Object-oriented approach to PLC software design for a manufacture machinery using IEC 61131-3 norm languages

Presents an application of object-oriented methodology to the development of programmable logic controller (PLC) programs. The PLC is widely used as a computer controller of manufacturing machinery, principally because of its robustness and programming simplicity. The IEC 61131-3 norm has been introduced aiming to provide standard languages and structure to the development environments of PLC programs, that up to now have been strictly bound to proprietary languages. Following the IEC 61131-3 prescription, is it also possible to develop well structured, object-oriented control software, which was hardly possible with the former vendor-specific low-level languages. The paper describes an application of the IEC 61131-3 standard to the development of the control software of a medium complexity manufacturing machinery. The software development methodology is reported and comparison regarding development time, software re-usability and application structuring, is then discussed.