Experimental Study on the Wing Parameter Optimization of Flapping-Wing Aircraft Based on the Clap-and-Fling Mechanism

The design of a flapping-wing aircraft is mainly inspired by flying animals: to improve the lift and efficiency of flapping-wing aircraft, their wings, an essential part of the aircraft, mimic the configuration and geometric characteristics of flying animals. Herein, we conducted wing parameter optimization experiments by changing the wing-vein layout, aspect ratio (AR), surface area, and leading-edge-rod flexibility of a flapping-wing aircraft having four wings with double wing clap-and-fling effects. The AR and leading-edge-rod flexibility significantly influenced the lift through the aircraft's clap-and-fling effects. Analyzing the wing deformation and lift fluctuation revealed that the leading-edge-rod flexibility delayed the trailing-edge separation during clapping, resulting in a large lift at the beginning of peeling. A pentagonal wing of 155-mm wing length, 5.0 AR, a 100-mm breaking point, and an 80-mm wing-vein convergence point at the leading-edge-rod near the wing root was deemed the optimal wing design. This optimal wing design was used to build a 30 g flapping-wing aircraft for an outdoor flight test, which could fly for 6.5 min with a 4.5-g load, thus demonstrating the developed prototype's potential for autonomous flight.