Component Sizing Study for a Light-duty Series Hydraulic Hybrid Vehicle in Urban Drive Cycles

With the focus on energy efficiency for many different kinds of vehicle applications, hybridization is considered a possible solution to reduce fuel consumption. While hybrid electric concepts are already available for passenger vehicles, and also considered for heavier applications, hybrid hydraulic alternatives have been mainly limited to the latter, which benefit most from the higher power density available. To study the different hybrid architectures and applications, a modeling framework for the system design is developed using the simulation tool Hopsan from Linköping University. Previously, the model of a series hydraulic hybrid vehicle was introduced, a lightduty vehicle simulated over two standard urban drive cycles, and its potential for further work established. In this paper, the model is extended by including a simple combustion engine power management to provide for more realistic propulsion of the hydraulic drivetrain, showing the potential to operate a series hydraulic hybrid vehicle’s engine in more efficient regions. Additionally, the design is studied concerning the effects of a variation of key component sizes on the accuracy and energy efficiency objectives. Instead of subjecting the system to (multi-objective) optimization, at this stage the individual components’ influence is studied, and the objectives are dealt with separately from each other to eliminate the need for compromise between them to gain a better understanding of the interdependencies.