The objective of this work was to utilize a piezoelectrically actuated lightly damped skeletal structure to resonantly drive elastic wings to generate hovering, flapping flight. The wings were aeroelastically tailored to generate lift from single degree of freedom excitation (i.e., wing twisting necessary for flight was generated by the passive dynamics of the wing interacting with the air). Experimental measurements indicated a mechanical power requirement of 250 mW per gram of lift, which is a number also independently derived and verified for 3-inch wings by Roy Kornbluh and Jim Delaurier, who were also working on a similar approach at SRI and the University of Toronto, respectively. This indicates that the piezoelectric actuator must have a power density greater than 250 mW/g in order to provide a viable device. Analytical models, together with experimental results, indicated that (polycrystalline) piezoelectric actuators are not capable of achieving the required power density when driving the type of load characterized by flapping wings. Note that they can achieve such power densities when driving loads matched to their own output impedance, but flapping wings are not a matched load. In other words, our results indicated that piezoelectrically actuated flapping flight is highly unlikely with the current state-of-the-art in polycrystalline piezoelectric actuators.
- Development of a Piezoelectrically-Actuated Mesoscale Robot Quadruped, M. Goldfarb, M. Gogola, G. Fischer, and E. Garcia, Journal of Micromechatronics, vol. 1, no. 3, 2001. PDF