A comprehensive methodology for building hybrid models of physical systems

This paper describes a comprehensive and systematic framework for building mixed continuous/discrete, i.e., hybrid physical system models. Hybrid mode ls are a natural representation for embedded systems (physical systems with digital controllers) and for complex physical systems whose behavior is si mplified by introducing discrete transitions to replace fast, often nonline ar dynamics. In this paper we focus on two classes of abstraction mechanism s, viz., time scale and parameter abstractions, discuss their impact on bui lding hybrid models, and then derive the transition semantics required to e nsure that the derived models are consistent with physical system principle s. The transition semantics are incorporated into a formal model representa tion language, which is used to derive a computational architecture for hyb rid systems based on hybrid automata. This architecture forms the basis for a variety of hybrid simulation, analysis, and verification algorithms. A co mplex example of a colliding rod system demonstrates the application of our modeling framework. The divergence of time and behavior analysis principle s are applied to ensure that physical principles are not violated in the de finition of the discrete transition model. The overall goal is to use this framework as a basis for developing systematic compositional modeling and a nalysis schemes for hybrid modeling of physical systems. Preliminary attemp ts in this area are discussed, with thoughts on how to develop this into a mofe general methodology. (C) 2000 Elsevier Science B.V. All rights reserve d.