Research On Design And Control Of Catapult Launched Tandem-wing Flying Robot With Variable Sweep

The catapult launched folding wing flying robot has the integrated functions of cruise,reconnaissance and strike,but the folding scheme inevitably complicates the aircraft structure,limiting the effectiveness of the control surfaces.Morphing technologies can not only change the aerodynamic characteristics of the aircraft to adapt to complex and changeable mission environments,but also improve the control efficiency and maneuverability of the aircraft.This subject proposes a novel small size catapult launched tandem-wing flying robot with variable sweep,combining with the technologies of variable sweep and catapult launched folding wing aircraft.The novel flying robot has four variable airfoils,and the innovation with variable sweep morphing technology can not only replace the traditional elevator and aileron to control the attitude of the robot while flying,but also realize multi-mission flight mode.This paper mainly studied from the points of structural configuration and unsteady aerodynamic characteristics,flight dynamic modeling,trajectory tracking and attitude stabilization,mode transition process stability,experiments verification.The novel flying robot with variable sweep uses tandem wing layout which can not only improve the loadability and the effectiveness of morphing control,but also weaken the coupling caused by morphing between longitudinal and lateral dynamics by coordinated allocation sweep angles of the four airfoils.The basic structure of the flying robot and the corresponding catapult launcher were designed,and two types of motor propulsion systems was used to improve the mobility and agility of the flying robot.The aerodynamic characteristics of the wing layout schemes with different gaps was analyzed using the CFD method to select the more appropriate wing layout.Because the flow field around the flying robot changes drastically during the deploying process after catapult launching,the variations of unsteady aerodynamics were studied in Fluent by dynamic meshing method.This study provides the basis for the subsequent control design and experimental research.The large-scale and rapid morphing of the variable sweep flying robot will cause variations in parameters such as inertial force,aerodynamic force,and position of mass center.In order to describe the dynamic model accurately and study the dynamic characteristics caused by morphing,the multi-rigid body dynamic model of the flying robot was established according to the constraint relationship between the rigid bodies by Kane method,and the fuselage is used as the main rigid body.The longitudinal and lateral dynamic models of the flying robot were decoupled and simplified based on the symmetric and asymmetric morphing planning.The variations of additional forces and additional moments caused by morphing were studied using dynamic response analysis,also the effects on the motion parameters of the flying robot.The control effectiveness of variable sweep control with the traditional elevator and aileron was compared,and the feasibility of replacing the traditional control surface with variable sweep control was also discussed.The variable sweep tandem-wing flying robot is complex nonlinear system with strongly coupling.Considering effects of dynamic characteristics and uncertainties of the system,sliding mode variable structure control method designed with indirect stable sliding mode surface was proposed to realize the trajectory tracking and attitude stabilization.For longitudinal motion system,the control law of outer loop was designed with hyperbolic tangent function,the inner loop was designed with integral sliding mode function,and the adaptive law was used to compensate the external disturbances.Lateral motion system was decoupled to make one control input for only one output.Based on the Hurwitz matrix stability condition,the sliding mode control law for heading was designed.According to the simulation results,the designed sliding mode controllers was proved to achieve the trajectory tracking and attitude stabilization of the flying robot under the influence of external disturbances.For the problem of the significant change of flight dynamic during the transition process of flight mode,the gain scheduled control method based on polytope model was proposed to realize global stability by changing the gain of the control system in real time.The longitudinal dynamic model was converted into a polytopic type by Jacobian linearization method with appropriate scheduled parameters.Based on the polytope model,a robust gain scheduled controller was designed using the affine quadratic stability theory.With the consideration of input saturation,the LQR optimal control method was used to design the state feedback controllers for the vertex systems of the polytope model.the effectiveness of the gain scheduled controller and its robustness under random interference were verified by simulation.The prototype of catapult launched tandem-wing flying robot with variable sweep and catapult launcher were developed,and the experiment system was established.The accuracy of modeling and analysis of the flight dynamics was verified by the dynamic response tests of the open-loop morphing,and the performance of the attitude stabilization controller was verified by the attitude feedback tests.The function of catapult-assisted take-off was verified under folded condition and unfolded condition,respectively.The feasibility of symmetric and asymmetric morphing for pitch control and roll control and the effectiveness of control methods were also verified by the flight test.