Design patterns for separating fault handling from control code in discrete manufacturing systems

Abstract

The objective of this paper is to propose a methodology for strictly separating fault detection and fault handling methods from control code in discrete manufacturing systems. In order to enable the separation, two different design patterns are elaborated. Based on an analysis of typical faults in manufacturing systems, a library of reusable function blocks for fault detection, handling, and also fault recovery is developed. These function blocks are implemented according to the international standard IEC 61499 and are applied within the design patterns. The design patterns are evaluated with the sequential control of an injection molding machine. It is shown, that the design patterns simplify the engineering and the separation of the fault detection and fault handling from control code significantly, since they provide clear design rules. Applying the proposed design patterns reduces the complexity of industrial control applications drastically. Furthermore, the function block library provides reusable and proven fault detection and fault handling methods.