Abstract

This paper describes the development of a forward-facing, series hydraulic hybrid vehicle (SHHV) powertrain model for medium size trucks, together with dynamic equations and basic features of subsystem modules. For properly handling all the control variables that arise from the significant freedoms introduced by the SHHV powertrain, a two level hierarchical control architecture is proposed emphasizing the assessment and optimization of the top level thermostatic state of charge (SoC) based energy management controller, with the expectation that series configuration would maximize the fuel economy as engine is decoupled from the wheels. Simulation results over the urban driving cycle represent a significant departure from the conventional wisdom of operating the engine near its sweet spot, show what is preferred from the system stand-point, and also demonstrate the potential of the selected hybrid system to substantially improve vehicle fuel economy. The improvement can be as high as 96.5% with engine shutdown and 71.9% with engine idling.

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