Abstract
KEYWORDS:
agricultural tractor, front loader, oscillating dynamic model, oscillating mathematical model
ABSTRACT:
Agricultural tractors equipped with front loaders are largely used for loading and manipulation operations of products and materials in agriculture. For this purpose the oscillating arm of the front loader is endowed with various working elements (buckets, forks).
Due to road unevenness, during the travelling of the tractor equipped with a charged front loader in transport position oscillating motions of the tractor body are generated, which are transmitted to the driver, who is consequently subjected to intensive strain. Further, these oscillations affect tractor-travelling safety, which is influenced mostly by the strong dynamic variation of the dynamic loads on the axles. Consequently, during high speed travelling of the tractor equipped with a front loader the load on the rear axle can be significantly diminished, causing the rear wheels to lose contact with the road surface with unpredictable consequences on the longitudinal stability of the moving tractor. By mounting the front loader onto the tractor body, additional mass, elasticity and damping is generated in the oscillating system of the tractor.
For the study of the oscillating process, the paper introduces an equivalent oscillating dynamic model of the system consisting of the tyre-wheel tractor and the front loader with a hydraulically driven jointed arm. In establishing the dynamic model the following simplifications are considered; the rear part of the front loader (the counter-weight) is attached to the tractor mass, and the masses of the charge, the bucket and the oscillating arm of the loader are taken into consideration as an equivalent concentrated mass. The elastic and damping characteristics of the tyres and of the joint of the loader arm and the tractor body are also taken into consideration. Based on the dynamic model, the mathematical model of the tractor oscillating motion is developed, allowing computer simulation of the oscillating motion in the longitudinal plane of the tractor, under various travelling conditions.