On the advantages of the new power-split infinitely variable transmission over conventional mechanical transmissions based on fuel consumption analysis

The use of power-split infinitely variable transmissions (PS-IVT) in off-road vehicles and, in particular, in agricultural machinery has recently increased considerably thanks to the high driving comfort they provide and the variable transmission ratios facilitating agricultural operations. Conventional mechanical transmissions are also still in use due to their high mechanical efficiency and cost-effective structure. Although the efficiency of the PS-IVT is known to be lower than that of the conventional transmission, it can reduce fuel consumption by allowing the control of internal combustion engine in an optimum way by allowing the continuous transmission ratio. This study is intended to obtain lower fuel consumption values by employing PS-IVT as compared to the conventional transmission. In order to determine the fuel consumption values to be obtained by two different types of transmission, GPS data of a real tractor at real time from the real user in real world conditions were collected, and the driving resistances for the considered vehicle were determined with the longitudinal vehicle dynamics model. Dynamometer test and theoretical calculations based on the kinematic model developed in our earlier study were carried out to determine the mechanical efficiencies of the conventional transmission and the PS-IVT respectively. Fuel consumption values obtained using different types of transmissions were compared in terms of mass by using a BSFC map of a four-cylinder common-rail turbo diesel engine. Fuel consumption simulations were performed in MATLAB environment, and two different power management strategies with eight different scenarios were evaluated. It is found that a reduction of 8.2% in fuel consumption compared with the conventional transmission can be achieved by the proper power management strategy for the PS-IVT.