折叠变体飞行器的降阶建模与颤振分析

Model Order Reduction and Flutter Analysis of Folding Morphing Aircrafts

折叠变体飞行器可在飞行过程中调整自身气动布局以适应不同飞行条件,从而使其执行不同任务或处于不同环境时都保持在最佳性能状态,然而可变的结构与气动布局会导致折叠变体飞行器的动态特性复杂且时变。针对折叠变体飞行器的动态特性预示问题,发展一种折叠变体飞行器的一体化降阶建模与颤振分析方法,提出适用于折叠变体飞行器的整体降阶建模和颤振特性快速分析流程,以探究折叠角和扭转弹簧刚度对固有频率和颤振速度的影响规律。基于所提方法和流程的动态特性预示结果表明:各阶模态的固有频率均随扭转弹簧刚度的增大而升高,而弯曲模态和扭转模态所对应的固有频率随折叠角的变化规律不同;折叠角的变化会影响颤振速度,且当折叠角为45°时增大扭转弹簧刚度会导致出现耦合颤振的模态阶次发生转变;此外,颤振速度还会随连接位置扭转弹簧间隙值的增加而升高。

Folding morphing aircrafts can adapt their aerodynamic layout to different flight conditions during flight,thus maintaining optimal performance in different missions or environments.However,variable structural and aerodynamic layouts may lead to complex and time-varying dynamic characteristics of folding morphing aircrafts.Aiming at the problem of predicting the dynamic characteristics of folding morphing aircrafts,this paper develops a method of integrated reduced-order modeling and flutter analysis for folding morphing aircrafts,and simultaneously proposes an overall reduced-order modeling and rapid analysis process of flutter characteristics prediction for folding morphing aircrafts to investigate the effect of folding angles and torsion spring stiffnesses on the natural frequency and flutter speed.The results of the dynamic characteristics based on the proposed method and process demonstrate that natural frequencies of each order increase with the increase of the stiffness of the torsion spring,but the natural frequencies corresponding to the bending mode and torsion mode exhibit different variations with the folding angle.The change of folding angles has an impact on the flutter speed,and increasing the torsional spring stiffness when the folding angle is 45 degree causes amodalorder shift in coupled flutter.Furthermore,the flutter speed may also increase with the increase of the freeplay value of the torsion spring at the connection position.