Performance of an active disturbance rejection control on a simulated continuous microalgae photobioreactor

• Published in: Computers & chemical engineering 2018-09, Vol.117, p.129-144
• Main Authors: Garzón-Castro, Claudia Lorena, Delgado-Aguilera, Efredy, Cortés-Romero, John Alexander, Tello, Edisson, Mazzanti, Gianfranco
• Format: Article
• Language: English
• Subjects: Active disturbance rejection control; Continuous culture; Growth of microalgae; Nonlinear system; Robust control
• ISSN: 0098-1354; 1873-4375
• DOI: 10.1016/j.compchemeng.2018.06.006

•Tracking of the maximum biomass production is achieved using the ADRC strategy.•An ADRC strategy to manage the dilution rate to reach microalgae biomass is proposed.•The simulations show an excellent behavior in terms of reference signal tracking.•The ADRC allows an active estimation and rejection of the disturbance.•The controller proposed is simple but robust against variation of parameters. Microalgae are used for the industrial production of high value compounds. The aim in continuous bioreactors is to obtain the highest biomass production. It is necessary to guarantee that the bioprocesses attain and maintain the optimal reference biomass CX*(t), despite endogenous and exogenous disturbances. This paper describes the numerical simulation of the application of active disturbance rejection control (ADRC) to control the dilution rate (D(t)) in a continuous culture of the microalga Chlorella vulgaris. To reduce the bioprocess to a “SISO” system, the authors chose the dilution rate, D(t), to be the only control signal. The control proposal was illustrated and evaluated through a numerical simulation using MATLAB/Simulink™ environment. The performance of the ADRC was tested by the application of external perturbations and variation of parameters over a nominal case. At nominal conditions, D(t) was always maintained within the physical limits imposed by the bioprocess. Step and smooth type signals, at 96.4%·|Dmax(t)|, were imposed as external perturbation on the control signal input, D(t). The controller response kept the output signal CX(t) within an insignificant 0.0043%·|CXmax(t)|. The algal culture had a strongly asymmetric response to variations of the ideal maximum growth rate, μmax(t) ± 30%·|μmax(t)|, and of the nominal light intensity, Iin(t) ± 30%·|Iin(t)|. Nonetheless, the controller promptly returned the output signal to its reference value, CX(t)*. The numerical test of the control proposal, in summary, showed that the ADRC strategy ensures excellent reference tracking capability and robustness towards parametric uncertainties, un-modeled dynamics, and external disturbances.