Abstract
Tractor rollovers are the main cause of fatal accidents in the agricultural sector, especially in rugged vineyards and orchards. Vineyard tractors operating in narrow passages are likely to lose stability due to high center-of-gravity (CoG), sloping grounds and mass distribution. Current ISO standards cover lateral stability tests and do not take into account different orientations. The aim of this study is to investigate the effects of CoG shifts caused by various tractor-mounted implements on rollover stability of a narrow track vineyard tractor. First, the CoG position of a vineyard tractor was determined experimentally according to ISO 789-6 standards, and a rigid multibody dynamics (MBD) model was composed by using Adams/View 2022.3 accordingly. Static Phase 1 stability tests were simulated using the PAC2002 tire model and pivot axle kinematics. The model was validated using a special rollover platform capable of simulating ±175° orientation and 55° tilt angles. Results consistently yielded underestimated results (favoring safety) with a mean absolute percentage error (MAPE) of 11% compared to experimentally determined stability angles. To simulate stability changes influenced by implements, 13 different scenarios were analyzed by varying the CoG position along the longitudinal, lateral, and vertical axes at specific rates in the MBD environment. The results were evaluated using stability maps and the Rollover Stability Index (RSI). The findings showed that lateral and vertical CoG shifts significantly affected the rollover behavior.