diff_drive_controller

Controller for mobile robots with differential drive.

As input it takes velocity commands for the robot body, which are translated to wheel commands for the differential drive base.

Odometry is computed from hardware feedback and published.

For an introduction to mobile robot kinematics and the nomenclature used here, see mobile_robot_kinematics.

Other features

• Realtime-safe implementation.

• Odometry publishing

• Task-space velocity, acceleration and jerk limits

• Automatic stop after command time-out

Description of controller’s interfaces

References

(the controller is not yet implemented as chainable controller)

Feedback

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.

Output

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

ROS 2 Interfaces

Subscribers

~/cmd_vel [geometry_msgs/msg/TwistStamped]

Velocity command for the controller, if use_stamped_vel=true. The controller extracts the x component of the linear velocity and the z component of the angular velocity. Velocities on other components are ignored.

~/cmd_vel_unstamped [geometry_msgs::msg::Twist]

Velocity command for the controller, if use_stamped_vel=false. The controller extracts the x 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

~/cmd_vel_out [geometry_msgs/msg/TwistStamped]

Velocity command for the controller, where limits were applied. Published only if publish_limited_velocity=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: