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Modern military ground vehicles are dependent not only on armor and munitions, but also on their electronic equipment. Advances in battlefield sensing, targeting, and communications devices have resulted in military vehicles with a wide array of electrical and electronic loads requiring power. These vehicles are typically designed to supply this power via a main internal combustion engine outfitted with a generator. Batteries are also incorporated to allow power to be supplied for a limited time when the engine is off. It is desirable to use a subset of the battlefield electronics in the vehicle while the engine is off, in a mode called “silent watch.” Operating time in this mode is limited, however, by battery capacity unless an auxiliary power unit (APU) is used or the main engines are restarted.

North American sales of light duty trucks, including sport utility vehicles (SUV's), have now passed the 50% mark of total vehicles sold. This fact, along with the recent surge in gas prices, has drawn attention to the lower average fuel economy of this vehicle class. With possible changes to the light duty truck corporate average fuel economy (CAFE) standards looming on the horizon, vehicle manufacturers are looking for ways to improve the fuel economy of these vehicles without affecting performance or utility. One possible solution in accomplishing this objective is the 42 volt integrated starter-generator (ISG). The ISG offers the ability to reduce fuel consumption through the use of engine-off during coast-down and idle, early torque converter lockup with torque smoothing, regenerative braking, and electrical launch assist. It also boosts the onboard power generation and energy storage, allowing for increased vehicle electrical loads.

The purpose of this paper is to demonstrate how simulation can impact the design process for an integrated starter generator (ISG) vehicle. Many aspects of the ISG system from the sizing of the electrical machine, the sizing of the battery(ies), the choice of battery chemistry, the choice of voltage, and the choice of control algorithms can be simulated with minimal expense or time consumption. Such simulations can assist the engineering team in making optimal design choices, all in advance of committing any expenditure of prototype funding. Simulations can provide an accurate approximation to the actual fuel economy impact of each of the potential higher-voltage functionalities that come with an ISG system. Further, total vehicle performance can be simulated to determine any performance-related issues prior to prototype component design and build. Content will be pulled from other papers to address the session topic of simulation impact on ISG vehicle design.

While the ZEV program's electric vehicles did not become successful market-driven products, many of the technical advantages of electric vehicles were validated by enthusiastic California consumers. Yet, battery technology has been and continues to be the limiting factor in terms of cost, functionality (range) and durability of EV systems. The automotive industry has largely moved on to research and development of other approaches to extremely low emissions and reduced fossil fuel consumption. PZEV gasoline vehicles, Hybrid electric vehicles, clean (EPA Tier 2) diesel vehicles and Proton Exchange Membrane (PEM) fuel cell electric vehicles (FCEVs) are the focus of attention. The purpose of this paper is to explore another possible solution: a battery electric vehicle with a relatively small fuel cell auxiliary power unit (APU) to recharge the battery pack during driving.