Abstract The fidelity of the hybrid electric vehicle simulation is increased with the integration of a computationally-efficient finite-element based electric machine model, in order to address optimization of component design for system level goals. In-wheel electric motors are considered because of the off-road military application which differs significantly from commercial HEV applications. Optimization framework is setup by coupling the vehicle simulation to the constrained optimization solver. Utilizing the increased design flexibility afforded by the model, the solver is able to reshape the electric machine's efficiency map to better match the vehicle operation points. As the result, the favorable design of the e-machine is selected to improve vehicle fuel economy and reduce cost, while satisfying performance constraints. Introduction Hybrid electric vehicles (HEV) play a major role in achieving future emission standards and fulfilling social expectation of more sustainable transportation. HEV is a complex system where reversible and non-reversible energy sources need to operate in concert to achieve customer acceptance and enable a significant leap in the fuel economy. In order to maximize the application benefits, component design needs to be optimized iteratively through the component development and integration process. Simply stated, the component design needs to be guided by the powertrain configuration, performance requirements and desired system attributes. This paper outlines such an approach, where the electric machine design is tailored to fit a specific application.In this study, the off-road application is chosen with a 14 ton 4×4 truck as a vehicle platform [1]. A series HEV with four In-Hub motors, shown in Figure 1 fits the desired application as it allows: (i) optimized engine efficiency since the engine speed is independent from vehicle speed (ii) flexible hull design and modularity due to removal of mechanical driveline, (iii) outstanding maneuverability, since all four wheel motors are controlled independently, (iv) power export capability, where the vehicle can act as a stationary generator. In the Series HEV configuration all the propulsion energy needs to flow through the In-Hub motors, which emphasizes the impact of electric machine design on the system level efficiency, performance, weight and cost. Therefore the design optimization of In-Hub machine forms the core part of this paper. Figure 1. Series HEV vehicle with In-Hub motors The paper is organized as follows. First the e-machine design tool, based on the Finite Element Analysis (FEA), will be introduced. The efficiency and performance of an existing A Framework for Optimization of the Traction Motor Design Based on the Series-HEV System Level Goals2014-01-1801 Published 04/01/2014 Andrej Ivanco Clemson-ICAR Kan Zhou and Heath Hofmann University of Michigan Zoran Filipi Clemson-ICAR CITATION: Ivanco, A., Zhou, K., Hofmann, H., and Filipi, Z., "A Framework for Optimization of the Traction Motor Design Based on the Series-HEV System Level Goals," SAE Technical Paper 2014-01-1801, 2014, doi:10.4271/2014-01-1801. Copyright © 2014 SAE InternationalDownloaded from SAE International by Univ of California Berkeley, Sunday, July 29, 2018electric machine base design is captured by FEA. This enables both physical scaling, and changes of design parameters that ultimately shape the efficiency map. Computational effort is reduced by using static FEA and post-processing techniques described in [ 2, 3]. Hence the new designs of the electric machine can be generated and analyzed quickly, without resolving computationally expensive FEA for each new design. The second part of the paper introduces the optimization framework, where the previously developed predictive electric motor model is integrated into the vehicle simulation and coupled to the optimization solver. The optimization algorithm executes the model for every