Evaluation of Motor and Battery Requirements for Hybrid-Electric Powertrains during Cranking

Hybrid electric vehicles (HEVs) are an emerging technology for improving fuel economy and emissions. However, hybrid powertrains are expensive to manufacture because of the sophisticated electronics required. In particular, the motor and battery requirements must be carefully considered because of the cost and weight of these components. For this reason, it is important to conduct an upfront analysis to determine the minimum requirements for the motor and battery [1]. Such an analysis ensures that the requirements for the vehicle (acceleration, fuel economy, etc) can be met while minimizing the incremental cost to the consumer. This paper describes the development of engine and transmission models used to perform such an analysis for a research vehicle project. The model must take into account several important effects such as crankshaft position, engine damper design, motor design, control strategies and so on. The multidomain modeling capabilities of Modelica allow us to formulate a model with which all these important effects can be captured [2]. This paper will show that such a model is not only capable of helping hardware designers evaluate the performance of different electrical components but also allows experimentation with various control strategies for controlling the launch clutch and drive motor.