The Study Of Fuzzy Sliding Mode Control Application For Unstable Plants

Unstable controlled plants are widespread in various modern control fields. They can not be well controlled by ordinary conventional controller due to that their stable state was not easy to reach, so it was necessary to select a suitable and effective way to control them. Sliding mode control could be used to control unstable plants, because of its many characteristics, such as excellent ro bust performance, strong anti-interference ability and easy to realize.However, chattering problem exists. As for the chattering in the sliding mode control, a fuzzy sliding mode controller was designed, and a typical inverted pendulum device was selected as controlled plant to verify performance of the designed fuzzy sliding mode controller. Mathematical model of unstable plant was established, the fuzzy sliding mode controller was designed, and simulation analysis was did.Specific research work is as follows:(1) Scheme design of fuzzy sliding mode controller. About the problem of that unstable plant was controlled difficultly; this paper selected a sliding mode control which was different from conventional control. The princ iple of chattering in the s liding mode control was analyzed, and the scheme that introducing fuzzy control into the sliding mode control to optimize the controller was designed.(2) The selection and mode establishment of unstable plant. Because the inverted pendulum system is a nonlinear, strong coupling, multivariable, higher order unstable plant, and it was an ideal experimental device to verify control method, it was selected as the research plant. The mathematical model of the inverted pendulum system was established. The lineariza tion of the model was did, then the performance of the model was analyzed theoretically.(3) The design of fuzzy s liding mode controller. First, we designed an equivalent sliding mode control rate, judged if it had a sliding mode and could reach by calculation, and the whole system could be quickly reached the equilibrium state by the designed exponential term. When the system was about to reach the sliding mode surface, the exponential term was trended to zero. And only the part of the designed constant velocity worked. Then this term was optimized through the fuzzy control theory, and the parameters was changed in real time through the fuzzy rule, to design a strong robustness, chattering obvious reduction, fuzzy sliding mode controller.(4) Simulation analysis of the fuzzy sliding controller. The structure diagram of the controller was established with MATLAB / simulink, the specific parameters of the controller was determined, and the program of each module was programmed; The fuzzy sliding mode controller was applied to the inverted pendulum system model, and simulation analysis was did.Through the analysis of the simulation results of the designed controller on this topic, it was verified that the controller combining the fuzzy control and the sliding mode control, could not only reduce the chattering problem existing in sliding mode control itself, but also have a strong robustness, fast response, and effective control performance in the whole control process of the inverted pendulum system of unstable plant.