Proceedings of the ASME 2014 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference IDETC/CIE 2014 August 17-20, 2014, New York, United States DETC2014-34897 OPTIMAL DUAL-MODE HYBRID ELECTRIC VEHICLE POWERTRAIN ARCHITECTURE DESIGN FOR A VARIETY OF LOADING SCENARIOS Alparslan Emrah Bayrak Mechanical Engineering University of Michigan Ann Arbor, Michigan, 48109 Email: bayrak@umich.eduYi Ren Mechanical Engineering University of Michigan Ann Arbor, Michigan, 48109 Email: yiren@umich.eduPanos Y. Papalambros Mechanical Engineering University of Michigan Ann Arbor, Michigan, 48109 Email: pyp@umich.edu ABSTRACT A hybrid-electric vehicle powertrain architecture consists of single or multiple driving modes, i.e., connection arrangements among engine, motors and vehicle output shaft that determine distribution of power. While most architecture development work to date has focused primarily on passenger cars, interest has been growing in exploring architectures for special-purpose vehicles such as vans or trucks for civilian and military applica- tions, whose weights or payloads can vary significantly during operations. Previous findings show that the optimal architecture can be sensitive to vehicle weight. In this paper we investigate architecture design under a distribution of vehicle weights, us- ing a simulation-based design optimization strategy with nested supervisory optimal control and accounting for powertrain com- plexity. Results show that an architecture under a single load has significant differences and lower fuel efficiency than an architec- ture designed to work under a variety of loading scenarios. 1 Introduction A powertrain driving mode of a Hybrid-Electric Vehicle (HEV) is defined as the the connection arrangement among en- gine, Motor/Generators (MG) and vehicle output shafts. For ex- ample, the Toyota Prius powertrain has one driving mode repre- sented by a lever analogy, as shown in Figure 1. Here the Plan- etary Gear (PG) is represented by the lever. It splits the power demand from the vehicle output shaft into the engine and MGs. Address all correspondence to this author. FIGURE 1 . The Toyota Prius Hybrid System in the lever representa- tion; four powertrain components (the engine, two MGs and the vehicle output shaft) are connected to PG nodes. We refer to a powertrain architecture as a collection of driving modes. For instance, the Chevrolet V olt has a four-mode archi- tecture, which uses clutches to switch among modes, in order to achieve high fuel efficiency and driveability in different driving conditions such as launching (high-torque low-speed) and high- way cruising (low-torque high-speed). Previous research has addressed supervisory control of en- gine and MG operations as well as mode-shifting strategies to improve fuel efficiency and driveability for a given architec- ture [1–3]. The attendant question is whether some architectures are more advantageous for some types of vehicles. For example, one might question whether architectures developed for passen- ger cars and light trucks are suitable for heavy trucks, delivery vans or military vehicles with different specifications and duty (driving) cycles. 1 Copyright c 2014 by ASMEPrevious work explored this question using a heuristic search algorithm to find the near-optimal powertrain architec- ture for given driving cycle and vehicle specifications [4]. It was shown that the solution can be sensitive to vehicle weight. For example, a significantly different solution was found when we changed the vehicle weight from 1400kg to 1600kg. Motivated by this observation, this paper investigates the optimal power- train architecture design under a distribution of vehicle weights (or payloads). The paper offers two contributions: (1) We show that an ar- chitecture designed to accommodate a variety of vehicle weights (payloads) has better averaged fuel economy than architectures designed for specific weights (payloads);