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OPC evolution toward Unix

OPC evolution toward Unix. From Windows to World Wide Domination?. Mark Beharrell IT/CO, CERN, Geneva, Switzerland ICALEPCS ― October 12th, 2005. Communication standards within a DCS OPC Data Access OPC on Unix The future. Data Flows within a Detector Control System. DCS. Accelerator.

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OPC evolution toward Unix

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  1. OPC evolution toward Unix From Windows to World Wide Domination? Mark Beharrell IT/CO, CERN, Geneva, SwitzerlandICALEPCS ― October 12th, 2005 • Communication standards within a DCS • OPC Data Access • OPC on Unix • The future

  2. Data Flows within a Detector Control System DCS Accelerator Web Access Supervisor (SCADA) Experiment General Services Devices Safety

  3. Device communication • Device access protocols vary between:- • Manufacturers • Models • Versions of models • Want an ‘interpreter’ • Hide device differences • Developed by 3rd party • What protocol to use with the interpreter?

  4. Middleware • General solutions • CORBA • Java RMI • DCOM • General solutions are not sufficient • Must solve a specific problem in standard way • Need Standardize to level of the device • “Data Acquisition” • “OPC Data Access”

  5. The OPC DA solution • 1996 - OPC Data Access 1.0 • Well defined specification giving • Device model • Data model • Communications model • Acceptance • Wide user base • Uses DCOM middleware

  6. Why OPC on Unix • Motivation • Single protocol for all device oriented • communications • Possibilities • DCOM on Linux • OPC XML DA • OPC Unified Architecture

  7. 1. DCOM on Linux • 1996 – Microsoft release the DCOM Spec. • Implementations on Solaris, VxWorks, Linux • DCOM → OPC • OPC DA (DCOM) Servers on Linux • Performance? • Stability?

  8. 1. DCOM-Performance & stability • Test • Windows OPC server ported to Linux • Measured time to read OPC items (float) on both platforms • Result • Windows OPC ~ 100,000 items per second • Linux OPC ~ 76,000 items per second • Problems • OPC server itself was stable • ‘System issues’

  9. 2. OPC XML DA • 2003 – OPC XML DA released • Similar to the DA specification • Same device and data model • Different communication model • Based on Web Services • OPC XML DA on any TCP/IP enabled processor

  10. 2. XML-Performance & stability • Test • Wrote OPC XML server using toolkit. • Measured time to read OPC items (float) on both platforms • Result • OPC XML DA ~ 6,000 items per second • Verses 76,000 with OPC on Linux! • Problems • ~5 items per second for single OPC item reads! • Interface definition does not always translate to code correctly.

  11. 3. OPC Unified Architecture • 2005 – OPC UA introduced • But not yet released • Fusion of OPC interfaces • “Integration of plant floor data into enterprise systems and the internet” • Provide secure, reliable and efficient services • Protocol and platform independence • DCOM to be ‘retired’ • Replaced by SOAP based alternatives

  12. Low industrial acceptance Not yet available It works but is it useful? • Several solutions to OPC servers on Unix. • DCOM based • OPC XML DA • OPC UA • Waste of time ? - NO • OPC DA clients on Linux based SCADA systems.

  13. Internet Enterprise Factory Platforms Into the future • OPC DA lives for the time being • OPC XML will be replaced by UA • OPC UA holds promise. • But World Wide Domination? For device access – maybe!

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