Ch 3_introduction to Control System J5800

8/3/2019 Ch 3_introduction to Control System J5800

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T H I S I S A N I N T R O D U C T O R Y T O P I C T O

C O N T R O L S Y S T E M A N D E X P L A I N S I T SI M P O R T A N C E I N I N D U S T R Y . T H I S T O P I CC O V E R S A R E T H R E E ( 3 ) I M P O R T A N T

E L E M E N T S ; M E A S U R E M E N T I N A C O N T R O LS Y S T E M , E V A L U A T I O N A N D C O N T R O L . O T H E R

E L E M E N T S W H I C H W I L L B E E X P L A I N E D I NT H I S T O P I C A R E T H E O P E N L O O P A N D C L O S E D

L O O P S Y S T E M A S W E L L A S B L O C K D I A G R A M .

INTRODUCTION TO

CONTROL SYSTEM


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Definition of control

Importance in industry Example of application

Open-loop & closed-loop system

Case studies: ipc-201 system


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DEFINATION OF CONTROL

Acontrol system can be thought of a system whichfor some particular input or inputs is used to controlits output to some particular value, give a particular

sequence of events or give an event if certainconditions are met.


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Importance in industry

Automatically operating machinery, perhaps in aproduction line with robots, which can be used toproduce components with virtually no humanintervention.

Appliances around the home and in the office.

Consistency of product

Reduced operating costs due to improved utilization

of plant and materials and reduction in manpower.

Greater safety for operating personnel.


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Example of application

Electrical


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Pneumatic

Air brake, vacuum pump, air compressor, pneumatic cylinderext.


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Hydraulic


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Open loop & closed loop control system

Open loop control

Closed loop control

CoolingProcess

Input

Of theTemperature

Selection

Output

Of theRoom

Temperature

Switch Cooling

TemperatureMeasurement

Input

Of theSet value

ComparisonElement

Error

Correction element

Output

Of the requiredRoom temperature

Feedback of temperature information

+ -


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In an open-loop control system the output from thesystem has no effect on the input signal to the plantor process. The output is determined solely by initialsetting.

In a closed-loop control system the output does havean effect on the input signal, modifying it tomaintain an output signal at the required value.


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Open-loop system Closed-loop system

Simple

Cheap Good reliability

Inaccurate

No Feedback system

Complex

Costly Greater chance of

breakdown

Accurate

Feedback system

Comparison


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Basic Elements In Open-loop System

Control This determine the action to be taken as a result of the input

required value signal to the system.

Correction This has an input from the controller and gives an output of

some action designed to change the variable being controlled.

Process This is the process of which a variable is being controlled.

Control Correction Process

Input

SetValue

Output

RequiredValue


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Basic Elements In Closed-loop System

Control

Law

Correction

Element

Measurement

Input

Of theSet value

ComparisonElement

Error

Output

Of the requiredRoom temperature

Feedback of a signalWhich is a measureOf the variable being controlled

+

-

Process


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Comparison element This element compare the required value of the variable being

controlled with the measured value of what being achieved andproduces an error signal. Thus if the output is the required valuethen there is no error and so no signal is fed to initiate control. Onlywhen there is a difference between the required value and the actual

values of the variable will there be an error signal and so controlaction initiated.

Control law implementation element The control law element determines what action to takewhen an

error signal is received. The control law used by the element may bejust to supply a signal which switches on or off when there is anerror, as in a room thermostat, or perhaps a signal which isproportional to the size of the error so that if the error is small asmall control signal is produced and if the error is large a largeproportional control signal is produced.


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Correction element

the correction element produces a change in the process whichaims to correct or change the controlled condition.

The term actuator is used for the correction element unit that

provides the power to carry out the control action.

Examples of correction elements are directional control valveswhich are used to switch the direction of flow of a fluid and socontrol the movement of an actuator such as the movement of

a piston in cylinder. Another example is an electrical motor where a signal is used

to control the speed of rotation of the motor shaft.


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Process

The process is the system in which there is a variable that isbeing controlled, e.g. it might be a room in a house with thevariable of its temperature being controlled.

Measurement element The measurement element produces a signal related to the

variable condition of the process that is being controlled.

For example, it might be a temperature sensor with suitable

signal processing.


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T H E F O L L O W I N G A R E E X A M P L E S O F C L O S E D

L O O P C O N T R O L S Y S T E M S T O I L L U S T R A T ET H E T E M P E R A T U R E C O N T R O L , L E V E LC O N T R O L , F L O W C O N T R O L A N D P R E S S U R E

C O N T R O L U S I N G I P C 2 0 1 C S Y S T E M .

CASE STUDIES


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IPC 201C SYSTEM

Aluminum profile table

(1200 x 720 mm)

Air treatment unit:

- Manual valve.

- Filter.

- Pressure regulator withmanometer.

- Security valve (2 bar)

Button pad:

- Push-buttons: start, stop,reset.

- Selectors: 0-1, control PLC-PID.

- Emergency Stop.

Red lamp.


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Reservoir tank

Volume: 3.12 l.

Stainless steel.

Coverless for easy filling.

Draining controlled by the bottom 2/2 singleacting solenoid valve.

Allows circuit filling.


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Volume: 3.12 l

Pressurized.

Top fluid input controlled by 2/2 single actingsolenoid valve.

Bottom fluid output controlled by 2/2 singleacting solenoid valve.

Left tank


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Central tank

Volume: 3.12 l

Not pressurized.

Top input and bottom output controlled by 2/2single acting valves.

Bottom cooling / heating system based on

Peltier Cells.

Mixer moved by a 24VDC motor.


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Central tank

Temperature sensor: PTC with signal

amplifier.

Level sensor (differential pressure) with

display.

Minimum and maximum capacitive levelsensors.


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Right tank

Volume: 3.12 l

Pressurised.

Top filling valve controlled by 2/2 single actingsolenoid valve.

Pressure input controlled by 2/2 single actingpneumatic solenoid valve and pressure switchwith display.

Bottom fluid draining controlled byproportional solenoid valve.

Minimum and maximum level capacitivesensors.


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Electrical components

- Power supplies 110VAC/24VDC

- PLC.

- Industrial PIDs.

- Connection terminals.

- Displays:

+ level & flow.

- Signal conditioners.

- PWM amplifiers.


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Other devices

- Faults generationbox.

- Pump 24VDC.

- Flowmeter.


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SCADA applications

- PLC/PID control

- Manual mode.

- Exercises.

- Graphs.


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+ -

REGULADOR

(CONTROLLER)PLC/PID

ACTUATOR

PELTIER CELLS

SENSOR

PTC

Setpoint:

Environment T+ 15 - 10

Temperature closed loop control


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+-

Setpoint:Environment T+ 15 - 10

PLC/PID PELTIER

PTC


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Setpoint:

0,45 2,5l/min

+ -

REGULADOR

(CONTROLLER)PLC/PID

ACTUATOR

PUMP

SENSOR

FLOWMETER

Flow closed-loop control (1/3)


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+-

PLC/PID PUMP

FLOWMETER

Setpoint:

0,45 2,5l/min


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+-

REGULATOR

(CONTROLLER)PLC/PID

ACTUATOR

ITV

SENSOR

FLOWMETER

Setpoint:

0,45 2,5l/min

Flow closed loop control (2/3)


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+-

PLC/PID ITV

FLOWMETER

Setpoint:

0,45 2,5l/min


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+-

ACTUATOR

PROPORTIONALSOLENOID VALVE

SENSORFLOWMETER

Setpoint:

0,45 2,5l/min REGULATOR

(CONTROLLER)PLC/PID

Flow closed-loop control (3/3)


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+-

PLC/PID PROPORCIONAL

SOLENOID VALVE

FLOWMETER

Setpoint:

0,45 2,5l/min


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+-

ACTUATOR

ITV

SENSOR

DIF. PRESSURE

Setpoint:

0 200mm REGULATOR

(CONTROLLER)PLC/PID

Level closed-loop control (1/3)


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+-

PLC/PID ITV

DIFFERENTIAL PRESSURE SENSOR

Setpoint:

0 200mm


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+-

ACTUATOR

PROPORTIONALSOLENOID VALVE

SENSOR

DIF. PRESSURE

REGULATOR

(CONTROLLER)PLC/PID

Setpoint:

0 200mm

Level closed loop control (2/3)


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+-

PLC/PID

DIFFERENTIAL PRESSURE SENSOR

PROPORTIONAL

SOLENOID VALVESetpoint:

0 200mm


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+-

ACTUATOR

PUMP

SENSOR

DIF PRESSURE.

REGULATOR

(CONTROLLER)PLC/PID

Setpoint:

0 200mm

Level closed loop control (3/3)


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+-

PLC/PID

DIFFERENCTIAL PRESSURE SENSOR

PUMPSetpoint:

0 200mm


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+-

REGULATOR

(CONTROLLER)PLC/PID(ITV)

ACTUATOR

ITV

SENSOR

ITV

Setpoint:

0 1,7 bar

Pressure closed-loop control


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Consigna:

0 1,7 bar

PID

SENSOR.

ACTUATOR


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Ch 3_introduction to Control System J5800

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