Vehicles with ESP

Task
The task of the steering angle sensor (N49), which works on an optical basis, is to record the steering angle specified by the driver and pass it on to connected systems.

Design
The steering angle sensor (N49) works in conjunction with the horn/airbag clock spring contact (A45). It is connected directly to the jacket tube module (N80).





Optical sensor with 6 light-emitting diodes (a) for photoelectric barrier measurement. The steering angle sensor consists of 2 microcomputers which form one unit together with a signal measuring arc. The 6 light-emitting diodes (a) are located at equal distances in the signal measuring arc and record an angle of 72°. They form a photoelectric barrier channel which is passed through by 5 groups of 3 different length apertures (b). The photoelectric barriers (a) are located in the steering angle sensor (N49) which is rigidly connected to the jacket tube module (N80). The apertures (b) are located in the moving upper section of the contact spiral (A45) and only form the complete functional unit of the optical steering angle sensor (N49) when both components are joined together.

Function
In the center position of the steering wheel the 15 apertures (b) assume a defined position relative to the 6 light-emitting diodes (a). This center position is recorded by the computer in the steering angle sensor. When the steering wheel is turned the position of the apertures changes relative to the light-emitting diodes (light/dark). A quite specific signal pattern for calculating the respective steering wheel position results due to the different length apertures and aperture spacings. Angle values are calculated with the aid of the signal patterns and converted into serial information for the control modules connected. The signals are recorded by light-emitting diodes and photoelectric barriers in 2 steps. The signal recording system is designed for a steering angle of ± 720° (4 steering wheel revolutions). Voltage is supplied via terminal 30 so that the steering angle is also recorded after ignition OFF". The steering angle sensor must be re-initialized after the voltage is interrupted (terminal 30). This is achieved by turning the steering wheel from stop to stop.