The Optimal Design Of The Wafer-Level Vacuum Package Butterfly Vibratory Gyroscope

Gyroscope is a sensor used to measure the angular velocity of moving carrier relative to inertial space.It has been widely used in military and civil fields and has become a key part of the intelligent system.MEMS gyroscope has the remarkable structural advantages such as small size,high reliability,low power consumption,low cost,easy batch manufacturing and so on.It has especially suitable for applications with high demand and low cost which have great attention by many countries.In this paper,the Butterfly vibratory gyroscope(BFVG)is taken as the research object.In order to improve the performance of the BFVG and adapt to the large-size wafer batch technology,the miniature structure of the BFVG is improved and designed.The dynamic theory analysis,structural optimization design,tolerance analysis,quadrature error control and so on are studied.The main contents are as follows:1.Based on the engineering-oriented high-performance and miniaturized BFVG as the research object,the sensitive structure of the BFVG is optimized and designed,and the working principle of the BFVG's sensitive structure is described.A theoretical model of the performance of the driving mode's vibration amplitude and sensing mode's sensitivity of the BFVG is established.The theoretical performance parameters of the BFVG are calculated,and the performance index of the miniaturized BFVG is proposed,and the design performance target is provided for the subsequent specific structure optimization design.The mechanism of nolinear vibration system of gyroscope is introduced,and the nonlinear theoretical modeling of the driving mode and the sensing mode are established.2.The structural optimization design and tolerance capability analysis of the miniaturized BFVG are carried out.The size of the BFVG is reduced by 4 times,so that the structure of the inclined beam is more sensitive to the size error caused by the fabrication process,and the overall performance of the BFVG is greatly influenced.The influence mechanism of the fabrication errors on the zero-bias stability of the BFVG is studied.The internal relation between the main error of the vibration oblique beam and the important performance index of the BFVG is quantitatively analyzed.The design of the cross-section of the vibration oblique beam of the BFVG and the reasonable design of the fabrication process steps are optimized.The tolerance capability analysis method of the BFVG's sensitive structure is studied.The specific size of the cross-section of the vibration oblique beam is optimized.3.The stress-release structure of the miniaturized BFVG is optimized.The influence of the thermal stress,the structural stress and the temperature change on the performance of the BFVG are studied and analyzed.Through theoretical analysis,the inherent characteristics of the gyroscope,such as modes frequencies and frequency mismatch,are affected by the change of the ambient temperature.A new folding stress-release structure is proposed.The optimum dimension parameters of the stress-release structure are determined by optimizing the size of the structure.4.The mechanism of the quadrature error and the mechanism of the influence on the zero-bias stability of the miniaturized BFVG are analyzed,and the model of the mode coupling is established.The zero-bias output signal caused by the quadrature error signal is mixed with the actual angular velocity detection output signal of the BFVG,so that the signal-to-noise ratio of the BFVG is seriously affected,and the performance of the BFVG is limited.The influence of the fabrication process on the quadrature error and the sensitivity of the BFVG are analyzed.The method based on the quadrature error static correction is proposed to realize the suppression of the quadrature error of the BFVG.The electrode structure of the BFVG is optimized and designed,and the quadrature error compensation electrode is additionally arranged.5.The fabrication processes of the miniaturized BFVG are designed,and the preliminary characteristics of the BFVGs are tested.The engineering level of the 6-inch vacuum package gyroscope is evaluated,including the size error,the resonant frequency,the Q value and the quadrature error quantity.The repeatability and consistency of intrinsic characteristic parameters of the BFVGs are measured,and the performances of the BFVGs are estimated by measured datas.The thermal stress experiment and electrostatic correction measurement and control experiment of the BFVGs are carried out to verify the validity of the stress-release structure and the quadrature error control.Finally,the zero bias stability of the BFVG is tested.The nonlinear vibration effect of the BFVG is tested to verify the accuracy of the nonlinear theoretical modeling of the modes.The Allan variance of the BFVG is up to 0.56o/h.