Research On Application Of AMR Aensor For Vehicle Detection In The Parking Lot

As the urban population rapidly rising, motor vehicles get rapid growth. The car parking problem has become an urgent problem to be solved. Intelligent parking lot has been widely used especially for intelligent parking system. In the intelligent parking system, the vehicle detection sensor is the key part of information collection. Now there are various vehicle detection methods, and magnetic testing is relatively one of the effective detection methods.In this paper, dual polarity permanent magnets model is studied to deduce the formula of magnetic field. The formula could be applied to study magnetic field geperturbation produced by the vehicle. This magnetic field is simulated by using an iron ball model. The experiment result indicates that there is a peak value of the output voltage when the iron ball moves along the Y direction. In this way, the detection method and the judgment method are obtained. A parking judgment detection system is designed based on anisotropic magnetic resistance (AMR). The system can be divided into six units which are information detection unit, data acquisition unit, information transmission unit, data processing unit, data execution unit, data storage unit. AD623 and LM324 are used as the amplifier circuit of the system, which has the virtues of low power consumption, high magnification, output impedance low. TLC1459 is used as Analog to Digital Converter (ADC) to realize low error and high rate of frequency-field. Bootstrap circuit is used to make the power of system upraise to realize the reset function. SPEC061A is used as the core part of the system to achieve date processing, controlling and performing. It has advantages of high processing speed, low power waste, high stability. Using this testing system, the magnetic field distribution of various vehicles on the different location can be accurately measured. The results show that the carport can be precisely judged through the fixed threshold method. The system has the performance of simple circuit, convenience and high reliability. Using magnetic resistance sensor to test vehicles is an innovative and practical subject research. With the help of the wireless sensor network, the function of system can be expanded. In the further, it will have further application prospects in the system of vehicle information collection and traffic transportation system.