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Fuel Optimal Powertrain Control for Heavy Trucks Utilizing Look Ahead
Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, The Institute of Technology.
2009 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The road topography in highways affects the powertrain control of a heavy truck substantially since the engine power is low in relation to the vehicle weight. In large road gradients constant speed is not possible to keep, which would have been beneficial otherwise, and in some uphills shifting gears becomes inevitable. If information about the road ahead, i.e. look ahead information, is available, then the powertrain can be controlled in a more fuel efficient way. Trial runs are performed, where the velocity trajectory that minimizes energy consumption, is calculated and communicated in real time as set points to the conventional cruise control. This look ahead control gives significant fuel consumption reductions compared to a standard cruise control, while keeping to the same mean speed. The results are the inspiration to further studies in how powertrain control can benefit from look ahead information. An engine with a non-linear fuel map is studied to understand its impact on fuel optimal speed. It is shown that for a significant fuel map non-linearity, quantified by a threshold value, constant speed in small road gradients is no longer optimal. Further, an automated manual transmission (AMT) optimal gear control is studied. It is shown that the reduced propulsion of a typical AMT gear-shifting process must be considered when choosing when to shift gears. Thus, additional reductions of fuel consumption are obtained with a look ahead control based on knowledge of engine and transmission characteristics.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press , 2009. , 14 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1400
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-18077ISBN: 978-91-7393-637-8 (print)OAI: oai:DiVA.org:liu-18077DiVA: diva2:214342
Presentation
2009-04-28, Glashuset, B-Huset, Campus Valla, Linköpings universitet, Linköping, 10:00 (Swedish)
Opponent
Supervisors
Available from: 2009-05-11 Created: 2009-05-05 Last updated: 2009-06-12Bibliographically approved
List of papers
1. Look-ahead control for heavy trucks to minimize trip time and fuel consumption
Open this publication in new window or tab >>Look-ahead control for heavy trucks to minimize trip time and fuel consumption
2009 (English)In: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 17, no 2, 245-254 p.Article in journal (Refereed) Published
Abstract [en]

The scenario studied is a drive mission for a heavy diesel truck. With aid of an on board road slope database in combination with a GPS unit, information about the road geometry ahead is extracted. This look-ahead information is used in an optimization of the velocity trajectory with respect to a criterion formulation that weighs trip time and fuel consumption. A dynamic programming algorithm is devised and used in a predictive control scheme by constantly feeding the conventional cruise controller with new set points. The algorithm is evaluated with a real truck on a highway, and the experimental results show that the fuel consumption is significantly reduced.

Keyword
predictive control, dynamic programming, fuel-optimal control
National Category
Engineering and Technology Computer and Information Science Control Engineering
Identifiers
urn:nbn:se:liu:diva-16629 (URN)10.1016/j.conengprac.2008.07.005 (DOI)
Projects
CADICS
Note

Original Publication: Erik Hellström, Maria Ivarsson, Jan Åslund and Lars Nielsen, Look-ahead control for heavy trucks to minimize trip time and fuel consumption, 2009, Control Engineering Practice, (17), 2, 245-254. http://dx.doi.org/10.1016/j.conengprac.2008.07.005 Copyright: Elsevier Science B.V., Amsterdam. http://www.elsevier.com/

Available from: 2009-02-08 Created: 2009-02-06 Last updated: 2017-12-14
2. Look Ahead Control - Consequences of a Non-Linear Fuel Map on Truck Fuel Consumption
Open this publication in new window or tab >>Look Ahead Control - Consequences of a Non-Linear Fuel Map on Truck Fuel Consumption
2008 (English)In: The 17th IFAC World Congress, 2008Conference paper, Published paper (Other academic)
Abstract [en]

Consequences of non-linearities in specific fuel consumption, sfc, of a heavy truck combustion engine are studied with focus on so small road gradients that constant speed is optimal if the engine torque has an affine relation to fueling. A quasi-static analysis gives valuable insights into the intrinsic properties of minimization of fuel consumption. Two objective functions are shown to give different optimal velocity trajectories on a constant road gradient, when the non-linearity in sfc is significant, a notation which is quantified. For a significant non-linearity, when a constraint is set to keep a final time, switching between two characteristic speeds is optimal. Alternatively, if consumed time, in addition to fuel consumption, is part of the objective function, then keeping to one constant speed is optimal also for significant non-linearities. However, the different optimal solutions still show similarities, since for a certain significant non-linearity a specific speed range determined by the characteristic velocities is shown to be unobtainable for both optimality criteria. Similar results are obtained for a full dynamic model including a realistic fuel map and other realistic constraints.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-18188 (URN)
Conference
The 17th IFAC World Congress
Note

This article is an extended version of (Ivarsson et al., 2008), Optimal Speed on Small Gradients – Consequences of a Non-Linear Fuel Map, presented at the IFAC World Congress 2008.

Available from: 2009-05-11 Created: 2009-05-11 Last updated: 2013-02-27
3. Impacts of AMT Gear-Shifting on Fuel Optimal Look Ahead Control
Open this publication in new window or tab >>Impacts of AMT Gear-Shifting on Fuel Optimal Look Ahead Control
2009 (English)Report (Other academic)
Abstract [en]

A fuel optimal gear shift control has been studied, when look ahead information is available, and the impact of the automated manual transmission (AMT) gear-shifting process is analayzed. For a standard discrete heavy truck transmission, answers are found on when to shift gears, prior to or when in an uphill slope. The gear-shifting process of a standard AMT is modeled, not considering the comfort details, in order to capture the fuel and time aspects of the gear shift. A numerical optimization is performed by dynamic programming, minimizing fuel consumption and time by controlling fuel injection and gear. Since a standard AMT does not have look ahead information, it sometimes gears down unnecessarily and thus gives a significantly higher fuel consumption compared to the optimal control. However, if gearing down is inevitable, the AMT gear-shifting strategy, based on engine thresholds, is a well-functioning gear control so that the optimal control only gives marginal additional savings. To attain the possible fuel reductions it is shown that the reduced propulsion of an AMT gear-shifting process, and the resulting vehicle retardation, must be considered. The point of shifting gears must be chosen to ensure an adequate engine speed in order to get a sufficient engine power after the gear shift, even as the truck is decelerated during gear shift.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2009. 14 p.
Series
LiTH-ISY-R, ISSN 1400-3902 ; 2883
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-18189 (URN)LITH-ISY-R-2883 (ISRN)10.4271/2010-01-0370 (DOI)
Available from: 2009-05-11 Created: 2009-05-11 Last updated: 2014-09-24Bibliographically approved

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