High-Performance Micromachined Vibratory Rate- and Rate-Integrating Gyroscopes.

We aim to reduce vibration sensitivity by developing gyros that operate in the balanced mode. The balanced mode creates zero net momentum and reduces energy loss through an anchor. The gyro can differentially cancel measurement errors from external vibration along both sensor axes. The vibration sensitivity of the balanced-mode gyroscope including structural imbalance from microfabrication reduces as the absolute difference between in-phase parasitic mode and operating mode frequencies increases. The parasitic sensing mode frequency is designed larger than the operating mode frequency to achieve both improved vibration insensitivity and shock resistivity. A single anchor is used to minimize thermoresidual stress change. We developed two gyroscope based on these design principles. The Balanced Oscillating Gyro (BOG) is a quad-mass tuning-fork rate gyroscope. The relationship between gyro design and modal characteristics is studied extensively using finite element method (FEM). The gyro is fabricated using the planar Si-on-glass (SOG) process with a device thickness of 100 micrometers. The BOG is evaluated using the first-generation analog interface circuitry. Under a frequency mismatch of 5Hz between driving and sense modes, the angle random walk (ARW) is measured to be 0.44deg/sec/sqrt(Hz). The Cylindrical Rate-Integrating Gyroscope (CING) operates in whole-angle mode. The gyro is completely axisymmetric and self-aligned to maximize mechanical isotropy. The gyro offers a large frequency ratio of ~1.7 between parasitic and the wineglass modes. The CING is fabricated using the 3D Si-on-glass (SOG) process with a device thickness of 300 micrometers. The 1st and 2nd generation CINGs operate at 18kHz and 3kHz, respectively and demonstrate a frequency mismatch of <1% and a large Q (~20,000 at 18kHz and ~100,000 at 3kHz under exact mode matching). In the rate-sensing mode, the first-generation CING (18kHz) demonstrates an Ag of 0.05, an angle random walk (ARW) of 7deg/sqrt(hr), and a bias stability of 72deg/hr without temperature compensation. In the rate-sensing mode, the second-generation CING measures an Ag of 0.0065, an ARW of 0.09deg/sqrt(hr), and a bias stability of 129deg/hr without temperature compensation. In the rate-integration mode, the second-generation CING demonstrates precession with an Ag of 0.011±0.001 under a frequency mismatch of 20~80mHz during several hours of operation.Ph.D.Electrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/91440/1/jycho_1.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/91440/2/jycho_2.pd

Navigation Using Inertial Sensors

This tutorial provides an introduction to navigation using inertial sensors, explaining the underlying principles. Topics covered include accelerometer and gyro technology and their characteristics, strapdown inertial navigation, attitude determination, integration and alignment, zero updates, motion constraints, pedestrian dead reckoning using step detection, and fault detection

Characterization of errors and noises in MEMS inertial sensors using Allan variance method

This thesis work has addressed the problems of characterizing and identifying the noises inherent to inertial sensors as gyros and accelerometers, which are embedded in inertial navigation systems, with the purpose of estimating the errors on the obtained position. The analysis of the Allan Variance method (AVAR) to characterize and identify the noises related to these sensors, has been done. The practical implementation of the AVAR method for the noises characterization has been performed over an experimental setup using the IMU 3DM-GX3 -25 data and the Matlab environment. From the AVAR plots it was possible to identify the Angle Random Walk and the Bias Instability in the gyros, and the Velocity Random Walk and Bias Instability in the accelerometers. A denoising process was also performed by using the Discrete Wavelet Transforms and the Median Filter. After the filtering the AVAR plots showed that the ARW was almost removed or attenuated using Wavelets, but not good results were obtained with the Median Filter

Gyrodampers for large space structures

The problem of controlling the vibrations of a large space structures by the use of actively augmented damping devices distributed throughout the structure is addressed. The gyrodamper which consists of a set of single gimbal control moment gyros which are actively controlled to extract the structural vibratory energy through the local rotational deformations of the structure, is described and analyzed. Various linear and nonlinear dynamic simulations of gyrodamped beams are shown, including results on self-induced vibrations due to sensor noise and rotor imbalance. The complete nonlinear dynamic equations are included. The problem of designing and sizing a system of gyrodampers for a given structure, or extrapolating results for one gyrodamped structure to another is solved in terms of scaling laws. Novel scaling laws for gyro systems are derived, based upon fundamental physical principles, and various examples are given

Isolated resonator gyroscope with a drive and sense plate

The present invention discloses a resonator gyroscope comprising a vibrationally isolated resonator including a proof mass, a counterbalancing plate having an extensive planar region, and one or more flexures interconnecting the proof mass and counterbalancing plate. A baseplate is affixed to the resonator by the one or more flexures and sense and drive electrodes are affixed to the baseplate proximate to the extensive planar region of the counterbalancing plate for exciting the resonator and sensing movement of the gyroscope. The isolated resonator transfers substantially no net momentum to the baseplate when the resonator is excited

CMOS systems and circuits for sub-degree per hour MEMS gyroscopes

The objective of our research is to develop system architectures and CMOS circuits that interface with high-Q silicon microgyroscopes to implement navigation-grade angular rate sensors. The MEMS sensor used in this work is an in-plane bulk-micromachined mode-matched tuning fork gyroscope (M² – TFG ), fabricated on silicon-on-insulator substrate. The use of CMOS transimpedance amplifiers (TIA) as front-ends in high-Q MEMS resonant sensors is explored. A T-network TIA is proposed as the front-end for resonant capacitive detection. The T-TIA provides on-chip transimpedance gains of 25MΩ, has a measured capacitive resolution of 0.02aF /√Hz at 15kHz, a dynamic range of 104dB in a bandwidth of 10Hz and consumes 400μW of power. A second contribution is the development of an automated scheme to adaptively bias the mechanical structure, such that the sensor is operated in the mode-matched condition. Mode-matching leverages the inherently high quality factors of the microgyroscope, resulting in significant improvement in the Brownian noise floor, electronic noise, sensitivity and bias drift of the microsensor. We developed a novel architecture that utilizes the often ignored residual quadrature error in a gyroscope to achieve and maintain perfect mode-matching (i.e.0Hz split between the drive and sense mode frequencies), as well as electronically control the sensor bandwidth. A CMOS implementation is developed that allows mode-matching of the drive and sense frequencies of a gyroscope at a fraction of the time taken by current state of-the-art techniques. Further, this mode-matching technique allows for maintaining a controlled separation between the drive and sense resonant frequencies, providing a means of increasing sensor bandwidth and dynamic range. The mode-matching CMOS IC, implemented in a 0.5μm 2P3M process, and control algorithm have been interfaced with a 60μm thick M2−TFG to implement an angular rate sensor with bias drift as low as 0.1°/hr ℃ the lowest recorded to date for a silicon MEMS gyro.Ph.D.Committee Chair: Farrokh Ayazi; Committee Member: Jennifer Michaels; Committee Member: Levent Degertekin; Committee Member: Paul Hasler; Committee Member: W. Marshall Leac

Characterization of MEMS Coriolis Vibratory Gyroscopes

A MEMS Gyroscope is a micromachined inertial sensor that can measure the angle of orientation or the angular rate of rotation. These devices have the potential to be used in high precision navigation, safety and consumer electronics applications. Due to their complexity, MEMS Gyroscopes are prone to have imperfections that inhibit their full potential. By deeply characterizing these sensors, it is possible to validate fabrication methodologies, apply control circuit mechanisms, and design alternative mechanical structures that improve the performance. In this project, a streamlined methodology for testing and characterizing these devices is presented and executed. Analysis to the obtained results is given. Aditionally, a prototype circuit was designed to operate the sensors in a closed-loop mode. Two families of gyroscopes with different thickness were characterized - 40 m and 100 m. The devices presented low sensitivity thresholds due to the presence of a large quadrature error. A phase sensitive demodulation solution was provided to eliminate this noise source. The 40 m presented an overall better performance. A Python Script to extract key noise performance parameters was also displayed.Giroscópios MEMS são micro sensores inerciais que conseguem medir o ângulo de orientação ou a variação ângular de uma rotação. Estes dispositivos têm o potencial de ser usados em aplicações de alta precisão para sistemas de navegação, segurança e para eletrónica comercial. Devido à sua complexidade, os Giroscópios MEMS são propensos a imperfeições que inibem o seu potencial máximo. Através da caracterização extensa destes sensores, é possível validar as metodologias de fabricação, aplicar circuitos de controlo e projetar estruturas mecânicas alternativas que melhorem a sua performance. Neste projeto é apresentada uma metodologia substanciada para testar e caracterizar estes dispositivos. Os resultados obtidos foram analisados. Adicionalmente, foi desenhado um protótipo de um circuito que opera os sensores em circuito fechado. Duas famílias de giroscópios com diferentes espessuras foram caracterizadas - 40 m e 100 m. Os dispositivos apresentaram baixos graus de sensibilidade devido a uma forte influência do erro de quadratura. Foi aplicada uma demodulação sensível à fase para melhoramento da performance. Um programa em Python para extrair parâmetros de ruído na resposta é apresentado

The NASA controls-structures interaction technology program

The interaction between a flexible spacecraft structure and its control system is commonly referred to as controls-structures interaction (CSI). The CSI technology program is developing the capability and confidence to integrate the structure and control system, so as to avoid interactions that cause problems and to exploit interactions to increase spacecraft capability. A NASA program has been initiated to advance CSI technology to a point where it can be used in spacecraft design for future missions. The CSI technology program is a multicenter program utilizing the resources of the NASA Langley Research Center (LaRC), the NASA Marshall Space Flight Center (MSFC), and the NASA Jet Propulsion Laboratory (JPL). The purpose is to describe the current activities, results to date, and future activities of the NASA CSI technology program

Preparation of NiO catalyst on FeCrAI substrate using various techniques at higher oxidation process

The cheap nickel oxide (NiO) is a potential catalyst candidate to replace the expensive available platinum group metals (PGM). However, the current methods to adhere the NiO powder on the metallic substrates are complicated. Therefore, this work explored the development of nickel oxide using nickel (Ni) on FeCrAl substrate through the combination of nickel electroplating and oxidation process for catalytic converter application. The approach was started with assessment of various nickel electroplating process based on the weight gain during oxidation. Then, the next experiment used the best process in which the pre-treatment using the solution of SiC and/or Al2O3 in methanol. The specimens then were carried out to short term oxidation process using thermo gravimetric analysis (TGA) at 1000 o C. Meanwhile, the long term oxidation process was conducted using an automatic furnace at 900, 1000 and 1100 o C. The atomic force microscopy (AFM) was used for surface analysis in nanometer range scale. Meanwhile, roughness test was used for roughness measurement analysis in micrometer range scale. The scanning electron microscope (SEM) attached with energy dispersive X-ray (EDX) were used for surface and cross section morphology analysis. The specimen of FeCrAl treated using ultrasonic prior to nickel electroplating showed the lowest weight gain during oxidation. The surface area of specimens increased after ultrasonic treatment. The electroplating process improved the high temperature oxidation resistance. In short term oxidation process indicated that the ultrasonic with SiC provided the lower parabolic rate constant (kp) and the Al2O3 and NiO layers were also occurred. The Ni layer was totally disappeared and converted to NiO layer on FeCrAl surface after long term oxidation process. From this work, the ultrasonic treatment prior to nickel electroplating was the best method to adhere NiO on FeCrAl substrate