Abstract
The purpose of this paper is to present a dynamic model of a complex hybrid electric propulsion system. The analyzed system consists of an engine, one or two electric motors, a conventional (epicyclical) automatic transmission, the rest of the drivetrain, as well as a vehicle body, all these subsystems being modeled individually by means of bond graph language and then linked together to form the complex powertrain system. Causality issues are of great importance when coupling the individual systems and components, as the authors emphasize throughout the paper. Equally important is to choose the adequate, compatible accuracy of models, in order to avoid blocking the simulations. Emphasis is on bond graph modeling technique, which is a link between physical (real) model and its mathematical (equations) description. Increased attention is given to methods of generalizing the powertrain system governing equations, as in the case of the automatic transmission model, which is designed to be flexible and easily changeable to other transmission models. Several hypotheses regarding drivetrain (rigid or elastic drive shafts, tire model) are taken into account, and a unique, generic SimulinkTM drivetrain model is given, valid for all drivetrain hypotheses. A GUI dialog box establishes all model parameters, for ease of modification. Bond graph models of electric motors catch the basic physical phenomena of electric machines, and integrate well into the assembled system bond graph. A series of breakaway acceleration simulations is performed in Simulink, and conclusions are presented and discussed.
Keywords: Hybrid Electric Vehicle, Modeling and Simulation, Bond Graphs, Block Diagrams, Variable Dynamics - Systems.