Flight dynamics modeling and analysis of high aspect ratio flexible aircraft

High aspect ratio flexible aircraft may assume large elastic deformation during flight, which has a great influence on the characteristics of flight dynamics. The conventional dynamic model of rigid aircraft is not applicable in this case, and it is necessary to develop a multidisciplinary model for high aspect ratio flexible aircraft. The dynamic model of the aircraft is constructed by combining the fully geometrically-exact model of nonlinear flexible beams and the quasi-steady aerodynamic model in this paper. The finite element method is used for system discretization, and the flight dynamics of the aircraft are modeled by using Lagrange equations. The constructed model reflects the comprehensive multidisciplinary characteristics, including the aerodynamics, the dynamics of telescopic deformation coupling with longitudinal bending deformation, and the dynamics of the six degrees of freedom rigid body. The dynamic stability, the time-domain responses and the coupling effects of the stretch/bending flexibility on the dynamics of the high aspect ratio flexible aircraft are investigated. The analysis results indicate that when the payload increases, the wing bending deformation becomes larger, and the effective lift losses much more seriously. In addition, when the payload reaches a certain value, the dynamics of the flexible aircraft becomes unstable, which may cause the damage of the wing structure. Meanwhile, the number of finite elements considering accuracy and calculation speed is also meaningful.

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