INDUSTRIAL COMMUNICATION
SYSTEMS
Chapter 1. Introduction
Assoc. Prof. Dr. BUI Dang Thanh
School of Electrical Engineering, Hanoi University of Science and Technology
1 Dai Co Viet road, Hà Nôi, Viêt Nam
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Historical Overview of Industrial
Communication System
• At the beginning of 1960, a digital
computer was for the first time applied as a
digital computer
• 1960s, digital communication network for
automation system
• 1970s SCADA
• 1980s DCS
• 2000s IIT, IoT
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Plant hierarchy of Industrial Communication Systems
Office
network
TCP - IP
Ethernet
Plant Network
Ethernet, ControlNet
Fieldbus
intelligent field devices
FF, PROFIBUS, MVB, LON
Sensor Busses
simple switches etc.
CAN, DeviceNet, SDS, ASI-bus, Interbus-S
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What is a Fieldbus?
❑ A Fieldbus is an industrial computer network for real-
time distributed control.
❑ A complex automated industrial system usually
needs an organized hierarchy of controller systems
to function.
❑ Human Machine Interface (HMI) at the top,
Programmable Logic Controllers (PLCs) in the
middle, and the Fieldbus at the bottom.
❑ The Fieldbus links the PLCs to the components
which actually do the work such as sensors,
actuators, electric motors, console lights, switches,
valves, and contactors.
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What is a Fieldbus?
❑ Fieldbus is a generic term that describes a new digital
communications network that is being used in industry to
replace the existing 4-20 mA analog signal standard.
❑ The network is a digital, bi-directional, multi-drop, serial-bus
communication network used to link isolated field devices,
such as controllers, transducers, actuators and sensors.
❑ Bi-directional means it is a duplex port; the data can be
transmitted in two directions at the same time.
❑ Multi-drop is also referred to as multi-access and it can be
interpreted as a single bus with many nodes connected to
it.
❑ Serial-bus means the data is transmitted serially
according to RS232 or RS485 protocol. Profibus uses
RS485 protocol.
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What is a Fieldbus?
❑ Fieldbus works on network structures such as daisy-chain, star,
ring, branch, and tree network topologies.
❑ Previously computers were connected using RS-232 by which
only two devices could communicate.
❑ This is the equivalent of the currently used 4-20 mA
communication scheme which requires that each device has its
own communication point at the controller level
❑ The fieldbus is the equivalent of the current LAN-type
connections, which require only one communication at the
controller level and allow multiple (100's) of analog and digital
points to be connected at the same time.
❑ This reduces both the length of the cable required and the
number of cables required.
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History & Current State
❖ In 1999 a committee formed the IEC 61158 standard
with eight different protocol sets:
◼ FOUNDATION Fieldbus ◼ FOUNDATION Fieldbus
H1 HSE
◼ ControlNet ◼ Interbus
◼ PROFIBUS ◼ SwiftNet
◼ P-Net ◼ WorldFIP
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History & Current State
❑ Recent additions or planned additions to IEC 61158 include but
are not limited to:
❑ PROFINET IO
❑ EtherCAT
❑ Both FOUNDATION Fieldbus and Profibus technologies are now
commonly implemented within the process control field, both for
new developments and major refits. In 2006, China saw the
largest FF systems installations at NanHai and SECCO, each
with around 15,000 fieldbus devices connected
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Who uses Fieldbuses?
• Those who plan complex
automated industrial
systems
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Where are Fieldbuses Used?
➢ In complex automated
industrial systems where an
organized hierarchy of
controller systems is needed.
➢ In manufacturing plants
where many instruments
need to be connected.
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What are Fieldbuses Used For?
❑ When fieldbuses work in the factory, the purpose has been to
reduce installation cost by moving the I/O interface from the
programmable logic controller (PLC) to a remote I/O unit
mounted close to the machine on the factory floor.
❑ Factory automation fieldbuses are fast and deterministic.
(Deterministic means the maximum worst-case time to obtain
data across the fieldbus is accurately predictable and is not
subject to chance.)
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When are Fieldbuses Used?
✓ When the advantages of Fieldbuses,
discussed on the next slide, are needed
✓ When the disadvantages of Fieldbuses, on the
slide after that, do not hinder use
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Advantages of Fieldbus
❑ A major advantage of fieldbus is the capital expenditure
(CAPEX) savings associated with cable elimination; multiple
devices share wire-pairs in order to communicate over the bus
network and savings are also available through speedier
commissioning.
❑ On going maintenance and process control system performance
are significantly enhanced through fieldbus systems, which
results in operations expense savings (OPEX).
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Disadvantages of Fieldbus
❖ Disadvantages of fieldbus compared to the 4-20 mA analog
signal standard:
➢ Fieldbus systems are complex, so more training needed
➢ The price of fieldbus components is higher
➢ Fieldbus test devices are more complex
➢ Device manufacturers have to offer different versions of
devices due to different fieldbus standards. This can add to
the cost of the devices and increases the difficultly of device
selection.
➢ Standards may predominate or become obsolete, increasing
the investment risk.
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Costs
• (CAPEX) Savings
• (OPEX) Savings Typical Modern Industrial System
• Cost of Devices
• Investment Risks
– Engineering costs
– Equipment costs
– Installation costs
– Commissioning costs
– Maintenance costs
– Operating costs
– Inventory costs
– Retooling costs
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Requires Supporting Technology?
• YES
• Fieldbus Components:
– Bus Terminal
– EtherCAT
– Fieldbus Box
– Lightbus
– PC Fieldbus Cards
– Switches
– And more …
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Location of the field bus in the plant hierarchy
File
Edit
SCADA level Operator 23 12 Engineering
4 2 2
33
Plant bus
Programmable
Plant Level Logic Controller
Field bus
Field level
Sensor/
Actor
Bus
Sensor / direct I/O
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Expectations
✓ Reduce cabling
✓ Increased modularity of plant (each object comes with its
computer)
✓ Easy fault location and maintenance
✓ Simplify commissioning (mise en service, IBS =
Inbetriebssetzung)*
✓ Simplify extension and retrofit
✓ Large number of off-the-shelf standard products to build “Lego”-
control systems
✓ Possibility to sell one’s own developments (if based on a
standard)
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The original idea: save wiring
marshalling tray
I/O bar capacity dumb devices
PLC
(Rangierung,
tableau de brassage (armoire de triage)
COM
PLC
field bus
but: the number of end-points remains the same !
energy must be supplied to smart devices
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Marshalling (Rangierschiene, Barre de rangement)
❑ The marshalling is the interface
between the PLC people and the
instrumentation people.
❑ The fieldbus replaces the
marshalling bar or rather moves it
piecewise to the process
(intelligent concentrator / wiring)
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Distributed peripherals
✓ Many field busses are just
extensions of the PLC’s Inputs
and Outputs, field devices are
data concentrators.
✓ Devices are only visible to the
PLC that controls them
relays and fuses
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Field busses classes
Office
network
TCP IP
Ethernet
Plant Network
Ethernet, ControlNet
Fieldbus
intelligent field devices
FF, PROFIBUS PA, LON
Sensor Busses
simple switches etc.
CAN, DeviceNet, SDS, ASI-bus, Interbus-S
The field bus depends on:
its function in the hierarchy
the distance it should cover
the data density it should gather
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Geographical extension of industrial plants
1 km .. 1000 km Transmission & Distribution
Control and supervision of large distribution networks:
• water - gas - oil - electricity - ...
1 km .. 5 km Power Generation
Out of primary energy sources:
• waterfalls - coal - gas - oil - nuclear - solar - ...
50 m .. 3 km Industrial Plants
Manufacturing and transformation plants:
• cement works - steel works - food silos - printing - paper
pulp processing - glass plants - harbors - ...
500m .. 2 km Building Automation
• energy - air conditioning - fire - intrusion - repair - ...
1 m .. 1 km Manufacturing
flexible manufacturing cells - robots
1 m .. 800 m Vehicles
• locomotives - trains - streetcars - trolley buses - vans -
buses - cars - airplanes - spacecraft - ...
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Fieldbus over a wide area: example wastewater
treatment
✓ Pumps, gates, valves, motors, water level sensors, flow meters,
temperature sensors, gas meters (CH4), generators, … are spread
over an area of several km2
✓ Some parts of the plant have explosive atmosphere.
✓ Wiring is traditionally 4..20 mA, resulting in long threads of cable
(several 100 km).
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Fieldbus over a wide area: Water treatment plant
Japan Control Room source: Kaneka, Japan
LAS
Remote
Malaysia SCADA Ethernet
Maintenance
System Bus Monitor
H1 Speed Fieldbus
JB Segment 1 Segment 3 JB
Sub Station
AO
AI
PID
PLC
AO
PID
AI AI AI AI AI AI AI AI PID AO
AO AO
DI M.C.C.
FB Protocol
Converter
JB Segment 2 JB Segment 4 Digital Input/Output
AI AI
S S S S S
AI AI AI PID AI PID AI AI AI AI
AO AO
Numerous analog inputs (AI),
low speed (37 kbit/s) segments merged to 1 Mbit/s links.
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Fieldbus application: Building Automation
Source: Echelon
low cost, low data rate (78 kbit/s), may use power lines (10 kbit/s)
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Fieldbus Application: locomotives and drives
radio power line
cockpit
diagnosis Train Bus
Vehicle Bus
brakes power electronics motors track signals
data rate 1.5 Mbit/second
delay 1 ms (16 ms for skip/slip control)
medium twisted wire pair, optical fibers (EM disturbances)
number of stations up to 255 programmable stations, 4096 simple I/O
integrity very high (signaling tasks)
cost engineering costs dominate
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Fieldbus Application: automobile
- 8 nodes
- 4 electromechanical wheel brakes
- 2 redundant Vehicle Control Unit
- Pedal simulator
- Fault-tolerant 2-voltage on-board power supply
- Diagnostic System
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Application: Avionics (Airbus 380)
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Networking busses: Electricity Network Control:
myriads of protocols
Inter-Control Center Protocol
SCADA
control IEC 870-6 control ICCP control High
HV Voltage
center center center
Modicom IEC 870-5 DNP 3.0 Conitel RP 570 serial links (telephone)
RTU RTU RTU RTU Remote Terminal Units
COM RTU
substation substation
MV Medium
Voltage
FSK, radio, DLC, cable, fiber,... RTU
RTU
houses RTU RTU
Low
LV Voltage
low speed, long distance communication, may use power lines or telephone modems.
Problem: diversity of protocols, data format, semantics...
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The ultimate sensor bus
power switch and
bus interface
requires integration of power electronics and communication at very low cost.
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Engineering a fieldbus: consider data density
(Example: Power Plants)
Acceleration limiter and prime mover: 1 kbit in 5 ms
Burner Control: 2 kbit in 10 ms
per each 30 m of plant: 200 kbit/s
Fast controllers require at least 16 Mbit/s over distances of 2 m
Data are transmitted from the periphery or from fast controllers to higher level, but slower links
to the control level through field busses over distances of 1-2 km.
The control stations gather data at rates of about 200 kbit/s over distances of 30 m.
The control room computers are interconnected by a bus of at least 10 Mbit/s,
over distances of several 100 m.
Planning of a field bus requires to estimate the data density per unit of length (or surface
and the requirements in response time and throughput over each link.
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Assessment
• What is a field bus ?
• Which of these qualities are required:
1 Gbit/s operation
Frequent reconfiguration
Plug and play
Bound transmission delay
Video streaming
• How does a field bus supports modularity ?
• What is the difference between a sensor bus and a process
bus ?
• Which advantages are expected from a field bus ?
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References
• http://en.wikipedia.org/wiki/Fieldbus
• http://www.isa.org/InTechTemplate.cfm?Section=Article_I
ndex1&template=/ContentManagement/ContentDisplay.cf
m&ContentID=60680
• http://www.us.profibus.com
• http://www.easydeltav.com/video/product/foundation_field
bus.asp
• http://www.fieldbus.org/images/stories/newsroom/newslett
er/200702/
• http://www.beckhoff.com/english.asp?embedded_pc/cx10
00_2.htm
• http://ethernet.industrial-networking.com/articles/
articledisplay.asp?id=79
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Thank you for your attention!
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