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AdaptiveToleranceGoalChecker

The adaptive tolerance goal checker uses two underlying goal tolerances a fine and a coarse one. The fine tolerance is used to instantly trigger goal reached when the robot is close to the goal (functionally same as simple goal checker), while the coarse tolerance is used to trigger goal reached when the robot is further from the goal but is making no meaningful progress towards it (or not expected to).

The goal is cosidered reached when one of the following conditions is met:

  • The robot is within the fine goal tolerance
  • The robot is within the coarse goal tolerance and its linear velocity and orientational velocity are below a specified threshold for a set amount of cycles
  • The robot is within the coarse goal tolerance and robots distance to the goal is not improving for a set amount of cycles
  • The robot is within the coarse goal tolerance and it has passed the finish line (the line perpendicular to the first robot pose within the coarse tolerance and passing through the goal pose)

When stateful is enabled, the XY goal reached state is preserved after one of the above conditions has been satisfied. See xy_goal_tolerance_buffer for configuring the hysteresis behavior.

AdaptiveToleranceGoalChecker Illustration

Parameters

<nav2_controller plugin>: nav2_controller plugin name defined in the goal_checker_plugin_id parameter in Controller Server.

Type: double Default: 0.10

Fine (desired) XY tolerance to the goal (m). When the robot's XY distance to the goal is within this tolerance, the goal is considered reached immediately (subject to the yaw check). Should be smaller than coarse_xy_goal_tolerance.

Type: double Default: 0.25

Coarse (fallback) XY tolerance to the goal (m). When the robot is within this tolerance but outside the fine tolerance, the goal is considered reached only if one of the coarse-tier acceptance conditions fires (stopped stagnation, distance stagnation, or finish-line crossing). Should be larger than fine_xy_goal_tolerance.

Type: double Default: 0.0

Hysteresis buffer for stateful XY position checking (m). When stateful is true, after the XY goal condition has been satisfied, the robot may drift within the corresponding accepted tolerance plus this buffer without rechecking the XY position. If the robot moves outside this buffered region, the previous XY reached state is cleared and the XY position must be checked again.

Type: double Default: 0.25

Tolerance on the yaw angle to the goal orientation (rad). The goal is only considered reached once the XY check passes AND the yaw error is within this tolerance.

Type: double Default: 1.0

Maximum remaining transformed global plan length above which the goal check is skipped (m). Prevents premature goal acceptance when the robot is still far from the goal along the path.

Type: bool Default: true

If true, once the XY tolerance is satisfied the checker latches that result and only re-evaluates yaw on subsequent cycles. If false, both XY and yaw are re-checked every cycle.

Type: bool Default: false

If true, the yaw check accepts both the goal orientation and its 180° opposite (useful for symmetric robots that can drive forward or backward). If false, only the goal orientation is accepted.

Type: double Default: 0.10

Linear velocity threshold below which the robot is considered "stopped" for the stopped-stagnation acceptance path (m/s). Combined with rot_stopped_velocity and required_stagnation_cycles.

Type: double Default: 0.10

Angular velocity threshold below which the robot is considered "stopped" for the stopped-stagnation acceptance path (rad/s). Combined with trans_stopped_velocity and required_stagnation_cycles.

Type: int Default: 15

Number of consecutive controller cycles for which a stagnation condition must hold before the coarse-tier acceptance fires. Applies to both stopped stagnation (velocity below threshold) and distance stagnation (no improvement in distance to goal). Must be >= 1.

Example

controller_server:
  ros__parameters:
    goal_checker_plugins: ["goal_checker"]
    goal_checker:
      plugin: "nav2_controller::AdaptiveToleranceGoalChecker"
      fine_xy_goal_tolerance: 0.10
      coarse_xy_goal_tolerance: 0.25
      xy_goal_tolerance_buffer: 0.10
      yaw_goal_tolerance: 0.25
      path_length_tolerance: 1.0
      stateful: true
      symmetric_yaw_tolerance: false
      trans_stopped_velocity: 0.10
      rot_stopped_velocity: 0.10
      required_stagnation_cycles: 15