There Are A Variety Of Uncertain Nonlinear Systems Disturbance Suppression Research

It is well known that nonlinear systems have more accurate and distinct features to demonstrate essential characteristics of the systems compared to linear systems.These ad-vantages lead to the diverse application of nonlinear system in modern industry.Further,nonlinear system plays an important role in the fields of robot control,power transmis-sion,biochemistry and so on.Moreover,the limitations of the actual operation and the complexity of industrial production make the uncertainty almost everywhere in the actual industrial systems.Even worse,some state variables are not measurable,the reasons of which could come from expensive sensors,physical difficulties and effects of noises.So it is of great significance to achieve the asymptotic stability of the nonlinear systems under the condition of uncertainty.Compared to asymptotic stability,finite-time stability has significant advantages in terms of robustness,adaptivity and anti-interference.Therefore,finite-time disturbance attenuation design makes a great impact on the fields of intelligent robots,auto-driving and so on.This thesis mainly discusses the following two issues:?.Disturbance attenuation via double domination approach for feedforward nonlinear system with unknown output functionThis part mainly considers the problem of disturbance attenuation for a class of feedforward nonlinear systems whose output functions are not precisely known.A new control strategy based on a double domination approach is proposed to deal with serious coexistence of various uncertainties,including unknown output function and external disturbances.The novelty lies in a distinct perspective to applying two domination gains in the constructions of the observer and the controller in the case when output functions are perturbed by unmeasurable errors,which was previously regarded as a rather difficult problem.The effectiveness of the proposed design method is verified by a numerical simulation example.?.A new fast global finite-time disturbance attenuation for generalized high-order uncertain nonlinear systemThis part focuses on the problem of fast global finite-time disturbance attenuation for generalized high-order uncertain nonlinear system.Based on finite-time stabilization method and delicate sign function,a new control design is proposed to construct Lyapunov function to cope with uncertainties,i.e.external disturbances.The advantage is that the convergent time is shortened greatly.Controller designed in this part is one-dimensional,the control strategy has a lower requirement on the control size,and its performance is evaluated in terms ofL₂-L_2p gain.Finally,the effectiveness of the proposed design method is verified by a numerical simulation example.