COMPARISON OF THE PHYSICAL AND EMPIRICAL APPROACH TO MODELLING OF QUASISTATIC ENVELOPING PROPERTIES OF THE TRACTOR TIRE

Vibration properties of agricultural tractors are important indicator of their overall performances. Most important excitation source comes from pronounced short-wavelength road undulations, which are typical for unprepared off-road terrains generally dealt with by tractors. Low-pass geometric filtering of road profile done by tire thereby defines effective vibration input. Appropriate tire model that is able to account for this phenomenon is needed in order to optimize tractor vibration properties in early stage of development, by means of computer aided simulations with virtual prototype. To reduce tire model complexity and therefore improve simulation speed, yet achieving satisfactory accuracy, one possible approach is to separate tire model into two parts, one describing tire enveloping properties on the short-wavelength road input and the other one for tire elasticity with single-point contact. Enveloping model thereby generates effective excitation for contact point. In this paper two quasi-static tire enveloping models were derived. One of them is physically based and the other one is novel empirical model. Performances of both models are represented and compared with one another as well as with results of the physical experiment. Good agreement with experimental data is achieved in both cases. It was concluded that, in view of computational efficiency, empirical model manifested supremacy over physical model while the other one achieved greater flexibility regarding variations of influential parameters.