Fuzzy logic combining controller design for chaos control of a rod-type plasma torch system

The nonlinear behavior analysis and chaos suppression control for a rod-type plasma torch system was discussed in the paper. The scenarios for the possible non-linear behavior in the plasma torch dynamics were also obtained with respect to the variation of system parameter μ via the numerical simulations, which might provide a guide for finding non-linear phenomena in the practical application of the plasma torch. From the bifurcation diagram, it shows that the plasma torch dynamics exit undesired chaotic behavior. In order to suppress the irregular chaotic motion, a fuzzy logic controller (FLC) that combines a sliding mode controller (SMC) and a state feedback controller (SFC) with guaranteed closed loop stability is designed. Each rule in this FLC has an SMC or an SFC in the consequent part. The role of the FLC is to schedule the final control under different antecedents. It is guaranteed that under the proposed control law, the rod-type plasma system with undesired chaotic motion can asymptotically stabilize to the unstable equilibrium point i.e. zero state. More importantly, the controller thus design can keep the advantages and remove the disadvantage of the two conventional controllers. Numerical simulations show the high performance of this method for chaos elimination in rod-type plasma torch system.