Transcript 14. - CT Johnson, Inc

FieldBus, the wave of the future
But I do not recommend it for every system.
It should not be used for systems with
less than 100 control loops
PC-ControLAB
The primary reason that the field bus was develop was
to save construction cost of wiring individual field devices
back to I/O Cabinets that were used in the early Days
of the DCS and PLC. However, it turned out that the
construction costs were offset by the increase in engineering
Presentation by Clifford T. Johnson, PE, Control Systems Engineer
Fieldbus
Fieldbus
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Assignment & Lab
•FieldBus, the wave of the future
•PC-ControLab: Tuning demo
Today
Assignment & Lab
ELC-213
AS-i (Actuator Sensor Interface)
AS-i is the easiest network to install
ASi
Bus
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AS-i is simply 2 wires
AS-i primarily operates On-Off
ball valves that incorporate
a rotary valve monitor that is
addressed using
5 position dip switch
ASi
IS Easiest to install
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AS-i Network Highlights
Technology Developer AS-i Consortium Introduced 1993
Openness Multiple vendors, 800+ products, 150 Vendors
Type of Network Sensor Bus
Physical Media 2-wire cable (flat or round)
Network Topology Bus, Ring, Tree, Star
Maximum Devices
- v2.0 31 nodes (or 248 I/O points)
- v2.1 62 nodes (or 434 I/O points)
- Maximum Distance 100 meters
- Maximum Distance with repeaters 300 meters
(max. of 2 repeaters can be used)
AS-i is the easiest network to install
ASi
Highlights
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Foundation Fieldbus Technology
(FFB)
Fieldbus provides two-way, multi-drop digital communication
between devices on the plant floor as well as the automation
and display systems. Thus, FFB is essentially a Local Area
Network (LAN) for field devices.
Fieldbus
Process Plant
P
Automation
and
Display Systems
L
F
Foundation
Fieldbus-USA
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6
FFB Plant Network Hierarchy
Plant
Network
Local Area
Network
Fieldbus
Network
Office Automation
• Mainframes
• Management
Automation & Display Systems
• DCS’s, PLC’s, PC’s
• SCADA, Supervisory Systems
Instrumentation & Control
• Transmitters, Controllers
• Valves & Actuators
FFB is the only Fieldbus that provides power to
the devices and that makes it
very difficult to design & Install
Foundation
Hardest to install
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ProFiBus
Process Field Bus
SIEMENS
SIEMENS
ET200C
ET200C
R
Star
Bus
Line
Ring
RS 485
FO
IEC 1158-2
ProFiBus
Best overall
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DeviceNET
DeviceNET
By Allen-Bradley
ELC-213
Allen-Bradley Developed DeviceNET
DeviceNET
For motor controls
ELC-213
What is Ethernet?
• The IEEE recognizes Ethernet as standard
IEEE802.3
• Defines layers 1 & 2
• Layer 1 defines cables, connectors &
electrical characteristics
• Layer 2 defines frame format, error
checking, and physical addressing
(MAC – Medium Access Control)
• The technology that Ethernet uses to
determine when nodes can transmit is
Carrier Sense, Multiple Access, with
Collision Detection or CSMA/CD
Ethernet
Not for process control
7
Application
6
Presentation
5
Session
4
Transport
3
Network
2
Data Link
1
Physical
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How does CSMA/CD work?
• Carrier Sense, Multiple Access, with
Collision Detection (CSMA/CD) is a
contention based access method:
Average and
Standard Deviation
determined
by network loading
– Carrier Sense: listen before sending
– Multiple Access: any device can send data
if it doesn’t detect a “busy” signal.
• CSMA is analogous to many speaker
phones where only one person can talk
at a time
• Collision Detection senses when two nodes
attempt to transmit simultaneously
• When a collision is detected, both nodes stop
and wait a different, specified, period of time
before retrying
• This is the underlying reason that
Ethernet is termed non-deterministic
Ethernet
Non Deterministic
Std. Dev.
_
X
Transmission speed
(msec)
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Ethernet – Myth vs. Reality?
• Myth: Non-determinism: Any Ethernet network loaded above 40%
will experience an exponential growth in transmission delay times
and become non-operational.
• Reality: Ethernet delays are linear and can be consistently
maintained under 2 ms for a lightly loaded network and 30 ms for a
heavily loaded network.
• These delays are inconsequential for most process control
applications and can be minimized by using switches and routers to
manage network topology.
However, Critical Control & Safety Systems do not use
Ethernet because it is Non-deterministic
Ethernet
Not for safety systems
ELC-213
Fieldbus Types
Type of
Control
Hardest
Fieldbus
Best
Overall
Process
Control
• IEC/ISA SP50
• Fieldbus Foundation
• Profibus PA
• HART
Devicebus
Sensorbus
Logic
Control
Easies
t
• Seriplex
• ASI
• INTERBUSLoop
Low-end
bit
Simple Devices
Summary
• Device Net
• SDS
• Profibus DP
• LONWorks
• INTERBUS-S
Type of
Devices
High-end
block
Midrange
byte
Complex Devices
FieldBUS Types
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PC-ControLAB
PC-ControLAB is a active demonstration of a
control Station that allows you to "TUNE" a
simulated controller and view the results.
you will download from resources the instructions
for tuning a flow, Temperature and Pressure loop for
optimum controls, then enter the tuning parameters
on an email to me as FLOW: Gain= XX; Reset=
XX; (derivative is not used) then the same for
PRESS & TEMP
Demo
PC_ControLAB
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PC-ControLAB
•User-friendly interface resembles a control station.
•Auto/Manual mode selection buttons and indication
•Set point and output entry via "jog" buttons or move
Pointer
•Tuning permits entry of Proportional Band in % and
Reset in repeats/min.
•Load control buttons permit forcing a step change or
enabling automatic load changes.
• You should simulate a load change by simply changing
the set point
Demo
PC_ControLAB
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PC-ControLAB
Control menu permits selection of control strategies:
•Feedback
•Override (Selector)
•Dual Feedback
•Two forms of Feedforward
•Ratio
•Two forms of Decoupling
•Cascade
•Four forms of Model-Based Control
Demo
PC_ControLAB
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PC-ControLAB
Demo
PC_ControLAB
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Homework ASSIGNMENT Web Link
Find a site of a Pressure Transmitter that works on
Foundation Fieldbus. email web page LINK only to me
by Sunday
All Emails Subjects and File names must have
Subject:Your last Name-Subject-Assignment Date (AD)
Email Ex:
Johnson-Fieldbus PT-AD
Lab: Johnson-PC_ControLab-AD
You will lose 1-3 points for incorrect subject
Subjects
Assignment
ELC-213
The End
Almost
Done
The End
Instrumentation
ELC-213