Following Server

Source code on Github.

The Following Server in opennav_following implements a server for following dynamic objects from a detection topic or specific reference frame. This server allows the robot to follow and maintain a determined distance from a detected object or specific frame, using topic-based detection techniques or coordinate frame tracking. The server is designed to be called by a BT application or autonomy application to follow moving objects.

Parameters

`controller_frequency`

Type: double Default: 50.0: Control frequency (Hz) for the following control loop.

`detection_timeout`

Type: double Default: 2.0: Timeout (s) to wait for detection of the object to follow.

`rotate_to_object_timeout`

Type: double Default: 10.0: Timeout (s) to rotate searching for the object when detection is lost.

`static_object_timeout`

Type: double Default: -1.0: Timeout (s) to stop following when the object remains static. If -1.0, the robot will follow indefinitely.

`linear_tolerance`

Type: double Default: 0.15: Linear tolerance (m) to consider that the target position has been reached.

`angular_tolerance`

Type: double Default: 0.15: Angular tolerance (rad) to consider that the target orientation has been reached.

`max_retries`

Type: int Default: 3: Maximum number of retries when detection or control fails.

`base_frame`

Type: string Default: "base_link": Robot's base frame for control law.

`fixed_frame`

Type: string Default: "odom": Fixed frame to use, recommended to be a smooth odometry frame not map.

`filter_coef`

Type: double Default: 0.1: Filter coefficient for smoothing object pose detections.

`desired_distance`

Type: double Default: 1.0: Desired distance (m) to maintain from the followed object.

`skip_orientation`

Type: bool Default: true: If true, ignore the detected object's orientation and point toward it from the robot's position.

`search_by_rotating`

Type: bool Default: false: If true, the robot will rotate in place when it loses object detection to try to find it again.

`search_angle`

Type: double Default: M_PI_2: Maximum angle (rad) to rotate when searching for the object.

`odom_topic`

Type: string Default: "odom": Odometry topic to use for obtaining the robot's current velocity.

`odom_duration`

Type: double Default: 0.3: Time (s) to buffer odometry commands to estimate the robot speed.

`transform_tolerance`

Type: double Default: 0.1: Time with which to post-date the transform that is published, to indicate that this transform is valid into the future.

Example

following_server:
  ros__parameters:
    controller_frequency: 50.0
    detection_timeout: 2.0
    rotate_to_object_timeout: 10.0
    static_object_timeout: 30.0  # -1.0 for indefinite following
    linear_tolerance: 0.15
    angular_tolerance: 0.15
    max_retries: 3
    base_frame: "base_link"
    fixed_frame: "odom"
    filter_coef: 0.1
    desired_distance: 1.0
    skip_orientation: true
    search_by_rotating: false
    odom_topic: "odom"
    odom_duration: 0.3
    transform_tolerance: 0.1

    # Controller configuration (inherited from docking controller)
    controller:
      k_phi: 3.0
      k_delta: 2.0
      beta: 0.4
      lambda: 2.0
      v_linear_min: 0.1
      v_linear_max: 0.5
      v_angular_max: 1.0
      slowdown_radius: 0.15
      use_collision_detection: false
      transform_tolerance: 0.1