This paper presents an all-wheel-drive (AWD) hybrid electric vehicle (HEV) design approach for extreme off-road applications. The paper focuses on the powertrain design, modeling, simulation, and performance analysis. Since this project focuses on a military-type application, the powertrain is designed to enhance crew survivability and provide several different modes of limp-home operation by utilizing a new vehicle topology -herein referred to as the island topology. This topology consists of designing the vehicle such that the powertrain and other equipment and subsystems surround the crew compartment to provide a high level of protection against munitions and other harmful ordnance. Thus, in the event of an external shield penetration, the crew compartment remains protected by the surrounding equipment - which serves as a secondary shield. The powertrain system principally consists of two internal combustion engines which are coupled to three electric machines using two planetary gear sets, and also includes other transmission elements. A detailed design of the powertrain is presented, which considers the vehicle layout, space claim issues, and extreme operating conditions.
Next in the paper, the mathematical model of the powertrain is outlined. The powertrain model is quasi-static, meaning that it neglects high-frequency dynamics due, for example, to gear elasticity. The model however, takes into account the inertias of the various components, as well as accounting for the parasitic losses due to friction. Finally, the powertrain model is implemented in a simulator program that provides an all-encompassing tool that allows for a complete analysis of the energy flow within the powertrain components. With this, the powertrain control strategy can be formulated with the objective of minimizing fuel consumption and / or maximizing performance using a trade-off approach.