Modeling for simulation of hybrid drivetrain components

Designing a hybrid drivetrain is a complex task, due to the unknown sensitivity of vehicle performance to system components specifications, the interaction between systems components, and the ability to operate the system components at different set points at any time. Therefore, many researchers [16] have made efforts formulating, and developing holistic hybrid drivetrain analysis, design, and optimization models including the top-level vehicle system control. However, an integral design approach [6] is usually characterized by large computation times, complex design problem formulations, multiple subsystem simulations, analyses, and non-smooth, or non-continuous models. In this paper, the influence of the component efficiencies, whereby the engine operation strategy (engine-, or system optimal operation) on the fuel economy, and the Energy Management Strategy (EMS) is investigated. Thereby, a relative simple Rule-Based (RB) EMS [11] is used, and is compared with the strategy based on Dynamic Programming (DP). The series-parallel transmission of the Toyota Prius has been used as a case study. The component modeling, and simulation results from the RB EMS, and DP are compared with results from the simulation platform ADVISOR. Finally, it is shown, that modeling the component efficiencies by only a few characteristic parameters, and using the RB EMS, the fuel consumption can be calculated very quickly, and with sufficient accuracy. In future work, the influence of topology choice on the fuel economy, and the EMS will also be investigated.