Design of Power-Split Hydrostatic CVT Agricultural Transmission for Enhanced Control and Efficiency

A newly conceived fully synchronized and full power-shift Output Coupled transmission for agricultural tractors was designed, based on the hypothesis of ideal components. This first version was simulated in a lumped parameter environment, including all the components of the transmission, the real hydraulic machines efficiencies, and a finite state machine based control system, to command hydraulic machines displacement and engagement/disengagement of clutches and synchronizers. The hydraulic transmission considered in the work is subjected to challenging operating conditions, which cause deviations from the ideal command profiles due to volumetric and hydromechanical efficiencies. In the second phase, the parameters of the transmission are optimized, obtaining an upgraded design. The new set of parameters substantially increase the performances of the hydrostatic units, moving the operating points to favourable conditions. The latter design is finally compared to the first one, focusing on the performance of both the hydrostatic units and the overall interconnected system.