Adaptive Control Of Switched Nonlinear Lower-triangular Systems With Constraints

As a kind of special and important hybrid systems,switched nonlinear systems have profound theoretical research significance and wide application background in engineering practice.However,because the more mixed structure of switched nonlinear systems than that of other systems,and the complexity of nonlinearties,which make the research and application of switched nonlinear systems are quite difficult,many design problems of such systems are worth exploring.By employing backstepping,adaptive neural networks and fuzzy control techniques,this dissertation discusses the feedback control problems for several classes of switched nonlinear systems,and studies the boundedness problem of the corresponding closed-loop systems.The main contents of this dissertation are listed as follows:1.For a class of uncertain strict-feedback nonlinear switched systems with an output constraint,a new adaptive neural-networks-based tracking controller design approach is developed.By introducing a novel barrier Lyapunov function(BLF),the constrained switched system is first transformed into a new system without any constraint,which means the control objectives of the both systems are equivalent.Then the command filter technique is applied to solve the so-called ``explosion of complexity" problem.The backstepping-based controller ensures that all the closed-loop variables are ultimately boundedness,while the output limit is not transgressed and the output tracking error can be reduced arbitrarily small.Finally,simulation results verify the effectiveness of the obtained results.2.For a class of switched non-strict-feedback nonlinear systems with output constraints,an adaptive fuzzy tracking controller design approach is proposed by a generalized tan-type-based barrier Lyapunov function.Combined with variable separation technology,common Lyapunov function method and dynamic surface control technique,an adaptive fuzzy controller is developed such that the finite-time stability of the resulting closed-loop system is ensured.Finally,the performance of the simulation results of a numerical example shows the validity of the presented design scheme.Although the constrained control problem of switched nonlinear systems has been tentatively studied in this dissertation and some effective control methods have been proposed,the research of such problem is still in the elementary step,and many essential problems need tobe further discussed.The future and worthy study topics include: The design of the new barrier function,constrained control design of switched stochastic systems and switched interconnected systems,etc.