Performance Analysis of an Electromagnetically Coupled Piezoelectric Energy Scavenger

The deliberate introduction of nonlinearities is widely used as an effective technique for the bandwidth broadening of conventional linear energy harvesting devices. This approach not only results in a more uniform behavior of the output power within a wider frequency band through bending the resonance response, but also contributes to energy harvesting from low-frequency excitations by activation of superharmonic resonances. This article investigates the nonlinear dynamics of a monostable piezoelectric harvester under a self-powered electromagnetic actuation. To this end, the governing nonlinear partial differential equations of the proposed harvester are order-reduced and solved by means of the perturbation method of multiple scales. The results indicate that, according to the excitation amplitude and load resistance, different responses can be distinguished at the primary resonance. The system behavior may involve the traditional bending of response curves, Hopf bifurcations, and instability regions. Furthermore, an order-two superharmonic resonance is observed, which is activated at lower excitations in comparison to order-three conventional resonances of the Duffing-type resonator. This secondary resonance makes it possible to extract considerable amounts of power at fractions of natural frequency, which is very beneficial in micro-electro-mechanical systems (MEMS)-based harvesters with generally high resonance frequencies. The extracted power in both primary and superharmonic resonances are analytically calculated, then verified by a numerical solution where a good agreement is observed between the results

Flexural modes coupling in cantilever-type piezoelectric energy harvesters

The ability to harness the waste mechanical energy and convert it into useful electrical power has made kinetic energy harvesters a promising candidate to provide an everlasting energy source for wireless autonomous devices. Nonlinearities, whether introduced deliberately for the sake of bandwidth broadening or present intrinsically, can highly influence the dynamic response and output power behavior of these type of energy scavengers. This paper aims to investigate the effect of nonlinearity on multi-mode vibrational response of a harvester composed of a cantilevered piezoelectric composite beam with an attached mass of finite dimensions. To that end, first of all a 3-DoF lumped parameter coupled electromechanical model of the device is developed through a comprehensive mathematical approach and its mode shapes and natural frequencies are calculated. The perturbation method of multiple scales is then applied to obtain the steady state solutions to the extracted order-reduced governing equations of the system. Results indicate that a harvester with a cubic attached mass exhibits a simple Duffing-type resonance as the excitation frequency falls in the vicinity of each natural frequency. That occurs while for a U-shaped mass the vibration modes would be coupled through occurrence of an internal resonance. In this latter case, both flexural modes of the piezoelectric beam are stimulated by a single frequency excitation and contribute to the power generation leading to an enhancement of the total output power which is the major advantage of the proposed design in this paper compared to the other existing energy harvesters. The frequency response curves of the output power are found to be composed of four branches and include Hopf bifurcations and instability regions. To verify the results obtained from the analytical approach, they are compared to a numerical solution where a good agreement is observed between them

Nonlinear energy harvesting from vibratory disc-shaped piezoelectric laminates

Implementing resonators with geometrical nonlinearities in vibrational energy harvesting systems leads to considerable enhancement of their operational bandwidths. This advantage of nonlinear devices in comparison to their linear counterparts is much more obvious especially at small-scale where transition to nonlinear regime of vibration occurs at moderately small amplitudes of the base excitation. In this paper the nonlinear behavior of a disc-shaped piezoelectric laminated harvester considering midplane-stretching effect is investigated. Extended Hamilton’s principle is exploited to extract electromechanically coupled governing partial differential equations of the system. The equations are firstly order-reduced and then analytically solved implementing perturbation method of multiple scales. A nonlinear finite element method (FEM) simulation of the system is performed additionally for the purpose of verification which shows agreement with the analytical solution to a large extent. The frequency response of the output power at primary resonance of the harvester is calculated to investigate the effect of nonlinearity on the system performance. Effect of various parameters including mechanical quality factor, external load impedance and base excitation amplitude on the behavior of the system are studied. Findings indicate that in the nonlinear regime both output power and operational bandwidth of the harvester will be enhanced by increasing the mechanical quality factor which can be considered as a significant advantage in comparison to linear harvesters in which these two factors vary in opposite ways as quality factor is changed

Mathematical Model and Experimental Design of Nanocomposite Proximity Sensors

A mathematical model of fringe capacitance for a nano-based proximity sensor, which takes the presence of different resistivities into account, is developed. An analytical solution obtained for a rectangular-shape sensor with applying of Gauss, Conversation of Charge and Ohm laws into Laplace's equation ∇2V (x, y, z, t) = 0 gives the electric potential distribution by which the fringe capacitance in a 2D domain area can be calculated. The calculated capacitance evidently decreases drastically due to the fringe phenomena while object moves toward the polymeric sensor. The model also asserts that the change of capacitance is under a noticeable influence of sensor resistivity, particularly in the range of 103-105Ω.m, the initial capacitance varies from 0.045pF to 0.024 pF. The fabricated flexible nanocomposite sensors, Thermoplastic Polyurethane (TPU) reinforced by 1wt.% Carbon Nanotubes (CNTs) having resistivity 105Ω.m, are capable of detecting presence of an external object in a wide range of distance and indicating remarkable correlation with the mathematical solution. Our proximity sensor fabrication is straightforward and relatively simple. An unprecedented detection range of measurement reveals promising ability of this proximity sensor in applications of motion analysis and healthcare systems

Analytical and numerical simulations of energy harvesting using MEMS devices operating in nonlinear regime

While macro-scale piezoelectric generators require base excitations with moderately large amplitudes to transit from the linear regime of vibration to the nonlinear one, for a MEMS harvester due to its small dimensions, this transition can occur at oscillatory base motions even smaller than a few microns, which necessitates the nonlinear analysis of MEMS harvesting devices in most environments. In this paper the coupled electromechanical behavior of a typical MEMS-based piezoelectric harvester in the nonlinear regime is investigated. Lagrange’s equations are used in accordance to the assumed mode method to extract the coupled nonlinear equations of motion governing the lateral deflection and output voltage. An analytical solution to the derived equations is performed employing the perturbation method of multiple scales providing the nonlinear frequency responses of the output power. Results indicate that although the effect of nonlinear inertia increases due to utilizing large tip masses in these harvesters, nonlinear curvature is still the dominant effect leading to hardening behavior of the response. The comparison of the responses of the nonlinear and linear devices shows a considerable enhancement of the frequency bandwidth in the nonlinear regime. Also a nonlinear coupled electromechanical FE simulation of the harvester is conducted using the ABAQUS software where a very good agreement is observed between the results of this simulation with both analytical and numerical solutions of the governing equations

Detecting Single Microwave Photons with NV Centers in Diamond

We propose a scheme for detecting single microwave photons using dipole-induced transparency (DIT) in an optical cavity resonantly coupled to a spin-selective transition of a negatively charged nitrogen-vacancy (NV−) defect in diamond crystal lattices. In this scheme, the microwave photons control the interaction of the optical cavity with the NV− center by addressing the spin state of the defect. The spin, in turn, is measured with high fidelity by counting the number of reflected photons when the cavity is probed by resonant laser light. To evaluate the performance of the proposed scheme, we derive the governing master equation and solve it through both direct integration and the Monte Carlo approach. Using these numerical simulations, we then investigate the effects of different parameters on the detection performance and find their corresponding optimized values. Our results indicate that detection efficiencies approaching 90% and fidelities exceeding 90% could be achieved when using realistic optical and microwave cavity parameters

Free vibration of FG-GPLRC conical panel on elastic foundation

Present research is aimed to investigate the free vibration behavior of functionally graded (FG) nanocomposite conical panel reinforced by graphene platelets (GPLs) on the elastic foundation. Winkler-Pasternak elastic foundation surrounds the mentioned shell. For each ply, graphaene platelets are randomly oriented and uniformly dispersed in an isotropic matrix. It is assumed that the Volume fraction of GPLs reainforcement could be different from layer to layer according to a functionally graded pattern. The effective elastic modulus of the conical panel is estimated according to the modified Halpin-Tsai rule in this manuscript. Cone is modeled based on the first order shear deformation theory (FSDT). Hamilton's principle and generalized differential quadrature (GDQ) approach are also used to derive and discrete the equations of motion. Some evaluations are provided to compare the natural frequencies between current study and some experimental and theoretical investigations. After validation of the accuracy of the present formulation and method, natural frequencies and the corresponding mode shapes of FG-GPLRC conical panel are developed for different parameters such as boundary conditions, GPLs volume fraction, types of functionally graded and elastic foundation coefficients. Copyright 2020 Techno-Press, Ltd.This research is founded by the Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant number 107.99-2019.02.Scopu