Semantic Modelling of Hybrid Controllers for Robotic Cells

Programmable Logic Controllers (PLCs) play an important role for integration of hardware and software in industrial robot cells. In this paper we propose a semantic grounding of the Sequential Function Charts (SFC) notation for specification of PLC programs. Our semantic grounding is expressed in the OWL semantic language and forms part of our semantic robot framework, called KIF (Knowledge Integration Framework). KIF is a set of ontologies and associated tools to ensure interoperability between heterogeneous equipment making up a robot cell. We also present a tool set for manipulating SFC instances stored in RDF triple stores reachable through the RDF4J framework. The semantic grounding and tool set are evaluated in a teaching-by-demonstration experiment in a small parts assembly setup featuring a collaborative industrial robot, ABB YuMi, where the tool set is used to create and execute SFC descriptions on-the-fly based on data from human demonstrations.