IntroductionSystem An interconnection of elements and devices for a desired purpose.Control System An interconnection of components forming a system configuration that will provide a desired response.Process The device, plant, or system under control.The input and output relationship represents the cause-and-effect relationship of the process.Thecontrolsystemisthatmeansbywhichanyquantityofinterestina machine,mechanismorotherequipmentismaintainedoralteredin accordance with a desired manner. Consider, for example, the driving system of an automobile. Speed of the automobileisafunctionofthepositionofitsaccelerator.Thedesired speedcanbemaintained(oradesiredchangeinspeedcanbe achieved)bycontrollingpressureontheacceleratorpedal.This automobiledrivingsystem(accelerator,carburettorandenginevehicle) constitutes a control system. Control SystemIntroductionMultivariable Control ystemOpen-Loop Control Systems utili!e a controller or control actuator to obtain the desired response.Closed-Loop Control Systems utili!es feedbac" to compare the actual output to the desired output response.Open-loop !An open-loop controller, also called a non-feedback controller, is a type of controller which computes its input into a system using only the current state and its model of the system. Diferences!The terms open-loop control and closed-loop control are often not clearly distinguished. Therefore, the diference betweenopen-loopcontrolandclosed-loopcontrolis demonstratedinthefollowingexampleofaroom heatingsystem.Inthecaseofopen-loopcontrolofthe roomtemperatureaccordingtoFiguretheoutdoor temperature will be measured by a temperature sensor and fed into a control de!ice. Open-loopOpen-loop!Acharacteristicoftheopen-loopcontrolleristhatit doesnotusefeedbacktodetermineifitsoutputhas achie!ed the desired goal of the input. This means that thesystemdoesnotobser!etheoutputofthe processesthatitiscontrolling."onse#uently,atrue open-loopsystemcannotengageinmachinelearning and also cannot correct any errors that it could make. It alsomaynotcompensatefordisturbancesinthe system. The characteristics of feedforward control It has the characteristic of forward control So, if we use this strategy correctly, the controlled variable will not deviate set point The advantage of feedforward control Fig 1-5 Feedforward control TT T team Ti(t) #eedforward controller SP T(t) Condensation retun The characteristics of feedforward control !eedforward control cannot compensate for all disturbances that enter the process The disadvantage of feedforward control The characteristics of feedforward control Fig 1-5 Feedforward controlIn this example, The feedforward control system can compensate only one of disturbances. If any of the other disturbances enter the process, this strategy will not compensate for it, and the result will be a permanent deviation from set point of the controlled variable. The disadvantage of feedforward control T team Ti(t)f(t) #eedforward controller SP TT T(t) Condensation retun Closed-loop! "loseloopcontrolsystemsusetheopen loopsystems$asforwardpath%and feedbackfromtheoutputtodecidethe inputle!eltotheopenloopsystem.And because the input is decided based on how muchawaytheoutputisfromthedesired le!el,thenonidealitiesinforwardpathdo notdegradethesystemperformance.The accuracy of the output thus depends on the feedbackpath,whichingeneralcanbe made !ery accurate. Closed-loop!In the case of closed-loop control of the room temperature as shown in Figurethe room temperature is measured and compared with the set-point !alue. If the room temperature de!iates from the gi!en set-point !alue, a controller $"% alters the heat &ow. All changes of the room temperature, e.g. caused by opening the window or by solar radiation, are detected by the controller and remo!ed. Closed-loopThe order of e!ents to organise a closed-loop control is characterised by the following steps' (easurement of the controlled !ariable"alculation of the control error $comparison of the controlled !ariable with the set-point !alue% )rocessing of the control error such that by changing the manipulated !ariable the control error is reduced or remo!ed The bloc" diagrams of feedbac" control system!ig #-$ %loc" diagrams of closed-loop control systems Controller !inal control element Process or plant SP Output Or Controlled variable Sensor& Transmitter - Summing 'unction (isturbance )(isturbance # The advantage of feedbac control1.! "#$T%#& 'T%(T)*I)'"ompensate for all disturbances The result of any disturbance entering the process is to mae the controlled variable deviate from the ')T +#I$T. #nce the controlled variable deviates from the set point, the controller changes its output to return the controlled variable to ')T +#I$T,its desired value-.The feedbac control loop does not now, nor does it care, which disturbance enters the process. It only tries to maintain the controlled variable at set point, and in this way compensates for all disturbances. The feedbac controller wors with minimum nowledge of the process. (ctually, the only information it needs is in which direction to move, and how much to move is usually ad.usted by trial and error. The characteristics of feedbac" control The disadvantage of feedbac control1.! "#$T%#& 'T%(T)*I)'"an compensate for a disturbance only (FT)% the controlled variable has deviated from the set point because of the disturbance. "an not give the controlled variable a timely control The characteristics of feedbac" control T team Ti(t) $rocess fluid T(t) TT TC SP Condensate return ensor #inal control element Transmitter Controller Some e*amples+,ashing machineOven-icrowave oven.ir conditioner!eedforward control system!eedbac" control system/ow to choose a proper control system00 +!eedbac" control system1eview+!eedforward control system234 Choose a proper control system"omparing open-loop control with closed-loop control the following diferences are seen' Proper Control SystemCan get the output that a process needLow cost !eedforward Control System!eedbac" Control SystemCan not compensate all disturbancesCan compensate all disturbancesimple structure %ow costComple& structure'igh cost ContrastTrade-off+ Simplicity and low cost Comple*ity and higher cost ChoiceAn open-loopsystemA closed-loopsystemPremise+ 5nsure the re6uirement of industrial productionClosed-loop control !shows a closed-loop action $closed control loop%* !can counteract against disturbances $negati!e feedback%* ! can become unstable, i.e.the controlled !ariable does not fade away, but grows $theoretically% to an in+nite !alue. Open-loop control !shows an open-loop action $controlled chain%* !can only counteract against disturbances, for which it has been designed* other disturbances cannot be remo!ed* ! cannot become unstable - as long as the controlled ob,ect is stable. -ummarising these properties we can de+ne' -ystems in which the output #uantity has no efect upon the process input #uantity are called open-loop control systems. -ystems in which the output has an efect upon the process input #uantity in such a manner as to maintain the desired output !alue are called closed-loop control systems. /istory(att)s #lyball *overnor+,-th century.*reece +/C. #loat regulator mechanism'olland +,0th Century. Temperature regulator/istory(ater-level float regulator/istory/istory#7th Century 1ames (att)s centrifugal governor for the speed control of a steam engine.#8)9s Minors"y wor"ed on automatic controllers for steering ships.#839s 2y3uist developed a method for analy!ing the stability of controlled systems#8$9s #re3uency response methods made it possible to design linear closed-loop control systems#8:9s 4oot-locus method due to 5vans was fully developed#8;9s tate space methods, optimal control, adaptive control and#879s%earning controls are begun to investigated and developed.Present and on-going research fields. 4ecent application of modern control theory includes such non-engineering systems such as biological, biomedical, economic and socio-economic systems66666666666666666666666666666666666$a% Automobile steering control system.$b% The dri!er uses the diference between the actual and the desired direction of tra!el to generate a controlled ad,ustment of the steering wheel.$c% Typical direction-of-tra!el response.5*amples of -odern Control Systems5*amples of -odern Control Systems5*amples of -odern Control Systems