Collision Avoidance and Parking Assist Systems: Description and Operation
Park Distance Control (PDC):Functional Description:
Operating Principle:
The park distance control system serves as a collision prevention feature and assists the driver when parking and maneuvering.
The system monitors the distance between the vehicle and an obstacle on the basis of the ultrasonic echo sound method.
The system essentially consists of the following components:
- PDC control unit
- 4 ultrasonic transducers in the front bumper
- 4 ultrasonic transducers in the rear bumper
- PDC switch (push button with indicator lamp)
- Rear tone generator
- Front tone generator (BC gong)
The front ultrasonic transducers have a measuring range from approx. 20 cm to approx. 60 cm, whereas the rear measuring range extends from approx. 20 cm to
approx. 150 cm (inside) or 60 cm (outside).
If there is an obstacle within the measuring range in front of or behind the vehicle, this is signaled audibly to the driver by the relevant tone generator.
The signal comprises a sequence of identical tones.
The less the distance to the obstacle, the faster the tone sequence.
A distance of below 20 cm is indicated by a continuous tone.
To distinguish between them, the tone pitch at the front (1500 Hz = high tone) and at the rear (1000 Hz = low tone) differ..
Forward and reverse parking:
The front tone generator is switched off when an obstacle is approached while driving forward such that a distance warning is triggered and reverse gear is
then selected. However, the tone generator is reactivated if the vehicle continues to roll forward.
The same procedure takes place while reversing (rear tone generator) and a forward gear is selected.
Parking on Incline or laterally:
When parking on an incline or laterally with respect to an obstacle, only the transducers in the comers of the bumpers are used for measuring the distance. In
the case of these transducers, the distance warning is interrupted after 3 seconds if an obstacle is no longer approached, e.g. driving along a wall. The
distance warning is reactivated if the vehicle continues to approach the obstacle.
The distance warning is not switched off in the close range (approx. 20 cm) indicated by a continuous tone.
Activation and deactivation logic:
The push button to switch the system on and off and an indicator lamp are integrated in the PDC switch.
The system is switched on when the indicator lamp lights.
There are two ways of activating the system:
- Depressing the push button
- Selecting reverse gear
There are three ways of deactivating the system:
- Pressing the push button
- Automatically after covering a distance of approx. 55 m at a speed below 35 km/h
- Automatically after exceeding a speed threshold (approx. 35 km/h)
The indicator lamp goes out when the system is deactivated
Defect Indication:
The PDC control unit features a Defect code memory.
The system provides an indication to the driver when it has stored a Defect code.
When the system is switched on by means of the PDC switch, a short continuous tone is provided and the indicator lamp flashes.
If the system is activated by selecting reverse gear, a Defect is indicated only by the indicator lamp flashing.