UC Irvine

Whenever we look at nature for inspiration, it never disappoints us. Either explicitly or implicitly, the technological know-how of mankind is greatly inspired and derived from natural provenance. The field of aerodynamics is not an exception; a clear example is the recent branch of Bio-inspired flapping robots (BIFRs), alternatively Flapping Wing Micro Air Vehicles (FWMAVs). Despite its inherently complex and intriguing aerodynamics and flight mechanics, the realm of flapping flight continuously surprises us with its numerous exciting potentials. The presence of wing-wing interaction in flapping flight is an example of such potential. One particular type of this wing-wing interaction is commonly known as the ‘clapping effect’, which is the main focus of this Dissertation. The aerodynamic performance of clapping wings, in terms of mean thrust production, exceeds that of a traditional flapping mechanism with no wing-wing interaction. In order to analyze the performance of the ‘clapping effect’, four different FWMAV models were developed, varying in the extent of wing clapping, and their aerodynamic performances were assessed in terms of thrust and power consumption at different flapping frequencies. The results indicated that the clapping effect enhances aerodynamic performance in terms of thrust generation. In order to explain the observed results, a flow visualization setup was constructed to gain insight into the flow field and the underlying vortex interaction. Additionally, BIFRs experience time-periodic aerodynamic forces, which induce oscillations in the body motion around the mean trajectory. These oscillations affect the performance of two-winged and four-winged BIFRs in different ways since both robots rely on different mechanisms for thrust generation. We constructed two different experimental setups: one that allows free vibration in one direction and another that does not allow any vibration. To measure the self-induced vibration, a motion capture system was used. The four-winged robot with the clapping effect, which was already superior in thrust production in a stationary environment, was found to be even more efficient in an oscillatory environment, in contrast to its two-winged counterpart with a traditional flapping mechanism. Moreover, flow visualization unveiled the reason behind such behavior, which also lies in vortex interaction. The superiority of the clapping effect is not confined to aerodynamic performance. It was found to exploit a significantly more robust vibrational stabilization mechanism, in comparison to the two-winged model that does not enjoy wing-wing interaction; the four-winged robot possesses a stable equilibrium beyond a critical frequency.in contrast to the two-winged model, which did not exhibit a stable response at any flapping frequency in the range considered for this study. In conclusion, we found that the clapping effect leads to a significantly more efficient thrust production, allows exploitation of the self-induced vibration for further thrust augmentation, and promotes vibrational stabilization. All these benefits are utilized in a new drone concept, named the quadflapper. The quadflapper is propelled by four four-winged robots. The inherent clapping effect of these flapping robots is used to maneuver and control the quadflapper in a smooth manner.