Research On Close-loop Detection Technology Of MEMS Axisymmetric Gyroscopes

In recent years,axisymmetric resonator gyroscopes have attracted much attention due to its potential advantages in symmetry of resonant structure,minimization losses of energy transfer between drive and sense modes and immunity to external vibrations.As one of the axisymmetric resonator gyroscopes,disk resonator gyroscope(DRG)has the characteristics of high thermal stability,large transducer area and low anchor loss.In this paper,a readout circuit with high signal-to-noise ratio(SNR),a force-to-rebalance detection circuit with adjustable scaling factor and an automatic mode-matching circuit are designed for cobweb-like disk resonator gyroscopes(CDRG).Compared with conventional circuit,the readout circuit in this paper combines driving and sensing electrodes to improve the utilization of capacitance,and the concept of decay factor is put forward for force-to-rebalance circuit,which not only realizes the adjustability of scale factor,but also reduces the system noise to a certain extent.Firstly,the different methods of interface circuits are studied and the noise of the readout circuit is analyzed in detail.According to the structure characteristics of gyroscope,a high SNR interface circuit suitable for CDRG is designed.Secondly,the driving loop,force-to-rebalance circuit and automatic mode-matching circuit are introduced respectively.Especially,the scale factor and noise of force-to-rebalance circuit are deduced theoretically,and the concept of decay factor is proposed to improve scale factor and optimize the performance of detection circuit.Experimental tests have been carried out in this paper.The experimental results show that the resonant frequencies of drive and sense modes are 18718.96 Hz and 18719.52 Hz respectively,and the quality factors are 112392 and 113041,respectively.The noise of the analog interface circuit is tested to be 0.14aF/?Hz,corresponding to the angular rate equivalent noise of 0.0085°/?h,which is less than the mechanical thermal noise of gyroscope.The scale factor of force-to-rebalance circuit increases from 7.9 mV/°/s to 19.1 mV/°/s with a decay factor,the bias instability of gyroscope improves form 11.19°/h to 7.46°/h.And the instability can be further reduced to 0.75°/h by mode-matching.