In a world of growing competitiveness, the role of simulation in vehicle development is constantly increasing. Because of the number of possible advanced power train architectures that can be employed, development of the next generation of vehicles requires accurate, flexible simulation tools. Such tools are necessary to quickly narrow the technology focus to those configurations and components that are best able to reduce fuel consumption and emissions.

With improvements in computer performance, many researchers started developing their own vehicle models. But often computers in simulation are used only to “crunch numbers.” Moreover, model complexity is not the same as model quality. Using wrong assumptions can lead to erroneous conclusions; errors can come from modeling assumptions or from data. To answer the right questions, users need to have the right modeling tools. For instance, one common mistake is to study engine emissions by using a steady-state model or to study component transient behavior by using a backward model.

Figure G-1 summarizes the main requirements, discussed below, for vehicle simulation tools required to fulfill both needs.

Basic Requirements
Maximum Reusability

While numerous plant and control models exist throughout companies, it is critical that the work performed during a project can be reused throughout the companies for future applications. Several approaches are necessary to achieve this goal:

  • Duplication of systems without duplication of models stored. For example, a wheel model should be reused numerous times without storing it several times under different names, which would make versioning management difficult.

  • Location of expert models in a single site. For example, an engine system comprised of control, actuator, plant and sensor models, and initialization file, by being located under the same folder, would facilitate its transfer to another expert.

  • Open source of the plant and control models (rather than compiled) to facilitate understanding of the assumptions and the modifications of equations to model new phenomena.

Maximum Flexibility

With the consistently increasing number of possible power train configurations for medium- and heavy-duty applications and the need to select the different level of modeling to properly meet different needs (i.e., fuel efficiency, emissions, drive quality), the need to quickly simulate any application is crucial. A vehicle modeling software should be able to provide the following features:

  • Simulation of subsystems, systems, collections or combinations of systems and subsystems (e.g. power trains), or entire vehicles. Providing a common environment to different experts (e.g., engine and vehicle experts) will facilitate the model’s reusability and ensure process consistency (e.g., validation, calibration).

  • Allow any configuration (assembly of systems) to be quickly modified and built automatically. For maintenance purposes, saving hundreds of models (a number

FIGURE G-1 Vehicle modeling tool requirements.

FIGURE G-1 Vehicle modeling tool requirements.

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