Evaluating implement-induced CoG shifts on tractor rollover stability: A multibody dynamics and experimental study across different machine orientations

• Multi-body dynamics model validated with real multidirectional rollover tests. • CoG shifts in three axes were simulated in 13 different equipment scenarios. • The highest rollover risk for vineyard tractors is close to lateral orientations. • Lateral and vertical CoG shifts affect stability more than longitudinal shifts. • High positioned equipment significantly reduces the lateral rollover threshold. 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 centre-of-gravity (CoG), sloping grounds and mass distribution. Current ISO standards cover lateral stability tests but 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 multi-body 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 testing ± 175° orientation and 55° tilt angles. Results consistently yielded underestimated results (favouring 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 analysed 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 behaviour.