Author: Deconinck, G.
Paper Title Page
THAAUST02 Suitability Assessment of OPC UA as the Backbone of Ground-based Observatory Control Systems 1174
  • W. Pessemier, G. Deconinck, G. Raskin, H. Van Winckel
    KU Leuven, Leuven, Belgium
  • P. Saey
    Katholieke Hogeschool Sint-Lieven, Gent, Belgium
  A common requirement of modern observatory control systems is to allow interaction between various heterogeneous subsystems in a transparent way. However, the integration of COTS industrial products - such as PLCs and SCADA software - has long been hampered by the lack of an adequate, standardized interfacing method. With the advent of the Unified Architecture version of OPC (Object Linking and Embedding for Process Control), the limitations of the original industry-accepted interface are now lifted, and in addition much more functionality has been defined. In this paper the most important features of OPC UA are matched against the requirements of ground-based observatory control systems in general and in particular of the 1.2m Mercator Telescope. We investigate the opportunities of the "information modelling" idea behind OPC UA, which could allow an extensive standardization in the field of astronomical instrumentation, similar to the standardization efforts emerging in several industry domains. Because OPC UA is designed for both vertical and horizontal integration of heterogeneous subsystems and subnetworks, we explore its capabilities to serve as the backbone of a dependable and scalable observatory control system, treating "industrial components" like PLCs no differently than custom software components. In order to quantitatively assess the performance and scalability of OPC UA, stress tests are described and their results are presented. Finally, we consider practical issues such as the availability of COTS OPC UA stacks, software development kits, servers and clients.  
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