How It Works: Notes

Preconditions for the stepper motor controller to work are correct coding and correct pin assignment as follows:

• Coding: Headlight-specific data for the adaptive headlights are coded in the stepper motor controllers.
• Pin assignment: To differentiate between the installation location, pin 12 of the stepper motor controller (SMC) for the left-hand headlight must be connected to earth.

The stepper motor controller calculates the swivelling motion of the headlights for the adaptive headlights based on defined positions as follows:

• The stepper motor controller receives from the AHL control unit the position to which the headlight is to move (nominal value).
• The stepper motor control recognises the current position of "its" headlight, i.e. the one to which it is assigned (actual value).
• The stepper motor controller calculates the distance that the headlight must be moved (in steps). The stepper motor controller allows the stepper motor to turn as many steps as required until the headlights are in the correct position.

The defined positions, upon which the calculations are based, are checked each time the zero-position sensor is passed: the SMCs compare the calculated or driven-to zero to verify that the corresponding signal arrives from the zero-position sensor.

The output signal of the zero-position sensor is a level (depending on the degree of overlap of Hall sensor and sensor plate).

The output signal is either a high level signal or a low level signal. The level curve is illustrated in the following graphic:

Fig 1: Identifying Output Signal

Courtesy of BMW OF NORTH AMERICA, INC.