Research On Active Disturbance Rejection Control Theory And Its Applications On Flight Systems

Multi-source disturbances(including unmodeled dynamics,parameter perturbations and external disturbances)always act on the control systems in practical engineering and this significantly deteriorates the control performance of the control systems.With the rapid development of modern technology,high-precision control is becoming an indispensable part of modern control system.As a result,disturbance rejection control is becoming a vital technique in control system design.Active disturbance rejection control(ADRC)is a meaningful disturbance rejection control frame: it employs disturbance observer to estimate disturbance,and then introduces the disturbance estimation to compensate the disturbance in a feedforward way,and finally constructs a composite controller by combining the feedback controller.Since ADRC improves the disturbance rejection performance of closed-loop system significantly,it has attracted wide attentions in control theory community and also been successfully applied in industrial engineering.As for the adverse effects caused by the multi-source disturbances in flight control systems,some theory and application problems on active disturbance rejection control are studied in this dissertation.The contents mainly involve composite nonlinear predictive control for uncertain nonlinear systems with well-defined relative degree,continuous finite-time terminal sliding mode control for uncertain nonlinear systems,composite predictive control for hypersonic vehicle systems,finite-time super-twisting sliding mode control for longitudinal trajectory tracking of Mars entry vehicles,drag based finite-time three-dimensional trajectory tracking for Mars entry vehicles,and composite guidance law design for three-dimensional interception process.The main findings and contributions of the dissertation are summarized as follows:(1)For high order uncertain nonlinear systems with well-defined relative degree,a composite nonlinear predictive controller is designed.Firstly,the nonlinear disturbance observer is introduced to estimate the disturbance in systems.Secondly,the dynamics of the system output are calculated based on system's dynamics and relative degree.Finally,the composite nonlinear predictive is constructed by employing the disturbance estimation information into the receding horizon optimization.To validate the effectiveness of the proposed controller,simulations on a missile system are carried out.The simulation results illustrate that the proposed method not only improves the disturbance rejection performance of the closed-loop system but also guarantees the merits of the nominal performance recovery.(2)For high order uncertain nonlinear systems with mismatched disturbances,continuous finite-time terminal sliding mode control methods are presented.1)For the finite-time stabilization problem of uncertain systems: First of all,high order sliding mode observers are introduced to estimate the disturbances and their high-order derivatives.Second,a novel dynamical terminal sliding mode manifold is constructed by employing the estimation information and system states.Then,a continuous composite controller is developed by introducing a virtual control to guarantee the switching terms only appear in the derivative of control action.Finally,experiments based on the DC-DC buck converter setup are carried out to verify the validity of the proposed control method.The experiment results show that the proposed controller not only improves the disturbance rejection performance of the closed-loop system but also guarantees the continuity of control action.2)For the finite-time output tracking problem of uncertain systems with unmeasurable states: First,the output tracking problem is converted to the stabilization problem of tracking error.Second,the high-order sliding mode observer is introduced to estimate the derivatives and high-order derivatives of output tracking error.And then a novel dynamic terminal sliding mode manifold is constructed based on the estimation information and output tracking error.Finally,both the simulations and experiments based on DC-AC inverter system are carried out to validate the effectiveness of the proposed controller.The simulation and experiment results illustrate that the proposed output feedback control method guarantees the continuity of control action and the finite-time convergence of output tracking error simultaneously.(3)For the longitudinal motion command tracking problem of hypersonic vehicles,a composite nonlinear predictive control scheme is proposed.Firstly,the dynamics of altitude and velocity are calculated based on the longitudinal model of hypersonic vehicles.Secondly,two nonlinear disturbance observers are designed to estimate the disturbances in altitude and velocity subsystems,respectively.Then,composite nonlinear predictive controllers are constructed based on disturbance estimation information and system states.Finally,to verify the validity of the proposed control method,simulations based on the actual flight environment data of hypersonic vehicles are carried out.Simulation results show that the proposed composite control scheme not only improves the tracking precision but also guarantees the merits of the nominal performance recovery.(4)For the longitudinal trajectory tracking problem of Mars entry vehicles,a finite-time super-twisting sliding mode controller is presented.First of all,the three-dimensional trajectory tracking problem is transformed into the longitudinal trajectory tracking problem through the decoupling of lateral and longitudinal motions.Second,the longitudinal trajectory tracking problem is refined to the altitude tracking problem,and the dynamics of altitude tracking error is obtained based on the longitudinal motion model of Mars entry vehicle.Then,a novel dynamical nonsingular terminal sliding mode manifold is constructed by employing the altitude tracking error and its derivative information.Thereafter,a finite-time super-twisting sliding mode controller is developed based on the super-twisting algorithm.Finally,simulations are carried out to validate the effectiveness of the proposed controller.The simulation results show that the proposed controller not only improve the altitude tracking precision but also guarantees the continuity of control action.(5)For the three-dimensional trajectory tracking problem of Mars entry vehicle,a composite finite-time control method is developed based on the drag trajectory tracking strategy.First of all,the trajectory tracking problem of Mars entry vehicle is transformed to the problem of drag trajectory tracking.Second,a sliding mode observer is designed to estimate the disturbance in drag tracking error dynamics.Then,a dynamical nonsingular terminal sliding mode manifold is constructed based on the disturbance estimation information and system states.Finally,a continuous composite super-twisting sliding mode controller is developed by introducing a virtual control to ensure the switching terms only appear in the derivative of control variable.In addition,simulations based on the data of practical Mars exploration missions are carried out to verify the validity of the proposed control scheme.Simulation results illustrate that the proposed method not only guarantee the continuity of control action but also significantly improve the landing precision of Mars entry vehicle.(6)For the guidance law design of three-dimensional interception process with the consideration of autopilot dynamics,a continuous output feedback terminal sliding mode guidance law is proposed.Firstly,based on the parallel approaching method,the three-dimensional guidance problem is transformed into the stabilization of the tangential components of the relative velocity.Secondly,high-order sliding mode observers are introduced to estimate the high-order dynamics of tangential relative velocities.Then,a composite continuous finite-time sliding mode output feedback guidance law is designed based on the control method in Chapter 3.Finally,simulations based on the data of practical interception process are carried out to verify the proposed controller.Simulation results show that the proposed guidance method not only improves the guidance precision significantly but also guarantees the continuity of control action.