| Sliding mode control (SMC) is becoming an important branch of modern control theory. It is valued for its robust accommodation of uncertainties and its ability to reject disturbances. In SMC system, the system states keep in the sliding mode or its neighborhood through designing control sign. The dynamic properties are determined by the sliding mode. The stability of sliding mode in the variable structure control (VSC) system is ensured completely by the design of sliding mode. How to choose good switch function, how to eliminate the chattering phenomenon while keeping the robustness property of SMC is the most important problem to be resolved for its wide application. These problems are studied in this dissertation. The main contents are as following:Firstly, based on referring to comparatively full literatures in the field of VSC, the history and development status quo of theories of nonlinear system are summarized, and the origin and development of the VSC theories and the main research direction of SMC at present are introduced.Secondly, the elementary concepts about SMC, mathematics description and basic properties of the sliding mode are stated. The designing target and claim, the choosing of switching function, inflexibility and chatting of sliding mode are elaborated.Thirdly, on the basis of the choosing of sliding mode, terminal sliding mode and global terminal sliding mode of nonlinear system are presented, and logarithm terminal sliding mode is put forward. The simulations show that better control effect can be achieved.Forthly, to the singular question in the control strategy, a non-singular terminal sliding mode control is presented, and an improved non-singular terminal sliding mode controller for the plants is designed. While keeping the robust of the system, the time that the system state reach the equilibrium point is finite and it has faster convergence rate and shorter convergence time. The simulation results proved the validity of the theoretical analysis.
|
PDF Full Text Request