Top-Down Behavioral Modeling Methodology of a Piezoelectric Microgenerator For Integrated Power Harvesting Systems

In this study, we developed a top/down methodology for behavioral and structural modeling of multi-domain microsystems. Then, we validated this methodology through a study case : a piezoelectric microgenerator. We also proved the effectiveness of VHDL-AMS language not only for modeling in behavioral and structural levels but also in writing physical models that can predict the experimental results. Finally, we validated these models by presenting and discussing simulations results.Comment: Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/handle/2042/16838

Design, Fabrication and Characterization of a Piezoelectric Microgenerator Including a Power Management Circuit

We report in this paper the design, fabrication and experimental characterization of a piezoelectric MEMS microgenerator. This device scavenges the energy of ambient mechanical vibrations characterized by frequencies in the range of 1 kHz. This component is made with Aluminum Nitride thin film deposited with a CMOS compatible process. Moreover we analyze two possible solutions for the signal rectification: a discrete doubler-rectifier and a full custom power management circuit. The ASIC developed for this application takes advantage of diodes with very low threshold voltage and therefore allows the conversion of extremely low input voltages corresponding to very weak input accelerations. The volume of the proposed generator is inferior to 1mm3 and the generated powers are in the range of 1$\mu$W. This system is intended to supply power to autonomous wireless sensor nodes.Comment: Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/EDA-Publishing

Faults Affecting Energy-Harvesting Circuits of Self-Powered Wireless Sensors and Their Possible Concurrent Detection

We analyze the effects of faults on an energy-harvesting circuit (EHC) providing power to a wireless biomedical multisensor node. We show that such faults may prevent the EHC from producing the power supply voltage level required by the multisensor node. Then, we propose a low-cost (in terms of power consumption and area overhead) additional circuit monitoring the voltage level produced by the EHC continuously, and concurrently with the normal operation of the device. Such a monitor gives an error indication if the generated voltage falls below the minimum value required by the sensor node to operate correctly, thus allowing the activation of proper recovery actions to guarantee system fault tolerance. The proposed monitor is self-checking with regard to the internal faults that can occur during its in-field operation, thus providing an error signal when affected by faults itself

MEMS Technologies for Energy Harvesting

The objective of this chapter is to introduce the technology of Microelectromechanical Systems, MEMS, and their application to emerging energy harvesting devices. The chapter begins with a general introduction to the most common MEMS fabrication processes. This is followed with a survey of design mechanisms implemented in MEMS energy harvesters to provide nonlinear mechanical actuations. Mechanisms to produce bistable potential will be studied, such as introducing fixed magnets, buckling of beams or using slightly slanted clamped-clamped beams. Other nonlinear mechanisms are studied such as impact energy transfer, or the design of nonlinear springs. Finally, due to their importance in the field of MEMS and their application to energy harvesters, an introduction to actuation using piezoelectric materials is given. Examples of energy harvesters found in the literature using this actuation principle are also presented

Conception de microgénérateurs intégrés pour systèmes sur puce autonomes

This PhD thesis addresses the subject of autonomous microsystems and their energy supply. Until now the energy needed for operation of these devices was provided by a finite source, like an electrochemical battery. It implies that the lifetime of the device is directly linked with the size of this reservoir and therefore a trade-off must be made between the size and the longevity of the system. The goal of this work consists in exploring the possibility of using the energy of ambient mechanical vibrations for powering autonomous devices. Furthermore we analyse the possibility of miniaturisation of such generators by using microfabrication techniques and piezoelectric thin layers. A MEMS micro energy scavenger would enable creation of autonomous systems on chip (SoC) or on a package (SoP). During this work we have developed detailed analytical and FEM models of piezoelectric micro power generators. The results obtained were used for design and fabrication of prototype structures using two types of piezoelectric thin layer materials: Aluminium Nitride (AlN) and Lead Zirconate Titanate (PZT). We have proven that these devices can generate powers up to several microwatts on a matched resistive load. We have also shown that in conjunction with special power management ASICs they can charge energy storage elements from very low amplitude vibrations. Finally we have assembled the entire energy harvesting system as a System on a Package. The presented devices are at the moment the sole examples of MEMS piezoelectric micro power generators adapted for ambient vibration energy harvesting. This PhD work is a part of the VIBES (VIBration Energy Scavenging) project founded by the European Commission (IST-1-STREP-507911).Cette thèse explore la thématique des microsystèmes autonomes, notamment la problématique de leur alimentation en énergie. Jusqu'à présent, l'énergie nécessaire pour faire fonctionner ces dispositifs était fournie par une source finie, par exemple une batterie électrochimique. Cela implique, qu'après un certain temps, le réservoir doit être rempli, sinon le dispositif cesse de fonctionner. De plus, un compromis doit être fait entre la taille et la durée de vie du système. L'objectif de ce travail est d'étudier la possibilité d'alimenter de tels systèmes à partir de l'énergie des vibrations mécaniques ambiantes. Nous nous sommes focalisés sur la miniaturisation du dispositif de récupération d'énergie, et sur la possibilité de son élaboration en employant les techniques de micro fabrication et les couches minces piézoélectriques. L'utilisation d'un dispositif de type MEMS permettrait de créer des systèmes autonomes sur une seule puce (SoC) où dans un boîtier (SoP). Au cours de cette thèse nous avons créé des modèles analytiques et par éléments finis des structures de générateurs piézoélectriques. Nous avons conçu et fabriqué les dispositifs en utilisant deux matériaux piézoélectriques : le nitrure d'aluminium (AlN) et le zirconate titanate de plomb (PZT). Nous avons démontré que de telles structures peuvent fournir une puissance de l'ordre de quelques microwatts. De plus, avec des circuits spécifiques de gestion de puissance elles permettent de charger des dispositifs de stockage à partir des vibrations d'une très faible amplitude. Les dispositifs présentés sont pour le moment les seuls microgénérateurs piézoélectriques au monde adaptés aux vibrations ambiantes. Cette thèse s'inscrit dans le cadre du projet VIBES (VIBration Energy Scavenging) qui est un STREP du sixième programme cadre de l'Union Européenne (IST-1-STREP-507911)

Enhanced models for power output prediction from resonant piezoelectric micro power generators

ISBN du colloque : 978-91-631-9280-7International audienceThis paper presents a detailed model of a resonant power harvesting device using the piezoelectric effect to convert the energy of ambient mechanical vibrations into useful electrical energy. The model treats the two most common cases of piezoelectric device configurations: a symmetric bimorph (macro devices) and an asymmetric bimorph (MEMS devices). In comparison with previously presented solutions for such structures, many significant improvements have been introduced and a good agreement with FEM simulation has been found

Modeling of Piezoelectric MEMS Vibration Energy

International audienc

Conception de microgénérateurs intégrés pour SoC autonomes

National audienc

MEMS Vibration Energy Harvesting Devices With Passive Resonance Frequency Adaptation Capability

International audienceFurther advancement of ambient mechanical vibration energy harvesting depends on finding a simple yet efficient method of tuning the resonance frequency of the harvester to match the one dominant in the environment. We propose an innovative approach to achieve a completely passive, wideband adaptive system by employing mechanical nonlinear strain stiffening. We present analytical analysis of the underlying idea as well as experimental results obtained with custom fabricated MEMS devices. Nonlinear behavior is obtained through high built-in stresses between layers in these devices. We report experimentally verified frequency adaptability of over 36% for a clamped-clamped beam device at 2 g input acceleration. We believe that the proposed solution is perfectly suited for autonomous industrial machinery surveillance systems, where high amplitude vibrations that are necessary for enabling this solution, are abundant

Piezoelectric vibration harvesting device with automatic resonance frequency tracking capability

International audienceFurther development in the area of vibration energy harvesting is limited by the lack of efficient methods to adapt the harvester to its surroundings. To this end, we propose an innovative passive way of automatic passive resonance frequency tracking. We present a new approach employing mechanical non-linear behaviour of the system to track the vibration frequency peak. An analytical model representing these nonlinear harvesting systems has been developed and analysed. Experimental results obtained with custom fabricated MEMS devices show an experimentally verified frequency adaptability of over 36% for a clamped-clamped beam device at 2g (1g=9.81m.s-2 ) input acceleration. We believe that the proposed solution is perfectly suited for autonomous industrial machinery surveillance systems, where vibrations with high accelerations that are necessary for enabling this solution are abundant