异向性磁阻传感器检测车流量的新方法

A novel approach for vehicle flow detection by using anisotropic magnetoresistive sensor

针对因单轴或双轴的模拟式异向性磁阻传感器检测车流量时无法获取空间磁场、地磁垂直分量(Z轴)不能全面体现车辆信息,以及环境中的强磁场导致磁阻传感器输出信号漂移等问题,根据行驶车辆对地磁场的扰动效应原理,设计开发了基于ZigBee无线传感器网络的车流量检测系统,提出一种车流量检测方法.该方法采用新型三轴数字式磁阻传感器HMC5843替代传统的单轴或双轴模拟式磁阻传感器,以三轴磁场合成的磁场强度替代地磁垂直分量执行状态机算法检测车流量,当车辆驶离传感器时重新获取环境磁场来解决信号漂移问题.实际测试表明:该方法在测量精度、可靠性、冗余度等方面均优于地磁垂直分量(Z轴)法.

In terms of current issues that the space geomagnetic field cannot be obtained, the geomagnetic vertical component （Z axis） is unable to reflect the vehicle＇s information completely and the sensor＇s output signal drifts along with the surrounding strong magnetic field by using the single or dual-axis analog anisotropic magnetoresistive（AMR） sensor in the traffic flow detection, a traffic flow detection system based on ZigBee wireless sensor network was developed and a novel approach to detect the traffic flow was proposed to solve these issues. The traditional single or dual-axis AMR sensor was replaced by the new digital three-axis AMR sensor HMC5843, and the magnetic field strength was used to execute state machine algorithm instead of the traditional Z axis component. After the vehicle left the sensor, the surrounding magnetic field was re-accessed to solve the drifting problem of sensor. The experimental result shows that the novel method has much better measurement accuracy, reliability and redundancy than the Z-axis method.