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The improvement of computational resources transformed the Modeling and Simulation (M&S) stage into a key task during the prototyping of novel vehicle concepts. It helps the design allowing the evaluation of new concepts/topologies under faulty or dangerous conditions.
It is also useful for tuning controllers and evaluating the whole system performance, even prior to actual construction. M&S has become an unavoidable step in the development of Electric and Hybrid Electric Vehicles (E&HEV).
Naturally, there are plenty of models by which the system may be sized and optimized, and according to its characteristics, may be analyzed. There is a trade-off between simplifications in the model and the amount of useful information obtained from it. Another trade-off exists between the level of detail and the computational power needed for simulation. Vehicle models can be classified depending on the direction of calculation:
- Forward Models make calculations starting from the engine toward the wheels. This model is preferred when dynamics is under analysis and for control strategy development.
- Backward Models start with the driving force required at the wheel (in order to match a velocity profile) and then work backward to the engine.
In forward models, a set of differential equations are generated; whereas in standard backward models, only static equations are solved, thus making these latter models much faster to run, while their accuracy is reduced.
Another categorization depends on the required degree of detail: quasi steady-state or dynamic models. In quasi steady-state models, more simplifications are assumed, resulting in a model faster to run but with less accuracy.
When the dynamics are of major interest, a dynamic model is employed. They are physic-based and reproduce the transient evolutions.
Once the model of the vehicle is defined, the representation of the model can be accomplished with a functional or a structural approach.
- Functional approaches have virtual links for connecting sub-systems. They give an overall description and are used in applications oriented to control design.
- Structural approaches are based on the topology of the real system and the links respond to physical connections. They are useful for system design and its analysis in faulty conditions.
In summary, the M&S stage, as applied to E&HEV, is crucial to reduce time and cost during the design stage. Choosing the proper model according to the particular study to be performed must be done carefully. | 
 stage into a key task during the prototyping of novel vehicle concepts. It helps the design process by allowing the evaluation of new concepts/topologies under faulty or dangerous conditions.*/);){kind=small}
