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The article focuses on the development of an OPC UA (object linking and embedding (OLE) for process control unified architecture) server. One of the major concerns regarding this new specification is the migration from the old component object model (COM) to the new UA specification. From the various migration strategies described in this article, the authors' server represents a special adapter software solution which aggregates several COM servers, one for each flexible manufacturing system (FMS) modelled in the address space of the UA server. The article focuses on the advantages introduced by the new specification like the unified modelling capability and the extensible meta model. The address space is exemplified by means of a screw fitting station, which is part of the flexible line, on which the UA server has been tested. From the four generally accepted use cases, the server implements the first two: observation and control. They are mainly supported through the variables and the methods of the address space. During the testing phase, the minimum sampling interval regarding the communication with the underlying COM servers has been determined for a different number of FMSs. As a result the special adapter software solution is a fast but also a well-performing approach, which works well even in very complex environments.
Date of Publication: August 2011