Evaluation of the stability of an articulated farm tractor using mounted implements on hillsides

When introducing a new farm tractor in the market, manufacturers undergo a tight homologation path under the supervision of the OECD centres technicians. Two of the most requested tests, although not mandatory for the commercialization of a tractor, are the individuation of the centre-of-gravity and of the lateral rollover angle on a tilting platform. The results of these tests are very interesting for the technical characterization of a vehicle but still far from its real working conditions, even if the tilting platform test forecasts, for example, the presence of fuel in the tank and the use of some weights to simulate the driver. Indeed, in this last test, no mounted implement (or equivalent mass) is connected to the tractor, hence limiting a lot the use of the results of the described tests. Therefore, a numeric stability simulator was developed to overcome this problem, thus managing the variety of the possible implements to be connected to a tractor and giving the farmers effective indications concerning their vehicles’ safety while working on hillsides. This simulator, based on a Newtonian approach, is able to compute the stability of a vehicle formed by a tractor and an implement. It was used to verify the possibility of safety using some common mounted implements with a compact wheeled articulated tractor, specifically designed to work within terraced orchards/vineyards, common in mountain areas. This tractor was chosen because of its particular architecture: it gives the tractor a higher agility and a shorter turning radius than conventional tractors with the same dimensions, but also a very different stability behaviour, maybe not completely predictable in all situations by inexperienced drivers.