11 research outputs found

    A novel fast resonance frequency tracking method based on the admittance circle for ultrasonic transducers

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    For ultrasonic systems, the resonance frequency tracking (RFT) is the most critical step. The rapid development in advanced material processing and microelectronics package has increased the demand of high speed RFT. Therefore, this paper proposes a fast RFT (FRFT) method according to the characteristics of piezoelectric transducers' (PT) admittance circle. In the proposed method, the PT is driven at two different frequencies, and the PT's admittance is collected and calibrated. Then, the PT's mechanical resonance frequency is derived using the admittance information after calibration. The proposed method is not affected by the parallel capacitor and the matching circuit. Additionally, the optimal initial values of the involved parameters are determined in order to improve the accuracy of the proposed method. Furthermore, an improved method based on multiple tracking is also provided. Simulations and experiments demonstrate that using the proposed FRFT method, the ultrasonic system can track the resonance frequency in a short time with high accuracy

    Power Management ICs for Internet of Things, Energy Harvesting and Biomedical Devices

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    This dissertation focuses on the power management unit (PMU) and integrated circuits (ICs) for the internet of things (IoT), energy harvesting and biomedical devices. Three monolithic power harvesting methods are studied for different challenges of smart nodes of IoT networks. Firstly, we propose that an impedance tuning approach is implemented with a capacitor value modulation to eliminate the quiescent power consumption. Secondly, we develop a hill-climbing MPPT mechanism that reuses and processes the information of the hysteresis controller in the time-domain and is free of power hungry analog circuits. Furthermore, the typical power-performance tradeoff of the hysteresis controller is solved by a self-triggered one-shot mechanism. Thus, the output regulation achieves high-performance and yet low-power operations as low as 12 µW. Thirdly, we introduce a reconfigurable charge pump to provide the hybrid conversion ratios (CRs) as 1⅓× up to 8× for minimizing the charge redistribution loss. The reconfigurable feature also dynamically tunes to maximum power point tracking (MPPT) with the frequency modulation, resulting in a two-dimensional MPPT. Therefore, the voltage conversion efficiency (VCE) and the power conversion efficiency (PCE) are enhanced and flattened across a wide harvesting range as 0.45 to 3 V. In a conclusion, we successfully develop an energy harvesting method for the IoT smart nodes with lower cost, smaller size, higher conversion efficiency, and better applicability. For the biomedical devices, this dissertation presents a novel cost-effective automatic resonance tracking method with maximum power transfer (MPT) for piezoelectric transducers (PT). The proposed tracking method is based on a band-pass filter (BPF) oscillator, exploiting the PT’s intrinsic resonance point through a sensing bridge. It guarantees automatic resonance tracking and maximum electrical power converted into mechanical motion regardless of process variations and environmental interferences. Thus, the proposed BPF oscillator-based scheme was designed for an ultrasonic vessel sealing and dissecting (UVSD) system. The sealing and dissecting functions were verified experimentally in chicken tissue and glycerin. Furthermore, a combined sensing scheme circuit allows multiple surgical tissue debulking, vessel sealer and dissector (VSD) technologies to operate from the same sensing scheme board. Its advantage is that a single driver controller could be used for both systems simplifying the complexity and design cost. In a conclusion, we successfully develop an ultrasonic scalpel to replace the other electrosurgical counterparts and the conventional scalpels with lower cost and better functionality

    Caractérisation des matériaux piézoélectriques dédiés à la génération des décharges plasmas pour applications biomédicales

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    Les transformateurs piézoélectriques se positionnent aujourd’hui comme une alternativetechnologique séduisante face aux solutions classiquement utilisées pour la génération desplasmas froids. Leur haute permittivité, leur faible tension d’alimentation et leur capacité deminiaturisation en font une solution sérieuse et originale pour de nombreuses applications faiblespuissances, notamment dans le domaine biomédical pour la stérilisation, le traitement de surfaceet la décontami-nation des instruments médicaux. Dans le cadre d'un fonctionnement engénérateur plasma, la conversion électromécanique au sein du transformateur s’accompagne depertes mécaniques et diélectriques, souvent converties en chaleur. À ces effets s'ajoute l’influenceproprement dite de la décharge sur le comportement électrique du dispositif. L’évolutiondynamique et fortement non-linéaire de la décharge entraine un comportement méconnu desgrandeurs électriques. Par conséquent, l’étage d’alimentation du transformateur constitue un sujetd’étude au même titre que le transformateur lui-même. De plus, étant donné la configuration duprocessus de génération, qui positionne le matériau piézoélectrique comme source et siège de ladécharge plasma, il devient nécessaire d’analyser la viabilité du dispositif. L’ionisation du milieugazeux environnant le générateur provoque des effets électroniques complexes, susceptiblesd’entrainer des dépôts de matière à la surface du matériau ou d’en éroder la surface. C’est dansce cadre, à l’interface entre le génie électrique et la science des matériaux, que s’articule cettethèse. Une première partie est destinée au développement d’un outil de commande numérique dugénérateur par une boucle de verrouillage de phase, assurant sa continuité de fonctionnementface aux variations des conditions opératoires. Par la suite, une modélisation du générateurplasma dans des configurations proches des décharges à barrières diélectriques est effectuée ;des simulations permettent une estimation de la puissance de décharge à partir d’uneidentification expérimentale des paramètres du modèle. Dans un deuxième temps, nouscherchons à établir une corrélation entre la structure du matériau et ses propriétés électriques ens’appuyant sur une méthodologie de caractérisation multi-échelle, avant et après déchargeplasma. L'étude se focalise principalement sur l'évolution en surface de la structure cristalline et lacomposition chimique, en liaison avec les propriétés fonctionnelles du transformateur aprèsgénération de la décharge. Enfin, une étude en température porte sur l’investigation des effetsd’auto-échauffement du générateur dans ce mode de fonctionnemen

    Inductorless bi-directional piezoelectric transformerbased converters: Design and control considerations.

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    Low Power DEAP Actuator Drive for Heating Valves

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    Proceedings of the 6th International Conference EEDAL'11 Energy Efficiency in Domestic Appliances and Lighting

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    This book contains the papers presented at the sixth international conference on Energy Efficiency in Domestic Appliances and Lighting. EEDAL'11 was organised in Copenhagen, Denmark in May 2011. This major international conference, which was previously been staged in Florence 1997, Naples 2000, Turin 2003, London 2006, Berlin 200h9a s been very successful in attracting an international community of stakeholders dealing with residential appliances, equipment, metering liagnhdti ng (including manufacturers, retailers, consumers, governments, international organisations aangde ncies, academia and experts) to discuss the progress achieved in technologies, behavioural aspects and poliacineds , the strategies that need to be implemented to further progress this important work. Potential readers who may benefit from this book include researchers, engineers, policymakers, and all those who can influence the design, selection, application, and operation of electrical appliances and lighting.JRC.F.7-Renewable Energ

    Piezoelectric transformer based power converters; design and control

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    Sensorless Position Control of Piezoelectric Ultrasonic Motors:a Mechatronic Design Approach

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    This dissertation considers mechatronic systems driven by piezoelectric ultrasonic motors (PUM). The focus is set on optimal system design and sensorless position control. Mechatronic industry faces the challenge to deliver ever more efficient and reliable products while being confronted to increasingly short time to market demands and economic constraints driven by competition. Although optimal design strategies are applied to master this challenge, they do not entirely respond to the given circumstances, as often only local criteria are optimised. In order to obtain a globally optimal solution, the many subfunctions of a mechatronic system and their models must be interrelated and evaluated concurrently from the very beginning of the design process. In this context PUM have been used increasingly during the last decade for various positioning applications in the field of mechatronic systems, laboratory equipment, and consumer electronics where their performances are superior to conventional electromechanical drive systems based on DC or BLDC motors. The position of the mobile component must be controlled. In some cases open-loop control is a solution, but more often than not sensors are used as feedback device in closed-loop control. Sensors are expensive, large in size and add fragile hardware to the device that compromises its reliability. Thus, not only the superior performance is not fully exploited but also the economical feasibility of the PUM drive system is jeopardised. Replacing sensors by advanced control techniques is an approach to these problems that is well established in the field of BLDC motors. Those sensorless control strategies are not directly transferrable, because of the fundamentally different working principles of PUM. Hence, the research of sensorless closed-loop position control techniques applicable to PUM and their validation with digitally controlled functional models is the very topic of this thesis. We propose a dedicated design methodology to this statement of the problem. A core model of the mechatronic system is conceived as general and simple as possible. It then develops for the different interrelated views reflecting the mechanical, electromechanical, drive electronic, sensorial and digital control functions of the global system. Each one becoming more specific and detailed in this process, the different views still enable mutual constraint adjustments and the dynamic integration of results from the other views during the design process. Starting with the stator of the PUM, a view describes the mechanical displacement. An electric equivalent model is written such that power input from the drive electronics is related to the mechanical energy transmitted to the mechanics. The resulting differential equations are solved by the finite element method (FEM). Position feedback configurations in the mobile part of the PUM are modelled analytically in order to be implemented in digital control and their electrical implications are updated to the stator model. In this way, sensors do not necessarily materialise physically any more, but are distributed among the mechanical configuration, the drive electronics and the digital controller. With respect to the sensor data, the controller is not simply receiving finalised data on the measured system parameter, but rather implements the sensor itself in software. Finally, the position detection performance obtained with the aforementioned design methodology was evaluated with the example of mechatronic locking devices actuated by custom-made as well as OEM motors. Functional models of motors, electronics and digital controllers were used to identify the limits of the proposed methods, and suggestions for further research were deduced. These results contribute to the development of robust sensorless position controllers for PUM

    Design of Piezoelectric Transformers for Power Converters by Means of Analytical and Numerical Methods

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    Piezoelectric transformers (PTs) provide several advantages compared to magnetic components, which are higher power density, lower radiated noise, and higher voltage isolation capability. PT must be properly designed to benefit the power converter with the aforementioned advantages. Analytical models are widely used for PT design in order to validate it before constructing the prototype. In this paper, the additional usefulness of finite element analysis (FEA) for PT design is shown. With FEA, it is possible to optimize the PT design not only by maximizing the energy transference but also by cleaning the working frequency range of spurious modes (geometrical 2D/3D effects). Moreover, FEA tools allow the study of other main aspects of the PT design such as manufacturing tolerances or the influence of the fixing layer on PT performance (which is a critical design point). A method for modeling and designing PTs is proposed, combining analytical 1D models and FEA results. The proposed method is validated with measurements of a PT design for a 10-W ac/dc converter prototype for mobile phone battery charger
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