Figure 2 depicts the main ObjectTypes of the Sercos device model and their relationships. The drawing is not intended to be complete. For simplicity only a few components and relations were captured so as to give an overview of the overall structure.

Figure 2 – Device Model Overview

The symbols in this drawing are according to the OPC UA symbol elements. Figure 2 shows the ObjectTypes used in this specification as well as some elements from other specifications that help understand some modelling decisions. The upper grey box shows the OPC UA base information model from which the TopologyElementType and ProtocolType are derived. The grey box in the second level shows the main ObjectTypes from the OPC UA for Devices Companion Specification. The grey box in third level shows the Sercos OPC UA information model that this specification introduces. The components of those ObjectTypes are illustrated only in an abstract way in this overall figure. The grey box in the fourth level shows an example of a basic drive model.

TopologyElementType is the base ObjectType for elements in a device topology. It introduces Parameters (ParameterSet) and Methods (not shown). This specification also defines a functional grouping concept to provide alternative viewpoints.

A class of devices is represented by the DeviceType ObjectType. This includes predefined elements to describe and identify a device. SercosDeviceType extends the DeviceType. Therefore the elements are inherited from FunctionalGroupType, TopologyElementType and DeviceType. All OPC UA mandatory elements are implemented.

SercosProtocolType represents the Sercos communication protocol implemented by the TopologyElement.