Reusable Components for Industrial Logic Control Programming
This paper addresses the problem of developing logic control programs in industry to cope with new requirements of flexible manufacturing systems. We propose a component based approach in which the control program is developed using Reusable Automation Components (RACs). Reusing components may speed up the development and also make the control program have fewer bugs. To get these benefits it is important that components already verified to work properly are reused. The RACs thus contain not only the implementation but may also be richly specified, using concepts from Design by Contract in object-oriented software development. The specification is helpful both for users of the components and for developers since the complete RAC including the specification can be translated to a tool for formal verification, to determine whether the specification is fulfilled or not. The RAC is introduced for general implementation languages and it is in this paper shown in detail how the RAC can be implemented and specified using the common IEC 61131 standard and especially Ladder Diagrams, the most common language today for logic control programs. An example RAC is specified, implemented and finally verified.