The gear shifting strategies strongly influence the vehicle fuel consumption because they change the powertrain inertia and the engine operation point. The literature normally presents gear shifting strategies based on the engine power and torque to improve the vehicle acceleration performance. Strategies based on fuel economy are difficult to determine due to a large number of factors that influence the engine behavior such as the available transmission ratios, required acceleration and vehicle speed. In this paper it was evaluated the influence of the addition of more gear ratios in the vehicle gearbox, which initially contains five available gear ratios. For each proposed gearbox configuration, the gear shifting strategy was optimized through an algorithm developed to improve the engine fuel consumption in the Brazilian standard urban driving cycle NBR6601. The simulations were performed by means of co-simulation between the multibody dynamics software AdamsTM (where is located the model based on a conventional 1.0L vehicle) and Matlab/SimulinkTM (where is implemented the vehicle longitudinal dynamics equations). The optimization algorithm elaborated in MatlabTM utilizes previous simulations results, stored in a database, to compare them with the results obtained performing new strategies.
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