非線形圧電方程式を基にした振動発電素子の非線形パラメータの決定方法

抄録

We propose a method to determine nonlinear parameters of small-sized practical piezoelectric energy harvester based on harmonic balance method, considering nonlinear piezoelectricity. The previous studies discussed a cantilever beam in which the piezoelectric material covers over entire structure, no mass attached on the tip of the beam, and it is connected to a single resistive load. However, such a condition was not practical. We used a cantilever beam with piezoelectric elements attached near the fixed end only and the mass was attached on the beam's tip. Firstly, we derived the governing equation of motion for the harvester based on the third-order nonlinear piezoelectric equation proposed previously. Secondly, we will determine nonlinear parameters of governing equation by using the harmonic balance method (HBM). The equation we derived replicates two phenomena observed in real device: (1) lower shift of the resonance frequency, (2) increase in the effective electromechanical coupling coefficient depending on the excitation force. We expect that our model can reproduce the actual electromechanical characteristics by using the two way coupled analysis with the non-linear circuit, which is proposed by us.