PLC object-oriented programming using IEC61131-3 norm languages: An application to manufacture machinery

This paper presents an application of object-oriented methodology to the development of Programmable Logic Controller (PLC) programs. PLC is widely used as computer controller of manufacturing machinery, principally because its robustness and programming simplicity. During the last years, IEC61131-3 norm has been introduced aiming to provide standard languages and structure to the development environments of PLC programs, that are instead strictly bound up to now to proprietary languages. Following IEC61131-3 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. This paper describes an application of the novel standard IEC61131-3 to the development of the control software of a medium complexity manufacturing machinery. Software development methodology is reported and comparison regarding development time, software re-usability and application structuring, is then discussed.