opc evolution toward unix
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
OPC evolution toward Unix
Mark Beharrell IT/CO, CERN, Geneva, Switzerland ICALEPCS ― October 12th, 2005
►Communication standards within a DCS►OPC Data Access►OPC on Unix►The future
From Windows to World Wide Domination?
2
Data Flows within a Detector Control System
DevicesDevices
Supervisor(SCADA)
Accelerator
Accelerator
ExperimentExperiment
SafetySafety
General Services
General Services
Web Access
Web Access
DCS
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”
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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
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Why OPC on Unix
MotivationSingle protocol for all device oriented
communications
Possibilities1. DCOM on Linux
2. OPC XML DA
3. OPC Unified Architecture
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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?
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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’
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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
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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.
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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
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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.
Low industrial acceptance
Not yet available
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Into the future
• OPC DA lives for the time being
• OPC XML will be replaced by UA
• OPC UA holds promise.
Platforms
But World Wide Domination?Enterprise
Factory
Internet
For device access – maybe!