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Snaking stability of articulated frame steer vehicles with axle suspension
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.ORCID iD: 0000-0001-8928-0368
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.ORCID iD: 0000-0002-4048-3452
2010 (English)In: International Journal of Heavy Vehicle Systems, ISSN 1744-232X, Vol. 17, no 2, 119-138 p.Article in journal (Refereed) Published
Abstract [en]

A known problem of articulated vehicles is that snaking oscillations may occur at high speed. For ride comfort reasons, it is desirable to introduce suspended axles on articulated vehicles such as wheel loaders which are traditionally built without wheel suspension. This paper investigates how this may affect the snaking stability, by studying the vehicle dynamic behaviour of a multibody simulation model with and without suspension. Results show that an axle suspension may have a slightly destabilising effect, although the difference is small and can be offset by a stiffer or more damped steering system.

Place, publisher, year, edition, pages
2010. Vol. 17, no 2, 119-138 p.
Keyword [en]
articulated vehicles, snaking stability, lateral stability, MBS, multibody simulations
National Category
Vehicle Engineering
Identifiers
URN: urn:nbn:se:kth:diva-8132DOI: 10.1504/IJHVS.2010.033178ISI: 000278964400002Scopus ID: 2-s2.0-77952414229OAI: oai:DiVA.org:kth-8132DiVA: diva2:13373
Note
QC 20101119 Uppdaterad från submitted till published (20101119).Available from: 2008-03-19 Created: 2008-03-19 Last updated: 2011-05-31Bibliographically approved
In thesis
1. Vehicle dynamic analysis of wheel loaders with suspended axles
Open this publication in new window or tab >>Vehicle dynamic analysis of wheel loaders with suspended axles
2008 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

The wheel loader is a type of engineering vehicle used primarily to move crude material over shorter distances. As the vehicle is designed without wheel suspension, wheel loader drivers are exposed to high levels of whole body vibration which influences ride comfort negatively. The work presented in this thesis has the aim to investigate the potential in adding an axle suspension to a wheel loader in order to reduce vibrations and increase handling quality. While suspended axles have great potential for improving ride comfort and performance, they will also necessarily affect the vehicle dynamic behaviour which is different in many aspects from that of passenger cars or other road vehicles: the wheel loader has a large pitch inertia compared to its mass, the axle loads vary considerably with loading condition, and the vehicle uses an articulated frame steering system rather than wheel steering. These issues must all be considered in the design process for a wheel loader suspension.

The effects of suspended axles on ride vibrations are analysed by simulating a multibody wheel loader model with and without axle suspension. Results from the simulations show that longitudinal and vertical acceleration levels are greatly reduced with axle suspension, but that the decrease in lateral acceleration is smaller. By reducing the roll stiffness lateral accelerations can be further reduced, although this may not be feasible because of requirements on handling stability. The pitching oscillation of the vehicle has also been studied as this is known to have a large influence on ride comfort. An analytical model is used to study the effect of front and rear suspension characteristics on the pitching response of the wheel loader, showing that a stiffer rear suspension is favourable for reducing pitching but also that a similar effect is attainable with a stiffer front suspension. Results are compared to multibody simulations which show the same trend as analytical predictions. By including a linearised representation of a hydropneumatic suspension in the models, it is also shown that favourable dynamic behaviour can be maintained when the vehicle is loaded by utilising the fact that suspension stiffness is increasing with axle load.

Articulated vehicles may exhibit lateral oscillations known as "snaking" when driven at high speed. The effect of suspended axles on these oscillations are analysed using a multibody simulation model of a wheel loader with an equivalent roll stiffness suspension model. It is found that the roll motion of the sprung mass has a slightly destabilising effect on the snaking oscillations. This effect is more pronounced if the body roll frequency is close to the frequency of the snaking motion, although this loss in stability can be compensated for by increasing the equivalent stiffness or damping of the steering system.

Together with existing vehicle dynamic theory and design rules, the studies reported in this work provide an insight into the specific issues related to suspension design for wheel loaders.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. vii, 54 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2008:15
Keyword
hjullastare, arbetsmaskin, fordonsdynamik, fordonsteknik
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-4677 (URN)978-91-7178-908-2 (ISBN)
Presentation
2008-04-03, D3, Lindstedsvägen 5, Stockholm, 10:15
Opponent
Supervisors
Note
QC 20101119Available from: 2008-03-19 Created: 2008-03-19 Last updated: 2010-11-19Bibliographically approved
2. Suspension design for off-road construction machines
Open this publication in new window or tab >>Suspension design for off-road construction machines
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Construction machines, also referred to as engineering vehicles or earth movers, are used in a variety of tasks related to infrastructure development and material handling. While modern construction machines represent a high level of sophistication in several areas, their suspension systems are generally rudimentary or even nonexistent. This leads to unacceptably high vibration levels for the operator, particularly when considering front loaders and dump trucks, which regularly traverse longer distances at reasonably high velocities. To meet future demands on operator comfort and high speed capacity, more refined wheel suspensions will have to be developed. The aim of this thesis is therefore to investigate which factors need to be considered in the fundamental design of suspension systems for wheeled construction machines.

The ride dynamics of wheeled construction machines are affected by a number of particular properties specific to this type of vehicle. The pitch inertia is typically high in relation to the mass and wheelbase, which leads to pronounced pitching. The axle loads differ considerably between the loaded and the unloaded condition, necessitating ride height control, and hence the suspension properties may be altered as the vehicle is loaded. Furthermore, the low vertical stiffness of off-road tyres means that changes in the tyre properties will have a large impact on the dynamics of the suspended mass. The impact of these factors has been investigated using analytical models and parameters for a typical wheel loader. Multibody dynamic simulations have also been used to study the effects of suspended axles on the vehicle ride vibrations in more detail. The simulation model has also been compared to measurements performed on a prototype wheel loader with suspended axles.

For reasons of manoeuvrability and robustness, many construction machines use articulated frame steering. The dynamic behaviour of articulated vehicles has therefore been examined here, focusing on lateral instabilities in the form of “snaking” and “folding”. A multibody dynamics model has been used to investigate how suspended axles influence the snaking stability of an articulated wheel loader. A remote-controlled, articulated test vehicle in model-scale has also been developed to enable safe and inexpensive practical experiments. The test vehicle is used to study the influence of several vehicle parameters on snaking stability, including suspension, drive configuration and mass distribution. Comparisons are also made with predictions using a simplified linear model.

Off-road tyres represent a further complication of construction machine dynamics, since the tyres’ behaviour is typically highly nonlinear and difficult to evaluate in testing due to the size of the tyres. A rolling test rig for large tyres has here been evaluated, showing that the test rig is capable of producing useful data for validating tyre simulation models of varying complexity.

The theoretical and experimental studies presented in this thesis contribute to the deeper understanding of a number of aspects of the dynamic behaviour of construction machines. This work therefore provides a basis for the continued development of wheel suspensions for such vehicles.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011. ix, 80 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2011:39
Keyword
construction machine, engineering vehicle, earth mover, wheel loader, vehicle dynamics, vehicle engineering, whole body vibrations, off-road vehicle, anläggningsmaskin, entreprenadmaskin, hjullastare, fordonsdynamik, fordonsteknik, helkroppsvibrationer, terrängfordon
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-33883 (URN)978-91-7501-040-3 (ISBN)
Public defence
2011-06-14, D2, Lindstedtsvägen 5, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
TrenOp, Transport Research Environment with Novel Perspectives
Note
QC 20110531Available from: 2011-05-31 Created: 2011-05-22 Last updated: 2012-06-12Bibliographically approved

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Drugge, LarsStensson Trigell, Annika

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