| 1. |
- Avelin, Anders, et al.
(författare)
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Use of combined physical and statistical models for online applications in the pulp and paper industry
- 2009
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Ingår i: Mathematical and Computer Modelling of Dynamical Systems. - : Informa UK Limited. - 1387-3954 .- 1744-5051. ; 15:5, s. 425-434
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Tidskriftsartikel (refereegranskat)abstract
- This paper discusses the accuracy of different types of models. Statistical models are based on process data and/or observations from lab measurements. This class of models are called black box models. Physical models use physical relationships to describe a process. These are called white box models or first principle models. The third group is sometimes called grey box models, being a combination of black box and white box models. Here we discuss two examples of model types. One is a statistical model where an artificial neural network is used to predict NOx in the exhaust gases from a boiler at Mlarenergi AB in Vsters, Sweden. The second example is a grey box model of a continuous digester. The digester model includes mass balances, energy balances, chemical reactions and physical geometrical constraints to simulate the real digester. We also propose that a more sophisticated model is not required to increase the accuracy of the predicted measurements.
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| 2. |
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| 3. |
- Blanco, A., et al.
(författare)
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Use of modelling and simulation in the pulp and paper industry
- 2009
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Ingår i: Mathematical and Computer Modelling of Dynamical Systems. - : Informa UK Limited. - 1387-3954 .- 1744-5051. ; 15:5, s. 409-423
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Tidskriftsartikel (refereegranskat)abstract
- In pulp and paper the modelling and simulation of the pulp production processes was the first major application. Since then several other applications have been realised though papermaking has never been on the lead concerning the use of computer-based modelling and simulation. The complex nature of the materials is one of the most demanding challenges and the biggest hurdle for any electronic description of the papermaking process or paper itself. So other industries took the lead and it is now for the paper industry to learn from these industries what can be done with the help of computers to control or optimise processes or to design new grades. The application of results gained with the use of modelling and simulation techniques in pulp and paper manufacturing processes has helped the industry to, for example, reduce emissions and increase the productivity and cost-efficiency of the processes. Still there are many important tasks open. A better understanding of the mechanisms of the processes and their control loops has to be achieved in order to further improve the paper quality, stabilise the wet-end chemistry, and enhance the runnability. Important features to be developed are new process designs, efficient process monitoring and systems that offer decision support during operation. In this paper a review of the state of the art on modelling and simulation in the pulp and paper industry is presented as well as further research needs.
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| 4. |
- Eriksson, Anders, et al.
(författare)
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A numerical model for fatigue effects in whole-body human exercise
- 2015
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Ingår i: Mathematical and Computer Modelling of Dynamical Systems. - : Taylor and Francis Ltd.. - 1387-3954 .- 1744-5051.
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Tidskriftsartikel (refereegranskat)abstract
- A physiology-based fatigue model was developed and tested, with the long-term objective to study optimal pacing strategies in cross-country skiing. The model considers both aerobic and anaerobic power contributions, with different demands for carbohydrate fuel. The fatigue model accumulates traces from anaerobic efforts, and dissipates fatigue exponentially. The current fatigue value affects the effective work rate output. A limited reservoir of fuel is considered. This paper discusses the numerical formulations. Examples show the relevance of the model for basic regimes of power output, and give qualitatively relevant results, but demonstrate the need for individual physiological parameters. Further examples study the model’s predictions with respect to interval training strategies, with conclusions on work rates and interval lengths.
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| 5. |
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| 6. |
- Ljung, Lennart, 1946-, et al.
(författare)
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Classical Model Validation for Control Design Purposes
- 1997
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Ingår i: Mathematical and Computer Modelling of Dynamical Systems. - : Informa UK Limited. - 1387-3954 .- 1744-5051. ; 3:1, s. 27-42
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Tidskriftsartikel (refereegranskat)abstract
- Model Validation is at the heart of the System Identification process. Recently, much renewed interest has been expressed in so called "identification for control". This means that the design variables associated with the identification process are tailored to achieve models that are well suited for control design purposes. A separate, but closely related issue is to devise validation tests that give information about the model's quality and suitability for control design. This paper shows and discusses how a basic and classical residual test gives such information.
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| 7. |
- Papadopoulos, Alessandro, et al.
(författare)
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A Dynamic Modelling Framework for Control-based Computing System Design
- 2015
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Ingår i: Mathematical and Computer Modelling of Dynamical Systems. - United Kingdom : Taylor & Francis. - 1387-3954 .- 1744-5051. ; 21:3, s. 251-271
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Tidskriftsartikel (refereegranskat)abstract
- This manuscript proposes a novel viewpoint on computing systems’ modelling. The classical approach is to consider fully functional systems and model them, aiming at closing some external loops to optimize their behaviour. On the contrary, we only model strictly physical phenomena, and realize the rest of the system as a set of controllers. Such an approach permits rigorous assessment of the obtained behaviour in mathematical terms, which is hardly possible with the heuristic design techniques, that were mainly adopted to date. The proposed approach is shown at work with three relevant case studies, so that a significant generality can be inferred from it.
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| 8. |
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| 9. |
- Jeppsson, Ulf
(författare)
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A Simplified Control-Oriented Model of the Activated Sludge Process
- 1995
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Ingår i: Mathematical and Computer Modelling of Dynamical Systems. - : Informa UK Limited. - 1387-3954. ; 1:1, s. 3-16
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Tidskriftsartikel (refereegranskat)abstract
- Automatic control systems rely on models to predict the near future and identification algorithms to adapt the models to changing process behaviour. The traditionally highly complex models of the activated sludge process developed for scientific purposes cannot be identified from on-line measurements and are not suited for process control purposes in their present form. Model decoupling based on the different time scales of the dynamic processes is one possible way of attacking this problem. It allows the implementation of more simple and realistically applicable controllers in combination with predictions based on simplified models in hierarchical control structure. This paper discusses these concepts and presents a reduced order model describing carbonaceous removal, nitrification, and denitrification in a medium time scale (several hours/days). The model parameters are identifiable from available on-line measurements and the dynamic behaviour is verified against computer simulations of the IAWQ activated sludge model no. 1.
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