If you’re qualified to drive, you must also know how to park.
It is difficult for some, but generally requires only a little practise and not a whole lot of skill. Nonetheless, parking is the most common cause of bumper dents/scratches and painful wheel-to-kerb scrapes.
These days, many cars come fitted with electronic systems to assist the driver during parking.
Usually an audible warning tells the driver that the vehicle is closing in on an obstacle. The most common types beep at varying frequency, increasing as the distance between car and object decreases.
More elaborate systems come with a camera and monitor or a graphical display of the vicinity with colours to differentiate between a clear zone and an obstacle.
WHAT ARE PARKING SENSORS?
Parking sensor systems primarily consist of ultrasonic or electromagnetic proximity sensors usually mounted in the bumper.
The ultrasonic variant makes use of ultra-high-frequency sound waves which are inaudible to the human ear.
HOW ULTRASONIC PARKING SENSORS WORK
Like a miniature speaker, the sensor’s diaphragm vibrates at the frequency of a digital electrical pulse from the parking controller. By default, the pulses start every time reverse gear is selected.
Within its operating zone (usually around 3 metres) when the sound waves hit any object, they are reflected back to the source.
This changes the sensor diaphragm’s oscillations received by the controller. A preset algorithm in the ECU determines the distance and produces an appropriate output to the beeper or display.
Accuracy and envelop of the sensing zone is dependent on the number of sensors located around the car and their location.
A wide horizontal range is desirable, as this minimises the chances of the car and driver being “blindsided”.
But the vertical range must be limited to ensure that the road surface is excluded from the “sensing”.
ELECTROMAGNETIC PARKING SENSORS
These parking sensors are based on radar technology and hence rely on radio waves.
A transmitter-receiver unit sends out radio waves. These will be reflected when an object stands in the path of the wave propagation.
The returning wave will have a different characteristic because its frequency changes as the obstruction gets closer.
A radio receiver relays this information to an ECU that accurately calculates distance and approach speed. Based on these, appropriate audio and visual warnings are issued to the driver.
The electromagnetic system can be “hidden”. Ultrasonic sensors, on the other hand, must be mounted externally and distributed across bumpers.