Hybrid Objects

Abstract

The behavior of hybrid systems is described by means of continuous and discrete variables. A number of di erent philosophies have been pursued in order to establish a mathematical framework that is able to handle both continuous and discrete processes. These range from the construction of hybrid automata [ACHH93] and structures [NOSY92], over the de nition of interfaces between the continuous and the discrete part [SA92] to more complex mathematical frameworks [Bro93]. Other approaches use Petri Nets [LBAD91], bond-graphs [STS93] or a synchronuous approach [BLG90], [BB91], just to name a few. In this paper we shall combine the modelling power of hybrid automata with the principles of object-orientation. The goal is to model reality by reusable objects that can easily be adapted to di erent applications|hybrid objects. That way, models of hybrid systems can be designed and can be used as components when modelling larger and more complex processes. The present work is based on the hybrid framework introduced in [TE93], and the object model introduced in [TE92]. In our framework a hybrid system is interpreted as consisting of a discrete controller within an analog environment (process). Hybrid automata then are generalized nite state machines where discrete transitions transfer the system between a nite number of control states or locations. The global states of a system can change continuously with time according to the laws of physics and these changes are governed for each control location by a set of di erential equations. The object model consists of a general part, which describes the system's full functionality, and a speci c part, which makes the object easily adaptable to di erent speci cations and control strategies. The speci c part contains exchangable receipes (the object's methods) which are functions of the given speci cations. We shall, in this paper, introduce a hybrid objectmodel together with an algorithm that allows us to automatically generate a set of correct methods for a restricted class of hybrid systems. This generation is done o -line and results in a deterministic control-law for each method. It is a function of the given speci cations. In the following sections we shall discuss the hybrid framework applied, introduce the hybrid object-model, and show how correct methods can be generated.

DOI: 10.1007/3-540-60472-3_25

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@inproceedings{Tittus1994HybridO, title={Hybrid Objects}, author={Michael Tittus and Bo Egardt}, booktitle={Hybrid Systems}, year={1994} }