Linear control of nonlinear processes: recent developments and future directions

Nikolaou, Michael; Misra, Pratik

doi:10.1016/s0098-1354(03)00036-x

Cited by 41 publications

(30 citation statements)

References 39 publications

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“…The nonlinearity measure has attracted much attention in the past years, and several definitions and computation methods have been proposed; see the survey paper [24] and the references cited. Roughly speaking, a nonlinearity measure can be regarded as the 'distance' between a nonlinear system and a class of feasible linear systems [25,24]. A larger distance means that the system is 'more' nonlinear; and in this case, a linear control may not achieve good global performance.…”

Section: Nonlinearity Analysismentioning

confidence: 99%

Linear control of a boiler–turbine unit: Analysis and design

et al. 2008

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Section: Nonlinearity Analysismentioning

confidence: 99%

Linear control of a boiler–turbine unit: Analysis and design

et al. 2008

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“…the process control model in Fig. 2 could be linear, although based on a non-linear process model), but it is not clear if that applies to spray drying [18]. Computational fluid dynamics (CFD) simulation techniques can play a role in the development of dynamic process control models (Fig.…”

Section: 'White Box' Modelsmentioning

confidence: 99%

Modern process control techniques in the production of dried milk products – a review

O’Callaghan

Cunningham

2005

Lait

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-Advanced process control techniques are being developed for the manufacture of milk powder. Further developments depend on determining with accuracy the multivariate aspects of thermodynamic properties of a concentrated food in the course of milk powder manufacture. Viscosity must be measured and modelled as a function of total solids, temperature, time and shear rate for each product over the range of conditions encountered in the falling film evaporator and the spray dryer, and, in addition, density and heat transfer coefficients must be determined and modelled versus total solids and temperature for spray drying. Some of these parameters are difficult to measure exhaustively, due to the interactive effects of time, temperature and shear rate. Research needs to be directed at characterising the changing thermodynamic properties of milk at all stages in its transformation to powder and at identifying an appropriate mix of first-principle and empirical models. Future developments are likely to involve models for stickiness, thermodynamic models of spray drying, online monitoring of atomisation and measurement / modelling of particle surface conditions. process control / model predictive control / milk powder / spray drying Résumé -Revue des techniques modernes de contrôle opératoire dans la production de poudres laitières. Des techniques avancées de contrôle de fabrication des poudres laitières sont en cours de développement. Ces développements reposent sur la détermination précise du caractère multivarié des propriétés thermodynamiques du concentré au cours de la fabrication de la poudre de lait. La viscosité doit être mesurée et modélisée en fonction de la teneur en matière sèche totale, de la température, du temps et du taux de cisaillement pour chaque produit sur l'ensemble des conditions rencontrées dans l'évaporateur à flot tombant et dans la tour de séchage par atomisation et, de plus, la masse volumique et les coefficients de transfert de chaleur doivent être déterminés et modé-lisés en fonction de la matière sèche totale et de la température de séchage par atomisation. Certains de ces paramètres sont difficiles à mesurer de façon exhaustive en raison des effets interactifs du temps, de la température et du taux de cisaillement. La recherche doit s'orienter vers la caractérisa-tion du changement des propriétés thermodynamiques du lait à tous les stades de sa transformation en poudre et vers l'identification d'une combinaison appropriée des modèles du premier principe et empiriques. Les futurs développements impliqueront probablement des modèles pour le collage, des modèles thermodynamiques de séchage par atomisation, le contrôle en ligne de l'atomisation et la mesure/modélisation des caractéristiques de surface des particules.

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“…The decomposition of nonlinear systems does not consider the effect of control, and the decomposition criterion comes from the characteristic of the open-loop systems instead of the characteristic of closed-loop systems. It is well known that the feedback may drastically reduce the nonlinearity of a system [30], and the subsystems active operating range determines the switching rule of hard-switching or the weighting function of soft-switching, which can further influences the overall control performance of nonlinear systems. It necessitates an integrated decomposition and combination of multi-model approach based on closed-loop systems, which is the topic of this paper.…”

Section: Introductionmentioning

confidence: 99%