The design of stable fuzzy logic controllers with combination of conventional controllers

This paper shows the design of a fuzzy logic controller (FLC) which combines a sliding mode controller (SMC) and a state feedback controller (SFC). Each rule in this FLC has an SMC or an SFC as the consequent part. The role of the FLC is to schedule the two conventional controllers and obtain the final control under different antecedents. Although each sub-system defined by the antecedent part of each rule is readily stabilized by the associated SMC or SFC in the consequent part, the overall system stability on combining the rules cannot be guaranteed immediately. The system stability can be ensured by using a proposed Lyapunov function based design approach. This FLC is applied to balance a car-pole inverted pendulum system as an illustrative example. It is shown that the FLC can keep the advantages and remove the disadvantages of the two conventional controllers