Twist Mux Controller

The TwistMuxController is a ROS 2 chainable controller designed to process velocity commands from multiple sources and forward them to hardware interfaces or other chainable controllers. The controllers support mobile platform controllers with holonomic and non-holonomic drive type.

Publishers

• ~/source [std_msgs/msg/String]: Publishes the source of the active velocity command. The source name corresponds to the key names in the cmd_vel_inputs parameter.

Subscribers

• {cmd_vel_inputs.source_key.topic} [geometry_msgs/msg/TwistStamped]: For each input in cmd_vel_inputs parameter, controller will create subscriber to that command velocity. The topic name depends on the topic parameter. See Example usage for example topics.

Parameters

• holonomic [bool, default: false]: Whether the robot drive type is holonomic or non-holonomic. This will affect the number of command interfaces.
• cmd_vel_inputs [dict, default: {}]: List of command velocity inputs. Each key in the dictionary has a unique name and the following parameters:
  • topic [string, default: {source_name}/cmd_vel]: Name of the topic to subscribe to.
  • timeout [double, default: 0.5]: Timeout for command velocity topic in seconds.
  • priority [uint, default: 0]: The priority of the input in range [0, 255], where 0 is the lowest priority and 255 is the highest. Note, if there are multiple inputs with the same priority, the output will be chosen arbitrary.
• command_interface_linear_x [string, default: linear/x/velocity]: Command interface for linear X velocity.
• command_interface_linear_y [string, default: linear/y/velocity]: Command interface for linear Y velocity. Available only if holonomic parameter is set to true.
• command_interface_angular_z [string, default: angular/z/velocity]: Command interface for angular velocity.

Interfaces

Exported Command Interfaces

• {node_name}/linear/x/velocity: Linear X Velocity
• {node_name}/linear/y/velocity: Linear Y Velocity. Available only if holonomic parameter is set to true.
• {node_name}/angular/z/velocity: Angular Velocity

Example Usage

Controller configuration:

  twist_mux_controller:
    ros__parameters:
      holonomic: false
      cmd_vel_inputs:
        manual:
          topic: manual/cmd_vel
          timeout: 0.2
          priority: 100
        autonomous:
          topic: autonomous/cmd_vel
          timeout: 0.2
          priority: 10
        unknown:
          topic: cmd_vel
          timeout: 0.2
          priority: 1
      command_interface_linear_x: drive_controller/linear/velocity
      command_interface_angular_z: drive_controller/angular/velocity

Above configuration will create subscribers for the following topics:

• /manual/cmd_vel
• /autonomous/cmd_vel
• /cmd_vel