2 - block diagram.pdf
TRANSCRIPT
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Block Diagram
and
Transfer function
FUNDAMENTAL OF FEEDBACK
CONTROL
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Unit 1: Process Control Loop
Process control loop
I/P
Process
Sensor
Transmitter
Controller
Transducer
Control valve
4-20 mA
1-5 Vdc
PID
Fuzzy logic
4-20 mA
3-15 psig
dP cell
Capacitance
Radar, Sonic
Magnetic
Resistance
IR/Laser
Pressure
Flow
Level
Temperature
pH
Linear
Equal percentage
© Abdul Aziz Ishak, Universiti Teknologi MARA Malaysia (2009)
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Unit 1: Process Control Loop
Process
Sensor
Transmitter
Controller
Transducer
Control valve
Pressure
Flow
Level
Temperature
pH
dP cell
Capacitance
Radar, Sonic
Magnetic
Resistance
IR/Laser
4-20 mA
1-5 Vdc
Field/profibus
PID
Fuzzy logic
4-20 mA
3-15 psig
Linear
Equal percentage
CONTROLLER
CONTROL
VALVE
PROCESS
TRANSMITTER
PV
SP
Process control loop
PV
SP
© Abdul Aziz Ishak, Universiti Teknologi MARA Malaysia (2009)
*SP = set point
*PV = process value
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Unit 1: Process Control Loop
CO
NT
RO
LL
ER
CO
NT
RO
L
VA
LV
E
PR
OC
ES
S
TRANSMITTER
PV SP
Simulation mode
Process control loop: The Block Diagram
CONTROLLER
CONTROL
VALVE
PROCESS
TRANSMITTER
PV
SP
© Abdul Aziz Ishak, Universiti Teknologi MARA Malaysia (2009)
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Block Diagram and Signal Flow
• Rectangular block diagram-represents the cause-and-effect
relationship between the input and output of a physical
system.
• Control element-represents any of the system component
such as controller, process, sensor, transmitter, transducer,
control valve, metering pump, solenoid valve, etc.
• Arrow-represents the direction of signal flow
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Heat Exchanger
Fluid in
Steam out
Ti T desired
Fluid out
TT
TC Steam in
•Example SP
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Signal operation • Circle block diagram represents the signals operation. A
negative or positive sign is placed inside the circle to
represent deduction or addition of the respective signals.
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Takeoff point • Takeoff point is a point where the signal is diverted into
multiple flows which has similar values to various
operators or control elements.
Heat Exchanger T desired
Fluid out
TT
TC Steam in
SP
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• Example 1 Draw a block diagram for the following equation:
Step 1
a. Identify control elements: a1 and a2
b. Identify signals: x1, x2 and 5
Step 2
Identify summing junction and arrows
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Step 3
Draw and label complete block diagram.
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• Assosiative and commutative properties:
y(s)=G1(s)G2(s)x(s)
y(s)=G1(s) x1(s)- G1(s) x2(s)
*More info in Principles and Practice of Automatic Process Control 3rd
edition pg 80
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• Draw a block diagram for the following equation:
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• Determine the equation that relating y(s)
and x(s)
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• Feedback loop
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• Example
Reduce the following block diagram to canonical form,
isolating block K in the forward loop. Then, calculate C/R.
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Reduce the block diagram below to canonical form.