Fuzzy controllers use human expert knowledge to control systems.
However, most of the implementations obtain the routine behaviour of the human operator only. More sophisticated tasks like supervision and adaptation are not implemented although this supervision guarantees the ability of human operators to control complex systems in a robust and stable way. From a control point of view, a fuzzy system is nothing else than a nonlinear control system which can be described e.g by nonlinear algebraic equations and nonlinear differential equations. Many mathematical methods have been developed to solve the stability problem of fuzzy systems, but they have a very sophisticated theoretical level and are only available for simple-structured systems. Stability analysis and design of fuzzy control systems.