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In recent years, energy harvesting from ambient sources in order to use for low-powered electronics has been considered by many researchers. Wind energy, solar energy, water energy, mechanical energy from vibrations, etc are common sources of ambient energy. In this paper, optimization of energy harvesting from ambient vibration using magnetic shape memory alloy is presented. To this end, a clamped-clamped beam coupled with MSMA units is considered. A shock load is applied to a proof mass which is attached to the middle of the beam. As a result of beam vibration a longitudinal strain is produced in the MSMA. This strain changes magnetic flux inside the coil connected to MSMA and as a result, an AC voltage is induced in the coil. To have a reversible strain in MSMA, a bias magnetic field is applied in the transverse direction of MSMA units. The Euler-Bernoulli model with von Kármán theory and a thermodynamics-based constitutive model are used to predict the non-linear strain and magnetic response .Finally, Faraday's law of induction is used to predict the output voltage. After obtaining the governing equations, a design optimization is performed to find the optimal shape and configuration of the energy harvester together with the effects of proof mass and bias field.

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In this paper, a thermodynamic based constitutive model used to model the behavior of magnetic shape memory alloy (MSMA) during applying strain in an energy harvester. In this type of energy harvester, applying strain changes the internal magnetization of MSMA and as a result changes the flux density around it. Using a coil the flux change can be converted to voltage. In order to study the effect of changing MSMA dimensions on the amount of harvested energy, the demagnetization factor for different dimensions derived from an analytic expression for ferromagnetic prisms and the results are validated by reference data. Increasing MSMA thickness results in increasing longitudinal demagnetization factor and decreasing transversal demagnetization factor. The constitutive model of MSMA is used in modeling an energy harvester using two different configurations; one a pickup coil turned around MSMA and second a system with ferromagnetic core to conduct magnetic flux and the pickup coil around core. Simulation of two models at different thicknesses shows that increasing thickness in system with coil around MSMA results in linear increase of voltage while this parameter in second configuration leads to a nonlinear increase of voltage. Furthermore, simulations show that increase of MSMA width, results in linear increase of output voltage in both configurations but with steepest rate for system with ferromagnetic core. Finally, increasing the length of MSMA specimen shows no changes in voltage for the system with coil around MSMA, while linear increase in voltage for the system with core is recorded.

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In this paper, Global sensitivity analysis of predicted strain from clamped–clamped beam magnetic shape memory alloy based energy harvester with PAWN method is presented. In the selected model MSMA units attached to the roots of clamped-clamped beam while coil wrapped around MSMA. A shock load is applied to a proof mass in the middle of the beam. As a result of beam vibration a longitudinal strain is produced in the MSMA and beam. There are limits to harvest energy from this model and one of them is the strain applied to the MSMA. As the strain increases with respect to the applied pre-strain, the MSMA exits the compression region and causes the model to fail. When strain exceeds limits also affect the predicted result. Thus PAWN method as an efficient and easy way for global sensitivity analysis of the inputs has been taken into account. Then the model is analyzed with introduced method to determine the effect of each input on the output. In the following, due to the importance of the harvested voltage, the sensitivity analysis and ranking of inputs are performed. Moreover, using two-sample Kolmogorov-Smirnov test it is shown that for design and optimization of model with respect to strain one can fix thickness, width and length of MSMA while studying model in corresponding maximums and minimums and also with respect to RMS voltage and similar test the width of the beam can be fixed.