Test And Research Of Underwater Metal Electromagnetic Reflection

With the development of marine resources development and utilization of gradually become national key fields, the detection technology for underwater metal objects such as underwater vehicle, gold, silver and precious metal is also developed. Ordinary detecting method such as image sonar is not efficient in detecting buried metal objects, but electromagnetic detecting method do. In this paper electromagnetic reflection of underwater metal is researched in order to provide theory and test basis for underwater metal electromagnetic detection.This thesis is focus on theory analysis and test for underwater metal electromagnetic reflection, introduced development and research status of underwater electromagnetic detecting in domestic and abroad, provide the theory of underwater electromagnetic reflection from a metal object, analyzed Spatial distribution of magnetic dipole, simulated underwater attenuation of electromagnetic field, propose the arrangement of electromagnetic sensors according to the feature of electromagnetic reflection, and also designed radiation coil and radiation circuit for underwater electromagnetic detection, chose the electromagnetic sensor fit for frequency, build the data acquisition, and write a program for data acquisition and analysis. Based on the feature of electromagnetic reflection signal, this paper proposed wavelet de-noising algorithm, amplitude envelope detecting method, transient feature extraction method, and radiation coil equivalent impedance calculation method for underwater electromagnetic reflection signal, and also provide basis for metal type judgment by electromagnetic reflection amplitude envelope and radiation coil equivalent impedance. Electromagnetic reflection test using aluminum and iron is accomplished in fresh water, this paper analyzed signal of electromagnetic reflection and equivalent impedance, prove the efficiency of detect, signal process and feature extraction method for electromagnetic reflection, and achieved metal type judgment under certain conditions.