Design On The Portable Impact Electromagnetic Source

The impact type electromagnetic source overcomes the shortcomings of the high frequency components of the traditional frequency sweeping electromagnetic source,and has the advantages of not destroying the original signal,the signal energy is larger,the signal to noise ratio is better,the excitation signal is close to the explosive source,and the inversion interpretation processing is simple.It is the hot direction of the development of the source.The research on impact source in the thesis has important theoretical significance and practical value for promoting shallow fine survey.According to the principle of electromagnetic emission,this thesis designs a new type of impact electromagnetic source,which can meet the following three design requirements more comprehensively than the existing artificial source:(1)sufficient impact force and energy;(2)portable performance to meet various shallow geological exploration occasions;(3)safety and no environmental pollution.Firstly,according to the principle of electromagnetic emission,the structure of impact electromagnetic source system is designed,including electromechanical system,source structure and charge-discharge circuit.Secondly,the finite element analysis is carried out through the electromechanical simulation model built by MAXWELL,and the relevant performance parameters such as force distribution,acceleration and the like of the focal electromagnetic hammer in the discharge process are accurately obtained.According to the analysis results,the electromagnetic hammer is designed as upper pure iron and lower stainless steel,and the contradiction between electromagnetic energy conversion efficiency and ground coupling degree is solved by using the difference of its size and ferromagnetism.The drive coil is designed in a multi-winding parallel connection mode,and the current rise time is reduced by reducing inductance to improve the stress effect of the electromagnetic hammer.Then,in order to meet the specific requirements of the instantaneous discharge of the impact electromagnetic source,the charging,discharging and control circuits in its transmitting circuit are analyzed and designed respectively.The current limiting resistor and series high-voltage silicon stack are adopted to solve the problems of large current and reverse charging in the charging circuit respectively and protect the safety of the circuit.Reasonable selection of discharge circuit element parameters makes it work in an overdamped state,effectively improves the peak value and steepness of the impact current waveform,matches the discharge current waveform with the electromagnetic hammer motion waveform,and further improves the working efficiency of the impact electromagnetic seismic source.Finally,integrating the above theoretical analysis and research,the instrument development of the impact electromagnetic source system is realized.Through experiment results,the device performance is analyzed,and the seismic wave signal is collected on site for spectrum analysis.The ultimate kinetic energy of the source system reaches 709.41 J,the instantaneous impact force reaches 49910 N,and the generated seismic wave signal bandwidth can reach 200 Hz,which can meet the engineering needs.