Research On Nonlinear Control Method Of Morphing Aircraft

The morphing aircraft can change geometric shape initiatively under different flight conditions and missions to achieve optimal flight performance in different flight phases and satisfy multi-mission requirements.In order to achieve flight stability during the structural deformation of the aircraft,this paper takes span-variable and sweep-variable hypersonic aircraft(missiles)as the study object,carries out study on the flight control method of the morphing aircraft,and explores the advantages of the morphing aircraft compared to the conventional aircraft.Firstly,the dynamic modeling and aerodynamic parameter analysis of the morphing aircraft are carried out.The influence of deformation on the aerodynamic parameters is analyzed.The differences between morphing aircraft and conventional aircraft are analyzed.It shows the essential characteristics of the morphing aircraft that there exists coupling and influence between the aircraft motion and the structural deformation.Secondly,the control problem of hypersonic morphing aircraft during structural deformation in the cruise phase is studied.The LPV model was obtained by Jacobian linearization and compared with the original nonlinear model.A control law based on the state-dependent Riccati equation(SDRE)is designed by used the LPV model.The simulation results show that the control law can make the flight state of the morphing aircraft quickly return to the initial equilibrium state after the deformation and less fluctuate.Then,the tracking control problem of the morphing aircraft in any flight phase is studied.The speed and attitude subsystem of the morphing aircraft are extracted from the original nonlinear model.The adaptive sliding mode control law with preassigned settling time is designed for the two subsystems,and the stability is analyzed and proved theoretically.The simulation results show that the speed and attitude of the morphing aircraft can track the reference command signal within a specified time,and the disturbance rejection capacity is stronger.Finally,the control cooperated with status-deformation problem of hypersonic morphing aircraft is studied.The model is obtained by regarding the structural deformation as a control input.A virtual adaptive sliding mode control law is designed and assigned to three actual control inputs by solving the optimization problem.The simulation results show that the algorithm realizes the control cooperated with status-deformation and it has a good effect.Moreover,when the traditional control input is saturated,the morphing aircraft can compensate it through structural deformation,which means a great advantage over conventional aircraft.