Flutter Analysis And Active Flutter Suppression For Multiple Control Surfaces Of High-Aspect-Ratio Wings

In recent years,due to its wide application prospect,the high altitude long endurance unmanned aerial vehicle(UAV)has become a research hotspot in the field of aircraft design at home and abroad.The wing of this kind of aircraft generally has the structural characteristics of high aspect ratio and large flexibility,so it is easily to produce large deformation under aerodynamic load.At this time,the results obtained by linear flutter analysis theory based on the hypothesis of small deformation will not be accurate,it must be consider geometrical nonlinearities to calculate flutter velocity of this type of wing.In this paper,the linear flutter analysis of a high aspect ratio wing is carried out firstly.Based on the “incremental finite element method” and “quasi-modal” method,we write a new solving sequences in MSC.NASTRAN by DMAP language.So that the static aeroelastic deformation of the wing under aerodynamic loads can be got and the intrinsic modes of the wing at the static equilibrium position can be achieved.Based on this mode,we can get the nonlinear critical flutter velocity.The results show that the critical flutter velocity of the wing will be reduced as for the geometrical nonlinear factors.Flutter can cause catastrophic damage to the wing structure.Active flutter suppression technology can improve the aeroelastic stability of such aircraft and has gradually become the first choice of anti-flutter measures for designers.Then the active flutter suppression was studied by installing two control surfaces on the trailing edge of the wing.Firstly,the influence of additional control on wing flutter characteristics is discussed,then the aerodynamic expression in time domain is obtained by rational function fitting methods,putting the acceleration sensor at the tip of the wing,using servo motor as the actuator,an aeroservoelastic model of wing with control surface is established.Secondly open loop time domain simulation is carried out in Simulink/Matlab.Finally,two kinds of the flutter active suppression methods are discussed which are PID control and model predictive control.These two methods are applied to the active flutter suppression of high aspect ratio wing,and the simulation results show that the two control methods are effective in suppressing wing flutter.Because the model predictive control can realize the constraint of control conditions through online rolling optimization,it is better than the simple PID control.