Research On Structural Design Of MEMS Cobweb-like Disk Resonator Gyroscope

MEMS vibratory gyroscope is an angular velocity sensor based on micromachining process and Coriolis force.Because of its unparalleled advantages in size,power consumption and cost,it is widely used in consumer electronics,automotive safety and industrial automation.However,accuracy of MEMS vibratory gyroscopes is currently limited by their own size constraints and processing techniques,and it is difficult to meet the needs of high-end application markets.Therefore,achieving high-precision MEMS vibratory gyroscopes is one of the most important research topics.Modal degeneracy and high quality factor are the main ways to achieve high-precision MEMS vibratory gyroscopes.Among them,disk resonator gyroscopes is the most accurate potential MEMS degenerate gyroscopes.However,the large relative process tolerances in the manufacturing process will introduce structural errors such as frequency split and damping asymmetry,resulting in reduced sensitivity and worsened bias performance.In addition,some energy loss mechanism limits the realization of high quality factor(Q).Therefore,in order to solve these problems as much as possible,this thesis,which takes the disk resonant gyro structure as a reference on the basis of the analysis of gyroscope dynamics,makes full use of the physical characteristics at the micro scale,and deeply explores the design method of high symmetry and high precision MEMS gyroscope structure from the perspective of structural symmetry and energy loss mechanism.The main research contents and innovations are as follows:1.Research on frequency symmetry of the MEMS cobweb-like disk resonator gyroscope.Based on the theoretical model of frequency split of MEMS disk resonator gyro,the influencing factors of frequency symmetry are determined.After discussing the origin of MEMS technology and the characteristics of mask technology,it is the first time to put forward the assumption that the tolerance of the linear structure is less than the arc structure.Based on this assumption,a cobweb-like disk resonator gyroscope(CDRG)with a full linear structure is designed.To compare as-fabricated structural symmetry,CDRGs and ring-like disk resonator gyroscopes(RDRGs)with similar frequencies have been processed side by side on the same wafer.Finally,the theory,simulation and experimental results are compared to verify this idea.Experimental data shows that the minimum as-fabricated relative frequency split of CDRGs is only 29.9ppm,with an average value of 79.1ppm,less than 1/7 of RDRGs.It is a kind of gyroscope structure with the minimum mean value and fluctuation range of as-fabricated relative frequency split among the MEMS axisymmetric gyros reported in the literature so far.Its excellent frequency symmetry can achieve low-voltage modal matching,reducing the difficulty of ASIC measurement and control circuit integration.2.Research on the energy loss mechanism and damping asymmetry of the MEMS cobweb-like disk resonator gyroscope.In view of the problem that some energy loss mechanisms limit the improvement of quality factor,the theoretical models of energy loss mechanisms of a cobweb-like disk resonator gyroscope have been comprehensively established.Firstly,based on the modified continuous fluid model and the energy transfer model,an analytical model of air damping of cobweb-like disk resonator gyroscope is derived;and Q value of thermoelastic damping is estimated based on the Zener's analytical model and the COMSOL finite element model,respectively,and then Q value of anchor damping solved using the perfect matching layer method.Finally,Quality factor of the cobweb-like disk resonator gyroscope is tested and verified.The estimated Q value of theoretical model of total energy loss mechanism corresponding to the energy transfer model is very consistent with the experimental results.And the error of the quality factor temperature coefficient of the experimental and theoretical models does not exceed 2%.In addition,the crystal orientation error model and the non-uniform ring-width equivalent error model are proposed for the first time to analyze the mechanism of damping asymmetric error,which is partially consistent with the experimental results.3.Structural characteristics analysis and performance test of MEMS cobweb-like disk resonator gyroscope.From the perspective of realizing a high-performance gyro structure,the dynamic characteristics and anti-impact ability of MEMS cobweb-like disk resonator gyroscope are analyzed by mode superposition method and overload stress method.The structure size of resonator is determined by parameter method,and the mathematical model of electrostatic excitation and capacitance detection of capacitance transducer is deduced.The nonlinear characteristics of the structure are studied,and it is found that the designed capacitance transducer can effectively reduce the nonlinear effect under the amplitude amplification effect of the resonator.Finally,the performance of CDRG and RDRG are tested and compared.In the force-to-rebalance mode,the best performance of the CDRG when locked at the maximum displacement: the scale factor,random angle walk and bias instability are 98.1m V/(°/s),0.004°/?h,and 0.187°/h.Compared with RDRG,the scale factor,angular random walk,and bias instability of CDRG are improved by 112%,700%,and 314%,respectively.All these indicate that MEMS cobweb-like disk resonator gyroscope has great potential for realizing high-precision gyroscope.