The Analysis And Optimization Of Noise And Scale Factor Nonlinearity For Silicon Micromachined Gyroscopes

In recent years,the research of silicon micromachined gyroscope has been developed rapidly with the development of MEMS technology.And it has been widely used in military and civil fields.Based on the dual mass silicon micromachined gyroscope developed by the research group,the noise performance and scale factor nonlinearity of the gyroscope are analyzed and studied in this paper.The main contents of this paper are as follows:(1)Noise model analysis of drive circuit.Firstly,the working principle of the drive circuit and the function of each link is analyzed in detail.Then,the possible noise types in the drive circuit are pointed out,and the noise model of the drive circuit is proposed.The power spectral density function is used to analyze the noise model and discuss the influence of driving noise on the sense channel.Finally,the conclusion is that the drive-mode’s displacement noise will affect the output of the sense channel through Coriolis force in the presence of input angular velocity,and the power spectral density expression of the noise is derived.(2)Noise model analysis of sense circuit.Firstly,two working modes of the sense circuit,open-loop mode and closed-loop force feedback mode,are introduced.Then,the drive-mode’s displacement noise and the inherent noise source of the detection circuit are used to establish the noise model of the detection circuit.The power spectral density function is used to complete the analysis of the noise transmission under the two working modes,and the power spectral density of the output noise is derived respectively.Finally,the angle random walk expression is calculated through the power spectral density,the contribution of different noise sources to the output noise is clarified,and the method to reduce the noise is proposed.(3)The principle analysis of scale factor nonlinearity error.Firstly,the scale factor expressions of gyroscope in open-loop and closed-loop modes are derived.According to the parameters in the expressions,the influence on the scale factor nonlinearity is analyzed in detail,using the scale factor deviation index to reflect the influence.After the analysis,it is concluded that in the open-loop mode,the nonlinearity introduced by the displacement-capacitance conversion link and the capacitance voltage conversion link is the main factor leading to the nonlinearity of the final scale factor.In the closed-loop mode,the nonlinearity introduced by the principle is negligible,but the nonlinearity of the force feedback voltage generation circuit limits the closedloop scale nonlinearity of the gyroscope.Finally,an algorithm is proposed to compensate the nonlinearity of closed-loop scale factor.(4)Performance test of silicon micromachined gyroscope.Referring to the test rules of domestic micromachined gyroscope,the noise performance and scale factor nonlinearity index of gyroscope are tested.The experimental results show that the noise performance and scale factor nonlinearity performance of the gyroscope are consistent with the theoretical analysis results in this paper.At the same time,the scale factor compensation algorithm is verified.