Control Design, A Class Of Nonlinear Systems Based On The Push

With the development of science and technology, the modern industrial systems become more and more complex. The controlled systems in practice usually contain high nonlinearities, uncertainties and time-delay simultaneously. This makes the analysis and synthesis of the system become more complex and difficult. Notice that fuzzy control methodology does not require the exact mathematical models, and with the fuzzy information supplied by the experts, fuzzy algorithm can successfully handle these complex nonlinear systems which are ill-defined or contain uncertainties. Therefore, fuzzy control has become one of the active research topics in the last few years. In addition, as an important approach of adaptive control of nonlinear systems, backstepping technique has been paid considerable attention in recent years. This thesis focuses on the issue of adaptive fuzzy controller design for three kinds of strict-feedback nonlinear systems based on backstepping technique. The main work is summarized as follows:In the first chapter, two schemes of indirect and direct adaptive fuzzy controller are proposed for a class of simple strict-feedback nonlinear systems. The schemes are proposed based on backstepping and the approximation capability of the first class of fuzzy logic systems. The proposed two adaptive schemes guarantee that the tracking error converges to a small neighborhood of zero while all the closed-loop signals remain bounded. Simulation examples are used to demonstrate the effectiveness of the proposed control schemes.The second chapter extends the results in Chapter 1 to the more general systems, which do not only include the external disturbances, but also include unknown virtual control gains. By use of Lyapunov stability theory, it is proved that all the closed-loop signals are bounded and the tracking error converges to a small domain of the origin. Simulation examples are used to demonstrate the effectiveness of the proposed control scheme.In the third chapter, output tracking control has been addressed for a class of time-delayed nonlinear systems of simple strict-feedback form. Indirect and direct adaptive fuzzy control schemes are developed, respectively. The proposed fuzzy controllers guarantee that the resulting closed-loop system is uniformly ultimately bounded and tracking error converges to a small neighborhood of zero. Simulation results are used to demonstrate the effectiveness of the proposed control scheme.At last, the conclusion and perspective are given at the end of the thesis.