Cloud-Enabled Automation Systems Using OPC UA

摘要

Emerging data-intensive applications like smart grids and the internet of things pose new challenges to industrial monitoring systems. Data has to be transferred not only within plant networks but also through the internet, across firewalls, proxies etc. OPC UA is a modern industrial communication standard that is getting more and more adopted in various industries. A drawback of OPC UA related to a cloud-based application is its client-server based communication concept. Following this communication principle, OPC UA has to handle hurdles caused by firewalls, proxies, dynamic IP-addresses, NATs and client-lookup strategies. While web and cloud technologies have successfully been used for various enterprise applications, their maturity for industrial applications with higher requirements for responsiveness and robustness is largely unknown. Widely used technologies for communication from a cloud application towards client-side services are XMPP and Websockets. The purpose of this work is to bring OPC UA together with web and cloud technologies in order to enable the use of OPC UA in cloud environments. We have extended the clientserver concept of OPC UA and provide an evaluation of the applicability, reliability and performance of various web-based communication protocols that serve as an additional transport layer underneath OPC UA. We have therefore extended the OPC UA communication stack with XMPP and Websocket support and we analyzed the performance of these extensions.