Order relation is the necessary condition of success of fuzzy control system

Inspired by the quotient space theory and fuzzy concept, it is pointed out that the foundation of success of FCS (fuzzy control system) does not refer to the value-getting of MFs (membership functions) and the success can be achieved by obtaining the mutual relationships between elements, namely the relationships of their order. The hierarchical structure, which is made up of order relation, is the essential characteristic of fuzzy control. It´s the necessary condition of the success of FCS. At the end of this paper, the logical control system based on order relation is given. Its controlling rules are more accustomed to the mental habits of the mankind and it may achieve the ideal performance of steady state. MATLAB´s simulation demonstrates the above-mentioned conclusions.