Low-frequency Compensation Technology Of Magnetoelectric Geophone

In the field of geophysical prospecting,seismic exploration is the most important means of exploring resources.The basic principle is to artificially excite elastic waves and record the reflected waves and refracted waves at the rock layer interface,and understand the geological structure by analyzing the waveforms.In actual seismic exploration applications,geophones are often used to pick up vibration signals.Magnetoelectric geophones are widely used because of their high signal-to-noise ratio,convenient interface,and stable structure.With the deepening of geological exploration from shallow to deep,it is necessary to improve the performance of geophones to pick up low-frequency signals.The response of magnetoelectric geophones to low-frequency signals is related to the parameters of its own mechanical structure.When the natural frequency is further reduced,its mass and volume need to be increased,which brings great inconvenience in engineering applications.In view of the above problems,this article takes the magnetoelectric geophone as the research object.Without changing the mechanical structure of the geophone,a reasonable compensation scheme is selected to study the low-frequency characteristics of the magnetoelectric geophone.The main research contents of this artile are as follows:(1)According to the structure and working principle of the magnetoelectric geophone,the dynamic model is established,and the open-loop transfer function and the closed-loop transfer function are derived from the dynamic model,so as to obtain the frequency characteristic curve of the geophone.In order to facilitate the subsequent circuit simulation,the electrical equivalent model of the magnetoelectric detector is derived from the principle of mechanical-electrical equivalence,and the simulation results show that the model effectively restores the input and output characteristics of the magnetoelectric detector.(2)The characteristics of passive compensation method,feedback compensation method,pole-zero compensation method and system identification compensation method are analyzed,and pole-zero compensation method is finally selected as the theoretical basis of low-frequency compensation for this subject.(3)Based on the transfer function derived from the pole-zero compensation method,the transfer function is transformed and a reasonable circuit structure is selected to design the active compensation network.The compensation circuit is simulated and parameter adjusted on Multisim.The simulation results show that the active compensation network is feasible and effectively compensates the low-frequency characteristics of the detector.According to the design and simulation results,a hardware platform and data acquisition device are built.(4)This article designed a digital filter which based on the transfer function of the analog compensation circuit based on the zero-pole compensation method.The digital filter program is processed on the LPC11U68 microcontroller based on the ARM core,and the appropriate pre-gain and single-ended-to-differential circuit are designed to build the acquisition circuit.Experiments show that the active compensation circuit designed compensates the low frequency characteristics of the detector with a natural frequency of 4.5Hz to0.11 Hz and the digital filter designed meets the requirements of real-time,and the low-frequency detection performance of the detector is effectively compensated.