| The development of Micro Air Vehicle (MAV) has received great attention recently with its application in military and civil fields. It has been one of the most important areas in biomimetic research for about two decades. For a very small scale MAV with high maneuverability, the flapping wing system may be more attractive than the rotary wing and fixed wing systems.This paper investigates the nonlinear dynamic characteristics of a flapping wing MAV with click mechanism using multi-body dynamic method. Firstly, a solid model of the flapping wing MAV is established. There are two pairs of flexible hinges in the flapping wing mechanism for realizing click effect. ADAMS is used to carry out the numerical simulation. Secondly, a pseudo-rigid-body model is used to simplify the geometrically nonlinear analysis. The dynamic characteristics of the click mechanism are analyzed from several aspects, such as restoring force, flap angle, displacement response. Finally, the results of the simulation and experimental prototype, such as the restoring force and displacement response, are compared. The click effect in the flapping mechanism is discussed in details.It is found that the flapping wing mechanism is an asymmetric system, while the structure being much stiffer on the upstroke compared with the downstroke. The energy ratio of the kinetic energy to work input over one period of excitation was subsequently obtained from the numerical models. It implies that asymmetry does not degrade the performance of the MAV with click mechanism and can even offer a marginal improvement. The two pairs of flexible hinges can restore and release the energy which may increase the reverse speed of the wings around the end of the stroke. The wing stroke angle can be more than 110°, which allows a great lift of the MAV. Moreover, the experimental and numerical results compare reasonably well, meaning that the multi-body dynamic model can reasonably capture the dynamic characteristics of the asymmetric MAV structure. |
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