PRE-CRASH SAFETY SYSTEM(w/ Driver Monitor Camera)

Loss of Vehicle Control

Sudden Braking

Pre-crash Intelligent Headrest Control

1. The diagram below shows the flow of the activation of the systems during a pre-crash intelligent headrest operation:

   

2. Operation

   (1)	The driving support ECU assembly determines that a collision with a vehicle approaching from behind is unavoidable using the signals received from the following sensors: rear millimeter wave radar sensor assembly, speed sensor (skid control ECU assembly) and yawrate sensor.
   (2)	At this time, the driving support ECU assembly transmits a pre-crash intelligent headrest operation signal to the pre-crash intelligent headrest ECU.
   (3)	The pre-crash intelligent headrest ECU operates a motor that is built into the pre-crash intelligent headrest in order to move the front surface of the headrest forward and upward.
   (4)	As the front surface of the headrest moves forward and upward, the head position detection sensor that is built into the pad detects the electrostatic capacity between the headrest and the head of the driver or front passenger. Then, the sensor transmits this information to the pre-crash intelligent headrest ECU.
   (5)	The pre-crash intelligent headrest ECU determines the distance between the front surface of the headrest and the head of the driver or front passenger based on the electrostatic capacity transmitted by the head position detection sensor. Then, the pre-crash intelligent headrest ECU stops the front surface of the headrest in preparation for the rear-end collision.
   (6)	The pre-crash intelligent headrest ECU maintains the position of the front surface of the headrest for approximately 0.9 seconds in preparation for the rear-end collision. After that, the pre-crash intelligent headrest ECU operates the motor inside the pre-crash intelligent headrest to retract the front surface of the headrest.

   

Opening or Closing of Eyelids and Face Direction Determination

1. On models with a driver monitor camera, if the driver monitor ECU assembly detects that the driver is not facing forward or does not have eyelids open, a warning is emitted by the driving support ECU assembly.

2. After the warning, if the driver's condition has not changed, the driving support ECU assembly activates the warning brake operation.*

   
   

   • *: The object targeted as a potential collision is the vehicle ahead.

   

Rear Millimeter Wave Radar Sensor Assembly

1. The rear millimeter wave radar sensor assembly consists of a rear millimeter wave radar circuit, signal processing circuit and CPU.

2. The rear millimeter wave radar circuit consists of an antenna (used for both transmission and reception) and reception antennas.

3. The rear millimeter wave radar sensor assembly uses frequencies in the 76 GHz band.

4. The reception antennas receive the millimeter wave radar waves that have been reflected.

5. The signal processing circuit detects the distance, relative speed and the direction of the object by generating millimeter wave radar waves and calculating the signals received by the reception antennas. Then, the signal processing circuit transmits this information to the driving support ECU assembly.

   

   Text in Illustration

   *1	Rear Millimeter Wave Radar Sensor Assembly	-	-
   *a	Detection Distance: Approx. 1.6 to 31 m (5.2 to 101.7 ft.)	*b	Horizontal Angle: Approx. 30°
   *c	Vertical Angle: Approx. 4°	*d	Signal Processing Circuit
   *e	Rear Millimeter Wave Radar Circuit	-	-

6. The distance to the object, azimuth (horizontal angle) and relative speed are calculated from the information that is provided by the reflection millimeter wave radar as described below:

   Item	Calculation Method
   Distance	Calculated from the length of time that has elapsed from the time the waves of the rear millimeter wave radar sensor assembly have been emitted, until the waves reflected by the rear millimeter wave radar are received. The detection distance is approx. 1.6 to 31 m (5.2 to 101.7 ft.).
   Azimuth	Calculated from the angle of the waves reflected by the rear millimeter wave radar sensor assembly that have been received. The detection angle has a horizontal angle of approx. 30° and a vertical angle of approx. 4°.
   Azimuth	Calculated by utilizing the changes (Doppler effect*) that occur in the frequencies of the reflected millimeter wave radar waves.

   Tech Tips

   *: The Doppler effect causes the observer to perceive the radio waves emitted by a moving object to be of higher frequencies as it approaches, and to be of lower frequencies as it recedes.

   

Near-infrared Projector

1. The near-infrared projector radiates near-infrared rays forward in order to enable the object recognition camera to capture the image of the objects even at night.

2. The near-infrared projector is built into the high beam units of the headlight assemblies.

3. When the conditions indicated below are met, the object recognition ECU transmits a near-infrared illumination request signal to the front controller (multiplex network front light ECU) via the driving support ECU assembly.

   
   

   • The engine switch is on (IG).

   • The low beam headlights are on.

   • The light control sensor on the automatic light control system has determined that the surroundings of the vehicle have become dark.

   • The vehicle is being driven [15 km/h (10 mph) minimum]. However, the near-infrared projector turns off when the vehicle comes to a stop [10 km/h (6 mph) maximum].

   

   Text in Illustration

   *1	Object Recognition Camera	-	-
   *a	Near-infrared Rays	*b	Reflected Rays

4. On except models for China, each high beam unit of the headlights contains a retractable, visible rays cut filter. To serve as an ordinary high beam headlight to radiate visible rays, the visible rays cut filter is retracted. To radiate near-infrared rays, the visible rays cut filter is upright. The light from the bulb passes through the visible rays cut filter so that only the near-infrared rays are emitted. Because the center of the visible rays cut filter forms a prism, the light that passes through the visible rays cut filter diffuses wider than an ordinary high beam headlight. The amount of the radiated energy is also the same as that of a hi beam headlight. This construction enables the system to capture a field of vision that is farther than that of the low beam headlights.

5. On models for China, each near-infrared projector of the headlight assembly contains a visible ray cut filter. The light from the bulb passes through the visible ray cut filter so that only the near-infrared rays are emitted. Because the center of the visible ray cut filter forms a prism, the light that passes through the visible ray cut filter diffuses wider than an ordinary headlight units. This construction enables the system to capture a field of vision that is farther than that of the low beam headlight units.

6. These projectors emit weak visible rays around the lens of the projectors.

   

   Text in Illustration

   *A	Except Models for China	*B	Models for China
   *1	Lens	*2	Hi Beam/Near Infrared Rays Switching Solenoid
   *3	Visible Rays Cut Filter	*4	Bulb
   *a	Near-infrared Rays	*b	Visible Rays
   *c	Operating as Hi Beam	*d	Operating as Infrared Projector

   Note

   The near-infrared projector emits weak visible rays when the near-infrared rays is emitted. However, do not look directly into the headlight assembly near-infrared projector unit for long time because they radiate the same amount of energy as the high beam headlight.

Object Recognition Camera

1. The object recognition camera consists of 2 cameras that are placed side-by-side in the center front area of the vehicle's roof headlining. Because these 2 cameras capture the reflected rays of the near-infrared projectors that are built into the headlight assembly, they can capture images even at night.

2. The 2 cameras of the object recognition camera capture an object and transmit the left and right image signals to the object recognition ECU. The object recognition ECU processes those images to detect a three-dimensional form and detects the parallax to calculate the distance to the object.

   

   Text in Illustration

   *1	Object Recognition Camera	*2	Lens
   *3	Visible Rays Cut Filter	*4	Charge Coupled Devices (CCD)
   *5	Object Recognition ECU	-	-
   *a	Near-infrared Rays	*b	Visible Rays
   *c	Image Data	-	-

3. The forward field of vision of the object recognition camera is within the range of approximately 45 degrees of the horizontal field angle and approximately 35 degrees of the vertical field angle.

   

   Text in Illustration

   *1	Object Recognition Camera	-	-
   *a	Approx. 45°	*b	Approx. 35°

Driver Monitor Camera

1. The driver monitor camera, which is mounted on the steering column, monitors the driver's face and eyelids, and transmits image data to the driver monitor ECU assembly.

2. The 2 near-infrared lights that are built into the driver monitor camera illuminate the driver's face and eyelids. Then, the reflected light consists primarily of near-infrared rays after it passes through the exterior light-receiving surface (which is made of a material that suppresses the transmission of visible rays). The CCD receives the reflected light, thus enabling the monitoring of the driver's face and eyelids even in the dark.

3. The 2 near-infrared lights that are built into the driver monitor camera illuminate the driver's face when the system is turned on.

   

Driver Monitor ECU Assembly

1. The driver monitor ECU assembly calculates the direction of the driver's face in accordance with the width of the face and the position of the eyes and the mouth, and calculates the open or close condition of the driver's eyelids in accordance with the width of the upper and lower line of eyes, found in the image data received from the driver monitor camera. Then, it transmits a face direction and eyelids open or close condition detection signal to the driving support ECU assembly.

   

Pre-crash Intelligent Headrest

1. If the rear millimeter wave radar sensor assembly has determined the possibility of being rear-ended, the front surface of the pre-crash intelligent headrest moves forward and upward. This shortens the distance between the headrest and the head of the driver or front passenger, thus lessening the neck injury sustained by the occupant.

   

   Text in Illustration

   *1	Pre-crash Intelligent Headrest	-	-
   *a	Normal Driving	*b	Unavoidable

2. The driver and front passenger seats are equipped with the pre-crash intelligent headrests. The pre-crash intelligent headrest consists of a head position detection sensor, pre-crash intelligent headrest ECU, link mechanism and electric motor.

3. The pre-crash intelligent headrest ECU operates the electric motor to actuate the link mechanism, causing the front part of the headrest to move forward and upward. The maximum movable distance is 60 mm (2.4 in.) forward and 25 mm (1 in.) upward.

4. The head position detection sensors are located in the headrest pads. The sensors detect the positions of the driver's and front passenger's heads using changes in electrostatic capacity* between the head and headrest. When a rear collision is determined to be unavoidable, each built-in head position detection sensor commences detecting the driver's and front passenger's head positions. When a seat is unoccupied, the front part of the relevant headrest moves to its maximum distance, and then comes to a stop. When a seat is occupied, the front part of the relevant headrest moves until it makes contact with the head.

   Tech Tips

   *: The capacity of an object to store an electric charge. The unit used to represent this capacity is F (Farad).

   

   Text in Illustration

   *1	Head Position Detection Sensor	*2	Pre-crash Intelligent Headrest ECU
   *3	Link Mechanism	*4	Motor
   *a	A - A Cross Section	-	-