Alexandra Efimovskaya

Dual Foucault Pendulum gyroscope

We report a new type of MEMS degenerate mode lumped mass gyroscope architecture. The Dual Foucault Pendulum (DFP) gyroscope consists of two dynamically equivalent, mechanically coupled proof masses, oscillating in anti-phase motion. This dual axis tuning fork behavior creates a dynamically balanced resonator with x-y symmetry in frequency and damping. Phase synchronization is established by mechanical coupling of the two proof masses, whereas quadrature suppression is achieved by four differential shuttle pairs placed in-between. Dual axis tuning fork behavior provides vibration immunity and anchor loss mitigation, resulting in a Q-factor over 300,000 on both modes at a center frequency of 3.2 kHz. Due to high-Q degenerate mode operation, open-loop performance of 0.003 °/√h ARW and 0.27 °/h in-run bias stability were experimentally demonstrated. We believe Dual Foucault Pendulum is the minimal realization of a dynamically balanced lumped mass degenerate mode gyroscope.

On ordering of fundamental wineglass modes in toroidal ring gyroscope

In this paper, we discuss the primary sources of frequency splits in degenerate mode Toroidal Ring Gyroscope (TRG) with isotropic concentric rings suspension. We show that operation in the n=3 “wineglass mode” might be preferable for prioritized device symmetry. We demonstrate that by means of structural design it is possible to achieve a desired order of wineglass modes, critical for vibration immunity, and potentially for improved performance of miniature devices. Mode-ordering is accomplished by a proper choice of a number of rings in the suspension and an angle between the spokes connecting the rings. The method of mode-ordering is confirmed through experimental characterization of 2.8 mm diameter TRG prototypes fabricated in <100> and <111> single crystal silicon.

Miniature origami-like folded MEMS TIMU

In this paper, we report implementation of a folded MEMS concept, demonstrating a prototype of Timing and Inertial Measurement Unit (TIMU) in <; 50 mm3 volume. The approach is based on assembling high aspect-ratio single-axis sensors into a 3-D configuration, or folding it into a 3-D prismatic shape, like a silicon origami. The fabrication process permits a significant reduction in size preserving functionality without compromising sensor performance. Fabricated TIMU prototypes feature 3 toroidal ring gyroscopes, 3 accelerometers, and a resonator, thus allowing for miniature self-contained 6-DOF inertial and timing system. Initial characterization confirmed the potential of folded MEMS approach for implementation of low-noise inertial sensors, demonstrating VRW of 0.078 m/s/√h and bias instability of <;0.2 mg for accelerometers, ARW of 0.78°/√h, and bias instability of <;17°/√h for gyroscopes.

Minimal realization of dynamically balanced lumped mass WA gyroscope: dual foucault pendulum

We report a new type of MEMS rate integrating gyroscope. The Dual Foucault Pendulum (DFP) gyroscope consists of two dynamically equivalent, mechanically coupled proof masses, oscillating in anti-phase motion, creating a dynamically balanced resonator with x-y symmetry in frequency and damping. Phase synchronization is established by mechanical coupling of the two proof masses, whereas quadrature suppression is achieved by four differential shuttle pairs placed in-between. Dual axis tuning fork behavior provides vibration immunity and anchor loss mitigation, resulting in a Qfactor over 100,000 on both modes at a center frequency of 2.7 kHz. Whole angle mechanization is demonstrated by FPGAbased closed loop control of the gyroscope, showing a scale factor variation of 22 ppm RMS over 2 hours of measurement. We believe Dual Foucault Pendulum is the minimal realization of a dynamically balanced lumped mass whole angle (WA) gyroscope.

Origami-like folded mems for realization of TIMU: fabrication technology and initial demonstration

This paper reports a prototype of miniature, <;50 mm3, Timing and Inertial Measurement Unit (TIMU), implemented utilizing a Folded MEMS concept. The approach is based on a wafer-level fabrication of high aspect ratio single-axis sensors, interconnected by flexible polyimide hinges, and then folded into a 3-D configuration, typically in a shape of cube or prism. Co-fabricated thru-wafer interconnects enable interfacing sensors on the device side of the TIMU with signal conditioning electronics potentially integrated inside a folded 3-D structure. We report a TIMU prototype with all 7 sensors operational, thus demonstrating a feasibility of the proposed fabrication approach. In this paper, we emphasize the characterization of the low-noise accelerometers, implemented on the TIMU sidewalls, demonstrating VRW of 0.057 m=s2= p h and bias instability of <;0.2 mg.

Origami-Like 3-D Folded MEMS Approach for Miniature Inertial Measurement Unit

This paper presents a miniature 50 mm3 inertial measurement unit (IMU) implemented using a folded microelectromechanical systems (MEMS) process. The approach is based on wafer-level fabrication of high aspect-ratio single-axis sensors interconnected by flexible hinges and folded into a 3-D configuration, like a silicon Origami [1]. Two different materials for flexible hinges have been explored, including photo-definable polyimide and parylene-C. We report, for the first time, an IMU prototype with seven operational sensors: three accelerometers, three gyroscopes, and a prototype of a reference clock. This paper concludes with the results of experimental characterization of inertial sensors demonstrating the feasibility of the proposed approach for a compact IMU. [2016-0267]

A comparative study of conventional single-mass and amplitude amplified dual-mass MEMS Vibratory Gyroscopes

This paper presents preliminary experimental results on a novel dual-mass MEMS gyroscope with mechanical amplification of amplitude. A side-by-side comparison between proposed dual-mass and conventional single-mass gyroscopes is presented and the effect of amplitude amplification on the scale factor and noise characteristics is discussed. The dual-mass gyroscope demonstrated a scale factor of 0.465 mV/(deg/s) in the open-loop rate-mode of operation, which is three times higher sensitivity than the single-mass gyroscope. The dual-mass gyroscope also showed a superior performance in bias stability and Angle Random Walk (ARW).

Thru-Wafer Interconnects for Double-Sided (TWIDS) fabrication of MEMS

This paper reports a new approach for fabrication of high-aspect ratio low resistance vertical interconnects, providing an electrical interface between the front-side and the backside of the Silicon-on-Insulator (SOI) wafer. The method of Thru-Wafer Interconnects for Double-Sided (TWIDS) fabrication of MEMS is based on seedless copper electroplating, and allows for voids free features and high aspect ratio (copper diameter to wafer thickness ratio is 10:1). We introduced the fabrication sequence, implemented and characterized prototypes of a MEMS toroidal ring gyroscope with thru-wafer interconnects, thus illustrating the process feasibility. Furthermore, the critical issue of mechanical stability in air-gap interconnect structures under 15,000 g shock was investigated using 3D Finite Element Analysis (FEA) models. Our simulations revealed that a partial filling the gaps with Parylene C allows for 1.55x improvement in mechanical stability without a significant increase in via parasitic capacitance values.

Double-Sided Process for MEMS SOI Sensors With Deep Vertical Thru-Wafer Interconnects

This paper reports an approach for co-fabrication of silicon-on-insulator (SOI) sensors with low-resistance vertical electrical interconnects in thick (up to

Compact roll-pitch-yaw gyroscope implemented in wafer-level Epitaxial Silicon Encapsulation process

600~\mu \text{m}