Non-Proprietary Controller-to-Controller Communications

Summary

By Bill Lydon, Editor

The improvement of manufacturing productivity and quality requires sharing data and synchronizing controllers. This can now be accomplished by using new standards that were jointly developed by PLCopen and the OPC Foundation.

There is a continued focus on achieving more manufacturing productivity and synchronization of the entire supply chain, and that is driving more requirements to orchestrate industrial plant controllers. A major user complaint is that controllers from multiple vendors cannot communicate peer-to-peer using an open standard. Each vendor has their own methodology, and many use their own communications protocols.

Controller suppliers seem to be ignoring this requirement, and as a result, users are frustrated. For example, at the ARC World Industry Forum held last February in Orlando, Florida, a panel of major automation vendor executives was asked by a user who operates multiple plants why controllers from each of these vendors cannot communicate peer-to-peer with each other. He explained that this is needed to accomplish his goals for better manufacturing productivity in existing plants. The answers did not address his issue and ranged from suggestions to replace other controllers with, “our brand,” “buy gateways,” and use “our industrial Ethernet protocol.”

PLCopen/OPC UA Solution

The PLCopen organization and the OPC Foundation have been listening to users. This challenge is now solved with the PLCopen/OPC UA function blocks that are able to communicate from controller to controller over industry standard Ethernet using common data models.

The first multivendor demonstration of this communication was presented at the 2012 SPS/IPC/DRIVES trade fair held in Nuremberg, Germany. This functionality is important because the business reality is there are controllers from multiple vendors, with multiple industrial protocols, in existing plants. In addition, new plants have a wide range of controllers, particularly on skid and prebuilt units, that need to communicate with other controllers. The PLCopen/OPC UA function blocks accomplish horizontal and vertical OPC-UA connection with included security.

The PLCopen organization and the OPC Foundation have been cooperating since 2008 to combine the technologies and create a platform and manufacturer-independent information and communication architecture. The goal is to increase the efficiency of engineering, process and information exchange. These efforts have led to the creation of the standard for the IEC 61131 controller programming environment and offer secure and efficient data exchange with industry standard function blocks.

PLCopen OPC UA Function Blocks

The joint PLCopen/OPC Foundation working group mapped the IEC 61131-3 software model to the OPC UA information model. This resulted in a standard way that OPC UA server-based controllers expose data structures and function blocks to OPC UA clients, including HMI, MES, Enterprise systems, and other controllers. PLCopen/OPC UA function blocks make it easy for a user to create applications that communicate directly from controllers to other controllers, enterprise systems, and other OPC UA devices.

The use of proprietary protocols for accessing a diverse range of machines is no longer required with the application of international standards based on OPC UA, PLCopen, and industry standard web services. Users can achieve an efficient access mechanism for different equipment from different suppliers to communicate shared information and coordinate control over standard Ethernet without the burden of proprietary industrial protocols.

Related Articles

• Digital Factory Superstructure Emerging with OPC UA
• OPC UA Redefines Automation Architectures
• Simplifying Automation System Hierarchies

Resources

• The Technical Specification "OPC UA Information Model for IEC 61131-3 ," version 1.00  
• Introduction in the PLCopen and OPC UA Communications Model
• OPC Foundation Website
• PLCOpen Organization Website