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Nonlinear System Identification and Control Applied to Selective Catalytic Reduction Systems
Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.ORCID iD: 0000-0002-5948-6303
2014 (English)Doctoral thesis, monograph (Other academic)
Abstract [en]

The stringent regulations of emission levels from heavy duty vehicles create a demand for new methods for reducing harmful emissions from diesel engines. This thesis deals with the modelling of the nitrogen oxide (NOx) emissions from heavy duty vehicles using a selective catalyst as an aftertreatment system, utilising ammonia (NH3) for its reduction. The process of the selective catalytic reduction (SCR) is nonlinear, since the result of the chemical reactions involved depends on the load operating point and the temperature.

The purpose of this thesis is to investigate different methods for nonlinear system identification of SCR systems with control applications in mind. The main focus of the thesis is on finding suitable techniques for effective NOx reduction without the need of over dosage of ammonia. By using data collected from a simulator together with real measured data, new black-box identification techniques are developed. Scaling and convergence properties of the proposed algorithms are analysed theoretically. Some of the resulting models are used for controller development using e.g. feedback linearisation techniques, followed by validation in a simulator environment. The benefits of nonlinear modelling and control of the SCR system are highlighted in a comparison with control based on linear models of the system. Further, a multiple model approach is investigated for simultaneous control of NOx and tailpipe ammonia. The results indicate an improvement in terms of ammonia slip reduction in comparison with models that do not take the ammonia slip into account. Another approach to NOx reduction is achieved by controlling the SCR temperature using techniques developed for LPV systems. The results indicate a reduction of the accumulated NOx.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. , 238 p.
Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-2516 ; 106
Keyword [en]
Nonlinear identification, nonlinear control, selective catalytic reduction, NOx reduction, recursive prediction error method, feedback linearisation, multiple-model
National Category
Control Engineering
Research subject
Electrical Engineering with specialization in Automatic Control
URN: urn:nbn:se:uu:diva-229148ISBN: 978-91-554-8989-2OAI: oai:DiVA.org:uu-229148DiVA: diva2:736091
Public defence
2014-09-19, Room 2446, Polacksbacken, Lägerhyddsvägen 2, Uppsala, 13:15 (English)
Swedish Energy Agency, 32299-1
Available from: 2014-08-27 Created: 2014-08-02 Last updated: 2014-09-08

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