Behavior Velocity Planner

Overview

behavior_velocity_planner is a planner that adjust velocity based on the traffic rules. It consists of several modules.

• Blind Spot
• Crosswalk
• Detection Area
• Intersection
• Stop Line
• Traffic Light
• Occlusion Spot

When each module plans velocity, it considers based on base_link(center of rear-wheel axis) pose. So for example, in order to stop at a stop line with the vehicles' front on the stop line, it calculates base_link position from the distance between base_link to front and modifies path velocity from the base_link position.

Input topics

Name	Type	Description
~input/path_with_lane_id	autoware_planning_msgs::PathWithLaneId	path with lane_id
~input/vector_map	autoware_lanelet2_msgs::MapBin	vector map
~input/vehicle_velocity	geometry_msgs::TwistStamped	vehicle velocity
~input/dynamic_objects	autoware_perception_msgs::DynamicObjectArray	dynamic objects
~input/no_ground_pointcloud	sensor_msgs::PointCloud2	obstacle pointcloud
~input/traffic_light_states	autoware_perception_msgs::TrafficLightStateArray	traffic light states

Output topics

Name	Type	Description
~output/path	autoware_planning_msgs::Path	path to be followed
~output/stop_reasons	autoware_planning_msgs::StopReasonArray	reasons that cause the vehicle to stop

Node parameters

Parameter	Type	Description
launch_blind_spot	bool	whether to launch blind_spot module
launch_crosswalk	bool	whether to launch crosswalk module
launch_detection_area	bool	whether to launch detection_area module
launch_intersection	bool	whether to launch intersection module
launch_traffic_light	bool	whether to launch traffic light module
launch_stop_line	bool	whether to launch stop_line module
launch_occlusion_spot	bool	whether to launch occlusion_spot module
forward_path_length	double	forward path length
backward_path_length	double	backward path length
max_accel	double	(to be a global parameter) max acceleration of the vehicle
delay_response_time	double	(to be a global parameter) delay time of the vehicle's response to control commands

Modules

Stop Line

Role

This module plans velocity so that the vehicle can stop right before stop lines and restart driving after stopped.

Module Parameters

Parameter	Type	Description
stop_margin	double	a margin that the vehicle tries to stop before stop_line
stop_check_dist	double	when the vehicle is within stop_check_dist from stop_line and stopped, move to STOPPED state

Flowchart

This algorithm is based on segment. segment consists of two node points. It's useful for removing boundary conditions because if segment(i) exists we can assume node(i) and node(i+1) exist.

First, this algorithm finds a collision between reference path and stop line. Then, we can get collision segment and collision point.

Next, based on collision point, it finds offset segment by iterating backward points up to a specific offset length. The offset length is stop_margin(parameter) + base_link to front(to adjust head pose to stop line). Then, we can get offset segment and offset from segment start.

After that, we can calculate a offset point from offset segment and offset. This will be stop_pose.

Traffic Light

Role

Judgement of a stop and a velocity planning according to a traffic light color.

Launch Timing

Launches when there is a traffic light on a target lane

Algorithm

1. Obtains a traffic light mapped to the route and a stop line correspond to the traffic light from a map information.

2. Uses the highest reliability one of the traffic light recognition result and if the color of that was red, generates a stop point.

3. When vehicle current velocity is

   • higher than 2.0m/s ⇒ pass judge(using next slide formula)
   • lower than 2.0m/s ⇒ stop

4. When it to be judged that vehicle can’t stop before stop line, autoware chooses one of the following behaviors

   • "can pass through" stop line during yellow lamp => pass
   • "can’t pass through" stop line during yellow lamp => emergency stop

Dilemma Zone

• yellow lamp line

  It’s called “yellow lamp line” which shows the distance traveled by the vehicle during yellow lamp.

• dilemma zone

  It’s called “dilemma zone” which satisfies following conditions:

  • vehicle can’t pass through stop line during yellow lamp.(right side of the yellow lamp line)

  • vehicle can’t stop under deceleration and jerk limit.(left side of the pass judge curve)

    ⇒emergency stop(relax deceleration and jerk limitation in order to observe the traffic regulation)

• optional zone

  It’s called “optional zone” which satisfies following conditions:

  • vehicle can pass through stop line during yellow lamp.(left side of the yellow lamp line)

  • vehicle can stop under deceleration and jerk limit.(right side of the pass judge curve)

    ⇒ stop(autoware selects the safety choice)

Module Parameters

Parameter	Type	Description
stop_margin	double	[m] margin before stop point
tl_state_timeout	double	[s] time out for detected traffic light result.
external_tl_state_timeout	double	[s] time out for external traffic input
yellow_lamp_period	double	[s] time for yellow lamp
enable_pass_judge	bool	[-] weather to use pass judge

Flowchart

Intersection

Role

Judgement whether a vehicle can go into an intersection or not by a dynamic object information, and planning a velocity of the start/stop

Launch Timing

Launches when there is an intersection area on a target lane

Module Parameters

Parameter	Type	Description
intersection/state_transit_margin_time	double	[m] time margin to change state
intersection/decel_velocity	double	[m] deceleration velocity in intersection
intersection/stop_line_margin	double	[m] margin before stop line
intersection/stuck_vehicle_detect_dist	double	[m] this should be the length between cars when they are stopped.
intersection/stuck_vehicle_ignore_dist	double	[m] obstacle stop max distance(5.0m) + stuck vehicle size / 2 (0.0m-)
intersection/stuck_vehicle_vel_thr	double	[m/s] velocity below 3[km/h] is ignored by default
intersection/intersection_velocity	double	[m/s] velocity to pass intersection. 10[km/h] is by default
intersection/intersection_max_accel	double	[m/s^2] acceleration in intersection
intersection/detection_area_margin	double	[m] range for expanding detection area
intersection/detection_area_length	double	[m] range for lidar detection 200m is by default
intersection/detection_area_angle_threshold	double	[rad] threshold of angle difference between the detection object and lane
intersection/min_predicted_path_confidence	double	[-] minimum confidence value of predicted path to use for collision detection
collision_start_margin_time	double	[s] margin time before objects enter intersection lane
collision_end_margin_time	double	[s] margin time after objects exit intersection lane
merge_from_private_road/stop_duration_sec	double	[s] duration to stop

Flowchart

NOTE current state is treated as STOP if is_entry_prohibited = true else GO

CrossWalk

Role

Judgement whether a vehicle can go into a crosswalk and plan a velocity of the start/stop.

Launch Timing

Launches when there is a crosswalk on the target lane.

Module Parameters

Parameter	Type	Description
crosswalk/stop_line_distance	double	[m] make stop line away from crosswalk when no explicit stop line exists
crosswalk/stop_margin	double	[m] a margin that the vehicle tries to stop before stop_line
crosswalk/slow_margin	bool	[m] a margin that the vehicle tries to slow down before stop_line
crosswalk/slow_velocity	double	[m] a slow down velocity
crosswalk/stop_dynamic_object_prediction_time_margin	double	[s] time margin for decision of ego vehicle to stop or not
walkway/stop_line_distance	double	[m] make stop line away from crosswalk when no explicit stop line exists
walkway/stop_margin	double	[m] a margin that the vehicle tries to stop before walkway
walkway/stop_duration_sec	double	[s] time margin for decision of ego vehicle to stop

Flowchart

flow chart is almost the same as stop line.

Detection Area

Role

If pointcloud is detected in a detection area defined on a map, the stop planning will be executed at the predetermined point.

Launch Timing

Launches if there is a detection area on the target lane.

Algorithm

1. Gets a detection area and stop line from map information and confirms if there is pointcloud in the detection area
2. Inserts stop point l[m] in front of the stop line
3. Inserts a pass judge point to a point where the vehicle can stop with a max deceleration
4. Sets velocity as zero behind the stop line when the ego-vehicle is in front of the pass judge point
5. If the ego vehicle has passed the pass judge point already, it doesn’t stop and pass through.

Module Parameters

Parameter	Type	Description
stop_margin	double	[m] a margin that the vehicle tries to stop before stop_line
use_dead_line	bool	[-] weather to use dead line or not
dead_line_margin	double	[m] ignore threshold that vehicle behind is collide with ego vehicle or not
use_pass_judge_line	bool	[-] weather to use pass judge line or not
state_clear_time	double	[s] when the vehicle is stopping for certain time without incoming obstacle, move to STOPPED state

Flowchart

Blind Spot

Role

Blind spot check while turning right/left by a dynamic object information, and planning and planning of a velocity of the start/stop.

Definition

Sets a stop line, a pass judge line, a detection area and conflict area based on a map information and a self position.

• Stop line : Automatically created based on crossing lane information.

• Pass judge line : A position to judge if stop or not to avoid a rapid brake.

• Detection area : Right/left side area of the self position.

• Conflict area : Right/left side area from the self position to the stop line.

Module Parameters

Parameter	Type	Description
stop_line_margin	double	[m] a margin that the vehicle tries to stop before stop_line
backward_length	double	[m] distance from closest path point to the edge of beginning point.
ignore_width_from_center_line	double	[m] ignore threshold that vehicle behind is collide with ego vehicle or not
max_future_movement_time	double	[s] maximum time for considering future movement of object

Flowchart

Occlusion Spot

Role

This module plans safe velocity to slow down before reaching collision point that hidden object is darting out from occlusion spot where driver can't see clearly because of obstacles.

Occlusion Spot Private

This module only works in private road and use occupancy grid map to detect occlusion spots.

Occlusion Spot Public

This module only works in public road and use dynamic objects to detect occlusion spots.

Considering all occupancy grid cells inside focus range requires a lot of computation cost, so this module ignores to search farther occlusion spot which is longitudinally or laterally slice once occlusion spot is found.

Definition

This module insert safe velocity at collision point and show virtual wall at intersection below.

Module Parameters

Parameter	Type	Description
pedestrian_vel	double	[m/s] maximum velocity assumed pedestrian coming out from occlusion point
safety_time_buffer	double	[m/s] time buffer for the system delay

Parameter /threshold	Type	Description
detection_area_length	double	[m] the length of path to consider occlusion spot
stuck_vehicle_vel	double	[m/s] velocity below this value is assumed to stop
lateral_distance	double	[m] maximum lateral distance to consider hidden collision

Parameter /(public or private)_road	Type	Description
min_velocity	double	[m/s] minimum velocity to ignore occlusion spot
ebs_decel	double	[m/s^2] maximum deceleration to assume for emergency braking system.
pbs_decel	double	[m/s^2] deceleration to assume for predictive braking system

Parameter /sidewalk	Type	Description
min_occlusion_spot_size	double	[m] the length of path to consider occlusion spot
focus_range	double	[m] buffer around the ego path used to build the sidewalk area.

Parameter /grid	Type	Description
free_space_max	double	[-] maximum value of a free space cell in the occupancy grid
occupied_min	double	[-] buffer around the ego path used to build the sidewalk area.

Flowchart

No Stopping Area

Role

This module plans to avoid stop in 'no stopping area`.

ModelParameter

Parameter	Type	Description
state_clear_time	double	[s] time to clear stop state
stuck_vehicle_vel_thr	double	[m/s] vehicles below this velocity are considered as stuck vehicle.
stop_margin	double	[m] margin to stop line at no stopping area
dead_line_margin	double	[m] if ego pass this position GO
stop_line_margin	double	[m] margin to auto-gen stop line at no stopping area
detection_area_length	double	[m] length of searching polygon
stuck_vehicle_front_margin	double	[m] obstacle stop max distance

Flowchart