Parking Assist Distance Sensor: Description and Operation

Distance Sensors












The four distance sensors are located in the rear bumper. They are mounted in identical plastic brackets that can be interchanged.

The sensors are named as follows:
- Left-hand outer distance sensor (RL)
- Left-hand centre distance sensor (RLC)
- Right-hand centre distance sensor (RRC)
- Right-hand outer distance sensor (RR)

Each distance sensor contains a diaphragm that works both as a speaker unit and microphone unit.

The distance sensors emit a wide-angle ultrasound signal (120° laterally and 60° vertically) and detect the reflected sound signals. The signals are converted to a digital signal that is sent to the control module for calculation of the closest object.

The distance sensors are active when the control module is in mode 2 or 3, i.e. Active and Detected

The distance sensors work according to a loop (controlled by the control module), which is repeated 3 times per second. The loop is as follows:
- Step 1: Sensor 1 - RL - emits an ultrasound signal and listens with sensors 1 and 2.
- Step 2: Sensor 2 - RLC - emits an ultrasound signal and listens with sensors 1 and 2.
- Step 3: Sensor 2 - RLC - emits an ultrasound signal and listens with sensors 2 and 3.
- Step 4: Sensor 3 - RRC - emits an ultrasound signal and listens with sensors 2 and 3.
- Step 5: Sensor 3 - RRC - emits an ultrasound signal and listens with sensors 3 and 4.
- Step 6: Sensor 4 - RR - emits an ultrasound signal and listens with sensors 3 and 4.

After a completed loop, the control module checks the sensors and calculates using Pythagoras' theorem (a2+b2=c2) which object is closest to the rear or side of the car, i.e, the object that the driver will be informed of.

Diagnostics
The control module monitors its own functionality and inputs and outputs. The distance sensors are checked 10 times/second in modes 2 and 3.

In the event of a fault in a distance sensor or its communication with the control module, the diagnostic trouble codes are generated:







- RR: Right-hand outer sensor
- RRC: Right-hand centre sensor
- RLC: Left-hand centre sensor
- RL: Left-hand outer sensor

For further information about fault diagnosis, Refer Fault Diagnosis, General/Fault diagnosis strategy for electronic systems. Testing and Inspection