Study On Digital Signal Demodulation Technology For Quartz Rate Sensor

Quartz tuning fork gyroscope or Quartz rate sensor (QRS) is a new kind of micro-mechanical vibratory angular rate sensor. As it has so many advantages such as low cost, small size, high reliability, long life and the ability to survive in harsh environment, its applications in both military and civil field are expanding. Moreover the development of micro-inertia measuring units (MIMU), which use micro-mechanical gyros as hardcore, is thriving and prosperous. The low precision of QRS is a key barrier to its widely used and how to better the performance is becoming a hot point in QRS research area.At first, the piezoelectricity of quartz crystal is explained, working mechanics of QRS is introduced based on Coriolis effect. Flexural vibratory equation of the quartz tines and driver and detected signals are analysed in detail, the modal of QRS'signals is established as well as driver and detecting circuits are studied.Then, equivalent circuit and admittance circle of piezoelectric vibrators are explained, an approach to gauge impedance of QRS'equivalent circuit is brought forward, the equation of admittance circle is acquired using a revised least squares method, the reciprocal of conductance–frequency plot is fitted by a least squared method with Househord transform, a new method to calculate the QRS'equavilent parameters is proposed and an experiment is also perfomed.And, an orthogonal vector's lock-in amplifier (LIA) is put forward to demodulate the QRS signals. After explaining the correlation demodulation principal of the LIA, it is concluded that phase-locked loop (PLL) is prior to Hilbert transform as reference channel of LIA. By rotating in-phase component and quadrature-phase component of the LIA output signals, the quadrature error is removed, then by eliminating the in-phase error and adjusting with scale factor the input rate is obtained. The digital PLL is also simulated in Simulink and single-axis gyro calibration test is performed using a rate table.At last, mechanical coupling and its impact on sense signal is narrated, the measures taken to minimize the mechanical coupling are analysed. The magtitude and phase errors, resulted from temperate and aging in driver and sense circuits, are proved theoretically and experimentally. How these errors affect the angular rate precision is discussed detailedly. Some advice is given to better the precision of QRS in measuring angular rate.