Engineering-Research-Paper-Summary

AUTONOMOUS ROOM AIR COOLER USING FUZZY LOGIC CONTROL SYSTEM

Aniketh Pattnaik(10);NITIE PGDIE42

This research paper describes the design and implementation of an autonomous room air cooler using fuzzy rule based control system. The rule base receives two crisp input values from temperature and humidity sensors, divides the universe of discourse into regions with each region containing two fuzzy variables, fires the rules, and gives the output singleton values corresponding to each output variable. Three defuzzifiers are used to control the actuators; cooler fan, water pump and room exhaust fan. The results obtained from the simulation were found correct according to the design model. This research work will increase the capability of fuzzy logic control systems in process automation with potential benefits. MATLAB-simulation is used to achieve the designed goal.

DESIGN BASIS

The control system design, development and implementation need the specification of plants, machines or processes to be controlled. A control system consists of controller and plant, and requires an actuator to interface the plant and controller. The behaviour and performance of a control system depend on the interaction of all the elements. The dynamical control systems design, modeling and simulation in local and distributed environment need to express the behaviour of quantitative control system of multi-input and multi-output variables control environment to establish the relation between actions and consequences of the control strategies.

Computational Intelligence (CI) is a field of intelligent information processing related with different branches of computer sciences and engineering. The fuzzy systems are one paradigm of CI. The contemporary technologies in the area of control and autonomous processing are benefited using fuzzy sets.

The fuzzy logic and fuzzy set theory deal with nonprobabilistic uncertainties issues. The fuzzy control system is based on the theory of fuzzy sets and fuzzy logic. Previously a large number of fuzzy inference systems and defuzzification techniques were reported. These systems/techniques with less computational overhead are useful to obtain crisp output. The crisp output values are based on linguistic rules applied in inference engine and defuzzification techniques.

The development of an air condition control system based on fuzzy logic with two inputs and one output using temperature and humidity sensors for feedback control, and three control elements for heating, cooling, and humidity, and formulated fuzzy rules for temperature and humidity has been achieved. To control the room temperature, the controller reads the room temperature after every sampling period.

PROPOSED MODEL

The basic structure of the proposed model of autonomous water room cooler consists of room air cooler with fuzzy logic control system. The room cooler mounted in a room has cooler fan, a water pump to spread water on its boundary walls of grass roots or wooden shreds. A room exhaust fan, humidity and temperature sensors used to monitor the environment of room are mounted in the room. The sensors with amplification and voltage adjustment unit are connected with the two fuzzifiers of the fuzzy logic control system. Three outputs of defuzzifiers: cooler fan speed control, water pump speed control and room exhaust fan speed control are connected through actuators.

CONCLUSION AND FUTURE WORK

Design model of autonomous room air cooler fuzzy logic processing control system provided the results effectively in agreement with the simulation results during the testing of various parts of the control system.

The algorithmic design approach makes the system efficient   and   absolutely   under   control.   This   work   builds up the control management without the complexity in a processing plant of room cooler to sustain the required cooling environment. The utility of the proposed system in such processing plants is being carried out and in future it will help to design the advanced control system for the various industrial applications in environment monitoring and management systems using state of the art FPGAs based Microelectronics Chips.

Industrial-Engineering-Research-Paper

APPLYING SCIENTIFIC MANAGEMENT PRINCIPLES TO

RAILROAD REPAIR SHOP

Aniketh Pattnaik(10)

Source:   paper  comes from  Carl  Graves, "Scientific  Management and the  Santa Fe  Shopmen of  Topeka,  Kansas, 1900-1915,"  Ph.D diss.,  Harvard  University,  1980

PAPER:

Students  of  labour  and  business  history have  studied  scientific  management  in  such  metal  factories  as  the Watertown  Arsenal,  but  no  one  has  analyzed  closely  this  work reorganization  in  the  railroad  industry.

This  paper  examines  how Taylorism  was  applied  on  the  Santa  Fe  between  1904  and  1918 and shall  try  to  answer  six  questions.

1. ·         What  was  the  nature  of  shop work  on  the  Santa  Fe  in  the  early  20th  century?
2. ·         Why was  scientific  management  installed?
3. ·         What  did  the  work  reorganization look  like?
4. ·         What  were  the  results?
5. ·         Why was  it  ended,  never revised,  or  widely  copies  by  other  railroads?
6. ·         Finally,  what  are some of  the  broader  implications  of  the  experiment?

WHAT  WAS  THE  NATURE  OF  RAILROAD  SHOP ( SANTA  FE)?

Railroad  shops  specialized  in  the  construction  and  repair  of locomotives  and  freight  and  passenger  cars.  Although  some lines built  part  of  their  locomotives  and  cars,  most  of  this  work  was performed  by  such  outside  firms  as  the  Baldwin  Locomotive  Works.

Therefore,  most  railroad  shop  work  was  the  repair  of  rolling stock  and  engines.  The  task  was  done  by  railroad  mechanics  -- machinists,  boilermakers,  blacksmiths,  carmen,  their  helpers  and apprentices,  as  well  as  common laborers.  In  the  first  two decades  of  the  20th  century,  railroad  shopmen were  more  numerous than  the  train  and enginemen  and  just  as  essential  to  their companies'  operations.  These  shopmen toiled  in  roundhouses  and in  small  and  large  shops  located  at  various  points  along  the line.  While  the  men  in  roundhouses  and  small  shops  did  minor 124 repairs,  the  mechanics in  larger  facilities  performed  such time- consuming tasks  as  locomotive  rebuilding,  as  well  as  some new construction.

The  Santa  Fe  Railway's  chief  repair  and  construction  facilities  were  located  in  Topeka,  Kansas.  These shops employed 1,600 men in  1900,  and  by  1918  the  total  was  approximately  3,000.  In addition,  medium-sized shops (employing between 250  and 750 men) were  located  in  such  places  as  San Bernardino,  California;  Ft. Madison,  Iowa;  and  Cleburne,  Texas.  Smaller  contingents  of shopmen were  found  in  roundhouses and adjacent  shop facilities  at nearly  every  division  point  along  the  system.  Except  for  the Topeka car  shop employees (who performed  piecework),  all  Santa  Fe shopmen were  paid  on  an  hourly  basis.

Shop work  on  the  Santa  Fe  was  varied,  although  at  times  it approached the  repetitive  nature  of  mass production.  Railway mechanics  disassembled  and  rebuilt  locomotives  and  repaired  or built  freight  and  passenger  cars.  In  the  larger  shops  this  work

was  done  by  an  increasingly  specialized  labour  force.  Occupational  titles  reflected  this  specialization:  there  were  (in Topeka)  blacksmiths,  hammersmiths,  and  springmakers;  there  were inside  and  outside  coach  carpenters,  car  painters,  air  brake repairers,  and  car  repairers;  there  were  erection  and  machine machinists,  as  well  as  various  types  of  helpers  and  labourers.

Sometimes  the  work  resembled  mass  production. Although  they  had  many common parts,  there  were  countless  variations  in  their structure, which  meant  that  the  work  was  more  varied  and  required  more  skill than  repetitive  assembly-line  mass production.  (During  the  age of  steam,  the  Santa  Fe  had  280  different  classes  of  locomotives.)

WHY  WAS  SCIENTIFIC  MANAGEMENT  INSTALLED?

By  introducing  scientific  management,  the  Santa  Fe  hoped  to check  rising  repair  costs,  increasing  union  influence  over  shop work,  and  general  deterioration  in  worker-management  relations.

The  company's concern  for  efficiency  and  cost  reduction  was shared  by  other corporations  in  this  period,  but  the  Santa  Fe's interest  was  especially  strong  because  of  its  recent  recovery from  bankruptcy  and  its  new leadership.  A  depression  had  forced the  already  troubled  Santa  Fe  into  receivership  in  December  1893.

Two years  later  the  railroad  emerged  from  receivership  with  a different  board  of  directors,  reduced  mileage  and  debt,  and  a  new president  --  Edward  Payson  Ripley.  The  new  chief  executive  and his  staff  achieved  dramatic  improvements  by –

• ·         trimming  unprofitable track age
• ·         instituting  such  cost-reduction  programs  as  conversion of  coal-fired  locomotives  to  less  costly  oil
• ·         ordering  new construction  only  after  careful  study
• ·         reinvesting  all  profits into  the  company

From 1898  to  1900,  the  company's surplus  rose, the  board  resumed payment  of  dividends,  and  rising  profits  generated  by  Ripley's  prudent  management and rising  national  prosperity  allowed  the  Santa  Fe  to  embark  on  a  modest  expansion  program.

Rising  repair  expenses,  however,  worried  corporate  executives.  Maintenance  costs,  especially  for  locomotives,  were rising  alarmingly  on  the  Santa  Fe  and  other  roads.  The  cost  of repair  per  locomotive  on  this  line  increased  from  $2,032  in  1897 to  $3,772  in  1904.  The  culprits  were  rising  wages  and  material costs,  as  well  as  declining  labor  efficiency.  Ripley  became convinced  that  trade  unions  were  detrimental  to  his  quest  for high  productivity  and  employee  loyalty.  The  Santa  Fe  had  earlier signed  agreements  with  such  shop  unions  as  the  machinists,  blacksmiths,  boilermakers,  and  carmen  in  1892,  due  mainly  to  the firm's  weak condition

Demands of  the  machinists'  union  brought  the  simmering union-management  conflict  to  a  crisis  in  1904.  This  labour organization  had  stepped  up  its  activity  on  the  Santa  Fe  in  late 1903  with  the  goal  of  organizing  enough men to  force  the  company to  grant  a  written  contract  and  improved  wages  for  the  entire system.  At  that  point  the  only  written  contract  for  machinists was on  the  Gulf  Lines  (in  Texas).  President  Ripley  and Vice- President  J.  W.  Kendrick  decided,  however,  that  the  rising  union influence  had  to  be  halted.  The  machinists'  union  taught  the  men "that  their  employer is  their  natural  enemy," said  Kendrick,  and counseled  workers  to  do  as  little  as  possible.  The  vice-president condemned the  proposed machinists'  union  agreement  because  it would  reduce  efficiency  and  output.  For  example,  one  part  of  the proposed  agreement  specified  that  such  tasks  as  running  lathes and  stripping  engines  be  done  only  by  machinists.  Kendrick argued  that  such  tasks  could  often  be  performed  by  lower-paid helpers  or  handymen.  The  company knew that  its  flat  rejection  of the  machinist  proposals  would  probably  trigger  a  strike.  But  the cost  of  such  a  conflict,  Ripley  wrote,  would  be  less  than  the additional  expense  of  one  year  under  the  proposed  union  rules.

A  more  detailed  version  of  his  objectives  appeared  in business  periodicals  in  1906.  These goals  were –

• ·         restoring harmonious  relations  between  employer  and  employee
• ·         freeing workers  from  the  tyranny  of  petty  officials,  on  the  one  hand,  and the  "individuality-destroying  union  domination,"  on  the  other
• ·         giving  the  line  more  reliable  and  efficient  workers
• ·         raising  automatically  the  pay  of  competent  employees  without interference  from  foremen
• ·         increasing  shop  capacity  without adding  new  equipment
• ·         improving  the  reliability  and  efficiency  of  the  work  performed
• ·         accomplishing  all  this while  reducing  company repair  costs

Thus,  this  cost-conscious  railroad  management  wanted  to lower  repair  costs  and  make  the  output  more  efficient.  An integral  part  of  these  tasks  was  the  elimination  of  union  influence  in  the  shops.  Emerson  promised  that  his  system  would meet  those  goals.

MODEL: WHAT  DID  THE  SYSTEM  LOOK  LIKE?

Although  an  admirer  of  Frederick  W.  Taylor,  the  father of  scientific  management,  Emerson  later  became  an  antagonist  and competitor.  Emerson's  concentration  on  ambiguous "principles  of efficiency,"  and  emphasis  on  the  labour  features  of  Taylor's system(especially  time  study  and  incentive  wages)  drew Taylor's wrath  for  being  dangerous  "short  cuts."  Nevertheless,  at  the time  of  his  appointment  to  the  Santa  Fe,  Emerson  considered himself  one  of  Taylor's  disciples.  In  major  respects,  Emerson's

changes  on  the  Santa  Fe  (his  most  important  corporate  assignment) reflected  Taylor's  influence,  as  will  be  documented later. (Among Emerson's  pre-1904  ventures  were  "systematizing  a  large new western  university,"  attempting  to  organize  US postal  routes in  The  Yukon,  and  managing  a  factory  of  100  employees.)

The  first  of  Emerson's  three  main  reforms  was  betterment  of methods  and  equipment.  His  goal  was  to  ensure  that  shop  conditions,  methods,  and  equipment  in  Topeka  would  promote  the  highest efficiency.  For  example,  he  studied  the  belting  which  transmitted  power  to  machinery.  Improvements in  belting  material  and  maintenance  lowered  failures  from  300  to  55  per  month  and  reduced monthly  belt  maintenance  from  $1,000  to  $275.  He  redesigned  many machine  tools  so  they  could  use  high-speed  steel,  which  allowed workers  to  perform  tasks  quicker.  In  addition,  he  designed dispatching  boards.  The  shop  machinery  board  had  separate  spaces

for  each  machine,  along  with  a  peg  for  requisition  slips.  By examining  the  board,  the  general  foreman  could  know  which  jobs were  to  be  rushed  (high-priority  work  had  a  special  color  tag) and  could  assign  future  jobs  for  each  machine.  Hence  the  foreman

could  prevent  tie-ups  and  idle  machines  and  men.  Finally  Emerson greatly  improved  blacksmith  shop  furnaces  so  that  men spent  less idle  time  waiting  for  the  fires  to  reach  operating  temperature.

The  second  element  of  Emerson's  innovations  was  centralizingin  Topeka  the  manufacture  of  tools  and  materials  for  the  entire Santa  Fe  system.  For  example,  the  Topeka  blacksmith  shop  began making  over  200  standardized  forgings  (of  bolts,  wrenches,  and  so on)  for  the  entire  system.  Previously the company had  done  this

work  at  several  points  along  the  line  and  occasionally  had  given the  work  to  outside  contractors.  Concentrating  their  manufacture allowed  the  railroad  to  produce  them  more  cheaply.

Probably  the  most  important  of  Emerson's  three  innovations was  the  individual  effort  reward  system,  also  called  the  bonus system  of  pay.  The  basis  for  this  wage  incentive  scheme  was  time study.  Using  stop  watches,  Emerson  and  his  assistants  studied

thousands  of  individual  operations  in  the  Topeka  shops.  The staff  then  decided  the  appropriate  time  (called  "standard  time") for  the  tasks  and  composed corresponding  bonus  schedules  of  pay. Every  worker  assigned  to  perform  an  operation  received  his  base hourly  pay  regardless  of  how slowly  he  toiled.  But  if  the employee  performed  his  assigned  task  in  the  "standard  time,"  he was said  to  be  "100  percent  efficient"  and  received  extra  money. If  he  performed  at  66  percent  efficiency  or  less,  he  received  no bonus;  80  percent  efficiency  led  to  a  3.25  percent  bonus,  90 percent  efficiency  drew  a  10  percent  bonus,  100  percent  efficiency  merited  a  20  percent  bonus,  and  so  on.

WHAT  WERE  THE  RESULTS?

As  Emerson's  scheme spread  from  Topeka  to  all  other  shops  on the  Santa  Fe  system,  outside  observers  and  company  officials  both noted  that  machines  and  men moved more  quickly  and  more  efficiently,  generating  a  substantial  monetary  savings.  The  work reorganization  was  not,  however,  without  its  problems.  There  was some  resistance  from  workers  even  after  unions  were  thrown  out, and  even  some  supervisory  personnel  were  opposed  to  the innovations.

These  improvements  were  reflected  in  higher  output  and decreased  unit  costs.  After  two  years  of  work  in  Topeka, Emerson's  system  increased  shop output  57  percent,  decreased  unit cost  of  production  36  percent,  even  while  the  average  pay  of  the

men rose  14.5  percent.  Per-unit  cost  of  maintenance  for  shop machinery  and  tools  fell  from  $10.31  (in  the  period  1903-04)  to $4.89  (in  the  period  1906-07)  on  the  Santa  Fe,  while  per-unit cost  on  another  Western  line  --  the  Southern  Pacific  --  actually

rose  slightly  during  the  same  time.  In  1906  railroad  Journals reported  that  the  Santa  Fe's  new system had restored  employer- employee  harmony,  improved  worker  efficiency  and  reliability,  and that  for  every  dollar  of  supervisory  and  bonus  pay,  the  company

had  saved  10.

CONCLUSION

Research  suggests  that  scientific  management  faced  two obstacles  in  railroad  shops,  one  from  the  workers  and  one  from the  managements.  Were  it  not  for  stiff  worker  resistance,  the 134 system might have spread farther.  Perhaps equally  as  important,

railroad  managements were  often  skeptical  of  major  reorganization of  their  shop operations,  for  understandable  and not-so-understandable reasons.

The bonus system ended on  the  Santa  Fe  in  1918,  not  because the  company decided  that  it  was no  longer  useful  but  because it was under  intense  pressure  from  shopmen, their  unions,  and (indirectly)  the  USRA.  Several  months  later  worker  pressure, abetted  by  USRA officials  eager  to  keep  the  railroads  running, led  to  the  demise  of  piecework  on  other  rail  lines.  Similarly  an earlier  Santa  Fe  attempt  to  expand  the  bonus  system  to  enginemen was halted  by  the  unbending resistance  of  the  Brotherhood  of Locomotive  engineers.  The  Santa  Fe's  long  and  costly  struggle  to defeat  the  shopcraft  unions  during  the  early  stages  of  scientific management was one reason  that  smaller  lines  such  as  the  Ann Arbor  Railroad  decided  against  the  introduction  of  incentive  pay.

In  the  absence  of  such  employee  resistance,  the  Santa  Fe  might have  expanded Emerson's  innovations  and retained  them much longer.

More  lines  might  have  followed  suit.  In  this  respect,  my results conflict  with  the  findings  of  Daniel  Nelson,  who has  argued  that scientific  management  experts  encountered  stiffer  opposition  from

managers  than  workers.

On  the  other  hand,  the  Santa  Fe  experience  shows  that management opposition  was  formidable,  within  the  company and  the rest  of  the  railroad  industry.  The  varied,  uncertain  nature  of railroad  repair  work  made scientific  management's application less  appropriate  than  for  mass  production.  In  certain  cases  it was  simply  easier  to  use  a  shortcut  version  --  piecework.  The source  of  some management  opposition,  however,  was  of  less laudible  origin.  Many railroads  had  "self  satisfied  attitudes" and  were  not  open  to  change.  Often  railroads  were  jealous  of each  other  and,  therefore,  did  not  wish  to  adopt  a  method  employed  by  another.  Considerable  skepticism  to  change  was generated  by  resistance  to  outside  experts.

 Emerson  was  indeed an  outsider.  His  chances  for  advising  other  lines  was  probably reduced  by  his  testimony  during  the  1910  rate  hearings.  These hearings  generated  considerable  debate  within  the  railroad industry  about  efficiency,  much of  it  defensive  in  natureThe  decline  of  the  American  railroad  industry  can  be  traced to  such  factors  as  increased  competition  from  more  efficient modes of  transportation,  and  the  lopsided  policies  of  a  federal government  which  heaped  subsidies  on  alternate  modes while  it denied  railroads  needed  rate  hikes  in  the  pre-World  War  I  era  and later  (during  the  Kennedy Administration)  denied  them  the  opportunity  to  lower  rates.  The  evidence  of  this  paper  might  lead one  to  add  another  factor  for  railroad  woes  --  managements' stubborn  refusal  to  recognize  the  potential  of  Taylorism.  However,  that  criticism  of  railroad  corporate  management must  be  tempered  by  recognition  of  two  other  factors  --  the recalcitrance  of  railroad  labor  toward  such  innovations,  and  the legitimate  doubts  which  companies  had  about  the  applicability  of scientific  management  toward  their  repair  establishments.

Design-and-Production-Process-Project

DESIGN AND PRODUCTION PROCESS PROJECT

Industrial Engineering Assignment

By : Aniketh Pattnaik(roll 10) & Gaurav Pandey (roll 33)

Topic:    SMART SENSORS TECHNOLOGY IN INDUSTRY

Introduction

Transducers are sensors and actuators in order that a computer system can interact with the physical environment. In 1982, Ko and Fung introduced the term “intelligent transducer” . An intelligent or smart transducer is the integration of an analog or digital sensor or actuator element, a processing unit, and a communication interface. In case of a sensor, the smart transducer  transforms the raw sensor signal to a standardized digital representation, checks and calibrates the signal, and transmits this digital signal to its users via a standardized communication protocol. In case of an actuator, the smart transducer accepts standardized commands and transforms these into control signals for the actuator. In many cases, the smart transducer is able to locally verify the control action and provide a feedback at the transducer interface. With the advent of modern microcontrollers it became possible to built low-cost smart transducers by using commercial-off-the-shelf microcontrollers that provide a standard communication interface, such as a UART (Universal Asynchronous Receiver/Transmitter). Thus, the usage of smart transducers can become a cost decreasing factor for building embedded control systems. The objective of this paper is to give a brief overview in principles, communications, and configuration aspects for smart transducers. The remainder of the paper is structured as follows. Discusses the basic principles of smart transducers. It gives an overview on existing communication interfaces for smart transducers. Section describes various approaches for configuration support of smart transducer networks. The paper is concluded in section Smart Transducer Principles

Two-Level Design Approach

The smart transducer technology introduces a two-level design approach that helps to reduce the overall complexity of a system by separating transducer-specific implementation issues from  interaction issues between different smart transducers.

The transducer manufacturer will deal with instrumenting the local transducer and signal conditioning in order to export the transducer’s service in a standardized way. Transducer manufacturers are thus liberated from interoperability issues between sensors, naming inconsistencies and the network topology of the total system. The user of a smart transducer’s service can access its data via an abstract interface that hides the internal complexity of the transducer hardware and software. Thus, smart transducer applications can be built in a less complex way.

Interface Design

The most critical factor for a smart transducer design is the construction of the interfaces to smart transducers. We distinguish the smart transducer interface and the transducer communication  interface.

The smart transducer interface is an abstract interface that gives access to the transducer features, such as measurement value or set value, respectively, but also vendor ID numbers, diagnostic information and setup parameters. Usually, a smart transducer interface provides different types of service, such as configuration, remote diagnosis, and real-time measurement. In order to keep a clean separation of functionalities and achieve a better understandability of a smart transducer interface, Kopetz proposes the introduction of distinct interfaces for functional different services

In detail the following three interface types can be distinguished:

Real-Time Service (RS) interface: 

This interface provides the timely real-time services to the smart transducer during the operation of the system. Diagnostic and Management (DM) interface: This interface opens a communication channel to the internals of a smart transducer. It is used to set parameters and to retrieve information about the internals of a component, e. g., for the purpose of fault diagnosis.

The DM interface is available during system operation without disturbing the real-time service. Normally, the DM interface is not time-critical. Configuration and Planning (CP) interface: This interface is necessary to access configuration properties of a node. During the integration phase this interface is used to generate the “glue” between the autonomous smart transducers. The CP interface is not time-critical.

The transducer communication interface defines the communication among the transducers in the network. The idea to connect multiple transducers to a single communication bus has its roots in the industrial fieldbus networks that dateback to the early 1970s. An early example for a transducer communication interface is the 4-20 mA current loop, an analog signal standard for the point-to-point connection of analogue devices. The transducer communication interface handles aspects such as the communication baud rate, data encoding, flow control, and message scheduling. The difference between these two interfaces becomes clear, when they are aligned to the 7-layer of the International Standard Organizations Open System Interconnect (ISO/OSI) model. While the issues on the smart transducer interface relate to the application layer (layer 7) of the OSI reference model, the network communication relates to the layers below 7, especially the physical layer (layer 1) and the data link layer (layer 2). The intermediate layers 3-6 are usually not defined for fieldbus systems. All interfaces have to be well-defined in the value and in the time domain in order to enable desirable properties such as interoperability, i. e., the ability of two or more devices, independent of the manufacturer, to work together in one or more distributed applications , and composability, i. e., if each subsystem implements well-defined interfaces in the temporal and value domain, it can be guaranteed a priori that the subsystem provides its specified service also in the composite system.

The IEC worked out the IEC 61158 standard. It is based on the following existing fieldbus systems:

Foundation Fieldbus: A functional superset of WorldFIP. The IEC 61158 standard defines also a Foundation Fieldbus High Speed Ethernet type.

ControlNet: ControlNet has been primarily designed to meet the requirements of high speed real-time applications for automation and control. ControlNet features the Control and Information Protocol that provides real-time and peer-to-peer messaging.

Ethernet/IP: EtherNet/IP is an open network based on the IEEE 802.3 Physical and Data Link standard, the Ethernet TCP/IP protocol suite and the Control and Information Protocol.

Profibus: Profibus is a distributed control system for process automation. Profibus is one of the most popular fieldbus protocols in this area. In 2001 it claimed 53.6% of the revenue created in the fieldbus sector in Europe.

SwiftNet: SwiftNet is a high performance fieldbus that was created as a synchronous, high speed flight data bus for Boeing Commercial Airplane. SwiftNet provides high data efficiency and clock synchronization among the communicating nodes.

WorldFIP: WorldFIP is designed with a strictly real-time capable control 

scheme based on a producer-consumer communication model. WorldFIP was published as a French standard in the late 80s. No significant change has taken place since the first French standard.

Interbus: Interbus is a digital, serial communication system for communication between control systems and transducer devices. Interbus is optimized, but not limited to factory automation applications.

What is HART

The majority of smart field devices installed worldwide today are HART-enabled. But some new in the automation field may need a refresher on this powerful technology. HART (Highway Addressable Remote Transducer) Protocol is the global standard for sending and receiving digital information across analog wires between smart devices and control or monitoring system. HART is a bi-directional communication protocol that provides data access between intelligent field instruments and host systems.

A DIGITAL UPGRADE FOR EXISTING PLANTS
HART technology offers a reliable, long-term solution for plant operators who seek the benefits of intelligent devices with digital communication – that is included in the majority of the devices being installed .Because most automation networks in operation today are based on traditional 4-20mA analog wiring, HART technology serves a critical role because the digital information is simultaneously communicated with the 4-20mA signal. Without it, there would be no digital communication.

There are several reasons to have a host communicate with smart devices. These include:

• Device Configuration or re-configuration
• Device Diagnostics
• Device Troubleshooting
• Reading the additional measurement values provided by the device
• Device Health and Status

How HART Works

“HART” is an acronym for Highway Addressable Remote Transducer. The HART Protocol makes use of the Bell 202 Frequency Shift Keying (FSK) standard to superimpose digital communication signals at a low level on top of the 4-20mA.

   

Figure 1. Frequency Shift Keying (FSK)

         

This enables two-way field communication to take place and makes it possible for additional information beyond just the normal process variable to be communicated to/from a smart field instrument. The HART Protocol communicates at 1200 bps without interrupting the 4-20mA signal and allows a host application (master) to get two or more digital updates per second from a smart field device. As the digital FSK signal is phase continuous, there is no interference with the 4-20mA signal.

Figure  2. Two Communication Channels

HART technology is a master/slave protocol, which means that a smart field (slave) device only speaks when spoken to by a master. The HART Protocol can be used in various modes such as point-to-point or multidrop for communicating information to/from smart field instruments and central control or monitoring systems.

HART Communication occurs between two HART-enabled devices, typically a smart field device and a control or monitoring system. Communication occurs using standard instrumentation grade wire and using standard wiring and termination practices.
                             
    

The HART Protocol provides for up to two masters (primary and secondary). This allows secondary masters such as handheld communicators to be used without interfering with communications to/from the primary master, i.e. control/monitoring system.

Figure 3. Primary and Secondary Masters

The HART Protocol permits all digital communication with field devices in either point-to-point or multidrop network configurations:

Figure 4. Point-to-Point Configuration

Multidrop Configuration

There is also an optional "burst" communication mode where a single slave device can continuously broadcast a standard HART reply message. Higher update rates are possible with this optional burst communication mode and use is normally restricted to point-to-point configuration.

Benefits of Using HART Communication

• Leverage the capabilities of a full set of intelligent device data for operational improvements.
• Gain early warnings to variances in device, product or process performance.
• Speed the troubleshooting time between the identification and resolution of problems.
• Continuously validate the integrity of loops and control/automation system strategies.
• Increase asset productivity and system availability.

Increase Plant Availability

• Integrate devices and systems for detection of previously undetectable problems.
• Detect device and/or process connection problems real time.
• Minimize the impact of deviations by gaining new, early warnings.
• Avoid the high cost of unscheduled shutdowns or process disruptions.

Reduce Maintenance Costs

• Quickly verify and validate control loop and device configuration.
• Use remote diagnostics to reduce unnecessary field checks.
• Capture performance trend data for predictive maintenance diagnostics.
• Reduce spares inventory and device management costs.

Improve regulatory compliance

• Enable automated record keeping of compliance data.
• Facilitates automated safety shutdown testing.
• Raise SIL/safety integrity level with advanced diagnostics.
• Take advantage of intelligent multivariable devices for more thorough, accurate reporting.

The standard features of HART technology range from simple compatibility with existing 4-20mA analog networks to a broad product selection:

• Compatibility with standard 4-20mA wiring
• Simultaneous transmission of digital data
• Simplicity through intuitive menu-driven interfaces
• Risk reduction through a highly accurate and robust protocol
• Ease of implementation for maximum “up-front” cost effectiveness
• Broad product selection, with compatible devices and software applications from most process automation providers
• Platform independence for full interoperability in multi-vendor environments

HART Specifications

. The current version of the HART Protocol is revision 7.3. The "7" denotes the major revision level and the "3" denotes the minor revision level.

The HART Protocol implements layers 1,2, 3, 4 and 7 of the Open System Interconnection (OSI) 7-layer protocol model:

The HART Physical Layer is based on the Bell 202 standard, using frequency shift keying (FSK) to communicate at 1200 bps. The signal frequencies representing bit values of 0 and 1 are 2200 and 1200Hz respectively. This signal is superimposed at a low level on the 4-to-20mA analog measurement signal without causing any interference with the analog signal.

The HART Data Link Layer defines a master-slave protocol - in normal use, a field device only replies when it is spoken to. There can be two masters, for example, a control system as a primary master and a handheld HART communicator as a secondary master. Timing rules define when each master may initiate a communication transaction. Up to 15 or more slave devices can be connected to a single multidrop cable pair.

The Network Layer provides routing, end-to-end security, and transport services. It manages "sessions" for end-to-end communication with correspondent devices.

The Transport Layer: The Data-Link Layer ensures communications are successfully propagated from one device to another. The Transport Layer can be used to ensure end-end communication is successful.

The Application Layer defines the commands, responses, data types and status reporting supported by the Protocol. In the Application Layer, the public commands of the protocol are divided into four major groups:

In order to control a dynamic variable in a process, there must be information about the variable itself. This information is obtained from a measurement of the variable. A measurement system is any set of interconnected parts that include one or more measurement devices. Measurement devices such as sensors, or primary elements, measure the variable.1. Me
asurement Devices

Measurement devices

Measurement devices perform a complete measuring function, from initial detection to final indication. Two important aspects of a measurement system are the sensor and the transmitter. A third is the transducer.

• Sensor: Primary sensing element
• Transducer: Changes one instrument signal value to another instrument signal value
• Transmitter: Contains the transducer and produces an amplified, standardized instrument signal

Signal types

In most existing plants pneumatic and electronic signals are predominant. Pneumatic signals are normally 3-15 pounds per square inch (psi), and electronic signals are normally 4-20 milliamps (mA). Optical signals are also used with fiber optic systems or when a direct line of sight exists.

Radio and hydraulic signals are also used, though they are not as common because of inherent problems such as radio signal interference and leakage of hydraulic systems. However, radio signals commonly are used when sensors and transmitters are great distances (on pipelines, for example) from control centres.

A major difference between electronic and pneumatic transmission systems is the time required for signal transmission. In an electronic system there are no moving parts, only the state of the signal changes. This change occurs with virtually no time lost.

 

As we stated previously, mechanical movement takes place whenever any pneumatic process signal changes. When devices move mechanically, time is lost. In addition, pneumatic systems, because they contain moving parts, are higher maintenance and subject to vibration, as well as rotational or gravitational mounting problems. However, pneumatic systems are still in place in many plants because they are safer than electrical systems in certain environments containing potentially explosive atmospheres.

A transmitter's gain, that is the ratio of the output of the transmitter to the input signal, is constant regardless of its output. In other words, an electronic transmitter's gain will remain constant whether it's output is 0% of span (4 mA) or 100% of span (20 mA) or any other point between those extremes.

So far, the discussion has centred around electronic and pneumatic transmitters. The input and output of both of these types of transmitters is an analog signal -- either a mA current or air pressure, both of which are continuously variable. There is another kind of transmitter -- the "smart" transmitter.

Smart Transmitter Components and Function

They can convert analog signals to digital signals (A/D), making communication swift and easy and can even send both analog and digital signals at the same time as denoted by D/A.

A smart transmitter has a number of other capabilities as well. For instance, inputs can be varied, as denoted by A/D. If a temperature transmitter is a smart transmitter, it will accept millivolt signals from thermocouples and resistance signals from resistance temperature devices (RTDs), and thermistors.

Components of the smart transmitter are illustrated in the lower figure. The transmitter is built into a housing about the size of a softball as seen on the lower left. The controller takes the output signal from the transmitter and sends it back to the final control element. The communicator is shown on the right.

The communicator is a hand-held interface device that allows digital "instructions" to be delivered to the smart transmitters. Testing, configuring, and supply or acquiring data are all accomplished through the communicator. The communicator has a display that lets the technician see the input or output information. The communicator can be connected directly to the smart transmitter, or in parallel anywhere on the loop.

Smart transmitters also have the following features:

• Configuration
• Re-ranging
• Characteristics
• Signal conditioning
• Self-diagnosis

Configuration

Smart transmitters can be configured to meet the demands of the process in which they are used. For example, the same transmitter can be set up to read almost any range or type of thermocouple, RTD, or thermistor. Because of this, they reduce the need for a large number of specific replacement devices.

Re-ranging

The range that the smart transmitter functions under can be easily changed from a remote location, for example by the technician in a control room. The technician or the operator has access to any smart device in the loop and does not even have to be at the transmitter to perform the change. The operator does need to use a communicator, however. A communicator allows the operator to interface with the smart transmitter. The communicator could be a PC, a programmable logic controller (PLC), or a hand-held device. The type of communicator depends on the manufacturer.

Re-ranging is simple with the smart transmitter. For instance, using a communicator, the operator can change from a 100 ohm RTD to a type-J thermocouple just by reprogramming the transmitter. The transmitter responds immediately and changes from measuring resistance to measuring millivoltage.

There is a wide range of inputs that a smart transmitter will accept. For instance, with pressure units, the operator can determine ahead of time whether to use inches of water, inches of mercury, psi, bars, millibars, Pascal’s, or kilopascals.

Characteristics

Another characteristic of a smart transmitter is its ability to act as a stand-alone transmitter. In such a capacity, it sends the output signal to a distributed control system (DCS) or a PLC.

Signal conditioning

Smart transmitters can also perform signal conditioning, scanning the average signal and eliminating any "noise" spikes. Signals can also be delayed (dampened) so that the response does not fluctuate. This is especially useful with a rapidly changing process.

Self-diagnosis

Finally, a smart transmitter can diagnose itself and report on any problems in the process. For example, it can report on a circuit board which is not working properly.

Summary

There are distinct advantages in using a smart transmitter. The most important include ease of installation and communication, self-diagnosis, improved and digital reliability. Smart transmitters are also less subject to effects of temperature and humidity than analog devices. And although vibration can still affect them, the effects are far less than with analog devices. Smart transmitters also provide increased accuracy. And because can replace several different types of devices, using them allows for inventory reduction.