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github_url:https://github.com/ros-controls/ros2_controllers/blob/{REPOS_FILE_BRANCH}/omni_wheel_drive_controller/doc/userdoc.rst

omni_wheel_drive_controller

Controller for mobile robots with omnidirectional drive.

Supports using three or more omni wheels spaced at an equal angle from each other in a circular formation. To better understand this, have a look at :ref:`mobile_robot_kinematics`.

The controller uses velocity input, i.e., stamped Twist messages where linear x, y, and angular z components are used. Values in other components are ignored.

Odometry is computed from hardware feedback and published.

Other features

  • Realtime-safe implementation.
  • Odometry publishing
  • Automatic stop after command time-out

Description of controller's interfaces

References (from a preceding controller)

When controller is in chained mode, it exposes the following references which can be commanded by the preceding controller:

  • <controller_name>/linear/x/velocity double, in m/s
  • <controller_name>/linear/y/velocity double, in m/s
  • <controller_name>/angular/z/velocity double, in rad/s

Together, these represent the body twist (which in unchained-mode would be obtained from ~/cmd_vel).

State interfaces

As feedback interface type the joints' position (hardware_interface::HW_IF_POSITION) or velocity (hardware_interface::HW_IF_VELOCITY, if parameter position_feedback=false) are used.

Command interfaces

Joints' velocity (hardware_interface::HW_IF_VELOCITY) are used.

ROS 2 Interfaces

Subscribers

~/cmd_vel [geometry_msgs/msg/TwistStamped]
Velocity command for the controller. The controller extracts the x and y component of the linear velocity and the z component of the angular velocity. Velocities on other components are ignored.

Publishers

~/odom [nav_msgs::msg::Odometry]
This represents an estimate of the robot's position and velocity in free space.
/tf [tf2_msgs::msg::TFMessage]
tf tree. Published only if enable_odom_tf=true

Parameters

This controller uses the generate_parameter_library to handle its parameters. The parameter definition file located in the src folder contains descriptions for all the parameters used by the controller.

.. generate_parameter_library_details:: ../src/omni_wheel_drive_controller_parameters.yaml

An example parameter file for this controller can be found in the test directory:

.. literalinclude:: ../test/config/test_omni_wheel_drive_controller.yaml
   :language: yaml