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Lecture 1 the lecture

Jul 14, 2015





Overview of lecture 1At the endof thislectureyou should be able toExplain the definition of control system.Explain the basic component of control systems.Explain the Closed-loop and Open-loop control system.Give an example of the control system.

What is control?Fig.1 Control the water levelWhat is controlhttp://www.merriam-webster.com1aarchaic:to check, test, or verify by evidence or experimentsb:to incorporate suitablecontrolsin2a:to exercise restraining or directing influence over:regulateb:to have power over:rulec:to reduce the incidence or severity of especially to innocuous levelsWhat is controlA term that describes the process of forcing a system to behave in a desired way in order to achieve certain objective(s) or goal(s).

What is system?http://www.merriam-webster.com1 :a regularly interacting or interdependent group of items forming a unified whole: asa(1):a group of interacting bodies under the influence of related forces(2):an assemblage of substances that is in or tends to equilibriumb(1):a group of body organs that together perform one or more vital functions(2):the body considered as a functional unitc:a group of related natural objects or forcesd:a group of devices or artificial objects or an organization forming a network especially for distributing something or serving a common purposee:a major division of rocks usually larger than a series and including all formed during a period or eraf:a form of social, economic, or political organization or practiceWhat is systemhttp://www.merriam-webster.com2 :an organized set of doctrines, ideas, or principles usually intended to explain the arrangement or working of asystematicwhole3 a:an organized or established procedureb:a manner of classifying, symbolizing, or schematizing4 :harmonious arrangement or pattern:order5 :an organized society or social situation regarded as stultifying or oppressive:establishment2 usually used withtheWhat is system*a segment of environment that is under consideration to control.* Can be a plant or a processWhat is Control SystemControl System is an interconnection of components forming a system configuration that will provide a desired system response.

Typically, a system process has one or more inputs and outputs, which can be represented by a block digram as shown below.PROCESSINPUTOUTPUTFig.2 Typical representation of a processBASIC COMPONENTSControlled variableQuantity or condition that is measured and controlled.Manipulated variableQuantity or condition that is varied by the controller so as to affect the value of the controlled variable Plant To perform particular operation. It is the physical object to be controlled (mechanical devices, heating furnace, etc.)Process Is any operation to be controlled. Processes can be chemical, economic, etcSystemIs a combination of components that act together and perform certain objectiveDisturbanceIs a signal that tends to adversely affect the value of the output ofa system. May internal or externalFeedback controlRefers to an operation that, in the presence of disturbances, tendsto reduce the difference between the output of a system and some reference input.Control System

Fig.3 Example of control systemControl EngineeringEngineeringdiscipline that concerned with understanding and controlling the systems to provide useful economics products.Applies control theory to design the systems with desired behaviors.

Control Engineering is not restricted to one field of engineering but equally applicable to different branches of engineering such as aeronautical, mechanical, chemical, civil, computer, electrical etc.

OPEN-LOOP & CLOSED-LOOPControl system can be categorized into 2 classses:Open-loop systemClosed-loop system

OPEN-LOOP vs CLOSED-LOOP Open-loop System: utilizes a controller or actuating device to obtain a desired response directly without using feedback

Fig.4 Open loop control systemOPEN-LOOP vs CLOSED-LOOP Closed-loop System:In contrast to an open-loop control system, a closed-loop utilizes the additional measure of the actual output to compare the actual output with the desired output (reference or command). This additional measure of the output is called thefeedback.

Fig.5 Close loop control systemExample of Control System

Fig.6 Example of control system Room Temperature controlAn open loop control systemRoom temperature control. Control Signal / Input : the inlet vent temperatureThe output (controlled variable) : The room air temperature.The actuator : comprises of the furnace and apre-programmedon-off switch that triggers the furnace, which in turn activates the inlet vent temperature. A disturbance : The ambient temperature

Fig.7 Open loop system of Room Temperature controlThe close loop control systemRoom temperature control. modified by incorporating the measure of the output, i.e. the room air temperature. The controller is thethermostatthat takes into account a reference signalThe output feedback in order to set the switch position.

Fig.7 Close loop control of Room Temperature controlThe close loop control systemRoom temperature control. Ideally, the thermostat should trigger the switch as soon as the error is negative and switch off when the room air has reached/exceeded the reference temperature. The features of this scheme areif room temperature A and we have positive feedback If AB is positive If AB is positive then (1 + AB) > 1 In this situation G < A and we have negative feedback If AB is positive and AB >>1 G = A / (1+AB) =A /AB = 1/B- gain is independent of the gain of the forward path A29

QUIZ 1In group of 5(Maximum members, less is better ),LetDecide one control system and define the basic component of the control system. Try to develop the block diagram for open loop and close loop of the system.