Steering Angle Sensor: Description and Operation

GF42.45-P-5107RT Steering angle sensor, component description

Component Identification:

Location
The steering angle sensor is located in the steering column module. It is fastened with the fanfare horns and airbag clock spring contact onto the steering column module.

Task
The steering angle sensor which operates on an optical basis records the steering angle as given by the driver and forwards it to the connected systems.

Component Identification:

Design
The steering angle sensor consists of 2 microprocessors forming a single unit together with one signal ring. The signal ring accommodates the 9 light-emitting diodes at equal intervals. These are located in a photoelectric barrier duct which is traversed by 8 blades of various lengths. The photoelectric barriers are located in the upper section of the fanfare horns and airbag clock spring contact and only after assembly (clipped together) of both parts is the integral functional unit of the steering angle sensor given.

Function
When the steering wheel is in the center position, the 8 blades adopt a defined position relative to the 9 LEDs. This center position is detected by the processor in the steering angle sensor.

When the steering wheel is turned, the position of the blades changes with respect to the light-emitting diodes (light/dark). Because of the different lengths of the blades and the different intervals between them, a defined signal pattern is produced for computing the current steering wheel position.

The signal patterns are used to calculate angle values which are converted into serial data for the connected control units.

The signals are recorded by light emitting diodes and photoelectric barriers in 2.5 degrees increments. Signal acquisition is designed for a 720 degrees steering angle (4 steering-wheel turns lock to lock).

To ensure that the steering angle is also recorded after "Ignition OFF", the voltage supply is set up via circuit 30. In the event of a power breakdown (circuit 30) the steering angle sensor has to be initialized again. This is done by turning the steering wheel from lock to lock.