Study on transient aeroelastic vibration and vehicle-mounted test for a morphing aircraft

This paper deals with the transient aeroelastic vibrations of a morphing aircraft undergoing structural transformation, both theoretically and experimentally. The framework integrates the floating frame of reference method, which accounts for large rigid-body motion with small deformations, and the unsteady vortex lattice method for aerodynamic modeling. The framework, with morphing commands introduced, leads to a set of nonlinear dynamic equations with kinematic constraints for the morphing aircraft. These equations enable the analysis of transient dynamic responses in the time domain. Numerical results indicate that the rigid-elastic coupling effect remains weak under aerodynamic forces. However, during the morphing process, the time-frequency spectrum of vibration of the aircraft exhibits significant complexity. During the morphing process, the aerodynamic forces induce new vibration forms that differ from the natural modes predicted by using modal analysis based on the finite element model. The vibration frequency undergoes substantial variation over time, with energy transfer occurring between different frequency bands. When the flow speed exceeds a certain threshold, the structural vibration during the morphing process first diverges and then converges. Slight variations in morphing time or flow speed can cause significant differences in the dynamic response. The results further indicate that the aerodynamic deformation of the folding angle is smaller at larger folding angles. The paper also presents the ground tests of a morphing aircraft mounted a car to validate the time-varying modeling method. The tests show that the vibration time-frequency spectrum exhibits a mesh-like energy band consistent with the simulations, confirming that the method effectively captures the evolution of the time-dependent dynamic characteristics of the morphing aircraft.