Energy harvesting based on magnetostriction, for low frequency excitations

Dynamics of an energy harvesting device based on Magnetostrictive material (MSM), Metglas, subjected to low frequency base excitation is studied. The model consists of a steel based cantilever beam laminated by Metglas as a MSM throughout the length. The cantilever beam is surrounded by a pickup coil on which electrical current is induced due to the magnetic field according to Faraday's law. The governing mechanical equation of the motion in conjunction with the equation describing the output electrical circuit are discretized and numerically integrated over the time. Unlike piezoelectric based energy harvesters, the proposed model offers low frequency energy harvesting. In the absence of base excitation, a free vibration problem subjected to initial condition is studied and the temporal response is determined. Due to the conversion of mechanical energy to electrical energy throughout the output circuit, the response resembles that of a damped single degree of freedom oscillator and the equivalent non-dimensional damping coefficient is determined. The steady state output power in terms of the excitation frequency is determined and the corresponding steady state current and voltage are presented. It is concluded that the non-dimensional damping coefficient exhibits Lorenzian response in terms of the load resistance indicating the multi-factorial dependency of the power on the governing parameters.