| Micro hemispherical resonator gyroscope(μHRG,Micro hemispherical resonator gyroscope)combines traditional HRG technology and micro-electromechanical systems(MEMS)process has the advantages of high precision,small size,and low cost,and has broad application prospects.In recent years,due to the excellent potential of μHRG in near-navigation or navigation-level applications,it has become one of the research hotspots in MEMS inertial devices at home and abroad.However,due to the current manufacturing technology level,errors and defects in the preparation of the resonator and the micro-assembly process between the resonator and the electrode substrate are inevitable,resulting in structural errors(frequency splitting,damping mismatch and uneven mass)of the resonator and assembly errors(tilt and eccentricity).These errors will limit the performance improvement of the μHRG.The influence mechanism of mechanical structure defects and micro-assembly errors on the force-to-rebalance(FTR)and whole angle(WA)modes of the μHRG is studied in depth,and the corresponding error suppression and compensation methods are proposed to improve the performance of the μHRG.The main research work of this paper includes:(1)A real-time automatic mode matching method based on standing wave precession is proposed for the angle error of the WA mode gyroscope caused by frequency mismatch.The transfer model between angle error and mechanical gain mismatch caused by frequency mismatch is established.PIR(Proportional Integral Resonance)controller is used to suppress 2θ harmonic error,and the effectiveness of the PIR controller is verified by simulation and experiment.The effectiveness of the proposed online identification algorithm for frequency mismatch information is verified by numerical simulation and experiment.The experimental results show that after real-time modal matching,the frequency mismatch is reduced from the 570.7 mHz to 28.7 mHz,which is reduced by about 95%.At the same time,the angle error is reduced from 25.8° to 7.3°,which is reduced by 71.7%.Experiments show that the proposed automatic mode matching method can effectively suppress the angle error caused by frequency splitting in WA mode.(2)Aiming at the additional bias drift in FTR mode and WA mode caused by excitation coupling error due to assembly eccentricity,an identification method of excitation coupling coefficients based on mode reversal is proposed,and a decoupling compensator is designed.Aiming at the FTR mode(Lynch architecture),a mathematical model between the excitation coupling error and the closed-loop scale factor and zero bias is established,and the correctness of the mathematical model is verified by simulation and experiment.The expression that the excitation coupling error introduces additional angle drift into the precession angle in WA mode is constructed.The experimental results show that the bias stability(1σ)in the FTR mode is reduced from 5.587°/h without compensation to 3.362°/h after excitation coupling compensation,which is reduced by about 39.8%.In the WA mode,the angle error is reduced from 9.8° without compensation to 7.5° after excitation coupling compensation,which is reduced by about 23.5%.The effectiveness of the proposed excitation coupling error identification and decoupling compensation method is verified by experiments.(3)Aiming at the bias error in FTR mode and angle estimation error(angle drift)in WA mode caused by electrode gain mismatch caused by assembly tilt,an identification method of electrode gain mismatch parameters based on electrode static capacitance measurement is proposed.A gain mismatch compensator is designed accordingly.For the FTR mode,the mathematical model of electrode gain mismatch,closed-loop scale factor,and bias is established,and the correctness of the mathematical model is verified by simulation and experiment.Aiming at WA mode,an error transfer model between electrode gain mismatch and angle estimation error(angle drift)is established.The experimental results show that the bias stability(1σ)in FTR mode is reduced from 3.362°/h without compensation to 2.022°/h after gain mismatch compensation,which is reduced by nearly 39.9%.In the WA mode,the angle error is reduced from 7.5° without compensation to 2.4° after gain mismatch error compensation,which is reduced by 68%.Finally,after adopting the above-mentioned frequency matching,excitation coupling compensation,and electrode gain mismatch compensation in the FTR mode,the performance of the scale factor and zero bias of the μHRG prototype is tested at room temperature.Experimental results show that the average value of the scale factor is 100582 LSB/(°/s)within the range of±80°/s.The average value of bias stability(1σ)is 2.2284°/h,and the average value of angle random walk is 0.1401°/(?).(4)Aiming at the bias drift caused by asymmetric damping in FTR mode,a bias drift compensation measurement,and control system based on alternating pseudo-rotation modulation is designed and implemented.The problem of zero bias drift of μHRG in FTR mode caused by damping mismatch is expounded.Simulation analysis and experiment study the open and closed-loop relationship between the driving force and pseudo-rotation rate.The principle of zero-bias modulation based on pseudo-rotation is studied,and the limitations of unidirectional pseudo-rotation zero-bias modulation are revealed.The FTR gyro’s zero drift compensation measurement and control system based on alternating pseudo-rotation modulation is designed and implemented.The experimental results show that the rate integral of gyro bias in 3 hours at room temperature in the FTR mode is reduced from 600° without rotation to 50° under alternate pseudo-rotation.Experiments show that the method based on alternating pseudorotation modulation can significantly improve the long-term drift of bias. |
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