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Optimal Braking Patterns and Forces in Autonomous Safety-Critical Maneuvers
Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.ORCID-id: 0000-0003-4034-2868
2018 (engelsk)Licentiatavhandling, med artikler (Annet vitenskapelig)
Abstract [en]

The trend of more advanced driver-assistance features and the development toward autonomous vehicles enable new possibilities in the area of active safety. With more information available in the vehicle about the surrounding traffic and the road ahead, there is the possibility of improved active-safety systems that make use of this information for stability control in safety-critical maneuvers. Such a system could adaptively make a trade-off between controlling the longitudinal, lateral, and rotational dynamics of the vehicle in such a way that the risk of collision is minimized. To support this development, the main aim of this licentiate thesis is to provide new insights into the optimal behavior for autonomous vehicles in safety-critical situations. The knowledge gained have the potential to be used in future vehicle control systems, which can perform maneuvers at-the-limit of vehicle capabilities.

Stability control of a vehicle in autonomous safety-critical at-the-limit maneuvers is analyzed by the use of optimal control. Since analytical solutions of the studied optimal control problems are intractable, they are discretized and solved numerically. A formulation of an optimization criterion depending on a single interpolation parameter is introduced, which results in a continuous family of optimal coordinated steering and braking patterns. This formulation provides several new insights into the relation between different braking patterns for vehicles in at-the-limit maneuvers. The braking patterns bridge the gap between optimal lane-keeping control and optimal yaw control, and have the potential to be used for future active-safety systems that can adapt the level of braking to the situation at hand. A new illustration named attainable force volumes is introduced, which effectively shows how the trajectory of a vehicle maneuver relates to the attainable forces over the duration of the maneuver. It is shown that the optimal behavior develops on the boundary surface of the attainable force volume. Applied to lane-keeping control, this indicates a set of control principles similar to those analytically obtained for friction-limited particle models in earlier research, but is shown to result in vehicle behavior close to the globally optimal solution also for more complex models and scenarios.

sted, utgiver, år, opplag, sider
Linköping: Linköping University Electronic Press, 2018. , s. 19
Serie
Linköping Studies in Science and Technology. Licentiate Thesis, ISSN 0280-7971 ; 1804
HSV kategori
Identifikatorer
URN: urn:nbn:se:liu:diva-147719DOI: 10.3384/lic.diva-147719ISBN: 9789176853016 (tryckt)OAI: oai:DiVA.org:liu-147719DiVA, id: diva2:1204256
Presentation
2018-05-18, Ada Lovelace, B-huset, Campus Valla, Linköping, 10:15 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2018-05-07 Laget: 2018-05-07 Sist oppdatert: 2019-05-02bibliografisk kontrollert
Delarbeid
1. Formulation and interpretation of optimal braking and steering patterns towards autonomous safety-critical manoeuvres
Åpne denne publikasjonen i ny fane eller vindu >>Formulation and interpretation of optimal braking and steering patterns towards autonomous safety-critical manoeuvres
2018 (engelsk)Inngår i: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 57, nr 8, s. 1206-1223Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Stability control of a vehicle in autonomous safety-critical at-the-limit manoeuvres is analysed from the perspective of lane keeping or lane changing, rather than that of yaw control as in traditional ESC systems. An optimal control formulation is developed, where the optimisation criterion is a linear combination of the initial and final velocity of the manoeuvre. Varying the interpolation parameter in this formulation turns out to result in an interesting family of optimal braking and steering patterns in stabilising manoeuvres. The two different strategies of optimal lane-keeping control and optimal yaw control are shown to be embedded in the formulation and result from the boundary values of the parameter. The results provide new insights and have the potential to be used for future safety systems that adapt the level of braking to the situation at hand, which is demonstrated through examples of how to exploit theresults.

sted, utgiver, år, opplag, sider
Taylor & Francis, 2018
Emneord
Vehicle stability, yaw control, lane keeping, lane change, avoidance manoeuvre, at-the-limit
HSV kategori
Identifikatorer
urn:nbn:se:liu:diva-152896 (URN)10.1080/00423114.2018.1549331 (DOI)000470891200008 ()
Forskningsfinansiär
Knut and Alice Wallenberg Foundation
Merknad

Funding agencies: Swedish Government (Sveriges Regering); Wallenberg AI, Autonomous Systems and Software Program (WASP) (Knut och Alice Wallenbergs Stiftelse) - Knut and Alice Wallenberg Foundation

Tilgjengelig fra: 2018-11-27 Laget: 2018-11-27 Sist oppdatert: 2019-07-15bibliografisk kontrollert
2. Attainable force volumes of optimal autonomous at-the-limit vehicle manoeuvres
Åpne denne publikasjonen i ny fane eller vindu >>Attainable force volumes of optimal autonomous at-the-limit vehicle manoeuvres
2019 (engelsk)Inngår i: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, s. 1-22Artikkel i tidsskrift (Fagfellevurdert) Epub ahead of print
Abstract [en]

With new developments in sensor technology, a new generation of vehicle dynamics controllers is developing, where the braking and steering strategies use more information, e.g. knowledge of road borders. The basis for vehicle-safety systems is how the forces from tyre–road interaction is vectored to achieve optimal total force and moment on the vehicle. To study this, the concept of attainable forces previously proposed in literature is adopted, and here a new visualisation technique is devised. It combines the novel concept of attainable force volumes with an interpretation of how the optimal solution develops within this volume. A specific finding is that for lane-keeping it is important to maximise the force in a certain direction, rather than to control the direction of the force vector, even though these two strategies are equivalent for the friction-limited particle model previously used in some literature for lane-keeping control design. More specifically, it is shown that the optimal behaviour develops on the boundary surface of the attainable force volume. Applied to lane-keeping control, this observation indicates a set of control principles similar to those analytically obtained for friction-limited particle models in earlier research, but result in vehicle behaviour close to the globally optimal solution also for more complex models and scenarios.

sted, utgiver, år, opplag, sider
Taylor & Francis, 2019
Emneord
Active safety, force vectoring, vehicle dynamics control, tyre–road interaction, vehicle manoeuvre strategy
HSV kategori
Identifikatorer
urn:nbn:se:liu:diva-156638 (URN)10.1080/00423114.2019.1608363 (DOI)000470461700001 ()2-s2.0-85064738528 (Scopus ID)
Merknad

Funding agencies: Swedish Government; Wallenberg AI, Autonomous Systems and Software Program (WASP) - Knut and Alice Wallenberg Foundation

Tilgjengelig fra: 2019-05-02 Laget: 2019-05-02 Sist oppdatert: 2019-07-03bibliografisk kontrollert

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