Plant hierarchy of Industrial Communication Systems

Office
network

TCP - IP
INDUSTRIAL COMMUNICATION Ethernet

SYSTEMS Plant Network

Ethernet, ControlNet

Fieldbus
intelligent field devices
Dr. BUI Dang Thanh FF, PROFIBUS, MVB, LON
School of Electrical Engineering, Hanoi University of Science and Technology
1 Dai Co Viet road, Hà Nôi, Viêt Nam Sensor Busses
simple switches etc.

CAN, DeviceNet, SDS, ASI-bus, Interbus-S

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What is a Fieldbus? What is a Fieldbus?

 Fieldbus is a generic term that describes a new digital

 A Fieldbus is an industrial computer network for real- communications network that is being used in industry to
time distributed control. replace the existing 4-20 mA analog signal standard.
 A complex automated industrial system usually  The network is a digital, bi-directional, multi-drop, serial-bus
needs an organized hierarchy of controller systems communication network used to link isolated field devices,
to function. such as controllers, transducers, actuators and sensors.
 Human Machine Interface (HMI) at the top,  Bi-directional means it is a duplex port; the data can be
Programmable Logic Controllers (PLCs) in the transmitted in two directions at the same time.
middle, and the Fieldbus at the bottom.  Multi-drop is also referred to as multi-access and it can be
 The Fieldbus links the PLCs to the components interpreted as a single bus with many nodes connected to
which actually do the work such as sensors, it.
actuators, electric motors, console lights, switches,  Serial-bus means the data is transmitted serially
valves, and contactors. according to RS232 or RS485 protocol. Profibus uses
RS485 protocol.
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 What is a Fieldbus? History & Current State

 Fieldbus works on network structures such as daisy-chain, star,

ring, branch, and tree network topologies.  In 1999 a committee formed the IEC 61158 standard
 Previously computers were connected using RS-232 by which with eight different protocol sets:
only two devices could communicate.
 This is the equivalent of the currently used 4-20 mA
 FOUNDATION Fieldbus  FOUNDATION Fieldbus
communication scheme which requires that each device has its
own communication point at the controller level H1 HSE
 The fieldbus is the equivalent of the current LAN-type  ControlNet  Interbus
connections, which require only one communication at the  PROFIBUS  SwiftNet
controller level and allow multiple (100's) of analog and digital
points to be connected at the same time.  P-Net  WorldFIP
 This reduces both the length of the cable required and the
number of cables required.

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History & Current State Who uses Fieldbuses?

 Recent additions or planned additions to IEC 61158 include but • Those who plan complex
automated industrial
are not limited to:
systems
 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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 Where are Fieldbuses Used? What are Fieldbuses Used For?

 In complex automated  When fieldbuses work in the factory, the purpose has been to

industrial systems where an reduce installation cost by moving the I/O interface from the
organized hierarchy of programmable logic controller (PLC) to a remote I/O unit

controller systems is needed. mounted close to the machine on the factory floor.

 In manufacturing plants  Factory automation fieldbuses are fast and deterministic.

where many instruments (Deterministic means the maximum worst-case time to obtain

need to be connected. data across the fieldbus is accurately predictable and is not
subject to chance.)

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When are Fieldbuses Used? Advantages of Fieldbus

 A major advantage of fieldbus is the capital expenditure

(CAPEX) savings associated with cable elimination; multiple
 When the advantages of Fieldbuses,
devices share wire-pairs in order to communicate over the bus
discussed on the next slide, are needed
network and savings are also available through speedier
 When the disadvantages of Fieldbuses, on the
commissioning.
slide after that, do not hinder use
 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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 Costs
Disadvantages of Fieldbus
• (CAPEX) Savings
 Disadvantages of fieldbus compared to the 4-20 mA analog • (OPEX) Savings Typical Modern Industrial System
signal standard: • Cost of Devices
 Fieldbus systems are complex, so more training needed • Investment Risks
 The price of fieldbus components is higher
– Engineering costs
 Fieldbus test devices are more complex – Equipment costs
 Device manufacturers have to offer different versions of – Installation costs
– Commissioning costs
devices due to different fieldbus standards. This can add to
– Maintenance costs
the cost of the devices and increases the difficultly of device – Operating costs
selection. – Inventory costs
– Retooling costs
 Standards may predominate or become obsolete, increasing
the investment risk.

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Location of the field bus in the plant hierarchy

Requires Supporting Technology?
File
Edit
SCADA level Operator 23 12 Engineering
4 2 2

• YES 33

• Fieldbus Components:
– Bus Terminal Plant bus
– EtherCAT
Programmable
– Fieldbus Box Plant Level Logic Controller
– Lightbus
– PC Fieldbus Cards
– Switches Field bus
– And more …
Field level

Sensor/
Actor
Bus
Sensor / direct I/O

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 The original idea: save wiring
Expectations marshalling tray
I/O bar capacity dumb devices
 Reduce cabling
 Increased modularity of plant (each object comes with its PLC
computer)
 Easy fault location and maintenance
 Simplify commissioning (mise en service, IBS =
Inbetriebssetzung)* (Rangierung,
tableau de brassage (armoire de triage)
 Simplify extension and retrofit

COM
 Large number of off-the-shelf standard products to build “Lego”- PLC
control systems field bus

 Possibility to sell one’s own developments (if based on a

but: the number of end-points remains the same !
standard)
energy must be supplied to smart devices

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Marshalling (Rangierschiene, Barre de rangement) Distributed peripherals

 Many field busses are just

extensions of the PLC’s Inputs
 The marshalling is the interface and Outputs, field devices are
between the PLC people and the data concentrators.
instrumentation people.  Devices are only visible to the
PLC that controls them
 The fieldbus replaces the
marshalling bar or rather moves it
piecewise to the process
(intelligent concentrator / wiring)

relays and fuses

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 Field busses classes
Geographical extension of industrial plants
1 km .. 1000 km Transmission & Distribution
Office
network Control and supervision of large distribution networks:
TCP IP • water - gas - oil - electricity - ...
Ethernet
1 km .. 5 km Power Generation
Plant Network Out of primary energy sources:
Ethernet, ControlNet
• waterfalls - coal - gas - oil - nuclear - solar - ...
50 m .. 3 km Industrial Plants
Fieldbus Manufacturing and transformation plants:
intelligent field devices • cement works - steel works - food silos - printing - paper
FF, PROFIBUS PA, LON
pulp processing - glass plants - harbors - ...
Sensor Busses 500m .. 2 km Building Automation
simple switches etc.
• energy - air conditioning - fire - intrusion - repair - ...
CAN, DeviceNet, SDS, ASI-bus, Interbus-S
1 m .. 1 km Manufacturing
flexible manufacturing cells - robots
The field bus depends on:
1 m .. 800 m Vehicles
its function in the hierarchy • locomotives - trains - streetcars - trolley buses - vans -
the distance it should cover buses - cars - airplanes - spacecraft - ...
the data density it should gather
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Fieldbus over a wide area: Water treatment plant

Fieldbus over a wide area: example wastewater
Japan Control Room source: Kaneka, Japan
treatment 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
 Pumps, gates, valves, motors, water level sensors, flow meters,
JB Segment 2 JB Segment 4
temperature sensors, gas meters (CH4), generators, … are spread Digital Input/Output

over an area of several km2 AI AI

S S S S S

 Some parts of the plant have explosive atmosphere. AI AI AI PID AI PID

AO AO
AI AI AI AI

 Wiring is traditionally 4..20 mA, resulting in long threads of cable

Numerous analog inputs (AI),
(several 100 km). low speed (37 kbit/s) segments merged to 1 Mbit/s links.
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 Fieldbus application: Building Automation
Fieldbus Application: locomotives and drives
Source: Echelon

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
low cost, low data rate (78 kbit/s), may use power lines (10 kbit/s)
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Fieldbus Application: automobile Application: Avionics (Airbus 380)

M onitoring redundantes
ECU und Bordnetz
Bordnetz ECU
Diagnose ECU 12V und 48V

c
Betätigungs-
einheit
Bremsen
ECU ECU
ECU
4

- 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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 Networking busses: Electricity Network Control: The ultimate sensor bus
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
power switch and
bus interface
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. requires integration of power electronics and communication at very low cost.
Problem: diversity of protocols, data format, semantics...
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Engineering a fieldbus: consider data density

(Example: Power Plants) Assessment
Acceleration limiter and prime mover: 1 kbit in 5 ms

Burner Control: 2 kbit in 10 ms • What is a field bus ?

per each 30 m of plant: 200 kbit/s

• Which of these qualities are required:
1 Gbit/s operation
Fast controllers require at least 16 Mbit/s over distances of 2 m Frequent reconfiguration
Plug and play
Data are transmitted from the periphery or from fast controllers to higher level, but slower links Bound transmission delay
to the control level through field busses over distances of 1-2 km. Video streaming
The control stations gather data at rates of about 200 kbit/s over distances of 30 m. • How does a field bus supports modularity ?
• What is the difference between a sensor bus and a process
The control room computers are interconnected by a bus of at least 10 Mbit/s,
over distances of several 100 m.
bus ?
• Which advantages are expected from a field bus ?
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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 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 Thank you for your attention!
• 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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