Abstract
By combining the flapping and rotary motion, a bio-inspired flapping wing rotor (FWR) is a unique kinematics of motion. It can produce a significantly greater aerodynamic lift and efficiency than mimicking the insect wings in a vertical take-off and landing (VTOL). To produce the same lift, the FWR’s flapping frequency, twist angle, and self-propelling rotational speed is significantly smaller than the insect-like flapping wings and rotors. Like its opponents, however, the effect of variant flapping frequency (VFF) of a FWR, during a flapping cycle on its aerodynamic characteristics and efficiency, remains to be evaluated. A FWR model is built to carry out experimental work. To be able to vary the flapping frequency rapidly during a stroke, an ultrasonic motor (USM) is used to drive the FWR. Experiment and numerical simulation using computational fluid dynamics (CFD) are performed in a VFF range versus the usual constant flapping frequency (CFF) cases. The measured lifting forces agree very well with the CFD results. Flapping frequency in an up-stroke is smaller than a down-stroke, and the negative lift and inertia forces can be reduced significantly. The average lift of the FWR where the motion in VFF is greater than the CFF, in the same input motor power or equivalent flapping frequency. In other words, the required power for a VFF case to produce a specified lift is less than a CFF case. For this FWR model, the optimal installation angle of the wings for high lift and efficiency is found to be 30° and the Strouhal number of the VFF cases is between 0.3–0.36.
Highlights
Since the research initiation of the micro aerial vehicle (MAV) from the defense advanced research projects agency (DARPA) program [1], increasing attention has been paid to the design of bio-inspired flapping wing MAV, and in particular, the study of aerodynamics [2,3,4]
An investigation is conducted into the effect of variant flapping frequency during a flapping on the aerodynamic force generation of a flapping wing rotor driven by an ultrasonic motor (USR30)
Cycle on the aerodynamic force generation of a flapping wing rotor driven by an ultrasonic motor through experiment and computational fluid dynamics (CFD) simulation
Summary
Since the research initiation of the micro aerial vehicle (MAV) from the defense advanced research projects agency (DARPA) program [1], increasing attention has been paid to the design of bio-inspired flapping wing MAV, and in particular, the study of aerodynamics [2,3,4]. 21 g insect-like tailless flapping wing micro air vehicle (FWMAV) with proportion-differentiation (PD). By undertaking several flight tests, they demonstrated that the tailless FWMAV could perform a vertical climb, hover and loiter, within a 0.3 m ground radius, with small variations in pitch and roll body angles. By mounting a commercial infrared (IR) transmission module on the vehicle, they realized that altitude control of the FWMAV by a modified proportional feedback algorithm. The validity of their approach is demonstrated in both numerical simulations and flight tests
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