ABSTRACT The energy management of a hybrid vehicle defines the vehicle power flow that minimizes fuel consumption and exhaust emissions. In a combined hybrid the complex architecture requires a multi-input control from the energy management. A classic optimal control obtained with dynamic programming shows that thanks to the high efficiency hybrid electric variable transmission, energy losses come mainly from the internal combustion engine. This paper therefore proposes a sub-optimal control based on the maximization of the engine efficiency that avoids multi-input control. This strategy achieves two aims: enhanced performances in terms of fuel economy and a reduction of computational time. INTRODUCTION Reducing fuel consumption and exhaust emissions in transportation is a major challenge for car manufacturers. The full hybrid vehicle is one of the possible architectures to limit CO2 emission. Hybrid-based solutions have to be carefully studied and optimized in order to carry out robust comparisons with zero-emission vehicles. The combined hybrid also called series-parallel hybrid or power-split hybrid, is the most efficient one in terms of energy consumption. This configuration needs a complex transmission with a mechanical link and an electrical link. Well-known combined hybrid applications are Toyota THS [ 1], Ford FHS e-CVT [ 2] and GM/Daimler/Chrysler/BMW Global Hybrid Cooperation (AHS2) [ 3]. A comparison of these hybrid electric continuousvariable transmissions can be found in [ 4]. This paper discuss about a continuous electrical variable transmission [ 5] which can be easily connected to a power battery in order to propose a high efficiency combined hybrid. This hybrid transmission offers many degrees of freedom to fulfill the torque at the wheel required by the driver. It is not straightforward to choose the best operating point of this derivative hybrid architecture because many manipulated variables such as the internal combustion engine torque, the engine speed or the battery power can be considered. Energy management has to set two manipulated variables, which determine the vehicle set point achieving torque required by the driver. When the torque and the speed at the wheel along a route or a driving cycle are perfectly known, a dynamic programming algorithm can find the optimal control that minimizes fuel consumption. The analysis of this offline optimal control policy shows that thanks to the high efficiency transmission, energy losses come mainly from the internal combustion engine. With this information, a new control based on the maximal engine efficiency is proposed. An optimal operating point line, which minimizes the engine brake specific fuel consumption for a given thermal power, is used to determine one of the manipulated variables. Thus, this strategy avoids multi-input control, an important asset for online optimization. The first section describes the high efficiency hybrid electric variable transmission and the advantages of a dual-mode structure. The second section presents the hybrid control architecture. The third section is devoted to the optimal Energy Management of a High Efficiency Hybrid Electric Automatic Transmission2010-01-1311 Published 04/12/2010 Maxime Debert, Guillaume Colin and Yann Chamaillard Univ. D'Orleans Michel Mensler and Ahmed Ketfi-cherif Renault Lino Guzzella ETHZ Copyright © 2010 SAE InternationalDownloaded from SAE International by Brought to you by the University of Kansas (Technical reports: 1998 to Present), Saturday, August 25, 2018control obtained with dynamic programming and the study of energy losses in prime movers. In the fourth section, a strategy based on the internal combustion engine maximum efficiency is proposed. Finally, the sub-optimal control is compared to the optimal control on different driving cycles. HYBRID TRANSMISSION This paper presents a high efficiency continuous electric variable transmission connected with a power battery. The transm