Snímky ze 2. přednášky Soubor

12.10.2015
Průmyslová informatika a
internet
(A0M35PII)
Přednáška 13.10.2015
Přednáška používá některé materiály od:
Prof. Dr. H. Kirrmann: Automation Industrielle,
EPFL / ABB Research Center, Baden, Switzerland 2010
Richard Šusta
Example: Rockwell (Allen-Bradley) NetLinx
Programmabl
e Device
Support PC
Desktop
PC
with excel
EtherNet / IP
Controller and Bridge
Servo
ControlNet
Linking Device
HMI
Bridge or Linking Device
Drive
HM
I
DeviceNet
Modular
I/O
509 -BOD
24vdc
Micro
PLC
Sensor
Block I/O
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12.10.2015
Centralized (Hierarchical) Control Architecture
Central Computer
(Mainframe)
Group
Group
Group
Control
Control
Control
Sensors, Actors
PLCs
plant
Classical, hierarchical, centralized architecture.
The central computer only monitors and forwards commands to the PLCs
P2P komunikace
communication in a control system is evolving from hierarchical to distributed
central master / slave: hierarchical
PLC
“master”
peer-to-peer: distributed
alternate
master
“slaves”
input
PLC
PLC
AP
separate bus master from
application master !
AP
AP
output
“masters”
AP
input
PLC
“slaves”
PLC
AP
output
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12.10.2015
ALLEN-BRADLEY
ALLEN-BRADLEY
ALLEN-BRADLEY
Decentralized Control System (DCS)
hierarchical
(vertical communication)
engineering
workstation
operator
workstation
data logger
peer-to-peer (horizontal communication)
plant bus
controller
controller
controller
controller
field bus
plant
all controllers can communicate as peers (without going through a central
master), restricted only by throughput and modularity considerations.
Note: Honeywell's "DCS™" stands for "Distributed Control System", it is not a decentralized control
system, but a control system for the process industry.
Sítě – to je směs protokolů SCADA
control
center
IEC 870-6
Modicom
control
center
IEC 870-5
DNP 3.0
RTU
COM
Příklad:
Elektrárna
RTU
Inter-Control Center Protocol
ICCP
Conitel
control
center
RP 570
RTU
HV
High
Voltage
serial links (telephone)
RTU
Remote Terminal Units
RTU
substation
substation
MV Medium
Voltage
FSK, radio, DLC, cable, fiber,...
houses
RTU
RTU
RTU
RTU
LV
Low
Voltage
Pro pomalé rychlosti a velké vzdálenosti lze použít silové rozvody nebo telefonní linky
Problem: rozmanitost protokolů, dotových formátů, semantik..
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3
12.10.2015
Lokální / Distribuované moduly
Ale počet I/O bodů zůstává,
energie se dodává mnoha malým zařízením
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Adresy dat PLC

Logické
 pevné
I/O tabulky, do kterých se mapují
vstupy a výstupy
 proměnlivé logické tabulky, podle vstupů a
výstupů

Systémy používající Tagy
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12.10.2015
Logické I/O adresy
Allen-Bradley – PLC5, SLC500
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Pevné vstupní a výstupní tabulky
Image courtesy of Allen-Bradley, a Rockwell Automation business
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5
12.10.2015
Data v pevných tabulkách
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Single-slot Addressing
Logical Rack 0
000
001 002 003
004 005
Logical Rack 1
006 007 010 011
012 013 014
015 016
017
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12.10.2015
Two-slot Addressing
Logical Rack 0
000
000 001 001
002 002
003 003
004 004 005 005 006
006
007 007
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Half-slot Addressing
Logical Rack 0
000 002
001 003
004 006
005 007
Logical Rack 1
010 012
011 013
Logical Rack 2
014 016 020 022
015 017 021 023
Logical Rack 3
024 026 030
025 027 031
032 034
033 035
036
037
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12.10.2015
Addressing and Remote I/O
Logical Rack 0
Logical Rack 1
Rack 2
000 001 002 003 004 005 006 007 010 011 012 013
P
r
o
c
e
s
s
o
r
1336
Plus II
VFD
P
o
w
e
r
S
u
p
p
l
y
Remote I/O
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Modulární PLC SLC 500
Image courtesy of Allen-Bradley, a Rockwell Automation business
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Tabulka vytvářena modulem
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Modularní PLC a I/O tabulky
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Přenosy dat – scanované a nescanované vstupy
Vstupní force
I/O modul
-|0|1
Scan vstupů
Scanované
vstupní
hodnoty
Okamžitý scan
Vstupní
hodnoty
čtené
povelem
Obraz vstupů
Tabulka proměnných
programu
Čtení bloku dat
Force aktivní?
Ano / Ne
synchr./asynchr.
Výstupní
hodnoty
zapisované
povelem
Zápis bloku dat
Scanované
výstupní
hodnoty
Obraz výstupů
Okamžitý scan
0|1
Scan výstupů
Výstupní force
-|0|1
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Tagově orientovaná PLC
Program
Tagy
vstupních
modulů
Vstupy
Private
Shared
Data
Tagy
výstupních
modulů
Consumed
tagy
Produced
Tagy
Výstupy
I/O Update Manager
Local bus
I/O moduly
Remote I/O
moduly
Te c h n o lo g ic k ý p r o c e s
Remote
tagy
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12.10.2015
Klasické PLC / ControlLogix
src x1
src x2
x1
x2
src xm
xm
src x1
t in
src x2
src xm
t prog
Program
t plcscan
dst y1
dst y1
dst y2
dst yn
y1
y2
yn
dst y2
t out
dst yn
t x1
x1
t x2
x2
t xm
xm
t y1
y1
t y2
y2
P
r
o
g
r
a
m
t prog
t yn
yn
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Data Types
Using these definitions . . .
Controller Memory
“Drive_Speed” Data
DINT, or 32 Bits
“Start” Data
BOOL, or 1 Bit
“Sensor”
Data
BOOL or
1 Bit
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12.10.2015
Identifying a Module Type
Several characteristics:
RSLogix 5000
Software I/O
Configuration
I or O for Input or Output
A for AC, B for DC, F for Fast Response Analog
Number of Points or Channels
Suffix – (Diagnostic, Electronic
Fusing, Individually Isolated,
Voltage Only, Current Only, etc.)
1756 - O B 16 D
Module Slot Number
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Identifying an I/O Module Tag
I/O format:
Location:Slot:Type.Member.Bit
I/O Point (Optional)
“Data” (I/O values), “Fault,” etc.
“I” for Input, “O” for Output,
“C” for Configuration
Module Slot Number
“Local” or Module Name for Remote
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12.10.2015
Example: Digital I/O Tags
Digital output module in slot 0 of local chassis:
1756-OB16D Module – Slot 0
Diagnostic
Data
Data Per Point
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Types of Scans

Continues task (spojitá úloha)
PLC scans the program code from top to bottom. When it
completes, it goes back to the top and restarts the process.
I/O scans
program scans
1. A continuous task is how PLC traditionally operates.
2. Continues tasks are performed at irregular intervals.
3. A watchdog monitors the scan time. If it exceeds predefined value, an
execution fault is displayed because PLC could accidentally lose an
input signal.
4. First scan (or first pass) – when the PLC is first powered ON or
whenever the PLC program is started – used for initializations
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Types of Scans

Periodic task (periodická úloha)
Like the continuous task, a periodic task executes all of its
code from top to bottom. However, when a periodic task
completes its scan, it waits a preconfigured time interval
before restarting.
program scans
1. A periodic task is always required for all numeric control
algorithms, e.g. PID controller.
2. The periodic task lets you control a process that might occur
at a significantly faster rate than the normal scan of the
continuous task can attain.
3. In a periodic task, we must insert I/O instructions if we need
actual data, otherwise it uses I/O data of the continues task.
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Types of Scans

Event task (úloha řízená událostí, přerušeni)
Lets you execute a piece of code based on the detection of
some incident that occurs in the control system.
Events
Program scans
1. The event task either immediately take control at a high priority
2. But interrupts are potentially dangerous sources of errors
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12.10.2015
Continues, Periodic, and Even Tasks

Picture taken from Rockwell Automation: Using Event Tasks with Logix5000 Controllers,
Publication LOGIX-WP003A-EN-P June, 2003, page 15
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Průmysl potřebuje informace...
1. spolehlivé přenést
2. spolehlivé zpracovat
3. spolehlivě testovat možné chyby
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12.10.2015
The Millennium Bridge London
Slavnostně
otevřen
v sobotu
10.6.2001
Rychle
zavřený
v pondělí
12.6.2001
Přímo učebnicový příklad špatné informace
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Therac 25 – těžká chyba v IS
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12.10.2015
Mask of Therac 25
2 deadly errors escaped detection
 during 2 years testing by the manufacture
 during 2 deep inspections
during deep inspection perform by US government
even if all knew what they should look for
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Operator sidebar
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12.10.2015
Structure of code
[source: Nancy G. Leveson, Clark S. Turner, An Investigation of the Therac-25 Accidents]
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1 of 2 errors
Error is clear only if you know its exact location
Magnet:
Set bending magnet flag
// ..but the flag is reset after 1st call of Ptime
repeat Set next magnet
Call Ptime
if mode/energy has changed, then exit
until all magnets are set
// it takes 8 s to adjust magnets!!!
return
Ptime:
repeat
if bending magnet flag is set then
if editing taking place then // it is tested only if bending magnet flag is set
if mode/energy has changed then exit
until hysteresis delay has expired
Clear bending magnet flag return
2nd more complex error appeared when an operator pressed key in the
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same moment when a byte circular counter overflowed
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