Research On Self-Excited Driving Technology Of Silicon Micro Resonant Pressure Sensor

The silicon micro resonant pressure sensor has the advantages of high precision,long-term stability,quasi digital output and so on.It has a broad application prospect in both military and civil fields.In this paper,the closed-loop self-excited driving technology of silicon micro resonant pressure sensor with self-developed electrostatic excitation and piezoresistance detection mode is studied,and the experimental prototype is developed.The completed work includes:(1)This paper introduces the basic structure and working principle of silicon micro resonant pressure sensor,analyzes the principle of electrostatic drive and piezoresistance detection,establishes the Wheatstone bridge model for the piezoresistance detection mechanism of the sensor,designs and analyzes the constant voltage source excitation circuit,establishes the linear resonator model and carries out dynamic analysis,and completes the design for measurement and control system framework of silicon micro resonant pressure sensor.(2)The DC AGC(Automatic Gain Control)self-excited drive system based on linear resonator model is designed,and the corresponding mathematical model is established.The average method is used to solve the model.The feasibility of the closed-loop self-excited system and the accuracy of the average method are verified by simulation in Simulink,and the influence of resonator quality factor change on the system is discussed.The 90°wide-band phase-shifting circuit and AGC circuit of the self-excited system are designed and analysed.(3)The vibration characteristics of the nonlinear resonator are analyzed;the DC AGC closed-loop self excitation model based on the nonlinear resonator is established and solved by the average method;the natural frequency and nonlinear coefficient of the actual pressure sensor are measured by the open-loop sweep and linear fitting,and then the simulation model of the system is improved and the results of the system analysis are verified by the simulation;the effects of stiffness nonlinearity on the frequency stability and dynamic characteristics are discussed;two methods of reducing frequency noise are explored and analyzed.(4)The whole system of the silicon micro resonant pressure sensor is tested in the range of 12k Pa?120k Pa.The results show that the sensitivity of the sensor are 28.0719Hz/k Pa,27.5774Hz/k Pa and 27.2606Hz/k Pa in the environment of low temperature(-40?),room temperature(19.7?)and high temperature(80?),the average temperature coefficient of the sensitivity is-0.00676Hz/k Pa/?,and the linearity of the sensor is 13.9682ppm,72.7040ppm and 13.2676ppm,respectively.The average temperature coefficient of the output frequency within the test range is within the range of-0.590Hz/??-1.241Hz/?.The accuracy of the sensor is better than 0.01%FS,and the hysteresis of the sensor at each temperature point is11.8231ppm,70.0093ppm and 17.8903ppm respectively.The frequency drift is about 3Hz and the output frequency noise is 5.46×10^-8.The work of this paper provides a complete theoretical basis and practical circuit scheme for the realization of silicon micro resonant pressure sensor system,and also lays a foundation for the follow-up research.