BMW 7 Series: Zero Position Sensor

The zero position of the swivel module with respect to the zero position sensor is detected by a 1/0 edge when swivelling from the direction of the off position in the direction of the optical axis. The swivel module is repeatedly calibrated during operation based on this "soft" reference point.

Fig. 58: Zero Position Sensor Detection Range

COMPONENTS DESCRIPTION CHART

1. Mechanical stop, minimum
2. Electrical stop
3. OFF position
4. Position of zero position sensor
5. Position of optical axis = 0
6. Electrical stop, maximum
7. Mechanical stop
8. Swivel direction
9. Reference run from left

Driving the stepper motor in positive direction of the swivel module corresponds to swivel movement to the right.

Mechanical Stop

Items 1 and 7 represent the mechanical stops of the swivel module. The mechanical stops are defined by the design of the headlights.

Differential Angle

A differential angle is required when the position of the swivel module is not known. A reference run that extends to the mechanical stops must be performed for this purpose. This is known as a "hard" reference run.

Optical Axis

The swivel position, in which the swivel module is in the straight-ahead direction of the vehicle is referred to as the optical axis. An angle of 0º is assigned to this position.

The optical axis is defined exactly as an angle with respect to the zero position sensor and as an angle with respect to the mechanical stop.

Consequently, the optical axis during swivel movement can be "normally" determined by way of the zero position sensor.

The differential angle with respect to the mechanical reference point is used in the case of fault.

Swivel Range Normally, the swivel module does not move to the mechanical stop but rather to the electric minimum and maximum stops.

Adjustment of the swivel module to the electrical stops avoids the loss of pulses on reaching a mechanical stop.

The minimum and maximum electrical stops are defined as angles with respect to the zero position.

NOTE: The panning ranges define the maximum pan angles that the adaptive headlights can utilize.

Panning, raising and lowering headlights

Via the LIN bus the footwell module instructs the headlight driver modules to actuate the respective stepper motors.

The headlight driver modules activate the stepper motors for panning. For the variable headlight beam pattern, the headlight driver modules also actuate the stepper motors to raise or lower the headlights. The maximum adaptive headlight panning range must not be exceeded when cornering. This must also be considered for the variable beam pattern headlights.

The off-side headlight requires a certain outward pan angle combined with a certain amount of lowering according to the headlight beam pattern.

The outward pan angle must be subtracted from the adaptive headlight pan angle for left-hand bends.

The table below shows which headlights are moved to set the various headlight beam patterns. The first example illustrates the situation for movement when driving in a straight line.

Driving in a straight line, left-hand drive vehicle

LIGHT FUNCTIONS

The angles quoted relate to headlights in the straight-ahead position!

Example for left-hand bend

When the urban beam pattern is active, the off-side headlight pans approximately 12º outwards. At the same time, the headlight is slightly lowered. Since, a panning range of up to 15º is available for left-hand bends, only 3º more is left for corner illumination.

Example for right-hand bend

When the urban beam pattern is active, the off-side headlight pans approximately 12º outwards. At the same time, the headlight is slightly lowered. For a right-hand bend a panning range of 8º is available. The headlight pans the full 8º.

Traverse Rate

The traverse rate of the swivel modules is up to 30º/second.

Swiveling

The following signals are made available to the footwell module for the purpose of moving the swivel module.

• Steering angle
• Road speed
• Yaw rate.

Under normal driving conditions, the adaptive headlight is controlled by the data from the steering angle sensor up to a speed of approximately 40 kph (25mph).

Fig. 59: Input Signals In E90

COMPONENTS DESCRIPTION CHART

1. Vehicle speed
2. Steering angle
3. Yaw rate

The yaw rate sensor is included in the calculation

• at speeds higher than approximately 40 km/h (25 mph)
• in the event of vehicle oversteering or understeering
• a vehicle tending to yaw.

The wheel speed sensors supply the signals for the vehicle speed. The dynamic stability control evaluates the wheel speed sensor of each wheel.

The vehicle oversteering/understeering or yawing is detected by means of the steering angle sensor and the yaw rate sensor.

The adaptive headlight is deactivated in the event of the vehicle oversteering/understeering or yawing. The swivel module returns to its zero position.

NOTE: The yaw rate sensor makes available signals relating to the yaw of the vehicle about the vertical axis. It is installed between the driver's and front passenger seats on the transmission tunnel.

The steering angle sensor is integrated in the steering column switch cluster. It is an optical sensor and makes available data relating to the steering wheel lock angle.

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