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 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.

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