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Llamas, X. & Eriksson, L. (2018). Control-oriented modeling of two-stroke diesel engines with exhaust gas recirculation for marine applications. Paper presented at Proceedings of the Institution of Mechanical Engineers. Journal of Engineering for the Maritime Environment (Part M)
Open this publication in new window or tab >>Control-oriented modeling of two-stroke diesel engines with exhaust gas recirculation for marine applications
2018 (English)In: Journal of Engineering for the Maritime Environment (Part M), ISSN 1475-0902, E-ISSN 2041-3084Article in journal (Refereed) Epub ahead of print
Abstract [en]

Large marine two-stroke diesel engines are widely used as propulsion systems for shipping worldwide and are facing stricter NOx emission limits. Exhaust gas recirculation is introduced to these engines to reduce the produced combustion NOx to the allowed levels. Since the current number of engines built with exhaust gas recirculation is low and engine testing is very expensive, a powerful alternative for developing exhaust gas recirculation controllers for such engines is to use control-oriented simulation models. Unfortunately, the same reasons that motivate the use of simulation models also hinder the capacity to obtain sufficient measurement data at different operating points for developing the models. A mean value engine model of a large two-stroke diesel with exhaust gas recirculation that can be simulated faster than real time is presented and validated. An analytic model for the cylinder pressure that captures the effects of changes in the fuel control inputs is also developed and validated with cylinder pressure measurements. A parameterization procedure that deals with the low number of measurement data available is proposed. After the parameterization, the model is shown to capture the stationary operation of the real engine well. The transient prediction capability of the model is also considered satisfactory which is important if the model is to be used for exhaust gas recirculation controller development during transients. Furthermore, the experience gathered while developing the model about essential signals to be measured is summarized, which can be very helpful for future applications of the model. Finally, models for the ship propeller and resistance are also investigated, showing good agreement with the measured ship sailing signals during maneuvers. These models give a complete vessel model and make it possible to simulate various maneuvering scenarios, giving different loading profiles that can be used to investigate the performance of exhaust gas recirculation and other controllers during transients.

Place, publisher, year, edition, pages
Sage Publications, 2018
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:liu:diva-147828 (URN)10.1177/1475090218768992 (DOI)
Conference
Proceedings of the Institution of Mechanical Engineers
Available from: 2018-05-15 Created: 2018-05-15 Last updated: 2018-05-21
Llamas, X. & Eriksson, L. (2018). LiU CPgui: A Toolbox for Parameterizing Compressor Models. Linköping: Linköping University Electronic Press
Open this publication in new window or tab >>LiU CPgui: A Toolbox for Parameterizing Compressor Models
2018 (English)Report (Other academic)
Abstract [en]

A toolbox for parameterizing the ellipse model, that is a control-oriented compressor model, to any given measured compressor map is described in detail in this document. The compressor model has been developed in previous publications and shown to be capable of accurately reproducing the measured data obtained from gas stand measurements, for a wide range of compressors, starting from small automotive applications to large compressors used in marine propulsion. In addition, it has been shown that it is possible to extrapolate both mass flow and efficiency to the unmeasured low speed region of the compressor in a physical way. The parameterization algorithm is based on Total Least Squares (TLS), which is shown here and in previous publications to be a fast and reliable approach to fit the compressor model to the map. The toolbox is implemented in a Matlab Graphical User Interface (GUI) in order to make it easy for the user to parameterize the compressor model. To demonstrate the workflow and ease of use, a complete step-by-step example of how to work with the toolbox is provided. To further facilitate the user in applying the model, the package also provides implementations of the ellipse compressor model both as a Matlab function and as a Simulink block. This way, the user can quickly and reliably use the results of the parameterization process in a desired application, e.g. including the compressor model of a given compressor map in a combustion engine simulation model.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2018. p. 45
Series
LiTH-ISY-R, ISSN 1400-3902 ; 3102
Keywords
Compressor Model, Parameterization, Software
National Category
Control Engineering
Identifiers
urn:nbn:se:liu:diva-144398 (URN)LiTH-ISY-R-3102 (ISRN)
Funder
VINNOVA, LinkSIC
Available from: 2018-01-18 Created: 2018-01-18 Last updated: 2018-01-18Bibliographically approved
Hockerdal, E., Frisk, E. & Eriksson, L. (2018). Real-time performance of DAE and ODE based estimators evaluated on a diesel engine. Science China Information Sciences, 61(7), Article ID 70202.
Open this publication in new window or tab >>Real-time performance of DAE and ODE based estimators evaluated on a diesel engine
2018 (English)In: Science China Information Sciences, ISSN 1674-733X, E-ISSN 1869-1919, Vol. 61, no 7, article id 70202Article in journal (Refereed) Published
Abstract [en]

Computation and sampling time requirements for real-time implementation of observers is studied. A common procedure for state estimation and observer design is to have a system model in continuous time that is converted to sampled time with Euler forward method and then the observer is designed and implemented in sampled time in the real time system. When considering state estimation in real time control systems for production there are often limited computational resources. This becomes especially apparent when designing observers for stiff systems since the discretized implementation requires small step lengths to ensure stability. One way to reduce the computational burden, is to reduce the model stiffness by approximating the fast dynamics with instantaneous relations, transforming an ordinary differential equations (ODE) model into a differential algebraic equation (DAE) model. Performance and sampling frequency limitations for extended Kalman filter (EKF)s based on both the original ODE model and the reduced DAE model are here analyzed and compared for an industrial system. Furthermore, the effect of using backward Euler instead of forward Euler when discretizing the continuous time model is also analyzed. The ideas are evaluated using measurement data from a diesel engine. The engine is equipped with throttle, exhaust gas recirculation (EGR), and variable geometry turbines (VGT) and the stiff model dynamics arise as a consequence of the throttle between two control volumes in the air intake system. The process of simplifying and modifying the stiff ODE model to a DAE model is also discussed. The analysis of the computational effort shows that even though the ODE, for each time-update, is less computationally demanding than the resulting DAE, an EKF based on the DAE model achieves better estimation performance than one based on the ODE with less computational effort. The main gain with the DAE based EKF is that it allows increased step lengths without degrading the estimation performance compared to the ODE based EKF.

Place, publisher, year, edition, pages
SCIENCE PRESS, 2018
Keywords
estimation; learning; DAE; ODE; EKF; observability; real-time
National Category
Computer Sciences
Identifiers
urn:nbn:se:liu:diva-149704 (URN)10.1007/s11432-017-9332-6 (DOI)000436183000009 ()
Available from: 2018-07-24 Created: 2018-07-24 Last updated: 2018-08-14
Llamas, X. & Eriksson, L. (2017). Control-Oriented Compressor Model with Adiabatic Efficiency Extrapolation. SAE International Journal of Engines, 10(4)
Open this publication in new window or tab >>Control-Oriented Compressor Model with Adiabatic Efficiency Extrapolation
2017 (English)In: SAE International Journal of Engines, ISSN 1946-3936, E-ISSN 1946-3944, Vol. 10, no 4Article in journal (Refereed) Published
Abstract [en]

Downsizing and turbocharging with single or multiple stages has been one of the main solutions to decrease fuel consumption and harmful exhaust emissions, while keeping a sufficient power output. An accurate and reliable control-oriented compressor model can be very helpful during the development phase, as well as for engine calibration, control design, diagnostic purposes or observer design. A complete compressor model consisting of mass flow and efficiency models is developed and motivated. The proposed model is not only able to represent accurately the normal region measured in a compressor map but also it is capable to extrapolate to low compressor speeds. Moreover, the efficiency extrapolation is studied by analyzing the known problem with heat transfer from the hot turbine side, which introduces errors in the measurements done in standard gas stands. Since the parameterization of the model is an important and necessary step in the modeling, a tailored parameterization approach is presented based on Total Least Squares. A standard compressor map is the only data required to parameterize the model. The parameterization is tested with a database of more than 230 compressor maps showing that it can deal well with different compressor sizes and characteristics. Also, general initialization values for the model parameters are provided using the complete database parameterization results. The results show that the model accuracy is good and in general achieves relative errors below one percent. A comparison of the model accuracy for compressor maps with and without heat transfer influence is carried out, showing a similar model accuracy for both cases but better when no heat transfer is present. Furthermore, it is shown that the model is capable to predict the efficiency characteristics at low speed of two compressor maps, measured with near adiabatic conditions.

Place, publisher, year, edition, pages
United States: S A E Inc., 2017
National Category
Control Engineering Vehicle Engineering
Identifiers
urn:nbn:se:liu:diva-136799 (URN)10.4271/2017-01-1032 (DOI)
Funder
EU, Horizon 2020, 634135
Available from: 2017-04-26 Created: 2017-04-26 Last updated: 2018-01-30Bibliographically approved
Leek, V., Ekberg, K. & Eriksson, L. (2017). Development and Usage of a Continuously Differentiable Heavy Duty Diesel Engine Model Equipped with VGT and EGR. In: SAE Technical Papers 2017-01-0611: . Paper presented at WCX 17: SAE World Congress Experience, Detroit, Michigan, USA, April 4-6, 2017. SAE International, Article ID 2017-01-0611.
Open this publication in new window or tab >>Development and Usage of a Continuously Differentiable Heavy Duty Diesel Engine Model Equipped with VGT and EGR
2017 (English)In: SAE Technical Papers 2017-01-0611, SAE International , 2017, article id 2017-01-0611Conference paper, Published paper (Refereed)
Abstract [en]

Today’s need for fuel efficient vehicles, together with increasing engine component complexity, makes optimal control a valuable tool in the process of finding the most fuel efficient control strategies. To efficiently calculate the solution to optimal control problems a gradient based optimization technique is desirable, making continuously differentiable models preferable. Many existing control-oriented Diesel engine models do not fully posses this property, often due to signal saturations or discrete conditions. This paper offers a continuously differentiable, mean value engine model, of a heavy-duty diesel engine equipped with VGT and EGR, suitable for optimal control purposes. The model is developed from an existing, validated, engine model, but adapted to be continuously differentiable and therefore tailored for usage in an optimal control environment. The changes due to the conversion are quantified and presented. Furthermore, it is shown and analyzed how to optimally control the engine in a fuel optimal way under steady-state conditions, and in a time optimal way in a tip-in scenario.

Place, publisher, year, edition, pages
SAE International, 2017
Series
SAE Technical Papers, ISSN 0148-7191
National Category
Control Engineering Vehicle Engineering
Identifiers
urn:nbn:se:liu:diva-141858 (URN)10.4271/2017-01-0611 (DOI)2-s2.0-85018403089 (Scopus ID)
Conference
WCX 17: SAE World Congress Experience, Detroit, Michigan, USA, April 4-6, 2017
Available from: 2017-10-10 Created: 2017-10-10 Last updated: 2018-01-30Bibliographically approved
Holmbom, R., Liang, B. & Eriksson, L. (2017). Investigation of Performance Differences and Control Synthesis for Servo-Controlled and Vacuum-Actuated Wastegates. In: SAE Technical Paper 2017-01-0592: . Paper presented at WCX 17: SAE World Congress Experience, Detroit, Michigan, USA, April 4-6, 2017. SAE International, Article ID 2017-01-0592.
Open this publication in new window or tab >>Investigation of Performance Differences and Control Synthesis for Servo-Controlled and Vacuum-Actuated Wastegates
2017 (English)In: SAE Technical Paper 2017-01-0592, SAE International , 2017, article id 2017-01-0592Conference paper, Published paper (Refereed)
Abstract [en]

Turbocharging plays an important role in the downsizing of engines. Model-based approaches for boost control are going to increasing the necessity for controlling the wastegate flow more accurately. In today’s cars, the wastegate is usually only controlled with a duty cycle and without position feedback. Due to nonlinearities and varying disturbances a duty cycle does not correspond to a certain position. Currently the most frequently used feedback controller strategy is to use the boost pressure as the controller reference. This means that there is a large time constant from actuation command to effect in boost pressure, which can impair dynamic performance. In this paper, the performance of an electrically controlled vacuum-actuated waste-gate, subsequently referred to as vacuum wastegate, is compared to an electrical servo-controlled wastegate, also referred to as electric wastegate. Their performance is investigated with the two actuators installed on a turbocharged inline four gasoline engine in an engine test bench. Furthermore, different control synthesis designs for these different actuators are investigated. A state-feedback controller with standard models for the electric wastegate is described and implemented, which gives a position-controlled wastegate. One main difference between vacuum and electric wastegate is that the latter has a position sensor. To make an extended comparison between the solutions, the vacuum wastegate is also equipped with a position sensor and controller using standard controller design methods. The controllers are implemented and compared both in a simulation environment and evaluated in an engine test bench. In addition, for the electric wastegate, both soft-landing and tightening features are also implemented and investigated. Their aim is to improve the lifetime and behavior at or near the closed position.

Place, publisher, year, edition, pages
SAE International, 2017
Series
SAE Technical Paper, ISSN 0148-7191
National Category
Control Engineering Vehicle Engineering
Identifiers
urn:nbn:se:liu:diva-141856 (URN)10.4271/2017-01-0592 (DOI)2-s2.0-85018446080 (Scopus ID)
Conference
WCX 17: SAE World Congress Experience, Detroit, Michigan, USA, April 4-6, 2017
Available from: 2017-10-10 Created: 2017-10-10 Last updated: 2018-01-30Bibliographically approved
Sivertsson, M. & Eriksson, L. (2017). Optimal stationary control of diesel engines using periodic control. Proceedings of the Institution of mechanical engineers. Part D, journal of automobile engineering, 231(4), 457-475
Open this publication in new window or tab >>Optimal stationary control of diesel engines using periodic control
2017 (English)In: Proceedings of the Institution of mechanical engineers. Part D, journal of automobile engineering, ISSN 0954-4070, E-ISSN 2041-2991, Vol. 231, no 4, p. 457-475Article in journal (Refereed) Published
Abstract [en]

Measurements and optimal control are used to study whether the fuel economy of a diesel engine can be improved through periodic control of the wastegate, illustrating how modern optimal control tools can be used to identify non-trivial solutions that can improve performance. The measurements show that the pumping torque of the engine is changed when the wastegate is controlled in a periodic manner versus stationary even if the mean position is the same. If this decreases the fuel consumption or not is seen to be frequency and operating point dependent. The measurements indicate that the phenomenon occurs in the time scales capturable by mean value engine models (MVEM). The operating points are further analyzed using a MVEM and optimal control. It is shown that whether the optimal solution exhibits periodic oscillations or not is operating point dependent, but is not due to the instantaneous nature of the controls. Even if an actuator model is added the oscillations persist for reasonable time constants, the frequency of the oscillations is however affected. Further it is shown that the periodic control can be predicted by optimal periodic control theory and that the frequency of the control affects the resulting efficiency.

Place, publisher, year, edition, pages
Sage Publications, 2017
Keywords
Optimal periodic control, diesel engines, optimal control, internal combustion engines, wastegate control
National Category
Control Engineering
Identifiers
urn:nbn:se:liu:diva-117337 (URN)10.1177/0954407016640631 (DOI)000397211700002 ()2-s2.0-85014504643 (Scopus ID)
Note

At the time for thesis presentation publication was in status: Manuscript

Available from: 2015-04-23 Created: 2015-04-23 Last updated: 2018-01-30Bibliographically approved
Llamas, X. & Eriksson, L. (2016). A Model of a Marine Two-Stroke Diesel Engine with EGR for Low Load Simulation. In: 9th EUROSIM Congress: . Paper presented at 9th EUROSIM Congress on Modelling and Simulation. 12 - 16 September 2016 in Oulu, Finland..
Open this publication in new window or tab >>A Model of a Marine Two-Stroke Diesel Engine with EGR for Low Load Simulation
2016 (English)In: 9th EUROSIM Congress, 2016Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

A mean value engine model of a two-stroke ma-rine diesel engine with EGR that is capable of simulatingduring low load operation is developed. In order to beable to perform low load simulations, a compressor modelcapable of low speed extrapolation is also investigated andparameterized for two different compressors. Moreover, aparameterization procedure to get good parameters for bothstationary and dynamic simulations is described and applied.The model is validated for two engine layouts of the same testengine but with different turbocharger units. The simulationresults show a good agreement with the different measuredsignals, including the oxygen content in the scavengingmanifold.

Keywords
Modeling, Parameterization, Simulations, Exhaust gas recirculation, Combustion engines
National Category
Vehicle Engineering Control Engineering
Identifiers
urn:nbn:se:liu:diva-136804 (URN)
Conference
9th EUROSIM Congress on Modelling and Simulation. 12 - 16 September 2016 in Oulu, Finland.
Funder
EU, Horizon 2020, 634135
Available from: 2017-04-26 Created: 2017-04-26 Last updated: 2018-02-22Bibliographically approved
Nezhadali, V. & Eriksson, L. (2016). Analysis of optimal diesel-electric powertrain transients during a tip-in maneuver. In: : . Paper presented at The 9th Eurosim Congress on Modelling and Simulation, 12 - 16 September 2016, Oulu Finland. IEEE
Open this publication in new window or tab >>Analysis of optimal diesel-electric powertrain transients during a tip-in maneuver
2016 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Optimal transients of a hybrid powertrain are calculated with the aim to give a smooth and time efficient acceleration. It is shown that there is a trade-off between time and driveline oscillations where high oscillations can be avoided by slightly longer acceleration time and proper control of the electrical and diesel power sources. During a low oscillation acceleration, there is still the possibility to reduce the amount of total consumed electrical and fuel energy. This is investigated by calculation of optimal controls during acceleration for a fixed time while penalizing the usage of energy in a low oscillation acceleration. The balance between electrical and diesel energy usage during the acceleration is also investigated. The results show that to avoid extreme transients by optimal control, a multidimensional formulation of the objective function including different properties should be considered.

Place, publisher, year, edition, pages
IEEE, 2016
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:liu:diva-128779 (URN)
Conference
The 9th Eurosim Congress on Modelling and Simulation, 12 - 16 September 2016, Oulu Finland
Available from: 2016-05-30 Created: 2016-05-30 Last updated: 2018-01-30Bibliographically approved
Eriksson, L., Nezhadali, V. & Andersson, C. (2016). Compressor Flow Extrapolation and Library Design for the Modelica Vehicle Propulsion Library - VehProLib. In: SAE 2016 World Congress and Exhibition: . Paper presented at SAE 2016 World Congress and Exhibition, Detroit, MI, USA, April 12-14 2016. SAE International, Article ID 2016-01-1037.
Open this publication in new window or tab >>Compressor Flow Extrapolation and Library Design for the Modelica Vehicle Propulsion Library - VehProLib
2016 (English)In: SAE 2016 World Congress and Exhibition, SAE International , 2016, article id 2016-01-1037Conference paper, Published paper (Refereed)
Abstract [en]

Modelbased systems engineering is becoming an important tool when meeting the challenges of developing the complex future vehicles that fulfill the customers and legislators ever increasing demands for reduced pollutants and fuel consumption. To be able to work systematically and efficiently it is desirable to have a library of components that can be adjusted and adapted to each new situation. Turbocharged engines are complex and the compressor model serves as an in-depth example of how a library can be designed, incorporating the basic physics and allowing fine tuning as more information becomes available. A major part of the paper is the summary and compilation of a set of rules of thumb for compressor map extrapolation. The considerations discussed are extrapolation to surge, extrapolation to restriction region, and extrapolation out to choking. Furthermore the compressor diameter is coupled to the maximum performance of the compressor such as maximum speed, mass flow, and pressure ratio. All this is a result of an analysis of a database of more than 300 compressors. The paper uses the compressor modeling to discuss how wishes for extendability and reuse of component performance influences the library design. A Modelica library named Vehicle Propulsion Library VehProLib has been developed to meet these goals by including basic components that give a starting point for modeling and at the same time allows reuse and extendablility.

Place, publisher, year, edition, pages
SAE International, 2016
Series
SAE Technical Papers, ISSN 0148-7191
National Category
Embedded Systems
Identifiers
urn:nbn:se:liu:diva-137758 (URN)10.4271/2016-01-1037 (DOI)2-s2.0-84975316733 (Scopus ID)
Conference
SAE 2016 World Congress and Exhibition, Detroit, MI, USA, April 12-14 2016
Available from: 2017-05-28 Created: 2017-05-28 Last updated: 2018-03-27Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-8646-8998

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