Nested-LET柔性铰链设计与性能分析

针对平面折展机构中柔性铰链在承受拉压载荷时变形大、转动精度差等问题,基于外LET铰链和嵌套结构的方法,提出了一种Nested-LET柔性铰链。设计了该铰链的结构,利用等效弹簧模型推导了其弯曲及拉压等效刚度计算公式并给出了修正系数。通过设计实例的理论计算和仿真分析,验证了理论分析的正确性和设计的可行性。比较了相同尺寸的Nested-LET与外LET铰链的弯曲性能与抗拉性能,结果表明,Nested-LET铰链弯曲刚度增加了1.5倍,拉压刚度提升了30倍,且转动中心漂移量有所下降。最后,通过拉伸实验验证了分析的正确性。

Design and Performance Analysis of Nested-LET Flexure Hinge

Flexibility and accuracy are two key factors that determine the performance of compliant joints, and also directly affect the application of compliant mechanisms. In fact, the two factors are mutually restricted. In order to improve the axial stiffness and rotation accuracy while maintaining good bending performance of joints in lamina emergent mechanisms (LEMs), a new type compliant joint based on the structure of lamina emergent torsional (LET) joint was proposed, and its structure was designed, named as Nested-LET. The close-form model of the Nested-LET was given, and the equivalent stiffness of bending and tensile-compressive was derived. The modified coefficients were presented to optimize the results, respectively. Comparing the result of theoretical calculation with finite element analysis (FEA), the theoretical formulas and modified coefficients were verified. Comparisons between the Nested-LET and outside LET joints with the same overall dimensions were made. The FEA results showed that bending stiffness of Nested-LET joint was 1.5 times larger, but tensile compressive stiffness was increased by 30 times, and center shift was reduced by 13%. Two corresponding joints were made of beryllium bronze material. Through the anti tensile test, it can be concluded that the FEA results were in good agreement with the experimental results. The Nested-LET joint improved accuracy of the joint, and it can be used in the design of high precision compliant joint.