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System Description

  1. PRE-COLLISION SAFETY SYSTEM 
    1. The pre-collision safety system optimizes the occupant protection equipment (seat belt) and activates related systems to reduce damage from the collision.
    2. Operation pattern and each operation of pre-collision safety system
    PRE-COLLISION SAFETY SYSTEM OPERATION PATTERN

    Operation pattern Control Transmitting ECU Receiving ECU Part operated
    Operate with sensor Pre-collision seat belts Cruise control ECU assy (Distance control ECU) Seat belt control ECU Front seat outer belts
    Operate with sensor Pre-collision brake assist Cruise control ECU assy (Distance control ECU) ABS & Traction actuator assy (Skid control ECU) Brake assist system
    Operate with sensor Damping force control Cruise control ECU assy (Distance control ECU) Suspension control ECU Shock absorbers
    Operate with sudden braking Pre-collision seat belts ABS & Traction actuator assy (Skid control ECU) Seat belt control ECU Front seat outer belts
    1. Operation when operating with sensor

      The pre-collision sensor (millimeter wave radar sensor) detects vehicles or other objects on the road in front. The cruise control ECU assy (distance control ECU) determines in advance that a collision is unavoidable based on object position, speed and track information. The cruise control ECU assy (distance control ECU) transmits unavoidable collision information through CAN communication. The seat belt control ECU receives the signal (from the cruise control ECU assy (distance control ECU)) and initiates control of the pre-collision seat belts. The ABS & Traction actuator assy (skid control ECU) also receives unavoidable collision information from the cruise control ECU assy (distance control ECU) and activates the pre-collision brake assist system. The suspension control ECU also receives unavoidable collision information and hardens the suspension as much as possible.

    2. Operation when operating with sudden braking

    The ABS & Traction actuator assy (skid control ECU) determines when the driver brakes suddenly according to brake pressure information, etc. The ABS & Traction actuator assy (skid control ECU) sends the operation demand signal to the seat belt control ECU through CAN communication and activates the pre-collision seat belt.

  2. OUTLINE OF PRE-COLLISION SEAT BELT CONTROL 
    1. The pre-collision seat belt operates with the sensor or sudden braking. The pre-collision seat belt motor tightens the seat belt to optimize occupant restraint performance.
    2. Operative condition
    1. When operating with sensor: The pre-collision sensor (millimeter wave radar sensor) detects objects and the cruise control ECU assy (distance control ECU) determines that a collision is unavoidable.
    2. When operating with sudden braking: The driver brakes suddenly and the ABS & Traction actuator assy (skid control ECU) determines it as sudden braking.
    3. The operation demand signal is received using a hand-held tester.
  3. OUTLINE OF PRE-COLLISION BRAKE ASSIST SYSTEM 
    1. The pre-collision brake assist system operates with the sensor and enters standby mode before a collision. Brake fluid pressure is increased to simultaneously improve fluid pressure response and reduce vehicle speed when the driver depresses the brake pedal.
    2. Operative condition
    1. When the driver depresses the brake pedal after the cruise control ECU assy (distance control ECU) determines that a collision is unavoidable:

      Brake fluid pressure is increased at the same time that the driver depresses the brake pedal after the pre-collision sensor (millimeter wave radar sensor) detects possible collision objects and the cruise control ECU assy (distance control ECU) determines that a collision is unavoidable.

    2. When the driver depresses the brake pedal before the cruise control ECU assy (distance control ECU) determines that a collision is unavoidable:

    Brake fluid pressure is increased at the same time that the cruise control ECU assy (distance control ECU) receives the information of an unavoidable collision after the pre-collision sensor (millimeter wave radar sensor) detects possible collision objects.

  4. OUTLINE OF DAMPING FORCE CONTROL 
    1. The damping force control operates with the sensor, and the suspension is hardened as much as possible to reduce damage from the collision.
    2. Operative condition
    1. The pre-collision sensor (millimeter wave radar sensor) detects possible collision objects, and the cruise control ECU assy (distance control ECU) determines that a collision is unavoidable.
  5. OPERATIVE CONDITION AND INOPERATIVE CONDITION OF EACH CONTROL (REVIEW) 
    OPERATIVE AND INOPERATIVE CONDITION TABLE

      Pre-collision seat belts ((1)) Pre-collision seat belts ((2)) Pre-collision brake assist ((2)) Damping force control ((2))
    Ignition switch is in LOCK or ACC position. - - - -
    When a warning message is displayed on the multi-information display. ((3)) (4) (4) (4) (4)
    When seat belt(s) is/are fastened. (5) (5) O O
    Operates when own vehicle speed is 30 km/h or more, regardless of relative speed. O - - -
    Operates when own vehicle speed is 5 km/h or more and relative speed is 30 km/h. - O O O
    When the vehicle collides with an object outside the detection range of the millimeter wave radar sensor (side collision, rear collision, etc.). ((6) - - -
    When the millimeter wave radar sensor can not detect a possible collision object. ((6) - - -
    (1) Operates with sudden braking
    (2) Operates with sensor
    (3) Fail-safe function (see FAIL-SAFE CHART  )
    (4) Inoperative parts are different depending on malfunction areas
    (5) Only the fastened seat belt side operates
    (6) Pre-collision seat belts that operate with sudden braking may operate when the brakes are suddenly applied.
  6. PRECAUTION FOR PRE-COLLISION SAFETY SYSTEM OPERATION 
    1. When the millimeter wave radar sensor detects an object in front under the conditions described below, the cruise control ECU assy (distance control ECU) may determine that a collision is unavoidable, and operate the pre-collision safety system. However, this is not abnormal.
    Fig 1: Identifying Pre-Collision Safety System Operation Precautions
    G03002631Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    HINT:

    The millimeter wave radar sensor might not be able to detect the following objects as collision objects:

    COLLISION OBJECTS - REFERENCE TABLE

    Objects that cannot be detected Plastic items (Safety Cones, etc.), etc.
    Objects that cannot be detected in a stable manner People, Bicycles, Motorcycles, Trees, Animals, Snow fence, etc.
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