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Vehicle dynamics platform, experiments, and modeling aiming at critical maneuver handling
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.
Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, The Institute of Technology.
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: urn:nbn:se:liu:diva-94203ISRN: LiTH-ISY-R-3064Libris ID: 20014448OAI: oai:DiVA.org:liu-94203DiVA: diva2:630272
Available from: 2013-06-18 Created: 2013-06-18 Last updated: 2017-01-27Bibliographically approved
In thesis
1. Modeling and Optimization for Critical Vehicle Maneuvers
Open this publication in new window or tab >>Modeling and Optimization for Critical Vehicle Maneuvers
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:nbn:se:liu:diva-94010 (URN)LIU-TEK-LIC-2013:42 (Local ID)978-91-7519-561-2 (ISBN)LIU-TEK-LIC-2013:42 (Archive number)LIU-TEK-LIC-2013:42 (OAI)
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
2. Models and Critical Maneuvers for Road Vehicles
Open this publication in new window or tab >>Models and Critical Maneuvers for Road Vehicles
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

As manufacturers are pushing their research and development toward more simulation based and computer aided methods, vehicle dynamics modeling and simulation become more important than ever. The challenge lies in how to utilize the new technology to its fullest, delivering the best possible performance given certain objectives and current restrictions. Here, optimization methods in different forms can be a tremendous asset. However, the solution to an optimization problem will always rely on the problem formulation, where model validity plays a crucial role. The main emphasis in this thesis lies within methodology and analysis of optimal control oriented topics for safety-critical road-vehicle maneuvers. A crucial element here is the vehicle models. This is investigated as a first study, evaluating the degree to which different model configurations can represent the lateral vehicle dynamics in critical maneuvers, where it is shown that even the low-complexity models describe the most essential vehicle characteristics surprisingly well.

How to formulate the optimization problems and utilize optimal control tools is not obvious. Therefore, a methodology for road-vehicle maneuvering in safety-critical driving scenarios is presented, and used in evaluation studies of various vehicle model configurations and different road-surface conditions. It was found that the overall dynamics is described similarly for both the high- and low-complexity models, as well as for various road-surface conditions.

If more information about the surroundings is available, the best control actions might differ from the ones in traditional safety systems. This is also studied, where the fundamental control strategies of classic electronic stability control is compared to the optimal strategy in a safety-critical scenario. It is concluded that the optimal braking strategy not only differs from the traditional strategies, but actually counteracts the fundamental intentions from which the traditional systems are based on.

In contrast to passenger cars, heavy trucks experience other characteristics due to the different geometric proportions. Rollover is one example, which has to be considered in critical maneuvering. Model configurations predicting this phenomenon are investigated using optimal control methods. The results show that the simple first go-to models have to be constrained very conservatively to prevent rollover in more rapid maneuvers.

In vehicle systems designed for path following, which has become a trending topic with the expanding area of automated driving, the requirements on vehicle modeling can be very high. These requirements ultimately depend on several various properties, where the path restrictions and path characteristics are very influential factors. The interplay between these path properties and the required model characteristics is here investigated. In situations where a smooth path is obtained, low-complexity models can suffice if path deviation tolerances are set accordingly. In more rapid and tricky maneuvers, however, vehicle properties such as yaw inertia are found to be important.

Several of the included studies indicate that vehicle models of lower complexity can describe the overall dynamics sufficiently in critical driving scenarios, which is a valuable observation for future development.

Place, publisher, year, edition, pages
Linköping University Electronic Press, 2016. 16 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1763
National Category
Control Engineering Vehicle Engineering
Identifiers
urn:nbn:se:liu:diva-127798 (URN)10.3384/diss.diva-127798 (DOI)978-91-7685-771-7 (ISBN)
Public defence
2016-06-10, Planck, Fysikhuset, Campus Valla, Linköping, 10:15 (English)
Opponent
Supervisors
Funder
VINNOVAeLLIIT - The Linköping‐Lund Initiative on IT and Mobile CommunicationsSwedish Research Council
Available from: 2016-05-25 Created: 2016-05-12 Last updated: 2016-05-25Bibliographically approved

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Lundahl, KristofferÅslund, JanNielsen, Lars

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