不同速度运动汽车的磁异信号研究与探测

运动汽车随着速度的增加伴随着非稳态材料的产生，如汽油高温燃烧、高速摩擦引起自由电荷累积等。针对这些磁异信号难以采用适用于铁磁性材料的磁偶极子模型描述的问题，提出了结合磁偶极子模型和运动电荷等效模型的方法，理论计算不同速度运动汽车的磁异信号并分析其时域、频域特征，获得磁异信号与速度的依赖关系。采用隧道磁阻传感器（TMR）结合滤波、放大、模数转换技术构建弱磁信号探测实验装置，探测不同速度运动汽车的时域磁异信号，并采用傅里叶变换获得其频域信息，与理论模型相吻合。随着速度的增加，频域信号向高频方向偏移，对于从低频地磁背景场中提取目标弱磁信号极其重要。 

Research and detection of magnetic anomaly signals of moving vehicles at different speeds

As speed increases, there is the creation of non-steady-state materials in vehicles, such as high-temperature combustion of gasoline and free charge accumulation caused by high-speed friction. These signals can not be explained by magnetic dipole model suitable to ferromagnetic materials. To solve this problem, a method combining the equivalent model of magnetic dipole and motion charge is proposed in this paper. The magnetic anomaly signals of vehicles at different speeds were calculated theoretically, their characteristics in time domain and frequency domain were analyzed, and the dependence relationship between magnetic anomaly signals and speeds was obtained. Further, a weak magnetic detection experiment device was constructed for detecting the magnetic anomaly signals of vehicles at different speeds in time domain, using the Tunnel Magnetoresistance sensor (TMR) combined with filtering, amplification and analog-digital conversion technology. The frequency-domain information was obtained using Fourier transform and the results agree with the theoretical model. In addition, the frequency-domain signal spectrum shifts to the high frequency as speed increases, which is extremely significant to extract weak magnetic target signals from low-frequency geomagnetic background field.