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Reaearch On Several Control Issues For A Class Of Nonsmooth Uncertain Systems

Posted on:2016-01-31Degree:DoctorType:Dissertation
Country:ChinaCandidate:J B GuFull Text:PDF
GTID:1108330470470018Subject:Control theory and control engineering
Abstract/Summary:PDF Full Text Request
There are a large number of nonsmooth dynamical systems in engineering practice, whose states may be driven by nonsmooth dynamics. Although plenty of outstanding work has been done in nonsmooth control field by the researchers over the world, the existing theories and techniques of analysis and design cannot handle all problems of nonsmooth uncertain systems due to the complexity of the nonsmooth dyanimcs. Therefore, the important work with the large significance and value is to improve the current analysis and design methods of nonsmooth dynamical systems, and generalize the nonsmooth theories in the view of control engineering practice.In order to solve the typical control problems of the nonsmooth dynamical systems in the industry, this dissertation concens three typical control problems that involve the analysis and design of the nonsmooth dynamical systems. In other words, static error estimation for a class of second-order mechanical systems, SMC design on a class of nonsmooth switching surfaces and nonsmooth robust control for a class of third-order systems with saturation are considered in the dissertation. The main contributions of this dissertation are summarized as follows:Firstly, the static error of a class of second-order mechanical systems with PD control caused by dry friction is analyzed. The results show that if the closed-loop system is over damped or critically damped, the static servo error may be the largest for the motion starting from the steady state. While the static servo error can be regulated according to the initial condition if the closed-loop system is under damped. Finally, the simulations for a simple one-degree-of-freedom (1DOF) mass-spring system are carried out to illustrate our results.Secondly, a new sliding surface design for sliding mode control of a class of nonlinear plants is proposed. The plants may involve the matched and unmatched uncertainties. In order to obtain the stable dynamics of the states with the unmatched uncertainties, the sliding surface that includes the unmatched uncertainties, whose values are assumed to be measurable, but structures are unknown, is constructed. The reaching phase is designed to ensure the stability of the closed loop with such a uncertain sliding surface. This result generalizes the robust design of the sliding mode control though the sliding surface may be uncertain.Thirdly, a nonsmooth two-degree-of-freedom (2DOF) controller for a class of third-order nonlinear systems with saturation is proposed. The nonsmooth feedback control insures the constringency to a constant ultimate value of the system states, and the 2DOF compensation design guarantees the ultimate value to be the equilibrium point of the system if the initial condition of the system is already known. The numerical simulations of ship steering under several conditions verify the effectiveness of the proposed method.
Keywords/Search Tags:Nonsmooth dynamical systems, Uncertainties, Nonsmooth feedback control, Sliding mode control
PDF Full Text Request
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