BMW 7 Series: Operating Principle Of Optical Steering Angle Detection

Steering angle detection

The code disc enables a 4-digit digital code to be generated for each light field. The 12- digit digital code is formed by lining up the 4-digit digital codes. The steering-angle speed can be ascertained from the changes to the individual digital codes.

Fig. 135: Operating Principle Of Optical Steering Angle Detection

COMPONENTS DESCRIPTION CHART

1. Code disc
2. Digital code for light field 1
3. Digital code for light field 2
4. Digital code for light field 3
5. 12-digit digital code

Block diagram of steering angle detection

The following block diagram shows the steering angle detection in simplified form.

Fig. 136: Steering Angle Detection Block Diagram

COMPONENTS DESCRIPTION CHART

1. Sliding register
2. Schmitt trigger
3. Photo-transistor
4. Code disc
5. Light-conducting element
6. LED (infrared)
7. Sensor circuit board
8. Activation of LED

The LED (8) is supplied with pulse-width modulated voltage, thus also supplying the light-conducting element (5) with infrared light. The light-conducting element projects the light onto the code disc (4). The phototransistors (3) pick up the light signals.

The signals of the photo-transistors are processed in the downstream electronics (2) into the signals "1" or "0".

The signals of the 12 photo-transistors are put together to form the digital code.

The sliding register (1) picks up the digital code and forwards it to the electronics of the steering column switch cluster.

Steering Wheel

Depending on the vehicle equipment, the following components are located in the steering wheel:

• Button block for telephone/radio
• Button block for cruise control system/Active Cruise Control
• Airbag with associated priming caps
• Horn button
• Vibration actuator for lane departure warning
• Steering wheel electronics
• Steering wheel heating.

Steering Wheel Structure

Fig. 137: Identifying Steering Wheel Important Components F01/F02

COMPONENTS DESCRIPTION CHART

1. Steering wheel heating
2. Button block for cruise control
3. Airbag unit
4. Vibration actuator for lane departure warning
5. Steering wheel electronics system
6. Button block for telephone/radio

The button blocks as well as the steering wheel electronics are linked across the LIN bus to the electronics in the steering column switch cluster.

With the corresponding request, the steering wheel electronics control and monitor the function of the vibration actuator and steering wheel heating.

The priming caps of the airbags are connected directly and are activated by the Crash Safety Module, ACSM.

The fanfare-horn button is evaluated by the electronics of the steering column switch cluster.

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