Designing fuzzy logic controller based on combination of terminal sliding mode and state feedback controllers for stabilizing chaotic behaviour in rod-type plasma torch system

In this paper, a fuzzy logic controller is designed for controlling non-linear behaviours in a rod-type plasma torch system. This system may behave chaotically when its parameters pass through critical values, and gives rise to undesirable oscillations, which degrade the performance of the system. In order to avoid such behaviours, the state feedback controller and the terminal sliding mode controller are combined into a fuzzy system to stabilize the equilibrium point of the system. The fuzzy rules include consequent parts in which state feedback control or terminal sliding mode control is utilized for different conditions. The proposed scheme provides the advantages of both methods, i.e. a decreased settling time is achieved using terminal sliding mode control, and using state feedback control, the chattering phenomenon is removed. The proposed method provides robustness against the external disturbance and uncertainty. Numerical simulations are given to verify that the proposed fuzzy control scheme can effectively control chaotic behaviour of the rod-type plasma torch system and the method provides the best performance among the other methods discussed in the paper.