Regulated Pure Pursuit¶

Source code on Github.

The Regulated Pure Pursuit controller implements a variation on the Pure Pursuit controller that specifically targeting service / industrial robot needs. It regulates the linear velocities by curvature of the path to help reduce overshoot at high speeds around blind corners allowing operations to be much more safe. It also better follows paths than any other variation currently available of Pure Pursuit. It also has heuristics to slow in proximity to other obstacles so that you can slow the robot automatically when nearby potential collisions. It also implements the Adaptive lookahead point features to be scaled by velocities to enable more stable behavior in a larger range of translational speeds.

See the package’s README for more complete information.

Regulated Pure Pursuit Parameters¶

desired_linear_vel:

Type	Default
double	0.5

Description: The desired maximum linear velocity (m/s) to use.

max_linear_accel:

Type	Default
double	2.5

Description: Maximum acceleration for linear velocity (m/s/s)

max_linear_decel:

Type	Default
double	2.5

Description: Maximum deceleration for linear velocity (m/s/s)

lookahead_dist:

Type	Default
double	0.6

Description: The lookahead distance (m) to use to find the lookahead point when use_velocity_scaled_lookahead_dist is false.

min_lookahead_dist:

Type	Default
double	0.3

Description: The minimum lookahead distance (m) threshold when use_velocity_scaled_lookahead_dist is true.

max_lookahead_dist:

Type	Default
double	0.9

Description: The maximum lookahead distance (m) threshold when use_velocity_scaled_lookahead_dist is true.

lookahead_time:

Type	Default
double	1.5

Description: The time (s) to project the velocity by when use_velocity_scaled_lookahead_dist is true. Also known as the lookahead gain.

rotate_to_heading_angular_vel:

Type	Default
double	1.8

Description: If use_rotate_to_heading is true, this is the angular velocity to use.

transform_tolerance:

Type	Default
double	0.1

Description: The TF transform tolerance (s).

use_velocity_scaled_lookahead_dist:

Type	Default
double	0.4

Description: Whether to use the velocity scaled lookahead distances or constant lookahead_distance.

min_approach_linear_velocity:

Type	Default
double	0.05

Description: The minimum velocity (m/s) threshold to apply when approaching the goal to ensure progress, when use_approach_linear_velocity_scaling is true.

use_approach_linear_velocity_scaling:

Type	Default
bool	true

Description: Whether to scale the linear velocity down on approach to the goal for a smooth stop.

max_allowed_time_to_collision:

Type	Default
double	1.0

Description: The time (s) to project a velocity command forward to check for collisions.

use_regulated_linear_velocity_scaling:

Type	Default
bool	true

Description: Whether to use the regulated features for path curvature (e.g. slow on high curvature paths).

use_cost_regulated_linear_velocity_scaling:

Type	Default
bool	true

Description: Whether to use the regulated features for proximity to obstacles (e.g. slow in close proximity to obstacles).

regulated_linear_scaling_min_radius:

Type	Default
double	0.90

Description: The turning radius (m) for which the regulation features are triggered when use_regulated_linear_velocity_scaling is tru. Remember, sharper turns have smaller radii.

regulated_linear_scaling_min_speed:

Type	Default
double	0.25

Description: The minimum speed (m/s) for which any of the regulated heuristics can send, to ensure process is still achievable even in high cost spaces with high curvature.

use_rotate_to_heading:

Type	Default
bool	true

Description: Whether to enable rotating to rough heading and goal orientation when using holonomic planners. Recommended on for all robot types that can rotate in place.

rotate_to_heading_min_angle:

Type	Default
double	0.785

Description: The difference in the path orientation and the starting robot orientation (radians) to trigger a rotate in place, if use_rotate_to_heading is true.

max_angular_accel:

Type	Default
double	3.2

Description: Maximum allowable angular acceleration (m/s/s) while rotating to heading, if use_rotate_to_heading is true.

goal_dist_tol:

Type	Default
double	0.25

Description: XY tolerance from goal to rotate to the goal heading, if use_rotate_to_heading is true. This should match or be smaller than the GoalChecker’s translational goal tolerance.

Example¶

controller_server:
  ros__parameters:
    use_sim_time: True
    controller_frequency: 20.0
    min_x_velocity_threshold: 0.001
    min_y_velocity_threshold: 0.5
    min_theta_velocity_threshold: 0.001
    progress_checker_plugin: "progress_checker"
    goal_checker_plugin: "goal_checker"
    controller_plugins: ["FollowPath"]

    progress_checker:
      plugin: "nav2_controller::SimpleProgressChecker"
      required_movement_radius: 0.5
      movement_time_allowance: 10.0
    goal_checker:
      plugin: "nav2_controller::SimpleGoalChecker"
      xy_goal_tolerance: 0.25
      yaw_goal_tolerance: 0.25
      stateful: True
    FollowPath:
      plugin: "nav2_regulated_pure_pursuit_controller::RegulatedPurePursuitController"
      desired_linear_vel: 0.5
      max_linear_accel: 2.5
      max_linear_decel: 2.5
      lookahead_dist: 0.6
      min_lookahead_dist: 0.3
      max_lookahead_dist: 0.9
      lookahead_time: 1.5
      rotate_to_heading_angular_vel: 1.8
      transform_tolerance: 0.1
      use_velocity_scaled_lookahead_dist: false
      min_approach_linear_velocity: 0.05
      use_approach_linear_velocity_scaling: true
      max_allowed_time_to_collision: 1.0
      use_regulated_linear_velocity_scaling: true
      use_cost_regulated_linear_velocity_scaling: false
      regulated_linear_scaling_min_radius: 0.9
      regulated_linear_scaling_min_speed: 0.25
      use_rotate_to_heading: true
      rotate_to_heading_min_angle: 0.785
      max_angular_accel: 3.2
      goal_dist_tol: 0.25