Michael Amrhein

École Polytechnique Fédérale de Lausanne | EPFL · Automatic Control Laboratory

A batch process is characterized by the repetition of time-varying operations of finite duration. Due to this repetition, there are two independent “time” variables, namely, the run time within a batch and the batch index. Accordingly, the optimization objective can be defined for a given batch or over several batches. This chapter formulates the d...

Experimental assessment or prediction of plant steady state is important for many applications in the area of modeling and operation of continuous processes. For example, the iterative implementation of static real-time optimization requires reaching steady state for each successive operating point, which may be quite time consuming. This paper pre...

Models of chemical reaction systems can be complex as they need to include information regarding the reactions and the mass and heat transfers. The commonly used state variables, namely, concentrations and temperatures, express the interplay between many phenomena. As a consequence, each state variable is affected by several rate processes. On the...

Multivariate curve resolution via alternating least squares (ALS) is used to resolve the concentration profiles C and the pure component spectra E of S species from the multivariate absorbance data A, assuming the bilinear model A = C E. Due to the possible permutations of profiles and the presence of intensity and rotational ambiguities, soft cons...

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Two incremental approaches are available in the literature to identify the kinetics of either homogeneous or fluid–fluid reaction systems from transient concentration measurements. The first approach decomposes the identification task into a sequence of subtasks to identify sequentially the reaction and mass-transfer flows, the reaction and mass-tr...

Reaction systems can be represented by first-principles models that describe the evolution of the states (typically concentrations, volume and temperature) by means of conservation equations of differential nature and constitutive equations of algebraic nature. The resulting models often contain redundant states since the various concentrations are...

This paper addresses the control of the blending process in cement industries. This process can be modeled by a nonlinear multivariable system with large parametric uncertainty. Using a specific transformation, a linear parameter varying (LPV) model with set-points as scheduling parameters is developed. Moreover, the model uncertainty originated fr...

This paper proposes a variation of the incremental approach to identify reaction and mass-transfer kinetics from concentration measurements for both homogeneous and gas–liquid reaction systems. This incremental approach proceeds in two steps: (i) computation of the extents of reaction and mass transfer from concentration measurements without explic...

In principal component regression (PCR) and partial least-squares regression (PLSR), the use of unlabeled data, in addition to labeled data, helps stabilize the latent subspaces in the calibration step, typically leading to a lower prediction error. A non-sequential approach based on optimal filtering (OF) has been proposed in the literature to use...

The identification of reaction kinetics involves the determination of a model structure (reaction stoichiometry, rate laws for all reactions) and its corresponding parameters from experimental data. An incremental identification approach for determining the kinetics of homogeneous reaction systems from transient concentration measurements has been...

This paper proposes two transformations for homogeneous reaction systems with inlet and outlet streams that allow isolating three distinct parts of the state vector, namely, the reaction variants, the reaction invariants but inlet- flow variants, and the reaction and inlet-flow invariants. In the absence of an outlet stream, as in batch and semi-batc...

Latent-variable calibration models such as principal component regression and partial least-squares regression may be compromised by systematic disturbances due to instrumental, process and operational drifts. The common thread to explicit drift-correction methods proposed in the literature is that, in the first step, the drift subspace is estimated...

For gas-liquid reaction systems with inlet and outlet streams, this paper proposes a linear transformation to decompose the numbers of moles vector into five distinct parts, namely, the extents of reaction, the extents of mass transfer, the extents of inlet flow, the extents of outlet flow, and invariants. Furthermore, several implications of being...

Minimal state representations are parsimonious models having no redundant states. For homogeneous reaction systems with S species, R independent reactions, p independent inlet streams and one outlet stream, a nonlinear transformation of the numbers of moles to reaction variants, flow variants and constant invariants is proposed. The conditions unde...

This paper deals with the identification of reaction and mass-transfer rates from concentrations measured in gas-liquid reaction systems. It is assumed that the reactions take place in the liquid bulk only. The identification proceeds in two steps: (i) estimation of the extents of reaction and mass transfer from concentration measurements, and (ii)...

The feasibility of using chemometric techniques for the automatic detection of whether a rabbit kidney is pathological or not is studied. Sequential images of the kidney are acquired using Dynamic Contrast-Enhanced Magnetic Resonance Imaging with contrast agent injection. A segmentation approach based upon principal component analysis (PCA) is used...

On-line measurements from first-order instruments such as spectrometers may be compromised by instrumental, process and operational drifts that are not seen during off-line calibration. This can render the calibration model unsuitable for prediction of key components such as analyte concentrations. In this work, infrequently available on-line refer...

Real-time data reconciliation of concentration estimates of process analytes and biomass in microbial fermentations is investigated. A Fourier-transform mid-infrared spectrometer predicting the concentrations of process metabolites is used in parallel with a dielectric spectrometer predicting the biomass concentration during a batch fermentation of...

It is well known that the prediction errors from principal component regression (PCR) and partial least-squares regression (PLSR) can be reduced by using both labeled and unlabeled data for stabilizing the latent subspaces in the calibration step. An approach using Kalman Filtering has been proposed to optimally use unlabeled data with PLSR. In thi...

Correct prediction of analyte concentrations from a new spectrum without drift is possible provided the spectrum lies in the row space spanned by the calibration spectra (space-inclusion condition). However, this condition may be violated as on-line spectrometers are compromised by instrumental, process and operational drifts that are not seen duri...

Spectrometers are enjoying increasing popularity in bioprocess monitoring due to their non-invasiveness and in situ sterilizability. Their on-line applicability and high measurement frequency create an interesting opportunity for process control and optimization tasks. However, building and maintaining a robust calibration model for the on-line est...

A classification methodology for the automatic detection of start- and endpoints of chemical and biotechnological reaction systems from spectral reaction data is proposed. In the calibration phase, several batch experiments must be conducted covering the expected operational variability (e.g., initial concentrations, dosage amount and time). The st...

A classification methodology for the automatic detection of start- and endpoints of chemical and biotechnological reaction systems from spectral reaction data is proposed. In the calibration phase, several batch experiments must be conducted covering the expected operational variability (e.g., initial concentrations, dosage amount and time). The st...

Dynamic Magnetic Resonance Imaging (MRI) with contrast media injection is an important tool to study renal perfusion in humans and animals. The goal of this study is to build classifiers for the automatic classification of a kidney as healthy or pathological. A new algorithm is developed that segments out the cortex from the rest of the kidney incl...

The economic environment in the specialty chemicals industry requires short times to market and thus the ability to develop new products and processes very rapidly. This, in turn, calls for large scale-ups from laboratory to production. Due to scale-related differences in operating conditions, direct extrapolation of conditions obtained in the labo...

This project aims at the optimization of chemical reactions by using online analytical and chemometric methods. The experiments are carried out in a fully automated chemical reactor (1 liter). The host computer controls the standard process variables such as mixture temperature, jacket temperature, pressure, added mass, pH, … In addition, it receiv...

L’industrie chimique doit, aujourd’hui plus que jamais, accélérer le développement des procédés réactionnels. Ceci demande des méthodes performantes d'optimisation, utilisant des plans d’expériences [1], au niveau chimique (choix du solvant, catalyseur, etc.) et au niveau dynamique (choix du profil d'alimentation) [2]. Pour l’optimisation du rendem...

The effect of the presence of metabolism-induced concentration correlations in the calibration samples on the prediction performance of partial least-squares regression (PLSR) models and mid-infrared spectra from Chinese hamster ovary cell cultures was investigated. Samples collected from batch cultures contained highly correlated metabolite concen...

Presented is a flexible bioreactor monitoring and control set-up consisting of a mid-infrared spectroscopic instrument equipped with an in situ probe and a customized bioprocess management and control environment. Reaction data addressing calibration of the mid-infrared spectra using partial least-squares regression resulted in the simultaneous est...

Calibration is the first step in the prediction of concentrations from spectral measurements of chemical reaction systems. It is a well-known fact that the species in the calibration set must include those in the new set. Typically, the calibration set is constructed from nonreacting mixtures of known concentrations. In this paper, it is proposed i...

Target factor analysis (TFA) has been used successfully with reaction data to determine, without knowledge of reaction kinetics, the number of independent reactions and the corresponding stoichiometries. This paper analyzes the applicability of TFA techniques to reaction data on the basis of concentration measurements. It is shown that, in some cas...

The concept of reaction invariants is extended to include flow invariants of chemical-reaction systems with inlet and outlet streams. A transformation to normal form is introduced that allows the separation of (1) the evolution of the independent reactions, (2) the influence of inlet streams, and (3) the behavior of the reaction and flow invariants...

Thèse no 1861 sc. techn. EPF Lausanne. Literaturverz.

Near-Infrared (NIR) spectroscopic methods for on-line concentration estimation are gaining popularity in chemical production. The problem with NIR data, however, is its nonlinear nature rendering standard factor-analytical (FA) techniques inapplicable to estimate the concentrations. To infer concentrations on-line from NIR spectra, the following st...

The analysis of spectral measurements using standard factor-analytical (FA) techniques requires the rank of the absorbance matrix to be equal to the number of absorbing species, S. However, in many practical reaction networks, such an assumption does not hold. This paper examines various scenarios where ‘rank deficiency’ can occur. The most importa...

The analysis of spectral measurements using standard factor-analytical (FA) techniques requires the rank of the ab-sorbance matrix to be equal to the number of absorbing species, S. However, in many practical reaction networks, such an assumption does not hold. This paper examines various scenarios where 'rank deficiency' can occur. The most import...

A novel approach to approximate modeling for multivariable controller design of binary distillation columns is suggested. The modeling idea draws on the wave propagation phenomena characterizing distillation column dynamics. The development of the model only requires knowledge about steady-state design data, including holdups and stationary concent...

The goal of our project (HES-SO n°11246) is to develop chemometric methods that enhance the development of chemical reactions. Semi-batch experiments are performed using a fully automated chemical reactor. Real-time analytical data, infrared (IR) spectra for instance, are syn-chronized with standard process variables [1]. In parallel to the on-line...

Ce travail présente une stratégie nouvelle pour la détection des carcasses avec odeur de verrat. Il fait appel à une technique d’analyse globale du type nez électronique, mais surtout il base la modélisation du nez sur des caractéristiques des échantillons aussi bien chimiques (concentrations de A, S et I) que sensorielles (analyse sensorielle) Un...

A minimal state representation is a dynamic model with no redundant states. For homogeneous reaction systems consisting of S species, R independent reactions, p independent inlet streams, and one outlet stream, a recently developed linear transformation and a novel nonlinear transformation of the numbers of moles vector are investigated. The linear...

The identification of reaction kinetics involves the determination of a model structure (reaction stoichiometry, rate laws for all reactions) and its corresponding parameters from experimental data. An incremental identification approach for determining the kinetics of homogeneous reaction systems from transient concentration measurements has been...