| In order to incrase the aerodynamic efficience,pay load and fuel weight,the lightweight flexible wing with high aspect ratio often employed by High-altitude Long-endurance?HALE?Unmanned Aerial Vehicle?UAV?.However,the flexible wing may lead to more serious aeroelastic problems,even restrict the UAV performance drematically.the investigation report of the Helios Prototype aircraft mishap indicates that the main problem in the design and study procedure of that kind of UAV is the lack of reliable analysis methods and tools which can capture the coupling between the structural dynamics and flight dynamics.The development of Active Control Technology?ACT?,such as maneuver load alleviation?MLA?,gust load alleviation?GLA?and active flutter suppression?AFS?et al,reveal the new solution of the aeroelastic problems.Further more,considering the ACT in the aircraft design process can not only dig more potential of ACT but also improve the performance of aircraft.In that case,carring out the aeroservoelastic modelling and active control research,developing the multidisciplinary design optimization?MDO?method and MDO framework to perform integrated design of elaborate aerodyanmic,structrue and controller is necessary.based on the above reasons,the research works conducted in this paper are as follows:1.high and low precision matching system for static aeroelastic numerical analysis are established.The static aeroelastic problem is solved by loosely coupled iteration,plate and shell model is chosen to represent structure,the Radial Based Function?RBF?interpolation method is adoptted to transfer information between the CFD mesh and CSD mesh,the CFD mesh in the interation is regeneration by Volume Spline Interpolation?VSI?and Transfinite Interpolation?TFI?method.In the MDO process,the potential equation based on the boundary layer correction is mainly used to evaluate aerodynamic characteristics and solve static aeroelastic problem,the system beased on RANS equation is used to compare and verify the former results.2.A time-domain state-space form aeroservoelastic model is proposed.In order to perform flexible aircraft analysis and take advantage of model control theory to design controller,Peters' finite-state theory,induced-flow dynamic and ONERA dynamic stall model are implemented to model 2D nonlinear unsteady aerodynamic forces,3D wing aerodynamic forces are calculated by strip theory and 3D cross flow effect correction.Wing structural deformation is modeled by equivalent beam finite element approach,the spanwise discretization is based on the same intervals as the strip method discretization,the equivalent node forces can be calculated with the virtual work principle conveniently.The stability of the state-space form aeroservoelastic system can be obtained via root locus,and the simulation results can be obtained by explicit runge kutta method in time marching scheme.The aeroservoelastic model proposed in the paper is verified by wind-tunnel tests and reference results.3.A dynamic equation is deduced to capture the strutural dynamic and flight dynamic.The coupling equation is deduced by Largrange's equation for quasi-coordinates considering wing,fuselarge and tail are flexible,the defination of the vector of mass point is facilitated by add in component frame.Then,the dynamic equation represent rigid body along with the stuctural dynamics and the dynamic equation based on mean axes method are obtained through rigid body,not highly flexible and inertia invariant hyperthesis respectively.The simulation code is validated by comparing with reference results.4.The bifurcation phenomenon of 2D dynamic stall flutter is revealed and analysed.The numerical studies clearly shows the existence of two bifurcation phenomenons in NACA 0012 airfoils' dynamic stall flutter,one is a subcritical Limit Cycle Oscilation?LCO?and other one is coexistence of symmetrical and asymmetrical LCO.The type and reason of the bifurcation is analysed.The AFS controller is designed by static output feedback method to stabilize the LCO with bifurcation,the closed loop results shows that the flutter boundary can be incrased by 31 percent.5.The gust load alleviation and active flutter suppression controller are designed for HALE UAV.The H2 static output feedback design method is chosen to deal with the undetectable states,which is solved by linear matrix inequality?LMI?method by introduced in conservative hyperthesis,reduced order model is implemented to ensure the LMI algorithm can be utlized effectivly.The lord factor caused by 1-cos and continues turbulance gust model can be reduced about 47% and 57% respectively by GLA system.6.The balanced truncation method is improved.The initial balanced truncation model can only apply to stable system in order to solve the controllable and observerable Gramian,because the dynamic system under flutter is unstable,real Schur transformation is used to decompose the system into an interconnection of stable and unstable subsystems,the stable subsystems is balance truncated and unstable subsystems is reserved.7.The elaborate aeroservoelastic optmization design is performed for a typical HALE UAV.The aero-structure and aeroservoelastic optimization frame work which included in the active control technology are developed respectively,the wing configuration is parameterized by root and tip chord length,the coordinates of wingtip leading edge point and airfoils' twists,the airfoils along spanwise is represented by Class Function/Shape Function Transformation,the number of the aerodynamic design variable is 82.The number of the structural size variable is 121 after districting the finite element model.The CFD and CSD solver are connected with flexible aircraft dynamic model through wing plantform,twists and equivalent beam algorithm.Under the premise of keeping maximum take off weight invariant,the range and endurance of the HALE UAV are increase 4.6% by aero-structure optimization and about 8.3% by aeroservoelastic optimization,which illustrate that the idea and optimization framework proposed in the paper are effective and reliable. |
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