Feedback control design for an anaerobic digestion process

Abstract

An approach for the design of linear feedback controllers for anaerobic digestion systems is presented. The ef¯uent chemical oxigen demand (COD) concentration and the dilution rate are taken respectively as the regulated and the manipulated variables. The control design is based on simple stepresponse models of the process endowed with an input delay to account for dead-times induced by measurement devices. The resulting feedback controller has a traditional proportional-integral (PI) control structure, so it can be easily implemented with conventional control technologies. Since the concentration of volatile fatty acids can be easily and quickly measured as compared with COD concentration, it is used as a secondary measurement that is incorporated into the feedback loop scheme to enhance the robustness of the control scheme with respect of in¯uent disturbances. The performance of the proposed control scheme is illustrated via numerical simulations and experimental work.

On the dynamic optimization of methane production in anaerobic digestion via extremum-seeking control approach

“…The feedback control schemes can be found in literature, they are mostly focused on the regulation of the organic pollution level, measurable as chemical oxygen demand (COD), or in to tracking reference trajectories for some operational variables which are readily available on-line (Álvarez-Ramírez et al, 2002;Bastin and Dochain, 1990;Flores-Estrella et al, 2013;Méndez-Acosta et al, 2005, 2008. The most popular ones are: linear PID-like controllers (Álvarez-Ramírez et al, 2002), robust output linearizing control schemes (see, e.g.…”

“…The most popular ones are: linear PID-like controllers (Álvarez-Ramírez et al, 2002), robust output linearizing control schemes (see, e.g. Méndez-Acosta et al, 2008) and adaptive controllers (Mailleret et al, 2004).…”

Automatic process control in anaerobic digestion technology: A critical review

“…A wide variety of control strategies were studied to manipulate feeding rate, which included proportional integral (PI) control (Steyer et al, 1999;Alvarez-Ramirez et al, 2002), PID control (García-Diéguez et al, 2011), adaptive control (Hilgert et al, 2000;Luo et al, 2014), robust adaptive (Petre et al, 2013), fuzzy logic (Murnleitner et al, 2002;Djatkov et al, 2014), neural network (Holubar et al, 2002(Holubar et al, , 2003, and neural fuzzy (Waewsak et al, 2010). The feeding rate can be used to simultaneously regulate the retention time and organic loading rate, allowing microbial communities in the system to adapt to the disturbances.…”

Multi-objective cascade controller for an anaerobic digester

“…A combination of the on/off and neural networks algorithm to control bicarbonate was proposed by Guwy et al [13]. Other researchers have used PID (proportional-integral-derivative) controllers for regulating AWT processes [14][15][16][17] because this type of controller can be easily implemented in wide variety of plants. However the tuning of these controllers is based on heuristic rules.…”

“…A few cascade applications can be found in the literature. Alvarez-Ramirez et al [15] have shown a direct feedback control system using only PID controllers in a cascade configuration. This system allows the regulation of an anaerobic digester working at a low COD concentration.…”