Focusing on the aeroelastic stability of thin panel structure of airframe component such as engine nozzle of high-speed flight vehicles,a nonlinear aeroelastic model for a two-dimensional heated panel exposing both surfaces to the airflow with different aerodynamic pressures is established.The von Karman large deflection plate theory and the first-order piston theory are used in the formulation of aeroelastic motion.The critical conditions for aeroelastic stability and the stability boundaries are obtained using theoretical analysis and numerical computations,respectively.The results show that the panel is more prone to become unstable when its two surfaces are subject to aerodynamic loading simultaneously;only if the sum of the aerodynamic pressures on both surfaces of the panel satisfies flutter stability condition,can the panel be likely aeroelastically stable;compared with the general panel flutter problem that only one surface is exposed to the airflows,the present condition makes the panel become aeroelastically unstable at relatively small flight aerodynamic pressure.
Due to the dynamical character of electromagnetic exciter and the coupling between structure and exciter(s),the actual output force acting on the structure is usually not equal to the exact value that is supposed to be,especially when multi-exciters are used as actuators to precisely actuate large flexible structure.It is necessary to consider these effects to ensure the force generated by each exciter is the same as required.In this paper,a robust control method is proposed for the multi-input and multi-output(MIMO)structural vibration control system to trace the target actuating force of each exciter.A special signal is designed and put into the coupled mul-ti-exciter-structure system,and the input and output signals of the system are used to build a dynamic model involving both the dynamical characters of the exciters and the structure using the subspace identification method.Considering the uncertainty factors of the multi-exciter/structure system,an H-infinity robust controller is designed to decouple the coupling between structure and exciters based on the identified system model.A MIMO vibration control system combined with a flexible plate and three electromagnetic exciters is adopted to demonstrate the proposed method,both numerical simulation and model experiments showing that the output force of each exciter can trace its target force accurately within the requested frequency band.
