Application Of Ultrasonic Ranging In Parking Assist System

Growth and booming of automobile industriy bring great rise of vehicle stock. However, it also causes traffic jam and frequent occurring traffic accidents. According to statistics, parking easily leads to traffic accidents. So how to simplify parking maneouvres is the key point to ensure vehicle's safety.During all kinds of parking assist systems, ranging is a frequently used approach. Among the vehicle-mounted ranging approaches, ultrasonic ranging is a grown and most suitable one. Ultrasonic wave is qualified with some good physical nature and it makes ultrasonic wave broadly used in a number of areas. Ultrasonic ranging including phase and TOF method and TOF is chosen for its low cost, easy implement and greater range. Ultrasonic wave's transmitting is related to environment's temperature and it should be acquired by ultrasonic ranging system. Ultrasonic wave will be damping when flying in the air and 40 kHz is best frequency of ranging usage. For the sake of influence of side lobe and aftershock, there would be a dead zone of TOF ultrasonic ranging method.Ultrasonic ranging system is consisted by MCU, ultrasonic transmitting circuit, ultrasonic receiving circuit, temperature measuring module and display module. Ultraosnic transmitting circuit is based on the 555 timer IC. Ultrasonic receiving circuit is based on CX20106A. Temperature measuring module is formed by DS18B20. Display module is based on quaternity LED SM410564. And software is fabricated according to hardware. It's proved that the ultrasonic ranging system is able to complete ultrasonic ranging.Because of the existence of lobe, ultrasonic ranging system can not localize obstacle in 2D and 3D. Theoretically, three receiving transducers' receiving system may localize obstacle. Three receiving transducers'parking assist system consists of MCU, power module, display module, temperature measuring module, storage module, ultrasonic transmitting circuit, ultrasonic receiving circuit and vehicle speed measuring circuit.Parking assist system is provided with certain precision, nonlinear error and repeatability error. Pakring assist system completed double receiving transducers'dot obstacle finding and single receiving transducer parking environment detection tests, which proved that this system is able to use difined hardware to finish some parking assist functions.