OPC Overview - Pipeliners Podcast...OPC Foundation • Formed in 1995 by a consortium of 5...

OPC Overview

Adam Hill

Kepware Technologies/PTC

Portland, ME (USA)

Agenda

• Before OPC

• OPC Foundation

• OPC Client Communications

• OPC Specifications

– OPC DA

– OPC HDA

– OPC AE

– OPC UA and Tunneling with OPC UA

May 14 – 16, 2019 INTERNATIONAL SCHOOL OF HYDROCARBON

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What You Will Learn

1.What does OPC stand for?

2.What is the purpose of the OPC

Foundation?

3.OPC specifies the communication between

what and what?


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Before OPC

Before OPC

• No standard exists for communication between devices (data sources) and computer

interfaces (data gatherers).

• Proprietary connections and toolkits are developed by hardware vendors.

– This limits users to one type of software and hardware package.

• As users want to make more client connections to one device, or add different hardware,

the problem gets sticky…


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Before OPC (cont.)


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OPC Foundation

OPC Foundation

• Formed in 1995 by a consortium of 5 companies:– Fisher-Rosemount, Rockwell, Opto 22, Intellution, and Intuitive Technology.

• Now there are over 450 corporate members in the Foundation.

THE FOUNDATION’S MISSION

“The mission of the OPC Foundation is to manage a global organization in which users, vendors and consortia collaborate to create data transfer standards for multi-vendor, multi-platform, secure and reliable interoperability in industrial automation.”

• To support this mission, the OPC Foundation:– Creates and maintains specifications

– Ensures compliance with OPC specifications via certification testing

– Collaborates with industry-leading standards organizations

May 14 – 16, 2019

OPC Foundation

• Approaching 500 Member Companies

world wide

• 80% North America and Europe and 20%

Japan, China and Rest of the World

• Thousands of OPC enabled products


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Board of Directors

• President and Chairman: Thomas Burke

• Governing Board Member Companies:

Ascolab, Beckhoff, Honeywell, ICONICS,

Microsoft, SAP, Siemens, Yokogawa

• Appoint officers, approve work items, and

drive direction of OPC


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Programs and Evangelism

• Certification

• Standard allow for interoperability –

but unfortunately not all solutions are

created equal

• Self-certification tools exists for

independent test and validation

• Independent (3rd party) lab

certification


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Programs and Evangelism

• Interoperability Workshops

– Competitors cooperating for the benefit of

the end user

– Yearly event held in North America,

Europe and Asia


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Evolution of OPC Acronym

• Originally, Object Linking and Embedding (OLE) for Process

Control.

– Object Linking and Embedding (OLE) was developed

by Microsoft to allow embedding in documents and other objects.

OLE 1.0, released in 1990, was the evolution of the

original dynamic data exchange (DDE). DDE only transfers

limited amounts of data between two running applications, while

OLE maintains active links. OLE was also the foundation for

COM technology.

• Moved away from Microsoft OLE to become Open Process

Control.

• Open Platform Communication

– OPC is now open connectivity via open standards.


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Client-Server-Device Concept

THEN

Client

Communication

Drivers

NOW

OPC Specs

Other

Standards

• OPC standardizes the connection specifications between a

client and a server (or also a client and an OPC-enabled

device, but this is uncommon).

• The server then bridges the communication from the client

to the device, and the server is smart enough to know to

maintain only one device connection so as not to

overburden the device.

• Thus, the client-server-device architecture is optimized.

• Before the advent of OPC, each client connected directly to

each device. With this approach, multiple clients could be

asking the same device for the same data. This was not

efficient or optimal for the device.


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Client-Server-Device Concept

Client

Communication

Driver

Robust Hardware,

Immune to

Electrical Noise

and Resistant to

Vibration and

Impact

Friendly UI,

Graphics and

Visualization,

Graphing,

Alarming,

Redundancy

Seamless Data

Source

Connectivity,

Interoperability

with Other

Software Apps

Scalable to Support One Device or Entire Plant, Great Customer

Support

Friendly UI,

Graphics and

Visualization,

Graphing,

Alarming,

Redundancy

Scalable and

Supportable

Seamless Data

Source

Connectivity,

Interoperability

with Other

Software Apps

Scalable and

Supportable

Robust

Hardware,

Immune to

Electrical Noise

and Resistant to

Vibration and

Impact

Scalable and

Supportable


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OPC Client Communications

OPC Client Communications

These options are controlled through settings in a connected client.

• Synchronous or asynchronous requests for polls or explicit (one-time)

reads

• Poll data or subscribe to data

– Polls require the server to return data at a set interval

– Subscriptions work on exception-based reads, where data is updated to the

client when a data change event is detected by the server

• Read from the device memory or server cache


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Client-Server Communications:

• Synchronous read/write will wait until the read or write has been completed before

continuing the poll cycle

Go Poll Neighborhood A

now, I will wait on the line

till you are done.

Go Poll Neighborhood B

now, I will wait on the line

till you are done.

Synchronous


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Client-Server Communications:

• Asynchronous read/write executes the

command and uses “call back events” for

when the read/write has been completed.Go Poll Neighborhood A,

call me back when you are

done.

Go Poll Neighborhood B,

call me back when you are

done.

Asynchronous


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Synchronous

Client

Server


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Asynchronous

Client

Server


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OPC Client Communications Applied

• When would it be appropriate to use either asynchronous and

synchronous reads?

• What are the settings recommended for highest throughput?

• Answer: Subscribe to items (if possible) or perform asynchronous polls

or read from the server cache.


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OPC Specifications

OPC “Classic” or the original OPC specifications are:

• OPC Data Access (DA)

• OPC Alarms and Events (AE)

• OPC Historical Data Access (HDA)

• OPC XML Data Access (XML-DA)

• OPC Data Exchange (DX)

• OPC Security

• OPC Batch

• OPC Complex Data

NEW OPC STANDARDS ARE FIREWALL FRIENDLY (DCOM INDEPENDENT) AND ENCOMPASS THE MOST ADOPTED CLASSIC SPECIFICATIONS INTO A SINGLE INTERFACE• OPC .NET (OPC Express or Xi)

– Runs on all Microsoft Platforms.

• OPC Unified Architecture (UA)

– Runs on any platform.

– Allows for new information models and vendor specific models.


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OPC DA Features

• Exchanges real-time data between client and server in the form of Value, Quality and

Timestamp (VQT).

• Supports browsing of available servers and information accessible in that server.

• Items can be scanned at a particular rate (down to 10ms).

• Supports reads, writes and subscriptions.

OPC

OPC

Physical I/O


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More on VQT

VALUE

• The latest state of an item of interest.

QUALITY

• Can I trust this state? Is the connection in error?

• Refers to the connection between the server and the device.

• If there is bad connection quality, the server returns “Unknown” value or the last good value.

TIMESTAMP

• Freshness of the data.

• This can come from the device or the OPC server depending on setup.

• Is the clock accurate?

Good OPC Servers and Clients do not ignore any part of VQT!


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OPC DA Environment

• Dependent on Microsoft’s Distributed Component Object Model (DCOM);

originally called "Network OLE". Remember “OLE for Process Control” used

to be OPC.

• Authentication controlled through Windows Component Services, not any 3rd

party software product.

• Microsoft Windows Domains or Workgroups only.

• Inside the firewall.

• No VPN Access.


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OPC Historical Data Access (HDA)

OPC DA is for real-time data, why the

need for HDA?

WHY?

• Ability to access and modify archived

data for a specific time domain.

• Read, Write and Playback raw or

aggregated data.

WHY NOT?

• Many end users just use OPC DA to get

the raw real-time data into a client.

• The client then handles the data

archiving.

• Based on DCOM.


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OPC Alarms and Events (AE)

OPC AE

WHY?

• Ability to evaluate alarms on the server

level.

• Alarms are central to the server

WHY NOT?

• Just like HDA, many end users just use

OPC DA to get the raw real-time data into

a client.

• The client then handles the alarming.

• Based on DCOM.Alarms and

Events Server


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OPC UA

OPC UA Environment

• Uses Binary/TCP and SOAP/HTTP for a Service-Oriented

Architecture (SOA).

• Meant to work on multiple Operating Systems (OS). Platform

independence!

• DCOM independent and Firewall/network barrier friendly.

• Combines OPC “Classic” into a single service set.


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OPC UA Connectivity

OPC UA

• Endpoint to endpoint

communication through a single

dedicated TCP port (very easy to

get through network barriers)

• Data encryption to RSA

standards and authentication

based on the x509 Certificate

standard. (This is the same

encryption e-commerce uses)

opc.tcp://10.10.110.10:49320


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Compare UA to DA

OPC DA and DCOM OPC UA and TCP/Binary

Must control security permissions through Windows Authentication and Windows Shell (Windows Platform dependence).

Optional authentication handled by the application. Optional security settings (certificate exchange and encryption) which are handledby the application, and do not depend on the OS shell(Platform independence).

Must drop the firewall or allow a long list of exceptions for the different applications trying to communicate.

Allow an exception for one single port (49320 for KEPServerEX) for OPC UA communication.

All machines must be on the same Local Area Network (Workgroup or Domain).

Applications can reside on any system, domain, or network anywhere.

Tunneling with OPC UA

Why the Need for Tunneling?

When applications do not support OPC UA, but a communications path through barriers

(such as across networks or firewalls) is needed, users can use an intermediate “tunneling”

application.

Perhaps to:

• Allow an OPC DA client on one network to talk to a device or an OPC DA server on a

different network

• Allow a non-OPC client on one network to talk to a device or OPC DA server on a

different network

• Enable a device on one network to exchange data with a device on another network

• Add security to communications


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Client App

(SCADA, HMI,

Database, etc.)

Client Side

Tunnel

Application

Server Side

Tunnel

Applicaiton

PLC or other

data source

Bulk Reads

Monitored Items: Data from Subscription Queue

Legend

Client Protocol

(OPC DA, OPC .NET,

OPC XML-DA, DDE,

SuiteLink, NIO, etc.)

OPC UA Protocol

Device Protocol

OPC UA Publish

Request & Response

Device Data

Device Read

What Does a Tunnel Look Like?Communication Barriers

(Firewalls, routers, other networks, the Internet)


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Key Takeaways

• Before OPC

• OPC DA

• OPC UA (Tunneling)

• Quick Use Case Example

INTERNATIONAL SCHOOL OF HYDROCARBON

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May 14 – 16, 2019

Questions?


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OPC Overview - Pipeliners Podcast...OPC Foundation • Formed in 1995 by a consortium of 5...

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