Figure 1.7 A control system can actually cause a system to become ...

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15 Νοε 2013 (πριν από 3 χρόνια και 7 μήνες)

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MET 487


Summer 2013

Professor Iskandar hack

Week 1


Chapter 1



COURSE OUTCOMES

ECET 48700 Course Outcomes:

A student who successfully fulfills the course requirements will have demonstrated the ability to:


investigate and understand available transducers based on specifications and be able to select one
for use (Criterion 3a)

understand and apply the physical principles of thermal, mechanical, and optical sensors (Criterion
3b)

interpret and apply transducer specifications (Criterion 3c)



design and build analog and digital signal conditioning circuits (Criterion 3c)




OTHER COURSE INFORMATION

Textbook
:
Process Control Instrumentation Technology
, Curtis D. Johnson, 8
th

Ed., 2006

References
: Lessons in Industrial Instrumentation (PDF Version 1.30) at
http://www.openbookproject.net/books/socratic/sinst/

Web sites and other references are posted on the
course website.

Software
: PSpice, Excel and other software



Use BB Learn for Internet and Email
: The principal Internet address for this course is:
https://ipfw.blackboard.com/

Use my IPFW email address:
hack@ipfw.edu

for questions, etc. during this
course.



Homework
: I encourage you to work together on homework assignments; however, homework
must

be
individually submitted. If computer generated, use the Word format and submit using the BB Learn
Assignments. If handwritten, homework must be placed in my mailbox in the MCET office, room ET
-
221.



Labs
: Lab assignments will be posted on BB Learn. You can build/program each lab alone or in two person
lab teams. No more than 2 persons per lab team are allowed without permission of the instructor. All lab
team members must be present when demonstrating a lab. One lab report per individual is required and will
be submitted via the BB Learn assignments. (NOTE each member of the team can submit the SAME report,
but submitted separately.





Quizzes
: There will be 4 multiple choice/true
-
false quizzes taken via the web. Each quiz may be taken
twice. Sufficient time will be allowed each time you take a quiz and the higher of your two scores will count
as your grade on each quiz.



GRADING

Grading Scale & Policy:
The grading scale used will be based on the Purdue + and


scale. The grade
will be based on the total of the homework, projects, and quizzes using the following scale:



6 Labs

5 X 500 pts


= 250 pts



4 Quizzes

4 X 100 pts each

= 400 pts



10 Homework 10 X 35 pts each

= 350 pts









Total = 100%







Total=1000 pts



You can view your grades and see your current percentage grade anytime on
BB Learn
.

Grades for this course:


A+ 4.0 930
-
1000 points


A

4.0 900
-
949 points


A
-


3.7 870
-
899 points


B+

3.3 840
-
869 points


B

3.0 800
-
839 points


B
-


2.7 770
-
799 points



C+

2.3 740
-
769 points


C

2.0 700
-
739 points


C
-


1.7 670
-
699 points


D+

1.3 640
-
669 points


D

1.0 600
-
639 points


D
-


0.7 570
-
599 points (lowest passing grade)


F

0.0 less than 570 points (failing grade)



CONTROL SYSTEMS

In process control, the basic objective is to
regulate the value of some quantity


We have a desired value that is referred to as the
reference or set point


We also must have some way of measuring the
actual value of that quantity


We must also have some method of comparing
the measured quantity to the reference value


We finally need some method of changing the
quantity

EXAMPLE 1

Curtis Johnson

Process Control Instrumentation Technology, 8e]

Copyright ©2006 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458

All rights reserved.

EXAMPLE 1

The previous slide shows a system that has liquid
flowing in at some rate Q
in
, and flowing out at another
rate Q
out
.


The liquid has a height or level
h.
The formula for Q
out

is Q
out

= K*sqrt(h), thus the flow rate out of the tank is
dependent on the height

h.


If
h
is too low for the Q
out

be less than Q
in

then the
height will increase. If the height increases to a point
that Q
out
is more than Q
in
than the height will decrease.


At some value of
h

Q
out
will equal Q
in


it is at this point
the tank has
self
-
regulated

PROBLEM EXAMPLE 1 (HINT QUIZ QUESTION)

Looking at the tank in Slide 6 and given the
following information:


Q
in
= 2.5 gal/min

Q
out
= K*sqrt(h) and K = 1.2 (gal/min)


At what height will the tank self
-
regulate to?


First we must realize that the tank will stabilize
at the point that Q
in

= Q
out
, we have the
relationship 2.5 gal/min = 1.2*sqrt(h).

h = ((2.5 gal/min)/(1.2))
2

= 4.34 ft

(look at page 3 in text for same example with
different numbers)



EXAMPLE 2

Curtis Johnson

Process Control Instrumentation Technology, 8e]

Copyright ©2006 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458

All rights reserved.

EXAMPLE 2 DISCUSSION

In the previous slide a human has been
added to the process.


In this case the person can adjust the height
my opening and closing the valve to change
Q
out

in such a way that the height can be
adjusted .


In this case the controlled variable is still the
height, but the height can be manipulated by
a person changing the
manipulated or
controlling variable Q
out


EXAMPLE 3
AN
AUTOMATIC LEVEL
-
CONTROL SYSTEM REPLACES THE HUMAN WITH A CONTROL
LER AND USES A SENSOR TO
MEASURE THE LEVEL.

Curtis Johnson

Process Control Instrumentation Technology, 8e]

Copyright ©2006 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458

All rights reserved.

EXAMPLE 3 DISCUSSION

In the previous slide the person is replaced by an automatic
control system.


The height is measured by a sensor (a float or electronic),
and a controller (typically a microcomputer or other
electronic circuitry) will signal an actuator to open/close the
valve controlling Q
out


Again the height is adjusted to a set point
H

by
manipulating Q
out

Example 4


Servomechanism
-
Type Control System

EXAMPLE 4 DISCUSSION

The goal of such systems is to move the arm of the robot
using servo
-
motors from point A to point B, or any of
series of movements.


Often used in repetitive manufacturing processes


This course will NOT cover such systems, although they
use similar technologies.


This course concentrates on PROCESS Control.

FIGURE 1.5

THIS BLOCK DIAGRAM OF A CONTROL LOOP DEFINES ALL THE BASIC

ELEMENTS AND SIGNALS INVOLVED.

Curtis Johnson

Process Control Instrumentation Technology, 8e]

Copyright ©2006 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458

All rights reserved.

Thinking point


hint possible quiz question

Looking at the previous slide, and your automotive
cruse control system.


What is the control element? (hint how do you
control the speed of your car)


What is the process? (answer


the
engine/transmission/terrain/wind all have effect on
the how fast the car is moving for certain flow of
gasoline)


Measurement (answer a speed sensor attached to
the drive train (different types exist)


Controller (answer


a signal to the fuel pump)

FIGURE 1.6

THE PHYSICAL DIAGRAM OF A CONTROL LOOP AND ITS CORRESPONDI
NG BLOCK DIAGRAM LOOK SIMILAR. NOTE
THE USE OF CURRENT
-

AND PRESSURE
-
TRANSMISSION SIGNALS.

Curtis Johnson

Process Control Instrumentation Technology, 8e]

Copyright ©2006 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458

All rights reserved.

FIGURE 1.6 (CONTINUED)

THE PHYSICAL DIAGRAM OF A CONTROL LOOP AND ITS CORRESPONDI
NG BLOCK DIAGRAM LOOK
SIMILAR. NOTE THE USE OF CURRENT
-

AND PRESSURE
-
TRANSMISSION SIGNALS.

Curtis Johnson

Process Control Instrumentation Technology, 8e]

Copyright ©2006 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458

All rights reserved.

FIGURE 1.7

A CONTROL SYSTEM CAN ACTUALLY CAUSE A SYSTEM TO BECOME UNS
TABLE.

Curtis Johnson

Process Control Instrumentation Technology, 8e]

Copyright ©2006 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458

All rights reserved.

FIGURE 1.8

ONE OF THE MEASURES OF CONTROL SYSTEM PERFORMANCE IS HOW T
HE SYSTEM RESPONDS TO CHANGES OF
SETPOINT OR A TRANSIENT DISTURBANCE.


Curtis Johnson

Process Control Instrumentation Technology, 8e]

Copyright ©2006 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458

All rights reserved.

FIGURE 1.9

IN CYCLIC OR UNDERDAMPED RESPONSE, THE VARIABLE WILL EXHIB
IT OSCILLATIONS ABOUT THE REFERENCE
VALUE.

Curtis Johnson

Process Control Instrumentation Technology, 8e]

Copyright ©2006 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458

All rights reserved.

FIGURE 1.10

TWO CRITERIA FOR JUDGING THE QUALITY OF CONTROL
-
SYSTEM RES
PONSE ARE THE MINIMUM AREA AND
QUARTER AMPLITUDE.

Curtis Johnson

Process Control Instrumentation Technology, 8e]

Copyright ©2006 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458

All rights reserved.

FIGURE 1.11

GRAPH (A) SHOWS HOW OUTPUT VARIABLE
B

CHANGES AS AN ANALOG OF VARIABLE
C
. GRAPH (B) SHOWS HOW
A DIGITAL OUTPUT VARIABLE,
N
, WOULD

CHANGE WITH VARIABLE
C
.

Curtis Johnson

Process Control Instrumentation Technology, 8e]

Copyright ©2006 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458

All rights reserved.

FIGURE 1.12

AN ADC CONVERTS ANALOG DATA, SUCH AS VOLTAGE, INTO A DIGIT
AL REPRESENTATION, IN THIS CASE 4 BITS.

Curtis Johnson

Process Control Instrumentation Technology, 8e]

Copyright ©2006 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458

All rights reserved.

FIGURE 1.13

THIS ON/OFF CONTROL SYSTEM CAN EITHER HEAT OR COOL OR DO N
EITHER. NO VARIATION OF THE DEGREE OF
HEATING OR COOLING IS POSSIBLE.

Curtis Johnson

Process Control Instrumentation Technology, 8e]

Copyright ©2006 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458

All rights reserved.

FIGURE 1.14

AN ANALOG CONTROL SYSTEM SUCH AS THIS ALLOWS CONTINUOUS VA
RIATION OF SOME PARAMETER, SUCH AS
HEAT INPUT, AS A FUNCTION OF ERROR.


Curtis Johnson

Process Control Instrumentation Technology, 8e]

Copyright ©2006 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458

All rights reserved.

FIGURE 1.15

IN SUPERVISORY CONTROL, THE COMPUTER MONITORS MEASUREMENTS

AND UPDATES SETPOINTS, BUT THE
LOOPS ARE STILL ANALOG IN NATURE.

Curtis Johnson

Process Control Instrumentation Technology, 8e]

Copyright ©2006 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458

All rights reserved.

FIGURE 1.16

THIS DIRECT DIGITAL CONTROL SYSTEM LETS THE COMPUTER PERFO
RM THE ERROR DETECTION AND
CONTROLLER FUNCTIONS.

Curtis Johnson

Process Control Instrumentation Technology, 8e]

Copyright ©2006 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458

All rights reserved.

FIGURE 1.18

A PROGRAMMABLE LOGIC CONTROLLER (PLC) IS AN OUTGROWTH OF O
N/OFF
-
TYPE CONTROL ENVIRONMENTS.
IN THIS CASE THE HEATER AND COOLER ARE

EITHER ON OR OFF.

Curtis Johnson

Process Control Instrumentation Technology, 8e]

Copyright ©2006 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458

All rights reserved.

FIGURE 1.19

ELECTRIC CURRENT AND PNEUMATIC PRESSURES ARE THE MOST COMM
ON MEANS OF INFORMATION
TRANSMISSION IN THE INDUSTRIAL ENVIRONMENT.


Curtis Johnson

Process Control Instrumentation Technology, 8e]

Copyright ©2006 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458

All rights reserved.

FIGURE 1.20

ONE OF THE ADVANTAGES OF CURRENT AS A TRANSMISSION SIGNAL
IS THAT IT IS NEARLY INDEPENDENT OF
LINE RESISTANCE.

Curtis Johnson

Process Control Instrumentation Technology, 8e]

Copyright ©2006 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458

All rights reserved.

FIGURE 1.21

A TRANSFER FUNCTION SHOWS HOW A SYSTEM
-
BLOCK OUTPUT VARIAB
LE VARIES IN RESPONSE TO AN INPUT
VARIABLE, AS A FUNCTION OF BOTH STATIC INPUT

VALUE AND TIME.

Curtis Johnson

Process Control Instrumentation Technology, 8e]

Copyright ©2006 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458

All rights reserved.

FIGURE 1.22

UNCERTAINTIES IN BLOCK TRANSFER FUNCTIONS BUILD UP AS MORE

BLOCKS ARE INVOLVED IN THE
TRANSFORMATION.

Curtis Johnson

Process Control Instrumentation Technology, 8e]

Copyright ©2006 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458

All rights reserved.

FIGURE 1.23

HYSTERESIS IS A PREDICTABLE ERROR RESULTING FROM DIFFERENC
ES IN THE TRANSFER FUNCTION AS THE
INPUT VARIABLE INCREASES OR DECREASES.


Curtis Johnson

Process Control Instrumentation Technology, 8e]

Copyright ©2006 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458

All rights reserved.

FIGURE 1.24

COMPARISON OF AN ACTUAL CURVE AND ITS BEST
-
FIT STRAIGHT LI
NE, WHERE THE MAXIMUM DEVIATION IS 5%
FS.

Curtis Johnson

Process Control Instrumentation Technology, 8e]

Copyright ©2006 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458

All rights reserved.

FIGURE 1.27

THE DYNAMIC TRANSFER FUNCTION SPECIFIES HOW A SENSOR OUTPU
T VARIES WHEN THE INPUT CHANGES
INSTANTANEOUSLY IN TIME (I.E., A STEP CHANGE).


Curtis Johnson

Process Control Instrumentation Technology, 8e]

Copyright ©2006 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458

All rights reserved.

FIGURE 1.28

CHARACTERISTIC FIRST
-
ORDER EXPONENTIAL TIME RESPONSE OF A
SENSOR TO A STEP CHANGE OF INPUT.

Curtis Johnson

Process Control Instrumentation Technology, 8e]

Copyright ©2006 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458

All rights reserved.

FIGURE 1.29

CHARACTERISTIC SECOND
-
ORDER OSCILLATORY TIME RESPONSE OF A

SENSOR.

Curtis Johnson

Process Control Instrumentation Technology, 8e]

Copyright ©2006 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458

All rights reserved.

FIGURE 1.30

MULTIPLE READINGS ARE TAKEN OF SOME VARIABLE WITH AN ACTUA
L VALUE,
V
. THE DISTRIBUTIONS SHOW
THAT SENSOR A HAS A SMALLER STANDARD

DEVIATION THAN SENSOR B.

Curtis Johnson

Process Control Instrumentation Technology, 8e]

Copyright ©2006 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458

All rights reserved.

FIGURE 1.31

FIGURE FOR PROBLEM 1.4.

Curtis Johnson

Process Control Instrumentation Technology, 8e]

Copyright ©2006 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458

All rights reserved.

FIGURE 1.32

FIGURE FOR PROBLEM 1.5.

Curtis Johnson

Process Control Instrumentation Technology, 8e]

Copyright ©2006 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458

All rights reserved.