Finite Element Modeling And Design Of Mechanical Pendulum Of Force Balance Feedback Seismometer

Force balance feedback seismometer is an important part of earthquake observation system,and the effective frequency range is the key performance index.In order to obtain more useful earthquake signals,expanding the effective frequency range of seismometers has become a research hotspot.The frequency range of seismometer is determined by the inherent frequency of mechanical pendulum and feedback circuit.In this paper,the method of reducing the natural frequency of mechanical pendulum is used to expand the frequency range of seismometer.The finite element modeling and simulation is introduced to the study of the natural frequency of the mechanical pendulum of seismometer,and the finite element model of the mechanical pendulum of force balance feedback seismometer is established.The influence of mechanical pendulum sensitive element on the first and second natural frequency is simulated and analyzed,and the relationship between the geometrical size of the sensitive element and the natural frequency of the mechanical pendulum is determined.Topological design of mechanical pendulum structure is carried out by topological calculation,and the natural frequency and effective frequency range of the new topology structure are tested.The test results show that,compared with the traditional mechanical pendulum seismometer,the first natural frequency of the new topology mechanical pendulum seismometer is reduced from 6Hz to 5Hz,the secondnatural frequency is increased from 46 Hz to 88 Hz,and the frequency difference is increased from 40 Hz to 83 Hz.Driven by the speed of the 0.5cm/s,the output voltage response of the new topology mechanical pendulum seismograph is4.58 V at the frequency of 0.5Hz,the output voltage response of the traditional seismograph is 3.59 V at 0.5Hz and 4.64 V at 1Hz under the same excitation.Thus,the starting point of the effective band range is reduced by50%,the frequency band has been widened by 0.5Hz.