Sequence-Controlled Web Services for Programmable Logic Controllers

The use of service-oriented architectures based on web services in the manufacturing layer of industrial enterprises enables vertical integration and promises increased interoperability. Unfortunately, the differing execution patterns—cyclic execution on programmable logic controllers vs. on-demand execution on industrial PCs—complicate the use of web services in the manufacturing layer. This paper introduces sequence-controlled web services that permit to easily export a control module as a web service. An automation engineer can use familiar IEC 61131-3 programming languages to implement the control application and subsequently can export selected modules as web services.