Étude d'interfaces électriques pour les récupérateurs d'énergie vibratoire électrostatiques

Electrostatic vibration energy harvesters (e-VEHs) are systems that convert part of their surroundings' kinetic energy into electrical energy, in order to supply small-scale electronic systems. Inertial E-VEHs are comprised of a mechanical subsystem that revolves around a mobile mass, and of an electrical interface. The mechanical and electrical parts are coupled by an electrostatic transducer. This thesis is focused on improving the performances of e-VEHs by the design of their electrical interface. The first part of this thesis consists in the study of a family of electrical interfaces called charge-pumps conditioning circuits (CPCC). It starts by building a formal theory of CPCCs. State-of-the-art reported conditioning circuits are shown to belong to this family. This family is then completed by a new CPCC topology. An electrical domain comparison of different CPCCs is then reported. Next, a semi-analytical tool allowing for the comparison of CPCC-based e-VEHs accounting for electromechanical effects is reported. The first part of the thesis ends by presenting a novel method for the measurement of e-VEHs' built-in electret potential. The second part of the thesis presents a radically different design approach than what is followed in most of state-of-the-art works on e-VEHs. It advocates for e-VEHs that actively synthesize the dynamics of their mobile mass through their electrical interface. We first show that this enables to convert energy in amounts approaching the physical limits, and from arbitrary types of input vibrations. Then, a complete architecture such an e-VEH is proposed and tested in simulations submitted to human body vibrations.Les récupérateurs d'énergie vibratoire électrostatiques (REV) sont des systèmes convertissant une partie de l'énergie cinétique de leur environnement en énergie électrique, afin d'alimenter de petits systèmes électroniques. Les REV inertiels sont constituées d'un sous-système mécanique bâti autour d'une masse mobile, ainsi que d'une interface électrique. Ces deux blocs sont couplés par un transducteur électrostatique. Cette thèse étudie l'amélioration des performances des REV par la conception optimisée de leur interface électrique. La première partie de cette thèse étudie une famille d'interfaces électriques appelées pompes de charge (PC). On commence par la construction d'une théorie formelle des PC. Des interfaces rapportées dans la littérature sont identifiées comme membres de cette famille. Cette dernière est ensuite complétée par une nouvelle topologie de PC. Une comparaison des différents PC est alors faite dans le domaine électrique, puis un outil semi-analytique est présenté pour la comparaison des PC en prenant en compte le couplage électromécanique. L'étude des PC se termine par la présentation d'une nouvelle méthode de mesure du potentiel d'électret des REV. La deuxième partie de la thèse présente une approche de conception radicalement différente de ce qui est présenté dans les travaux actuels sur les REV. Elle préconise une synthèse active de la dynamique de la masse des REV à travers leur interface électrique. Nous montrons d'abord que cela permet la conversion d'énergie en quantités proches des limites physiques, et ce à partir de vibrations d'entrée de forme arbitraire. Enfin, une architecture pour un tel REV est proposée et testée en simulation

A Novel Characterization Method for Accurate Lumped Parameter Modeling of Electret Electrostatic Vibration Energy Harvesters

International audienceThis letter presents a new method for the characterization of electret transducers, which are typically used in electrostatic vibration energy harvesters (electret e-VEHs). This is the first method allowing to accurately measure the value of the equivalent voltage source representing the electret in lumped parameter models of a wide range of electret e-VEHs. An accurate value for this parameter is critical for design, analysis and optimization, given the increasing complexity of e-VEHs electrical interfaces. Until now, there was no universal method allowing the measurement of this parameter, because of practical difficulties with some geometries, and because of charging non-uniformities. In this letter, the new method is presented, with insights on how to maximize the measurement accuracy. It is then applied to a state-of-the art MEMS electret e-VEH

Series-Parallel Charge Pump Conditioning Circuits for Electrostatic Kinetic Energy Harvesting

International audienceThis paper presents a new family of conditioning circuits used in electrostatic kinetic energy harvesters (e-KEHs), generalizing a previously reported conditioning circuit known as the Bennet's doubler. The proposed topology implements a conditioning scheme described by a rectangular charge-voltage cycle (QV-cycle) of tunable aspect ratio. These circuits show an exponential increase of the converted energy over operation time if studied in the sole electrical domain. The QV-cycle's aspect ratio can be set to values that were previously inaccessible with other exponential conditioning circuits. After a brief intuitive presentation of the new topology, its operation is rigorously analyzed and its dynamics are quantitatively derived in the electrical domain. In particular, the aspect ratio of the rectangular QV-cycle describing the biasing scheme of the transducer is expressed as a function of the circuit's parameters. Practical considerations about the use of the reported conditioning circuits in actual e-KEHs are also presented. These include a discussion on the applications of the proposed conditioning, a description of the effects of electrical nonidealities, and a proposition of an energy extracting interface

Electrostatic vibration energy harvester using an electret-charged mems transducer with an unstable auto-synchronous conditioning circuit

International audienceThis paper reports for the first time experiments using an electrostatic vibration energy harvester comprised of a low voltage electret-charged MEMS transducer joined to an unstable autosynchronous conditioning circuit with rectangular charge-voltage characteristic, also known as the Bennet's doubler conditioning circuit. The experimental results show that the electret voltage, even if of low value, can be used as the necessary pre-charge for these type of electrostatic vibration energy harvesters. Also, the use of such a conditioning circuit with a low-voltage electret capacitive MEMS tranducer instead of the previously-reported conditioning circuits with direct connection to load or through a rectifier, can be advantageous in terms of maximal harvested power for a low-voltage electret, showing up to 95% higher converted power

Characterization of the capacitance variation of electrostatic vibration energy harvesters biased following rectangular charge-voltage diagrams

International audienceThis paper presents for the first time a method to measure the capacitance variation of electrostatic vibration energy harvesters (e-VEHs) that employ conditioning circuits implementing a biasing scheme that can be represented by a rectangular charge-voltage diagram. Given the increasing number of e-VEHs using such complex conditioning circuits and the complex dynamics that are induced from this type of biasing, a mean to assess this measurement is of primary importance for the analysis of e-VEHs. The proposed method is based on the inspection of the voltage evolution across two simple conditioning circuits implementing a rectangular charge-voltage diagrams biasing scheme. After the method is presented, it is carried out for the characterization of a state-of-the-art MEMS e-VEH

Analysis and Comparison of Charge-Pump Conditioning Circuits for Capacitive Electromechanical Energy Conversion

International audienceThis work presents a rigorous electrical analysis of charge-pump conditioning circuits for capacitive energy converters (CEG) with built-in bias voltage. The subsequent implications on the selection of the optimal conditioning circuit are also presented. In particular, the determining role of the application context and constraints on the optimal conditioning circuit choice is discussed. This context is defined by the transducer's capacitance variation amplitude, by the value of the built-in bias of the transducer, and by limitations on the operating voltages across the circuit elements and the transducer

Autonomous energy management interface for electrostatic series-parallel charge pump vibrational energy harvester

International audienceThis paper presents an autonomous energy management interface for electrostatic series-parallel charge pump vibrational energy harvester. It analysis the feasibility of an ultra low power interface for high voltage output harvesters. It introduces a mixed signal high voltage low power intermediate stage designed in 0.35μm ams CMOS technology, that separates the charge pump Conditioning circuit (CC) and the load. It manages the energy extraction from the CC into a buffer capacitor. The energy is accumulated until there is enough to supply a load. This process is achieved autonomously and using only a pre-charged capacitor to supply the control blocks