Damage-Mitigating Control For The Flutter Of Hypersonic Flight Vehicle Airfoil

As a kind of vehicle with traveling at speeds exceeding 5 times the speed of sound,the hypersonic flight vehicle faces more complex aerodynamics problems during flight.Airfoil as a crucial component contributing most of the lift to the aircraft is one of the main aerodynamic problems for hypersonic flight vehicles.However,once airfoil flutter occurs,if it is not effectively controlled,the load on the airfoil and the flight dynamics also change,then the changed flight dynamics further aggravate the airfoil flutter,even threaten flight safety.Therefore,accurate airfoil flutter motion model,fast and effective airfoil flutter controller,as well as accurate flutter damage estimation model for estimating the airfoil flutter damage timely,mitigating damage of airfoil effectively and improving the reliability of airfoil components is of great significance.In this paper,based on the airfoil flutter motion model and the longitudinal model of hypersonic flight vehicles,the characteristics of airfoil flutter considering flight dynamics are studied,and the damage model is established to estimate the damage of airfoil flutter.Then,effective controllers are designed to control and mitigate the damage of airfoil flutter.The main contents of the paper are as follows:Firstly,the two-degree-of-freedom airfoil flutter model is established based on the Lagrangian equation,and the third-order piston theory is employed to calculate the unsteady aerodynamic force on the upper and lower surfaces of the airfoil during flutter.The longitudinal short-period model of hypersonic flight vehicle is integrated into the airfoil flutter motion model by a coupling equation.The characteristics of airfoil flutter with consideration of flight dynamics and the traditional flutter model are compared.Secondly,based on the stress-strain model,strain-life model and Miner damage theory,a linear damage model is established.And then based on the nonlinear characteristics of the crack growth fatigue damage model,a time-based nonlinear dynamic damage model is established to estimate the damage of airfoil,in which the current damage of the airfoil components is taken into accounts.Damage comparative simulations are conducted to show the damage evolution of airfoil flutter motion.Then,through the analysis of the airfoil flutter damage and considering the adverse effects of the airfoil flutter,the predictive controller is designed to control the airfoil flutter and mitigate the damage of airfoil based on the predictive control theory related.Subsequently,a more accurate three-degree-of-freedom airfoil flutter motion model considering the airfoil control surface is established based on the two-degree-of-freedom airfoil flutter model.The predictive controller is designed to control the three-degree-of-freedom airfoil flutter,and the damage of airfoil is analized.Then,the integral predictive control and adaptive period integral predicitive control is designed to control the airfoil flutter motion system with disturbance.Finally,based on the linear damage model,the influence of damage on the airfoil flutter motion is studied.Then,the damage is be regarded as the disturbance of system,and the robust predictive controller is designed to mitigate the damage of three-degree-of-freedom airfoil flutter motion.The flutter responses and damage evolution of the airfoil flutter with disturbance under predictive control,robust predictive control,and adaptive robust predictive controller are compared and analyzed.