The effect of periodic magnetic force on a piezoelectric energy harvester

The response of a piezoelectric (PZT) harvester in pendulum shape is explored under a periodic magnetic field both theoretically and experimentally. The magnetic force F-m is found via fitting to a polynomial function including the third order of amplitude after the evaluation of magnetic simulations. F-m term dominates the dynamics of the piezoelectric (PZT) harvester with a certain frequency omega(m) and the excitation amplitude U-m. A clear softening effect is observed as function of excitation frequency. Besides, the output power estimation is in good agreement with the experimental results. While the amplitude changes sinusoidal, velocity of the pendulum tip especially includes a number of different high frequency components with growing amplitudes. The periodic excitation causes ripples at the maximal and minimal values of velocity. Excitation frequency omega(m) which differs from the natural frequency coo causes much complex velocity data with high frequency components. The averaged power P = 79 mu W can be obtained and power increases dramatically when the harvester is excited at the natural frequency. (C) 2012 Elsevier B.V. All rights reserved.