Cotrolling Technology Of Driving Stability For Micromachined Quartz Tuning Fork Gyroscope

The micromechanical gyroscope is a new kind of MEMS vibratory angular rate sensor. It is gradually used in military and commercial fields widely because of its small size,light weigh,low power consumption,high ability of anti over loading and available for formidable working condition. However.But it is still classified to category of low gyroscopes because of its low accuracy, and now it can not be applied at occasions that have higher requirements, so promoting its accuracy becomes a critical problem which a researcher needs to account for. Quartz tuning gyroscope is one kind of micromechanical gyroscopes, which is composite of gyroscope watch,drive circuit and sense circuit. This paper choose quartz tuning fork gyroscope to investigate, getting the gyroscope's equal parameters, finding out the gyroscope's best operating point, realizing the gyroscope's PLL-driving control and improving the stability of the gyroscope's sense signal. In this paper, main contents are showed as follows:1.Analyze the equivalent circuit of the gyroscope,deduce the viewpoint that the current in series branch circuit is equivalent to the oscillation velocity,and introduce the admittance circle and its application at determining the resonant frequency of the gyroscope;2. Analyze the influence of the capacitance characteristic of sampling resistance in the real application circuit to the solution of resonant frequency of the gyroscope. The capacitance characteristic of sampling resistance makes the phase-frequency curve shift, the shift makes the three resonant frequencies of the gyroscope that measured in practical situation different from the theoretical values; Introduce the least-squares procedure based on Householder-transform; Design the sweep-frequency platform based on the LabView software; Build two models of the gyroscope taking and not taking account of equivalent capacitance of the sampling resistance. Get the gyroscope's two groups of equal parameters of using least-squares procedure according to the sweep-frequency result. Make use of the equal parameters to simulate and then compare with the real results,getting the conclution that:the capacitance characteristic of sampling resistance shifts the phase-frequency curve of the gyroscope, and inorder to get the gyroscope's equal parameters precisely the capacitance characteristic of sampling resistance must be considered.This is a innovative point3. Determine the best operating point of the gyroscope from the drive end and sense end respectively according to the equivalent parameters of the gyroscope. In the drive end , gyroscope has different performance at different frequency point. And the best amplitude stability of the driving oscillation velocity will be achieved at resonance frequency by analsys in theory ,so the resonance frequency is the best operating point ;In the sense end , the best operating point is where the gyroscope's sensitivity-out is the best having the same rate in.Through gyroscope's parameters, the best frequency in the sense end is got ,and it is consistent with the resonance frequency .So the resonance frequency is gyroscope's best operating point in both gyroscope's drive end and sense end. Finding the best operating point in in both gyroscope's drive end and sense end is another innovative point.4. Analyse the insufficiency of the drive method using square wave. The radio-frequency component in the square wave influences sense output through variable coupling. And present the experiment result that shows the wobble in the the series branch current of the gyroscope because of the differential effect of the static equivalent .Design the pll control methods based on Labview and locking-in amplifier.Using these two mathod make the gyroscope librating at different resonant frequencies. The sense signal is mostly stable when the gyroscope librates at the series resonant frequency .The standard deviation of sense output signals are 6.167353e-005v by pll control methods based on Labview and 6.596771e-005v by pll control methods based on locking-in amplifier.But the sampling rate of pll control based on locking-in amplifier is apparently higher than that based on the Labview software, so the quartz tuning fork gyroscope's ideal control method is the pll control method based on locking-in amplifier.