Research On Vibration Characteristics Of Pressure Sensor With Micro Cross Resonator

The micro resonant pressure sensor is widely used in engineering practice because of its simple structure,high sensitivity and stable operation.In order to further improve the sensitivity of the pressure sensor,a method of reducing the dimension of resonator is usually adopted,which not only increases the manufacturing difficulty of the resonator,but also leads to the weakening of the output signal and increases the complexity of the detection system.Therefore,without changing the structure size of the resonator,further improving the detection sensitivity of the pressure sensor has become the focus of researchers.Based on this problem,a micro cross resonator pressure sensor is proposed and the resonant characteristics are studied.Under the consideration of electrostatic force,air damping force and molecular force,micro cross resonator is simplified into a multi-field coupling vibration model.The dynamic equation is established and the frequency equation and mode function of the resonator are derived.The modes and natural frequencies of micro cross resonator are solved,and the changes of the natural frequencies of cross resonator with structure parameters,bias voltage,molecular force and external pressure are analyzed.When the length of the resonator increases or the distance between the plates decreases,the natural frequency of the resonator decreases.When the external pressure and electrostatic force increase,the natural frequency of the resonator increases.The smaller the plate distance is,the greater the effect of molecular force on natural frequency is,and the effect of molecular force on low order natural frequency of resonator is obviously greater than that of high order.The nonlinear vibration equation of micro cross resonator is built,the sensitivity expression of micro cross resonant pressure sensor is derived,and nonlinear vibrational frequency of the resonator is solved by multi-scale method.The effects of dimension parameters,external pressure and Van der Waals force on nonlinear natural frequencies are studied.By Linztade-Poincare method,nonlinear time domain response function and amplitude-frequency characteristic curve of the resonator are obtained.The influence of multiple physical field parameters on the time domain response of the resonator,as well as the corresponding relation between different excitation frequencies and amplitude are analyzed.When the thickness of the resonator is thin,the distance is small and the length is large,nonlinear natural frequencies are greatly affected.The smaller the plate distance and the thinner the thickness of resonator are,the faster the excitation frequency decreases with the increase of the amplitude,moreover,the amplitude jump is easy to occur.The lower plate is thinner and the length of the resonator is shorter,the sensitivity of the pressure sensor is higher.A micro cross resonator and a micro straight resonator are fabricated by micro machining technology and assembled to be resonant pressure sensors.Using the metal stripping technology,the excitation end of the resonator is separated from vibration pickup end,so that the output voltage signal is not doped with excitation signal,and then the result is more accurate.Based on Owen bridge,low-frequency open-loop detection circuit of micro cross pressure sensor is designed,and low-frequency closed-loop detection system is developed by using phase-locked technology.A high-frequency detection system with reverse phase gain module is designed to improve the sensitivity of the sensor by adjusting the gain.By electrostatic excitation-capacitance detection method,open-loop frequency sweep experiments are carried out on straight and cross pressure sensors,and external pressure is applied to test the sensitivity of the sensor.The results show that output voltage amplitude of cross-type pressure sensor is larger,the frequency signal is more stable,and the ability to resist environmental interference is strong.The range of the pressure sensor in this paper is 0～210 k Pa.After using the feedback gain,the equivalent mass of the resonator can be reduced without changing actual size of the resonator,so as to improve natural frequency of resonant pressure sensor and achieve the purpose of improving detection sensitivity of micro cross resonant pressure sensor.The pressure test results show that the sensitivity of cross resonant pressure sensor increases from 11.15 Hz/k Pa to 210.80Hz/k Pa after adjusting the feedback gain,which verifies the correctness of feedback measurement and control technology used.