Proposal for the New Drivable Area data structure

[purewater0901]

Currently, Autoware uses occupancy grid to describe drivable area. This drivable area is generated in behavior path planer. It is used in the motion planner, especially in Obstacle Avoidance Planner now. Path and PathWithLaneID contains drivable area in them.

• path
• pathwithlaneid

However, occupancy grid has several issues, I would like to change it to line string. In this format, drivable area can be described as left bound and right bound lines.

I compared the occupancy grid to line string, and summarized it in the following table.

	Occupancy Grid	Line String
Pros	Flexible behavior for motion planner	Small Data Size Can handle overlapped trajectory
Cons	Large Data Size Cannot handle overlapped trajectory Accuracy changes based on discretization method	Motion planner cannot change its behavior

After I discussed with TIER IV members, we suggest using line string as its advantages outweigh its disadvantages. If you have any idea about the drivable area, we are happy to discuss it.

I also put the image of the new type of the drivable area.

cc: @yukkysaito @mitsudome-r

[purewater0901]

Difficulty with line string

Since we decide the drivable area in behavior path planner, it is difficult for motion planner to change its behavior. In the following example, behavior path planner decided to swerve the obstacle by passing its right side, so motion planner cannot try to avoid it from left side. However, this will not be a big issue in most of the cases.

Difficulty with Occupancy grid

In the following case, it has to deal with overlapped path. However, it is not easy to find a boundary in the crossed section.

[xmfcx]

How do you define left and right boundaries for 4-way intersections?

The image I sent is from Tesla fsd and as far as I know they only mark road boundaries. Not as left/right.

[yukkysaito]

The "right/left bound" is used by the behavior planner to indicate the possible driving area to the motion planner. In this case, I don't think there is a pattern of indicating four independent sides.

[mitsudome-r]

I think we are trying to generate something similar to yellow lines in Zoox video: https://www.youtube.com/watch?v=rZ6hH2Frrf4

[TakaHoribe]

@xmfcx @mitsudome-r We're now thinking to start the implementation of the proposed method. Please let us know if you have any concerns.

[yukkysaito]

reference PRs :

• feat(behavior_path_planner, obstacle_avoidance_planner): add new drivable area autoware.universe#2472
• feat(autoware_auto_planning_msgs): remove drivable_area and add left and right bound tier4/autoware_auto_msgs#36
• chore: sync awf-latest tier4/autoware_launch#595
• feat(tier4_auto_msgs_converter): remove unnecessary code tier4/tier4_autoware_msgs#67