### A bioinspired flapping wing structure based on the geometry and stiffness simi-larity of dragonfly

• Received:2022-09-09 Revised:2023-01-09 Online:2023-01-18 Published:2023-01-18

Abstract: At present, the research on flapping wing and flapping wing rotor micro aerial vehicles is mainly focused on the flapping mechanism design to mimic the insect wing motion and the aerodynamic characteristics. The research on insect wings is mainly focused on the biological composition in micro scale, the material and mechanical characteristics. The principal component analysis method is used to establish the relationship between the spanwise bending stiffness and the geo-metric parameters of the insect wings. Take dragonfly wing as example, a bionic flapping wing can be designed based on geometric similarity. Based on mechanical test, the spanwise bending stiffness of dragonfly wings can be measured to establish a stiffness similarity law. The flapping wing structure can be optimized by using the similarity law as a design constraint. Three types of flapping wings were designed and made as test samples. One is in the usual rectangular shape (JX-wing) based on the stiffness similarity only; another is a dragonfly-like flapping wing (JH-wing) based on geo-metric similarity only; the third type is an improved dragonfly-like flapping wing (GD-wing) based on both geometric simi-larity and stiffness similarity law. Take a flapping wing rotor model as a test platform, experiment work is carried out to measure and compare the lifting forces of the three types of flapping wings in a range of flapping frequency 5-15Hz. The test results show that the lift of the GD-wing is 25% larger than rectangular JX-wing at 12.5Hz flapping frequency. The lift of the GD-wing is close to the JH-wing when the flapping frequency is below 6.5Hz, but becomes at least twice larger than the JH-wing when the flapping frequency is above 8Hz. The flapping wing structure design method based on both geometric similarity and stiffness similarity provides a pass-way for flapping wing and flapping wing rotor of high lift and efficiency.

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