Simulation And Research For Digital Detection Techniques Of Weak Signal In Tuning Fork QRS

Quartz tuning fork gyroscope 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 multiplex inertia measuring units (MIMU), which use micro-mechanical gyros as hardcore, is thriving and prosperous. However, the precision of gyros can satisfy exigent applications worse and worse. This dissertation aims at weak signal detection technology in micro-mechanical gyros, and digital correlated demodulation which can improve signal detecting accuracy is simulated; Methods of compressing signal band width to improve signal-to-noise ratio and analyzing error production to decrease system error are researched. Following work has been done according to this point:1. Working mechanics of the gyro and physical theory of piezoelectricity are expatiated. According to optimum electrode collocation, electric field distribution and bearing forces of the microcosmic crystalloid unit are analyzed, which explain motivity of various vibrating modes of the quartz tuning fork2. Advantages of digital detecting for weak signal in improving accuracy are simulated and analyzed, which validates that the method of compressing signal band width to improve signal-to-noise ratio is feasible in demodulating gyros signal; different digital filters are also compared and optimally chosen3. Resonance frequency and mechanical quality factor varying with temperature are analyzed in detail and their relation is shown in a chart. The importance of temperature compensation in stabilizing output signal is indicated 4. A practical data collecting project based on sound card is designed. Demodulation for collected gyro signal indicates that the zero voltage is assignable and the linearity is not so satisfactory. Therefore more work has to be done to eliminate the nonlinearity5. Zero drift, zero shift error, phase-angular drift and random noises according to system error are analyzed. Several primary factors, such as centroid shift, non-orthogonal of drive axis and checkout axis etc, producing mechanical coupling which influence system performance greatly are declared respectivelyThe simulation reveals well that digital correlated demodulation can detect very weak signal so that it can be applied in gyros; deeply analyzing system error production is also the foundation and guidance for techniques revising and optimizing.