Research On Sliding Mode Control Of Wing Aeroelastic Systems

In the design of aircraft structures,designers usually choose to increase the structural stiffness to avoid aeroelastic problems,but it will lead to an increase in structural weight,which affects the overall performance of the aircraft.The advent of active aeroelastic wing(AAW)technology has brought new design concepts to the design of aircraft.It uses modern control technology to drive the deflection of the control surface and actively change the airflow load distribution on the surface of the wing,thus changing the stability of the system.The active aeroelastic wing technology can make the aircraft reduce the weight of the wing structure,reduce the aerodynamic damping,and expand the flight envelope,which will become a key technology in the future aviation technology.Active aeroelastic wing technology is a multi-disciplinary,multi-domain intersection and fusion technology,involving aerodynamics,structural mechanics,vibration mechanics,nonlinear dynamics,system identification,optimization,modern control theory,artificial intelligence and other related disciplines.Obviously,aerodynamic modeling?predicting and control technology are two of the most important technologies.The accuracy of aerodynamics is directly related to the accuracy of the system model.The modeling and prediction of aerodynamics has been greatly developed in the past few decades,and has achieved fruitful research results.A good control system not only could deal with high nonlinear and even under-actuated aeroelastic model of the wing,but also has the ability to maintain the stability of the system in response to uncertain models,external disturbances,and unmeasurable conditions(sensor failure).Although control technology has made a lot of progress in the field of active aeroelasticity,and the design of aeroelastic active control law has become a hot issue of current research,but relative to aerodynamics,development is still relatively slow,there are still some research deficiencies,for example,no considering the unmeasurable system states,the state output time delay problem is not considered,and factors such as inaccurate modeling and uncertainty are not considered.In this paper,the two-degree-of-freedom wing model with the trailing edge control surface is taken as the research object,and the active control method of the aeroelastic system of the wing in subsonic flight region is studied.The academic contributions of this article are as follows:1.For the single-degree-of-freedom Duffing system,the chaos and bifurcation behavior induced by levy noise are studied.The adaptive fuzzy sliding mode control method is proposed to suppress the nonlinear response,and the stochastic stability proof is given.2.For the quasi-stationary aeroelastic system with gust disturbance,assuming that the system states are unmeasurable,a sliding mode observer is designed to estimate the unmeasurable state and gust disturbance,and a sliding mode surface is constructed in the estimation space,and a new arrival law is proposed.In order to suppress the chattering in the traditional sliding mode control method and realize the finite time reachability of the sliding surface,based on the linear matrix inequality,the sufficient conditions for the asymptotic stability of the closed-loop system are derived.3.The neural network observer and sliding mode controller design for unsteady aerodynamics and structural cubic nonlinear wing flutter are studied.First,a wing aeroelastic model in state space form is established.Secondly,the neural network observer is designed to estimate the unmeasured state and nonlinear part of the system,and the sliding mode surface based on the state observer is constructed.The observer-based sliding mode controller is designed and sufficient conditions are derived to ensure the asymptotical stable.4.The design of sliding mode controller for unsteady aeroelastic systems considering output time delay and model uncertainty is studied.First,a wing aeroelastic model with model uncertainty is established.Secondly,the observer is designed to reconstruct the system and estimate the unmeasurable states of the system.On this basis,the integral sliding mode surface is constructed in the estimation space,and the sliding mode controller is designed.The sufficient conditions for the asymptotic stability of the closed-loop system are given.