Fuzzy control of an anaerobic digestion process

The paper proposes a simple Takagi-Sugeno PI-fuzzy controller for an anaerobic digestion process. A fifth order nonlinear model of the anaerobic digestion process is first presented. A second order linear model of the process is next proposed, and the parameters of the linear model are obtained from an optimization problem solved by a Gravitational Search Algorithm. A PI controller is designed for the linear process model using a frequency domain approach in terms of imposing the phase margin. The Takagi-Sugeno PI-fuzzy controller is designed on the basis of the linear PI controller. The Takagi-Sugeno PI-fuzzy controller is validated by simulation using the nonlinear process model in the fuzzy control system.