The dynamic characteristics of LIPCA and its application for mimicking insect flapping motion

In this paper, we present an approach to increase flapping frequency of a previously developed flapper actuated by lightweight piezo-composite actuator (LIPCA). This is an effort to mimic the flapping motion of Allomyrina Dichotoma of which flapping frequency is typically 30 Hz. For this purpose, the dynamic characteristic of the LIPCA and the parameter study of a four-bar linkage have been conducted. From the finite element analysis and experiment, it was found that the first resonant frequency of the LIPCA in a simply supported configuration is about 80 Hz. When a dummy mass of 50 grams is attached at the center of the LIPCA, the first resonant frequency is dropped to about 20 Hz, which is still higher than the optimal frequency of the previous flapper. This means that a particular geometry of the four-bar linkage system, which was used to amplify the actuation displacement and flapping angle, might have reduced the optimal flapping frequency. Therefore, the topology of the linkage system was examined for the amplification of rotation angle and the moment transfer efficiency. In a parametric study, it was found that a carefully chosen combination of linkage lengths may provide a higher flapping frequency while the flapping angle is not seriously reduced. A new four-bar linkage system was fabricated based on the result and tested to verify the possibility. The optimal flapping frequency of the new flapper was measured to be about 18 Hz, which is about 100% increase compared to that of the previous flapper.