Structural Design And Process Reserch Of Grating MEMS Gyroscope Based On Grating Self-imaging

As a kind of micro sensor to measure the angular rate of the carrier,MEMS gyroscope is widely used in inertial navigation,attitude control and stable control platform due to its small size,low power consumption,low cost and other advantages.The current mainstream MEMS gyroscopes are mainly based on capacitive detection,and due to parasitic capacitance and pull-down effects,their accuracy has reached its limit level,making it difficult to break through.In order to further improve the accuracy of MEMS gyroscopes and combine the advantages of grating detection accuracy limit higher than capacitive detection,this paper studies the structural design and key process research of MEMS gyroscopes based on grating self imaging effect.The main content is as follows:(1)Detection mechanism and simulation design of grating self-imaging effect MEMS gyroscope.When the gyroscope perceives external angular velocity,the lower grating is driven by the mass block under the action of Coriolis force,and based on the self-imaging effect of the double-layer grating,the angular velocity information can be obtained by detecting the diffraction light intensity change of the double-layer grating.Through theoretical and simulation design,the optimal size of the structure and the double-layer grating of the MEMS gyroscope were achieved.The simulation results showed that the driving frequency of the gyroscope was 8146.7Hz(off-plane)and7720Hz(in-plane),and the detection frequency was 8147.8Hz(off-plane)and7719.6Hz(in-plane).The quality factors of the driving direction were 1257.8(off-plane)and 855.7(in-plane),and the quality factors of the detection direction were 3850(offplane)and 1393.2(in-plane).The sensitivity of the grating MEMS gyroscope was6.97 m V/°/s(off-plane)and 22.81 m V/°/s(in-plane)..(2)Grating MEMS gyroscope process and manufacturing.This mainly includes designing the MEMS process flow,conducting in-depth research on the high-precision grating preparation process and the low-side-etching cantilever beam etching process,and finally characterizing and testing the grating MEMS gyroscope structure.The results show that the manufacturing error of the MEMS gyroscope can be kept within5.7%,which verifies the feasibility of the manufacturing process.(3)Modal matching control of grating MEMS gyroscope.By testing,the driving and detection frequencies of the gyroscope were 7083 Hz and 7112 Hz respectively(compared with the simulation results,the maximum relative error was 8.3%),and the quality factors were 810.3 and 1059.1.In order to reduce the impact of gyroscope manufacturing errors on gyroscope sensitivity,a tuning method based on electromagnetic driving is proposed,that is,applying a bias voltage to the ends of the driving wire to make the gyroscope driving beam produce tensile stress and change the characteristic frequency.The experimental results show that when the bias voltage is4.6V,the driving frequency can be tuned to 7111 Hz,and the frequency difference is less than 1Hz,which verifies the feasibility of the electromagnetic driving tuning method for MEMS gyroscopes,and provides powerful support for realizing highprecision MEMS gyroscope inertial measurement.