Two-degree-of-freedom velocity-amplified vibrational energy harvester for human motion applications

This paper presents an electromagnetic energy harvester to extract low frequency and low acceleration vibration energy available in a bridge environment. The developed harvester is a multi-mode oscillator with dual electromagnetic transduction mechanisms. The harvester consists of two cantilever beams. The first cantilever beam is split into two equal pieces along its length and the second beam placed in between them coming back to the fixed end and attached at outer end to the first beam. This way instead of a long conventional cantilever beam a compact harvester is fabricated. Two magnets as proof masses are attached to each free end of the beam making it a two degree of freedom system (2-DOF). The magnets are positioned to oscillate inside hand wound coils during operation. An analytical model was developed and COMSOL multiphysics was used to simulate the mode shapes of the harvester. The mathematical model was simulated for open circuit voltage in MATLAB and showed closely matching results with the experimental values. The harvester is characterized in lab for its performance under sinusoidal vibrations at low frequency (3 Hz–15 Hz) and low acceleration (0.01–0.09 g) levels. The 2-DOF harvester has two resonant frequencies of 4.4 Hz and 5.5 Hz and a volume of 333 cm3. It produces maximum voltage of 0.6 V at first resonance on coil-1 and maximum voltage of 1.2 V on coil-2 at second resonance at 0.09 g. At acceleration of 0.09 g the harvester produced 2.51 mW at first resonant frequency and 10.7 mW at second resonance. Moreover, the AC output voltage of the harvester is rectified to DC voltage by a three-stage Cockcroft-Walton multiplier type circuit. The DC power output at 0.05 g was 0.939 mW at first resonance and 0.956 mW at second resonance while maximum voltages of 5.4 V on coil-1 and 4 V on coil-2 were produced.

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A Multiple Degree-of-Freedom Velocity-Amplified Vibrational Energy Harvester: Part B — Modelling

Volume 2: Mechanics and Behavior of Active Materials; Integrated System Design and Implementation; Bioinspired Smart Materials and Systems; Energy Harvesting ◽

10.1115/smasis2014-7511 ◽

2014 ◽

Cited By ~ 5

Author(s):

Valeria Nico ◽

Declan O’Donoghue ◽

Ronan Frizzell ◽

Gerard Kelly ◽

Jeff Punch

Keyword(s):

Energy Harvester ◽

Vibrational Energy ◽

Coupled Model ◽

Electrical Energy ◽

Theoretical Models ◽

Building Blocks ◽

Degree Of Freedom ◽

Harmonic Oscillators ◽

Power Requirement ◽

Non Linear Oscillator

Vibrational energy harvesting has become relevant as a power source for the reduced power requirement of electronics used in wireless sensor networks (WSNs). Vibrational energy harvesters (VEHs) are devices that can convert ambient kinetic energy into electrical energy using three principal transduction mechanisms: piezoelectric, electromagnetic and electrostatic. In this paper, a macroscopic two degree-of-freedom (2Dof) nonlinear energy harvester, which employs velocity amplification to enhance the power scavenged from ambient vibrations, is presented. Velocity amplification is achieved through sequential collisions between free-moving masses, and the final velocity is proportional to the mass ratio and the number of masses. Electromagnetic induction is chosen as the transduction mechanism because it can be readily implemented in a device which uses velocity amplification. The experimental results are presented in Part A of this paper, while in Part B three theoretical models are presented: (1) a coupled model where the two masses of the non-linear oscillator are considered as a coupled harmonic oscillators system; (2) an uncoupled model where the two masses are not linked and collisions between masses can occur; (3) a model that considers both the previous cases. The first two models act as necessary building blocks for the accurate development of the third model. This final model is essential for a better understanding of the dynamics of the 2-Dof device because it can represent the real behaviour of the system and captures the velocity amplification effect which is a key requirement of modelling device of interest in this work. Moreover, this model is essential for a future optimization of geometric and magnetic parameters in order to develop a MEMS scale multi-degree-of-freedom device.

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A C-Battery Scale Energy Harvester: Part B — Transducer Optimization and Modeling

Volume 2: Integrated System Design and Implementation; Structural Health Monitoring; Bioinspired Smart Materials and Systems; Energy Harvesting ◽

10.1115/smasis2015-8908 ◽

2015 ◽

Cited By ~ 1

Author(s):

Elisabetta Boco ◽

Valeria Nico ◽

Ronan Frizzell ◽

Jeff Punch

Keyword(s):

Energy Harvester ◽

Spectral Response ◽

Optimization Methods ◽

Human Motion ◽

Optimal Number ◽

Experimental Results ◽

Halbach Array ◽

Element Simulation ◽

Optimisation Methods ◽

Two Degree Of Freedom

A two Degree-of-Freedom (2DoF) nonlinear electromagnetic energy harvester, which employs velocity amplification, with a volume of 26.7cm 3 and 25.6 cm3 (25.5mm diameter and 52.4mm height) is investigated in this work. These dimensions are very close to those of a C-battery (26.2mm diameter and 50mm length, for a volume of 27.8cm3), making the harvester suitable to be integrated in electronic devices. The harvester consists of a Halbach array of magnets oscillating inside a set of seven coils. The use of magnetic springs and the impacts between the two masses, leads to nonlinear harvester behaviour, broadening the harvester’s spectral response. Moreover, the impacts exploit velocity amplification on the secondary (smaller) mass, improving the electromagnetic conversion. The aim of this work is to optimize the performance of the electromagnetic transducer through analytical and numerical methods and to experimentally verify the optimization methods. This paper discusses the magnetic configuration that maximizes the variation of flux density and an analytical model is presented that predicts the optimal number of turns and wire diameter for the coils. A finite element simulation takes the output from the initial optimization calculations and predicts the output voltage of the harvester. Experimental results are then presented where various coil designs are tested and comparisons are made to the numerical results to validate the models. The experimental results also show a high volumetric Figure of Merit (FoMV), which highlights the benefits of the optimisation methods used. Finally, in order to give the reader an understanding of the system performance under real-world vibrations, the system was tested under excitation generated by human motion.

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Modeling and Simulation Analysis of a Two-degree-of-Freedom Nonlinear Piezoelectric Energy Harvester

IOP Conference Series Materials Science and Engineering ◽

10.1088/1757-899x/649/1/012004 ◽

2019 ◽

Vol 649 ◽

pp. 012004

Author(s):

Junxiang Jiang ◽

Shaogang Liu ◽

Junchao Wu ◽

Lifeng Feng

Keyword(s):

Modeling And Simulation ◽

Energy Harvester ◽

Simulation Analysis ◽

Degree Of Freedom ◽

Piezoelectric Energy ◽

Two Degree Of Freedom

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A broadband flow energy harvester induced by the wake of a bluff body

10.21203/rs.3.rs-171119/v1 ◽

2021 ◽

Author(s):

Wen-An Jiang ◽

Xin-dong Ma ◽

Yong Wang ◽

Mao Liu ◽

Li-qun Chen ◽

...

Keyword(s):

Bluff Body ◽

Permanent Magnets ◽

Energy Harvester ◽

Analytical Data ◽

Degree Of Freedom ◽

Nonlinear Flow ◽

Physical Parameters ◽

Restoring Force ◽

Flow Energy ◽

Two Degree Of Freedom

Abstract Wake galloping energy harvesting have been extensively developed to scavenge flow energy from vortex-induced oscillations. Hence, the wake-galloping harvester only has a natural frequency which leads to a very narrow bandwidth. Therefore, it does not operate well under the wide region of shedding frequencies in variable wind speed. To overcome the vital issue, this paper we explored a novel two-degree-of-freedom nonlinear flow energy harvester to collect flow energy induced by the wake of a bluff body. The nonlinear restoring force is realized by using a repulsive magnetic force between two cuboid-shaped permanent magnets, and the electromechanical coupling equations is presented. Based on the method of harmonic balance, the electromechanical governing equations is decoupled, and the first order harmonic solutions are implemented. The modulation equations are established, the amplitude-frequency figures of displacement and voltage are depicted with different detuning parameters. The superiority of the presented energy harvester is contrasted with the single-degree-of-freedom linear and nonlinear cases, the results revealed that the two-degree-of-freedom nonlinear scheme can enhance the bandwidth of flow energy capture. The effect of physical parameters on the scavenged power is discussed. The accuracy and efficiency of the approximate analytical data are examined by numerical simulations.

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