SPEAKER: Anders P. Ravn

DATE: 6 November 1998

PLACE and TIME: Room E3-209 at 14:00.

ABSTRACT: (presented at the Nordic Workshop, Turku, October 1998)

When computers become integral parts of a machine or a plant, they have to interact directly with a physical system. Specifications therefore involve both a dynamical systems model, typically based on smooth functions of real time, and models of digital programs, usually some form of automata. The challenge in hybrid systems is to integrate such models and not the least to find notations that makes it possible to reason about interactions between the the continuous and discrete worlds. This talk initially discusses several case studies in order to illustrate where hybrid reasoning is justified and also where one may more usefully treat the two views separately using real-time constraints as a fixed interface. After a summary of the hybrid systems model developed by Branicky and others, we introduce a design technique where stability (the central property of dynamical systems) is proved by combining a theorem about stability of mode switched systems with a specification of a reactive system with real-time constraints.