Structure analysis of a class of fuzzy controllers using pseudo trapezoid shaped membership functions

An output expression of a class of dual-input single-output fuzzy controlle rs using pseudo trapezoid shaped membership function is given. By structure analysis it is proved that this class of fuzzy controllers is the sum of a global two-dimensional multi-level relay and a local linear or nonlinear p roportional-integral or proportional-differential controller. And the outpu t of this class of fuzzy controllers is a continuous, non-decreasing functi on of its input variables. These and other meaningful results derived from structure analysis based on the output expressions can guide the design of fuzzy controllers.