Behavior Path Planner

The Behavior Path Planner’s main objective is to significantly enhance the safety of autonomous vehicles by minimizing the risk of accidents. It improves driving efficiency through time conservation and underpins reliability with its rule-based approach. Additionally, it allows users to integrate their own custom behavior modules or use it with different types of vehicles, such as cars, buses, and delivery robots, as well as in various environments, from busy urban streets to open highways.

The module begins by thoroughly analyzing the ego vehicle’s current situation, including its position, speed, and surrounding environment. This analysis leads to essential driving decisions about lane changes or stopping and subsequently generates a path that is both safe and efficient. It considers road geometry, traffic rules, and dynamic conditions while also incorporating obstacle avoidance to respond to static and dynamic obstacles such as other vehicles, pedestrians, or unexpected roadblocks, ensuring safe navigation.

Moreover, the planner actively interacts with other traffic participants, predicting their actions and accordingly adjusting the vehicle’s path. This ensures not only the safety of the autonomous vehicle but also contributes to smooth traffic flow. Its adherence to traffic laws, including speed limits and traffic signals, further guarantees lawful and predictable driving behavior. The planner is also designed to minimize sudden or abrupt maneuvers, aiming for a comfortable and natural driving experience.

!!! note

The [Planning Component Design](https://autowarefoundation.github.io/autoware-documentation/v1.0/design/autoware-architecture/planning/) Document outlines the foundational philosophy guiding the design and future development of the Behavior Path Planner module. We strongly encourage readers to consult this document to understand the rationale behind its current configuration and the direction of its ongoing development.

Purpose / Use Cases

Essentially, the module has three primary responsibilities:

1. Creating a path based on the traffic situation.
2. Generating drivable area, i.e. the area within which the vehicle can maneuver.
3. Generating turn signal commands to be relayed to the vehicle interface.

Features

Supported Scene Modules

Behavior Path Planner has following scene modules

!!! Note

click on the following images to view the video of their execution

<div align="center">
    <table>
        <tr>
            <td><img src="./image/supported_module_lane_following.svg" alt="Lane Following Module" width="300"></td>
            <td><a href="https://www.youtube.com/watch?v=A_V9yvfKZ4E"><img src="./image/supported_module_avoidance.svg" alt="Avoidance Module" width="300"></a></td>
            <td><img src="./image/supported_module_avoidance_by_lane_change.svg" alt="Avoidance by Lane Change Module" width="300"></td>
        </tr>
        <tr>
            <td><a href="https://www.youtube.com/watch?v=0jRDGQ84cD4"><img src="./image/supported_module_lane_change.svg" alt="Lane Change Module" width="300"></a></td>
            <td><a href="https://www.youtube.com/watch?v=xOjnPqoHup4"><img src="./image/supported_module_start_planner.svg" alt="Start Planner Module" width="300"></a></td>
            <td><a href="https://www.youtube.com/watch?v=ornbzkWxRWU"><img src="./image/supported_module_goal_planner.svg" alt="Goal Planner Module" width="300"></a></td>
        </tr>
    </table>
</div>

!!! Note

Users can refer to [Planning component design](https://autowarefoundation.github.io/autoware-documentation/v1.0/design/autoware-architecture/planning/#supported-functions) for some additional behavior.

How to add or implement new module?

All scene modules are implemented by inheriting base class scene_module_interface.hpp.

!!! Warning

The remainder of this subsection is work in progress (WIP).

Planner Manager

The Planner Manager’s responsibilities include:

1. Activating the relevant scene module in response to the specific situation faced by the autonomous vehicle. For example, when a parked vehicle blocks the ego vehicle’s driving lane, the manager would engage the avoidance module.
2. Managing the execution order when multiple modules are running simultaneously. For instance, if both the lane-changing and avoidance modules are operational, the manager decides which should take precedence.
3. Merging paths from multiple modules when they are activated simultaneously and each generates its own path, thereby creating a single functional path.

!!! note

To check the scene module's transition, i.e.: registered, approved and candidate modules, set `verbose: true` in the [behavior path planner configuration file](https://github.com/autowarefoundation/autoware_launch/blob/0cd5d891a36ac34a32a417205905c109f2bafe7b/autoware_launch/config/planning/scenario_planning/lane_driving/behavior_planning/behavior_path_planner/behavior_path_planner.param.yaml#L3).

![Scene module's transition table](./image/checking_module_transition.png)

!!! note

For more in-depth information, refer to [Manager design](./docs/behavior_path_planner_manager_design.md) document.

Inputs / Outputs / API

Input

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