Robust Global Stabilization of Continuous Bioreactors

Abstract This paper studies the problem of designing controllers for enlarging the stability region of continuous stirred microbial bioreactors. A specific application is in anaerobic digestion, where the stability region can be very small if the operating steady state is selected to maximize the methane production rate. A control Lyapunov function approach is followed to construct a globally stabilizing state feedback control law. This turns out to be proportional output feedback in the case of anaerobic digestion, where the measurement is the methane production rate. The robustness properties of the feedback controller are also investigated. For situations of large, measurable changes in the organic load of the bioreactor, a feedforward measurement is incorporated in the control law, leading to improved robustness margin.