Authors: Muñoz, Diego A.; Marquardt, Wolfgang

Abstract: This work focuses on the control design for feedback linearizable nonlinear systems with unknown time-varying disturbances and uncertainty such that bounds on inputs and state constraints are not violated. Exploiting the special structure of the systems considered, controllers based on Lyapunov's direct methods are easily synthesized, which enforce asymptotic stability in the presence of bounded inputs. However, these controllers do not account explicitly for state constraints in the presence of disturbances and uncertainty. The solution of this task is addressed in this work by an optimization-based method, the so-called normal vector approach.

Keywords: Model-based Control; Optimization and Scheduling

Digital Object Identifier (DOI): 10.3182/20120710-4-SG-2026.00143

Conference: 8th IFAC International Symposium on Advanced Control of Chemical Processes (2012)

Location: Furama Riverfront, Singapore

Start Date: Tue Jul 10 2012 - End Date: Fri Jul 13 2012

Page Numbers: 916-921

Authors: A. N. Idris, Elrashid; Engell, Sebastian

Abstract: For continuously operated processes, even a small increase in the efficiency pays important dividends in terms of energy savings and profit. Therefore, tighter and more efficient control of chemical plants is becoming a strategic objective. In this work, we demonstrate the use of dynamic process optimization to improve the business performance of chemical processes. Model predictive control techniques are widely applied to coupled multivariable control problems. The reference values in these problems are usually adjusted by infrequent optimizations based upon a static rigorous nonlinear model of the plant. In between these optimizations, however, the process may undergo sub-optimality of operation due to the presence of disturbances. In this paper, nonlinear model-based optimization with different schemes is proposed to combine optimal operation and feedback control. The work demonstrates the feasibility and the potential of using optimizing as well as economics-oriented tracking control techniques for a challenging example, a catalytic distillation process. The performances of the proposed controllers are investigated and compared. This work points out that by using direct optimizing NMPC, the plant economics can be handled better while guaranteeing the product specifications.

Keywords: Model-based Control; Optimization and Scheduling; Process Applications

Digital Object Identifier (DOI): 10.3182/20120710-4-SG-2026.00146

Conference: 8th IFAC International Symposium on Advanced Control of Chemical Processes (2012)

Location: Furama Riverfront, Singapore

Start Date: Tue Jul 10 2012 - End Date: Fri Jul 13 2012

Page Numbers: 922-927

Authors: Komulainen, Tiina M.; Stølen, Anne Bleken; Janbu, Astrid Oust

Abstract: In this paper the experimental design and modeling of E.coli ER2566 bacteria growth in a bioreactor are presented. The goal of the study is to explore the possibilities to use probabilistic models for bioreactor modeling. Flask tests were performed in conditions corresponding to a full 33 experimental design. Based on the flask test results, a 1/3 of the design matrix was chosen for the bioreactor experiments. The bacterial growth data was used to compare the proposed Markov chain model with the modified Grompertz model. The proposed modeling method combines biologically inspired Markov chain with probabilistic growth/no-growth functions. The performance of the Markov chain model was similar to the performance of the Grompertz model, giving a good basis for further modeling studies.

Keywords: Batch Process Modeling and Control; Process Applications; Modeling and Identification

Digital Object Identifier (DOI): 10.3182/20120710-4-SG-2026.00121

Conference: 8th IFAC International Symposium on Advanced Control of Chemical Processes (2012)

Location: Furama Riverfront, Singapore

Start Date: Tue Jul 10 2012 - End Date: Fri Jul 13 2012

Page Numbers: 928-933

Authors: Vargas, Alejandro; Dewasme, Laurent; Moreno, Jaime A.; Vande Wouwer, Alain

Abstract: An output-feedback controller is proposed for fed-batch cultures of microbial strains exhibiting overflow metabolism, i.e., cultures where cell strains may produce inhibiting metabolites when excess substrate is fed. The control objective is therefore to control the substrate feed rate in order to remain near the optimal substrate concentration during the whole culture. The proposed controller uses measurements of an output signal that can be calculated from on-line process data and determines the necessary dilution rate to maintain the output near its local, time-varying, maximum at all times. The controller is hybrid, combining a proportional plus integral controller with antiwindup, modified so that the error signal used in the feedback may change its sign according to a state machine which keeps track of whether the control action should be positive or negative. The transition is made smoothly to avoid chattering and based on an auxiliary variable which follows the local output maximum. Partial proof of convergence is given and simulations of the model of a yeast production system show the applicability of the proposed strategy.

Keywords: Optimization and Scheduling; Batch Process Modeling and Control

Digital Object Identifier (DOI): 10.3182/20120710-4-SG-2026.00145

Conference: 8th IFAC International Symposium on Advanced Control of Chemical Processes (2012)

Location: Furama Riverfront, Singapore

Start Date: Tue Jul 10 2012 - End Date: Fri Jul 13 2012

Page Numbers: 934-939

Authors: Ranzan, Cassiano; Trierweiler, Luciane Ferreira; Hitzmann, Bernd; Trierweiler, Jorge Otávio

Abstract: In this work the technique of fluorescence spectroscopy was investigated as a tool to measure the main variables of interest in the production of ethanol from sugarcane juice. In order to do that, a methodology for the construction of chemometric models based on the intensities presented by excitation/emission pairs in the fluorescence spectra was proposed and tested. The results indicate that it is a promising technique, but still demanding further studies about the influence of broth composition in the spectra and how to take it into consideration in the chemometric modeling.

Keywords: Process and Control Monitoring; Process Applications

Digital Object Identifier (DOI): 10.3182/20120710-4-SG-2026.00166

Conference: 8th IFAC International Symposium on Advanced Control of Chemical Processes (2012)

Location: Furama Riverfront, Singapore

Start Date: Tue Jul 10 2012 - End Date: Fri Jul 13 2012

Page Numbers: 940-945

Authors: Kim, Kwang-Ki; Cheong, Kim Seng; Chen, Kejia; Braatz, Richard D.

Abstract: This paper studies the parameter-dependent characteristics of a gene switching model that consists of dual positive feedback loops. Developing a predictive mathematical model for large regulatory networks in biological systems would be useful for their analysis and design. A parameter estimation scheme is proposed based on the observation of the steady-states for a gene switching model. Deterministic and stochastic stability are studied for this model, as well as other important system behaviors such as convergence rate to a stable equilibrium point, hysteresis induced by two time scales of the system model, and noise sensitivity with respect to the system parameters. Sensitivity of system performance indices with respect to the system parameters are analyzed in terms of H_infinity- and H₂-norms of the linearized system model with their closed-form solutions. The presented qualitative and quantitative studies of the system characteristics enable the synthesis of a robust gene regulatory network that achieves desired static and dynamic responses.

Keywords: Process Applications; Modeling and Identification

Digital Object Identifier (DOI): 10.3182/20120710-4-SG-2026.00201

Conference: 8th IFAC International Symposium on Advanced Control of Chemical Processes (2012)

Location: Furama Riverfront, Singapore

Start Date: Tue Jul 10 2012 - End Date: Fri Jul 13 2012

Page Numbers: 946-951

Authors: Jia, Gengjie; Gunawan, Rudiyanto

Abstract: Kinetic model identification of metabolic networks is important, but still represents a significant challenge. The difficulties faced vary from the vast kinetic parameter search space to the lack of complete parameter identifiability. To meet these challenges, an incremental modeling approach is proposed here, including two key components—dynamic flux calculation and flux-based kinetic parameter estimation. In essence, the identification method relies on time-course concentration data to generate the family of consistent metabolic flux values and by doing so, the parameter estimation step can be done one flux at a time. The key contribution of the method is an efficient generation of a library of kinetic models with similar goodness of fit to the provided data. The performance of this identification method is demonstrated using a generic branched metabolic pathway model and the glycolytic pathway model of Lactococcus lactis (L. lactis).

Keywords: Modeling and Identification; Process Applications

Digital Object Identifier (DOI): 10.3182/20120710-4-SG-2026.00189

Conference: 8th IFAC International Symposium on Advanced Control of Chemical Processes (2012)

Location: Furama Riverfront, Singapore

Start Date: Tue Jul 10 2012 - End Date: Fri Jul 13 2012

Page Numbers: 952-957

Authors: Kim, Woohyun; Eom, Moon-Ho; Lee, Sang-Hyun; Choi, Jin-Dal-Rae; Park, Sunwon

Abstract: To develop a commercial fermentation process producing butanol, a kinetic model describing the metabolism in an acetone-butanol-ethanol (ABE)-producing by Clostridium acetobutylicum ATCC 824, was proposed by modifying the previously proposed metabolic pathways. We used an efficient optimization algorithm combining a genetic algorithm and the Levenberg-Marquardt algorithm in order to estimate the kinetic parameters of the model with experimental data obtained from a batch fermentor because of the complexity of the model equations. To evaluate the kinetic parameters estimated with the fermentation experiments using C. acetobutylicum ATCC824, an additional experiment was carried out using the modified clostridium, where pathway deletion was introduced. Thus, this kinetic study will be contributed to designing C. acetobutylicum for enhanced ABE production.

Keywords: Modeling and Identification; Process Applications

Digital Object Identifier (DOI): 10.3182/20120710-4-SG-2026.00186

Conference: 8th IFAC International Symposium on Advanced Control of Chemical Processes (2012)

Location: Furama Riverfront, Singapore

Start Date: Tue Jul 10 2012 - End Date: Fri Jul 13 2012

Page Numbers: 958-963