Study On The Electrostatic Force Control Key Technologies Of The Silicon Micromachined Butterfly Gyroscope

Gyroscope is the sensor that measures the rotational rate of a carrier. It is the basical core device in inertial navigation and weapon guide system. It has been applied abroad in many military and civil areas. Along with the deep research and rapid development of Micro-Electro Mechanical System(MEMS), silicon micromachined gyroscopes have become a major focus of wide research and development in the past decades. The silicon micromachined butterfly gyroscope is an angle vibration microgyroscope based on Coriolis effect, it has some important advantages, such as designed masterly, fabricated easily, high sensitivity, and thus has the potential to be the high performance silicon microgyroscope which can be fabricated in batches. The study on high performance silicon microgyroscope has been greatly developed abroad, but the related products and technologies are embargoed against China. In addition, most domestic micromachined gyroscopes can not meet the demands. Therefore, it is of great stratagem importance to research the key technology of silicon micromachined butterfly gyroscope for accelerating and boosting our novel measurement element.The silicon micromachined butterfly gyroscope is a complex electromechanical coupling system, whose structural precision is restricted by design level, fabrication imperfections, etc. Meanwhile, it is influenced by temperature variations, vibrations and acceleration shocks in applications. This dissertation focuses on the electrostatic force control key technologies of silicon micromachined butterfly gyroscope to improve its performance. Breakthroughs were made on the key scientific problems such as the formation mechanism of quadrature error, electrostatic force control. The research results will provide a novel compensation control theory and method for developing high performance micromachined gyroscopes. The main research contents of this dissertation are as follows:1. The mechanical structure and operation principle of the silicon micromachined butterfly gyroscope were presented, and the driving moments and Coriolis moments of the gyroscope were derived. According to the analysis of forces acting on the drive and detect directions, the basic dynamic equation was established. Then, expression of the mechanical sensitivity of the gyroscope was obtained. The steady-state responses of drive mode and detect mode were analyzed, and their characteristics were generalized.2. According to the capacitive output characteristics of silicon micromachined butterfly gyroscope, the detection mechanism of weak capacitive signal using double sinusoidal high-frequency carrier waves was studied, and the driving signal and sensing signal were successfully extracted from each other. Closed loop excitation circuit using PID controller and phase control technologies was designed, and the open loop detection circuit and angle velocity demodulation were introduced. Finally, the theoretical model of the output signal of the silicon micromachined butterfly gyroscope was obtained.3. The formation mechanism of bias stability of the silicon micromachined butterfly gyroscope was analyzed from the principle error and manufacture error. The gyroscope’s deformation error and manufacture error of the support beams were studied by using the stiffness matrix. The influence mechanism of quadrature error acting on the bias output was studied. The quadrature error is expressed as the coupling stiffness coefficient Kyx in the dynamic equation. The coupling stiffness was changed with the variation of the environmental temperature, which would make the bias output change, and deeply limit the performance of gyroscope.4. The improvement of bias stability for the silicon micromachined butterfly gyroscope based on dynamic electrostatic force balancing of coupling stiffness was presented. According to the relationship between the zero bias and the coupling stiffness, the half-close-loop control detection circuit based on dynamic electrostatic force balancing of coupling stiffness was designed. Test and comparison of the major performance specifications including scale factor, nonlinearity, bias stability, temperature sensitivities of scale factor were carried out for the micromachined butterfly gyroscope before and after improving. The results showed that the temperature sensitivities and bias instability under short in-run time were improved significantly. The bias stability is improved by 80.9%, from 89°/h to 17°/h.5. The improvement of bias stability for the micromachined butterfly gyroscope based on dynamic electrostatic force balancing control for the detection mode was presented. The dynamic electrostatic force balancing technology is based on charge injection in opposite phase, which was used to balance the charge of the Coriolis force signal, nonideal coupling error and external angular disturbance. This control manner can widen the bandwidth and measurement range, improve the linearity, and eliminate the quadrature coupling error. The close-loop control detection circuitry based on dynamic electrostatic force balancing was designed. Test and comparison of the major performance specifications including scale factor, nonlinearity, bias stability, temperature sensitivities of scale factor were carried out for the micromachined butterfly gyroscope before and after improving. The results showed that the nonlinearity, temperature sensitivities and bias instability under short in-run time were improved significantly. The bias stability is improved by 82.7%, from 136°/h to 23.5°/h.