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Modeling and Optimization for Critical Vehicle Maneuvers
Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, The Institute of Technology.
2013 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

As development in sensor technology, situation awareness systems, and computational hardware for vehicle systems progress, an opportunity for more advanced and sophisticated vehicle safety-systems arises. With the increased level of available information---such as position on the road, road curvature and knowledge about surrounding obstacles---future systems could be seen utilizing more advanced controls, exploiting at-the-limit behavior of the vehicle. Having this in mind, optimization methods have emerged as a powerful tool for offline vehicle-performance evaluation, providing inspiration to new control strategies, and by direct implementation in on-board systems. This will, however, require a careful choice of modeling and objectives, since the solution to the optimization problem will rely on this.

With emphasis on vehicle modeling for optimization-based maneuvering applications, a vehicle-dynamics testbed has been developed. Using this vehicle in a series of experiments, most extensively in a double lane-change maneuver, verified the functionality and capability of the equipment. Further, a comparative study was performed, considering vehicle models based on the single-track model, extended with, e.g., tire-force saturation, tire-force lag and roll dynamics. The ability to predict vehicle behavior was evaluated against measurement data from the vehicle testbed.

A platform for solving vehicle-maneuvering optimization-problems has been developed, with state-of-the-art optimization tools, such as JModelica.org and Ipopt. This platform is utilized for studies concerning the influence different vehicle-model configurations have on the solution to critical maneuvering problems. In particular, different tire modeling approaches, as well as vehicle-chassis models of various complexity, are investigated. Also, the influence different road-surface conditions-e.g., asphalt, snow and ice-have on the solution to time-optimal maneuvers is studied.

The results show that even for less complex models-such as a single-track model with a Magic Formula based tire-model-accurate predictions can be obtained when compared to measurement data. The general observation regarding vehicle modeling for the time-critical maneuvers is similar; even the least complex models can be seen to capture certain characteristics analogous to those of higher complexity.

Analyzing the results from the optimization problems, it is seen that the overall dynamics, such as resultant forces and yaw moment, obtained for different model configurations, correlates very well. For different road surfaces, the solutions will of course differ due to the various levels of tire-forces being possible to realize. However, remarkably similar vehicle paths are obtained, regardless of surface. These are valuable observations, since they imply that models of less complexity could be utilized in future on-board optimization-algorithms, to generate, e.g., yaw moment and vehicle paths. In combination with additional information from enhanced situation-awareness systems, this enables more advanced safety-systems to be considered for future vehicles.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2013. , 108 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1608
National Category
Control Engineering
Identifiers
URN: urn:nbn:se:liu:diva-94010Local ID: LIU-TEK-LIC-2013:42ISBN: 978-91-7519-561-2 (print)OAI: oai:DiVA.org:liu-94010DiVA: diva2:628617
Presentation
2013-08-16, Visionen, B-huset, Campus Valla, Linköpings universitet, Linköping, 10:15 (Swedish)
Opponent
Supervisors
Available from: 2013-06-14 Created: 2013-06-14 Last updated: 2013-06-25Bibliographically approved
List of papers
1. Vehicle dynamics platform, experiments, and modeling aiming at critical maneuver handling
Open this publication in new window or tab >>Vehicle dynamics platform, experiments, and modeling aiming at critical maneuver handling
2013 (English)Report (Other academic)
Abstract [en]

For future advanced active safety systems, in road-vehicle applications, there will arise possibilities for enhanced vehicle control systems, due to refinements in, e.g., situation awareness systems. To fully utilize this, more extensive knowledge is required regarding the characteristics and dynamics of vehicle models employed in these systems. Motivated by this, an evaluative study for the lateral dynamics is performed, considering vehicle models of more simple structure. For this purpose, a platform for vehicle dynamics studies has been developed. Experimental data, gathered with this testbed, is then used for model parametrization, succeeded by evaluation for an evasive maneuver. The considered model configurations are based on the single-track model, with different additional attributes, such as tire-force saturation, tire-force lag, and roll dynamics. The results indicate that even a basic model, such as the single-track with tire-force saturation, can describe the lateral dynamics surprisingly well for this critical maneuver.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2013. 22 p.
Series
LiTH-ISY-R, ISSN 1400-3902 ; 3064
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-94203 (URN)LiTH-ISY-R-3064 (ISRN)
Available from: 2013-06-18 Created: 2013-06-18 Last updated: 2017-01-27Bibliographically approved
2. Models and Methodology for Optimal Vehicle Maneuvers Applied to a Hairpin Turn
Open this publication in new window or tab >>Models and Methodology for Optimal Vehicle Maneuvers Applied to a Hairpin Turn
Show others...
2013 (English)Conference paper, Published paper (Other academic)
Abstract [en]

There is currently a strongly growing interest in obtaining optimal control solutions for vehicle maneuvers, both in order to understand optimal vehicle behavior and to devise improved safety systems, either by direct deployment of the solutions or by including mimicked driving techniques of professional drivers. However, it is nontrivial to find the right mix of models, formulations, and optimization tools to get useful results for the above purposes. Here, a platform is developed based on a stateof-the-art optimization tool together with adoption of existing vehicle models, where especially the tire models are in focus. A minimum-time formulation is chosen to the purpose of gaining insight in at-the-limit maneuvers, with the overall aim of possibly finding improved principles for future active safety systems. We present optimal maneuvers for different tire models with a common vehicle motion model, and the results are analyzed and discussed. Our main result is that a few-state singletrack model combined with different tire models is able to replicate the behavior of experienced drivers. Further, we show that the different tire models give quantitatively different behavior in the optimal control of the vehicle in the maneuver.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-94204 (URN)
Conference
The 2013 American Control Conference, June 17-19, Washington, DC, USA
Available from: 2013-06-18 Created: 2013-06-18 Last updated: 2013-06-18Bibliographically approved
3. Studying the Influence of Roll and Pitch Dynamics in Optimal Road-Vehicle Maneuvers
Open this publication in new window or tab >>Studying the Influence of Roll and Pitch Dynamics in Optimal Road-Vehicle Maneuvers
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2013 (English)Conference paper, Published paper (Other academic)
Abstract [en]

A comparative analysis shows how vehicle motion models of different complexity, capturing various characteristics, influence the solution when used in time-critical optimal maneuvering problems. Vehicle models with combinations of roll and pitch dynamics as well as load transfer are considered, ranging from a single-track model to a double-track model with roll and pitch dynamics and load transfer. The optimal maneuvers in a 90◦-turn and a double lane-change scenario are formulated as minimum-time optimization problems, and are solved using numerical optimization software. The results obtained with the different models show that variables potentially important for safety systems, such as the yaw rate, slip angle, and geometric path, are qualitatively the same. Moreover, the numeric differences are mostly within a few percent. The results also indicate that although input torques differ about 50–100 % for certain parts of the maneuver between the most and least complex model considered, the resulting vehicle motions obtained are similar, irrespective of the model. Our main conclusion isthat this enables the use of low-order models when designing the onboard optimization-based safety systems of the future.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-94205 (URN)
Conference
The 23rd International Symposium on Dynamics of Vehicles on Roads and Tracks, 19-23 August, Qingdao, China
Available from: 2013-06-18 Created: 2013-06-18 Last updated: 2013-06-18Bibliographically approved
4. An Investigation of Optimal Vehicle Maneuvers for Different Road Conditions
Open this publication in new window or tab >>An Investigation of Optimal Vehicle Maneuvers for Different Road Conditions
2013 (English)In: IFAC Proceedings Volumes, Volume 46, Issue 21, International Federation of Automatic Control , 2013, Vol. 46, 66-71 p.Conference paper, Published paper (Refereed)
Abstract [en]

We investigate optimal maneuvers for road-vehicles on different surfaces such as asphalt, snow, and ice. The study is motivated by the desire to find control strategies for improved future vehicle safety and driver assistance technologies. Based on earlier presented measurements for tire-force characteristics, we develop tire models corresponding to different road conditions, and determine the time-optimal maneuver in a hairpin turn for each of these. The obtained results are discussed and compared for the different road characteristics. Our main findings are that there are fundamental differences in the control strategies on the considered surfaces, and that these differences can be captured with the adopted modeling approach. Moreover, the path of the vehicle center-of-mass was found to be similar for the different cases. We believe that these findings imply that there are observed vehicle behaviors in the results, which can be utilized for developing the vehicle safety systems of tomorrow.

Place, publisher, year, edition, pages
International Federation of Automatic Control, 2013
Series
IFAC Proceedings Volumes, ISSN 1474-6670 ; Volume 47, Issue 3
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-94206 (URN)10.3182/20130904-4-JP-2042.00007 (DOI)978-3-902823-48-9 (ISBN)
Conference
7th IFAC Symposium on Advances in Automotive Control. The International Federation of Automatic Control, September 4-7, 2013. Tokyo, Japan
Available from: 2013-06-18 Created: 2013-06-18 Last updated: 2016-05-25Bibliographically approved

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Lundahl, Kristoffer

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