Obstacle Stop Planner

Overview

obstacle_stop_planner has following modules

• Obstacle Stop Planner
  • inserts a stop point in trajectory when there is a static point cloud on the trajectory.
• Slow Down Planner
  • inserts a deceleration section in trajectory when there is a point cloud near the trajectory.
• Adaptive Cruise Controller (ACC)
  • embeds target velocity in trajectory when there is a dynamic point cloud on the trajectory.

Input topics

Output topics

Common Parameter

Obstacle Stop Planner

Role

This module inserts the stop point before the obstacle with margin. In nominal case, the margin is the sum of baselink_to_front and max_longitudinal_margin. The baselink_to_front means the distance between baselink(center of rear-wheel axis) and front of the car. The detection area is generated along the processed trajectory as following figure. (This module cut off the input trajectory behind the ego position and decimates the trajectory points for reducing computational costs.)

If another stop point has already been inserted by other modules within max_longitudinal_margin, the margin is the sum of baselink_to_front and min_longitudinal_margin. This feature exists to avoid stopping unnaturally position. (For example, the ego stops unnaturally far away from stop line of crosswalk that pedestrians cross to without this feature.)

The module searches the obstacle pointcloud within detection area. When the pointcloud is found, Adaptive Cruise Controller modules starts to work. only when Adaptive Cruise Controller modules does not insert target velocity, the stop point is inserted to the trajectory. The stop point means the point with 0 velocity.

Restart prevention

If it needs X meters (e.g. 0.5 meters) to stop once the vehicle starts moving due to the poor vehicle control performance, the vehicle goes over the stopping position that should be strictly observed when the vehicle starts to moving in order to approach the near stop point (e.g. 0.3 meters away).

This module has parameter hold_stop_margin_distance in order to prevent from these redundant restart. If the vehicle is stopped within hold_stop_margin_distance meters from stop point of the module, the module judges that the vehicle has already stopped for the module’s stop point and plans to keep stopping current position even if the vehicle is stopped due to other factors.

Parameters

Stop position

Obstacle detection area

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