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Langer T.H.,A S Hydrema Produktion | Kristensen L.B.,Hydrema Produktion Weimar GmbH | Mouritsen O.A.,University of Aalborg | Hansen M.R.,University of Agder
SAE Technical Papers

Manufacturers of construction machinery are challenged in several ways concerning dynamic loads. Considering off-highway dump trucks that travel through high amplitude short wave irregular terrain with considerable speed two aspects concerning dynamics are important. The first is the legal requirements that prescribe the maximum limit on the vibration exposure on the operator which is a measure for ride comfort. The second is the importance of knowing the dynamic loading of the structural parts. In order to use the wide variety of computer-aided design tools to size and optimize mechanical joints, spring-damper elements and the welded structures it is crucial to have information on the time history of the loads. For trucks carrying payloads the most important load contribution is undoubtedly the reaction forces between terrain and tires. By use of virtual prototypes it is possible to evaluate accelerations of different machine parts and reaction forces in joints. Hence it is possible to find loads for sizing components and structures and prevent fatigue, and also the influence of design changes on ride comfort can be evaluated. This poses a non-trivial challenge: To be able to describe the tire ground interaction for big off-road tires on short wave irregular terrain. In this paper a simple tire model combining the well known slip theory and a displaced volume approach is presented. A non-gradient optimization routine is applied for parameter identification by minimizing the difference between simulated data and experimental data obtained from full vehicle testing. The experimental work is carried out by letting a dump truck pass a set of well defined obstacles. Based on the obtained agreement between simulated and measured results the tire model is considered suitable for describing the tire ground interaction and, subsequently, reliable for a model based evaluation of the dynamic loads. Copyright © 2010 SAE International. Source

Langer T.H.,A S Hydrema Produktion | Iversen T.K.,A S Hydrema Produktion | Andersen N.K.,Mercantec | Mouritsen O.O.,University of Aalborg | Hansen M.R.,University of Agder
International Journal of Industrial Ergonomics

Whole-body vibration is a health hazard for operators of construction machinery. The level of whole-body vibration exposure on the operator is governed by three different factors; performance of the suspension system of the machine, planning of the work and the skills of the operator.In this research work it is investigated whether there is a potential in bringing down the level of whole-body vibration exposure by educating operators of backhoe loaders. This is carried out by an experimental setup. Six experienced operators participated in the experiments carried out on two different sizes of backhoe loaders. Each operator had to complete three different tasks without any kind of instructions. Subsequently they got a short education on eco-driving and vibration avoidance and carried out the tasks once more. Time duration, whole-body vibration exposure and fuel consumption was registered before and after education.The result of the short education was an average reduction in the whole-body vibration exposure of 22.5%. And for all completed tasks expect one a considerably fuel saving was obtained too - up to 38%. This experiment demonstrates that education of the operator will improve the occupational health and save fuel. The results also indicate that these improvements can be obtained without reduction in productivity as the instructions become a habit for the operators. Thus it is profitable for the employer to educate the employees operating construction machinery.Relevance to industry: The findings of this work is highly relevant to the construction industry. It shows a great potential in reducing damaging vibration and at the same time reduce fuel consumption. It also emphasizes the need for better education of machine operators. © 2012 Elsevier B.V. Source

Langer T.H.,A S Hydrema Produktion | Iversen T.K.,A S Hydrema Produktion | Mouritsen O.O.,University of Aalborg | Bak M.K.,University of Agder | Hansen M.R.,University of Agder
International Journal of Vehicle Design

Tyre modelling is a major challenge when using time domain multibody simulation models to evaluate ride comfort on off-highway commercial vehicles. Further, parameters for these big tyres are difficult to obtain and thus, commercial car tyre models are difficult to apply. In this research work, a simple vertical tyre model for off-highway ride comfort evaluation is suggested. A displaced volume approach has been developed and combined with the slip theory to yield a tyre model that can be characterised by only three parameters. Full scale measurements on a dump truck have been carried out. Force responses from measurements are compared to the simulation results. Acceleration responses and the level of whole-body vibrations have also been compared. © 2014 Inderscience Enterprises Ltd. Source

Langer T.H.,A S Hydrema Produktion | Iversen T.K.,A S Hydrema Produktion | Mouritsen O.O.,University of Aalborg | Ebbesen M.K.,University of Agder | Hansen M.R.,University of Agder
Structural and Multidisciplinary Optimization

Suspension systems on commercial vehicles have become an important feature meeting the requirements from costumers and legislation. The performance of the suspension system is often limited by available catalogue components. Additionally the suspension performance is restricted by the travel speed which highly influences the ride comfort. In this article a suspension system for an articulated dump truck is optimized in sense of reducing elapsed time for two specified duty cycles without violating a certain comfort threshold level. The comfort threshold level is here defined as a whole-body vibration level calculated by ISO 2631-1. A three-dimensional multibody dynamics simulation model is applied to evaluate the suspension performance. A non-gradient optimization routine is used to find the best possible combination of continuous and discrete design variables including the optimum operational speed without violating a set of side constraints. The result shows that the comfort level converges to the comfort threshold level. Thus it is shown that the operational speed and hence the operator input influences the ride comfort level. Three catalogue components are identified by the optimization routine together with a set of continuous design variables and two operational speeds one for each load case. Thus the work demonstrates handling of human factors in optimization of a mechanical system with discrete and continuous design variables. © 2013 Springer-Verlag Berlin Heidelberg. Source

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