University of California

Other

Government of the United States of America, As Represented by the Secretary of Commerce

Parvenu, Inc.

Solus Micro Technologies, Inc.

Andrei M Shkel

Alexander A Trusov

Cenk Acar

Adam Schofield

Sergei A Zotov

Doruk Senkal

Erik Jesper Eklund

Yusheng Wang

Igor P Prikhodko

Michael J Little

Christopher C Painter

Mohammad H Asadian Ardakani

Brenton R Simon

Roger T Howe

Asad M Madni

John Kitching

Lynn Edward Costlow

Elizabeth Ann Donley

Sergey A Zotov

Montgomery C Rivers

Eleanor Hodby

E Jesper Eklund

Mohammed Ahamed

Chris Painter

A dual-shell architecture and methods of fabrication of fused quartz resonators is disclosed. The architecture may include two encapsulated and concentric cavities using plasma-activated wafer bonding followed by the high-temperature glassblowing. The dual-shell architecture can provide a protective shield as well as a 'fixed-fixed' anchor for the sensing element of the resonators. Structures can be instrumented to operate as a resonator, a gyroscope, or other vibratory sensor and for precision operation in a harsh environment. Methods for fabricating a dual-shell resonator structure can include pre-etching cavities on a cap wafer, pre-etching cavities on a device wafer, bonding the device wafer to a substrate wafer to form a substrate pair and aligning and bonding the cap wafer to the substrate pair to form a wafer stack with aligned cavities including a cap cavity and a device cavity. The wafer stack may be glassblown to form a dual-shell structure.

Fused quartz dual shell resonator and method of fabrication

Processes and systems for adaptive pedestrian inertial navigation are provided. Configurations can adjust to various navigation scenarios, including different floor types and different gait paces. A combination of IMU data partition, principal component analysis (PCA), and artificial neural network may be used to perform the floor type detection. Floor type results may be used in the multiple-model extended Kalman filter. In each extended Kalman filter, an adaptive threshold is used for the stance phase detection to enable the detector to adjust to gait frequency without tuning design parameters during navigation. A floor type classification of high accuracy is demonstrated, and the position error in a velocity-changing navigation system using adaptive threshold is reduced.

Methods and systems for adaptive pedestrian inertial navigation

The improvement includes an outer proof mass having a corresponding center of mass; and an inner proof mass having a corresponding center of mass, where the corresponding centers of mass of the outer proof mass and the inner proof mass are approximately co-located. Thus, a double Foucault pendulum is essentially provided in a micromachined gyroscope.

Fully balanced micro-machined inertial sensor

A toroidal ring gyroscope with a robust outer perimeter anchor and a distributed suspension system. The vibrational energy in the design is concentrated towards the innermost ring, and the device is anchored at the outer perimeter. The distributed support structure prevents vibrational motion propagating to the outer anchor, which helps trap the vibrational energy within the gyroscope and provides a Q-factor of &#x3e;100,000 at a compact size of 1760 &#x3bc;m. Due to the parametric pumping effect, energy added to each mode is proportional to the existing amplitude of the respective mode. As a result, errors associated with finding the orientation of the standing wave and x-y drive gain drift are bypassed. The toroidal ring gyroscope can be fabricated using any standard silicon on insulator process. Due to the high Q-factor and robust support structure, the device can potentially be instrumented in high-g environments that require high angular rate sensitivity.

Axi-symmetric small-footprint gyroscope with interchangeable whole-angle and rate operation

A method for self-compensation of the bias draft of the quadrature signal of a gyroscope. The method is a combination of a variety of sub-methods, which can include quadrature compensation, can be used to achieve the highest possible stability. The calibration methods include a temperature self-sensing algorithm utilizing the drive-mode resonance frequency for calibration of thermal drift in the mechanical parameters of the system, a sideband-ratio approach for direct detection of mechanical drive-mode amplitude, modifying the AC and DC components of the amplitude gain control (AGC) for improved stability, and an approach for compensation of thermal drift in the sense-mode pick off system by utilizing mechanical quadrature. By using some or all of the four methods of calibration above, the highest level of long term in-run bias stability can be achieved.

Utilization of mechanical quadrature in silicon MEMS vibratory gyroscope to increase and expand the long term in-run bias stability

A method of making a Coriolis vibratory gyroscope with a three dimensional mushroom resonator element includes defining a cavity in a substrate wafer; bonding a cap wafer onto the substrate over the cavity from which cap wafer the resonator element will be formed; heating the substrate and cap wafer to generate a pressure build-up within the cavity; plastically deforming the cap wafer by the pressure build-up to form the mushroom resonator element having a perimeter around the mushroom resonator element; releasing the three dimensional mushroom resonator element at the perimeter by selectively removing material so that the perimeter of mushroom resonator element is free to vibrate; and disposing a layer of conductive material on the mushroom resonator element to form electrodes thereon for use in driving and sensing vibrations of the mushroom resonator element and its perimeter. A microgyroscope made by such a method is also included within the embodiments.

Method of fabricating micro-glassblown gyroscopes

A multi-axis microelectromechanical-systems (MEMS) inertial measurement unit (IMU) is fabricated in a vacuum sealed single packaged device. An FM vibratory gyroscope and an FM resonant accelerometer both for generating FM output signals is fabricated in the silicon chip using MEMS. A signal processor is coupled to the an FM vibratory gyroscope and to the FM resonant accelerometer for receiving the FM gyroscopic output signals and the FM accelerometer output signals. The signal processor generates simultaneous and decoupled measurement of input acceleration, input rotation rate, and temperature and/or temperature distribution within the IMU, self-calibration of the biases and scale factors of the IMU and its support electronics against temperature variations and other common mode errors, and reduction of the cross axis sensitivity by reducing acceleration errors in the gyroscope and rotation errors in the accelerometer.

Multi-axis chip-scale MEMS inertial measurement unit (IMU) based on frequency modulation

A method for fabricating an environmentally robust micro-wineglass gyroscope includes the steps of stacking and bonding of at least an inner glass layer and an outer glass layer to a substrate wafer; plastically deforming the inner glass layer into a mushroom-shaped structure and deforming the outer glass layer into a shield capable of extending over the inner glass layer, while leaving the inner and outer glass layers connectable at a central post location; removing the substrate layer and a portion of the inner glass layer so that a perimeter of the inner glass layer is free; and bonding the deformed inner and outer glass layers to a handle wafer. The resulting structure is an environmentally robust micro-wineglass gyroscope which has a double ended supported central post location for the mushroom-shaped structure of the inner glass layer.

Environmentally robust micro-wineglass gyroscope

A z-axis gyroscope design is presented with a 2-degree of freedom (DOF) sense mode allowing interchangeable operation in either precision (mode-matched) or robust (wide-bandwidth) modes. This is accomplished using a complete 2-DOF coupled system which allows for the specification of the sense mode resonant frequencies and coupling independent of frequency. By decoupling the frame connecting the sense system to a central anchor, x-y symmetry is preserved while enabling a fully coupled 2-DOF sense mode providing control over both the bandwidth and the amount of coupling independent of operational frequency. The robust mode corresponds to operation between the 2-DOF sense mode resonant frequencies providing a response gain and bandwidth controlled by frequency spacing. Precision mode of operation, however, relies on mode-matching the drive to the second, anti-phase sense mode resonant frequency which can be designed to provide a gain advantage over a similar 1-DOF system.

Micromachined gyroscopes with 2-DOF sense modes allowing interchangeable robust and precision operation

A vibratory sensor is fabricated as a three-dimensional batch-micromachined shell adapted to vibrate and support elastic wave propagation and wave precession in the shell or membrane and at least one driving electrode and preferably a plurality of driving electrodes directly or indirectly coupled to the shell to excite and sustain the elastic waves in the shell. The pattern of elastic waves is determined by the configuration of the driving electrode(s). At least one sensing electrode and preferably a plurality of sensing electrodes are provided to detect the precession of the elastic wave pattern in the shell. The rotation of the shell induces precession of the elastic wave pattern in the shell which is usable to measure the rotation angle or rate of the vibratory sensor.

Method for batch fabrication of three-dimensional shells

A MEMS resonator includes two resonating masses having an anti-phase and in-phase resonance mode, each mode having a resonance frequency, and an anti-phase resonance levering system coupled to the two resonating masses to stiffen and/or dampen the in-phase resonance mode while leaving the anti-phase resonance mode compliant. This effectively raises the in-phase resonance frequency above the anti-phase resonance frequency, and potentially creates a large frequency separation between the two resonance modes. This reduces the energy transfer between the two modes, allowing for robustness to external acceleration, because the in-phase mode is of a higher frequency. The anti-phase resonance levering system is disposed between the two resonating masses as an internal levering mechanism, or is disposed around the two resonating masses as an external levering mechanism.

Lever mechanisms for anti-phase mode isolation in MEMS tuning-fork structures

A high temperature micro-glassblowing process and a novel inverted-wineglass architecture that provides self-aligned stem structures. The fabrication process involves the etching of a fused quartz substrate wafer. A TSG or fused quartz device layer is then bonded onto the fused quartz substrate, creating a trapped air pocket or cavity between the substrate and the TSG device layer. The substrate and TSG device layerare then heated at an extremely high temperature of approximately 1700&#xb0; C., forming an inverted wineglass structure. Finally, the glassblown structure is cut or etched from the substrate to create a three dimensional wineglass resonator micro-device. The inverted wineglass structure may be used as a high performance resonator for use as a key element in precision clock resonators, dynamic MEMS sensors, and MEMS inertial sensors.

Microfabrication of high quality three dimensional structures using wafer-level glassblowing of fused quartz and ultra low expansion glasses

A digital angular rate sensor system based on frequency modulation (FM) of the rotation rate. The new approach relies on tracking of the resonant frequencies of two high-Q mechanical modes of vibration in a MEMS vibratory gyroscope to produce an inherently digital measurement of the input angular rate. The disclosed system is enabled by a combination of a MEMS vibratory high-Q gyroscope and a new signal processing scheme which takes advantage of a previously ignored gyroscope dynamics effect. The FM nature of the system eliminates noise versus bandwidth and resolution versus dynamic range tradeoffs of conventional vibratory rate gyroscopes. The FM approach allows achieving superior signal-to-noise-ratio through the use of ultra-high Q (1 million) mechanical structure without limiting the measurement bandwidth. Stability of 1e-9 can be achieved in the FM system, providing a 1000 times improvement over the state-of-the-art conventional AM gyroscopes with capacitive pick-off.

Growing community of inventors

Irvine, CA, United States of America

Andrei M Shkel