OPTIMIZING ENGINE DOWNSIZING AND DRIVING BEHAVIOUR IN CONVENTIONAL AND HYBRID POWERTRAINS FOR AUTONOMOUS DRIVING APPLICATIONS

The continuous increase in global CO2 emissions, together with more stringent vehicle emissions and fuel economy regulations around the world require innovative solutions and technologies to address these challenges. To this end, Connected and Automated Vehicles (CAV) are one pathway by which significant fuel economy improvements and emissions reductions may be simultaneously achieved. In this study, the potential fuel economy improvements stemming from improved driving behaviour, as well as dedicated engine rightsizing possible with CAVs, have been considered. This study focuses on two different powertrain configurations: a conventional gasoline engine driven powertrain, and a hybrid electric vehicle. To investigate the fuel economy improvement potential of CAVs via driving behaviour modifications, each cycle was gradually modified by smoothing speed fluctuations at several stages representing a range of driving behaviours, starting from those that would be possible on-road today, to those that would require a fully connected automated vehicle network. In addition to this, the optimal engine displacement with respect to fuel economy was found for each of the different scenarios by neglecting conventional performance metrics and focusing only on drive cycle requirements. Simulation results demonstrated potential fuel economy improvements for both conventional and hybrid powertrains, from 5% to 14% derived from improved driving behaviour, while improvements from 1% to 28% were possible with engine rightsizing, and improvements of 6% to 38% were possible by combining improved driving behaviour with engine rightsizing depending on the drive cycle considered. For driving scenarios requiring a fully connected autonomous network, simulation results predicted even larger potential fuel economy improvements, indicating significant benefits derived from implementation of CAVs in terms of fuel economy and vehicle CO2 emissions.