Bi-Xenon Headlights
Bi-Xenon Headlights
The dynamic cornering light is new for Bi-Xenon headlights (standard for Cayenne Turbo, optional for Cayenne and Cayenne S). In addition to the existing static cornering light, which is particularly useful when turning, the dynamic cornering light provides better illumination of corners on the road, e.g. when driving cross country. Neither the static nor the dynamic cornering light is active when driving straight ahead. A sharp turn of the steering wheel activates the static cornering light while driving (up to max. 80 mph (130 km/h) ) and when the vehicle is stationary.
Headlight Control Unit
NOTES: Headlight control units are not installed in vehicles with halogen headlights. Faults relating to halogen headlights are detected by the light master (vehicle electrical system control unit).
The headlight control unit only performs functions and supports the activation of required actuators in the headlight. The necessary data is provided via CAN or via a direct connection for the headlight control unit. The headlight control unit is not a "light master" and does not decide which light is switched "ON". The headlight control unit is connected to the vehicle electrical system control unit (light master) and the gateway control unit.
On vehicles with steel springs, the self-levelling sensors are connected directly to the headlight control unit. The headlight control unit is powered by the vehicle electrical system.
Headlight Control Unit Software
The two headlight control units in the vehicle work independently. Each headlight control unit has the individual software and hardware it requires for calculating the required parameters. During a service, headlight variant coding must be performed and parameters must be set using the PIWIS Tester.
The functions, such as automatic range adjustment, static cornering light and dynamic cornering light, are calculated in the headlight control unit and implemented by the connected bulbs/actuators. The light master (vehicle electrical system control unit) issues the command to switch on the lights.
Dipped Beam
The series reactor (ignition control unit) is integrated in the headlight control unit for the dipped beam function. The headlight control unit is hard wired to the vehicle electrical system control unit (light master). The series reactor (ignition control unit) can also be activated without the power supply (terminal 15) from the headlight control unit.
Diagnosis is performed when terminal 15 is switched on and when the lights are activated. The series reactor (ignition control unit) has a power monitoring and power control system. The headlight control unit sends its status bit to the CAN bus when dipped beam is "ON". This bit is monitored by the opposite headlight control unit. If a fault is detected, emergency mode is enabled and the message "Check dipped beam" appears on the on-board computer. The same happens if the headlight control unit intentionally switches off the dipped beam headlight because of a problem with the automatic range adjustment and dynamic cornering light functions (message displayed on on-board computer: "Automatic range adjustment failure" or "Cornering light failure").
NOTES: Diagnosis is performed by the vehicle electrical system control unit (light master).
High Beam, Auxiliary Main Beam, Headlight Flasher
The control motor for high beam activation is hard wired to the vehicle electrical system control unit (light master). The headlight control unit is not responsible for activating the high beam headlight in the headlight module variants.
The auxiliary main beam headlight is also activated by the vehicle electrical system control unit (light master) and its output cannot be regulated. The vehicle electrical system control unit (light master) activates the headlight flasher functions. The required bulbs and motors are activated directly for this purpose.
- Only the auxiliary main beam is activated when terminal 15 is "ON" and terminal 56b (dipped beam) is "OFF".
- The auxiliary main beam and the main beam magnet is activated when terminal 15 is "ON" and terminal 56b (dipped beam) is "ON".
- There is no headlight flasher function when terminal 15 is "OFF".
Cornering Light
We differentiate between the variants Static cornering light and Dynamic cornering light for the cornering light function. The driver's visible area is larger and this contributes further to improving active safety. The road is illuminated even better because the two light beams lie side-by-side and do not focus their light on one point. The headlight control unit has the relevant software for calculating the required parameters.
Static Cornering Light
The purpose of the static cornering light is to light up the adjacent area in front of and beside the vehicle with a large beam spread and homogeneous linking with the rays of light emerging from the main headlight. The headlight control unit calculates the required value for the static cornering light bulb from the input values received via the CAN bus.
The static cornering light, with a beam angle of approx. 30° with respect to the direction of travel (controlled by the steering angle), provides better illumination of the road in the direction of the steered corner (e.g. when turning) when the vehicle is stationary or when travelling at speed up to 80 mph (130 km/h).
The static cornering light is switched on if the following conditions are met:
- Dipped beam "ON" (via light switch) or the light sensor detects the need for lights "ON".
- Steering angle a(on) =2°.
- Speed-dependent.
- Terminal 15 analog and terminal 15 via CAN signal.
The static cornering light is switched off if one of the following conditions is met:
- Dipped beam "OFF".
- Steering angle a(off) =< 2°.
- Terminal 15 as CAN signal "OFF".
- Terminal 15 analog "OFF".
- High beam "ON".
Static cornering light control depends on the characteristics that were defined during the development phase. The static cornering light is switched on when there is a jump from 0 % to 30 % (U(eff jump)). The voltage is adjusted in a "ramp" from 30 % then to 100 % (U(eff jump)). Essentially, a steeper "ramp" (see Phase 4) is used for increasing the voltage. The voltage is reduced using a flatter "ramp" (see Phase 6).
The adjusting behaviour depends on the various signals:
- Steering angle
- Steering angle speed
- Vehicle speed
- Left/right direction indicator
- Reverse gear
NOTES: When setting the direction indicator light, the time "t(ON)" is reduced by a predefined factor.
Dynamic Cornering Light
The steering angle, vehicle speed and yaw rate serve as input values for controlling the dynamic cornering light, which is integrated in the Bi-Xenon light unit. This provides optimal illumination of the road during cornering. The course of the road and any obstacles are detected earlier. The dynamic cornering light is activated at speeds of 2 mph (3 km/h) or higher. The maximum adjustment angle of the headlight at the inside of the bend is 15°, while the value for the headlight at the outside of the bend is 7.5°.
NOTES: Activating the high beam switches the static cornering light off. In contrast, the dynamic cornering light remains active when travelling at 2 mph (3 km/h) or faster even when high beam is active. This improves visibility for the driver.
The dynamic cornering light is activated as soon as the following conditions are met:
- Dipped beam "ON" (via light switch) or
- the light sensor detects the need for lights "ON"" and
- vehicle speed > 2 mph (3 km/h),
- engine rpm > 600 rpm,
- positive feedback after referencing the stepper motors.
Stepper Motors (auto. range adjustment, dynamic cornering light)
Each stepper motor is connected to the headlight control unit via an interface. The headlight control unit calculates the required position into which the stepper motor must move, and sends this information to the stepper motor. If a stepper motor fails or malfunctions, a fault is stored in the fault memory and the relevant emergency operation function is initiated.
Each stepper motor is used for a different purpose:
- Stepper motor for automatic range adjustment.
- AFS stepper motor (dynamic cornering light).
During initialization, the headlight control unit checks the number of registered stepper motors. If a difference is detected, a fault is recorded.
NOTES: The power supply for the headlight control unit and stepper motors comes directly from a terminal 15 relay.
Automatic Range Adjustment
The automatic range adjustment function is integrated in the headlight control unit. The dynamic range adjustment system keeps the inclination of the light rays (dipped beam Bi-Xenon module and static cornering light) at the preset value of -1 % independently of the vehicle's load so that neither the vehicle's load nor the pitching movements resulting from the vehicle's driving dynamics can "blind" oncoming traffic when dipped beam is switched on, while at the same time ensuring an adequate range of vision for the driver.
NOTES: The system is adapted to the different types of vehicles by programming the vehicle specific parameters using the PIWIS Tester.
The system responds very quickly to braking or acceleration. The motor begins to adjust the headlights after commencement of the pitching movement. When the vehicle is stationary, the vehicle's inclination is calculated from the sensor signals and the headlight settings are corrected according to the difference between their required and actual positions. The full scope of functions is maintained when high beam is switched on. This results in increased driving safety while at the same time reducing the strain on the driver.
The following CAN signals are required for calculating automatic range adjustment and the functions of the actuators:
- Steering angle
- Yaw rate
- Left + right direction indicator
- Vehicle level, front + rear
- Wheel speed
- Motor operating status
- Dipped beam status
- Light sensor
- Brake light switch
- Reverse gear
- Synchronization data (from headlight control unit)
- Accelerator pedal
Based on these signals, a microprocessor controller calculates the vehicle's pitch angle and the required positions of the stepping motors in the headlight for the purposes of range adjustment.
NOTES: Vehicles with steel springs. In this case, the self-levelling sensors are read in directly by the left headlight control unit and the sensor values are transmitted to the right headlight control unit in the form of a CAN signal.
Automatic Range Adjustment - Poor Road Surface/Off-road Detection
The automatic range adjustment system includes a function for detecting poor road surfaces/off-road conditions, which counteracts the continual adjustment behavior by using a filter system that significantly reduces actuation of the stepping motors or shutting them down completely. Interfering signals which are superimposed over the sensor signals as a result of the road surface (bumps and pot holes) are filtered out while driving.
Automatic Range Adjustment - Chassis Variants
Two chassis variants are used in the Cayenne (steel spring and air suspension). Two automatic range adjustment variants (coding) are available due to the mechanical and electronic differences between the chassis variants. These are adapted specifically to suit the relevant chassis. The required parameters are assigned for all Cayenne models using the vehicle's required components list.
NOTES: Headlights, which are not yet operational (delivery status) and are used, operate in emergency mode will cause a fault to be entered in the fault memory of the headlight control unit "Control unit not coded" if terminal 56b is "OFF".