141 research outputs found
High performance 3-folded symmetric decoupled MEMS gyroscopes
This thesis reports, for the first time, on a novel design and architecture for realizing inertial grade gyroscope based on Micro-Electro-Mechanical Systems (MEMS) technology. The proposed device is suitable for high-precision Inertial Navigation Systems (INS). The new design has been investigated analytically and numerically by means of Finite Element Modeling (FEM) of the shapes, resonance frequencies and decoupling of the natural drive and sense modes of the various implementations. Also, famous phenomena known as spring softening and spring hardening are studied. Their effect on the gyroscope operation is modeled numerically in Matlab/Simulink platform. This latter model is used to predict the drive/sense mode matching capability of the proposed designs. Based on the comparison with the best recently reported performance towards inertial grade operation, it is expected that the novel architecture further lowers the dominant Brownian (thermo-mechanical) noise level by more than an order of magnitude (down to 0.08ĂÂș/hr). Moreover, the gyroscope\u27s figure of merit, such as output sensitivity (150 mV/ĂÂș/s), is expected to be improved by more than two orders of magnitude. This necessarily results in a signal to noise ratio (SNR) which is up to three orders of magnitude higher (up to 1,900mV/ ĂÂș/hr). Furthermore, the novel concept introduced in this work for building MEMS gyroscopes allows reducing the sense parasitic capacitance by up to an order of magnitude. This in turn reduces the drive mode coupling or quadrature errors in the sensor\u27s output signal. The new approach employs Silicon-on-Insulator (SOI) substrates that allows the realization of large mass (\u3e1.6mg), large sense capacitance (\u3e2.2pF), high quality factors (\u3e21,000), large drive amplitude (~2-4 ”m) and low resonance frequency (~3-4 KHz) as well as the consequently suppressed noise floor and reduced support losses for high-performance vacuum operation. Several challenges were encountered during fabrication that required developing high aspect ratio (up to 1:20) etching process for deep trenches (up to 500 ĂÆĂąâŹĆĄĂâĂ”m). Frequency Response measurement platform was built for devices characterization. The measurements were performed at atmospheric pressures causing huge drop of the devices performance. Therefore, various MEMS gyroscope packaging technologies are studied. Wafer Level Packaging (WLP) is selected to encapsulate the fabricated devices under vacuum by utilizing wafer bonding. Through Silicon Via (TSV) technology was developed (as connections) to transfer the electrical signals (of the fabricated devices) outside the cap wafers
Degree-per-hour mode-matched micromachined silicon vibratory gyroscopes
The objective of this research dissertation is to design and implement two novel micromachined silicon vibratory gyroscopes, which attempt to incorporate all the necessary attributes of sub-deg/hr noise performance requirements in a single framework: large resonant mass, high drive-mode oscillation amplitudes, large device capacitance (coupled with optimized electronics), and high-Q resonant mode-matched operation. Mode-matching leverages the high-Q (mechanical gain) of the operating modes of the gyroscope and offers significant improvements in mechanical and electronic noise floor, sensitivity, and bias stability. The first micromachined silicon vibratory gyroscope presented in this work is the resonating star gyroscope (RSG): a novel Class-II shell-type structure which utilizes degenerate flexural modes. After an iterative cycle of design optimization, an RSG prototype was implemented using a multiple-shell approach on (111) SOI substrate. Experimental data indicates sub-5 deg/hr Allan deviation bias instability operating under a mode-matched operating Q of 30,000 at 23ÂșC (in vacuum). The second micromachined silicon vibratory gyroscope presented in this work is the mode-matched tuning fork gyroscope (M2-TFG): a novel Class-I tuning fork structure which utilizes in-plane non-degenerate resonant flexural modes. Operated under vacuum, the M2-TFG represents the first reported high-Q perfectly mode-matched operation in Class-I vibratory microgyroscope. Experimental results of device implemented on (100) SOI substrate demonstrates sub-deg/hr Allan deviation bias instability operating under a mode-matched operating Q of 50,000 at 23ÂșC. In an effort to increase capacitive aspect ratio, a new fabrication technology was developed that involved the selective deposition of doped-polysilicon inside the capacitive sensing gaps (SPD Process). By preserving the structural composition integrity of the flexural springs, it is possible to accurately predict the operating-mode frequencies while maintaining high-Q operation. Preliminary characterization of vacuum-packaged prototypes was performed. Initial results demonstrated high-Q mode-matched operation, excellent thermal stability, and sub-deg/hr Allan variance bias instability.Ph.D.Committee Chair: Dr. Farrokh Ayazi; Committee Member: Dr. Mark G. Allen; Committee Member: Dr. Oliver Brand; Committee Member: Dr. Paul A. Kohl; Committee Member: Dr. Thomas E. Michael
MEMS Accelerometers
Micro-electro-mechanical system (MEMS) devices are widely used for inertia, pressure, and ultrasound sensing applications. Research on integrated MEMS technology has undergone extensive development driven by the requirements of a compact footprint, low cost, and increased functionality. Accelerometers are among the most widely used sensors implemented in MEMS technology. MEMS accelerometers are showing a growing presence in almost all industries ranging from automotive to medical. A traditional MEMS accelerometer employs a proof mass suspended to springs, which displaces in response to an external acceleration. A single proof mass can be used for one- or multi-axis sensing. A variety of transduction mechanisms have been used to detect the displacement. They include capacitive, piezoelectric, thermal, tunneling, and optical mechanisms. Capacitive accelerometers are widely used due to their DC measurement interface, thermal stability, reliability, and low cost. However, they are sensitive to electromagnetic field interferences and have poor performance for high-end applications (e.g., precise attitude control for the satellite). Over the past three decades, steady progress has been made in the area of optical accelerometers for high-performance and high-sensitivity applications but several challenges are still to be tackled by researchers and engineers to fully realize opto-mechanical accelerometers, such as chip-scale integration, scaling, low bandwidth, etc
Fabrication, Testing and Characterization of MEMS Gyroscope
This thesis presents the design, fabrication and characterization of two Micro-Electro-Mechanical Systems (MEMS) vibratory gyroscopes fabricated using the Silicon-On-Insulator-Multi-User-MEMS Process (SOIMUMPs) and Polysilicon Multi-User-MEMS-Process (Poly-MUMPs). Firstly, relevant literature and background on static and dynamic analysis of MEMS gyroscopes are described. Secondly, the gyroscope analytical model is presented and numerically solved using Mathematica software. The lumped mass model was used to analytically design the gyroscope and predict their performance. Finite element analysis was carried out on the gyroscopes to verify the proposed designs. Thirdly, gyroscope fabrication using MEMSCAP's SOIMUMPs and PolyMUMPs processes is described. For the former, post-processing was carried out at the Quantum Nanofab Center (QNC) on a die-level in order to create the vibratory structural elements (cantilever beam). Following this, the PolyMUMPs gyroscopes are characterized optically by measuring their resonance frequencies and quality factor using a Laser Doppler Vibrometer (LDV). The drive resonance frequency was measured at 40 kHz and the quality factor as Q = 1. For the sense mode, the resonance frequency was measured at 55 kHz and the unity quality factor as Q = 1. The characterization results show large drive direction motions of 100 um/s in response to a voltage pulse of 10 V. The drive pull-in voltage was measured at 19 V. Finally, the ratio of the measured drive to sense mode velocities in response to a voltage pulse of 10 V was calculated at 1.375
Rotation active sensors based on ultrafast fibre lasers
Gyroscopes merit an undeniable role in inertial navigation systems, geodesy and seismology. By employing the optical Sagnac effect, ring laser gyroscopes provide exceptionally accurate measurements of even ultraslow angular velocity with a resolution up to 10â11 rad/s. With the recent advancement of ultrafast fibre lasers and, particularly, enabling effective bidirectional generation, their applications have been expanded to the areas of dual-comb spectroscopy and gyroscopy. Exceptional compactness, maintenance-free operation and rather low cost make ultrafast fibre lasers attractive for sensing applications. Remarkably, laser gyroscope operation in the ultrashort pulse generation regime presents a promising approach for eliminating sensing limitations caused by the synchronisation of counter-propagating channels, the most critical of which is frequency lock-in. In this work, we overview the fundamentals of gyroscopic sensing and ultrafast fibre lasers to bridge the gap between tools development and their real-world applications. This article provides a historical outline, highlights the most recent advancements and discusses perspectives for the expanding field of ultrafast fibre laser gyroscopes. We acknowledge the bottlenecks and deficiencies of the presented ultrafast laser gyroscope concepts due to intrinsic physical effects or currently available measurement methodology. Finally, the current work outlines solutions for further ultrafast laser technology development to translate to future commercial gyroscopes
Enhancements of MEMS design flow for Automotive and Optoelectronic applications
In the latest years we have been witnesses of a very rapidly and amazing grown of MicroElectroMechanical systems (MEMS) which nowadays represent the outstanding state-of-the art in a wide variety of applications from automotive to commercial, biomedical and optical (MicroOptoElectroMechanicalSystems).
The increasing success of MEMS is found in their high miniaturization capability, thus allowing an easy integration with electronic circuits, their low manufacturing costs (that comes directly from low unit pricing and indirectly from cutting service and maintaining costs) and low power consumption.
With the always growing interest around MEMS devices the necessity arises for MEMS designers to define a MEMS design flow. Indeed it is widely accepted that in any complex engineering design process, a well defined and documented design flow or procedure is vital.
The top-level goal of a MEMS/MOEMS design flow is to enable complex engineering design in the shortest time and with the lowest number of fabrication iterations, preferably only one. These two characteristics are the measures of a good flow, because they translate directly to the industry-desirable reductions of the metrics âtime to marketâ and âcostsâ.
Like most engineering flows, the MEMS design flow begins with the product definition that generally involves a feasibility study and the elaboration of the device specifications. Once the MEMS specifications are set, a Finite Element Method (FEM) model is developed in order to study its physical behaviour and to extract the characteristic device parameters. These latter are used to develop a high level MEMS model which is necessary to the design of the sensor read out electronics. Once the MEMS geometry is completely defined and matches the device specifications, the device layout must be generated, and finally the MEMS sensor is fabricated.
In order to have a MEMS sensor working according to specifications at first production run is essential that the MEMS design flow is as close as possible to the optimum design flow.
The key factors in the MEMS design flow are the development of a sensor model as close as possible to the real device and the layout realization. This research work addresses these two aspects by developing optimized custom tools (a tool for layout check (LVS) and a tool for parasitic capacitances extraction) and new methodologies (a methodology for post layout simulations) which support the designer during the crucial steps of the design process as well as by presenting the models of two cases studies belonging to leading MEMS applications (a micromirror for laser projection system and a control loop for the shock immunity enhancement in gyroscopes for automotive applications)
Fixed-wing MAV attitude stability in atmospheric turbulence, part 1: Suitability of conventional sensors
Fixed-wing Micro-Aerial Vehicles (MAVs) need effective sensors that can rapidly detect turbulence induced motion perturbations. Current MAV attitude control systems rely on inertial sensors. These systems can be described as reactive; detecting the disturbance only after the aircraft has responded to the disturbing phenomena. In this part of the paper, the current state of the art in reactive attitude sensing for fixed-wing MAVs are reviewed. A scheme for classifying the range of existing and emerging sensing techniques is presented. The features and performance of the sensing approaches are discussed in the context of their application to MAV attitude control systems in turbulent environments. It is found that the use of single sensors is insufficient for MAV control in the presence of turbulence and that potential gains can be realised from multi-sensor systems. A successive paper to be published in this journal will investigate novel attitude sensors which have the potential to improve attitude control of MAVs in Turbulenc
A Review on Key Issues and Challenges in Devices Level MEMS Testing
The present review provides information relevant to issues and challenges in MEMS testing techniques that are implemented to analyze the microelectromechanical systems (MEMS) behavior for specific application and operating conditions. MEMS devices are more complex and extremely diverse due to the immersion of multidomains. Their failure modes are distinctive under different circumstances. Therefore, testing of these systems at device level as well as at mass production level, that is, parallel testing, is becoming very challenging as compared to the IC test, because MEMS respond to electrical, physical, chemical, and optical stimuli. Currently, test systems developed for MEMS devices have to be customized due to their nondeterministic behavior and complexity. The accurate measurement of test systems for MEMS is difficult to quantify in the production phase. The complexity of the device to be tested required maturity in the test technique which increases the cost of test development; this practice is directly imposed on the device cost. This factor causes a delay in time-to-market
A Review on Key Issues and Challenges in Devices Level MEMS Testing
The present review provides information relevant to issues and challenges in MEMS testing techniques that are implemented to analyze the microelectromechanical systems (MEMS) behavior for specific application and operating conditions. MEMS devices are more complex and extremely diverse due to the immersion of multidomains. Their failure modes are distinctive under different circumstances. Therefore, testing of these systems at device level as well as at mass production level, that is, parallel testing, is becoming very challenging as compared to the IC test, because MEMS respond to electrical, physical, chemical, and optical stimuli. Currently, test systems developed for MEMS devices have to be customized due to their nondeterministic behavior and complexity. The accurate measurement of test systems for MEMS is difficult to quantify in the production phase. The complexity of the device to be tested required maturity in the test technique which increases the cost of test development; this practice is directly imposed on the device cost. This factor causes a delay in time-to-market
Quantum Communication, Sensing and Measurement in Space
The main theme of the conclusions drawn for classical communication systems
operating at optical or higher frequencies is that there is a wellâunderstood
performance gain in photon efficiency (bits/photon) and spectral efficiency
(bits/s/Hz) by pursuing coherentâstate transmitters (classical ideal laser light)
coupled with novel quantum receiver systems operating near the Holevo limit (e.g.,
joint detection receivers). However, recent research indicates that these receivers
will require nonlinear and nonclassical optical processes and components at the
receiver. Consequently, the implementation complexity of Holevoâcapacityapproaching
receivers is not yet fully ascertained. Nonetheless, because the
potential gain is significant (e.g., the projected photon efficiency and data rate of
MIT Lincoln Laboratory's Lunar Lasercom Demonstration (LLCD) could be achieved
with a factorâofâ20 reduction in the modulation bandwidth requirement), focused
research activities on groundâreceiver architectures that approach the Holevo limit
in spaceâcommunication links would be beneficial.
The potential gains resulting from quantumâenhanced sensing systems in space
applications have not been laid out as concretely as some of the other areas
addressed in our study. In particular, while the study period has produced several
interesting highârisk and highâpayoff avenues of research, more detailed seedlinglevel
investigations are required to fully delineate the potential return relative to
the stateâofâtheâart. Two prominent examples are (1) improvements to pointing,
acquisition and tracking systems (e.g., for optical communication systems) by way
of quantum measurements, and (2) possible weakâvalued measurement techniques
to attain highâaccuracy sensing systems for in situ or remoteâsensing instruments.
While these concepts are technically sound and have very promising benchâtop
demonstrations in a lab environment, they are not mature enough to realistically
evaluate their performance in a spaceâbased application. Therefore, it is
recommended that future work follow small focused efforts towards incorporating
practical constraints imposed by a space environment.
The space platform has been well recognized as a nearly ideal environment for some
of the most precise tests of fundamental physics, and the ensuing potential of
scientific advances enabled by quantum technologies is evident in our report. For
example, an exciting concept that has emerged for gravityâwave detection is that the
intermediate frequency band spanning 0.01 to 10 Hzâwhich is inaccessible from
the groundâcould be accessed at unprecedented sensitivity with a spaceâbased
interferometer that uses shorter arms relative to stateâofâtheâart to keep the
diffraction losses low, and employs frequencyâdependent squeezed light to surpass
the standard quantum limit sensitivity. This offers the potential to open up a new
window into the universe, revealing the behavior of compact astrophysical objects
and pulsars. As another set of examples, research accomplishments in the atomic
and optics fields in recent years have ushered in a number of novel clocks and
sensors that can achieve unprecedented measurement precisions. These emerging
technologies promise new possibilities in fundamental physics, examples of which
are tests of relativistic gravity theory, universality of free fall, frameâdragging
precession, the gravitational inverseâsquare law at micron scale, and new ways of gravitational wave detection with atomic inertial sensors. While the relevant
technologies and their discovery potentials have been well demonstrated on the
ground, there exists a large gap to spaceâbased systems. To bridge this gap and to
advance fundamentalâphysics exploration in space, focused investments that further
mature promising technologies, such as spaceâbased atomic clocks and quantum
sensors based on atomâwave interferometers, are recommended.
Bringing a group of experts from diverse technical backgrounds together in a
productive interactive environment spurred some unanticipated innovative
concepts. One promising concept is the possibility of utilizing a spaceâbased
interferometer as a frequency reference for terrestrial precision measurements.
Spaceâbased gravitational wave detectors depend on extraordinarily low noise in
the separation between spacecraft, resulting in an ultraâstable frequency reference
that is several orders of magnitude better than the state of the art of frequency
references using terrestrial technology. The next steps in developing this promising
new concept are simulations and measurement of atmospheric effects that may limit
performance due to nonâreciprocal phase fluctuations.
In summary, this report covers a broad spectrum of possible new opportunities in
space science, as well as enhancements in the performance of communication and
sensing technologies, based on observing, manipulating and exploiting the
quantumâmechanical nature of our universe. In our study we identified a range of
exciting new opportunities to capture the revolutionary capabilities resulting from
quantum enhancements. We believe that pursuing these opportunities has the
potential to positively impact the NASA mission in both the near term and in the
long term. In this report we lay out the research and development paths that we
believe are necessary to realize these opportunities and capitalize on the gains
quantum technologies can offer
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