Optimization of olive-oil extraction using nonlinear H-infinity control

Olive-oil extraction is a process carried out by thousands of small industrial units in the Mediterranean countries (olive-oil mills), often in an empirical manner and using heuristic parametrization. The article proposes a new nonlinear H-infinity control approach for optimizing olive-oil extraction. The state-space model of the olive-oil extraction process is formulated after taking into account time-delays between the control inputs and its outputs. This state-space model undergoes approximate linearization around a temporary operating point which is re-computed at each step of the control method. The linearization is based on Taylor series expansion and on the computation of the model's Jacobian matrices. For the approximately linearized description of the olive-oil extraction system an optimal (H-infinity) feedback controller is designed. The computation of the controller's feedback gain requires the solution of an algebraic Riccati equation which also takes place at each iteration of the control method. The stability properties of the H-infinity control scheme are proven through Lyapunov analysis.