압전 바이몰프 진동자의 형태에 따른 전기 음향특성 해석

Abstract

Abstract

The piezoelectric bimorph and multi-morph has been used in industrial fields widely. The shape of piezoelectric bimorph has been changed to improve its characteristics. However, it is hard to find the theoretical analyses for the non-rectangular type bimorph such as triangular and trapezoidal because the equation of motion with nonlinear differential equation is not easy to solve. In order to solve this problem, in this paper, the characteristic changes by the shape change of bimorph and multi-morph is analyzed theoretically. For the tapered piezoelectric bimorph and multi-morph actuators, we introduced an exponential function of length to the width of the actuators. The vibrating displacement and input admittance were analyzed for the exponentially tapered piezoelectric actuators theoretically. To confirm the theory suggested in this paper, several exponentially tapered piezoelectric bimorph and multi-morph actuators are fabricated. The experimental results agree well with the theoretical ones. As the results, when the wide end of the actuator is b, and the short end is a, the resonant frequency is proportional to the value of b/a in case of fixed b whereas the resonant frequency is inversely proportional to the b/a value in case of fixed a. In the b fixed case, the vibrating displacement at the free end is increased by the b/a value. We also confirmed that the more the number of layer on multi-morph is, the higher the resonant frequency is. From the results, the validity of the suggested analysis method could be confirmed. Using this method, the piezoelectric actuators with tapered shape could be designed appropriately.