Research On The Temperature Effects Of Silicon Resonant Micro Accelerometer Based On Electrostatic Rigidity

The resonant micro accelerometer is a mechanical sensor that utilizes the micro-beam resonant frequency to sense external acceleration.It has the advantages of small size,light weight,low power consumption,high measurement accuracy,good stability,easy mass production,and accurate digital signal output.In the military,aerospace and automotive electronics and other fields have a wide range of application prospects.Compared to other resonant micro accelerometers,the electrostatic stiffness type resonant accelerometer can adjust the resonant frequency of the micro-beam by changing the bias voltage,thereby realizing the adjustment of the key performance indicators such as the accelerometer scale factor and sensitivity.Strong design flexibility and high process robustness.However,as a mechanical sensor,this kind of accelerometer also has the problem of thermal stability,that is,the ability of performance to keep constant with temperature changes.The temperature effect of the thermal stability of the silicon resonant micro accelerometer based on electrostatic rigidity has been studied in this thesis.And the main work and achievements were as follows.(1)Based on the analysis of the structural characteristics of the vibrating beam of the electrostatic stiffness type resonant micro accelerometer,combined with the Euler-Bernoulli beam theory and the Hamiltonian principle,the mechanical-electrical-thermal multi-field control equation of the micro-beam vibration is established.And using the Laplace transformation,the vibration mode function of the micro beam was deduced.Compared with the mode shape function deduced based on the traditional model,the mode function considers the effect of the axial force and the lumped mass.COMSOL Multiphysics simulation showed that the mode function derived from this paper was more accurate.Based on the lumped parameter method and the Galerkin method,two analytical macromodels for micro-beams were established,namely a lumped parameter model and a Galerkin method macromodel.(2)Based on E.Suhir's three layer structure theory,the analytical expression of the equivalent axial force of the micro-beam subjected to the residual thermal stress was deduced.Combined with the working principle of the micro accelerometer,the change rule of the key performance index of the micro accelerometer caused by the temperature change was obtained.The results of the research showed that when the existing micro-accelerometer was operated in the temperature range,the frequency fluctuation of the micro beam reached 14.09% and the fluctuation of the scale factor reached 28.55%.By analyzing the function relationship between temperature and the scale factor of the micro accelerometer,this paper proposed a new method to improve the thermal stability of the micro accelerometer scale factor by adjusting the stiffness ratio K.This method had the advantage that it didn't require additional temperature control facilities and structural improvements compared to other measures for improving thermal stability.(3)Based on the macro model of Galerkin's method,the influence of temperature on the vibration modes of the main vibration mode and the higher vibration mode of the beam were analyzed.The numerical simulation results showed that the temperature had the greatest influence on the response amplitude of the first-order principal mode shape,and with the increase of temperature,The amplitude of the micro beam increased.The multi-scale method was used to obtain the amplitude-frequency response function of the micro-beam coupling system.The nonlinear temperature effects of electrostatic stiffness nonlinearity and mechanical stiffness were analyzed.The numerical simulation results showed that the higher the temperature,the stronger the two nonlinearities and the temperature change.Mainly through the influence of electrostatic stiffness to affect the nonlinear characteristics of micro-beam vibration.