Research On Force Balance Control And Error Suppression Technology Of Vibrating Ring Silicon Microgyroscope

Micro vibrating ring gyroscope is a two-dimensional axisymmetric structure solid fluctu-ation gyroscope that evolved from a three-dimensional hemispherical resonant gyroscope.On the premise of inheriting the characteristics of hemispherical resonant gyroscope such as high accuracy,high reliability,long life,and overload resistance,it is compatible with the current mainstream MEMS processing technology,and thus has better CSWa P,and has an extensive application prospect.Therefore,the vibration ring gyroscope has become one of the research hotspots of MEMS gyroscope.The force balance control(FBC)method is currently the best working method for the static performance of the MEMS gyroscope.Still,the presence of unavoidable processing errors destroys the ring resonator’s structural symmetry and limits the performance potential of the ring gyroscope.This paper aims to improve the performance of the vibrating ring silicon micro-gyroscope and suppress errors in the force balance measurement and control system of the ring gyroscope.The main work of this paper is described as follows.(1)A ring gyroscope detection and control system based on FBC is developed.The structural form,electrode configuration,fabrication process,and measured mode parameters of the multi-ring resonator are analyzed.The principle of ring resonator excitation and detection is analyzed by the micro-element method,and the functions of electrodes at different axis angles are clarified.The accuracy and stability of the ring gyroscope detection and control system based on FBC are demonstrated using simulation combined with experimental.The amplitude stabilization control and frequency following of the drive mode are performed,and the closed-loop control of the detection mode is completed.(2)The influence of principle inertial acceleration error,non-principle structure error,and non-principle phase error of the ring gyroscope on the FBC method is analyzed.The effects of implicated tangential inertial acceleration,implicated centripetal inertial acceleration,and coupled interference inertial acceleration on the force balance detection and control system are analyzed from both the drive and detection modes.A more comprehensive(including mass error,damping error,stiffness error,and electrode angle misalignment)kinetic equation of the ring gyroscope is established.The structural error’s perturbation of the drive and sense modes are investigated,and the scheme to suppress the quadrature coupling error is proposed.The disturbance of phase delay error on the signal extraction and closed-loop control of the detection and control system is analyzed,and the suppression scheme of the phase delay error is proposed.(3)A structural error suppression system with real-time mode frequency tuning and closed-loop quadrature stiffness correction based on multiplier excitation signals is designed and im-plemented.The mechanism of the influence of mode frequency split and quadrature stiffness coupling on the detection mode of high-quality factor ring gyroscope is revealed.The prin-ciple of the ring gyroscope to achieve the electrostatic stiffness correction and its coupling phenomenon is analyzed.The prerequisites for mode frequency matching are clarified,and the implementation steps of frequency matching in the presence of the above coupling are proposed.The frequency split information is obtained online by the multiplicative excitation method and combined with quadrature stiffness correction to realize the self-matching,and the experiments of structural error suppression are carried out.The experimental results show that the zero-bias instability is improved by 2.93 times,and the angle random walk is improved by 12.18 times after the structural error suppression.(4)A closed-loop detection bandwidth expansion and scale factor repeatability error sup-pression method based on an equivalent unit negative feedback loop is proposed.The equivalent unit negative feedback system is obtained by the equivalent transformation of the FBC structure.Based on the correlation between the cutoff frequency of the open-loop transfer function and the bandwidth of the feedback system,the force balance controller is redesigned to increase the cutoff frequency and ensure a suitable phase margin to expand the bandwidth from less than 5Hz to 20Hz.Based on the gain characteristics of the equivalent unit negative feedback system,a method is proposed to suppress the scale factor repeatability error,which reduces the error by 59%.The causes of the scale factor nonlinearity and asymmetry are analyzed,and the suppression ability of the FBC method on the above two types of errors is experimentally demonstrated.(5)The performance test of the ring gyroscope principle prototype based on the FBC method was conducted.The gyroscope’s test results at room temperature are as follows.The scale factor is 2488.284LSB/（？）/s,the nonlinearity is 61.713ppm,the asymmetry is 35.936ppm,the repeatability is 75.423ppm over a range of±100（？）/s;the zero bias is 0.077（？）/s,the zero bias instability is 0.852（？）/h,the angular random walk is 0.044（？）/~√h;the bandwidth is 20Hz.The vibrating ring gyroscope used in this paper is the first prototype developed by our team.The resonant structure needs to be further optimized,and there is still much room for improvement in mechanical sensitivity and quality factor.Nevertheless,the work in this paper provides an effective technical way for further research and performance improvement of the ring gyroscope force balance detection and control system,and has some reference significance for the error analysis and suppression of axisymmetric gyroscope.