Study On The Formation Mechanism And Suppressing Techniques Of Quality Defects In Micro Hemispherical Resonator Gyroscope

High-performance micro gyroscope is the core sensor of positioning and navigation system for micro unmanned platform,cluster guided ammunition,individual navigation and other equipments,which has a wide range of application requirements.The micro hemispherical resonant gyroscope(MSRG)is developed on the basis of the traditional macro hemispherical resonant gyroscope,which has the advantages of high precision,small volume and low power consumption.It is one of the most important development directions among high-performance MEMS gyroscopes in the future.With the structural sizes and volume of the MSRG obviously decreasing,the manufacturing errors become more prominent,which manifests as the quality defects including frequency split and damping asymmetry in working modes.Quality defects will directly cause the zero bias drift of the output of the gyroscope and seriously restrict the improvement of the comprehensive performance.At present,there is a lack of systematic research on the formation mechanism and suppression methods of quality defects in MSRG at home and abroad.This paper focuses on the basic theory and key technologies such as the influence law of quality defects,the formation mechanism and suppression methods of the frequency splits and the damping asymmetry,so as to provide important technical support for the independent development of high-performance MSRG in China.The main contents are as follows:1.The dynamic model of MSRG with quality defects.The general structure and operating principle of the MSRG are introduced,and the natural frequency,quality factor,effective mass and angular gain are analyzed.The formula for calculating the natural frequency is deduced and the damping mechanism containing air viscoelastic damping,surface damping,thermal-elastic damping,support damping and internal friction loss including is analyzed.The dynamic model of MSRG is established based on the Lagrange energy method.Then,the quality defect errors are introduced,and the influence of the damping asymmetry and frequency splits on the bias output of the gyro is discussed.2.The formation mechanism of quality defects in MSRG.The main manufacturing process is introduced.The material defects and manufacturing geometric errors of the resonator is analyzed by finite element method(FEM).The disturbance model of the influence of uneven distribution of mass and stiffness on natural frequency is established.The formation mechanism of different harmonic manufacturing errors to frequency splits and damping asymmetry of the resonator is studied.The identification system of main modal characteristics parameters including modal angle,frequency splits and quality factor is established based on frequency sweep method and energy decay method.3.Frequency matching techniques of MSRG.The theoretical model of frequency trimming based on stiffness and mass modification is derived using the quivalent model of the non ideal resonant ring.The complete trimming process including modal misalignment trimming and residual frequency trimming is proposed.The trimming accuracy within 0.1Hz is realized using femtosecond laser ablation and mass addition process.Besides,the influence of different mechanical trimming methods on the quality factor of the resonator is studied by FEM and contrast experiments.The second harmonic error and the frequency splits in operating mode are suppressed simultaneously by mechanical trimming in comprehensive multimodes.4.Damping matching techniques of MSRG.Based on the lumped mass equivalent model,the damping matching theory of the gyroscope is derived.The method of electrostatic damping tuning based on adjustable energy dissipation is studied.The influence of the voltage and resistance on the damping and frequency drift of the gyroscope is analyzed.Based on the theory of thermoelastic damping adjustment,the mechanical adjustment method of damping distribution is studied.Besides,a comprehensive adjusting method of damping distribution is obtained.5.Main performance testing of MSRG.The quality defects adjustment is carried out on MSRG fabricated by our research group.The key performance indexes of the gyroscope prototype are systematically tested.Testing results demonstrate the correctness of the quality defects adjustment methods proposed in this paper.