Dynamic Modeling And Aerodynamic Characteristics Analysis Of Catapulted Extended-range UAV

With the continuous progress of science and technology,the catapult UAV,as a new military weapon,is gradually showing its great potential in military operations.Compared with traditional manned aircraft,catapulted UAVs have higher maneuverability and operational flexibility.It launches drones from the ground or ships into the air via catapults,and then uses advanced remote control systems to control them for various missions.The emergence of catapulted UAVs will revolutionize military operations and reshape battlefield patterns,and its high mobility,ability to adapt to complex environments and reduce the risk of casualties make the weapon an important tactical weapon.The flight performance index is one of the important standards to measure the quality of UAV,including flight height,flight speed,flight duration,range and stability.Among them,the requirements of endurance time and range are very high,and UAVs need to perform combat tasks in the air for a long time and long distance to meet military needs.In this paper,a new range extension scheme of the catapult UAV is proposed,which not only analyzes its flight height,flight speed and stability,but also puts forward some methods to increase its flight duration and range.This paper mainly studies the multi-platform ejection process,dynamic response analysis,aerodynamic modeling,unsteady aerodynamic characteristics analysis,aeroelastic characteristics analysis,extended range technology and so on.The main work and achievements of this paper are as follows:Firstly,different ejection modes and corresponding motion processes of UAVs are introduced.On this basis,combined with launch dynamics theory,a dynamic model suitable for complex dynamic analysis of launch processes on different platforms is established.Then,according to the UAV dynamic modeling and analysis method,the flexibility of the structure is constructed by using the modified Craigi-Bampton method,and the rigid-flexible coupling model is constructed by studying the motion characteristics of the flexible body.Finally,according to the actual combat environment under different temperature conditions,the dynamic analysis of the multi-rigid body system and the rigid-flexible coupling system of the sea-land-air multi-ejection platform is carried out.The motion attitude of the UAV body and the launcher during the ejection process is studied,and the influence of the flexible processing of components on the simulation results is proved by comparison.Secondly,when the UAV is ejected from the launching cylinder,the position of the center of mass and the aerodynamic force and inertial force will change when the sweep Angle of the UAV changes in a large range.The Kane method is used to accurately describe the dynamic characteristics of the UAV,and the body of the UAV is regarded as the main rigid body.Through the accurate analysis of the constraints between the sub-rigid bodies inside the UAV,a dynamic model suitable for the asymmetric tilt Angle ejector UAV is constructed.The difference of dynamic performance between symmetric and asymmetric deformation strategies during flight is studied,and the longitudinal and transverse dynamic models are simplified respectively.Furthermore,the characteristics of additional force and moment caused by the change of wing sweep Angle and the effects of these effects on the flight parameters of UAV are analyzed.The changes of additional force and torque during the turning process of UAV from low speed to high speed and from low speed to high speed are analyzed.By comparing the effect of asymmetrical deformation control strategy with that of traditional rudder surface control,the feasibility of asymmetrical deformation control of UAV attitude is verified.Then,according to the multi-rigid body model established by Kane method,the changes of the centroid and aerodynamic center of the asymmetric swept-wing UAV are studied,and the effects of the changes of centroid and aerodynamic center on the aerodynamic torque of the UAV are analyzed.Based on the dipole grid method,the aerodynamic model of time-varying multi-body system is established by Kriging agent model technology,and the global optimization of sweep Angle is based on genetic algorithm.Finally,the model of asymmetrically swept wing is modeled and modal analysis is carried out.On the basis of modal analysis,flutter analysis of UAV wing is carried out through the combination of dipole grid method and infinite surface spline interpolation method,and the flutter speed and frequency of asymmetrically swept wing are verified by dry wind tunnel test.It is proved that asymmetrically swept wings can achieve flutter suppression by variable sweep action.Finally,in order to make the UAV travel longer and stay in the air longer,a wing structure with variable bending based on the corrugated structure is designed according to the existing range extension method of the UAV.The stiffness calculation and finite element analysis of the corrugated structure are carried out,and the dynamic model of the deformed wing rib is established.A variable camber wing sample was developed and its static stiffness was tested.The aerodynamic characteristics of a variable camber wing are analyzed in three typical velocity domains:low speed,high Angle of attack,subsonic and transonic.The range and flight time of UAVs are calculated,and it is proved that the modified wing structure of UAVS can increase the flight range by 41.82%and the flight duration by 57.61%.Based on the sequence gradient-repair algorithm,the trajectory optimization of UAV range coverage is carried out.After optimization,the longitudinal range of UAV can reach 1.527×10~5m,and the range coverage under the influence of earth rotation can reach 7.896×10~9m~2.