Blind Spot

Role

Blind spot module checks possible collisions with bicycles and pedestrians running on its left/right side while turing left/right before junctions.

Activation Timing

This function is activated when the lane id of the target path has an intersection label (i.e. the turn_direction attribute is left or right).

Inner-workings / Algorithms

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.

Stop/Go state: When both conditions are met for any of each object, this module state is transited to the "stop" state and insert zero velocity to stop the vehicle.

• Object is on the detection area
• Object’s predicted path is on the conflict area

In order to avoid a rapid stop, the “stop” judgement is not executed after the judgment line is passed.

Once a "stop" is judged, it will not transit to the "go" state until the "go" judgment continues for a certain period in order to prevent chattering of the state (e.g. 2 seconds).

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
adjacent_extend_width	double	[m] if adjacent lane e.g. bicycle only lane exists, blind_spot area is expanded by this length

Flowchart

@startuml
title modifyPathVelocity
start

if (ego is turning right or left ?) then (yes)
else (no)
  stop
endif

:calculate pass judge Line;

if (ego vehicle is not after pass judge line?) then (yes)
else (no)
  stop
endif

:check obstacle in blind spot;

if (obstacle found in blind spot?) then (yes)
  :set current state as STOP;
else (no)
  :set current state as GO;
endif

:set state with margin time;

if (current state is same as previous state) then (yes)
  :reset timer;
else if (state is GO->STOP) then (yes)
  :set state as STOP;
  :reset timer;
else if (state is STOP -> GO) then (yes)
  if (start time is not set) then (yes)
    :set start time;
  else(no)
   :calculate duration;
   if(duration is more than margin time)then (yes)
    :set state GO;
    :reset timer;
   endif
  endif
endif


if (state is STOP) then (yes)
  :set stop velocity;

  :set stop reason and factor;
endif

stop
@enduml