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tricycle_controller

Controller for mobile robots with a single double-actuated wheel, including traction and steering. An example is a tricycle robot with the actuated wheel in the front and two trailing wheels on the rear axle.

Input for control are robot base_link twist commands which are translated to traction and steering commands for the tricycle drive base. Odometry is computed from hardware feedback and published.

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.

Other features

Realtime-safe implementation. Odometry publishing Velocity, acceleration and jerk limits Automatic stop after command timeout

Parameters

This controller uses the generate_parameter_library to handle its parameters.

traction_joint_name (string)

Name of the traction joint

Default: “”

Constraints:

parameter is not empty

steering_joint_name (string)

Name of the steering joint

Default: “”

Constraints:

parameter is not empty

wheelbase (double)

Shortest distance between the front wheel and the rear axle. If this parameter is wrong, the robot will not behave correctly in curves.

Default: 0.0

wheel_radius (double)

Radius of a wheel, i.e., wheels size, used for transformation of linear velocity into wheel rotations. If this parameter is wrong the robot will move faster or slower then expected.

Default: 0.0

odom_frame_id (string)

Name of the frame for odometry. This frame is parent of base_frame_id when controller publishes odometry.

Default: “odom”

base_frame_id (string)

Name of the robot’s base frame that is child of the odometry frame.

Default: “base_link”

pose_covariance_diagonal (double_array)

Odometry covariance for the encoder output of the robot for the pose. These values should be tuned to your robot’s sample odometry data, but these values are a good place to start: [0.001, 0.001, 0.001, 0.001, 0.001, 0.01].

Default: {0.0, 0.0, 0.0, 0.0, 0.0, 0.0}

twist_covariance_diagonal (double_array)

Odometry covariance for the encoder output of the robot for the speed. These values should be tuned to your robot’s sample odometry data, but these values are a good place to start: [0.001, 0.001, 0.001, 0.001, 0.001, 0.01].

Default: {0.0, 0.0, 0.0, 0.0, 0.0, 0.0}

open_loop (bool)

If set to true the odometry of the robot will be calculated from the commanded values and not from feedback.

Default: false

enable_odom_tf (bool)

Publish transformation between odom_frame_id and base_frame_id.

Default: false

odom_only_twist (bool)

for doing the pose integration in separate node.

Default: false

cmd_vel_timeout (int)

Timeout in milliseconds, after which input command on cmd_vel topic is considered staled.

Default: 500

publish_ackermann_command (bool)

Publish limited commands.

Default: false

velocity_rolling_window_size (int)

Size of the rolling window for calculation of mean velocity use in odometry.

Default: 10

Constraints:

greater than 0

use_stamped_vel (bool)

Use stamp from input velocity message to calculate how old the command actually is.

Default: true

traction.max_velocity (double)