Damage Characteristics Analysis And Damage-mitigating Control For The Wing Of Hypersonic Unmanned Aircraft

As a kind of high performance aircraft,the hypersonic aircraft experiences subsonic,transonic supersonic and hypersonic speed range,and the flight altitude passes through different flow regimes,including continuous,transitional and rarefied flow,the complex aerodynamic interference and aerodynamic heat generated by extreme flight condition may result in some fatigue damage in airframe structure,and the accumulation of fatigue damage will lead to unpredictable flight disaster.However,as the main load-bearing structure,the root of wing spars need to stand the loads not only come from the self-gravity of the wing,but from the huge aerodynamic loads and heat in hypersonic flow.Therefore,as the key component of the wing,the root of wing spar has a maximum probability of generating the fatigue damage compared to other components of the aircraft.To ensure the structural reliability of the wing in entire flight envelope and extending the service life,this thesis studies the structural mechanics model and damage model of the root of wing spar,and establishes the strength reliability model.And then,by analyzing the key variables of the aircraft which have the greatest effect to the structural damage,the two methods of damage mitigating control are proposed.The main works of this thesis are given as follows:Firstly,on the basis of a generic hypersonic aircraft model and aerodynamic parameters given by NASA,force analysis for the wing spar of hypersonic aircraft is carried out,the structural mechanic model of the component is built,combine with the strength characteristics of the material,a novel reliability model of the wing spar is established based on the stress-strength interference theory and total probability theorem.Secondly,based on the hypersonic aircraft model and combine with the fatigue damage mechanism,the damage model which can express the development of fatigue damage in the root of spar is established.By analyzing the impact of aircraft variables on the aerodynamic parameters,dynamic pressure and the damage characteristics to find out the key variables which have the greatest effect to the structural damage.Thirdly,design the longitudinal and attitude flight controller of the hypersonic aircraft by using the siding-mode theory to make the aircraft variables track the command signals,simulate climb and cruise maneuver.Adopt two methods which are Reduce the Task Requires and Reduce the Performance to achieve the basic damage mitigating control,and explore the principle of damage mitigating.And then,use particle swarm optimization algorithm to seek the optimal command curves which can satisfy the best compromise conditions,by designing the command constrained curves to achieve damage mitigating control.Finally,the shortcomings of conventional sliding mode control are analyzed,and a novel sliding mode control with unidirectional auxiliary surfaces based on a fast double power reaching law is proposed to design the longitudinal and attitude flight controller.Meanwhile,the impacts of reaching law parameters on the dynamic properties of the aircraft are analyzed,and achieve the real-time damage mitigating control by feeding back the damage state to the reaching law parameters to adjust the tracking performance of controllers.