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Directional stability of buses under influence of crosswind gusts
KTH, Superseded Departments, Aeronautical and Vehicle Engineering. (Fordonsdynamik)
2004 (English)In: Vehicle System Dynamics, ISSN 0042-3114, Vol. 41, 93-102 p.Article in journal (Refereed) Published
Abstract [en]

Incidents with heavy vehicles have put the issue of directional stability of buses under influence of crosswind gusts into focus. In this work the directional stability of buses when exposed to crosswind gusts has been investigated by using a MBS vehicle model combined with a generalised crosswind gust model and results from static wind tunnel measurements. The simulations carried out show the importance of the aerodynamic properties of buses as well as the importance of a proper weight distribution. It is also shown how important the driver model is in order to get realistic directional deviation in simulations and thereby also how important the driver is in order to keep the directional deviation to a minimum in real life situations.

Place, publisher, year, edition, pages
London: Taylor & Francis , 2004. Vol. 41, 93-102 p.
Keyword [en]
Aerodynamics; Automobile drivers; Computer simulation; Mathematical models; Safety factor; Steering; Wind effects; Wind tunnels
National Category
Vehicle Engineering
Identifiers
URN: urn:nbn:se:kth:diva-10384OAI: oai:DiVA.org:kth-10384DiVA: diva2:216418
Note
QC 20100722Available from: 2009-05-08 Created: 2009-05-08 Last updated: 2010-08-17Bibliographically approved
In thesis
1. Assessment of crosswind performance of buses
Open this publication in new window or tab >>Assessment of crosswind performance of buses
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

When driving a vehicle on the road, the driver has to compensate continuously for small directional deviations from the desired course due to disturbances such as crosswinds, road irregularities and unintended driver inputs. These types of deviations have a tiring effect on the driver and should therefore be minimised. When the magnitude of these disturbances increases, especially with crosswind, the directional deviation might become so large that the driver will have difficulties in compensating for it, and will thereby affect the traffic safety. The objective of this research work is to increase the understanding of the crosswind sensitivity of buses and to find solutions to the problem of improving the safety of buses with respect to crosswind performance. The work presented in this thesis contributes to increased knowledge about the directional stability of buses under the influence of crosswind gusts through parameter studies using detailed vehicle simulation models, through full-scale experiments and through studies of the effect of steering feel on the subjective and objective evaluation of crosswind performance.

A natural crosswind gust model has been derived from wind tunnel measurements and implemented in a multi-body dynamics simulation tool. The aerodynamic loads of the crosswind gust model have been applied on a detailed vehicle model and the behaviour of the vehicle model has been studied for various vehicle configurations in both open- and closed-loop manoeuvres. The vehicle model, with parameters corresponding to real vehicle data, has been validated and the agreement with measurements is good. A method for estimating the aerodynamic loads on a bus due to crosswind on a road section is also presented. Aerodynamic loads under real conditions were estimated using this method and these data were thereafter used in a study where the effect of steering feel on the subjective and objective evaluation of crosswind performance was investigated using a moving-base driving simulator, with the aim of finding a relationship between steering feel and crosswind sensitivity.

The thesis covers the influence of changing chassis-related parameters and aerodynamics-related parameters on the crosswind sensitivity, as well as the influence of the setting of the steering system on the crosswind performance of the driver-vehicle system. The results identify areas of high potential for improving the crosswind sensitivity of buses, such as the centre of gravity location and the yaw moment overshoot at gust entry. Furthermore, the study shows the importance of having a vehicle that facilitates prompt driver corrections for reducing the lateral deviation under crosswind excitation; i.e. it is shown that a steering system with the possibility of changing the yaw rate gradient referencing the steering-wheel input when the vehicle is subjected to a sudden crosswind has a good potential for improving the crosswind performance of the driver-vehicle system.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. vii, 58 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2009:25
Keyword
crosswind, buses, steering feel, directional stability, subjective, objective, aerodynamic load
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-10382 (URN)978-91-7415-316-3 (ISBN)
Public defence
2009-05-29, D1, KTH, Lindstedtsvägen 17, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20100722Available from: 2009-05-14 Created: 2009-05-08 Last updated: 2010-07-22Bibliographically approved

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