Formulation of Electric Voltage for Vibration Generation Device Using Magnetostriction Material

A study on vibration power generation using magnetostriction material is carried out in both experimental and theoretical sides, and the power generation voltage is formulated using an analytical formula. The damping constant is obtained from experiments, and the bending at free end is described by the equation of motion of forced oscillation using the damping constant. Power generation is achieved through the variation in the longitudinal magnetization of cantilever beam. The magnetization curve, where the magnetization is saturated at tensile stress and is approaching to zero at compressive stress, is described by using an arctangent function. By assuming that magnetoelastic energy caused by stress is equivalent to magnetic energy, the energy can be converted into an effective magnetic field by using the function. The operating point on magnetization curve is set by the shape magnetic anisotropy of cantilever beam, and the magnetization variation due to the effective magnetic field is calculated around the operating point. The calculated variation in magnetization is differentiated by time to obtain the generated voltage. The generated voltage calculated by using the formulation well explains the experimental results of the dependence of generated voltage on bias magnetic field, and the characteristics of waveform are similar to the experiments.