rocker_bogie_controller

Overview

Controller for rocker bogie drive wheel systems. Control is in the form of a velocity command, that is split then sent on the two steer and the four wheels of a rocker bogie drive configuration. Odometry is computed from the feedback from the hardware, and published.

The controller is created based on diff_drive_controller so it is compatible with ros_controller. You can easily activate this controller same as other ros_controllers with which you should be familiar.

Velocity commands

The controller works with a velocity twist from which it extracts the x component of the linear velocity and the z component of the angular velocity. Velocities on other components are ignored.

Hardware interface type

The controller works with steer joints through a position interface and wheel joints through a velocity interface.

Description

Subscribed Topics

• /fr01_rocker_bogie_controller/cmd_vel (geometry_msgs/Twist)
• Velocity command.

Published Topics

• /fr01_rocker_bogie_controller/odom (nav_msgs/Odometry)

• Odometry computed from the hardware feedback.

• Not properly implemented yet.

• /tf (tf/tfMessage)

• Transform from odom to base_footprint

• Not properly implemented yet.

Important parameters

See the following yaml file example and please feel requirements from its parameter names.

rosed fr01_control fr01_rocker_bogie_controller.yaml

#fr01:
# Publish all joint states -----------------------------------
joint_state_controller:
  type: joint_state_controller/JointStateController
  publish_rate: 50    

# Wheel & Steer (rocker_bogie_controller should be used without namespace)
fr01_rocker_bogie_controller:
    type        : "rocker_bogie_controller/RockerBogieController"
    left_wheel  : ['wheel_left_front_joint', 'wheel_left_middle_joint', 'wheel_left_back_joint']
    right_wheel : ['wheel_right_front_joint', 'wheel_right_middle_joint', 'wheel_right_back_joint']
    left_steer  : ['steer_left_front_joint', 'steer_left_back_joint']
    right_steer : ['steer_right_front_joint', 'steer_right_back_joint']
    publish_rate: 100

    pose_covariance_diagonal : [0.00001, 0.00001, 1000000000000.0, 1000000000000.0, 1000000000000.0, 0.001]
    twist_covariance_diagonal: [0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
    wheel_separation_multiplier: 1.0
    wheel_radius_multiplier    : 1.0
    cmd_vel_timeout: 20
    base_frame_id: base_footprint

    enable_odom_tf: true
    wheel_separation_w : 0.26
    wheel_separation_h : 0.4
    wheel_radius : 0.3

    linear:
      x:
        has_velocity_limits    : true
        max_velocity           : 0.9  # m/s
        min_velocity           : -0.9 # m/s
        has_acceleration_limits: true
        max_acceleration       : 1.7  # m/s^2
        min_acceleration       : -0.4 # m/s^2
    angular:
      z:
        has_velocity_limits    : true
        max_velocity           : 0.5  # rad/s
        has_acceleration_limits: true
        max_acceleration       : 1.5  # rad/s^2  #  wheel_right_front_joint_position_controller:

How to launch

• First, load parameters from fr01_rocker_bogie_controller.yaml.
• Of course you can also create your own yaml.
• Next, spawn controller named fr01_rocker_bogie_controller.
• Please do not specify namespace for now.

roslanch fr01_control fr01_sim_control.launch 

<launch>
    <!-- Load joint controller configurations from YAML file to parameter server -->
    <!-- <rosparam file="$(find fr01_control)/config/fr01_diff_drive_controller.yaml" command="load"/> -->
    <rosparam file="$(find fr01_control)/config/fr01_rocker_bogie_controller.yaml" command="load"/> 

    <!-- load the controllers -->
    <node name="controller_spawner" pkg="controller_manager"
        type="spawner" respawn="false"
        output="screen" 
        args="fr01_rocker_bogie_controller
        joint_state_controller
        " />

    <!-- convert joint states to TF transforms for rviz, etc -->
    <node name="robot_state_publisher" pkg="robot_state_publisher" type="robot_state_publisher"
        respawn="false" output="screen">
        <!-- <remap from="/joint_states" to="/fr01/joint_states" /> -->
    </node>

</launch>