Optimal Design and Analysis of Axial Gradient Buffer Structure Based on 2-DOF Flexible Hinge

Conventional unmanned aerial vehicle (UAV) landing gears exhibit deficiencies including severe stress concentration, insufficient cushioning deformation capacity, and inadequate fatigue resistance during the landing impact process, which makes it difficult for them to meet the technical requirements of high-overload buffering conditions. Based on the elastic mechanics theory of the cantilever beam and using a two-degree-of-freedom (2-DOF) flexible hinge as the base, an analytical equation for the rotational stiffness of a 2-DOF flexible hinge in the direction was established. By combining the response surface methodology (RSM), the influence laws of key geometric parameters on the mechanical performance of the hinge were systematically analyzed. The optimal value range of the core structural parameters of this 2-DOF flexible hinge was determined as follows: the radius of the rounded corner R = 2.5 - 3.5 mm, the minimum thickness t = 1.5 - 2 mm, and the width a = 20 - 30 mm. Building on this foundation, an axial gradient columnar buffering structure incorporated with flexible hinges is proposed for the application of UAV landing buffering. Cross-verification between theoretical analysis and finite element simulation shows that the relative errors of structural deformation in each loading direction are merely 1.76% and 1.9%, respectively, which validates the accuracy and reliability of the proposed theoretical model. Parametric studies incorporating transient dynamic analyses under impact loading conditions elucidate that the maximal deflection and peak stress characteristics of the flexible hinge are positively correlated with the drop height and the structural connection angle. The outcomes of this research contribute a foundational theoretical framework and actionable technical support for facilitating the lightweight design and performance enhancement of flexible landing gears within high-load buffering systems of UAV.