Micro Scale Angular Rate Sensors
Ph.D. student of Prof. Slava Krylov
Wednesday, July 15, 2020 at 14.00
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The meeting will be recorded and made available on the School’s site.
Micro-gyroscopes based on microelectromechanical systems (MEMS) technology became an indispensable component of many engineering systems starting from computer games and mobile phones and up to autonomous cars, drones and wearable medical devices. In the past 20 years, the use of micro-gyroscopes gradually become more widespread also in the field of navigation, guidance and control. In this arena, tactical and inertial grade gyroscopes are often required to operate in harsh environments while preserving their key sensing characteristics. This is very challenging task, which continues to stimulate an extensive research in both academia and industry. In the present work, several architectures of inertial micro sensors were introduced and explored. The goal was to investigate a possibility to improve the robustness of the devices to the environmental factors using the suggested designs.
In the talk, the key aspects of the modeling, design, fabrication, integration and characterization of a novel, tactical-grade, single axis tuning fork gyroscope will be presented and discussed. The device is distinguished by a combination of two detection techniques – capacitive and optical – in the same fully functional, robust, single crystal Si, vacuum packaged device with integrated electronics. The goal of the research, mainly focused on the design and modeling of the mechanical core of the device, was to investigate the feasibility of the suggested architecture and sensing approach and their potential for a possible performance/robustness enhancement.To measure the sensor's main figures of merit an extensive rate-table performance study was carried out. The adopted approach allowed the achievement of tactical grade performance of the sensor and excellent values of bias instability (BI) parameter lower than 0.7/h. The device also demonstrated low thermal sensitivity with the scale-factor deviation of less than 0.01% for the of 100 C temperature range. The carefully designed dynamically balanced architecture resulted in highly improved Q-factor of 140000One of the approaches allowing improved performance of micro gyros is to exploit more efficient actuation. In the framework of the research, a new approach allowing excitation of large amplitude vibrations through the parametric resonance (PR) mechanism was introduced and investigated.The main distinguished feature of the suggested approach is that the PR is excited though the inertia (rather than commonly used stiffness) modulation. We demonstrate, using the model, that modulation of 12% in the moment of inertia can be achieved in a multi-DoF tilting device. Our model results indicate that the PR-based driving of the two DoF structure allows to maintain the almost constant resonant amplitude within the frequency range of more than 200 Hz. Devices of several configurations were designed, fabricated from the silicon on insulator (SOI) substrates and characterized. The suggested inertia modulation paradigm can be implemented in various inertial sensors including micro gyros as well as frequency sensors based on a mechanical heterodyning principle.