Proportional-Integral Controller Assisted by GPI Observer for Microalgal Continuous Culture

Microalgae have been explored as a promising alternative energy source over the last few years, and several control strategies have been developed to maintain their operational conditions. However, these bioprocesses still pose difficult challenges, due to the nonlinearity and uncertainties of microalgal dynamics. This paper addresses the problem of biomass regulation in a continuous culture of the microalga Dunaliella tertiolecta. Our strategy is based on a Proportional-Integral (PI) controller assisted by a Generalized Proportional Integral (GPI) observer, in order to mitigate the impact of disturbances on biomass levels. The proposed design was tested via numerical simulation, using MATLAB/Simulink™ 2020a environment. The robustness of the controller was demonstrated by subjecting the simulated bioreactor to disturbances and changes in reference biomass densities. The proposed strategy effectively tracked the reference within an insignificant deviation ±0.5%. Furthermore, our proposal effectively rejected disturbances that classical PI was unable to counter.