On the Piecewise Continuous Control of Methane Fermentation Processes

A. CHAMROO
Laboratoire d’Automatique et d’Informatique Industrielle, Université de Poitiers
40, avenue du recteur Pineau, 86022 Poitiers, France

I. SIMEONOV
Institute of Microbiology, Bulgarian Academy of Sciences
Acad. G. Bonchev Str., 1113 Sofia, Bulgaria

C. VASSEUR, N. CHRISTOV
Laboratoire d’Automatique, Génie Informatique et Signal
Université des Sciences et Technologies de Lille, 59655 Villeneuve d’Ascq, France

Abstract: The paper deals with a new approach for computer-based control of a methane fermentation process in stirred tank bioreactors. The process is described by a non-linear mathematical model based on one-stage reaction scheme. The process control is realized using a piecewise continuous regulator which enables tracking of a variable set point trajectory and overperforms the existing anaerobic digestion control schemes. Computer simulation examples illustrate the performance of the proposed approach.

Keywords: Anaerobic digestion, Non-linear systems, Piecewise continuous control.

Afzal Chamroo received the PhD degree in Automatic Control from the Lille University of Science and Technology, Lille, France, in 2006. Since 2007, he has been an Associate Professor with the ESIP (Ecole Supérieure d’Ingénieurs de Poitiers) and member of the LAII (Laboratoire d’Automatique et d’Informatique Industrielle), Poitiers, France. His research interests include real time identification and control using switched systems.

Ivan Simeonov received the MSc and PhD degrees in Control Engineering from the Technical University of Sofia, Bulgaria, in 1971 and 1981, respectively. Since 1986 he has been a Senior Research Associate with the Bulgarian Academy of Sciences, where he is presently the Head of the research group “Mathematical Modeling and Computer Science” at the Institute of Microbiology. He has been an Associate Professor at the Technical University of Sofia (1988-1999), Technical University of Gabrovo (2000-2005) and New Bulgarian University (since 2005). He is the author/co-author of over 160 scientific papers published in international journals and conference proceedings.

Christian Vasseur (MSc’70, PhD’72) is a Professor of Computer Engineering, Automatics, and Signal Processing at the Lille University of Science & Technology (USTL), Lille, France. He was Director of the ‘Ecole Nationale Supérieure des Arts et Industries Textiles’ in Roubaix, France (1988-1997), and Head of the I3D (Interaction, Image et Ingénierie de la Décision) Research Laboratory at USTL (1998-2004). He is co-author of nearly 200 scientific publications in the field of automatic classification applied to real-time signal and image analysis.

Nicolai Christov (MSc’71, PhD’78) is a Professor of Computer Engineering, Automatics, and Signal Processing at the Lille University of Science & Technology, Lille, France. From 1978 to 2004, he held different research and faculty positions in the Technical University of Sofia (TUS), Bulgaria. He was Vice-Head of the Joint Laboratory of Systems Optimization, TUS – Moscow Power Institute (1988-1990), Head of the TUS Control Systems Research Laboratory (1990-1997) and Co-Chairholder of the UNESCO Chair of Engineering for Development (1997-2004). His research interests are in linear systems theory, optimal and robust control and estimation, and sensitivity analysis and numerical methods for linear systems, in which areas he has published a large number of journal and conference papers and several books.

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CITE THIS PAPER AS:
A. CHAMROO, I. SIMEONOV, C. VASSEUR, N. CHRISTOV, On the Piecewise Continuous Control of Methane Fermentation Processes, Studies in Informatics and Control, ISSN 1220-1766, vol. 17 (2), pp. 181-188, 2008.

1. Introduction

During the last two decades the anaerobic digestion (methane fermentation) has been widely used in the biological wastewater treatment and depolution of highly concentrated wastes from animal farms and agroindustries [1]. Anaerobic processes result in the production of a biogas, an important energy source that can replace fossil fuel sources and thus contribute to the greenhouse gas reduction.

Anaerobic digestion processes are very complex and their efficient control is still an open problem. Due to the very limited on-line information, the process control is usually reduced to the regulation of the biogas production rate (energy supply) or of the concentration of polluting organic matter (depolution control) at a desired value in presence of disturbances [2]. In this case, however, the classical linear regulators do not have good performances because of the strongly non-linear input-output process characteristics [3]. More sophisticated linearizing controllers have been proposed in [2,4], but due to some implementation difficulties they haven’t found practical application.

In this paper a new control scheme for anaerobic digestion processes is proposed, based on the piecewise continuous regulator developed in [6-8]. The proposed control scheme can be efficiently implemented and overperforms the existing anaerobic digestion controllers both in disturbance rejection and set point tracking. The proposed controller is particularly adapted in this context due to its original property which allows itself to be independent of the plant’s model. Thus, it shows robustness against the non linear nature of processes. The paper gives the theory of piecewise control leading to the robust control method. Moreover, simulation examples are proposed so as to show the performance of the approach.

4. Conclusion and Future Works

Control of the anaerobic digestion process presents difficulties due to its non linear nature. However, the proposed method uses a controller, which is independent of the plant’s model, thus overcoming the non linear effects in the present working conditions. Moreover, the regulator can be very easily implemented and requires few step calculations.

As a perspective of our study, works are presently being carried out to realize control of the anaerobic digestion process with a wider range of the set points and disturbances.

ACKNOWLEDGEMENT

This work is supported by the European Union under Grants 15010/02Y0064/03-04 CAR/Presage N 4605 Obj. 2-2004:2 – 4.1 – N 160/4605

REFERENCES

Forster, C.F., D.A. John Wase, Environmental Biotechnology, Ellis Horwood Ltd, N.Y., 1990.
Bastin, G., D. Dochain, On-line estimation and adaptive control of bioreactors, Elsevier Science Publ., Amsterdam, 1991.
Simeonov, I., Modelling and control of anaerobic digestion of organic waste, Chem. Biochem. Eng. Q., 8, 1994, pp. 45-52.
Simeonov, I., I. Queinnec, Linearizing control of the anaerobic digestion with addition of acetate, Control Engineering Practice, 14, 2006, pp. 799-810.
Simeonov, I.S., Mathematical modeling and parameter estimation of anaerobic fermentation processes, Bioprocess Engineering, 21, 1999, pp. 377-381.
Koncar, V., C. Vasseur, Systèmes à fonctionnement par morceaux et poursuite échantillonnée, APII-JESA, 35, 2001, pp. 665-689.
Koncar, V., C. Vasseur, Control of linear systems using piecewise continuous systems. IEE Control Theory & Applications, 150, 2003, pp. 565-576.
Chamroo, A., Studies in Piecewise Continuous Systems: Application in Online Identification and Real Time Control Fields. Ph.D. Thesis, Université des Sciences et Technologies de Lille (in French), 2006.