all joints at the same time. To bring up this controller, add the launch argument robot_controller:=forward_state_controller. Commands can then be sent on the topic /<Robot Name>/forward_state_controller/commands. This controller expects the ordering of the command array to be [<positions for each joint>, <velocities for each joint>, <efforts for each joint>].

Caution

When using the forward position and state controllers, there is no safety mechanism in place to ensure smooth motion. The ordering of the command must match the ordering of the joints specified in the controller configuration file (here for robots with an arm or here for robots without an arm), and the robot can move in unpredictable and dangerous ways if this is not set correctly. Make sure to keep a safe distance from the robot when working with these controllers and ensure the e-stop can easily be pressed if needed.

Additionally, the state publisher node, object synchronization node, and image publisher nodes from spot_driver will get launched by default when running on the robot to provide extra information such as TF, odometry, and camera feeds. To turn off the image publishers (which can cause problems with bandwidth), add the launch argument launch_image_publishers:=false.

Mock

To use a mock hardware interface, run:

ros2 launch spot_ros2_control spot_ros2_control.launch.py hardware_interface:=mock

By default, this will load a robot with no arm. If you want your mock robot to have an arm, add the launch argument mock_arm:=True.

Examples

Examples are provided to replicate these joint control examples from Boston Dynamics. They are designed to show how you can send commands to the robot using the built in forward position controller, and can be run in mock mode or on the real robot.

Run the following commands to test these examples after launching spot_ros2_control.launch.py. If your robot does not have an arm:

ros2 launch spot_ros2_control noarm_squat.launch.py

Or, if your robot does have an arm:

ros2 launch spot_ros2_control wiggle_arm.launch.py

Add the launch argument spot_name:=<namespace> if the ros2 control stack was launched in a namespace.

Additional Arguments

• controllers_config: If this argument is unset, a general purpose controller configuration will be loaded containing a forward position controller and a joint state publisher, that is filled appropriately based on whether or not the robot used (mock or real) has an arm. The forward state controller is also specified here. If you wish to load different controllers, this can be set here.
• robot_controller: This is the name of the robot controller that will be started when the launchfile is called. The default is the simple forward position controller. The name must match a controller in the controllers_config file.
• launch_rviz: If you do not want rviz to be launched, add the argument launch_rviz:=False.