PDC Sensor System - Technical Architecture of Multi-Sensor Parking Distance Control Networks
This technical article provides a comprehensive analysis of the
PDC sensor system architecture, covering the multi-sensor network topology, master-slave configuration, signal processing chain, and integration with vehicle electronic systems for reliable parking distance control.
The PDC sensor system is a complete parking distance control solution comprising multiple ultrasonic sensors, a control module, and user interface components. The system consists of four ultrasonic sensors in each bumper, a control module (ECU), a sounder or buzzer for audible warnings, and a switch for manual activation. In more advanced configurations, five ultrasonic sensors may be installed in the front bumper, with four sensors fitted to the rear bumper. The PDC runs a distance measurement in relation to objects in the pickup range by means of ultrasonic sensors. The system monitors the distance between the vehicle and an obstacle on the basis of the ultrasonic echo sound method. The system serves as a collision prevention feature and assists the driver when parking and maneuvering.
PDC Sensor
The system architecture employs a master-slave configuration for efficient sensor control. In a master-slave compatible PDC system, the master sensor comprises a CPU module, a first ultrasonic transducer, a master drive module, a master amplifier module, slave drive modules, and power supply modules. The slave sensors are digital probes without CPU, comprising an ultrasonic IC, a boost drive module, and a second ultrasonic transducer. The CPU module drives the first ultrasonic transducer via the master drive module, and the first ultrasonic transducer amplifies and transmits echoed signals to an A/D conversion module of the CPU module via the master amplifier module. The CPU module drives the ultrasonic IC of the corresponding slave sensor via a slave drive module, which drives the second ultrasonic transducer via the boost drive module. The ultrasonic IC is employed for each slave sensor, enabling a farther detection distance and stronger anti-interference capability of the whole system.
The signal processing chain within the PDC system involves coordinated operation of all sensors. In combined transmit and receive mode, the ultrasonic sensors first transmit a package of ultrasonic impulses in succession, then pick up the echo impulse reflected by an object. The echo impulse is amplified in the ultrasonic sensor and forwarded as a digital signal to the control unit. In receive mode, an ultrasonic sensor picks up the echo impulses sent by neighboring ultrasonic sensors. The control unit can evaluate signals from up to three ultrasonic sensors simultaneously using trilateration. From the individual digital signals, the control unit calculates the shortest distance between an ultrasonic sensor and the object. When an object is detected, a visual warning is displayed and audible warnings are generated. This coordinated processing ensures accurate obstacle detection and localization.
The system's activation and deactivation logic is designed for user convenience and safety. There are two ways of activating the system: depressing the push button or selecting reverse gear. There are three ways of deactivating the system: pressing the push button, automatically after covering a distance of approximately 55 m at a speed below 35 km/h, or automatically after exceeding a speed threshold of approximately 35 km/h. 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 ECU also provides a feed to the switch tell-tale LED. The system also features intelligent behavior during specific parking scenarios, such as when parking on an incline or laterally with respect to an obstacle, where only the transducers in the corners of the bumpers are used for measuring the distance.
The PDC system integrates with other vehicle systems through the vehicle's bus network. The PDC control module is linked to the vehicle's bus system for vehicle speed, transmission range selection, and diagnosis. The module sends messages via the vehicle's bus to the audio system and central display. This enables visual warnings to be displayed on the central information display, showing an overhead view of the vehicle with the effective range of the ultrasonic sensors. The module also controls the tone signal generator, producing different frequencies for front and rear obstacle detection: 1500 Hz (high tone) for front sensors and 1000 Hz (low tone) for rear sensors. The junction box electronics (JBE) activate the ultrasonic sensors to send the ultrasonic impulses and receive the digital signals. This comprehensive integration ensures the PDC system operates seamlessly with other vehicle systems for effective parking assistance.
