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Multi-Axis Solutions for MEMS Inertial Sensors

  • Author(s): Efimovskaya, Alexandra;
  • Advisor(s): Shkel, Andrei M.;
  • et al.

Inertial Measurement Unit (IMU) integrates three-axis gyroscopes and three-axis accelerometers to provide information about position, orientation, and trajectory. For decades, IMUs based on high-end sensors have been widely used for navigation, flight control, and stabilization functions. Inspired by recent improvements in performance of MEMS inertial sensors, this Ph.D. dissertation explores a large-scale integration of discrete inertial sensors in a single micro chip solution, and introduces two approaches for a compact tactical-grade MEMS IMU.

The first approach is based on a silicon "origami-like" MEMS fabrication process, which involves fabrication of a high density array of discrete single-axis inertial sensors and then folding the array into a 3D IMU configuration. The main contribution of this thesis is

invention and implementation of a double-sided fabrication process for foldable structures with flexible polymer hinges, integrated high-end MEMS inertial sensors, and integration of thru-wafer interconnects in the fabrication process. Dissimilar materials were explored for

fabrication of the "origami-like" structures, expanding our knowledge on the use of polymers and standard bulk and surface micro-machining tools for manufacturing of 3D MEMS devices. In addition, this work investigated two tactical-grade gyroscope designs for potential integration with the introduced fabrication process: Dynamically Amplified Gyroscope (DAG) and Toroidal Ring Gyroscope (TRG). We designed, modeled, and implemented the control electronics, and experimentally demonstrated the tactical-grade performance of the DAG and TRG gyroscopes. In this dissertation, for the first time, an IMU prototype with all sensors operational was reported, demonstrating feasibility of the Folded MEMS approach for implementation of a compact tactical-grade performance system.

This thesis also explored a MEMS IMU solution, utilizing a single multi-axis sensing element. We demonstrated a 3-axis roll-pitch-yaw gyroscope, a major building block of the miniaturized IMU. The mechanical structure of the gyroscope employed a single vibrational

element with a torsional drive mode and a multi-directional sense modes. Experimental characterization of the sensor showed that it is capable of measuring an angular rate around all three orthogonal axes simultaneously with a minimal cross talk between

axes of sensitivity and increased immunity to external vibrations.

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