| Aircraft wings are a compromise that allows the aircraft to fly at a range of flight conditions,but the performance at each condition is sub-optimal for a long time.Suppose the wing can adopt the high lift shape with slight sweep angle,extensive aspect ratio and high relative thickness in take-off and landing,and the small drag shape with large sweep angle,small aspect ratio and low relative thickness in supersonic cruise and maneuvering state,the aerodynamic performance is most optimal.In this case,the aircraft can expand the flight envelope,adapt to complex flight environments,meet different mission requirements,reduce energy consumption and improve flight efficiency.To improve flight efficiency and multi-mission adaptability of the aircraft,a morphing wing framework for both high and low speed conditions is designed,and the position optimization of distributed drivers inside the morphing wing are studied.The aerodynamic and mechanical characteristics of the morphing wing in different states were analyzed by simulation,and the influence of different actuator number arrangement on the structure was analyzed emphatically.Finally,a prototype was developed and the mechanical experiment was carried out.The structural deformation of the rotating and shear swept wings is analyzed,based on a wing rib swing mechanism,a parallel linkage morphing wing mechanism with variable chord length,variable sweep,variable area,and variable aspect ratio was designed.Taking element size as the parameter,the aspect ratio and degree of wing rib swing were analyzed to obtain the variation curve of wing parameters.The driver modeling of the morphing wing structure with wide velocity domain is carried out,a structure unit that contains the wing skeleton,actuator and flexible skin was chosen as the research object.Equivalent spring stiffness of the flexible skin was measured by an experimental method.Based on the principle of virtual work,a quasi-static mechanical analysis method was adopted to obtain the mechanical model of structure unit.Taking the deformation of the unit as the objective optimization function,the optimal driver position and the initial state of the skin were obtained through the Matlab Optimization toolbox fmincon function,and the experimental verification was carried out.Considering the aerodynamic force of the morphing wing,the force transmission analysis of the morphing wing skeleton is carried out,and the stress characteristics are obtained.The Xflr5 aerodynamic analysis software was used to numerically simulate the different states of morphing wing,and the pressure distribution coefficient and aerodynamic characteristics under each state were obtained.When flying at low speed,the small sweep angle and large aspect ratio increased the lift and lift-drag ratio significantly,and the take-off,landing and cruise performance improved significantly.When flying at high speed,the large sweep angle and small aspect ratio brought smaller resistance.The mechanical characteristics of the morphing wing with centralized and distributed driving at different sweep angles are analyzed.The results show that the centralized drive has little effect on the stiffness of the wing.Under the distributed drive,the stiffness of the morphing wing is related to the sweep angle and the layout of the drive.When the distributed drive is located at the tip of the wing,the maximum deformation is generated,and when the fully distributed drive is adopted,the deformation is the smallest.When the number of drives is limited,the deformation of strong distributed drive is smaller than that of weak distributed drive.Therefore,the distributed drive will maximize the wing stiffness,which is more suitable for low structural stiffness wings.The structural design of the morphing wing prototype is carried out,and the machining and assembly are completed.The morphing wing prototype can realize smooth and continuous deformation under centralized drive.The structural stiffness of the morphing wing under different sweep angles is tested... |
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