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Influence of tyre properties on the ride dynamics of heavy off-road vehicles
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.ORCID iD: 0000-0001-8928-0368
2011 (English)Conference paper, Published paper (Other academic)
Abstract [en]

Wheeled earthmoving machines are a class of off-road vehicles that are typically equipped withlarge and soft tyres to obtain sufficient traction and flotation on unpaved surfaces. Theunsuspended mass is typically larger than for road vehicles. This indicates that the tyreproperties will affect not only the dynamics of the wheels and axles, but may also have asubstantial effect on the ride dynamics of the vehicle. This paper investigates how the tyrecharacteristics influence the optimal design of a wheel suspension for an off-road constructionmachine. Frequency domain analysis of a pitch and bounce model show that overallacceleration levels are significantly affected by tyre stiffness and damping, but that the tradeoffbetween pitch and bounce is unaffected by tyre properties although the main ride frequenciesare offset. Also, optimal suspension damping is fairly independent of the tyres. It is alsoinvestigated if a locked front axle suspension may be used in the loaded case, to simplifysuspension system design by using tyres as sole suspension elements. It is found that thisconfiguration leads to decreased ride quality, mainly due to the increased suspension stiffnessand lack of damping.

Place, publisher, year, edition, pages
2011.
National Category
Vehicle Engineering
Identifiers
URN: urn:nbn:se:kth:diva-33884OAI: oai:DiVA.org:kth-33884DiVA: diva2:418341
Conference
Joint 9th Asia-Pacific ISTVS Conference and Annual Meeting of Japanese Society for Terramechanics
Note
QC 20110531Available from: 2011-05-22 Created: 2011-05-22 Last updated: 2011-05-31Bibliographically approved
In thesis
1. 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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