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Micro Electro Mechanical Systems (MEMS) have an extensive use in different areas of technology. Inertial sensors (accelerometers and gyroscopes) are one of the most widely used devices fabricated using MEMS technology. MEMS accelerometers play an important role in different application areas such as automotive, inertial navigation, guidance, industry, space applications etc. because of low cost, small size, low power, and high reliability. This book presents a detailed SIMULINK model for a conventional capacitive sigma-delta accelerometer system consisting of a MEMS accelerometer, closed-loop readout electronics, and signal processing units (e.g. decimation filters). By using this model, it is possible to estimate the performance of the full accelerometer system including individual noise components, operation range, open loop sensitivity, scale factor, etc. The developed model has been verified through test results using a capacitive MEMS accelerometer, full-custom designed readout electronics, and signal processing unit implemented on a FPGA.
This thesis reports the design and modelling of a MEMS (Micro Electro Mechanical system) based inertial accelerometer. The main motivation to design a differential type of accelerometer is that such a kind of structure allows differential electrostatic actuation and capacitive sensing. They can be operated at the border of stability also so that the "pull in" operation mode can be explored. Such kinds of structures have a wide range of applications because of their high sensitivity. One is in the field of minimally invasive surgery where accelerometers will be combined with gyroscopes to be used in the navigation of surgical tools as a inertial micro unit (IMU). The choice for the design of a structure with 1 Degree ofFreedom(DOF), instead of a 2-DOF device was instigated by the simplicity of the design and by a more efficient 1-DOF dynamic model. The accelerometers were designed and optimized using the MATLAB simulator and COVENTORWARE simulation tool. First set of devices is fabricated using a commercial foundry process called SOIMUMPs. The simulation tests show that the SOl accelerometer system yields 8.8kHz resonant frequency, with a quality factor of 10 and 2.l2mV/g sensitivity. To characterize the accelerometer a new semi automatic tool was formulated for the noise analysis and noise based optimization of the accelerometer design and the analysis estimation shows that there is a trade off between the SIN ratio and the sensitivity and for the given design could be made much better in terms of SIN by tuning its resonant frequency.
Diploma Thesis from the year 2005 in the subject Electrotechnology, grade: Master 9.8/10, , language: English, abstract: Microelectromechanical systems (MEMS) are collection of microsensors and actuators that have the ability to sense its environment and react to changes in that environment with the use of a microcircuit control. They also include the conventional microelectronics packaging, integrating antenna structures for command signals into microelectromechanical structures for desired sensing and actuating functions. The system may also need micropower supply, microrelay, and microsignal processing units. Microcomponents make the system faster, more reliable, cheaper, and capable of incorporating more complex functions. In the beginning of 1990s, MEMS appeared with the aid of the development of integrated circuit fabrication processes, in which sensors, actuators, and control functions are co-fabricated in silicon [1]. Since then, remarkable research progresses have been achieved in MEMS under the strong promotions from both government and industries. In addition to the commercialization of some less integrated MEMS devices, such as microaccelerometers, inkjet printer head, micromirrors for projection, etc., the concepts and feasibility of more complex MEMS devices have been proposed and demonstrated for the applications in such varied fields as microfluidics, aerospace, biomedical, chemical analysis, wireless communications, data storage, display, optics, etc. Some branches of MEMS, appearing as microoptoelectromechanical systems (MOEMS), micro total analysis systems, etc., have attracted a great research since their potential applications’ market.
Most MEMS accelerometers on the market today are capacitive accelerometers that are based on the displacement sensing mechanism. This book is intended to cover recent developments of MEMS silicon oscillating accelerometers (SOA), also referred to as MEMS resonant accelerometer. As contrast to the capacitive accelerometer, the MEMS SOA is based on the force sensing mechanism, where the input acceleration is converted to a frequency output. MEMS Silicon Oscillating Accelerometers and Readout Circuits consists of six chapters and covers both MEMS sensor and readout circuit, and provides an in-depth coverage on the design and modelling of the MEMS SOA with several recently reported prototypes. The book is not only useful to researchers and engineers who are familiar with the topic, but also appeals to those who have general interests in MEMS inertial sensors. The book includes extensive references that provide further information on this topic.
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. This Special Issue on "MEMS Accelerometers" seeks to highlight research papers, short communications, and review articles that focus on: Novel designs, fabrication platforms, characterization, optimization, and modeling of MEMS accelerometers. Alternative transduction techniques with special emphasis on opto-mechanical sensing. Novel applications employing MEMS accelerometers for consumer electronics, industries, medicine, entertainment, navigation, etc. Multi-physics design tools and methodologies, including MEMS-electronics co-design. Novel accelerometer technologies and 9DoF IMU integration. Multi-accelerometer platforms and their data fusion.
Surface micromachined low-capacitance MEMS capacitive accelerometers which integrated CMOS readout circuit generally have a noise above 0.02g. Force-to-rebalance feedback control that is commonly used in MEMS accelerometers can improve the performances of accelerometers such as increasing their stability, bandwidth and dynamic range. However, the controller also increases the noise floor. There are two major sources of the noise in MEMS accelerometer. They are electronic noise from the CMOS readout circuit and thermal-mechanical Brownian noise caused by damping. Kalman filter is an effective solution to the problem of reducing the effects of the noises through estimating and canceling the states contaminated by noise. The design and implementation of a Kalman filter for a MEMS capacitive accelerometer is presented in the thesis in order to filter out the noise mentioned above while keeping its good performance under feedback control. The dynamic modeling of the MEMS accelerometer system and the controller design based on the model are elaborated in the thesis. Simulation results show the Kalman filter gives an excellent noise reduction, increases the dynamic range of the accelerometer, and reduces the displacement of the mass under a closed-loop structure.
Most MEMS accelerometers on the market today are capacitive accelerometers that are based on the displacement sensing mechanism. This book is intended to cover recent developments of MEMS silicon oscillating accelerometers (SOA), also referred to as MEMS resonant accelerometer. As contrast to the capacitive accelerometer, the MEMS SOA is based on the force sensing mechanism, where the input acceleration is converted to a frequency output. MEMS Silicon Oscillating Accelerometers and Readout Circuits consists of six chapters and covers both MEMS sensor and readout circuit, and provides an in-depth coverage on the design and modelling of the MEMS SOA with several recently reported prototypes. The book is not only useful to researchers and engineers who are familiar with the topic, but also appeals to those who have general interests in MEMS inertial sensors. The book includes extensive references that provide further information on this topic.
This book reports on new theories and applications in the field of intelligent systems and computing. It covers computational and artificial intelligence methods, as well as advances in computer vision, current issues in big data and cloud computing, computation linguistics, and cyber-physical systems. It also reports on important topics in intelligent information management. Written by active researchers, the respective chapters are based on selected papers presented at the XIV International Scientific and Technical Conference on Computer Science and Information Technologies (CSIT 2019), held on September 17–20, 2019, in Lviv, Ukraine. The conference was jointly organized by the Lviv Polytechnic National University, Ukraine, the Kharkiv National University of Radio Electronics, Ukraine, and the Technical University of Lodz, Poland, under patronage of Ministry of Education and Science of Ukraine. Given its breadth of coverage, the book provides academics and professionals with extensive information and a timely snapshot of the field of intelligent systems, and is sure to foster new discussions and collaborations among different groups.
The work presented in this dissertation describes the design, fabrication and characterization of a Micro Electro Mechanical System (MEMS) capacitive accelerometer on a flexible substrate. To facilitate the bending of the accelerometers and make them mountable on a curved surface, polyimide was used as a flexible substrate. Considering its high glass transition temperature and low thermal expansion coefficient, PI5878G was chosen as the underlying flexible substrate. Three different sizes of accelerometers were designed in CoventorWare® software which utilizes Finite Element Method (FEM) to numerically perform various analyses. Capacitance simulation under acceleration, modal analysis, stress and pull-in study were performed in CoventorWare®. A double layer UV-LIGA technique was deployed to electroplate the proof mass for increased sensitivity. The proof mass of the accelerometers was perforated to lower the damping force as well as to facilitate the ashing process of the underlying sacrificial layer. Three different sizes of accelerometers were fabricated and subsequently characterized. The largest accelerometer demonstrated a sensitivity of 187 fF/g at its resonant frequency of 800 Hz. It also showed excellent noise performance with a signal to noise ratio (SNR) of 100:1. The accelerometers were also placed on curved surfaces having radii of 3.8 cm, 2.5 cm and 2.0 cm for flexibility analysis. The sensitivity of the largest device was obtained to be 168 fF/g on a curved surface of 2.0 cm radius. The radii of robotic index and thumb fingertips are 1.0 cm and 3.5 cm, respectively. Therefore, these accelerometers are fully compatible with robotics as well as prosthetics. The accelerometers were later encapsulated by Kapton® superstrate in vacuum environment. Kapton® is a polyimide film which possesses similar glass transition temperature and thermal expansion coefficient to that of the underlying substrate PI5878G. The thickness of the superstrate was optimized to place the intermediate accelerometer on a plane of zero stress. The Kapton® films were pre-etched before bonding to the device wafer, thus avoiding spin-coating a photoresist layer at high rpm and possibly damaging the already released micro-accelerometers in the device wafer. The packaged accelerometers were characterized in the same way the open accelerometers were characterized on both flat and curved surfaces. After encapsulation, the sensitivity of the largest accelerometer on a flat and a curved surface with 2.0 cm radius were obtained to be 195 fF/g and 174 fF/f, respectively. All three accelerometers demonstrated outstanding noise performance after vacuum packaging with an SNR of 100:1. Further analysis showed that the contribution from the readout circuitry is the most dominant noise component followed by the Brownian noise of the accelerometers. The developed stresses in different layers of the accelerometers upon bending the substrates were analyzed. The stresses in all cases were below the yield strength of the respective layer materials. AlN cantilevers as tactile sensors were also fabricated and characterized on a flexible substrate. Ti was utilized as the bottom and the top electrode for its smaller lattice mismatch to AlN compared to Pt and Al. The piezoelectric layer of AlN was annealed after sputtering which resulted in excellent crystalline orientation. The XRD peak corresponding to AlN (002) plane was obtained at 36.54o. The fabricated AlN cantilevers were capable of sensing pressures from 100 kPa to 850 kPa which includes soft touching of human index finger and grasping of an object. The sensitivities of the cantilevers were between 1.90 × 10-4 V/kPa and 2.04 × 10-4 V/kPa. The stresses inside the AlN and Ti layer, developed upon full bending, were below the yield strength of the respective layer materials.