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This paper experimentally examines a multifunctional gust alleviation system and holds promise for improving small unmanned aerial vehicles performance in wind gusts. The designed multifunctional wing spar is able to harvest energy itself from the normal vibrations during flight. If the wing experiences any strong wind gust, it will provide vibration control to maintain its stability. The proposed wing spar carries on the functions of energy harvesting, strain sensing, and gust alleviation via piezoelectric materials. A closed form electromechanical cantilever multifunctional beam model is developed, which captures the basics of piezoelectric constitute equations using Euler-Lagrange equations. An enhanced two mode reduced energy control (REC) law is developed to saturate a positive strain feedback (PSF) control law, and therefore decrease energy consumption but maintains the same gust alleviation performance. An equivalent circuit model is also developed based on the distributed parameter method to represent a multifunctional gust alleviation system using harvested energy. Experimental results show that compared to conventional PSF control law, the REC decreases voltage supply from ±20 to ±4 V, uses 76% less energy whereas maintaining the same performance. Experimental results also show that it is feasible to alleviate wind gust disturbance using harvested power from ambient vibrations, but requires the harvesting time to be 0.42 times longer than the wind gust duration.
Date of Publication: Aug. 2013