Optical Steering-angle Sensor: Notes

The steering column switch cluster contains the optical steering-angle sensor as well as the associated electronics. A second processor on the underside of the board backs up the information regarding the steering angle and steering-angle speed. This is why the steering angle and steering-angle speed are evaluated and calculated in the second processor in addition to the main processor of the steering column switch cluster.

The steering-angle sensor is designed as a non-contact optical angle measurement system. The system consists of a code disc and an optical sensor. The code disc is connected directly to the steering wheel via a driver. If the steering wheel is moved, the code disc rotates within the optical sensor.

The code disc has a pattern of holes. The pattern of holes is arranged in such a way that four circular tracks are formed. The four tracks represent the digital range of the sensor. The digital code changes when the steering is turned every 0.5°.

Fig 1: Identifying Code Disc And Optical Sensor

Courtesy of BMW OF NORTH AMERICA, INC.