Using decision functions for nonlinear controller design

A type of nonlinear controller is introduced which is based on the aggregation of fuzzy sets using decision functions. The fuzzy sets are defined on the domain of discourse of individual input variables of the controller. The nonlinear control surface is formed by an aggregation suitable for the process that is controlled. The nonlinearity of the control surface can be specified explicitly by the selection of the membership functions and the aggregation operator. By keeping the number of fuzzy sets to one per variable, the number of controller parameters is reduced considerably compared to a more conventional fuzzy controller especially when the number of inputs is large. The resulting controller belongs to a more restrictive class of controllers, but the ease of implementation and the reduced complexity often compensates for the loss of generality.