Adaptive Front Lighting System (AFS)
ADAPTIVE FRONT LIGHTING SYSTEM (AFS)
Xenon Headlamp Assembly with AFS
The AFS is a new system to improve driver visibility under differing driving conditions. AFS provides a larger visible area which is illuminated when cornering by adjusting the position of the beam distribution on the road. Horizontal adjustment is made automatically to the most suitable orientation for the driving conditions using steering angle and information from other vehicle sensors.
AFS is only available with xenon headlamps and also includes the dynamic headlamp levelling system described in the 'Headlamp Levelling' section of this document. The bi-xenon module within the headlamp is controlled by actuator motors which rotate the projector module on its vertical and horizontal axes to adjust the beam output to suit the cornering conditions and vehicle inclination. Only the bi-xenon lamp projector module swivels, the halogen high beam lamp unit remains static.
The AFS system is controlled by an AFS control module which is located at the bottom of the 'A' pillar, behind the CJB. The control module controls the vertical and horizontal alignment of the xenon projector module and the operation of the static bending lamp which is requested by the AFS control module but controlled by the CJB.
AFS Concept
AFS Control Module
The AFS control module is a dual functionality unit which also incorporates software to control the dynamic headlamp levelling. The AFS control module is connected to the high speed CAN bus and receives inputs from other vehicle systems on the status of the following parameters:
^ Steering angle
^ Vehicle speed
^ Headlamp status
^ Engine running
^ Reverse gear selected
^ Automatic lighting on.
The AFS will only operate when the AFS control module receives an engine running signal on the CAN bus. When the engine running signal is received and the lighting control switch is in the headlamps position, the AFS control module performs an initialisation routine.
The AFS will also function when the lighting control switch is in the AUTO position and the AFS control module receives a lights on signal from the rain/light sensor and an engine running signal.
The AFS control module then monitors the inputs from the other vehicle systems to control the AFS functionality according to cornering angles and vehicle speed.
AFS Control Module Connector C2193 Pin Details
AFS Control Module Connector C2193 Pin Details:
Operating Modes
The AFS has three modes of operation:
^ Manoeuvring mode
^ Normal driving mode
^ High speed mode
^ Reverse mode.
Manoeuvring mode is used for speeds up to 18.6 mph (30 km/h). Manoeuvring mode only moves the xenon projector module on the side of the vehicle towards the direction of turn, e.g. Left hand projector module moves to the left during a left hand turn. The opposite projector module is fixed and does not move. This mode allows the maximum amount of swivel range of the projector module to 15 °.
Normal driving mode is used for speeds between 18.6 and 43.5 mph (30 and 70 km/h). Normal driving mode moves both xenon projector modules at a ratio of 3:1, e.g during a left hand turn, the left hand projector module moves 3 ° and the right hand projector module moves 1 degree. This mode allows the maximum amount of swivel range of the projector module in the direction of the turn to 12 °.
High speed mode is used for speeds above 43.5 mph (70 km/h). High speed mode moves both xenon projector modules at a ratio of 3:1, e.g during a left hand turn, the left hand projector module moves 3 ° and the right hand projector module moves 1 degree. This mode allows the maximum amount of swivel range of the projector module in the direction of the turn to 10 °.
Reverse mode disables the swivel function when reverse gear is selected. The AFS projector modules move to their central straight ahead position and the static bending lamp, if active, will go off. When reverse gear is deselected, the AFS projector modules will move to a position to match the steering angle and the static bending lamp will illuminate if the operating conditions are correct (i.e. vehicle speed above 1.86 mph (3 km/h).
Xenon Headlamp Assembly with AFS Construction
The AFS xenon headlamp construction is similar to the non-AFS xenon headlamp assembly. The AFS assembly contains an additional carrier frame which provides the location for the AFS components. The remaining lamps are as described previously for the Xenon headlamp assembly. The functionality of the static bending lamp on the AFS headlamp is different from the functionality of the cornering lamp on the xenon headlamp.
The carrier frame has a radial bearing at the top and a thrust washer at the bottom which provide the horizontal pivot points for the xenon projector module. The lamp module lower pivot has a splined end which locates in the mating splines of the AFS horizontal actuator motor. The carrier frame is suspended on two flexible mountings at the top which provide for the vertical pivot points for the xenon projector module which allow for the vertical adjustment of the projector module. The bottom of the carrier frame is attached to the AFS vertical actuator motor.
The AFS actuator motors are DC motors which are driven by a power output from the AFS control module. The AFS control module also provides the earth path for the motor.
The actuators contain a potentiometer which is connected via wires with gold plated connector pins to the AFS control module. The two wires to each actuator provide a feedback signal to the AFS control module to give the precise position of the xenon projector module.
The AFS control module receives front and rear suspension height data to provide dynamic headlamp levelling adjustment via the vertical actuator motor. The AFS control module also receives vehicle speed signals from the ABS module to adjust the projector module vertically to increase the beam range as the vehicle speed increases.
Initialisation Procedure
When the AFS control module receives an ignition on signal, the control module performs the initialisation procedure which ensures that the headlamps are correctly aligned on both their vertical and horizontal axes.
The headlamp levelling initialisation takes less than 3 seconds to complete. The headlamp levelling motors are powered from their current position, which can be either the upper or lower limit or somewhere in between, to their lower position and then back to the 0 ° position.
The AFS swivel initialisation starts less than 1 second after the headlamp levelling initialisation is activated to ensure that the headlamps are at or below the 0 degree position in the vertical axis, thus preventing glare to oncoming vehicles. The AFS swivel initialisation is completed in less than 2.5 seconds. The LH and RH AFS actuator motors are powered from the 0 degree position to their fully inboard position, then to their fully outboard position and then back to the 0 degree position.
Failure Mode
In the event of a failure of the AFS system, a warning indicator in the instrument cluster is illuminated to warn the driver. The AFS warning indicator illuminates when the ignition switch is in the ignition position (II) and will illuminate continuously until the fault is rectified. The AFS warning indicator will also be illuminated if a failure of the steering angle sensor or the vehicle speed signal is detected.
Illumination of the AFS warning indicator does not necessarily mean that there is a fault with the AFS system. The fault may be caused by a failure of another system preventing the AFS system operating correctly.
The AFS control module performs a diagnostic routine every time AFS is requested. If any fault is found, the AFS control module will suspend the operation of the AFS function.
If the AFS system has failed with the xenon projector module in a position other than the correct straight ahead position, the AFS control module will attempt to drive the xenon projector module to the zero (straight ahead) position. If this is not possible, the AFS control module will lower the projector module using the levelling actuator motors to prevent excess glare to oncoming vehicles.
The AFS control module software can detect an internal failure of the control module control circuits. The control module will power the projector modules to the zero position and prevent further operation.
Faults can be investigated by interrogating the AFS control module using T4 to check for fault codes.
Static Bending Lamps
NOTE: The static bending lamps are not fitted to NAS market vehicles
The static bending lamps are a standard feature on AFS headlamps designed to illuminate the direction of travel when cornering at low speeds. The design of the lens projects a spread of light from the vehicle at approximately 45 ° to the vehicle axis. The static bending lamps are controlled by the CJB.
The static bending lamp is incorporated into the outer part of the headlamp assembly and shares the same housing and reflector as the side lamp.
The static bending lamp uses a 35W Halogen H8 bulb which locates in a holder which is connected via wires to the main connector on the headlamp housing. The holder is located in an aperture in the headlamp housing and rotated to lock. The bulb is accessible via a removable cover at the rear of the headlamp housing.
AFS Control
The static bending lamps operate with a steering angle sensor signal which is received by the AFS control module and the CJB. The AFS control module sends a static bending lamp on request to the CJB which activates the static bending lamp bulb.
At speeds above 30 mph (48 km/h), the static bending lamp in the direction of the turn is illuminated when the steering wheel rotation reaches 70 °. As the vehicle turn is decreased, the static bending lamp is switched off when the steering wheel rotation reaches 50 °.
At speed below 30 mph (48 km/h), the static bending lamp in the direction of the turn is illuminated when the steering wheel rotation reaches 245 °. As the vehicle turn is decreased, the static bending lamp is switched off when the steering wheel rotation reaches 225 °.
The operation of the static bending lamps is controlled by the CJB. When the operation parameters of the lamp are reached, the CJB fades the static bending lamp bulb on using a PWM voltage over a period of approximately 2 seconds. When the lamp is switched off, the CJB fades the bulb off by decreasing the PWM voltage.