PDC sensor parking aid
A PDC sensor parking aid is an advanced driver assistance system that uses ultrasonic sensors to help drivers park safely and accurately. It detects obstacles around the vehicle and provides audible and visual warnings to guide the driver during parking maneuvers. This comprehensive guide covers the function, operation, components, warning patterns, and maintenance of PDC parking aid systems.
The PDC sensor parking aid, also known as Park Distance Control (PDC), is a system that supports the driver while parking by indicating acoustically the distance to an obstruction behind or in front of the vehicle. This system assists the driver when maneuvering the vehicle into a parking space, or anywhere there are obstacles that need to be avoided, warning the driver accordingly. The parking aid is not infallible and is for guidance only; it cannot take the place of the driver's personal assessment of obstacles. The sensors may not be able to detect certain types of obstructions, such as narrow posts, small objects close to the ground, or objects with dark, non-reflective surfaces. The purpose of the system is to assist the driver when parking or maneuvering in restricted space, not as a crash avoidance system or a replacement for visual interpretation.
PDC Sensor
The PDC parking aid system typically consists of four ultrasonic sensors in each bumper, a control unit or ECU, a sounder for audible warnings, and a parking switch. The system operates using ultrasonic signals which are transmitted by the sensors. The reflected echo from this output is received by the sensors and used by the PDC ECU to calculate the distance from an object. The PDC uses the echo sounding principle to calculate the distances between each of the sensors in the front and rear bumpers and any obstacle that might be present. The PDC sensor outputs a pulsed signal to the PDC ECU, which the ECU translates into a distance reading. The ultrasonic sensors have their own electronics and operate in combined transmit and receive mode, first transmitting a package of ultrasonic impulses in succession, then picking up the echo impulse that is reflected by an object.
The activation of the PDC parking aid system is typically automatic. PDC is automatically activated whenever Reverse gear is engaged. Both front and rear sets of sensors are activated and the indicator in the switch illuminates. A brief confirmation tone sounds when the parking aid is ready. To switch it off, the driver can drive faster than 10 mph (15 km/h), or press the PDC switch manually. When driving forwards into a limited space, front PDC can be activated manually by pressing the switch. If PDC has been manually switched off, it will not activate automatically until the switch has been pressed again, or the starter switch has been turned off and on again. The PDC ECU monitors the condition of the PDC switch by providing a feed, and when the switch is pressed, an earth path is created, initiating the PDC system.
The warning pattern of the PDC parking aid is designed to be intuitive for the driver. During distance measurement, the pauses between chime impulses get shorter as the gap between the vehicle and the obstacle decreases. The distance from an obstruction is identified by an intermittent tone sounding, with a higher pitch for the front sensors and a lower pitch for the rear sensors. As the vehicle moves closer to an obstruction, the frequency of the tone increases proportionally. At proximity of less than approximately 30 cm (1 foot), a continuous tone is heard. The maximum detection range is typically up to 2000 mm (78.7 inches). When an object is detected, the time delay between the audible warning tones decreases as the distance between the detected object and the vehicle decreases until the audible warning tone becomes continuous. If an object is detected by one of the corner sensors only, the audible warnings stop after about 5 seconds if there is no change in the distance.
The PDC parking aid system also features diagnostic capabilities. The parking aid system is capable of On Board Diagnostic (OBD). If a malfunction exists in the system, a tone will sound for 5 seconds. If a long, high pitched tone sounds and the switch indicator light flashes when PDC is activated, then a fault in the system has been detected. The PDC ECU has an on-board diagnostic routine that monitors the system and alerts the driver to a system fault by emitting a tone from the sounder. If a PDC system fault has occurred, the sounder will emit a continuous tone for 3 seconds and the PDC switch LED will flash continuously when reverse gear is selected. When a new parking aid sensor is installed, the sensor head must first be painted to match the color of the bumper cover, following specific requirements to ensure the parking aid system will work correctly. The PDC system has a blind spot where objects cannot be detected, and the system is subject to the physical limits that apply to all forms of ultrasonic measurement. Regular maintenance, including keeping sensors free from dirt, ice, and snow, is essential for optimal performance.
