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Micro-glassblowing Paradigm for Realization of Rate Integrating Gyroscopes

  • Author(s): Senkal, Doruk
  • Advisor(s): Shkel, Andrei M
  • et al.
Abstract

This Ph.D. dissertation reports novel fabrication processes and architectures for implementation of Rate Integrating Gyroscopes at micro-scale. Majority of the focus is directed towards development of a surface tension and pressure driven micro-glassblowing paradigm, which is envisioned to serve as an enabling mechanism for wafer-scale fabrication of 3-D micro-wineglass gyroscopes. New 2-D silicon Micro Rate Integrating Gyroscope (MRIG) architectures are also explored to bridge the gap between conventional micro-machining techniques and micro-glassblowing processes, and to serve as a test platform for various MRIG control strategies. Closed loop Whole Angle operation of these 2-D silicon MRIG architectures is presented to identify some of the control challenges associated with MRIG control, such as energy pumping and suppression of errors caused by structural imperfections.

The main contribution of the thesis is the development of a high temperature (1700 °C) micro-glassblowing process for fabrication of highly symmetric and low internal dissipation 3-D fused silica wineglass resonators. Owing to the "self-healing'" properties of surface tension and pressure driven micro-glassblowing paradigm, and the low internal loss fused silica material, quality factors above 1 million and frequency splits less than 1 Hz have been demonstrated. In addition to a multi-purpose test-bed for micro-wineglass characterization, in-situ electrode structures with sub 10 micron capacitive gaps are reported for electrostatic transduction.

In order to streamline the realization of MRIG control strategies, two new Si-MEMS MRIG architectures were also developed as a part of this thesis: Toroidal Ring Gyroscope (TRG) and Dual Foucault Pendulum (DFP) Gyroscope. Toroidal Ring Gyroscope consists of an outer anchor, concentric ring suspension system, and inner electrode assembly. Q-factors above 100,000 were obtained with this architecture at a compact size of 1760 micron. First demonstration of a parametrically driven MRIG is also reported as a part of this work, showing better than 20 ppm scale factor stability at 360 °/s rate input. Dual Foucault Pendulum (DFP) architecture is a conventionally machined lumped mass Micro Rate Integrating Gyroscope implemented using in-house silicon-on-insulator technology. It is believed that this two mass DFP architecture is the minimal realization of a dynamically balanced, lumped mass MRIG.

Finally, a custom, multi-purpose FPGA/DSP based control system was developed to demonstrate interchangeable rate and rate integrating mechanization of micro-scale gyroscope architectures developed in this thesis. Continuous Rate Integrating Gyroscope operation is demonstrated, by electronically compensating structural imperfections via control loops, such as Phase Locked Loop (PLL), Amplitude Gain Control (AGC), quadrature null loop, and closed-loop parametric drive.

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