Research On Bandwidth Expansion Of Seismometer Based On Optimization Of Mechanical Topology And Feedback Circuit

As a measuring instrument of ground motion,seismometer is widely used in geological disaster prediction,earthquake precursor information capture,engineering investigation and nuclear explosion monitoring.The seismometer plays a vital role in the process of vibration signal monitoring,and its performance is of great significance to seismic monitoring and signal acquisition.In the process of seismic monitoring,the seismic waves received by seismometer are mainly low-frequency signals.When the frequency of seismometer is too high and the frequency band range is too narrow,it is difficult to pick up the low-frequency signals,which can not meet the needs of seismic monitoring.Therefore,in view of the problem that the effective frequency band of the existing seismometers is not wide enough,this paper takes the moving coil seismometer as the research object,and optimizes the mechanical structure and feedback circuit of the seismometer to reduce the natural frequency,broaden the frequency band range and ensure the reliability of seismic monitoring data.The optimization process is carried out from two aspects: topology optimization of seismometer mechanical pendulum structure and parameter optimization of feedback circuit.The main research contents include:(1)The working principle of the moving-coil seismometer was studied,and its transfer function was deduced.Through the corresponding theoretical analysis,the influencing factors of the bandwidth and natural frequency of the moving-coil seismometer were obtained in this study.Based on the results of theoretical analysis,this research further optimized the moving-coil seismometer system from two perspectives including the mechanical pendulum structure and the feedback circuit.(2)Variable density method was utilized to establish the mathematical model of topology optimization of the mechanical pendulum,with the optimization objective of minimizing the natural frequency of the mechanical pendulum in case of that its volume and stiffness fulfil the requirements as well as the optimization algorithm as moving asymptotes algorithm.On this basis,the topology optimization of the mechanical pendulum structure of the seismometer was completed by utilizing finite element software ANSYS Workbench.Additionally,through modal analysis,harmonic response analysis,static and transient analysis,etc.,the mechanical pendulum performance before and after optimization was simulated and compared.(3)In order to further reduce the natural frequency of the moving-coil seismometer,the feedback circuit network was optimized and a feedback circuit based on double feedback loops was proposed.The genetic algorithm was used to optimize the circuit parameters of the feedback loops,and the MATLAB software was used to optimize the circuit parameters of the double feedback loop with the minimum natural frequency of the dynamic ring seismometer system as the optimization goal.(4)On the premise of processing and assembling the prototype of the seismometer,the natural frequency of the mechanical pendulum before and after optimization were tested as well as the effective frequency band range of the seismometer,and the performance parameters of the seismometer were obtained.The related research findings indicated that: a)the natural frequency of the optimized mechanical pendulum was reduced from 4.8Hz to 3Hz,reducing by 37.5%,and;b)the frequency band range of the seismometer was 0.5-70 Hz before optimization,while the frequency band range of seismometer after the parameters optimization of mechanical topology and feedback circuit was 0.21-80 Hz,with the frequency band of low-frequency bands expanded by 58% compared with that before optimization,demonstrating that the low-frequency characteristics were improved effectively.