Access to cloud data improves fuel efficiency
The 48V split-level power supply for passenger cars has become synonymous with a new generation of mild hybridisation. One of the main features of this approach is a combined starter and generator which is no longer engaged by a pinion in the ring gear, but via a belt drive. This design makes the system very responsive in stop-and-go traffic situations: Since it can restart the engine within less than 0.2 seconds it is worthwhile switching off the engine even during short stops, leading to lower fuel combustion and likewise lower CO2 emission.
“The charm of connected energy management lies in the fact that we can optimise the driving strategy of the vehicle in terms of energy efficiency just by using an improved data basis”, said Oliver Maiwald, Head of Technology & Innovations at Continental’s Powertrain Division. “These data enable the electronic control unit to calculate which combination of unpowered coasting and energy recuperation achieves the best combination of battery charging status an low friction losses of the vehicle.
The technology has been demoed on a production model Volkswagen Golf with a 1.2 litre gasoline engine to which the components of the 48V hybrid drive have been added without significantly modifying the vehicle’s architecture. The combination of 48-V hybridisation and connection to a cloud-based topology data repository – in Continental phrasing, eHorizon – gives the driver the advantage of better fuel economy while at the same time making the vehicle more agile because of the electromotive support from the hybrid powertrain.
The reason why the 48V Eco Drive demonstration vehicle exhibited such a high energy efficiency was twofold: First, the vehicle recuperated energy when decelerating, transforming kinetic energy in electricity. Second, the hybrid 48V technology enables a driving strategy in which the combustion engine was switched off very frequently. This driving strategy, called coasting contributes significantly to low fuel consumption. At the end of such a coasting phase the engine is re-started very silently and quickly. Both strategies – recuperation and coasting – require certain trade-offs since they are competing in a certain way.
Previous systems meet their decision about the balance between recuperation and soaring based on static vehicle data. The dynamic eHorizon connects the vehicle to the back-end where dynamic data are fed into the loop, such as traffic situation data, or topology data. “The connectivity to the cloud allows us to utilise dynamic information regarding traffic flow and other events for the energy management”, says Ralf Lenninger, head of Innovation and strategy at Continental. If the trajectory is known – through navigation data or self-learning algorithms – the Eco Drive control unit can make forward-looking decisions as to when is the best time for coasting or for recuperation. As an example, the system can generate an alert to the driver to take toe foot off the pedal early because he is approaching a stop point. Thus, the vehicle can continue coasting for a relatively long time and in the final phase it can start recuperating energy. Depending on the altitude profile of the route as well as of curves and intersections, the driving style can be optimised automatically. An estimate of the fuel savings effect lies around 2 to 3 percent. This does not look overly impressing, but one should consider that it refers solely to the additional effect through utilising the cloud-based dynamic data. The static system per se is estimated to reduce fuel consumption by up to to 15 percent.