Ultrasound-based parking aid - park distance control (PDC)

The parking assistant is a driver assistance system that supports drivers during manoeuvring and parking and warns them of obstacles in the immediate vicinity of the vehicle.

The traditional parking aid operates on the basis of ultrasound that is emitted using several sensors. If an obstacle is detected, the driver is informed of this either visually or acoustically. The more ultrasonic sensors that are installed and spread out across the width of the vehicle, the more accurate the measurement result will be. Depending on the vehicle or on the system, LED displays, graphic representations on the screen or purely acoustic signalling devices can be installed to provide the necessary information.

The following system descriptions and diagnostic information are illustrated using the example of a Golf V Plus. The manufacturer's designation for the purely acoustic parking aid is park distance control (PDC). Because four ultrasonic sensors are installed in the rear bumper, this is referred to as a 4-channel system.

The parking aid for the rear section of the vehicle consists of the following components:

Supply voltage 9 -16 volt
Ultrasonic frequency 50kHz - 60kHz
Detection angle: vertical / horizontal 60° +/- 10° degrees
Range 250cm
Temperature range -40 to 85°C

The ultrasonic sensors or rather their system functioning is monitored by the relevant higher-level control unit. Any occurring errors are stored in the control unit's error memory and can be exchanged/updated by using a suitable diagnostic unit. With some vehicle models, a warning message can also be displayed on the instrument cluster in the event of a system error.

However, before control unit diagnostics are undertaken, it is first advisable to carry out a visual inspection of the individual system components as part of initial troubleshooting activities.

As part of control unit diagnostics, it is possible to employ the help of various functions and vehicle information as and when needed.

During installation of the ultrasonic sensor, care must be taken to ensure that the decoupling element is correctly seated. If the installation is faulty, send and receive operations may be adversely affected

The ultrasonic sensors in the bumpers must be kept clean and free of ice in order to ensure adequate functioning of the PDC system.
And so as to prevent any damage occurring, cleaning the sensors with a high-pressure cleaner should be avoided.

In the majority of cases, the visible surfaces of the ultrasonic sensors have been painted in the vehicle's colour.
In such cases, the manufacturer stipulates vehicle-specific paintwork guidelines in order to avoid any impaired functioning. So Volkswagen, for example, specifies that the paint thickness on the front and side surface of the membrane must not exceed 125µm.
With regard to this matter, the current, vehicle-specific information provided by each individual vehicle manufacturer should be observed!