ACTA AERONAUTICAET ASTRONAUTICA SINICA ›› 2020, Vol. 41 ›› Issue (9): 123761-123761.

• Fluid Mechanics and Flight Mechanics •

### Rigid body modal frequencies of two cables suspension system for full-model flutter

WU Taihuan, LIN Qi, HE Shengjie, LIU Ting, GAO Zhongxin, WANG Xiaoguang

1. School of Aerospace Engineering, Xiamen University, Xiamen 361102, China
• Received:2019-12-24 Revised:2020-01-12 Online:2020-09-15 Published:2020-09-29
• Supported by:
National Natural Science Foundation of China (11472234, 11702232); Special Funds for Basic Scientific Research Operating Expenses of Central Universities(20720180071)

Abstract: In this paper, the influencing factors of the rigid body modal frequencies of two cables suspension systems for full-model flutter tests are studied. First, based on the rope parallel mechanism theory, the static model of the two cables suspension system is built. The static stiffness model of the system is then derived by introducing the weighting matrix. Second, the undamped oscillation equation of the two cables suspension system is established to analyze the changing laws of the modal frequencies of the system rigid body. Furthermore, a ground prototype of the system is established for the system modal frequency tests to study the influencing factors of the rigid body modal frequencies of the system and their changing rules. Finally, the above mathematical model is modified with reference to the experimental results. The results show that with the increase of the rope pretension force, the rigid body modal frequency of the system shows an upward trend, while the natural frequency at each order of the rigid body mode rises at different rates, with that of the translational mode being much less affected by the rope pretension force than that of the rotating mode, and that of the rolling mode being the largest and rising fast. In the translational mode, the natural frequency of the heave mode is larger than that of the lateral mode The positional relationship between the pulley and the mass center of the aircraft model affects the rate at which the natural frequencies of the support system pitch mode and yaw mode increase with the rope pretension force, though with different degrees of influence, while having almost no effect on the natural frequency of the rolling mode. The study has found that by controlling the pretension force of the suspension ropes and properly designing the installation positions of the pulleys on the fuselage, the rigid body modal frequencies of the two cables suspension system can be effectively reduced. Therefore, the results are instructive for the optimal design of the two cables suspension system.

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