A Tire Model for Off-Highway Vehicle Simulation on Short Wave Irregular Terrain

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