Wideband Micro-Power Generators for Vibration Energy Harvesting

Wideband;Vibration energy harvesting;Electrical and Computer Engineering

Soliman, Mostafa

University of Waterloo

关键词: Wideband;    Vibration energy harvesting;    Electrical and Computer Engineering;   

Others  :  https://uwspace.uwaterloo.ca/bitstream/10012/4584/1/Mostafa-Thesis-Final-vesrion2.pdf

瑞士|英语

来源: UWSPACE Waterloo Institutional Repository

【 摘 要 】

Energy harvesters collect and convert energy available in the environment intouseful electrical power to satisfy the power requirements of autonomous systems.Vibration energy is a prevalent source of waste energy in industrial and built environments.Vibration-based energy harvesters, or vibration-based micro powergenerators (VBMPGs), utilize a transducer, a mechanical oscillator in this application,to capture kinetic energy from environmental vibrations and to convert it intoelectrical energy using electromagnetic, electrostatic, or piezoelectric transductionmechanisms.A key design feature of all VBMPGs, regardless of their transduction mechanism,is that they are optimally tuned to harvest vibration energy within a narrowfrequency band in the neighborhood of the natural frequency of the oscillator. Outsidethis band, the output power is too low to be conditioned and utilized. Thislimitation is exacerbated by the fact that VBMPGs are also designed to have highquality factors to minimize energy dissipation, further narrowing the optimal operatingfrequency band. Vibrations in most environments, however, are random andwideband. As a result, VBMPGs can harvest energy only for a relatively limitedperiod of time, which imposes excessive constraints on their usability.A new architecture for wideband VBMPGs is the main contribution of thisthesis. The new design is general in the sense that it can be applied to any of thethree transduction mechanisms listed above. The linear oscillator is replaced witha piecewise-linear oscillator as the energy-harvesting element of the VBMPG. Thenew architecture has been found to increase the bandwidth of the VBMPG duringa frequency up-sweep, while maintaining the same bandwidth in a frequency downsweep.Experimental results show that using the new architecture results in a 313%increase in the width of the bandwidth compared to that produced by traditionalarchitecture. Simulations show that under random-frequency excitations, the newarchitecture collects more energy than traditional architecture.In addition, the knowledge acquired has been used to build a wideband electromagneticVBMPG using MicroElectroMechanical Systems, MEMS, technology.This research indicates that a variety of piecewise-linear oscillators, including impactoscillators, can be implemented on MPG structures that have been built usingMEMS technology. When the scale of the MPGs is reduced, lower losses are likelyduring contact between the moving oscillators and the stopper, which will lead toan increase in bandwidth and hence in the amount of energy collected.Finally, a design procedure has been developed for optimizing such widebandMPGs. This research showed that wideband MPGs require two design optimizationsteps in addition to the traditional technique, which is used in all types ofgenerators, of minimizing mechanical energy losses through structural design andmaterial selection. The first step for both regular and wideband MPGs minimizesthe MPG damping ratio by increasing the mass and stiffness of the MPG by a commonfactor until the effect of size causes the rate at which energy losses increaseto accelerate beyond that common factor. The second step, which is specific towideband MPGs, tailors the output power and bandwidth to fit the ProbabilityDensity Function, PDF, of environmental vibrations. A figure of merit FoM wasdevised to quantify the quality of this fit. Experimental results show that with thisprocedure, the bandwidth at half-power level increases to more than 600% of theoriginal VBMPG bandwidth.