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Agricultural tractors and their implements are at the basis of modern farming. Besides propulsion, in such system, most of the mechanical actuations are performed with a fluid power system that is highly power-dense and versatile, but has a low energy efficiency. This article first describes the challenges of the state-of-the-art hydraulic system that cause poor efficiency. Afterward, it proposes and demonstrates a solution that can significantly increase such efficiency without affecting the cost and functionality of the overall hydraulic control system. The proposed solution is based on a peculiar control approach to the hydraulic supply units that power the implement functions through the hydraulic remote connections. The approach is based on an impressed-pressure control methodology, as opposed to the traditional impressed flow method used in off-road machinery. The result is that the typical energy-inefficient pressure saturation conditions that often occur in common vehicles are mitigated and brought to a more efficient state. To support the development of the technology, the research takes into consideration the circuit of a 400-hp tractor and a 16-row planter. A simulation model of the hydraulic system of the two vehicles was implemented and validated against experiments. The model was then utilized to estimate the reduction in the energy consumption achieved by the proposed solution. Lab tests and field experiments of the proposed solutions applied to the reference tractor and planter system confirmed an overall 18% energy efficiency improvement.
Tian et al. (Sun,) studied this question.