详解MEMS振动陀螺仪.pdf

所需积分/C币:29 2019-07-23 19:17:00 13.68MB .PDF

微电子系统(MEMS)技术以微观尺度融合电气和机械系统,彻底改变了惯性传感器。自1991年Draper实验室首次对微机械陀螺仪进行演示以来,已经有了在表面微机械加工微机械加工,混合表面 - 体粒加工技术或替代制造技术中制造的各种微机械陀螺仪设计。受到同一时代微机械加速度计取得巨大成功的启发,广泛研究商用微机械陀螺的研究工作引领了一些创新的陀螺仪拓扑,制造和集成方法以及检测技术。因此,在各种基于微机械加工的批量制造工艺中,已经有效地实施并演示了利用振动元件进行试验并检测科里奥利力的振动微机械陀螺仪。然而,实现制造变化和环境波动的可能性仍然是微机械振动速率陀螺仪商业化和大批量生产中最大的挑战之一。
② Springer To my beloved wife sebnem acar, and my dear parents Preface Merging electrical and mechanical systems at a micro scale, Microelectromechani cal Systems(MEMS)technology has revolutionized inertial sensors. Since the first demonstration of a micromachined gyroscope by the Draper Laboratory in 1991 various micromachined gyroscope designs fabricated in surface micromachining, bulk micromachining, hybrid surface-bulk micromachining technologies or alterna- tive fabrication techniques have been reported Inspired by the promising success of micromachined accelerometers in the same era. extensive research efforts to wards commercial micromachined gyroscopes led to several innovative gyroscope topologies, fabrication and integration approaches, and detection techniques. Con sequently, vibratory micromachined gyroscopes that utilize vibrating elements to in- duce and detect Coriolis force have been effectively implemented and demonstrated in various micromachining-based batch fabrication processes. However, achieving robustness against fabrication variations and environmental fluctuations still re mains as one of the greatest challenges in commercialization and high-volume pro duction of micromachined vibratory rate gyroscopes The limitations of the photolithography-based micromachining technologies de fine the upper-bound on the performance and robustness of micromachined gyro scopes. Conventional gyroscope designs based on matching or near-matching the drive and sense mode resonant frequencies are quite sensitive to variations in oscil atory system parameters. Thus, producing stable and reliable vibratory microm chined gyroscopes have proven to be extremely challenging, primarily due to the high sensitivity of the dynamical system response to fabrication and environmental variations In the first part of this book, we review the Coriolis effect and angular rate sensors, and fundamental operational principles of micromachined vibratory gy roscopes We review basic mechanical and electrical design and implementation practices, system-level architectures, and common fabrication methods utilized for MEMS gyroscopes and inertial sensors in general. We also discuss electrical and mechanical parasitic effects such as structural imperfections, and analyze their im- pact on the sensing element dynamics Preface In the second part, we review recent results of the study on design concepts that explore the possibility of shifting the complexity from the control electronics to the structural design of the gyroscope dynamical system. The fundamental approach is to develop structural designs and dynamical systems for micromachined gyro- scopes that provide inherent robustness against structural and environmental param eter variations. In this context, we primarily focus on obtaining a gain and phase stable region in the drive and sense-mode frequency responses in order to achieve overall system robustness. Operating in the stable drive and sense frequency regions provides improved bias stability, temperature stability, and immunity to environ- mental and fabrication variations. Toward this goal, two major design concepts are investigated: expanding the dynamic system design space by increasing the degree- of-freedom of the drive and sense mode oscillatory system, and utilizing an array of drive-mode oscillators with incrementally spaced resonant frequencies This book provides a solid foundation in the fundamental theory, design and im plementation of micromachined vibratory rate gyroscopes, and introduces a new paradigm in MEMs gyroscope sensing element design, where disturbance-rejection capability is achieved by the mechanical system instead of active control and com pensation strategies. The micromachined gyroscopes of this class are expected to lead to reliable, robust and high performance angular-rate sensors with low pro duction costs and high yields, fitting into or enabling many applications in the aerospace/defense automotive and consumer electronics markets June 2008 Cenk Acar: Andrei shkel ontents Part I Fundamentals of Micromachined Vibratory gyroscopes 1 ntroduction 1.1 The Coriolis effect 1. 2 Gyrosc 4 1. 3 The MEMS Technology 1. 4 Micromachined Vibratory Rate gyroscopes 1.5 Applications of MEMS G 8 1.6 Gyroscope performance specifications 8 1.7 A Survey of Prior Work on MEMS Gyroscopes 10 1. 8 The robustness Challenge.. ..14 1.9 Inherently robust Systems 15 1. 10 Overview 16 2 Fundamentals of Micromachined gyroscopes 2.1 Dynamics of Vibratory Rate Gyroscopes 17 2.1.1 Linear gyroscope dynamics 17 2.1.2 Torsional gyroscope dynamics 2.2 Resonance Characteristics 25 2.3 Drive-Mode operation 28 2. 4 The Coriolis response 2. 4.1 Mode-Matching and 4 f 32 2. 4. 2 Phase Relations and Proof-Mass Trajectory 36 2.5 Summary 42 3 Fabrication Technologies 3.1 Microfabrication Techniques. .............. 3.1.1 Photolithography 44 3.1.2 Deposition .46 3.1.3 Etching 48 3.1.4 Wafer Bonding Contents 3.2 Bulk Micromachining processes 52 3.2.1 SOI-Based Bulk micromachining 3.2.2 Silicon-on-Glass Bulk micromachining 56 3.3 Surface-Micromachining Processes 3.4 Combined Surface-Bulk Micromachining 6 3.5 CMOS Integration 3.5.1 Hybrid Integration 64 3.5.2 Monolithic Integration..∴..… 65 3.6 Packaging 67 3.6.1 Wafer-Level Packaging ......68 3.6.2 Vacuum Packaging 3.7 Summary 4 Mechanical Design of MEMS Gyroscopes 73 4.1 Mechanical Structure Designs .73 4.2 Linear Vibratory Systems 74 4.2.1 Linear Suspension Systems 4.2.2 Linear flexure elements 83 4.3 Torsional vibratory systems 4.3.1 Torsional Suspension Systems 88 4.3.2 Torsional Flexure Elements 4.4 Anisoelasticity and Quadrature Error 93 4.4.1 Quadrature Compensation 100 4.5 Damping 4.5.1Ⅴ iscous dai 10 4.5.2 Viscous Anisodampin 104 4.5.3 Intrinsic Structural Damping .....105 4.6 Material Properties of Silicon .107 4.7 Design for Robustness 108 4.7.1 Yield 4.7.2 Vibration Immunity 4.7.3 Shock resistance 4.7.4 Temperature effects 109 4. 8 Summ 5 Electrical Design of MEMS Gyroscopes 5.2 Basics of Capacitive electrodes 5.3 Electrostatic Actuation 5.3.1 Variable-Gap Actuators 113 5.3.2 Variable-Area actuators 114 5.3.3 Balanced Actuation 116 5. 4 Capacitive detection 117 5. 4.1 Variable-Gap Capacitors 117 5.4.2 Variable-Area Capacitors 118

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