155ARTICLE INFO Article ID: 08-07-02-0010 Copyright © 2018SAE Internationaldoi:10.4271/08-07-02-0010 History Received: 28 Mar 20 18 Revised: 20 Ma y 2018 Accepted: 29 Jun 20 18 e-Available: 31 Oc t 2018 Keywords HEVs, optimization, Genetic Algorithm, military hybrid vehicles, Pontryagin’s Minimum principle Citation Liu, Z., Mamun, A., Rizzo, D., and Onori, S., “Combined Battery Design Optimization and Energy Management of a Series Hybrid Military Truck,” SAE Int. J. Alt. Power. 7(2):155–167, 2018, doi:10.4271/08-07-02-0010. ISSN: 2167-4191 e-ISSN: 2167-4205 Combined Battery Design Optimization and Energy Management of a Series Hybrid Military Truck Zifan Liu and Abdullah-Al Mamun Mamun, Clemson University, USA Denise M. Rizzo, U.S. Army TARDEC, USA Simona Onori, Stanford University, USA Abstract This article investigates the fuel savings potential of a series hybrid military truck using a simul - taneous battery pack design and powertrain supervisory control optimization algorithm. The design optimization refers to the sizing of the lithium-ion battery pack in the hybrid configuration. The powertrain supervisory control optimization determines the most efficient way to split the power demand between the battery pack and the engine. Despite the available design and control optimization techniques, a generalized mathematical formulation and solution approach for combined design and control optimization is still missing in the literature. This article intends to fill that void by proposing a unified framework to simultaneously optimize both the battery pack size and power split control sequence. This is achieved through a combination of genetic algorithm (GA) and Pontryagin’s minimum principle (PMP) where the design parameters are integrated into the Hamiltonian function. As GA and PMP are global optimization methodologies under suitable conditions, the solution can be considered as a benchmark for the application under study. Five military drive cycles are used to evaluate the proposed approach. The simulation results show 5%-19% reduction in fuel consumption depending on the drive cycle compared to a baseline non-optimized case. Downloaded from SAE International by Duke Univ, Friday, January 11, 2019156 Liu e t al. / SAE Int. J. Alt. Power. / Volume 7, Issue 2, 2018 © 2018 SAE International. All Rights Reserved. Introduction Military vehicles require increased power and energy for superior dynamic performance, reliable power exportability, and durable silent watch capability when compared to passenger vehicles. Yet enhancing the fuel efficiency of military vehicles is an important issue that needs to be addressed [ 1]. Hybridization of the military vehicle powertrain is seen as a potential mean to achieve significant fuel efficiency improvement while providing the required performance. Hybrid electric vehicles (HEVs) combine multiple power sources to enable fuel-saving functions, such as regenerative braking, engine idling elimination, and effi - cient engine operating region shift. However, the deployment of military HEVs is still under active research due to chal - lenges such as reliability in complex operating and environ - mental conditions [ 2]. The focus of this article is to develop a systematic approach to optimize the design and energy management of military HEVs, accounting for specific military driving conditions. In HEVs, a high-level supervisory energy management strategy (EMS) manages the energy flow among different power sources at each time instant. The objective of the EMS is to achieve certain tasks, such as minimization of fuel consumption and/or tailpipe emission and/or battery health degradation, under appropriate constraints, satisfactory driv - ability, and component specifications [ 3]. The highest benefits out of powertrain hybridization are achieved under the optimal component design and optimal power split between the engine and the energy storage system (ESS). Different optimizatio