Research On Aeroelasticity Flutter Active Control Of Nonlinear System

The flutter problems of aeroelastic system widely exist in many engineering areas, such as aviation, civil structure and wind power generation etc. With the continuous decreases of weight and stiffness of aircraft and continuous improvement of the speed, aircraft aeroelastic flutter problems are becoming more and more prominent, the active flutter control of wing becomes a research hotspot in the optimization control of aircraft. Based on nonlinear dynamics theory and modern control theory, a study on the flutter analysis and active control of the nonlinear two-dimensional wing is carried out in this paper, the main contributions of this dissertation are as the follows:The nonlinear flutter of two-dimensional airfoil is analyzed under constant aerodynamic conditions. The aerodynamical model of airfoil flutter system is established based on Lagrange equation. Various factors which affect the flutter speed are given out and the influence of structural parameters and aerodynamic parameters on pneumatic elastic system is analyzed. The critical flutter speed and the stability of the system are obtained by using the describing function method, the Hopf bifurcation theorem and the Routh-Hurwitz criterion.Taking nonlinear two-dimensional airfoil with two control surfaces as the research object, an integral backstepping sliding mode active control method is proposed. The backstepping sliding mode control system for pneumatic elastic airfoil is designed, the stable tracking control of plunge displacement and pitch angle for aerofoil are realized, and the stability analysis of the system is carried out based on Lyapunov theory. The simulation results show that the designed control system can effectively eliminate the flutter of the aerofoil aeroelastic system, the stable tracking of the desired state is achieved and the chattering of the conventional sliding mode is weakened.In view of the uncertain problem of external disturbances for airfoil, a method of adaptive backstepping sling mode control based on system immersion and manifold invariant(I&I) for aeroelastic system is proposed. In this method, the whole adaptive law is designed based on I&I. An adaptive backstepping two order sliding mode control system based on super-twisting method is designed for pneumatic elastic airfoil, the effect of unknown external disturbance on the system is eliminated. Simulation results show that thestability of plunge displacement and pitch angle ouput for airfoil are improved based on the accuracy of I&I disturbance estimation, at the same time, the designed controller accelerates the convergence of the system states, so the stability and adaptability of the system are ensured.