Active Modeling: A Method for Creating and Simulating Variable-Complexity Models

摘要

Effective and efficient simulation-based design is facilitated by models of appropriatencomplexity. A single model will not have the most appropriate level of complexitynthroughout all phases of a simulation maneuver if inputs or parameters vary. Ideally, anmodel for which complexity can be varied as necessary will achieve the best possiblentrade-off between accuracy and computational efficiency. A method is presented fornswitching system model elements on and off as their importance changes, and predictingnthe response of the resulting variable-complexity model. A modified transformer elementnremoves the dynamic output of a model element to the rest of the system when the movingnaverage of its absolute power falls below a user-defined threshold. When the element isn“off,” the input from the system to the element is still passed through the transformer sonthat an estimate of element power and importance can continue to be calculated and thenelement switched back “on” if necessary. The bond graph formalism is used to facilitatenimplementation. Switch configurations are defined for both causally weak and causallynstrong energy storage and dissipative elements. The method is applicable to linear ornnonlinear systems that can be modeled with lumped parameter elements. The approach isndemonstrated for quarter- and half-car vehicle models subject to a road profile of varyingnfrequency. The appropriate model complexity at all stages is determined and implementedncontinuously without prior knowledge of input or parameter changes.