Survivability in shock environment is an important reliability index of silicon micro-gyroscope. Shock response of dual-mass silicon micro-gyroscope is investigated in this paper. A lumped mass model was established for the micro-gyroscope based on the characteristics of the dual-mass structure. Analytic solution to the response of the structure under shock load in a half-sine acceleration form was then acquired. The analytic solution was applied to calculate the shock response of a well designed dual-mass silicon micro-gyroscope in our laboratory, while the correctness of it was verified with finite element method (FEM) in ANSYS. The analytic solution is serviceable in reliability prediction of dual-mass silicon micro-gyroscope in shock environment.
This paper studies the control theory and the methods of the silicon micromachined resonant accelerometers(SMRAs). According to the structure and movement of the resonant accelerometer, the model of its dynamics and the equations of motion are deduced. The model of the closed-loop control is set up with the phase lock loop (PLL). The principle of PLL is expounded in detail. The requirements for phases and gains of the sinusoidal self-drive-oscillation are met by PLL. The average method is to take the average of slowly changing variables within a cycle to find the solutions of nonlinear equations. Using the average method, it analyzes the PLL’s phase control methods in depth and derives the system stability condition. The simulation results verify the correctness of the stability condition. It provides a guiding theory for the realization of SMRA’s precision control.
This paper presents an enhanced lift-off process for forming side electrode on the quartz –based double-ended tuning fork (DETF) resonator. In the case of fabricating quartz-based DETF, electrode pattern design is an important issue. Taking advantage of the piezoelectricity effect, a simple surface electrode can excite the flexural motion of the DETF, however it suffers from the large motional resistance. Proposed lift-off process can pattern excitation electrode on the side wall without using special photolithograph equipments. Experimental results demonstrated that the motional resistance can be reduced by several times by forming side electrode using proposed process.
Packaging thermal stress is harmful to the performance of the micromechanical silicon resonant accelerometer. In order to decrease the packaging thermal stress, correlations of packaging thermal stress with the material properties, curing temperature and geometrical size of adhesive layers of adhesive materials were discussed. A finite element model of package was developed to analyze the influence of surface mounting technology (SMT) on the micromechanical silicon resonant accelerometer. The simulation results show that the Young’s modulus, thermal expansion coefficient, curing temperature and geometrical sizes of adhesive layers are important influencing factors for packaging thermal stress and the warpage of the chip. The thermal stresses during the process of SMT will cause the resonant frequency shift.
A micro-heater is used inside silicon micro-gyroscope to keep the working temperature of gyroscope constant so as to minimize the effect of environment temperature on performances of gyroscope. The structure of gyroscope package is first given. With a heater inside, the characteristics of gyroscope, such as frequency, coupled vibrations, temperature distribution and thermal equilibrium time, are predicted with the aid of ANSYS, a finite element tool. Finally, surfaces of the package are optimized with anti-radiation shields covering. As a result, when gyroscope is subjected to an ambient temperature of 20°C, the temperature of itself could reach the equilibrium state of about 84°C within 2 minutes with a temperature difference of about 2°C between the anchor and the proof mass. Besides, if ambient temperature increases from -40°C to 80°C, heating power consumption is degraded from 1.27625W to 0.09712W. However, this design needs further improvement to decrease its heating power consumption and equilibrium time.
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