Guideline for Object Avoidance in Autoware

Introduction

Key nodes for avoidance:

aster_avoid and velocity_set.

Working principle:

velocity_set will receive topic safety_waypoints to judge whether there is a barrier in the path. If there is a barrier, it will control the vehicle to decelerate or stop to avoid crash, which will publish to finaobstacle_waypoint_pub_waypoints. The place of barrier will publish to obstacle_waypoint.

aster_avoid will receive topic obstacle_waypoint. If there is a barrier, it will use astar algorithm to plan a new path, and publish to safety_waypoints.

Then, velocity_set will receive safety_waypoints from aster_avoid and work iteratively until no barrier found. If user close the "Enable Avoidance" in aster_avoid, velocity_set will only stop the vehicle but not re-plan a new path. Make sure you have opened aster_avoid even if you don't need the re-plan function.

Frequent problems

1. Planing conflict. Autoware has multiple path planing algorithms, such as lattice_planner, which may conflict when open more then one in the same time. Please close all related node about lattice_planner or other planing nodes when using aster_avoid and velocity_set.
2. Waypoint. The output of to node pure_pursit (which control the final speed) from velocity_set is finaobstacle_waypoint_pub_waypoints. Therefore, all speed output is depending on the waypoints information. Please open "Waypoint" in node pure_pursit.
3. Parameter setting. To make sure the vehicle can stop, set a high value to the following parameters:
   1. Stop Distance for Obstacle. The distance starting stop behavior between vehicle and obstacle. Reference value: 20-30 m.
   2. Decelerate Range. The distance starting deceleration behavior between vehicle and obstacle. There are some unknow questions in deceleration mode. Please set "" to 0 to ignore deceleration mode.
   3. Detection Range.
   4. Detection Height Top/Bottom. Threshold to determine whether it is an obstacle.
   5. Deceleration for Obstacle. Maximum deceleration for avoidance. Reference value: 4 m/s.
   6. Velocity Change Limit. The limit of velocity change for avoidance. Reference value: 10 km/h.
   7. Temporal Waypoints Size.