INTRODUCTION TO CONTROLINTRODUCTION A system is combination of components that act together and perform certain task. A control system is a group of components that maintains a desire result by regulating energy input.2SPLevelINTRODUCTION3AUTOMATION Automation / automatic control: A control system which works with minimalor no human involvement. Examples: Automatic milk filling machine. Automatic car gear shift. Automatic car speed cruise control. Automated palleting system. Advantages.4TYPES OF CONTROLTypes of controlApplicationsProcess ControlServo MechanismSequential ControlNumerical ControlTypes of signalPneumaticsElectronics5TYPES OF CONTROL Pneumatics signal: 3psi 15psi Electronics signal: 4mA 20mA6Something to think about: Why starting from 4mA and 3psi? Why mA but not mV?BASIC TERMINOLOGY Control Variable (cv) Set Point (sp) Measured Variable (cm) Error (E) Manipulating Variable (mv) Disturbances (z) Load7BASIC TERMINOLOGY Conditions (disturbances) in a process that are capable of causing load change. Examples.8BASIC TERMINOLOGY Examples.9RTD sensorCold air flow inRoom temperature = 28oC.Desired value of the room temperature = 25oC.Ambient temperature = 35oC.CHARACTERISTICS OF CONTROL SYSTEM Stable system. System is stable when the Controlled Variable reaches steady state after some time. Unstable system. System is unstable when the Controlled Variable starts oscillating and the oscillation stays.10CHARACTERISTICS OF CONTROL SYSTEM Underdamped, Criticallydamped, Overdamped.11CHARACTERISTICS OF CONTROL SYSTEM Unstable constant amplitude. Unstable increasing amplitude.12TimeC.Vd.unstableconstantamplitudeTimeC.Ve.unstableincreasingamplitudeCHARACTERISTICS OF CONTROL SYSTEM Time response / Settling time. Time delay / Dead time. % Overshoot. Time constant. Offset.13REPRESENTING A CONTROL SYSTEM Electronics Level Control. Pneumatics Level Control. Electronics Flow Control. Pneumatics Flow Control14CONTROL BLOCK DIAGRAMOPEN LOOP & CLOSED LOOP CONTROL SYSTEMS15Open Loop Open Loop systems are control systems in which the output is not measured and not feedback into the controller.Closed Loop Closed Loop systems are control systems in which the output is measured and feedback into the controller.OPEN LOOP & CLOSED LOOP CONTROL SYSTEMS16Open Loop ExamplesClosed Loop ExamplesFan, toaster, hair dryer AC, Oven, Household hot water system, Household water tank.OPEN LOOP & CLOSED LOOP CONTROL SYSTEMS17Open Loop Advantages Less expensive than closed loop control because not necessary to measure actual result. Controller is much simpler because corrective action based on error is not required. Easier to build since stability is not a major problem.Closed Loop Advantages The system response relatively insensitive to external disturbances and internal variations in system parameters. It is possible to use relatively inaccurate and inexpensive components to obtain an accurate control.OPEN LOOP & CLOSED LOOP CONTROL SYSTEMS18Open Loop Disadvantages Errors caused by unexpected disturbances are not corrected. Human operator must slowly correct changing disturbances by manual adjustment.Closed Loop Disadvantages Overcorrect of errors will cause oscillations and stability problem.TYPES OF OPEN LOOP CONTROL SYSTEMSTypes of OPEN LOOP controlDirect forward open loop controlHolding element open loop controlTime plane open loop controlPosition plane open loop controlSequential open loop control19ELEMENTS OF CLOSED LOOP CONTROL20ComparingCorrective actionProcessMeasurementELEMENTS OF CLOSED LOOP CONTROL Sensor Transmitter Controller Transducer Final Control Element21SPAUXILIARIES OF CONTROL SYSTEM Indicator / Gauge Recorder Alarm Trip Interlock22FEEDFORWARD CONTROL Is based on measuring disturbances, anticipating error, and take corrective actions to cancel the error.23FEEDFORWARD CONTROL24FEEDFORWARD CONTROL Advantages: Fast errors correction. Can predict errors. Disadvantages: 1) 2) 3) 4) Block diagrams25FEEDFORWARD CONTROL Feedforward control is open loop control. Feedforward control minimized the transient error caused by measurable disturbances. Feedforward control cannot cancel the effects of immeasurable disturbances. Feedback control provides corrections for immeasurable disturbances. So, feedforward is normally combined with feedback loop.26THANK YOU27