Research On Coupling And Uncertainty Of Vehicle And Design Methods For Guidance And Control

Because of the complex flight environment,large flight envelope,and fast flight speed,the guidance and control system of aircraft experience difficulties such as strong nonlinear coupling,significant uncertainties of parameters and disturbances,and complex control limits.The combination of these challenges complicates the design of guidance and control protocols.Based on robust control technologies such as sliding mode control,backstepping,and adaptive dynamic surface,the underlying theory and control methods for coupling and uncertainty systems were researched and applied to the design of guidance and control protocols of aircraft.The main research contents and contributions are:(1)The control of uncertain systems is studied,and three robust and enhanced control methods for unmatched uncertain systems are proposed.First,the robustness of the sliding mode variable structure control in systems with matching uncertainties is shown.For unmatched uncertain systems,Levant’s precise differentiator technology and the second-order sliding mode control are combined to complete the design of a robust controller.Second,the concept of backstepping is adopted.The uncertainties of the system are combined and considered comprehensively.A nonlinear disturbance observer is designed to estimate the combined uncertainty and compensate for it in the control system to enhance the robustness of the control system effectively.Finally,considering that uncertainty is a function of the state of a system,a two-layer adaptive dynamic surface control method is proposed,which is better than the existing single-layer adaptive control method.(2)The control of coupling systems is studied,and three control methods for a coupling system are proposed.The studied coupling systems are classified into state-coupling and control-input coupling systems according to the coupling relationship between the control input and system state.First,a distributed control method based on direct coupling compensation,which is the most studied method in the existing literature,is presented.On this basis,a vector control method based on direct coupling compensation is proposed.Second,inspired by the difference between backstepping and feedback linearization,a control method for coupling and effective compensation of the reference input is proposed.Theoretical analysis and simulation results show that this control scheme can maximize control efficiency.Finally,a new vector control method based on a vector algorithm,which provides theoretical support for the design of a non-decoupled vector controller for the attitude of an aircraft,is proposed for a class of control input coupling systems.(3)The attitude control of a vehicle is studied,and a new non-decoupled vector control method is proposed.The modeled uncertainty of the control system of the vehicle and the uncertainties in vector coupling are considered,which is different from the traditional attitude control that decouples aircraft dynamics with an expression in the ballistic coordinates or speed coordinates.This study establishes the velocity vector and angular velocity vector dynamics within the body-fixed coordinates.The control of the airspeed,angle of attack,sideslip angle,and roll-angle velocity are transformed into the tracking space vector.First,a vector-controller for velocity and attitude control of a vehicle with thrust is designed.Second,a vector controller for attitude control of a vehicle without thrust is designed.These provide new ideas and methods for attitude control.(4)The fixed-time convergence control for higher-order systems is studied,an adaptive integral sliding mode control method with fixed-time convergence is proposed,and a new three-dimensional nonlinear guidance law is designed.To address the issue of fixed-time convergent control of higher-order systems,many scholars have conducted extensive research,mainly focusing on the design of new sliding surfaces.However,this design is relatively complex and requires approximate treatment.The homogeneous theory is combined with the integral sliding mode and adaptive control to address this issue.An adaptive integral sliding mode control method with fixed-time convergence is proposed and applied to the design of a three-dimensional guidance protocol.A novel three-dimensional nonlinear guidance protocol is developed for the autopilot feature.(5)The integrated guidance and control of a missile is studied,and a method for integrating it with full-state coupling is proposed.A model that integrates the guidance and control with whole coupling states is developed,where the control and guidance systems are not separate.The channels of the guidance and control systems are merged,which enables their integration.An adaptive dynamic surface controller is developed to complete the integration of the guidance and control with whole states of coupling.