| Nonlinear non-minimum phase systems have unstable zero dynamics or internal dynamics,their non-minimum phase property restricts the direct application of many powerful nonlinear control techniques.The control of nonminimum phase systems is more difficult than that of minimum phase systems,and is one of the challenging issues in the control theory and engineering applications.For non-minimum phase system,it is difficult to give the direct relationship between disturbance and measurable information,in addition,the frequency uncertainty and the coupling between the estimated values will cause a large number of the parameter calculation burden.When the state of the system is unmeasurable,the independence of the observer and controller will be affected,and traditional observer methods are not easily extended to tracking control.In this paper.a novel disturbance observer is designed for a class of unknown frequency sinusoidal disturbance non-minimum phase systems,Firstly,the auxiliary filter is designed to excite the disturbance characteristics,and then designing a novel disturbance observer to estimate the key parameters of the disturbance.Finally,disturbance observer-based control(DOBC)can compensate and reject multi-source uncertainty simultaneously by adjusting controller and observer parameters.The research work in the paper is as follows:(1)A separate observer design method is presented in this paper.Firstly,the special auxiliary filter and observer are designed to estimate the sinusoidal disturbance parameters of unknown frequency,meanwhile,the equivalent form of disturbance is reformulated.Secondly,the observer is designed to obtain the input disturbance state.With above,the nonlinear non-minimum disturbance rejection problem can be simplified to the observer design problem for linear system.The effectiveness of the method is demonstrated by Lyapunov theorem and numerical simulation.(2)For a class of uncertain non-minimum phase systems,A compensation method for sinusoidal disturbances is proposed.The unmodeled dynamics considered in this chapter are uncertain nonlinear bounded functions.Firstly,a compound control system with disturbance observer and dynamic output feedback controller is constructed,and disturbance is rejected by adjusting controller and observer parameters.Finally,the stability of disturbance estimates are analyzed by Lyapunov theorem.(3)A class of multiple sources non-minimum phase system is investigated,Besides the unknown frequency sinusoidal,the controlled plant is subjected to bounded noise and unknown nonlinear term simultaneously.Due to the coupling between disturbance rejection and compensator,the closed-loop control system has a complex structure.The nonlinear disturbance observer is designed to estimate unknown sinusoidal disturbance in this paper,the influence of noise on the estimated frequency parameters is rejected by designing noise reduction filters,and the rejection of bounded noise and nonlinear terms can be rejected by combining with dynamic output feedback controller.Finally,the disturbance can be rejected by adjusting controller and observer parameters. |
