Study On Design Magnetic Detection Technology And Application Based On Giant Magneto-impedance Effect

Magnetic detection technique has been widely used for its invulnerability to electronic interference, independence of the effects of rain, smoke, fog and other adverse environment.The new magnetic detection system based on giant magneto-impedance effect(Giant Magneto-Impedance, GMI) which has high sensitivity and highly linear performance can significantly improve the ability to detect ferromagnetic targets on the battle field. Firstly,in this paper, GMI effect in amorphous wires physical properties are analyzed and a detection theory with magnetic sensing system is explored, then one-dimensional magnetic detection system and three-dimensional magnetic detection system with high sensitivity are designed and implemented, respectively. Meanwhile, under the background of the research on the detection of ferromagnetic target in the battle field such as Tanks, this study develops the application technology research of the magnetic detection system based on GMI effect.In this paper, firstly, the mechanisms for GMI effect and its related theories have been thoroughly discussed. Based on electromagnetic theory, the different characteristics of the applied frequency band for GMI effect have been analyzed to determine the theoretical model of GMI effect. The analysis of theoretical model shows the main influence factors of the GMI effect in amorphous wires, and the influence laws between those factors are also discussed in this paper. Comparing the experiment results, we have got the optimal combination of various factors influencing GMI effect, which provides a theoretical and experimental basis for the design of GMI effect magnetic sensor.Furthermore, a GMI effect magnetic sensor with high sensitivity has been designed based on the above theoretical and experimental foundations. In the circuit design, CMOS inverters were used to acquire a highly stable pulse excitation signal. In order to improve the sensitivity of the sensor, the method of amorphous wire coiled collection was employed to replace the method of traditional amorphous wire terminal voltage collection. Meanwhile,a peak sampling and keeping circuit adopted analog switch instead of the diode devices with the purpose of improving the stability of the circuit. Finally, a fourth-order Butterworth filter circuit and a feedback circuit were designed to preprocess the collected signals. In addition, the sensor was verified by the experiments to meet the ferromagnetic targets detection accuracy, linearity and so on.Based on the design of one-dimensional sensor, taking FPGA as the core unit, a threedimensional GMI magnetic sensor was designed for detecting magnetic field of the non-cooperative target. Using the CORDIC algorithm, three-axis magnetic field was superposed to detect the value of the total magnetic field. The detection experiments about three components and total magnetic field of the three-dimensional magnetic sensor output for moving ferromagnetic target have been developed in the relatively stable magnetic field in the laboratory and outdoor environment, respectively. Experimental results show that the detection system can detect ferromagnetic targets sensitively, and get the change of the magnetic field features of the car in 6 to 8 meters away.In the process of detecting magnetic field, the detection results are susceptible to carrier magnetic field. Then we developed the method of estimating the magnetic field coefficient of the fixed magnetic field and the induced magnetic field based on the qusai-Newton method, which has high rate of convergence, excellent stability and maximum effectiveness of the magnetic interference compensation. Meanwhile, a method to calculate the relative velocity was proposed using a dual-sensor output. It can solve the impact of carrier velocity during target detection process. The experimental results showed the feasibility of the proposed scheme.For a typical battlefield ferromagnetic targets-tank, the spatial distribution of the magnetic field was carried out. In this paper, one mathematical model was established based on the spatial distribution of its magnetic field, and the numerical analysis was used to derive space distribution of the magnetic field for the tank. Then we discussed the characteristic of tanks magnetic field. Besides, the target detection and recognition guidelines based on these characteristic was established, which provides the necessary theoretical basis and effective support for the detection and identification of magnetic target.