DISTRIBUTED CONTROL STANDARD CONNECTS INDUSTRY REGARDLESS OF BUS.docx

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DISTRIBUTED CONTROL STANDARD CONNECTSINDUSTRY REGARDLESS OF BUS

Monday, 07 May 2007

Distributed Control Standard Connects Industry Regardless ofBus

Page 2 Page 3 All Pages

In the early days of modern automation, the use of microprocessortechnology addressed the need for fast and efficient configuration of

control logics through graphical methods that mimic the hardwiredrelay logics. Over the past 30 years, the automation community hasput the emphasis on simplifying and standardizing the method ofprogramming this new breed of controllers. From these efforts camethe adoption of the IEC 61131-3 standard that specifies theprogramming languages for automation.

Fieldbus Proliferation

From the very moment that the industry started to usemicroprocessor-based

programmable logic
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controllers (PLCs), the need of having these controllers to exchangeinformation, gather data from remote units, and set interlocks betweencontrollers initiated a quest for a comprehensive solution. Early on, theindustry focused on finding or establishing communication protocols

and methodologies that would be candidates for standardization. TheModicon protocol, or Modbus, was one result of an internationallyaccepted standard. Derivatives of Modbus such as Modbus RTU orModbus IP are good examples of partial solutions to meet the demandfrom automation engineers, but standards havent stopped there. Over

time, associations and major automation vendors have proposedindustrial fieldbus networks that eventually evolved into standards,such as PROFIBUS, DeviceNet, ControlNet, Fieldbus Foundation,CANbus, SERCOS, EtherCAT, Siemens H1, and many others.


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Interoperability

Realized

Despite a proliferation of standards, however, interoperability stilllagged among differing standards. Several organizations initiateddiscussion on how to achieve coherent cooperation among controllersin the same application. Fieldbus Foundation, among others,addressed the format of pertinent information to be shared on the

network. Yet, although the mechanism of exchanging informationcould be defined, the cooperation between devices was notaddressed. The International Electrotechnical Commission (IEC) cameup with a conceptual view of how to have independent programmablelogic controllers cooperate in a cohesive and very efficient manner. By
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defining the IEC 61499 standard, the IEC addressed the need for acomprehensive and familiar approach to automation controllers

cooperation. Using function blocks as a visual representation of acontrol entity, the IEC committee redefined the methodology of

creating modern control systems. Today, industrial networkingsoftware providers are building network control and monitoringapplications that take this visual block approach to defining industrialnetworks comprising disparate field bus components that traditionallycould not communicate.

Implementing IEC 61499

In creating an automation system, one would traditionally start by

looking at individual control applications and then determine how tohave these interact with each other. The advent of IEC 61499 createdthe structure for, among other things, a supervisory application layerthat connects isolated control systems. One example of thissupervisory industrial networking and control software is the ISaGRAF5 control software environment. These programming, networking, andcontrol environments allow the designer to define the local behavior ofthe control devices as well as global diagrams using the IEC 61499

environment. Alibrary of drop-in functional blocks regulates the behaviors of thecooperating devices. Custom-made function blocks also can be
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dropped into the diagram to regulate the behaviors. Each 61499function block is made of two parts (see Figure 1). The top part holdsthe ECC (Execution Control Chart). The IEC 61499 standard specifiesthat this part should be programmed using a state machine. Under

ISaGRAF 5, it is programmed using an SFC (Sequential FunctionChart), which happens to be an ideal state machine.

The bottom partdefines the actual control function. It can be programmed using any ofthe IEC 61131 languages: SFC, FBD (Function Block Diagram), LD(Ladder Diagram), ST (Structured text), and IL (Instruction List). EachIEC 61499 function block is assigned to a specific resource. Theseresources will eventually be assigned to a given device (calledconfiguration under IEC 61131) and one device can hold more than

one resource. Therefore, an IEC 61499 diagram can span multipleresources, which may also mean spanning multiple devices. IEC61499 helps the automation engineer to tackle a range of controlchallenges, from simple control challenges to very complex ones.ISaGRAF, for example, gives the engineer the opportunity to havedifferent views over the control application and refers to these viewsas the Hardware view, the Resource view and the Link architecture,as illustrated in Figures 2, 3, and 4, respectively.

The Hardware view shows the physical devices on the network, in61499 mode. It also uses icons to indicate the devices that have anestablished 61499 relationship, as well as which 61499 diagramregulates the relationship. By double-clicking on the diagramreference, the user can have a look at the actual diagram. An IEC
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61499 diagram greatly accelerates deploying applications across anindustrial network made up of proprietary devices, switches, andcontrollers. The 61499 diagram supersedes the implementation ofindividual applications on individual devices.

Traditionally, anapplication would be implemented on individual controllers in

traditional automation, interacting with each other through manuallyimplemented data transfers or interlocks.

However, the IEC 61499 function block diagrams span over multipledevices (referred in the past as configurations or controllers) and,therefore, regulate the interaction between the various devices using a

single functional diagram. By usingthe graphic network design environments such as the ISaGRAF 5suite of automation tools, it is now possible to create control systemsthat define interactions among multiple devices. These could bePLCs, field controllers, or field instruments (flowmeter, valves, pumps
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etc.) with variable footprints, but all interacting in a well-defined andcoherent fashion without the need for manually implementedalgorithms on individual devices. With IEC 61499, the industrialcontrol network is a seamless extension to the hardware bus on the

controller, making the design of networked control systems as simpleas the design of a singular PLC.

This article was written by Julien Chouinard, Managing Director, at

ICS Triplex ISaGRAF in Montreal, Canada. For more information,

contact Mr. Chouinard [email protected],or

visithttp://info.hotims.com/10968-402.

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402?showall=1&limitstart=

Each 61499 function block is made of 2 parts:

1. The top portion holds the ECC (Execution

Control Chart). The IEC 61499 standard specifies

that this part should be programmed using a statemachine. Under ISaGRAF 5.0, it is conveniently

programmed using SFC, which happens to be an

ideal state machine.

2. The bottom portion defines the actual control

function. It can be programmed using any of the

IEC 61131 languages.

IEC 61499 function blocks can either be Basic or Composite. You can create anew Basic FB by programming its ECC and FB algorithms and by defining its

inputs and outputs. Composites are created using basic FBs as well as a library ofstandardized IEC 61499 FBs. An IEC 61499 application is made of interconnectedBasic and Composite FBs. Within an application, these FBs are distributed overresources and devices if need be. ISaGRAF acts to deploy the distributedapplication over resources and devices resulting in FBs that are automaticallyconnected to one another.http://www.isagraf.com/pages/newsletter/nov_2005.htm
mailto:[email protected]:[email protected]:[email protected]://www.medicaldesignbriefs.com/component/content/article/1096-et/features/6017-10968-402?showall=1&limitstart=http://www.medicaldesignbriefs.com/component/content/article/1096-et/features/6017-10968-402?showall=1&limitstart=http://www.medicaldesignbriefs.com/component/content/article/1096-et/features/6017-10968-402?showall=1&limitstart=http://www.isagraf.com/pages/newsletter/nov_2005.htmhttp://www.isagraf.com/pages/newsletter/nov_2005.htmhttp://www.isagraf.com/pages/newsletter/nov_2005.htmhttp://www.medicaldesignbriefs.com/component/content/article/1096-et/features/6017-10968-402?showall=1&limitstart=http://www.medicaldesignbriefs.com/component/content/article/1096-et/features/6017-10968-402?showall=1&limitstart=mailto:[email protected]


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FUNCTION BLOCK MODEL

IEC 61499 FUNCTION BLOCK MODEL

Application Note

www.isagraf.com- January 2006

Definition

The IEC 61499 standard defines a distributed model for splitting

different parts of an industrial automation process and complex

machinery control into functional modules called function blocks. These

function blocks can be distributed and interconnected across multiple

controllers.

System:

A collection of devices interconnected and communicating with eachother by means of a communication network consisting of segments and

links.

Device:

An independent physical entity capable of performing one or more

specified functions in a particular context and delimited by its interfaces.

Resource:

A functional unit having independent control of its operation, and which

provides various services to applications including scheduling and

execution of algorithms.Application:

A software functional unit that is specific to the solution of a problem in

industrial-process measurement and control. An application may be

distributed among devices and may communicate with other

applications.

Function block:

A software functional unit that is the smallest element of a distributed

control system. It utilizes an execution control chart (ECC) state

machine to control the execution of its algorithms.Overview

A Function Block Model represents parts included in a measurement and

control function block. Figure 1 shows these parts of a measurement

and control function block. Many function blocks are connected together

with a data/event interface and are part of an application.
http://www.isagraf.com/http://www.isagraf.com/http://www.isagraf.com/


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A function block is a functional unit of software comprising an individual

instance or copy within a resource. The algorithms contained within a

function block are hidden from the outside of the function block and are

scheduled according to the Execution Control Chart state machine

(ECC).

Copyright 2006: ICS Triplex ISaGRAF Inc. All rights reserved. No

portion of this work may be reproduced in any form or by any means,

without the prior written permission of ICS Triplex ISaGRAF Inc.

IEC 61499 Function Block Model

Event inputs and outputs are used to synchronize function blocks within

an application and to schedule the algorithms within the function block.

Data inputs and outputs are the interface with the external of the

function block since internal data is hidden. The data may be part of the

algorithms and may also be state information for the Execution Control

Chart (ECC).

Function blocks are created by defining their ECC and programming

their algorithms. These function blocks are called basic function blocks(see Figure 1). The ECC is a state machine processing events and

scheduling algorithms. It defines the behavior of the function block upon

receiving events. The algorithms operate on internal variable values,

input values, and output values. Each basic function block can run on

any resource.


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When function block algorithms and the control of their execution are

expressed entirely in terms of interconnected function blocks, these are

called composite function blocks (see Figure 2). These are created by

interconnecting existing basic and composite function blocks. No ECC or

algorithm is created. A composite function block runs on any resource.However, the basic and composite function blocks making up a

composite function block run on the same resource as the main

composite block.

An application is defined by function block (Basic and Composite)

networks specifying event and data flows throughout function block

instances. The event flow determines the scheduling and execution of

the function blocks algorithms. Each function block within the

application can be distributed across resources and devices.

In ISaGRAF, an application can be created using custom function blocks

or function blocks from libraries. Figure 3 shows the basic function block

editor. Figure 4 shows the composite function block editor and figure 5

shows the function block model displayed by the ISaGRAF toolset.Figure 3 displays a function block ECC state machine and a function

block algorithm from the basic function block editor. The ECC is a state

machine built using the SFC editor. Algorithms can use any of the

IEC61131-3 programming languages as well as the flow chart language

provided in the ISaGRAF toolset. The available IEC 611313 languages


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are the following: Sequential Flow Chart (SFC), Function Block Diagram

(FBD), Ladder (LD), Instruction List (IL), and Structured Text (ST).



without the prior written permission of ICS Triplex ISaGRAF Inc. 2

IEC 61499 Function Block Model

Composite function blocks can also be created in the ISaGRAF toolset

using the composite function block editor (see Figure 4). ISaGRAF

enables you to create a composite function block by adding any

available basic and composite function block to the function block

network.

The newly created function block is available for use in any application

and can be configured to run on any resource or device part of thesystem.


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portion of this work may be

reproduced in any form or by any means, without the prior written

permission of ICS Triplex ISaGRAF Inc. 3

International Electrotechnical Commission: Function Blocks Part 1 -

Architecture (61499-1 CEI:200X). ICS Triplex ISaGRAF Inc.: ISaGRAF

Users Guide. November 2005.


portion of this work may be reproduced in any form or by any means,without the prior written permission of ICS Triplex ISaGRAF Inc. 4http://www.oooneida.org/publications_Others_FunctionBlock_model.html

IEC 61499 Application Model

Application Note

www.isagraf.com

January 2006

Definition





controllers.
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System: A collection of devices interconnected and communicating with

each other by means of a communication network consisting of

segments and links.

Device: An independent physical entity capable of performing one or

more specified functions in a particular context and delimited by itsinterfaces.

Resource: A functional unit having independent control of its operation,

and which provides various services to applications including scheduling

and execution of algorithms.

Application: A software functional unit that is specific to the solution of

a problem in industrial-process measurement and control. An application

may be distributed among devices and may communicate with otherapplications.

Function block: A software functional unit that is the smallest element

of a distributed control system. It utilizes an execution control chart

(ECC) state machine to control the execution of its algorithms.

Overview

An Application Model represents parts included in a measurement and

control application. Figure 1 shows these parts of a measurement and

control application. Many function blocks are connected together with a

data/event interface and are part of an application. The device is a self-contained hardware capable of executing an application distributed

across one or multiple resources.

A resource is considered to be a functional unit contained in a device.

The functions of a resource are to accept inputs from the process

interface (IO driver) or the communication interface (Shared memory,

communication network), process the data, and return outputs to these

interfaces.

An automation and process control application runs in a resource or

splits the load across multiple resources to use the special features of

each resource.


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(c) Copyright 2006: ICS Triplex ISaGRAF Inc. All rights reserved. No


without the prior written permission of ICS Triplex ISaGRAF Inc.IEC 61499 Application Model

An application may consist of one or more function blocks where the

input sampling is performed in one function block, control processing is

performed in a second function block, and output conversion is

performed in a third function block. This distributed application may run

function blocks within one resource or across multiple resources. These

resources are part of one or many devices.

An application is defined by function block networks specifying event

and data flow throughout function block instances. The event flowdetermines the scheduling and execution of the function blocks'

algorithms.

In ISaGRAF, each program can be a distributed application. Figure 2

shows distributed function blocks within an application. This is the

Application Model displayed by the ISaGRAF toolset.

A distributed application exchanges data across the communication

interface. The ISaGRAF elements use the communication interface

transparently. Building and compiling the application generates all

required link parameters. Each distributed element of an application isconnected to the others across the communication interface. When

building an ISaGRAF application, the distributed application generator

automatically links together these distributed elements.

Figure 2 displays function blocks, links between function blocks, and

service interface function blocks. The Publish and Subscribe function


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blocks are service interface function blocks. These interface the

application with the communication interface and the process interface.

All other function blocks are basic, composite custom build, or

predefined function blocks from the library.

Figure 2: ISaGRAF Application Model Viewer

References


Architecture (61499-1 (c) CEI:200X). ICS Triplex ISaGRAF Inc.:

ISaGRAF User's Guide. November 2005.

(c) Copyright 2006: ICS Triplex ISaGRAF Inc. All rights reserved. No



permission of ICS Triplex ISaGRAF Inc. 2http://www.oooneida.org/publications_Others_Application_model.html

IEC 61499 EXECUTION MODELApplication Note


Definition


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controllers.

System:

A collection of devices interconnected and communicating with eachother by means of a communication network consisting of segments and

links.

Device:



Resource:



execution of algorithms.Application:




applications.

Function block:



machine to control the execution of its algorithms.Overview

An Execution Model represents parts included in a function block

execution mechanism. Figure 1 shows these parts of a execution

mechanism. Each function block execution follows a specific mechanism.


instance or copy within a resource. The algorithms contained within a

function block are hidden from the outside of the function block and are

scheduled according to the Execution Control Chart state machine

(ECC).


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Event input (t2) and event output (t8) are used to synchronize function

blocks within an application and to schedule the algorithms within the

function block.

Data input (t1) and data output (t5) are the interface with the externalof the function block since internal data is hidden. The data may be part

of the algorithms and may also be state information for the ECC.




IEC 61499 Execution Model

Function blocks can be created by defining their ECC, input and output

signals, and programming their algorithms. These function blocks arecalled Basic function block. The ECC is a state machine processing

events and scheduling algorithms. The ECC defines the behavior of the

function block upon receiving events. The algorithms operate on internal

variable values, input values, and output values. Each Basic function

block can run on any resource.

In a Basic function block, timing is important. Data inputs are received

first (t1), then the event inputs (t2) are either received at the same

time or next. When event inputs trigger the ECC execution the function

block must have stable data inputs. Otherwise, erroneous behavior

occurs. At t3, the resource schedules the execution of the algorithms

related to the event. At t4, the algorithms start running and process the

input data signals. Upon completion, the algorithm outputs the data

signal (t5), then the resource is notified (t6) and the ECC takes over at


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t7. The ECC outputs event signals (t8) and the execution of the function

block is completed until the reception of a new event.

When function block algorithms and the control of their execution are

expressed entirely in terms of interconnected function blocks, these are

called Composite function block. These are created by interconnectingexisting Basic and Composite function blocks. No ECC and algorithms

are created. A Composite function block may run on any resource. Each

function block within the Composite function block runs on the same

resource as the Composite function block. Function blocks within of a

composite function block cannot be individually distributed across

multiple resources.

The execution of a Composite function block differs from a Basic function

block; A Composite function block does not have an ECC or algorithms.

At some point when breaking down a Composite function block, eachfunction block contained within is a Basic function block and executes as

a standard Basic function block. The overall timing delay depends on the

execution time of each of these internal function blocks.

In ISaGRAF, you can create applications using custom function blocks or

function blocks from libraries. You can also create Basic function blocks.

The ISaGRAF ECC is a state machine built with the SFC editor. However,

the ECC has a different execution behavior from IEC 61131 SFC. All

STEPS execute in one virtual machine cycle until a FALSE transition

occurs. Algorithms may use any of the IEC61131-3 programminglanguages as well as the flow chart language provided with the ISaGRAF

toolset. The available programming languages are the following:

Sequencial Flow Chart (SFC), Function Block Diagram (FBD), Ladder

(LD), Instruction List (IL), and Structured Text (ST).

Composite function blocks can also be created with the ISaGRAF toolset

using the Composite FB editor. ISaGRAF enables the creation of

composite function blocks by adding any available Basic and Composite

function block to the function block network.

The creation of a new function block (basic or composite) makes it

available for use in any application and may be configured to run on any

Resource or Device making up the system.


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Figure 2 shows the execution mechanism used by an ISaGRAF control

engine. After reading IO inputs and bound variables, the logic isprocessed. Then bound variables, retain variables and output IO are

written. This cycle starts over once the delay is over.





Figure 2: ISaGRAF Basic Function Block Execution Model

The ISaGRAF Basic function block execution model operates as defined

in the IEC 61499 standard.When the ISaGRAF resource consumes bound data, the resource reads

the event and data input values (WITH qualifier). This is IEC 61499 t1

and t2 time (figure 1). Then the resource starts the execution of the

function block ECC (t3 - figure 1) as it starts executing the TIC code.

The algorithm is then running (t4 - figure 1) and upon completion (t5 -

figure 1), the algorithm writes the output data values. The resource (t6

- figure 1) returns execution to the ECC (7). This one writes output

event values. Then the resource writes bound data values (WITH

qualifier). This action generates the event and data signalssimultaneously.

References





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IEC 61499 DISTRIBUTION MODEL

Application Note


Definition





controllers.

System:

A collection of devices interconnected and communicating with each

other by means of a communication network consisting of segments and

links.

Device:



Resource:

A functional unit having independent control of its operation, and whichprovides various services to applications including scheduling and

execution of algorithms.

Application:




applications.

Function block:

A software functional unit that is the smallest element of a distributedcontrol system. It utilizes an execution control chart (ECC) state

machine to control the execution of its algorithms.

Overview

A Distribution Model represents parts included in a measurement and

control system. Figure 2 shows these parts of a distribution model. An

application can be distributed by allocating its function block instances


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to different resources in one or more devices. Function blocks are the

atomic unit of distribution. An application built with many function

blocks is displayed as one schematic while its function block instances

are distributed across resources and devices. Figure 1 shows a control

system having many devices connected together via the controlnetwork. The application built with function blocks is distributed across

these devices.




IEC 61499 Distribution Model

Many devices (Configuration) are connected together via a

communication network. The device is a self-contained hardware

capable of executing a control loop. The device is a controller having a

processor, memory devices and may contain a communication network

when used in a distributed application. The devices are PLCs solving the

control logic and can be seen in intelligent actuators such as valves or in

sensors such as flow meters. Any field bus can serve as communication

network. Industrial Ethernet, Profibus, DeviceNet are among those often

used. Some networks are faster while others are more deterministic.

The choice of network depends on the process to control. Hard real-time


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or soft real-time applications need specialized communication networks

to meet the time-critical behaviors.

An automation and process control application runs in a single device or

across mutiple devices to split the load and use the feature specialty of

each device.

An application may consist of one or more control loops where input

sampling is performed in one device, control processing is performed in

a second device, and output conversion is performed in a third device.

These cooperative control loops share data in a predictive and

deterministic way described in the IEC 61499 standard.


shows distributed applications across devices. This is the Distribution

Model displayed by the ISaGRAF toolset. All function block bitmaps

(yellow) at the right of the application name indicate the distribution

across devices. A bitmap displayed below a device means that the

program has a part running in that device. The absence of a bitmap

below a device means that the program has no part running in that

device. For each program built using the ISaGRAF toolset, the System

Model viewer quickly displays the distribution of the application. Each

device can have either a bitmap representation or the standard icon.

The communication network connects together devices that are part of a

distributed system. Many communication networks are displayed if such


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is configured in the system. Some devices may use one communication

network while others may use another.


network. The ISaGRAF elements use the communication network

transparently. Building and compiling the application generates allrequired link parameters. Each distributed element of an application is

connected to the others across the communication network. Upon


automatically links these distributed elements together.


portion of this work may bereproduced in any form or by any means,

without the prior written permission of I CS Triplex ISaGRAF Inc. 2

IEC 61499 Distribution Model

Figure 3 shows the devices, the communication network, the

applications, the distributed relationship between devices and


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applications as well as the application schematic. Application_A has

parts running on the first, second, and third device. Application_B has

parts running on the last two devices of the system. Application_C runs

only on the first device. Each part of Application_A exchanges the

proper information across the communication network. The sameapplies to Application_B.

In the System Model view, double-clicking an application displays its

schematic view. The schematic view is the Application Model. In this

view, there are no device boundaries. It is a one schematic for the

distributed application. Each function block in the application can be

assigned to a resource which is also assigned to a device. The event and

data signals between the function blocks are simple to draw. The

ISaGRAF distribution generator creates all required links between these

signals. These links exchange information transparently on thecommunication interface.

The functional relationships between the function blocks of an

application are unaffected by its distribution. The ISaGRAF toolset takes

care of the whole distributed aspect of the application. Delays are added

in the communication interface and in the algorithms execution that

must be taken into account when designing such a distributed

application.


Architecture (61499-1 CEI:200X). ICS Triplex ISaGRAF Inc.: ISaGRAFUsers Guide. November 2005.




IEC 61499 SYSTEM MODEL

Application Note


DefinitionThe IEC 61499 standard defines a distributed model for splitting




controllers.


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System:

A collection of DEVICES interconnected and communicating with each


links.

Device:An independent physical entity capable of performing one or more


Resource:




Application:


industrial-process measurement and control. An application may bedistributed among devices and may communicate with other

applications.

Function block:




Overview

A system model represents parts included in a measurement and control

system. Figure 1 shows the parts of this system model. Many devices(configurations) are connected together with a communication network.

The device is a selfcontained hardware capable of executing a control

loop. The device is a controller having a processor and memory devices

and may also contain a communication network when used in a

distributed application. The devices are PLCs solving the control logic

and are seen in intelligent actuators such as valves and in sensors such

as flow meters. Any field bus can do for the communication network;

Industrial Ethernet, Profibus, DeviceNet among others are often used.

Some communication networks are faster while others are more

deterministic, therefore, network selection depends on the process to

control. Hard real-time and soft real-time applications require

specialized communication networks to meet time-critical behaviors.


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An automation and process control application either runs on a single

device or splits the load across many devices to use the special features

of each device.




IEC 61499 System Model

An application may consist of one or more control loops where the input

sampling is performed in one device, control processing is performed in

a second device, and output conversion is performed in a third device.

These cooperative control loops share data in a predictive anddeterministic way explicitly detailed in the IEC 61499 standard.


shows distributed applications across multiple devices. This is the

System Model displayed by the ISaGRAF toolset. All function block

bitmaps (in yellow) at the right of the application name indicate the

distribution across devices. A bitmap below a device means that the

program has a running part in that device. No bitmap displayed below a

device means the application has no running part in that device. For

each program built with the ISaGRAF toolset, the System Model viewer

quickly displays the distribution of the application. Each device is

represented with either a bitmap or a standard box.

The communication network connects the devices making up a

distributed system. Many communication networks are displayed when

configured this way in the system. Some devices may use one


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communication network while other devices may be connected to

another.


network. The ISaGRAF elements use the communication network

transparently. Building and compiling the application generates allrequired link parameters. Each distributed element of an application is

connected to the others across the communication network. Upon


automatically links these distributed elements together.

Figure 2 shows the devices, the communication network, the

applications making up the system as well as the distributed relationship

between devices and applications. Application_A has parts running on

the first, second, and third device. Application_B has parts running on

the last two devices of the system. Application_C runs only on the firstdevice. Each part of distributed Application_A exchanges the proper

information across the communication network. The same information

exchange applies for Application_B.




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References


Architecture (61499-1 CEI:200X). ICS Triplex ISaGRAF Inc.: ISaGRAFUsers Guide. November 2005.




TRAINING - RESOURCE MODEL

IEC 61499 SYSTEM MODEL

Application Note


DefinitionThe IEC 61499 standard defines a distributed model for splitting




controllers.

System:



links.Device:



Resource:




Application:




applications.

Function block:



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Overview

A Resource Model represents parts included in a measurement and

control resource. Figure 1 shows these parts of a measurement andcontrol resource. Many function blocks are connected together with a

data/event interface and are part of a resource. The device is a self-

contained hardware capable of executing control loops programmed in

one or multiple resources.

A resource is considered to be a functional unit contained in a device.

The functions of a resource are to accept inputs from the process

interface (IO driver) or the communication interface (Shared memory,

communication network), process the data, and return outputs to these

interfaces.

An automation and process control application runs in a resource or

splits the load across multiple resources to use the special features of

each resource.

Figure 1: IEC 61499 Resource Model

Copyright 2006: ICS Triplex ISaGRAF Inc. All rights reserved. Noportion of this work may be reproduced in any form or by any means,


IEC 61499 Resource Model

An application may consist of one or more control loops where the input

sampling is performed in one function block, control processing is



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function blocks within one resource or across multiple resources. These

resources are part of one device or multiple devices.


shows distributed applications within a resource. This is the ResourceModel displayed by the ISaGRAF toolset.


interface. The ISaGRAF elements use the communication interface

transparently. Building and compiling the application generates all

required link parameters. Each distributed element of an application is

connected to the others across the communication interface. When


automatically links together these distributed elements.

Figure 2 displays function blocks, links between function blocks, andservice interface function blocks. The Publish and Subscribe function

blocks are service interface function blocks. These interface the

application with the communication interface and the process interface.

All other function blocks are basic, composite custom build, or pre-

defined function blocks from the library. From the Device Model viewer,

clicking on an application pops up the Resource Model view.


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portion of this work may bereproduced in any form or by any means, without the prior written


PRACTICAL HINTS

IEC 61499 PRACTICAL HINTS

Application Note


Definition





controllers.

System:



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links.

Device:


specified functions in a particular context and delimited by its interfaces.Resource:




Application:




applications.Function block:



machine to control the execution of its algorithms

Overview

Building a distributed application is not always simple. What is the

starting point? What is the cycling time? How to get IO and variable

values? How to exchange data between applications and devices? What

are good programming practices and data integrity? This applicationnote is all about these issues.

An application may consist of one or more function blocks where input

sampling is performed in one function block, control processing is



function blocks within a single resource or across multiple resources.

These resources are part of one device or multiple devices.


instance or copy within a resource. An automation and process control

application having many function blocks requires synchronization to

guarantee data integrity and good behavior.

Starting Point

Figure 1 shows the RESTART function block that sets the starting point

of an application. All function blocks contained in an application should


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be initialized and have a proper starting point. Since individual function

blocks can run on any resource or device, their order of execution must

be defined. The RESTART function block clearly indicates the starting

point of the application. This function block sends an event when the

resource runs for the first time, then all other function blocks formingthe application start running.

The RESTART function block can be connected to all function blocks

contained in the application. In this case, when the function blocks

receive the RESTART event, these switch to the running state. Also, the

RESTART function block can be connected to a single function block. In

this case, the first function block receives the RESTART event and starts

running, then its output event and data signals trigger other function

block contained in the application.

Copyright 2006: ICS Triplex ISaGRAF Inc. All rights reserved. Noportion of this work may be reproduced in any form or by any means,


IEC 61499 Practical Hints

An application can run one time or periodically (cyclically). Function

blocks can be on standby awaiting an event signal to start running.

Signals coming from input devices or human machine interfaces trigger

these function blocks. In applications needing to run periodically, a

common practice is to use the PERIODIC function block providing the

cycle time to the application. This PERIODIC function block sends anevent signal at a specific time interval and sets the cycle time for the

control loop. In this type of application, the PERIODIC event should

exceed the total execution time of the application. Otherwise, the

function block will deviate from the defined cycle time. The total

execution time of an application is equal to the propagation delay


35/42

between function blocks and the internal execution times of the

algorithms defined for all individual function blocks.

Service Interface

An application needs to read and write to the external world. Accessing

IO device values, variable values, and communication values is common

in any control and automation application.

IEC 61499 application schematic disallow variables since these require

declared instances on a resource and device. An interfacing mechanism

is needed. Function blocks specializing in such purposes are called

Service Interface Function Blocks. These function blocks are the atomic

object used for distribution application rather than variables. Therefore,

an application must contain service interface function blocks to enable

reaching IOs, variables, and communication values.

Figure 3 shows an application having an input service interface (IN) and

an output service interface (OUT). The input service interface retrieves

values from IO points coming from an IO device driver as well as

variable values coming from a resource database or a communication

interface such as an OPC server or field bus link. The output service

interface sends data values to external IO devices, variable databases,

and a communication link.



without the prior written permission of ICS Triplex ISaGRAF Inc. 2IEC 61499 Practical Hints

Individual function blocks contained in an application can reach internal

variables on their own, therefore, these function blocks do not require

service interfaces. However, Adding service interfaces to an application

increases the reuse of function blocks and programming flexibility.


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Data Integrity

Since ISaGRAF applications event and data signals are synchronized,

each time an event is sent from a function block, the corresponding data

is valid. Therefore, the receiving function block has valid data associated

with the event. Each time a function block consumes its inputs, it

retrieves all events and data from other function blocks linked to itsinputs. Also, a function block produces all of its output signals

simultaneously.

Figure 4 shows two function blocks interfacing with FB2. How are the

event and data signals synchronized since FB1 and FB3 do not talk to

each other? This type of programming brings about data integrity

problems in the application. FB2 gets the event and data signals from

both function blocks correctly, however, the synchronization of the

event and data signals is uncertain. Moreover, the data coming from

FB3 may not be ready when FB1 outputs its event signal.


37/42



without the prior written permission of I CS Triplex ISaGRAF Inc. 3

IEC 61499 Practical Hints

Figure 5 shows FB3 receiving its event and data signals correctly. When

FB1 sends its event signal, it asks FB2 to prepare the data and drive FB3correctly. Such good programming practices save a lot of debugging

time.

References





38/42




Demos ajempls isafraf

http://www.icpdas-usa.com/isagraf_product_demos.html

http://www.infoplc.net/noticias/item/1201-isagraf-anuncia-la-versi%C3%B3n-61-de-isagraf-con-

nuevo-workbench-y-firmware-c5

ISaGRAF anuncia la versin 6.1 deISaGRAF con nuevo workbench yfirmware C5

Martes, 24 Abril 2012

o

o

o

o

ISaGRAFISaGRAF, la firma lder en tecnologa de software

para automatizacin, ha anunciado la versin 6.1de ISaGRAF. ISaGRAF es el firmware yworkbench lder del mercado para conformidad a

IEC 61131-3 e IEC 61499 en productos deautomatizacin industrial. ISaGRAF 6.1 es una
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39/42

importante novedad formada por un nuevoworkbench y la nueva versin 5.3 del firmwareC5. Ahora se basa en el potente Microsoft Visual

Studio 2010 y ofrece una mayor velocidad, uninterface de usuario nuevo y mejorado, as comouna gestin ms avanzada de ventanas y del

paquete de software.

ISaGRAF 6.1 incorpora extensiones (plug-ins) para las nuevas

funciones, as como para implementar algunas de las funcionesque han popularizado al galardonado ISaGRAF 5 entre clientes

de todo el mundo. Entre las funciones que vuelve a incorporar

ISaGRAF 6.1 Workbench se encuentra un editor de IEC 61499.

Otros lenguajes disponibles son: LD, FBD, ST, SFC y SAMA.

Otra importante funcin ahora disponible en esta nueva versin

se denomina Control de Fuente de Versin (Version SourceControl) y permite trabajar a mltiples usuarios sobre los mismos

elementos (p.ej., dispositivo, recurso, punto de utilizacin) al

realizar una doble comprobacin de entrada y salida. Tambin

permite a los usuarios gestionar mltiples versiones de un
http://www.infoplc.net/media/k2/items/cache/37d163b88a4522bd852de06260df3d98_XL.jpg


40/42

proyecto, realizar copias de seguridad y restaurar proyectos

enteros o determinados elementos de un proyecto, as como

comparar archivos entre diferentes versiones.

Otras funciones incorporadas como novedad a ISaGRAF 6.1 son

Interrupciones de Usuario, Failover (Cambio de Unidad), rbol de

Dependencia, Biblioteca de Bloques, Monitor de Bloqueo de

Variables y Estado del Controlador.

Dado que los diferentes tipos de aplicaciones necesitan diferentes

tipos de Interrupciones (p.ej., tiempo, impulso, E/S...), laimplementacin de las Interrupciones con ISaGRAF ofrece un

conjunto de herramientas que permite a los OEM definir y asignar

las interrupciones a una aplicacin ISaGRAF. Tambin incorpora

un plug-in para que los usuarios finales configuren y programen

las interrupciones.

Failover (Cambio de Unidad) es un modo de soporte para elfuncionamiento en el que un sistema de control secundario asume

las funciones de un sistema de control cuando el sistema primario

no est disponible debido a una avera del equipo o una parada

programada. Se utiliza para hacer que los sistemas de control

sean ms tolerantes a fallos. La funcin Failover de ISaGRAF 6.1

permite al usuario modificar decisiones acerca del control y

cambiar las condiciones a partir de las cuales un controlador

recupera o pierde el control.

El plug-in rbol de Dependencia proporciona a los usuarios una

visin completa de todos los elementos incluidos en una


41/42

aplicacin de forma que puedan ver todas las dependencias entre

variables, as como las dependencias ascendentes y

descendentes para cada variable.

La Biblioteca de Bloques supone una mejora del interface de

usuario que permite a los usuarios arrastrar y soltar cualquier

funcin o bloque de funciones en un programa en lugar de

realizar la seleccin desde el selector de bloque. Las funciones y

los bloques de funciones son contextuales para el proyecto,

dispositivo o recurso seleccionado, se agrupan segn su mbito o

categora, y los usuarios tambin pueden buscar el nombre del

bloque.

El Monitor de Bloqueo de Variable muestra una lista de todas las

variables bloqueadas.

La funcin de Estado del Controlador proporciona a los usuarios

informacin fundamental sobre su controlador, como la versindel proyecto que estn ejecutando, as como el tiempo de ciclo y

el nmero de variables bloqueadas.

El nuevo Firmware C5 versin 5.3 incorpora nuevas plantillas,

como plantillas de Microsoft Windows y Linux par alas nuevas

funciones Interrupciones de Usuario y Failover (Cambio de

Unidad). Otras funciones nuevas son las prioridades de SFC paratransicin simultnea en caso de divergencia OR.

ISaGRAF 6.1 sigue incorporando una versin gratuita que

consiste en el firmware gratuito ISaGRAF ejecutado en XP


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Embedded, Windows XP de 32 y 64 bit, Windows Vista y

Windows 7, as como una versin totalmente funcional del

workbench ISaGRAF 6.1 mediante el cual los desarrolladores

pueden crear aplicaciones completas. El firmware gratuitoISaGRAF incluye un Modbus TCP Cliente y un Modbus TCP

Servidor.

Acerca de ISaGRAF v6.1

ISaGRAF 6.1 Workbench es un entorno modular y flexible que

permite a los usuarios aadir o eliminar componentes. Cadacomponente del Workbench ha sido desarrollado e interacciona

con la tecnologa de ISaGRAF basada en Microsoft .NET

Framework y denominada Automation Collaborative Platform

(ACP). ISaGRAF ACP ofrece la posibilidad de aadir o eliminar

varios plug-ins con el fin de cubrir los requisitos de cada producto.

Documents

DISTRIBUTED CONTROL STANDARD CONNECTS INDUSTRY REGARDLESS OF BUS.docx