Reference : Observation and Control of Anaerobic Digestion Processes for Improved Biogas Production
Dissertations and theses : Doctoral thesis
Life sciences : Biotechnology
Engineering, computing & technology : Electrical & electronics engineering
Engineering, computing & technology : Energy
Security, Reliability and Trust; Computational Sciences
Observation and Control of Anaerobic Digestion Processes for Improved Biogas Production
[en] Observation and Control of Anaerobic Digestion Processes for Improved Biogas Production
Chaib Draa, Khadidja mailto [University of Luxembourg > Interdisciplinary Centre for Security, Reliability and Trust (SNT) > ; University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Engineering Research Unit >]
University of Luxembourg, ​Luxembourg, ​​Luxembourg
Docteur en Sciences de l'Ingénieur
Voos, Holger mailto
Darouach, Mohamed mailto
Hansen, Joachim mailto
Alma, Marouane mailto
Boutat, driss mailto
Zhang, Ping mailto
[en] Nonlinear systems ; Anaerobic digestion ; Nonlinear observer ; H_\infty criterion ; Nonlinear control
[en] In this thesis, we propose a formal modelling framework for the anaerobic digestion process, where we add more degrees of freedom in the control of biogas production. Indeed, we add two additional control inputs to the standardized AM2 (Acidogenesis Methanogenesis, 2 steps) model, re ecting addition of stimulating substrates which enhance the biogas quality and quantity. Then, we describe how the parameters of the resulted nonlinear model can be identi ed, and we analyse the positiveness and boundedness of its state variables. Based on the derived mathematical model and the analysis results, we design di erent software sensors to overcome the lack of reliable and cheap sensors. Indeed, we present a general class of systems to which the considered process model belongs. Then, we design an LMI-based invariant like observer as well as an LMI-based nonlinear observer of the same form as the generalized Arcak's observer. Furthermore, with the aim to render the observer design more robust to disturbances, we include the H1 criterion in its synthesis. Also, to promote the use of the proposed observers in real applications, we extend the methodology to the discrete time case and to the case of nonlinear systems with nonlinear outputs. For the di erent observers design, we use the di erential mean value theorem which allows the transformation of the nonlinear estimation error to a linear parameter varying system. Then, we use the Lipschitz conditions and the Lyapunov standard function to synthesize the stability conditions in the form of linear matrix inequalities. Finally, we enhance the feasibility of the later conditions by using a judicious reformulation of the Young's inequality. In the thesis, we also deal with the process control where we propose a control strategy to track an admissible reference trajectory planned by the plant operator. Moreover, to account for the partial availability of the state vector measurements, we include an exponential nonlinear observer in the control synthesis. Thus, we design an observer based tracking control scheme. To perform the stability analysis of the closed loop system, composed of the system, the observer and the controller, we use the Barbalat's lemma conjointly with the techniques already mentioned for the observers design. Finally, we propose two different methods to compute the controller and the observer parameters. In the first one, we propose to compute them separately. While, in the second one we compute the parameters simultaneously.
University of Luxembourg - UL

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