Hybrid Simulation of Continuous-discrete Systems

Many processes in the chemical industry have some discrete phenomena superimposed on the continuous system dynamics. While the continuous behavior arises from phenomena such as mass, energy and momentum conversion, discrete behavior may occur due to physico-chemical discontinuities or discrete controller actions. Such systems which involve interaction between the continuous system dynamics and logical control functions are classified as Hybrid Systems. For such systems modeling in terms of the continuous variables alone is not sufficient. Simulation of such systems is necessary since discrete actions can trigger a qualitative change in the process model. Dynamic simulation becomes mandatory for the synthesis and validation of safety operating conditions in chemical processes or start-up and shut-down procedures. This paper presents a new hybrid simulation environment for modeling and simulation of hybrid systems. It offers a high-level design language for the automatic or semi-automatic generation of the process models. Examples of practical relevance as well as an outline for treating the logical consistency of multi-event network are given. The application of the simulation language is illustrated by means of a continuous-discrete implementation of a Dynamic Matrix Control strategy.