全模颤振风洞试验三索悬挂系统多体动力学分析

全模颤振风洞试验需要通过软支撑系统模拟飞行器的自由飞行状态并调整模型姿态达到配平状态。参考NASA双索悬挂方案，提出了一种两电机驱动的三索悬挂系统，利用后方两索的同向/反向联动实现模型俯仰和滚转姿态的调整，利用弹簧刚度以及钢绳张力设计实现支撑频率要求。基于柔性多体动力学方法，建立了包括飞行器刚体模型、柔性索、滑轮、弹簧、气动力模型、伺服电机控制在内的复杂系统动力学模型，其中，利用任意拉格朗日-欧拉（ALE）变长度索单元描述钢绳，利用不约束物质坐标的索结点约束描述钢绳与滑轮相互作用，利用索结点物质输运速度约束描述伺服电机绞盘，利用飞行力学的气动力模型描述吹风下的气动力。基于该模型，通过小扰动响应辨识研究了弹簧刚度、钢绳张力、连接点位置等因素对支撑频率的影响规律，并分析了系统姿态调整能力，俯仰调整范围达到-12.5°~12.5°，滚转调整范围达到-45°~45°。采用滑轮处电位计测量的钢绳相对位移作为反馈信号，基于设计的控制律利用多体动力学求解器与Simulink对风洞吹风下的姿态调整过程进行仿真，模型达到配平状态，获得了吹风下的索拉力和伺服电机功率，为系统设计提供基础。

Multibody dynamics analysis of three-cable mount system for full-mode flutter wind tunnel test

In the full-mode flutter wind tunnel test, simulation of the free-flight condition through the soft support system and adjustment of the trimmed model attitude are necessary. This paper proposes a two-motor three-cable mount system with reference to NASA’s two-cable mount system. The pitch and roll attitude of the model are adjusted by the co/reverse moving of two rear cables, and the support frequency is required by the design of spring stiffness and cable tension. Based on the flexible multibody dynamics, the complex system dynamics model including the rigid body model, the flexible cable, pulleys, springs, the aerodynamic model and the servo-motor control is established. In this model, the flexible cable is described by Arbitrary-Lagrangian-Eulerian (ALE) variable-length cable element, the interaction between the cable and the pulley is described by cable node constraint with the unconstrained material coordinate, the servo-motor by the material transport speed constraint at the cable node, and the aerodynamic force in the wind tunnel by the aerodynamic model of flight mechanics. Based on the established dynamic model, the influence of factors such as spring stiffness, cable tension, and joint location on the frequency characteristics of the support is studied by identifying small disturbance responses, and the attitude adjustment ability of the system is analyzed, showing that the pitch range is -12.5° to 12.5° and the roll range is -45° to 45°. With the cable displacements measured by the potentiometers at the pulleys as feedback signals, the simulation of the attitude adjustment in the wind tunnel by the designed control law is conducted using the multibody dynamics solver and Simulink. As a result, the model achieves trimmed flight, and the cable tension and servo-motor power are obtained, establishing the foundation for the system design.