Research of Processing Errors on Modal Frequency of a Dual-mass Decoupled Silicon Micro-gyroscope

In this paper, the architecture, processing errors analysis and optimization method of a dual-mass silicon micro-gyroscope are presented. The dual-mass silicon micro-gyroscope consists of two identical single mass gyroscopes and a lever mechanism. Driving decoupling springs and sensing decoupling springs are key components to achieve motion decoupling. The processing error analysis indicates that the main influence of processing errors on modal frequency are width error of spring beams. The optimization method which increases the width of spring beams is adopted to reduce the effect of width errors on modal frequency. The structure optimization simulation results demonstrate that the frequency difference variation resulting from the processing errors decreased from 53.45% to 7.08% by increasing the width of spring beams. Introduction Silicon micro-gyroscopes are novel gyroscopes based on the MEMS technology. The application domain of these sensors is rapidly expanding from automotive to consumer electronics and personal navigation systems. Low cost, small size and easy integration make silicon micro-gyroscopes ideal for use in many fields. There are no MEMS gyroscopes meeting the requirement of inertial-grade, but from the trend in reported gyroscopes we can confirm that inertial-grade gyroscopes will exist in the near future. In order to improve the performance of silicon micro-gyroscope, error sources should be well identified. One of the most important error sources are the processing error.[1] In this paper, the processing error of a decoupled dual-mass silicon micro-gyroscope is analyzed by ANSYS. Basing on analysis results, we propose an optimization method to decrease the influence of processing error on modal frequency and implement simulation verification. Principle of decoupled dual-mass silicon micro-gyroscope A schematic drawing of the micro-gyroscope is shown in Fig .1(a). It consists of two identical single mass gyroscopes, which are connected by driving spring to shape a whole structure. On the top and bottom of the structure, there are two sets of levers in order to suppress the in-phase sensing modal and amplify the anti-phase driving modal. The decouple principle is shown in Fig.1(b). The electrostatic driving force is applied on the driving electrodes. Two driving frames and proof masses on the left and right sides will be driven against each other. Since the stiffness of driving decoupling spring in the driving direction is flexible, sensing frames keep static in driving direction, Joint International Mechanical, Electronic and Information Technology Conference (JIMET 2015) © 2015. The authors Published by Atlantis Press 426 so the driving decoupling will be achieved. When an external angular rate around z-axis is input, two masses are driven into a vibrating motion by the Coriolis forces. Since the stiffness of sensing decoupling spring in sensing direction is flexible, driving frames keep static in sensing direction, so the sensing decoupling will be achieved. Sensing Cmbo Driving Decoupling Spring Sensing Frame Sensing Spring Driving Sensing Frame Driving Coupling Spring Base beam Sensing Decoupling Spring Anchor Sensing Coupling Spring Lever beam Driving Sensing Comb