6,589 research outputs found

    Design and Implementation of an Integrated Biosensor Platform for Lab-on-a-Chip Diabetic Care Systems

    Get PDF
    Recent advances in semiconductor processing and microfabrication techniques allow the implementation of complex microstructures in a single platform or lab on chip. These devices require fewer samples, allow lightweight implementation, and offer high sensitivities. However, the use of these microstructures place stringent performance constraints on sensor readout architecture. In glucose sensing for diabetic patients, portable handheld devices are common, and have demonstrated significant performance improvement over the last decade. Fluctuations in glucose levels with patient physiological conditions are highly unpredictable and glucose monitors often require complex control algorithms along with dynamic physiological data. Recent research has focused on long term implantation of the sensor system. Glucose sensors combined with sensor readout, insulin bolus control algorithm, and insulin infusion devices can function as an artificial pancreas. However, challenges remain in integrated glucose sensing which include degradation of electrode sensitivity at the microscale, integration of the electrodes with low power low noise readout electronics, and correlation of fluctuations in glucose levels with other physiological data. This work develops 1) a low power and compact glucose monitoring system and 2) a low power single chip solution for real time physiological feedback in an artificial pancreas system. First, glucose sensor sensitivity and robustness is improved using robust vertically aligned carbon nanofiber (VACNF) microelectrodes. Electrode architectures have been optimized, modeled and verified with physiologically relevant glucose levels. Second, novel potentiostat topologies based on a difference-differential common gate input pair transimpedance amplifier and low-power voltage controlled oscillators have been proposed, mathematically modeled and implemented in a 0.18ÎŒm [micrometer] complementary metal oxide semiconductor (CMOS) process. Potentiostat circuits are widely used as the readout electronics in enzymatic electrochemical sensors. The integrated potentiostat with VACNF microelectrodes achieves competitive performance at low power and requires reduced chip space. Third, a low power instrumentation solution consisting of a programmable charge amplifier, an analog feature extractor and a control algorithm has been proposed and implemented to enable continuous physiological data extraction of bowel sounds using a single chip. Abdominal sounds can aid correlation of meal events to glucose levels. The developed integrated sensing systems represent a significant advancement in artificial pancreas systems

    An Update on Power Quality

    Get PDF
    Power quality is an important measure of fitness of electricity networks. With increasing renewable energy generations and usage of power electronics converters, it is important to investigate how these developments will have an impact to existing and future electricity networks. This book hence provides readers with an update of power quality issues in all sections of the network, namely, generation, transmission, distribution and end user, and discusses some practical solutions

    Index to NASA Tech Briefs, 1975

    Get PDF
    This index contains abstracts and four indexes--subject, personal author, originating Center, and Tech Brief number--for 1975 Tech Briefs

    Modeling and Analysis of Power Processing Systems

    Get PDF
    The feasibility of formulating a methodology for the modeling and analysis of aerospace electrical power processing systems is investigated. It is shown that a digital computer may be used in an interactive mode for the design, modeling, analysis, and comparison of power processing systems

    Fault-Tolerant Control of a Flux-switching Permanent Magnet Synchronous Machine

    Get PDF
    Je jasnĂ©, ĆŸe nejĂșspěơnějĆĄĂ­ konstrukce zahrnuje postup vĂ­cefĂĄzovĂ©ho ƙízenĂ­, ve kterĂ©m kaĆŸdĂĄ fĂĄze mĆŻĆŸe bĂœt povaĆŸovĂĄna za samostatnĂœ modul. Provoz kterĂ©koliv z jednotek musĂ­ mĂ­t minimĂĄlnĂ­ vliv na ostatnĂ­, a to tak, ĆŸe v pƙípadě selhĂĄnĂ­ jednĂ© jednotky ostatnĂ­ mohou bĂœt v provozu neovlivněny. ModulĂĄrnĂ­ ƙeĆĄenĂ­ vyĆŸaduje minimĂĄlnĂ­ elektrickĂ©, magnetickĂ© a tepelnĂ© ovlivněnĂ­ mezi fĂĄzemi ƙízenĂ­ (měniče). SynchronnĂ­ stroje s pulznĂ­m tokem a permanentnĂ­mi magnety se jevĂ­ jako atraktivnĂ­ typ stroje, jejĂ­ĆŸ pƙednostmi jsou vysokĂœ kroutĂ­cĂ­ moment, jednoduchĂĄ a robustnĂ­ konstrukce rotoru a skutečnost, ĆŸe permanentnĂ­ magnety i cĂ­vky jsou umĂ­stěny společně na statoru. FS-PMSM jsou poměrně novĂ© typy stƙídavĂ©ho stroje stator-permanentnĂ­ magnet, kterĂ© pƙedstavujĂ­ vĂœznamnĂ© pƙednosti na rozdĂ­l od konvenčnĂ­ch rotorĆŻ - velkĂœ kroutĂ­cĂ­ moment, vysokĂœ točivĂœ moment, v podstatě sinusovĂ© zpětnĂ© EMF kƙivky, zĂĄroveƈ kompaktnĂ­ a robustnĂ­ konstrukce dĂ­ky umĂ­stěnĂ­ magnetĆŻ a vinutĂ­ kotvy na statoru. SrovnĂĄnĂ­ vĂœsledkĆŻ mezi FS-PMSM a klasickĂœmi motory na povrchu upevněnĂœmi PM (SPM) se stejnĂœmi parametry ukazuje, ĆŸe FS-PMSM vykazuje větĆĄĂ­ vzduchovĂ© mezery hustoty toku, vyĆĄĆĄĂ­ točivĂœ moment na ztrĂĄty v mědi, ale takĂ© vyĆĄĆĄĂ­ pulzaci dĂ­ky reluktančnĂ­mu momentu. Pro stroje buzenĂ© permanentnĂ­mi magnety se jednĂĄ o tradičnĂ­ rozpor mezi poĆŸadavkem na vysokĂœ kroutĂ­cĂ­ moment pod zĂĄkladnĂ­ rychlostĂ­ (oblast konstantnĂ­ho momentu) a provozem nad zĂĄkladnĂ­ rychlostĂ­ (oblast konstantnĂ­ho vĂœkonu), zejmĂ©na pro aplikace v hybridnĂ­ch vozidlech. Je pƙedloĆŸena novĂĄ topologie synchronnĂ­ho stroje s permanentnĂ­mi magnety a spĂ­nanĂœm tokem odolnĂ©ho proti poruchĂĄm, kterĂĄ je schopnĂĄ provozu během vinutĂ­ naprĂĄzdno a zkratovanĂ©ho vinutĂ­ i poruchĂĄch měniče. SchĂ©ma je zaloĆŸeno na dvojitě vinutĂ©m motoru napĂĄjenĂ©m ze dvou oddělenĂœch vektorově ƙízenĂœch napěƄovĂœch zdrojĆŻ. VinutĂ­ jsou uspoƙádĂĄna takovĂœm zpĆŻsobem, aby tvoƙila dvě nezĂĄvislĂ© a oddělenĂ© sady. Simulace a experimentĂĄlnĂ­ vĂœzkum zpƙesnĂ­ vĂœkon během obou scĂ©náƙƯ jak za normĂĄlnĂ­ho provozu, tak za poruch včetně zkratovĂœch zĂĄvad a ukĂĄĆŸĂ­ robustnost pohonu za těchto podmĂ­nek. Tato prĂĄce byla publikovĂĄna v deseti konferenčnĂ­ch pƙíspěvcĂ­ch, dvou časopisech a kniĆŸnĂ­ kapitole, kde byly pƙedstaveny jak topologie pohonu a aplikovanĂĄ ƙídĂ­cĂ­ schĂ©mata, tak analĂœzy jeho schopnosti odolĂĄvat poruchĂĄm.It has become clear that the most successful design approach involves a multiple phase drive in which each phase may be regarded as a single-module. The operation of any one module must have minimal impact upon the others, so that in the event of that module failing the others can continue to operate unaffected. The modular approach requires that there should be minimal electrical, magnetic and thermal interaction between phases of the drive. Flux-Switching permanent magnet synchronous machines (FS-PMSM) have recently emerged as an attractive machine type virtue of their high torque densities, simple and robust rotor structure and the fact that permanent magnets and coils are both located on the stator. Flux-switching permanent magnet (FS-PMSM) synchronous machines are a relatively new topology of stator PM brushless machine. They exhibit attractive merits including the large torque capability and high torque (power) density, essentially sinusoidal back-EMF waveforms, as well as having a compact and robust structure due to both the location of magnets and armature windings in the stator instead of the rotor as those in the conventional rotor-PM machines. The comparative results between a FS-PMSM and a traditional surface-mounted PM (SPM) motor having the same specifications reveal that FS-PMSM exhibits larger air-gap flux density, higher torque per copper loss, but also a higher torque ripple due to cogging -torque. However, for solely permanent magnets excited machines, it is a traditional contradiction between the requests of high torque capability under the base-speed (constant torque region) and wide speed operation above the base speed (constant power region) especially for hybrid vehicle applications. A novel fault-tolerant FS-PMSM drive topology is presented, which is able to operate during open- and short-circuit winding and converter faults. The scheme is based on a dual winding motor supplied from two separate vector-controlled voltage-sourced inverter drives. The windings are arranged in a way so as to form two independent and isolated sets. Simulation and experimental work will detail the driver’s performance during both healthy- and faulty- scenarios including short-circuit faults and will show the drive robustness to operate in these conditions. The work has been published in ten conference papers, two journal papers and a book chapter, presenting both the topology of the drive and the applied control schemes, as well as analysing the fault-tolerant capabilities of the drive.

    Design and Measurement of Integrated Converters for Belt-driven Starter-generator in 48 V Micro/mild Hybrid Vehicles

    Get PDF
    With reference to a 48 V belt-driven starter-generator, used in micro/mild hybrid vehicles, the paper shows the design and measurement of an integrated H-bridge and of a compact DC/DC converter, both fabricated in low-cost HV-MOS technology. The H-bridge is in charge of rotor excitation and, thanks to a direct copper bonding of the HV-MOS devices on a ceramic substrate, it ensures a full-integrated solution with low ON-resistance values. The compact DC/DC converter interfaces the 48 V power domain with the lower voltage domain of sensing and control electronics, such as 5 V and 1.65 V in this case study, without using cumbersome inductors and transformers. The latter are difficult to integrate in silicon technology. The converter has a multi stage architecture, where each stage implements a switched capacitor regulation. Multiple voltage outputs are supported, with a configurable regulation factor, sustaining an input voltage variation from 6 V (in case of cranking) up to 60 V. Specific design techniques have been implemented to reduce electromagnetic interference (EMI), typical of switching converters. Experimental measurements on fabricated prototype chipsets confirm the suitability of the presented designs for low-EMI 48 V application

    Survey on Photo-Voltaic Powered Interleaved Converter System

    Get PDF
    Renewable energy is the best solution to meet the growing demand for energy in the country. The solar energy is considered as the most promising energy by the researchers due to its abundant availability, eco-friendly nature, long lasting nature, wide range of application and above all it is a maintenance free system. The energy absorbed by the earth can satisfy 15000 times of today’s total energy demand and its hundred times more than that our conventional energy like coal and other fossil fuels. Though, there are overwhelming advantages in solar energy, It has few drawbacks as well such as its low conversion ratio, inconsistent supply of energy due to variation in the sun light, less efficiency due to ripples in the converter, time dependent and, above all, high capitation cost. These aforementioned flaws have been addressed by the researchers in order to extract maximum energy and attain hundred percentage benefits of this heavenly resource. So, this chapter presents a comprehensive investigation based on photo voltaic (PV) system requirements with the following constraints such as system efficiency, system gain, dynamic response, switching losses are investigated. The overview exhibits and identifies the requirements of a best PV power generation system

    STUDY OF FULLY-INTEGRATED LOW-DROPOUT REGULATORS

    Get PDF
    Department of Electrical EngineeringThis thesis focuses on the introduction of fully-integrated low-dropout regulators (LDOs). Recently, for the mobile and internet-of-things applications, the level of integration is getting higher. LDOs get popular in integrated circuit design including functions such as reducing switching ripples from high-efficiency regulators, cancelling spurs from other loads, and giving different supply voltages to loads. In accordance with load applications, choosing proper LDOs is important. LDOs can be classified by the types of power MOSEFT, the topologies of error amplifier, and the locations of dominant pole. Analog loads such as voltage-controlled oscillators and analog-to-digital converters need LDOs that have high power-supply-rejection-ratio (PSRR), high accuracy, and low noise. Digital loads such as DRAM and CPU need fast transient response, a wide range of load current providable LDOs. As an example, we present the design procedure of a fully-integrated LDO that obtains the desired PSRR. In analog LDOs, we discuss advanced techniques such as local positive feedback loop and zero path that can improve stability and PSRR performance. In digital LDOs, the techniques to improve transient response are introduced. In analog-digital hybrid LDOs, to achieve both fast transient and high PSRR performance in a fully-integrated chip, how to optimally combine analog and digital LDOs is considered based on the characteristics of each LDO type. The future work is extracted from the considerations and limitations of conventional techniques.clos
    • 

    corecore