Global sensitivity analysis based on DIRECT-KG-HDMR and thermal optimization of pin-fin heat sink for the platform inertial navigation system

In this study, in order to reduce the local high temperature of the platform in inertial navigation system (PINS), a pin-fin heat sink with staggered arrangement is designed. To reduce the dimension of the inputs and improve the efficiency of optimization, a feasible global sensitivity analysis (GSA) based on Kriging-High Dimensional Model Representation with DIviding RECTangles sampling strategy (DIRECT-KG-HDMR) is proposed. Compared with other GSA methods, the proposed method can indicate the effects of the structural and the material parameters on the maximum temperature at the bottom of the heat sink by using both sensitivity and coupling coefficients. From the results of GSA, it can be found that the structural parameters have greater effects on thermal performance than the material ones. Moreover, the coupling intensities between the structural and material parameters are weak. Therefore, the structural parameters are selected to optimize the thermal performance of the heat sink, and several popular optimization algorithms such as GA, DE, TLBO, PSO and EGO are used for the optimization. Moreover, steady thermal response of the PINS with the optimized heat sink is also studied, and its result shows that the maximum temperature of high temperature region of the platform is reduced by 1.09 degree Celsius compared with the PINS without the heat sink.Comment: 34 pages, 18 figures, 5 table

Development and implementation of automated interferometric microscope for study of MEMS inertial sensors

Microelectromechanical systems (MEMS) are quickly becoming ubiquitous in commercial and military applications. As the use of such devices increases their reliability becomes of great importance. Although there has been significant research in the areas of MEMS errors, there is a lack of work regarding long term reliability of packaged systems. Residual thermomechanical stresses might relax over time which affects physical distances within a package, ultimately influencing the performance of a device. One reason that there has not been sufficient work performed on the long-term effects on structures might be the lack of a tool capable of characterizing the effects. MEMS devices have been measured for shape and its changes using interferometric techniques for some time now. Commercially available systems are able to make high resolution measurements, however they might lack loading options. To study aging effects on components a test might need to run continuously for days or weeks, with systematic operations performed throughout the process. Such a procedure is conducive to an automated data acquisition system. A system has been developed at WPI using a Twyman-Green interferometer and a custom software suite. The abilities of this system are demonstrated through analysis performed on MEMS tuning fork gyroscope (TFG) sensors. Specifically, shape is recorded to investigate die bond relaxation as a function of time and thermal cycle. Also presented are measurements made using stroboscopic illumination on operating gyroscopes, in situ. The effect of temperature on the performance of the sensors is investigated using a customized precision rate table

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

High-accuracy Motion Estimation for MEMS Devices with Capacitive Sensors

With the development of micro-electro-mechanical system (MEMS) technologies, emerging MEMS applications such as in-situ MEMS IMU calibration, medical imaging via endomicroscopy, and feedback control for nano-positioning and laser scanning impose needs for especially accurate measurements of motion using on-chip sensors. Due to their advantages of simple fabrication and integration within system level architectures, capacitive sensors are a primary choice for motion tracking in those applications. However, challenges arise as often the capacitive sensing scheme in those applications is unconventional due to the nature of the application and/or the design and fabrication restrictions imposed, and MEMS sensors are traditionally susceptible to accuracy errors, as from nonlinear sensor behavior, gain and bias drift, feedthrough disturbances, etc. Those challenges prevent traditional sensing and estimation techniques from fulfilling the accuracy requirements of the candidate applications. The goal of this dissertation is to provide a framework for such MEMS devices to achieve high-accuracy motion estimation, and specifically to focus on innovative sensing and estimation techniques that leverage unconventional capacitive sensing schemes to improve estimation accuracy. Several research studies with this specific aim have been conducted, and the methodologies, results and findings are presented in the context of three applications. The general procedure of the study includes proposing and devising the capacitive sensing scheme, deriving a sensor model based on first principles of capacitor configuration and sensing circuit, analyzing the sensor’s characteristics in simulation with tuning of key parameters, conducting experimental investigations by constructing testbeds and identifying actuation and sensing models, formulating estimation schemes is to include identified actuation dynamics and sensor models, and validating the estimation schemes and evaluating their performance against ground truth measurements. The studies show that the proposed techniques are valid and effective, as the estimation schemes adopted either fulfill the requirements imposed or improve the overall estimation performance. Highlighted results presented in this dissertation include a scale factor calibration accuracy of 286 ppm for a MEMS gyroscope (Chapter 3), an improvement of 15.1% of angular displacement estimation accuracy by adopting a threshold sensing technique for a scanning micro-mirror (Chapter 4), and a phase shift prediction error of 0.39 degree for a electrostatic micro-scanner using shared electrodes for actuation and sensing (Chapter 5).PHDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/147568/1/davidsky_1.pd

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

Sijainnin estimointi inertiamittausyksikölla ilman paikannusjärjestelmää

This thesis aims to estimate the position of an inertial measurement unit (IMU) without any tracking device such as GPS. The work includes the calibration of the accelerometer with particle swarm optimization (PSO) to solve the equation, the gyrometer with the extended Kalman filter (EKF) and the magnetometer also with EKF. The calibration is realized with the data from the sensors and Matlab. When the calibration is done, the acceleration is obtained from the accelerometer and the gyrometer. The algorithm employs mostly rotation matrix theory. The performance of the algorithm depends on the success of the calibration. A small error in the estimation of the acceleration leads to a wrong result. This was, nevertheless, to be expected as a double integration with respect to time of a signal with remaining traces of bias is doomed to fail without any correction algorithms. Unfortunately, a working algorithm could not be achieved, pointing out that it may be difficult to realize one without external devices such as GPS.Tässä työssä estimoidaan inertiamittausyksikön (IMU) sijaintia käyttämättä GPS-laitetta. Työ sisältää kiihtyvyysanturin kalibroinnin hiukkasparvioptimointialgorithmilla (PSO), gyroskoopin laajennetulla Kalmanin suodattimella (EKF) ja kompassin EKF:lla. Kalibrointi on suoritettu vain anturien arvoilla ja Matlab-sovelluksella. Anturin kiihtyvyys saa kalibroiduilta kiihtyvyysanturilta ja kompassilta. Algorithmi käyttää rotaatiomatriisin teoria. Algorithmi tehokkuus riippuu kalibroinnista. Pienikin estimointivirhe aiheittaa väärän tuloksen.Työn tulokset voitiin ennustaa koska tuplaintegrointi pienellä virhellä johtaa helposti ja nopeasti tulokset väärään suuntaan. Työn algoritmi vaatii korjausalgoritmin joka pystyisi poistamaan integroinnin virheen. Valitettavasti toimivaa algoritmia ei löydettu, joka viittaa siihen, että sen toteutaminen saattaa olla vaikeaa ilman apulaitetta, kuten GPS-laitetta

Optical pulse distortion and manipulation through polarization effects and chromatic dispersion

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2001.Includes bibliographical references (leaves 112-129).Pulse distortion and shaping mechanisms play a significant role in optical fiber communication and sensing. In this thesis we shall investigate techniques which alleviate pulse deterioration due to polarization effects, and utilize large chromatic dispersion for system performance enhancement. We first demonstrate a method of mitigating polarization mode dispersion (PMD) in fiber optic communication systems. PMD has been a known effect for over a decade. However, it was not an impediment to system performance until recent advances in communication system bit rates. Today, with 10 Gb/s and 40 Gb/s channel rates appearing in new system equipment, PMD prohibits the use of many fiber cables already installed. Current PMD compensation techniques that require feedback control have difficulty meeting the speed and reliability requirements of telecom standards. In the first part of this thesis we investigate alternative compensation schemes which reduce the complexity of the feedback schemes. We next exploit the recent availability of ultra-long length chirped fiber Bragg gratings (FBG). Their enormous chromatic dispersion enables methods of improving current techniques in sensing and high speed optical sampling. In one experiment, we modulate the frequency of a standard distributed Bragg reflector (DBR) laser, and then apply the dispersion of the ultra-long FBG. Picosecond pulses are formed, whose repetition rate is independent of the laser cavity length. Since the gain of the laser is not modulated, the timing jitter is fundamentally limited only by the frequency noise of the laser. Finally, we again utilize the large delay of an ultra-long chirped FBG to implement arbitrary dynamic optical filtering of pulse spectra. In sensing applications such as fiber gyroscopes and optical coherence tomography (OCT), a wide Gaussian spectrum is ideal for low error in the gyro, and high image resolution in OCT. A modelocked fiber laser provides very wide spectra, but the shape can be irregular. We stretch the modelocked pulse temporally with an FBG, and access the frequency components in the time domain. We can then selectively suppress frequencies with an amplitude modulator to synthesize a Gaussian spectrum. Polarization effects and chromatic dispersion will inevitably appear in many optical systems. It is the goal of this thesis to show that their effects can be minimized or utilized for system performance enhancement.by Patrick Chien-pang Chou.Ph.D

FLEXIBLE LOW-COST HW/SW ARCHITECTURES FOR TEST, CALIBRATION AND CONDITIONING OF MEMS SENSOR SYSTEMS

During the last years smart sensors based on Micro-Electro-Mechanical systems (MEMS) are widely spreading over various fields as automotive, biomedical, optical and consumer, and nowadays they represent the outstanding state of the art. The reasons of their diffusion is related to the capability to measure physical and chemical information using miniaturized components. The developing of this kind of architectures, due to the heterogeneities of their components, requires a very complex design flow, due to the utilization of both mechanical parts typical of the MEMS sensor and electronic components for the interfacing and the conditioning. In these kind of systems testing activities gain a considerable importance, and they concern various phases of the life-cycle of a MEMS based system. Indeed, since the design phase of the sensor, the validation of the design by the extraction of characteristic parameters is important, because they are necessary to design the sensor interface circuit. Moreover, this kind of architecture requires techniques for the calibration and the evaluation of the whole system in addition to the traditional methods for the testing of the control circuitry. The first part of this research work addresses the testing optimization by the developing of different hardware/software architecture for the different testing stages of the developing flow of a MEMS based system. A flexible and low-cost platform for the characterization and the prototyping of MEMS sensors has been developed in order to provide an environment that allows also to support the design of the sensor interface. To reduce the reengineering time requested during the verification testing a universal client-server architecture has been designed to provide a unique framework to test different kind of devices, using different development environment and programming languages. Because the use of ATE during the engineering phase of the calibration algorithm is expensive in terms of ATE’s occupation time, since it requires the interruption of the production process, a flexible and easily adaptable low-cost hardware/software architecture for the calibration and the evaluation of the performance has been developed in order to allow the developing of the calibration algorithm in a user-friendly environment that permits also to realize a small and medium volume production. The second part of the research work deals with a topic that is becoming ever more important in the field of applications for MEMS sensors, and concerns the capability to combine information extracted from different typologies of sensors (typically accelerometers, gyroscopes and magnetometers) to obtain more complex information. In this context two different algorithm for the sensor fusion has been analyzed and developed: the first one is a fully software algorithm that has been used as a means to estimate how much the errors in MEMS sensor data affect the estimation of the parameter computed using a sensor fusion algorithm; the second one, instead, is a sensor fusion algorithm based on a simplified Kalman filter. Starting from this algorithm, a bit-true model in Mathworks Simulink(TM) has been created as a system study for the implementation of the algorithm on chip

Technologies for single chip integrated optical gyroscopes

Optical gyroscopes are being employed for navigational purposes for decades now and have achieved comparable or better reliability and performance than rotor-based gyroscopes. Mechanical gyros are however generally bulky, heavy and consume more power which make them unsuitable for miniaturized applications such as cube satellites and drones etc. Therefore, much effort is being expended worldwide to fabricate optical gyros having tactical grade robustness and reliability, small size, weight, cost and power consumption with minimal sacrifice of sensitivity. Integrated optics is an obvious approach to achieving this. This work comprises detailed comparative analysis of different types and structures of integrated optical gyroscopes to find out the suitable option for applications which require a resolution of <10 o/h. Based on the numerical analysis, Add-drop ring resonator-based gyro is found to be a suitable structure for integration which has a predicted shot noise limited resolution of 27 o/h and 2.71 o/h for propagation losses of 0.1 dB/cm and 0.01 dB/cm respectively. An integrated gyro is composed of several optical components which include a laser, 3dB couplers, phase/frequency modulators, sensing cavity and photodetectors. This requires hybrid integration of multiple materials technologies and so choices about which component should be implemented in which technology. This project also undertakes theoretical optimization of few of the above-mentioned optical components in materials systems that might offer the most convenient/tolerant option, this including 3dB coupler, thermo-optic phase modulator and sensing cavity (resonator and waveguide loop). In particular, the sensing element requires very low propagation loss waveguides which can best be realised from Si3N4 or Ta2O5. The optimised Si3N4 or Ta2O5 waveguides however are not optimal for other functions and this is shown and alternatives explored where the Si3N4 or Ta2O5 can easily be co-integrated. The fabrication process of low loss Si3N4 and Ta2O5 waveguides are also reported in this thesis. Si3N4 films were grown by using low pressure chemical vapor deposition (LPCVD) technique. Dry etching of Si3N4 films have been optimized to produce smooth and vertical sidewalls. Experimental results predicted that the propagation loss of 0.009 dB/cm is achievable by using optimum waveguide dimensions and silica cladding with the relatively standard processes available within the Laser Physics Centre at the Australian National University. A CMOS back end of line compatible method was developed to deposit good quality Ta2O5 films and silica claddings through ion beam sputtering (IBS) method. Plasma etching of Ta2O5 waveguides has been demonstrated by using a gas combination of CHF3/SF6/Ar/O2. Oxygen was introduced into the chamber to produce non-vertical sidewalls, so the waveguides could be cladded without voids with IBS silica. Average propagation losses of 0.17 dB/cm were achieved from Ta2O5 waveguides which appeared after extensive investigation to be limited by the spatial inhomogeneity of the processing. Lastly, a detailed theoretical and experimental analysis was performed to find out the possible causes of the higher average propagation loss in Ta2O5 waveguides, some sections being observed with 0.02 dB/cm or lower losses