| Popis: |
In this paper a non-linear model for a two degree-of-freedom (2Dof) vibrational energy harvester is presented, together with its experimental validation. The device consists of two masses relatively oscillating one inside the other. The inner (lighter) mass comprises five NdFeB magnets, assembled in a Halbach configuration. The outer (heavier) mass is made of seven coils. Magnetic springs act on both the outer and the inner masses and enable momentum to be transferred from the heavier to the lighter mass, amplifying the velocity of the latter. In this way, an efficient kinetic o electrical energy conversion is achieved from small vibrations, using electromagnetic conversion, which is strongly affected by the relative velocity of the two masses. A finite element model is presented in order to simulate the magnetic field produced by the Halbach stack and the force of the springs as a function of the cap height. The results are then integrated in a numerical model built in Matlab, in order to study the electrical optimization of the harvester. Specifically, the number of turns of the coils is varied to maximize the power output produced at resonance. Finally, the same model is used with exponentially correlated noise as the input, and the effect of lowering the cap is investigated in detail. Experimental data are compared to the simulation results, demonstrating the effectiveness of the model. |
