Coasting As A Real Driving Function

Depending on the driving profile and without the aid of additional advanced driver assistance systems, mild hybrid vehicles with electrification of 48 V do not require the internal combustion engine for propulsion for up to a quarter of the driving time. The engine can therefore be disengaged and stopped, which – depending on the operating strategy – reduces actual consumption by up to 8 % on average. According to developments at Continental, additional potential savings can be achieved by predictive Energy Management (pEM). An overall technology view is required for drivers to understand and accept the vehicle behaviour.

- Antonio Arcati

COASTING BETWEEN FUNCTION AND DRIVER REACTION

Powertrain architectures that have already been moderately electrified, such as a 48 V mild hybrid, allow the internal combustion engine to be switched-off and disengaged from the power train, when it is not needed for propulsion of the vehicle. Particularly in more urban areas, this can be the case for up to a quarter of the driving time [1, 2]. If you want to reduce fuel consumption of a vehicle and therefore its CO2 emissions, coasting is one of the most efficient hybrid operating strategies that can be used to react to traffic and driving situations. Depending on the vehicle and E/E architecture in the C segment, coasting with a disengaged and switched-off engine (engine-off coasting) alone results in average CO2 savings of up to 8 % in urban areas and 5 % in extra-urban areas.

In accordance with EU regulation 443/2009 and 253/2014 (amendment to 510/2011), CO2 emission savings that are not considered by the applicable test cycle up to a maximum of 7 g of CO2/km can be claimed by vehicle manufacturers as eco-innovations [3, 4]. Eco-innovations therefore play a significant role in efforts to reduce the average CO2 emissions of a fleet to below the average EU limit value of 95 g of CO2/km for 2020. The CO2 savings resulting from coasting can be qualified in a modified NEDC [5] and, according to simulations, achieve similar CO2 savings in the real world.

Greater potential for savings and therefore minimisation of consumption in the real world can also be achieved by a supportive and predictive driving strategy approach combined with a coordinated interaction concept. Thanks to this driver support, the proportion of driving time spent coasting can reach up to 35 % with anticipatory driving strategy management, which leads to additional CO2 savings.