Control experiences and energetic optimization studies for a series hybrid electric vehicle

Among the research and development subjects of ENEA, an important theme is the study of innovative vehicles, of electric and hybrid-electric type, with high energy efficiency and low emissions. This paper deals with features and working methods throughout the roll bench testing of the ENEA hybrid Daily, a 6m series hybrid developed by ALTRA, IVECO and ANSALDO, equipped with a controller developed in collaboration between ENEA and University of Pisa, to evaluate the real effectiveness of different control algorithms in achieving significant fuel economy improvements. Two testing campaigns were performed, the first one at fixed generator and storage conditions, according to a number of European, American and Japanese urban driving cycles, the second one according to a fixed urban driving cycle, at different working conditions for generator set-point and storage state-of-charge. Results obtained during the first campaign, reported in previous papers and here partially resumed, demonstrated that it is possible to reduce fuel consumption with respect to the conventional version of the same vehicle. The second testing campaign demonstrated the need to correctly manage the battery state-of-charge, because of the great reduction in battery charging-discharging efficiency due to high current condition typical of HEV and the negative influence that high SOC levels demonstrated on motorgenerator operations. Starting by the experimental data, it was also possible to obtain an input-output energetic model of the system that enables us to find the generator operating points that match minimal specific fuel consumption for each value of the power average demand.