Modelling the real-time behaviour of machine controls using UML statecharts

For covering the real-time characteristics of an automation system during model-based design it is essential to model not only the function but also the behaviour of the control programs running on a real-time controller. This paper introduces an approach to the modelling and evaluation of the functional and time behaviour of Programmable Logic Controllers (PLC) on model level. The control algorithm consisting of UML statecharts is extended with an execution model of the controller which is also given as a statechart. The approach is integrated into a model-based design system for industrial control systems focusing on the field of production systems. An example will be employed to illustrate the benefits of a model-based design system which does incorporate real-time aspects of the controller.