Strömberg, J.-E. and Nadjm-Tehrani, S. (1993). Towards Reliable Models of Hybrid Systems. Technical Report LiTH-IDA-R-93-48, Department of Computer and Information Science, Linköping University, Sweden. (bibtex),
Abstract: In this paper we address the question of adequacy of hybrid representations of computer systems embedded in physical environments. Within a proposed modelling framework we describe how reliable models for physical systems from the area of dynamic systems can be incorporated into models of hybrid systems with minimal effort. These models can be automatically derived based on descriptions of the physical system in the language of bond graphs. This inter-disciplinary modular modelling is only possible if the formalism used for description of hybrid systems is compositional and sufficiently expressive.We propose a modular variant of transition systems, Hybrid Transition Systems, for representation of hybrid systems. For this formalism a binary composition operator is defined, and an operational semantics provided. Two novel aspects of the formalism are separation of the input and state variables, and adoption of algebraic equations for description of the change in the value for some continuous variables.We illustrate the application of this formalism to representation of three realistic examples. We provide some example requirements specifications, and for one safety property we briefly sketch the needed analysis over the continuous state spaces. In another example it is illustrated that a hybrid formalism is even needed for the representation of the plant in isolation.
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