ABSTRACTAlthough fuzzy logic control has created lots of interest in recent years, systematic tuning methods for fuzzy logic controllers have remained uncovered. The applications presented in the literature are usually tuned by trial-and-error methods.In this article a systematic off-line method for tuning a multivariable fuzzy logic controller for an unknown multivariable system is proposed. The system can include time delays, and it is assumed to be stable and linear. In order to keep the structure of the controller simple, the number of the system inputs and outputs are restricted to two. A model of the system is not needed. The rules of the controller and places of the membership functions for the controller outputs are determined from the static gain of the system which can be measured experimentally. Approximate knowledge of the time constants and the delays of the system can help in the selection of the widths of the membership functions. The controller eliminates the steady-state error and keeps t...