Abstract: 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.

Key words: full-mode flutter, wind tunnel test, cable mount system, flexible multibody dynamics, aeroelasticity, feedback control