Application of rough set theory on system modeling

The available knowledge (rules) can be extracted from original data by using rough set theory (RST). Based on this idea, RST is used to model for an actual system. The system consists of a variable-frequency controller, an AC motor and a water-box. The steps of the system modeling is that, firstly, input-output data sets are obtained by sampling; then, the rough set model of system (rules set) is gotten according to rough set algorithm; and finally, the validity of the model is verified by comparing with actual system. In modeling process, it is important that how to determine the attributes set of information table, to reduct the attributes according to their significance, and to obtain the decision rules.