A New Data-Driven Control System for MEMSs Gyroscopes: Dynamics Estimation by Type-3 Fuzzy Systems

In this study, a novel data-driven control scheme is presented for MEMS gyroscopes (MEMS-Gs). The uncertainties are tackled by suggested type-3 fuzzy system with non-singleton fuzzification (NT3FS). Besides the dynamics uncertainties, the suggested NT3FS can also handle the input measurement errors. The rules of NT3FS are online tuned to better compensate the disturbances. By the input-output data set a data-driven scheme is designed, and a new LMI set is presented to ensure the stability. By several simulations and comparisons the superiority of the introduced control scheme is demonstrated.

ZRO Drift Reduction of MEMS Gyroscopes via Internal and Packaging Stress Release

Zero-rate output (ZRO) drift induces deteriorated micro-electromechanical system (MEMS) gyroscope performances, severely limiting its practical applications. Hence, it is vital to explore an effective method toward ZRO drift reduction. In this work, we conduct an elaborate investigation on the impacts of the internal and packaging stresses on the ZRO drift at the thermal start-up stage and propose a temperature-induced stress release method to reduce the duration and magnitude of ZRO drift. Self-developed high-Q dual-mass tuning fork gyroscopes (TFGs) are adopted to study the correlations between temperature, frequency, and ZRO drift. Furthermore, a rigorous finite element simulation model is built based on the actual device and packaging structure, revealing the temperature and stresses distribution inside TFGs. Meanwhile, the relationship between temperature and stresses are deeply explored. Moreover, we introduce a temperature-induced stress release process to generate thermal stresses and reduce the temperature-related device sensitivity. By this way, the ZRO drift duration is drastically reduced from ~2000 s to ~890 s, and the drift magnitude decreases from ~0.4 °/s to ~0.23 °/s. The optimized device achieves a small bias instability (BI) of 7.903 °/h and a low angle random walk (ARW) of 0.792 °/√ h, and its long-term bias performance is significantly improved.

Die-Level Vacuum Packaging of Mems Devices with Non-Evaporating Getters

In this article original method of vacuum packaging in ceramic package 5142.48-A with non-evaporating getter inside is described. Some MEMS devices such as gyroscopes, accelerometers and resonators often require high and stable vacuum for operational capability. It is known two main approaches to the vacuum packaging of MEMS devices: hermetization on the wafer level and on the die level. Die-level vacuum packaging can be implemented by sealing the die in ceramic package providing excellent hermeticity with sufficiently low leak rate. However, because of outgassing from materials of the package it is difficult to achieve stable vacuum over all MEMS device lifetime. To prevent vacuum degradation it is necessary to use special materials that can remove active gases from the package by chemical sorption named getters. In this work tablet-shaped non-evaporating getter with thickness of 0.7 mm made of titan-vanadium alloy with activation temperature near 525 °C was used. For the vacuum packaging workflow new special vacuum chamber is designed. It may contain four MEMS devices simultaneously. During the process of getter activation heating was provided by halogen lamps G12 35 Wplaced over the caps of the ceramic packages with a little gap. It is defined that in deep vacuum full power of one lamp can heat the cap of the package to the temperature more than 600 °C. Probable overheating is excluded by means of the newly-designed programmable device — power switch, which can maintain required temperature in automatic mode for the necessary time. Temperature control is realized by no-contact pyrometrical method. During the experiment all necessary parameters providing specified temperature profile of the process were determined. Efficiency of the developed vacuum packaging workflow is successfully confirmed by the high and stable Q-factor of fabricated MEMS gyroscopes.

Actor Critic Neural Network-Based Adaptive Control for MEMS Gyroscopes Suffering from Multiresource Disturbances

In this paper, an actor critic neural network-based adaptive control scheme for micro-electro-mechanical system (MEMS) gyroscopes suffering from multiresource disturbances is proposed. Faced with multiresource interferences consisting of parametric uncertainties, strong couplings between axes, Coriolis forces, and variable external disturbances, an actor critic neural network is introduced, where the actor neural network is employed to estimate the packaged disturbances and the critic neural network is utilized to supervise the system performance. Hence, strong robustness against uncertainties and better tracking properties can be derived for MEMS gyroscopes. Aiming at handling the nonlinearities inherent in gyroscopes without analytically differentiating the virtual control signals, dynamic surface control (DSC) rather than backstepping control method is employed to divide the 2nd order system into two 1st order systems and design the actual control policy. Moreover, theoretical analyses along with simulation experiments are conducted with a view to validate the effectiveness of the proposed control approach.

ZRO Drift Reduction of MEMS Gyroscopes via Internal and Packaging Stress Release

Zero-rate output (ZRO) drift induces deteriorated micro-electromechanical system (MEMS) gy-roscope performances, severely limiting its practical applications. Hence, it is vital to explore an effective method toward ZRO drift reduction. In this work, we conduct an elaborate investigation on the impacts of the internal and packaging stresses on the ZRO drift at the thermal start-up stage, and propose a temperature-induced stress release method to reduce the duration and magnitude of ZRO drift. Self-developed high-Q dual mass tuning fork gyroscopes (TFGs) are adopted to study the correlations between temperature, frequency and ZRO drift. Furthermore, a rigorous finite element simulation model is built based on the actual device and packaging structure, revealing the temperature and stresses distribution inside TFGs. Meanwhile, the relationship between temperature and stresses are deeply explored. Moreover, we introduce a temperature-induced stress release process to generate thermal stresses and reduce the temperature-related device sensitivity. By this way, the ZRO drift duration is drastically reduced from ~2000 s to ~890 s, and the drift magnitude decreases from ~0.4 °/s to ~0.23 °/s. This stress release method achieves a small bias instability (BI) of 7.903 °/h and a low angle random walk (ARW) of 0.792 °/√h, and the long-term bias performance is significantly improved.