Browse Publications Technical Papers 2011-01-1014

Holistic Vehicle Energy Management - Moving Towards CAFE's Target 2011-01-1014

EPA and NHTSA have harmonized Regulations for Greenhouse Gas (GHG) emissions and Corporate Average Fuel Economy (CAFE) for model year (MY) 2012-16, published on April 1st, 2010. This requirement applies to all passenger cars and light trucks. Therefore the reduction of CO₂ emissions will be a major challenge for the automotive industry in the coming years to achieve the targets (GHG & CAFE) of 250 g/mi CO₂ and 35.5 miles per gallon (mpg) for MY 2016. In addition to combustion engine improvements, vehicle energy management and operating strategies offer a huge potential to reduce CO₂ emissions through innovative electronic systems.
The paper will show a possible implementation of a holistic vehicle energy management system including the operating strategy "Free wheeling." Starting from a top-down approach, we have developed operating strategies that offer the possibility to optimize the energy usage of the entire system. Energy recuperation and advanced Stop/Start system are the main elements of the operating strategies.
Design of new power net architectures is necessary to tackle the requirements of the new systems. To achieve the same level of reliability the vehicle systems and components must be adapted accordingly to allow engine stop for vehicle speed not equal to zero. The evaluation of the energy management strategies are based on a "virtual" average CAFE passenger car. This vehicle is investigated in simulating the driving cycles FTP-75 and HWFET. The feasibility of the 35.5 mpg target will be shown.


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