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Non-linear Compensator for handling non-linear Effects in EGR VGT Diesel Engines
Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, The Institute of Technology.
Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, The Institute of Technology.
2009 (English)Report (Other academic)
Abstract [en]

A non-linear compensator is investigated for handling of non-linear effects in diesel engines. This non-linear compensator is a non-linear state dependent input transformation that is developed by inverting the models for EGR-flow and turbine flow having actuator position as input and flow as output. The non-linear compensator is used in an inner loop in a control structure for coordinated control of EGR-fraction and oxygen/fuel ratio. A stability analysis of the open-loop system with a non-linear compensator shows that it is unstable in a large operating region. This system is stabilized by a control structure that consists of PID controllers and min/max-selectors. The EGR flow and the exhaust manifold pressure are chosen as feedback variables in this structure. Further, the set-points for EGR-fraction and oxygen/fuel ratio are transformed to set-points for the feedback variables. In order to handle model errors in this set-point transformation, an integral action on oxygen/fuel ratio is used in an outer loop. Experimental validations of the proposed control structure show that it handles nonlinear effects, and that it reduces EGR-errors but increases the pumping losses compared to a control structure without non-linear compensator.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press , 2009. , 30 p.
Series
LiTH-ISY-R, ISSN 1400-3902 ; 2897
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-18348ISRN: LiTH-ISY-R-2897OAI: oai:DiVA.org:liu-18348DiVA: diva2:218521
Available from: 2009-05-28 Created: 2009-05-20 Last updated: 2014-10-08Bibliographically approved
In thesis
1. Control of EGR and VGT for Emission Control and Pumping Work Minimization in Diesel Engines
Open this publication in new window or tab >>Control of EGR and VGT for Emission Control and Pumping Work Minimization in Diesel Engines
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Legislators steadily increase the demands on lowered emissions from heavy duty vehicles. To meet these demands it is necessary to integrate technologies like Exhaust Gas Recirculation (EGR) and Variable Geometry Turbochargers (VGT) together with advanced control systems. Control structures are proposed and investigated for coordinated control of EGR valve and VGT position in heavy duty diesel engines. Main control goals are to fulfill the legislated emission levels, to reduce the fuel consumption, and to fulfill safe operation of the turbocharger. These goals are achieved through regulation of normalized oxygen/fuel ratio and intake manifold EGR-fraction. These are chosen as main performance variables since they are strongly coupled to the emissions. To design successful control structures, a mean value model of a diesel engine is developed and validated. The intended applications of the model are system analysis, simulation, and development of model-based control systems. Dynamic validations show that the proposed model captures the essential system properties, i.e. non-minimum phase behaviors and sign reversals. A first control structure consisting of PID controllers and min/max-selectors is developed based on a system analysis of the model. A key characteristic behind this structure is that oxygen/fuel ratio is controlled by the EGR-valve and EGR-fraction by the VGT-position, in order to handle a sign reversal in the system from VGT to oxygen/fuel ratio. This structure also minimizes the pumping work by opening the EGR-valve and the VGT as much as possible while achieving the control objectives for oxygen/fuel ratio and EGR-fraction. For efficient calibration an automatic controller tuning method is developed. The controller objectives are captured by a cost function, that is evaluated utilizing a method choosing representative transients. Experiments in an engine test cell show that the controller achieves all the control objectives and that the current production controller has at least 26% higher pumping losses compared to the proposed controller. In a second control structure, a non-linear compensator is used in an inner loop for handling non-linear effects. This compensator is a non-linear state dependent input transformation. PID controllers and selectors are used in an outer loop similar to the first control structure. Experimental validations of the second control structure show that it handles nonlinear effects, and that it reduces EGR-errors but increases the pumping losses compared to the first control structure. Substantial experimental evaluations in engine test cells show that both these structures are good controller candidates. In conclusion, validated modeling, system analysis, tuning methodology, experimental evaluation of transient response, and complete ETC-cycles give a firm foundation for deployment of these controllers in the important area of coordinated EGR and VGT control.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2009. 230 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1256
National Category
Control Engineering
Identifiers
urn:nbn:se:liu:diva-18484 (URN)978-91-7393-611-8 (ISBN)
Public defence
2009-06-12, Visionen, B-huset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2009-05-29 Created: 2009-05-28 Last updated: 2009-05-29Bibliographically approved

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Non-linear Compensator for handling non-linear Effects in EGR VGT Diesel Engines(763 kB)351 downloads
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Wahlström, JohanEriksson, Lars

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