Automatic Control System
VII.
Controller
Structure of control system
Control software
actuating
drive
controller
actuating
unit
actuator
transducer
sensors
Process
the name of
mathematical
model of
the plant
transmitter
Standard signals
operator desk
Standard industrial
I/O interface
Visualisation software
SCADA (Supervisory control and data acquisition)
Material flow
Simulation software
Variables
Process controller and typical application field
• Process controller
ready to use for industrial control and it’s possible the
hardware redundancy and integrate the functionality of
control and SCADA software.
• Application field
process industry applications (paper, primary metals, food
processing, and so on.)
batch-type control (chemicotechnology, pharmaceutic
chemistry, or injection molding machines, and so on.)
• Programmability
standard control languages IEC1131-3 and SCADA
depending of factory
PLC familyes
• Control relays
8-20 I/O, limited memory size, only LD programming
languages with limited and not standard instructions.
• Compact PLC
12-32 I/O, normal memory size, standard IL, LD, FBD
programming languages with limited instructions.
• Modular PLC with compact unit
flexible arrangement up to 800 I/O, different memory size,
standard IL, LD, FBD programming languages.
• Modular PLC with rack system
Higher I/O number, memory size, CPU frequency, network
ability. All standard programming languages are used.
Structure of modular PLC
Programming device
CPU module
Local extension I/O module
Network station
Remote extension I/O module
Network arrangement
Remote Clients
Workplaces
Maintenance
Operator
Engineering
System Servers
Control Network
Process Automation
Process
Automation and
Safety
S800 I/O
Variable Speed Drives
S900 I/O (Ex)
MCC
Fieldbus High Speed
Linking Devices
(FF HSE/H1, PB DP/PA)
Safety
AC 700F kontroller V9.1
Local I/O Modules
(Up to 8)
CPU (“PM 783F”)
Field Bus Coupler
Connector *
24 VDC
Power connector
FBP (Field Bus
Plug) *
CPU Terminal base
Ethernet
(“TB 711F”)
(RJ-45)
© ABB Group
March 23, 2016 | Slide 8
RS232/485
SER (MODBUS)
RS232/485
DIAG
I/O Terminal Units
(up to 8)
Industrial software
• Simulation software
Facilities: Involving differential equations, matrix, etc.
Converting between frequency and time domain.
Charting functions.
Creating block models.
• Control software
Content of control task for industrial computer (process
control), or intelligent devices in laboratory (scope,
frequency generator, power supply, etc.)
• Visualisation software
Instead 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
manipulated
variable
Controlled, measured
variable
action
signal
feedback
signal
max
max
20 mA
20 mA
A/D conversion
control task
D/A conversion
Domain of
variability
4 mA
4 mA
min
min
w(t ){dim}  wmin {dim}
 w(t )
1{dim}
Program structure of PLC control program
Priority
Deafault
task
Periodic
task
Program A1
Function block 1
Function 1
Program An
Function block 2
Program P1
Function x
Program Pn
Data FB1/1
Data FB1/2
Data FB1/3
Function block N
Function N
Event
task
System
task
Program E1
Program En
Program R1
Program Rn
The system programs handle the
error, keep the connection with
operator, and so on.
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
D
P
E
S
A1 A2 A3 A1
A2 A3 A1A
P1
AA3 A1 A2 A3 A1A
P
AA3 A1 A2 A3
P
t
t
t
E1
R1
t
Cyclic processing of the user program
not use loop instruction (for, until..)
at the end the program the processing starts again automatically
Standby PLC
interrupt
selftest
Write data
Read data
Process user program
The standard control languages
IEC1131-3
• Structural Text
similar to QuickC
• Instruction Line
similar to assembly
• Ladder Diagram
graphical language similar to contact plan
• Function Block Diagram
graphical language similar to digital circuit plan
• Function Chart
graphical language and text languages by IEC848 standard
Structure of Instruction line
Label
Instruction
Symbolic name
for variable
Comment
These are always required
It is used like the target of
It relates to the variable.
the jump instructions.
Jumps
Calls
Label
Symbolic name
for function block
or function
Structure of jump’s instructions
A
A
yes
no
jump conditional
no
yes
B
jump unconditional
B
C
label yes
C
D
label unconditional jump
D
Structure of Call’s instructions
Data_2
call name
Data_1
Function
block
User
program
return
The same type of function blocks or
functions can be called more times
with different name and so data block.
The call’s instructions can be used in
the function block program too.
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
ST
In all scan the output result depends on the actual value of
the contacts.
• Set
S
In 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.
• Reset
R
In 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
Sequence
Smallest 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
The relaycoil1 is energised if the
contact1 and the contact2 are closed.
OR
The relaycoil2 is energised if the
contact1 or contact2 are the closed.
XOR
The relaycoil3 is energised if either
the contact1 or the contact2 are
closed.
Circuit connections
between ends
AND
OR
XOR
Sequence
LD contact1
AND contact2
ST relaycoil1
LDN contact1
OR contact2
ST relaycoil2
LD contact1
XOR contact2
ST relaycoil3
Logical closed
instruction series
LD contact1
ANDN contact2
LDN contact1
AND contact2
OR
ST relaycoil3
Structure of Ladder diagram
Type
Suggested flowchart of the PLC program
conditions
conditions
Actions
Jump’s label
Call’s name
Actions
conditions
Actions
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
Steps of creating control program
• Flowchart of the program
define input, output, and internal variables
• Hardware topology file
• Edit program file and reference file
definition of variables, edit program, syntax check
• Compile editing program
convert to machine code, error massages
• Transfer (download) to PLC
• Test and commissioning
start/stop program running, display program in running
• Modify program