Study on flexible flapping wings with three dimensional asymmetric passive deformation in a flapping cycle

In order to further improve the efficiency of flapping wings, inspired by bird flight, a new compliant joint structure is proposed, which is easy to manufacture. The joint has the capacity of passive bending, twisting and sweeping under the aerodynamic effect of the flapping wing. A multi-objective optimization program for the compliant joint is developed, which is combined with the measured joint load. The optimized compliant joint has the effect of asymmetric passive deformation in a flapping cycle. The model wings with compliant joints are studied in the windless flapping experiment, wind tunnel experiment and free flight test. The experimental results show that the model wings have a significant advantage of power consumption compared with the original wings, and also have an advantage in the aerodynamic performance at low flight velocity and low angle of attack. (C) 2020 Elsevier Masson SAS. All rights reserved.