Saturated linear dynamic output-feedback control for a class of three-state continuous bioreactors with inhibited kinetics

The problem of designing a saturated output-feedback controller to stabilize a class of continuous three-state bioreactors with Haldane inhibited kinetics is addressed. The reactor must be maintained about the (locally stable but possibly structurally unstable) steady-state with maximum production rate by manipulating the substrate feed rate on the basis of a biomass measurement. The consideration of the problem in the light of bioreactor (bifurcation and invariant set) dynamical and (passivity and observability) structural characteristics leads to a saturated linear dynamic OF control design with: (i) PI scheme with observer-based antiwindup protection, (ii) simple construction and tuning, and (iii) closed-loop robust stability conditions in terms of control gains and limits. The PI controller recovers (up to observer convergence and saturation) the behavior of a model-based nonlinear state-feedback passive stabilizing controller equivalent to an exact nonlinear model-based predictive controller with infinite-time receding horizon. The proposed approach is illustrated with a representative case example through numerical simulations.

► The problem of controlling three-state bioreactors with biomass measurement is considered.
► The optimal steady-state (SS) is open-loop locally stable but not robustly stable.
► The problem is addressed within a constructive observer control design framework.
► Reactor mass invariants, bifurcation, passivity, and observability properties are exploited.
► The problem is solved with a saturated linear dynamic PI biomass controller.