LEC-02 IEC 61131-3 Programming Standard Rev3 PDF

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21/09/2015

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IEC 61131-3 Standard Programming Environment for Industrial Control Applications

Information courtesy of PLCopen (www.plcopen.org)

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Yesterday’s Reality • Industrial control of a plant was not unique to one manufacturer’s equipment. • Even when manufacturer’s used the same programming language the differences in syntax were significant. (eg. PLC ladder logic I/O addressing) • Development of software in one vendor’s equipment could not be easily transported to another vendor’s equipment.

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How to solve the problem? • Standards – agreement by all players in the industrial control business to comply with an international programming standards. • Standard is rigid enough to ensure consistency of the programming environment while not constraining vendors from producing unique product. • Strongly supported by end-users. Why?

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Benefits of a Standard • Programming techniques learned for one environment are easily transportable to new environments. • A common programming standard reduces the time required for training, troubleshooting or maintaining industrial control systems. Avoids need for re-training. • Allows control systems experts to focus on solving a problem via software and allows this software to be re-used (reduces dependency on one supplier). • Improves the ability to integrate components from different vendors, locations, projects or countries. 02 – IEC 61131-3 Standard ELEX 4221

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What exactly is IEC? • International Electrotechnical Commission (IEC) – Non-profit; not government related; • Produces standards that provide guidelines for virtually every aspect of electrical, electronics and related technologies. • IEC membership: representatives from over 70 countries. Each country is represented by its “national committee”. • Standards are prepared by people that are working in the relevant industry and knowledgeable about the technology and users’ needs. 02 – IEC 61131-3 Standard ELEX 4221

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IEC 61131-3 • Programming Languages / Industrial Control Programming • 61131 Standard is comprised (at this time) of 7 parts: 1. 2. 3. 4. 5. 7. 8.

General Overview / Definitions Hardware Programming Languages User Guidelines Communication (Messaging Service Spec) Fuzzy Logic Implementation Guidelines

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Consistency / Reliability The programming standard significantly contributes to the consistent and reliable execution of industrial software configurations because it addresses key issues such as: 

execution control

   

structured software software encapsulation (re-use code) data type definitions and constraints addresses complex sequential behaviour

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Components of IEC 61131-3

1. Programming Languages     

Ladder Logic Diagram (LD) Instruction List (IL) Structured Text (ST) Function Block Diagrams (FBD) Sequential Function Charts (SFC)

2. Common Elements (re: the programming languages)

 Data types  Standard Functions  Function Blocks 02 – IEC 61131-3 Standard ELEX 4221

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Ladder Logic Diagram • Based on the well-known North American PLC programming language. • The standard specifies a standardized, rationalized set of relay ladder logic programming symbols.

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Instruction List • Similar to assembly language programming. • Single accumulator-based execution model. • Only one operation is allowed per line of code (eg. Loading a value into the accumulator)

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Structured Text • • • •

High level language, block structured. Includes functions such as ABS(), SIN(), SQRT() Similar to Pascal (or Basic). Complex statements and nested instructions are possible (supports if-then-else, while-do, etc.)

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Function Block Diagram • Graphical language • Similar to LabView • Allows program elements which appear as blocks to be “wired” together. • Used in many applications that involve the flow of data between control components.

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Sequential Function Chart • Graphical language showing logic flow sequence (flowchart like). • Basic elements are steps with action blocks and transitions. • Steps are program code that is executed until transition occurs. • Complex task broken down into smaller parts. 02 – IEC 61131-3 Standard ELEX 4221

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Standard Data Types • • • • • •

Bit string types: BOOL, BYTE, WORD, DWORD, LWORD Integer types: INT, SINT, DINT, LINT Unsigned Integer types: USINT, UINT, UDINT, ULINT Real types: REAL, LREAL Time/Date types: TIME, DATE, TIME_OF_DAY Character types: STRING, WSTRING

• Vendor and user defined data types are possible.

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Variables • • • • •

Global Direct (local) I/O Mapping  Input, Output, I/O External Temporary

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Standard Functions (Program Organization Units) • • • • • •

Bit string functions: AND, OR, NOT, XOR, SHL, SHR, ROR, etc. Numerical Functions: ADD, SUB, MUL, DIV, ABS, SQRT, LN, etc. Type conversions: USINT_TO_DINT, BOOL_TO_BYTE, etc. Selection functions: MIN, MAX, LIMIT, MUX, SEL Comparison functions: GT, GE, EQ, LT, LE, NE String functions: LEFT, RIGHT, MID, CONCAT, INSERT, DELETE, etc.

Vendor and user defined functions are possible.

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Standard Function Blocks • Bistables (latches or flipflops):

SR, RS

• Edge detection: R_TRIG, F_TRIG • Counters:

CTU, CTD, CTUD

• Timers:

TP, TON, TOF, RTC

• Vendor and user defined functions are possible (custom).

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IEC 61131-3 Software Model from presentation by Eelco van der Wal (PLCopen) Configuration Resource

Variable access path

Resource

Task

Task

Task

Task

Program

Program

Program

Program

FB FB

Function FB Block Variable

FB FB

Global and direct variables

Execution control path

Access path Communication Function 02 – IEC 61131-3 Standard ELEX 4221

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IEC 61131-3 Software Model

A typical microprocessor-based system could be viewed as being a resource (the microprocessor) with a task (the program it executes).

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IEC 61131-3 Software Model Configuration

The complete software package / database required to solve the industrial control problem is referred to as the “configuration”. Communication Function 02 – IEC 61131-3 Standard ELEX 4221

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IEC 61131-3 Software Model - DeltaV Example Configuration

DeltaV Configuration (all hardware, software and field devices).

This would be like a complete DeltaV configuration including all hardware and software.

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IEC 61131-3 Software Model Configuration

Resource

Resource

The “resources” are the hardware (computational) components of the system).

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IEC 61131-3 Software Model - DeltaV Example Configuration

ProPlus Station

DeltaV Hardware (CPU & I/O Rack) Resource

Resource

The resources, in a DeltaV configuration , could be multiple DeltaV hardware racks (controller and I/O, the ProPlus and/or intelligent field devices.

Communication Function 23

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IEC 61131-3 Software Model Configuration Resource Task

Resource Task

Task

Task

A “task” controls the different parts (sections) of a program required to accomplish the industrial control objective.

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IEC 61131-3 Software Model - DeltaV Example Configuration Resource

Resource

Task

Task

Control Module

Control Module

KC-1107

FC-1115

Task

Task

Control

Control Module

Module ZC-2128

TC-2104

Access path Communication Function 25

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IEC 61131-3 Software Model Configuration Resource

Resource

Task

Task

Task

Task

Program

Program

Program

Program

A “program” is the software written to execute the industrial control strategy and may be in any one of the 5 programming languages. Execution control path

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IEC 61131-3 Software Model - DeltaV Example Configuration Resource

Resource

Task

Task

Task

Task

Program

Program PID FBD

Program Struct. Text

Program

SFC

PID FBD Execution control path

Access path Communication Function 27

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IEC 61131-3 Software Model from presentation by Eelco van der Wal (PLCopen) Configuration Resource

Variable access path

Resource

Task

Task

Task

Task

Program

Program

Program

Program

FB FB

Variable

FB FB

Global and direct variables

Access path Communication Function 02 – IEC 61131-3 Standard ELEX 4221

Function Block FB

Execution control path

Data is exchanged using global or direct variables.

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IEC 61131-3 Software Model from presentation by Eelco van der Wal (PLCopen) Configuration Resource

Variable access path

Resource

Task

Task

Task

Task

Program

Program

Program

Program

FB FB

Function Block FB Variable

FB FB Execution control path

Global and direct variables

Access path Communication Function

This would be an early model PLC.

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Example

Fermentation Control System

courtesy of Omron Electronics

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Fermentation Process Agitator

Feed valve Acidic reagent Alkali reagent

Temperature sensor pH sensor

Heater band

Harvest valve

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Fermentation Control Decomposition • MainSequence • Valve control

e.g. top level process steps - filling, heating, agitating, fermenting, harvesting, cleaning. e.g. operating valves used to fill and empty the fermentation vessel

• Temperature control for monitoring the temperature of the vessel and modulating the heater. • Agitator control for the agitator motor activated as demanded by the main process sequence.

• pH Control

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for monitoring the acidity of the fermentation contents and adding acidic or alkali reagents.

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Fermentation Control Program

Function Block Programming

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Main Sequence SFC S1

Sequential Function Chart Programming

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Initialisation

S2

N

Filling

S3

N

Heating

S4

N

Fermenting

S5

N

Harvesting

S6

N

Cleaning

Shows the main process states Indicates current active state and transition condition to be completed

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