Analysis of Design Tradeoffs for Plug-in Hybrid Vehicles

This chapter presents a systematic analysis of the design tradeoffs present in plug-in hybrid electric vehicles (PHEVs) and presents a model of PHEV design to review how the PHEV design studies in literature can fit into the PHEV design model. The PHEV design process is broken up into three components including design objectives, analyses, and design attributes where objectives, analyses, and attributes for the PHEV can exist at system level, vehicle level, and subsystem level. This study investigates and summarizes the design tradeoffs that exist among these three levels of the design process for a variety of the PHEV subsystems. The study finds that a majority of PHEV studies to date have used vehicle-level design objectives to guide the design process and system level design attributes can be achieved only by including system-level design objectives and analyses directly into the PHEV design process. It also finds that designs of PHEVs are characterized by strong connections between the characteristics of the vehicles at the subsystem level and the design attributes at the vehicle and system levels. Several case studies are also presented to show how PHEV designers have found compromises among these design tradeoffs to achieve a set of design objectives. Some case studies demonstrate that subsystem-level design objectives can limit design space and thus restricting optimization toward system-level attributes whereas others demonstrate how system-level design objectives may lead a PHEV designer to compromise vehicle-level performance in pursuit of optimized system-level performance.