A wind-flutter energy converter for powering wireless sensors

This paper describes a low-speed wind energy harvesting system that transfers aerodynamically induced flutter energy into electrical energy. A random airflow generates mechanical vibrations due to the fluid-structure interaction between a flexible belt and the airflow. An electromagnetic resonator with copper coils and a permanent magnet is designed to efficiently harvest electrical energy from the induced mechanical vibrations. Different groups of springs are compared at various wind conditions to maximize the power output. Typically ∼7 mW of electrical energy can be obtained at ∼3 m/s wind speed with a 1 m long belt. A power conditioning circuit with a charge pump and a DC-DC converter is used to convert the generated voltage into a stable 3.3 V DC for consumption. It is demonstrated that this generator can be used to drive a commercial wireless temperature sensor.     

基于MEMS的压电微能量采集器的电路研究与测试

微能量采集技术是利用某种效应把周围环境中的某种形式的能量转换成电能,为嵌入式系统和无线传感网络中的MEMS器件供能。本文探讨了一种基于MEMS技术的压电型微能量采集器。微能量采集器工作于低频环境,当给其振动激励信号时,它能够把机械能转换为电能。但是能量采集器直接输出的是交流电压,一般不能直接为器件供能。所以,利用AC-DC电路把交流转换为直流,实现为MEMS器件供能。文中给出了微能量采集器的测试电路,同时给出了测试结果,论证了在低频环境下这种微能量采集器的可行性。     

Electrostrictive polymer harvesting using a nonlinear approach

This paper presents a new application of the ‘synchronized switch harvesting on inductor’ (SSHI) applied to electrostrictive polymers for DC energy harvesting. It is demonstrated that this technique is very effective for harvesting energy from ambient vibrations using electrostrictive polymers. The method consists in adding an electrical switching device connected in parallel with the electrostrictive elements. The switch triggers on maxima or minima of the voltage and realizes a voltage inversion through an inductor. It is shown that, when applied to electrostrictive polymers, the SSHI technique increases the harvesting process efficiency by 700% compared to the classical approach.     

Design and development of a MEMS butterfly resonator using synchronizing beam and out of plane actuation

This paper presents beam modeling techniques for maximizing mechanical sensitivity of a butterfly resonator for gyroscopic applications. We investigate the geometric aspects of synchronizing beam that connects the wings of a butterfly resonator. Our results show that geometric variation in the synchronizing beam can have a large effect on the frequency split and sensitivity of the device. The model simulation shows a sensitivity of \( 10^{ - 12} \)\( (m/^\circ /s) \) for a frequency split of 10 Hz resulting from the optimized synchronized beam. Out of plane actuation was developed to drive and sense the resonators displacement. Fabricated butterfly resonators were tested, and the experimental results show a frequency split of 305 Hz and 400 Hz while the model illustrated a split of 195 Hz and 330 Hz respectively. The design and analysis presented in this paper can further aid the development of MEMS butterfly resonators for inertial sensing applications.

     

An electromagnetic, vibration-powered generator for intelligent sensor systems

This paper describes the design of miniature generators capable of converting ambient vibration energy into electrical energy for use in powering intelligent sensor systems. Such a device acts as the power supply of a microsystem which can be used in inaccessible areas where wires can not be practically attached to provide power or transmit sensor data. Two prototypes of miniature generator are described and experimental results presented. Prototype A is based around two magnets coupled to a coil attached to a cantilever; prototype B is based around four magnets.

For prototype A, experimental results are given for its resonant frequency and its open circuit and loaded output as a function of vibration amplitude. For prototype B, experimental results are given for the generator’s Q factor in air and vacuum, its output voltage as a function of vibration amplitude as well as its magnetic field strength. This generator has been tested on a car engine and shown to produce a peak power of 3.9 mW with an average power of 157 μW.     

Conductive Blended Polymer MEMS Microresonators

This paper presents an all-polymer microelectromechanical system technology in which a crosslinker is used to modify the electromechanical properties. The structural material of these microelectromechanical systems (MEMS) structures is a poly(3,4-ethylenedioxythiophene)/polystyrene sulfonate/polymethyl methacrylate (PEDOT/PSS/PMMA) blended conductive polymer. Microbridge resonators are fabricated using surface micromachining on glass substrates. The electromechanical properties of the polymer microbridges are studied using electrostatic actuation and optical and electrical detection. The resonance frequency of the polymer bridges occurs in the MHz range, with quality factors of the order of 100 when measured in vacuum. Addition of a silane-based crosslinker increases the Young's modulus of the polymer structural material which is reflected in higher resonance frequency, higher pull-in voltage, better long-term stability of the electrical conductivity, and in a decrease in the quality factor of the resonator. The mechanical properties of the polymer resonators are strongly affected by the residual stress because of the low Young's modulus, and by the measurement frequency and the measurement temperature due to the viscoelastic properties of the polymer structural material     

Electroplated nickel based micro-machined disk resonators for high frequency applications

Microelectromechanical system (MEMS) based resonators can be used for filtering and frequency synthesis applications in many subcomponents of radio frequency wireless integrated circuits due to their small size, high level of frequency selectivity, low cost batch fabrication, ease of integration with CMOS circuits. Electroplated nickel is an attractive low cost material for CMOS compatible MEMS due to their low deposition temperatures. Among the different modes of vibration, radial-contour mode resonators are preferred for high frequency applications because they offer higher effective stiffness. Two different types of electroplated nickel based radial-contour bulk-mode circular disk resonator geometries which depend on capacitive actuation and readout technique is presented in this work. Material, mechanical and electrical characterizations were performed on these structures to show their functionality.     

等强度梁式压电振动能量收集器特性研究

为了提高微型悬臂梁式压电振动能量收集器的压电材料利用率,增强其能量转换效率,基于等强度梁理论设计了一种微型压电式振动能量收集器.分析了该能量收集器的力学特性及机电耦合特性,并且与等截面悬臂梁式振动能量收集器进行了对比.研究结果表明:微型等强度梁式压电振动能量收集器的固有频率低、表面应力分布合理、压电材料利用率高、能量输出密度大,其性能明显优于等截面梁式压电振动能量收集器.     

Synchronized switch harvesting applied to self-powered smart systems: Piezoactive microgenerators for autonomous wireless receivers

This paper introduces the conceptual architecture of a fully integrated, truly self-powered structural health monitoring (SHM) scheme. The challenge here is to power an array of numerous distributed actuators and sensors as well as wireless data transmission modules without recurring to heavy and costly wiring. Based on microgenerators which directly convert ambient mechanical energy into electrical energy, using the synchronized switch harvesting (SSH) method, the proposed solution allows avoiding the periodic replacement or reloading of batteries. This addresses environmental and economic issues at the same time, knowing that such elements are heavy, polluting and might be installed in rather inaccessible locations. Indeed, especially in airborne structures saving weight and maintenance cost is of priority importance.Previous work showed that such microgenerators provide a stand-alone power source, whose performances meet the requirements of autonomous wireless transmitters (AWTs) that comprise an acoustic Lamb wave's actuator and a radio frequency (RF) emitter (D. Guyomar, Y. Jayet, L. Petit, E. Lefeuvre, T. Monnier, C. Richard, M. Lallart, Synchronized switch harvesting applied to self-powered smart systems: Piezoactive microgenerators for autonomous wireless transmitters, Sens Actuators A: Phys. 138 (1) (2007) 151–160, doi:10.1016/j.sna.2007.04.009). Following this work, the present contribution presents a further step towards the integration of the SHM technique. It shows the ability of our microgenerators to provide enough energy to give logical autonomy to each self-powered sensing node, named autonomous wireless receiver (AWR), and thus to provide some local (decentralized) pre-processing ability to the SHM system.A preliminary design of the device using off-the-shelf electronics and surface mounted piezoelectric patches will be presented. Since the existence of a positive energy balance between the harvesting capabilities of the SSH technique and the energy requirements of the proposed device will be proved, the system formed by the combination of the AWR with the previously developed AWT, is a proof of concept of truly self-powered smart systems for damage detection in simple structures, setting apart application-specific optimization or miniaturization concerns that will be addressed in future works.     

Double permanent magnet vibration power generator for smart hip prosthesis

Ever since the first studies about biomedical implantable devices, the problem of how to energize them has stood out as both important and notoriously difficult to solve. In order to extend the lifetime of implants, it is imperative to develop power generators that are autonomous, safe and maintenance-free. Energy harvesting is a natural way of meeting these requirements. First, the energy source is theoretically everlasting, a fact that helps to guarantee the autonomy. Second, the energy is obtained from the environment of the application itself, contributing to its safety. Finally, a properly designed energy harvesting system is very unlikely to ever require maintenance. This paper follows this line and describes an electromagnetic power transducer that harvests electrical energy from the human gait and stores it. An efficient power management module uses the stored energy to energize the telemetric system of a smart hip prosthesis implant, enabling the early detection of loosening, the target application of this work. The system is able to extract a total 1912.5 μJ of usable energy under normal walking conditions.