Detecting Steering Angle and Steering-Angle Speed: Notes

To pick up the steering angle, a code disc is illuminated from above by an LED and a light-conducting element. Due to the pattern in the code disc, the light from above only reaches down to certain areas. There, the light encounters photo-transistors.

The pattern of the code disc corresponds to the digital code of the steering angle.

The photo-transistors convert the light signals into electrical signals. As the signals are not yet sufficiently unambiguous, they are processed by downstream electronics.

Thereafter, the signals are digitized and have the signal states 1 or 0.

The steering column switch cluster receives the current value of the steering angle, the digital code, and forwards this across the FlexRay.

A section of the code disc and the optical sensor are shown below.

Section on the code disc	Optical sensor
The code disc (1) rotates depending on the steering-wheel position. The pattern of the digital code (2) on the code disc changes in 0.5° steps. The light of the light-conducting element (3) penetrates the pattern of the digital code of the code disc.	The light beams encounter the photo-transistors in accordance with the pattern of the digital code. The photo-transistors convert the light beams into electrical signals. The downstream electronics ensure that the electrical signals have the signal states 1 or 0. This means that the steering angle is available to the steering column switch cluster as a digital code.
If the code disc (1) continues to rotate, the pattern (2) on the code disc changes. The light of the light-conducting element (3) penetrates the code disc in other areas.	A new digital code is generated in accordance with the changed pattern of the digital code. This means that the new steering angle is available to the steering column switch cluster as a digital code.