Automatic Control System

VII.

Controller

transmitter

actuator

Structure of control system

Process

the name of mathematical

model of the plant

Material flow

sensorstransducer

actuatingunit

actuatingdrive

controller

operator desk

Visualisation softwareSCADA (Supervisory control and data acquisition)

Simulation software

Control software

Standard signals

Variables

Standard industrialI/O interface

Process controller and typical application field

• Process controllerready to use for industrial control and it’s possible the hardware redundancy and integrate the functionality of control and SCADA software.

• Application fieldprocess industry applications (paper, primary metals, food processing, and so on.)batch-type control (chemicotechnology, pharmaceutic chemistry, or injection molding machines, and so on.)

• Programmabilitystandard control languages IEC1131-3 and SCADA depending of factory

PLC familyes

• Control relays8-20 I/O, limited memory size, only LD programming languages with limited and not standard instructions.

• Compact PLC12-32 I/O, normal memory size, standard IL, LD, FBD programming languages with limited instructions.

• Modular PLC with compact unitflexible arrangement up to 800 I/O, different memory size, standard IL, LD, FBD programming languages.

• Modular PLC with rack systemHigher I/O number, memory size, CPU frequency, network ability. All standard programming languages are used.

Structure of modular PLCProgramming device

CPU module

Local extension I/O module

Network station Remote extension I/O module

MCC

Variable Speed Drives

S800 I/O

S900 I/O (Ex)

Workplaces

Control Network

Remote Clients

System Servers

Fieldbus High Speed Linking Devices(FF HSE/H1, PB DP/PA)

Process Automation Process Automation and Safety

Operator EngineeringMaintenance

Safety

Network arrangement

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roup

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e 8

CPU Terminal base

(“TB 711F”)

CPU (“PM 783F”)

Local I/O Modules (Up to 8)

I/O Terminal Units

(up to 8)

FBP (Field Bus Plug) *

RS232/485

DIAG

RS232/485

SER (MODBUS)

Field Bus Coupler Connector *

Ethernet

(RJ-45)

24 VDC

Power connector

AC 700F kontroller V9.1

Industrial software

• Simulation softwareFacilities: Involving differential equations, matrix, etc. Converting between frequency and time domain. Charting functions.Creating block models.

• Control softwareContent of control task for industrial computer (process control), or intelligent devices in laboratory (scope, frequency generator, power supply, etc.)

• Visualisation softwareInstead of classic operator desk (push button, dial indicator)

Control software

Control software needs a model of the process• Define correct interface between process and controller.

(using standard signals)

• Dividing into simpler part of the process.

• Choosing control strategies.

• Creating control task, and define the parameters.

Standard industrial I/O interface for signals

Digital I/O

• galvanic isolation

• 24 VDC logic (0 -7 VDC , 14 - 30 VDC)

Analogue I/O

• Usually no galvanic isolation

• Typically: 4-20 mA signal area

• Typically resolution: 12 bit

Dimensionless technique

)({dim}1

{dim}){dim}( min twwtw

Controlled, measuredvariable

feedbacksignal

actionsignal

manipulatedvariable

A/D conversioncontrol task

D/A conversion

max

min

20 mA

4 mA

max

min

20 mA

4 mA

Domain ofvariability

Program structure of PLC control program

Deafault task

Periodictask

Eventtask

Systemtask

Priority

Program A1

Program An

Program E1

Program En

Program Rn

Program R1

Program Pn

Program P1

Function block 1

Function block N

Function N

Function x

Function 1

Data FB1/1Data FB1/2Data FB1/3

The system programs handle the error, keep the connection with operator, and so on.

Function block 2

Programs, function blocks, functions

• The programs can be written any standard languages. Different languages can be used in the project.

• The function blocks and the function are well tested subprograms.

• The function blocks have more input and more output variables, which can be catch from any programs.

• The functions have more input and one output variables. The output variables appear in the working register of CPU and needs handle.

How the programs use the CPU

t

t

t

t

D

P

E

S

A1A2A3A1

P1

A2A3A1A

P

E1

P

AAA3A1A2A3A1

R1

A3A1A2A3A

Cyclic processing of the user programnot use loop instruction (for, until..)

at the end the program the processing starts again automatically

Write data

interrupt

Standby PLC

selftest

Process user program

Read data

The standard control languagesIEC1131-3

• Structural Textsimilar to QuickC

• Instruction Linesimilar to assembly

• Ladder Diagramgraphical language similar to contact plan

• Function Block Diagramgraphical language similar to digital circuit plan

• Function Chartgraphical language and text languages by IEC848 standard

Structure of Instruction line

Label InstructionSymbolic name

for variableComment

These are always requiredIt is used like the target of the jump instructions. It relates to the variable.

Jumps Label

CallsSymbolic name

for function block

or function

Structure of jump’s instructions

A

CB

D

yes

label yes

yes jump conditional

A

no

label unconditional jump

no

jump unconditional

B

C

D

Structure of Call’s instructions

Userprogram

Functionblock

Data_1

Data_2call name

The same type of function blocks or functions can be called more timeswith different name and so data block.

The call’s instructions can be used inthe function block program too.

return

Instructions of IEC1131-3

• LD, LDN

• S, R

• ST, STN

• AND, ANDN

• OR, ORN

• XOR, XORN

• LT, LE, EQ, EN, GE, GT

• JMP, JMPC, JMPCN

• CAL, CALC, CALCN

• RET, RETC, RETCN

all variables

bool variables

all variables

bool variables

bool variables

bool variables

all variables (the result is bool)

label

name of function block or

function

Store, Set, Reset output instructions

• Store STIn all scan the output result depends on the actual value of the contacts.

• Set SIn the first scan when the logical result of contacts actual value equals true the output register (variable) is set high, and remains in this state independent the contacts actual value until a reset instruction.

• ResetRIn the first scan when the logical result of contacts actual value equals false the output register is reset

Variables of IEC1131-3• BOOL

• BYTE, WORD, DWORD

• integer (INT), short integer (SINT), double integer (DINT), unsigned integer (UINT), ...

• REAL

• TIME

• DATE

• TIME_OF_DAY

• DATE_AND_TIME

• STRING

bool variables

bit sequence variables

digital variables

real number

T#0h0m0s0ms

D#1900-01-00 (YYYY-MM-DD)

TOD#00:00:00 (HH:MM:SS)

DT# 1900-01-00-00:00:00

Structure of Instruction line program

SequenceSmallest part of a instruction line program the sequence consisting of one or more instruction line.

Syntactic of sequence– Started one load instruction (LD, LDN) and

finished one or more result instruction (ST, STN, S, R, JMPC, JMPCN, CALC, CALCN).

– Inside the sequence the type of the variables is the same.

– JMP, CAL, RET are the one line instructions.

Bool algebra

AND

OR

XOR

The relaycoil1 is energised if the contact1 and the contact2 are closed.

The relaycoil2 is energised if the contact1 or contact2 are the closed.

The relaycoil3 is energised if either the contact1 or the contact2 are closed.

Sequence

AND

OR

XOR

LD contact1

AND contact2

ST relaycoil1

LDN contact1

OR contact2

ST relaycoil2

LD contact1

ANDN contact2

LDN contact1

AND contact2

OR

ST relaycoil3

LD contact1

XOR contact2

ST relaycoil3

Circuit connections between ends

Logical closed instruction series

Structure of Ladder diagram

Type

Suggested flowchart of the PLC program

If the result of the conditions is false the actions aren’t processed and begins automatically examination of the next conditions.

The jumped actions aren’t processed. It remains the latest value.

There aren’t conditions before JMP, CAL instructions

Actions

conditions

conditions

conditions

Actions

Actions

Jump’s labelCall’s name

Steps of creating control program • Flowchart of the program

define input, output, and internal variables

• Hardware topology file

• Edit program file and reference filedefinition of variables, edit program, syntax check

• Compile editing programconvert to machine code, error massages

• Transfer (download) to PLC

• Test and commissioning start/stop program running, display program in running

• Modify program