Hierarchical fuzzy control for a wastewater anaerobic treatment plant

A hierarchical fuzzy control for a wastewater treatment anaerobic plant is presented. On the basis of a previously developed integrated control, which switches two controllers, two new variables are considered (COJ/X/sub 2/ and /spl Delta/QCH/sub 4/); next, the two controllers are transformed to fuzzy proportional-integral (PI) variables; and finally, Takagi-Sugeno fuzzy supervisor is developed in order to smooth the switching. Hence, a hierarchical fuzzy control structure is built: the low level is constituted by the fuzzy PI and the higher one by the fuzzy supervisor. This new strategy allows an increase in methane production. Applicability of the proposed structure is illustrated via simulations.