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

MICROACELERÓMETRO MEMS, DISEÑO, ANÁLISIS ESTRUCTURAL Y ELECTROSTÁTICO (MEMS MICROACCELEROMETER, DESIGN, STRUCTURAL AND ELECTROSTATIC)

En ese trabajo se describe el diseñó de un microacelerómetro de bajo consumo de potencia con tecnología MEMS; se obtuvo un microacelerómetro de 159 μm x 109 μm. Se realizó un mesh por el método de elementos finitos, para su análisis estructural y electrostático, esto con el software COMSOL MULTIPHYSICS 5.1, para comprobar su eficiencia y buen funcionamiento. Debido a que es un sensor de movimiento inercial tipo capacitivo, su principal aplicación es en los disparadores de bolsas de aire de automóviles; el cual podría impactar en la industria automotriz y de consumo.This paper describes the design of a low power consumption micro-accelerometer with MEMS technology; the dimensions of microaccelerometer computed were 159 μm x 109 μm, a mesh was obtained by the finite element method, for its structural and electrostatic analysis, this with the COMSOL MULTIPHYSICS 5.1 software, to verify its efficiency and good performance. The main application of microaccelerometers is in automobile airbag triggers, which could impact the automotive and consumer industries

Adjustable Nonlinear Springs to Improve Efficiency of Vibration Energy Harvesters

Vibration Energy Harvesting is an emerging technology aimed at turning mechanical energy from vibrations into electricity to power microsystems of the future. Most of present vibration energy harvesters are based on a mass spring structure introducing a resonance phenomenon that allows to increase the output power compared to non-resonant systems, but limits the working frequency bandwidth. Therefore, they are not able to harvest energy when ambient vibrations' frequencies shift. To follow shifts of ambient vibration frequencies and to increase the frequency band where energy can be harvested, one solution consists in using nonlinear springs. We present in this paper a model of adjustable nonlinear springs (H-shaped springs) and their benefits to improve velocity-damped vibration energy harvesters' (VEH) output powers. A simulation on a real vibration source proves that the output power can be higher in nonlinear devices compared to linear systems (up to +48%).Comment: Please refer to paper "Nonlinear H-Shaped Springs to Improve Efficiency of Vibration Energy Harvesters", Journal of Applied Mechanics | Volume 80 | Issue 6, 2013 -- Paper No: JAM-12-1470; doi: 10.1115/1.4023961 -- for the published version of this articl

Energy Harvesters and Self-powered Sensors for Smart Electronics

This book is a printed edition of the Special Issue “Energy Harvesters and Self-Powered Sensors for Smart Electronics” that was published in Micromachines, which showcases the rapid development of various energy harvesting technologies and novel devices. In the current 5G and Internet of Things (IoT) era, energy demand for numerous and widely distributed IoT nodes has greatly driven the innovation of various energy harvesting technologies, providing key functionalities as energy harvesters (i.e., sustainable power supplies) and/or self-powered sensors for diverse IoT systems. Accordingly, this book includes one editorial and nine research articles to explore different aspects of energy harvesting technologies such as electromagnetic energy harvesters, piezoelectric energy harvesters, and hybrid energy harvesters. The mechanism design, structural optimization, performance improvement, and a wide range of energy harvesting and self-powered monitoring applications have been involved. This book can serve as a guidance for researchers and students who would like to know more about the device design, optimization, and applications of different energy harvesting technologies

A Novel Micro Piezoelectric Energy Harvesting System

(Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2007(PhD) -- İstanbul Technical University, Institute of Science and Technology, 2007Bu tezde yeni bir titreşim temelli mikro enerji harmanlayıcı sistemi önerilmiştir. Titreşimler ve ani hareketler, mekanik yapının sadece eğilmesine değil aynı zamanda gerilmesine yol açar, bu sayede sistem doğrusal olmayan bölgede çalışır. İnce piezoelektrik film tabakası mekanik stresi elektrik enerjisine çevirir. Mikrowatt mertebesinde güç seviyeleri mm3’lük aletlerle elde edilebilir, bu da güneş panellerinde elde edilen güç yoğunlukları kadar yüksektir. Algılayıcı kabiliyeti sayesinde bilgi depolayabilen, kum tanesi büyüklüğünde olan ve üretiminde kullanılan temel malzeme silikon olan bu aletler “zeki kum” olarak isimlendirilmiştir. Mekanik yapının modellenmesi ve tasarımı geliştirilmiş ve üretim sonuçları da ayrıca verilmiştir. Sistemin bilgi gönderebilmesi ve alabilmesi amacıyla iyi bilinen RFID teknolojisi tabanlı bir kablosuz haberleşme yöntemi önerilmiştir. Bu bağlamda, paket taşımacılığında sürekli ivme denetleme, sınır güvenliği için kendinden beslemeli algılayıcılar, çabuk bozulan yiyeceklerin taşımacılığında sıcaklık denetleme ve pilsiz kalp atışı algılayıcı gibi birçok uygulama önerilmiştir.In this thesis, a novel, vibration based micro energy harvester system is proposed. Vibrations or sudden movements cause the mechanical structure does not only bend but also stretch, thus working in non-linear regime. The piezoelectric thin film layer converts the mechanical stress into the electrical energy. Microwatts of power can be achieved with a mm3 device which yields a high power density levels on the order of the solar panels. This device is named “smart sand”, because it has also sensor capabilities that can store information, its size is almost a sand grain and the main material used for the fabrication is silicon. The modeling and design of the mechanical structure has been developed and fabrication results have also been given in the thesis. In order for the system to send and receive the information, a wireless communication scheme is proposed which is based on the well-known RFID technology. In this concept, several applications are proposed such as continuous acceleration monitoring in package delivery, self-powered sensors for homeland security, temperature monitoring of the perishable food item delivery and a batteryless heart rate sensor.DoktoraPh

Active vibration control of a flexible robot link using piezoelectric actuators

Nuisance vibrations are a concern throughout the engineering realm, and many re-searchers are dedicated to finding a solution to attenuate them. This research primarily focusses upon the suppression of vibrations in a robot system, with the control system being designed so that it is both affordable and lightweight. Such constraints aim to provide a solution that may be utilised in a variety of applications. The utilisation of piezoelectric elements as both actuators and sensors provides several advantages in that they are lightweight, easily integrated into an existing system and have a good force to weight ratio when used as actuators. To read and control these elements a single board computer was employed, in acknowledgement of the constraining parameters of the design. The amalgamation of vibration control and robotics has lent to the re-search being conducted with separate objectives set, isolating certain elements of the overall system design for validation. Ultimately, these separate investigations progress to the integration of the robot and control systems prior to further research concerning nonlinear vibrations, dynamic control and the discrete-time domain modelling of the system.This research first investigates the viability of the chosen components as a vibration attenuation solution. In addition, analytical models of the system have been created, for two types of sensors to determine the most effective; an inertial measurement unit and a collocated pair of piezoelectric sensors. These models are based on Euler-Bernoulli beam theory and aim to validate the control theory through a comparison of the experimental data. These experiments isolate the vibration problem from a robot system through the investigation of the control of a long slender beam envisioned as a robot manipulator link, but excited using a shaker platform in a sinusoidal manner. An observation of the theory related to the voltage produced by the piezoelectric elements, suggests that even with the application of only proportional control by the system, the controlled output would have components indicative of both proportional and derivative control. This observation and the underlying theory are further analysed within this research.The next objectives are to compare the performance of the control system developed in this research which utilises a Raspberry Pi 3B+ [1] with one that employs a dSPACE MicroLabBox [2], and to determine the suitability of the former for use with robot sys-tems. With the former ensuring that the constraints placed on the design, those which influenced the selection of the components, does not conclude to the dSPACE Micro-LabBox system being overtly preferable. The latter investigates both the impact of the system’s inclusion on the functionality of the system and the system’s perform-ance with respect to the intended application. The KUKA LBR iiwa 7 R800 [3] robot manipulator is utilised to satisfy this objective, wherein the link is mounted on the end effector of the manipulator acting as an eighth link. The final investigation in this research pertains to the attenuation of nonlinear vibrations experienced by a robot manipulator link. Additional components were added to the link to induce a geometric nonlinearity in the system. An analytical model of the amended system was created to validate the theory through comparison with experimental results. The control system was employed for multiple cases to ascertain the level of its performance with regards to the suppression of nonlinear vibrations

Low power strain sensor based on MOS tunneling current.

Sensors, such as pressure sensors, accelerometers and gyroscopes, are very important components in modern portable electronics. A limited source of power in portable electronics is motivating research on new low power sensors. Piezoresistive and capacitive sensing technologies are the most commonly utilized technologies, which typically consume power in the µW to mW range. Tunneling current sensing is attractive for low power applications because the typical tunneling current is in the nA range. This dissertation demonstrates a low power strain sensor based on the tunneling current in a metal-oxide-semiconductor (MOS) structure with a power consumption of a couple of nano-Watts (nW) with a minimum detectable strain of 0.00036%. Both DC and AC measurements were used to characterize the MOS tunneling current strain sensor. The noise level is found to be smallest in the inversion region, and therefore it is best to bias the device in the inversion region. To study the sensitivity in the inversion region, a model is developed to compute the tunneling current as a function of strain in the semiconductor. The model calculates the tunneling current due to electrons tunneling from the conduction band of the semiconductor to the gate (ECB tunneling current) and the tunneling current due to electrons tunneling from the valence band of the semiconductor to the gate (EVB tunneling current). It is found that the ECB tunneling current is sufficient to explain experimental gate leakage current results reported in the literature for MOSFETs with low substrate doping concentration. However, for the tunneling current strain sensor with a higher substrate doping concentration reported here, a model using both ECB and EVB tunneling current is required. The model fits our experiments. During both DC and AC measurements, the MOS tunneling current is found to drift with time. The drift could arise from the trap states within the oxide. The current drift makes it difficult to obtain an absolute measurement of the strain. Combining the tunneling current strain sensor with a resonant sensor may be a good choice because it measures changes in the mechanical resonant frequency, independent of a drift of the tunneling current amplitude