Research On Gust Response Analysis And Alleviation Of The Flexible Aircraft

During flight, discrete gust and continuous turbulences can significantly excite the structuralvibrations, which leads to increased structural loads, produced fatigue damage and decreased ridecomfort, especially on large civil airplanes. Due to the characteristic of large ratio wing of civilairplanes, the overloads induced by discrete gust and continuous turbulences often composes of thesevere conditions.The stability of the civil airplane is analysized by using the V gmethod and g method. Underdifferent flight velocity conditions, Analyzed the contribution to flutter stability of each mode. At themean time, fourier transform method, time-domain simulation and hybrid approach are used to solvethe response of discrete gust.The overloads induced by discrete gust and continuous turbulences can be efficiently suppressedby introducing the gust load alleviation system. Today, large civil airplanes are commonly equippedwith gust load alleviation systems. This paper focuses on the gust load alleviation of a civil airplane.Firstly, based on the structural dynamic equations and the unsteady aerodynamics model, theopen-loop aeroelastic equations of an elastic airplane under gust input and the deflection of thecontrol surfaces are established. Besides, by introducing the coordinate transformation, therelationship between the rigid body modal coordinates and the motion variables defined in flightdynamics is obtained, which results in the integration equations in aeroelasticity and flight dynamics.In this paper, the ailerons and the elevators are used as control surfaces to alleviate the gustresponses. The corresponding control laws are separatedly designed for continuous and discrete gusts.Finally, according to the simulation results, the schemes of control systems are evaluated.