PSZ 19:16 (Pind. 1/07)
UNIVERSITI TEKNOLOGI MALAYSIA
DECLARATION OF THESIS / UNDERGRADUATE PROJECT PAPER AND COPYRIGHT
Author’s full name :
AHMAD FAISHAL BIN AHMAD RAZALI
Date of birth
:
24 OCTOBER 1986
Title
:
LIFT CONTROL BY USING PROGRAMMABLE
LOGIC CONTROLLER (PLC) FOR STUDENTS KITS
Academic Session:
2008/2009 – 2
I declare that this thesis is classified as :
√
CONFIDENTIAL
(Contains confidential information under the Official Secret
Act 1972)*
RESTRICTED
(Contains restricted information as specified by the
organisation where research was done)*
OPEN ACCESS
I agree that my thesis to be published as online open access
(full text)
I acknowledged that Universiti Teknologi Malaysia reserves the right as follows :
1. The thesis is the property of Universiti Teknologi Malaysia.
2. The Library of Universiti Teknologi Malaysia has the right to make copies for the purpose
of research only.
3. The Library has the right to make copies of the thesis for academic exchange.
Certified by :
SIGNATURE
SIGNATURE OF SUPERVISOR
(NEW IC NO. /PASSPORT NO.)
861024-29-5443
Date :
NOTES :
12 MAY 2009
*
NAME OF SUPERVISOR
ENCIK SHUKRI BIN ABD MANAF
Date :
12 MAY 2009
If the thesis is CONFIDENTIAL or RESTRICTED, please attach with the letter from
the organisation with period and reasons for confidentiality or restriction.
“I declare that I have read this project report and in my opinion this project report is sufficient in
terms of scope and quality for the award of
Bachelor’s Degree of Electrical Engineering (Instrumentation & Control).”
Signature
:
..........................................................
Supervisor
:
ENCIK SHUKRI BIN ABD MANAF
Date
:
12 MAY 2009
LIFT CONTROL BY USING PROGRAMMABLE LOGIC CONTROLLER (PLC)
FOR STUDENTS KITS
AHMAD FAISHAL BIN AHMAD RAZALI
Submitted to the Faculty of Electrical Engineering
in partial fulfillment of the requirement for the degree of
Bachelor of Electrical Engineering (Instrumentation & Control)
Faculty of Electrical Engineering
Universiti Teknologi Malaysia
APRIL 2009
ii “Hereby, I declare that this thesis entitled ‘LIFT CONTROL BY USING PLC FOR STUDENTS KITS’ is the
results of my own research except as cited in the references. The project report has not been accepted
for any degree and is not concurrently submitted in candidature of any other degree.
Signature
:
................................................
Name
:
AHMAD FAISHAL BIN AHMAD RAZALI
Date
:
12 MAY 2009
iii Selawat dan Salam ke atas Rasul Junjungan
NABI MUHAMMAD S.A.W.
Untuk Ayah dan Ibu Tersayang
AHMAD RAZALI BIN YAACOB
&
SITI FATIMAH BINTI YAACOB
iv ACKNOWLEDGEMENT
Assalamualaikum, greatfull to Allah because of His permission I can finish my final year
project successfull. Special thanks to my committed supervisor, Encik Shukri Bin Abd Manaf for his
guidance, ideas and help throughout this project progress.
My appreciation also goes to my family who just not give the contribution from their helps, but
also to support me troughout this project progress. Also thanks for their encouragement, caring and
spirit that has be given to me.
Besides, don’t forget for my friends, Amer Hamzah who just not give an idea and helpess for
me but also his support to finish this project. Also for Process Control Assistant, Encik Hazrul for his
help to supply me with the equipment.
Nevertheless, my appreciation to my coursemate who are give me the information that I have to
know and all the people who are involve for this project either directly or indirectly. Thank you so
much..
v ABSTRACT
Elevator is one of the system which can be controlled by programmable logic controller,PLC.
Elevator was build to help the people to moving from one floor to another without consume a lot of
people energy. Besides, its also are used to move the goods or even the car upward or downward in a
few application. Its system have a few basic operation with a few extra operation to make the system
more reliable, efficient and safe to used. There are two types of elevator depending on its application
and its place installed which is hydraulic and cable lifted elevator. The programmable logic
controller, PLC is the one of the best controller to handling this system operation due to its reliable
system. The signal use in PLC is a digital signal and the in some system, it is a analog signal. So, the
input of PLC will change the type of signal first to the suitable form of signal in PLC. It will
implement some range of analog signal to logic one in digital form and implement the logic zero for
the other range. In order to operate the system, the program that was entring by the user will execute
when the instruction is obey by the system situation and send the signal output to operate some
operation depending on the program installed. Therefore, all the system operation will be controlled
according to the sequence of the program.
vi TABLE OF CONTENT
CHAPTER
1
TITLE
PAGE
DECLARATION OF THESIS
ii
DEDICATION
iii
ACKNOWLEDGMENT
iv
ABSTRACT
v
TABLE OF CONTENT
vi
LIST OF TABLES
x
LIST OF FIGURES
xi
LIST OF SYMBOLS
xiv
LIST OF APPENDICES
xv
INTRODUCTION
1.1. History of Elevator
1
1.2. Elevator
3
1.3. Problems Statement
8
1.4. Objective of the Project
9
vii 1.5. Scope of Project
2
10
LITERATURE REVIEW
2.1. De-Lorenzo Model
12
2.2. Types of Elevator
14
2.2.1. Hydraulic Elevator
14
2.2.2. Cabled-Lifted Elevator
19
2.3. Balance
22
2.4. Safety
23
2.5. Lift Pulley system
25
2.6. Multiple Pulley
26
2.7. Power Flow Through Typical
27
Elevator
2.8. Elevator Operation State
31
2.9. Elevator Motor Drive
32
2.10. AC vs Dc Drive efficiency
34
viii 2.11. Programmable Logic Controller,
35
PLC
3
METHODOLOGY
3.1. Introduction
42
3.2. Hardware Implementation
43
3.2.1.
Pulley System
44
3.2.2.
Sensor
45
3.2.3.
Sliding Door
46
3.2.4.
DC Geared Motor
47
3.2.5.
Relay
51
3.2.6.
OMRON PLC
53
3.2.7.
Others Component
54
3.3. Softwae Implementation
3.3.1.
State Diagram
56
3.3.2.
Ladder Diagram
58
ix 4
RESULT AND DISCUSSION
4.1. Introduction
59
4.2. Result
60
4.3
5.
4.2.1.
Hardware Result
60
4.2.2.
Programming Result
63
4.2.2.1.
Up and Down operation 63
4.2.2.2.
Open and Close door
Discussion
72
76
CONCLUSION
5.1. Conclusion
78
5.2. Problems
79
5.3. Recommendation
80
REFERENCE
APPENDICE A
APPENDICE
x LIST OF TABLE
TABLE
TITLE
PAGE
Table 3.2(a)
DC Geared Motor SPG 50 specification
48
Table 3.2(b)
DC Geared Motor SPG 20 specifcation
50
xi LIST OF FIGURE
FIGURE
TITLE
PAGE
1.2(a)
Elevator
4
2.2(a)
Hydraulic Rams
16
2.2(b)
Two Hydraulic Rams
17
2.3(a)
Empty Car
23
2.3(b)
Occupied Car
23
2.4(a)
Centrifugal Governor
24
2.6(a)
Multiple Pulley
27
2.7(a)
Force on Pulley
29
2.7(b)
Pulley system implementation
30
2.11(a)
PLC Design
36
2.11(b)
Ladder diagram input symbols
38
2.11(c)
Ladder diagram output symbols
39
2.11(d)
Sequental function chart
40
3.1(a)
PLC process diagram
43
3.2(a)
Pulley system
44
3.2(b)
Double side pulley
45
3.2(c)
Limit switch
45
xii 3.2(d)
Level sensor implementation
46
3.2(e)
Sliding door implementation
47
3.2(f)
DC Geared Motor SPG 50
48
3.2(g)
Motor Up/Down implementation
49
3.2(h)
DC Geared Motor SPG 20
49
3.2(i)
Open/Close door motor implementation
50
3.2(j)
Relay
51
3.2(k)
Relay circuit
52
3.2(l)
OMRON PLC
53
3.2(m)
Counterweight
54
3.3(a)
CX-Programmer software
55
3.3(b)
CX Progrmmer ladder diagram
58
4.2(a)
Transition State
61
4.2(b)
Final State
62
4.2(c)
Basement Level
63
4.2(d)
Request from level three
64
4.2(e)
State R3 operation
65
4.2(f)
State R4 detected
66
4.2(g)
Motor Up/Down off
67
4.2(h)
Motor down on
69
4.2(i)
State R14 detected
70
4.2(j)
Motor down off
71
4.2(k)
Door open operate
72
4.2(l)
Timer count
73
xiii 4.2(m)
Door close operate
74
4.2(n)
Sensor Close detected
75
4.3(a)
Normally open
77
4.3(b)
Normally close
77
xiv LIST OF SYMBOLS
P
-
Power
I
-
Current
V
-
Voltage
T
-
Torque
ω
-
Rotational Speed
F
-
Force
We
-
Weight Elevator
Wc
-
Counterweight
DO
-
Door Open
SO
-
Sensor Open
OS
-
Open Stop
T
-
Timer
DC
-
Door Close
SC
-
Sensor Close
CS
-
Close Stop
SU
-
Switch Up
SD
-
Switch Down
CB
-
Call Button
R
-
State
D
-
Door operation
MU
-
Motor Up
MD
-
Motor Down
xv LIST OF APPENDICES
APPENDIX
TITLE
PAGE
A
Elevator Motor from the Reuland company
83
B
The Project Model
86
CHAPTER 1
INTRODUCTION
1.1.
HISTORY OF ELEVATOR
The elevator was first developed during 1800s and relied on steam or hydraulic
plungers for lifting capability. After that, the cab was affixed to a hollow plunger that
lowered into an underground cylinder. Liquid, most commonly water, was injected into the
cylinder to create pressure and make the plunger elevate the cab.
The power elevator debuted mid-19th century in the U.S as simple freight hoist
operating between just two floor in a New York City building. By 1853, Elisha Graves Otis
was at the New York Crystal Palace exposition, demonstrating an elevator with a “safety” to
break the cab’s fall in case of rope failure, a defining moment in elevator development. By
1857, the country’s first Otis passenger elevator was in operation at a New York City
department store.
2 Later, in the 1800s, with the advent of electricity, the electric motor was
integrated into elevator technology by German inventor Werner von Siemens. With
the motor mounted at the bottom af the cab, this design employed a gearing scheme
to climb shaft walls fitted with racks. In 1887, an electric elevator ws developed i n
Baltimore, using a revolving drum to wind the hoisting rope, but these drums could
not practically be made large enough to store the long hoisting ropes that would be
required by skyscrapers. Motor technology and control methods evolved rapidly. In
1889 came the direct-connected geared electric elevator, allowing for the building of
significantly taller structures. By 1903, this design had evolved into the gearless
traction electric elevator, allowing hundred-plus story buildings to become possible
and forever changing the urban landscape. Multi-speed motors replaced the original
single-speed models to help with landing-leveling and smoother overall operation.
Electromagnet technology replaced manual rope-driven switching and braking. Pushbutton controls and various complex signal systems modernized the elevator even
further. Safety improvements have been continual, including a notable development
by Charles Otis, son of original "safety" inventor Elisha, that engaged the "safety" at
any excessive speed, even if the hoisting rope remained intact.
3 1.2.
ELEVATOR
A lift known throughout the world is known as an elevator in the United
States. An elevator or lift is a transport device used to move goods or people
vertically, from one floor to another. The elevator turns electrical power into
mechanical(rotational) power. The elevator must pick up and drop off passenger as
efficiently as possible. If collection of elevator is used, a complex controller usually
controls them. There are many type of elevator or lift depending on the uses of it but
they all work in the same way. These are passenger elevator, freight elevator, vehicle
elevator, boat elevator, aircraft elevator, dumbwaiter, paternoster and others.
A lift/ elevator is made up of 4 major components. The lift/elevator cab or
platform, the shaft or hoistway, the drive system and the counterweight. The cab is
moved vertically using either hydraulic piston or a pulley system. The weight of the
cab is balanced by counterweights so that the drive system uses minimal energy.
The elevator must fit within the given space requirements of the building. It
must be made large enough to deal with the normal daily traffic and to move the
necessary objects within the building. It cannot be made too large and, therefore,
affect the structure of the building itself. Possible restrictions on the weight carried
within the elevator may be determined from the size of the motor and the other
components within the elevator system. This weight limit must be large enough to
handle daily usage.
4 Figure 1.2(a): Elevator
1.2.1.
USES OF ELEVATOR
a) Passenger Elevator
•
Designed to move the people between a building’s floors.
•
Passenger elevators capacity is related to the available floor space.
Generally, it capacities from 1,000 to 6,000 lb(455-2,727 kg) in 500
lb(230kg) increments.
•
Usually, for eight floors or less buildings, hydraulic or electric are
used with speeds up to 200 ft/min(hydraulic) and up to 500
ft/min(electric). But for buildings up to ten floors, electric and
gearless elevator are used with speeds up to 500 ft/min, and for ten
floors above, speeds begin at 500 ft/min up to
2000 ft/min.
•
Sometimes, it is used as a city transport along with funiculars.
5 b) Freight Elevator
•
Designed to carry goods rahter than passengers.
•
Often exempt from some code requirements anf from some of the
requirements for fire service.
•
Generally, it required to display a written notice in the car that the use
by passengers is prohibited, though certain freight elevator allow dual
use through the use of an inconspicious riser.
•
It is typically larger and capable of carrying heavier loads than a
passenger elevator, generally from 2,300 to 4,500 kg.
c) Vehicle Elevators
•
It is installed where ramps are considered space-inconservative for
smaller buildings(ususally in apartment building where frequent
access is not an issue).
•
The car platforms are raised and lowered hydraulically and are
connected to chained steel gears. The platform also can rotate about
its vertical axis (up to 180 degrees) to ease driver access and
accomodate building plans.
6 d) Boat Elevator
•
Used in some smaller canals.
•
The boats and small ships can pass between different levels of a
canals with a boat lift rather than through a canal lock.
e) Aircraft Elevator
•
It carry aircraft between the flight deck and the hangar deck for
operations or repairs.
•
It is designed for much greater capacity than any other elevator ever
build, up to 200,000 pounds of aircraft and equipment.
•
Smaller elevators lift munitions to the flight deck from magazines
deep inside the ship.
f) Dumbwaiter
•
Often used for the moving of small items such as dishes in a 2-story
kitchen or books in a multistory rack assembly
•
Modern dumbwaiters are generally driven by a small electric motor
with a counterweight and their capacity is limited to about 750 lb (340
kg).
7 •
Dumbwaiters are used extensively in the restaurant business (hence
the name) and may also be used as book lifts in libraries, or to
transport mail or similar items in an office tower.
•
Dumbwaiters, especially older ones, may also be hand operated using
a roped pulley.
g) Paternoster
•
It is a constantly moving chain boxes.
•
A similar concept moves only a small platform, which the rider
mounts while using a handhold and was once seen in multi-story
industrial plants.
8 1.3
1.
PROBLEMS STATEMENT
The existing model by De-Lorenzo use a lot of motor in order to operate the
door. It is consist of outside door motor and inside door motor. Each level
have its own motor to open and close the outside door. Therefore, if they have
3 level, they needs 3 motor just for operation of outside door without take
calculation for other use. The other motor that they use is for inside door and
for lift up and down the cab. So, they use 5 motor in that system which is take
more cost.
2. The existing model also not implemented in suitable pulley system. They use
simple types of combination pulley which is not having so much advantage.
That pulley system needs more energy or power in order to lift up and down
the cab.
3. Another problems is, the existing model have limiting level especially in De
Lorenzo model. By this problems, we can’t see the priority of the level in
operation time. In case whenever the cab at the lowers level and there is
signal or call at level 3 and level 5, we can see that it will stop at level 3 fist
before continue to level 5. But for the model where having 3 level, there is
limited to see the cab stop at differential level higher than one.
9 1.4.
OBJECTIVE OF THE PROJECT
There are two objective of my project which is:
1. To create the model lift controlled by Programmable Logic Control (PLC). This
system is just one of any other system which is attend to be controlled by PLC to
give the overview about what the PLC can do in any system which is related with
our daily life. Automatically, we can see the important use of PLC in its
operation.
2. The other one objective of this project is to create the training kits for students to
give the overview about the real lift operation. Besides, its just not give them
overview about the lift operation, but they also can learn about PLC, how to
setup the system with PLC, how to programming the PLC and others. Therefore,
the students can get a lot of benefits for their knowledge with this training kits.
10 1.5.
SCOPE OF THE PROJECT
The scope of this project involve a mechanical systems, electrical systems
and some programming. There is a lot of combination of electrical and mechanical
parts that are involved compare to the programming because this project is about
create the hardware. The scope of this projects are:
1) Build the lift/ elevator prototypes. The mechanical systems play the
important role in order to build the frame/ body for this project. This
body must have the suitable measurement so that it will have the
stability and strong supporting base. It can’t be very high or low
because it will effect its stability and the supporting base must be
breadth enough to support the lift structure. Besides, this base also
will provide the space for system connection with PLC and the system
circuit.
2) Implement the suitable system. The suitable system is focusing on its
pulley system in order to lift up and down the cab so that it will reduce
the energy and power consumed for that system.
11 3) Controlling the lift operation by PLC programming. The brand of
PLC that will be used for this is project is OMRON PLC. This PLC
can be programmed by CX-programming software. All the lift/
elevator operation will be depend on this programe and the error of its
operation will be adjust in this programming. Automatically, the
students will get the knowledge about PLC programming whenever
they use this system kits.
4) Make the circuit connection for the components in the system with
PLC device. The components of this systems would be all the sensor
use, motor, LED indicator, switch and others. By this scope, it involve
understanding of power consumed for each components use and the
method for connection with PLC.
CHAPTER 2
LITERATURE REVIEW
2.1
DE-LORENZO MODEL
13 The De-Lorenzo model [12] consist of real three-stop scaled down lift and
allows an innovative approach to PLC control and management. The model includes:
¾ Lift car up-down and position visual signalling at each floor
¾ Booking to be effected through buttons with flashing signaling, on priority
basis and indepedently from the lift car position.
¾ Lift car geared motor, hoist and electromagnetic brake floor, safety and lift
car deceleration limit switch.
¾ Lift car and floor door open-shut motors.
¾ Motor protection thermal relays simulated by buttons
¾ Lift car deceleration, either up and down, near the stop floor
¾ Reproduction of the inside lift car switch panel
¾ Installation graph on the panel
¾ Connection to PLC through terminals or connection
¾ Fault simulator through microswitch
¾ Power supply, single phase from mains
¾ Complete with connection cables
14 2.2.
TYPES OF ELEVATOR
There are two main types of elevator which is hyraulic elevator and cable
lifted elevator. One of the different between these two types is the method which it is
lifted and the system that it is used. For the hydraulic elevator, it is lifted from below
by a long metal shaft but for the cable lifted elevator, it is pulled up from above by a
long metal cable. The detail about these types of elevator are:
2.2.1. Hydraulic Elevators
The car/ cab of this types of elevator is lifted from below by a hydraulic ram
which is a long piston that is driven into or out of a hollow cylinder by pressure in a
hydraulic fluid as shown in figure 2.2(a) below. Usually, this fluid is oil or water,
exerts a force on any surface it touches including the base of piston.
“According to John Willey & Sons [1],Whenever the pressure in this hydraulic fluid
is high enough, the force it exerts on the base of the piston will exceed the weight of
the piston and elevator car. Then, it will make the car elevator accelerate upward.”
As the piston rises, the hydraulic fluid has more space to fill and its pressure
drops. In order to keep this piston moving upward, there must be something to
continuously add high pressure hydraulic fluid to the cylinder. This necessity is
usually an electrical powered pump.
15 It will draws low pressure hydraulic fluid from a reservoir and pumps it into the
cylinder. This pump will work on the fluid and make the elevator car lift.
When the elevator car has reached certain height, the pump stops and the
piston rests on the high pressure hydraulic fluid beneath it. As long as the amount of
this fluid is doesn’t change, the piston and car will stay where the passenger gettin
gon and off. In order to descend, the elevator opens a valve and permits the heigh
pressure hydraulic flu id to return to the low pressure reservoir. The fluid in the
cylinder has considerable pressure potential energy and that energy must go
somewhere. As it flows through the valve, the fluid accelerates and it rushes into the
reservoir at high speed. But its kinetic energy soon becomes thermal energy as the
fluid swirls around randomly. When the swirling has stopped, the fluid in the
reservoir will be warmer than it was before the elevator made its trip up and down.
The hydraulic elevator is naturally safe. Even if the cylinder springs a leak,
the hydraulic fluid will probably not flow out of the cylinder fast enough for the car
to descend at dengeroud speed. a hydraulic ram encounters very little friction and
wear, so its piston can move in or out of the cylinder rapidly.
16 Figure 2.2(a): Hydraulic rams
To see how this mechanical advantage works, suppose that you have two
hydraulic rams connected by a hose so that hydraulic fluid can flow freely from one
cylinder to the other, figure 2.2(b). One hydraulic ram is much wider than the other.
Since fluid accelerates toward lower pressure, the pressures in the two cylinders will
tend to equalize. This pressure exerts an upward force on each piston equal to the
pressure times the surface area of that piston. As a result, the upward force on the
wide piston is enough to support the weight of an elevator car while the upward force
on the narrow piston is only enough to support the weight of your hand. As things
stand, neither the elevator nor your hand move because each is supported by pressure
in the hydraulic fluid.
17 Now imagine that we begin to push down a little harder on the narrow piston.
The pressure inside that cylinder rises in order to exert an equal but oppositely
directed force on our hand. Because of the pressure imbalance, fluid begins to flow
out of the narrow cylinder and into the wide cylinder. With less fluid in the narrow
cylinder, its piston descends and our hand moves downward.
With more fluid in the wide cylinder, its piston rises and the elevator car move
upward. We are raising a heavy elevator with a hand pump.
Pushing the narrow piston inward a long distance only squeezes a modest
amount of fluid into the wide cylinder. The wide piston moves upward only a very
short distance. We have produced a huge upward force on the elevator and lifted it a
short distance by exerting a modest downward force on the narrow piston and
moving it downward a very long distance. The work we do on the fluid is equal to
the work the fluid does on the elevator car. Energy is conserved, as it must be.
Figure 2.2(b): Two Hydraulic rams
18 The piston of the narrow cylinder will reach the bottom long before the
elevator reaches the second floor. To make a more practical hand-powered elevator,
we would need to add several one-way valves and a fluid reservoir to the narrow
cylinder and convert it into a proper pump. That way we could slowly raise the
elevator upward, with ever so many cycles of the pump, fill the narrow cylinder with
fluid and then squeeze it into the wide cylinder, fill the narrow cylinder with fluid,
and so on. To return the wide piston to its original position and lower the elevator, a
bypass valve should allow the hydraulic fluid to flow back
into the fluid reservoir.
“Eventhough the hydraulic elevators are wonderful in many situations, they
do have at least two drawbacks which is stated by John Willey & Sons[1].” First, a
hydraulic elevator is only as tall as its piston and cylinder. The piston has to reach all
the way to the top floor and the equally tall cylinder must be hidden below the
ground. Burying the cylinder is quite a procedure in a tall build. A deep hole must be
drilled and the cylinder must be lowered into the hole with a crane. The difficulties
involved in manufacturing the cylinder and piston and in assembling the completed
hydraulic ram limit itsheight.
However, some hydraulic elevators are over 30 stories tall.The other
deficiency of hydraulic elevators is that there is no mechanism forstoring energy
between trips. The energy expended in lifting people up 30 floors is not saved as
those people descend. It becomes thermal energy in the hydraulic fluid as the
hydraulic fluid returns to the reservoir. For a tall building with lots of up and down
traffic, the elevator can turn a lot of electric energy into thermal energy in the
hydraulic fluid.
19 2.2.2. Cabled-Lifted Elevator
In further imrpovement for the safety, the ropes used to lift early elevators
were replaced with metal cables which were less prone to wear and aging and make
cable failure a rare event. With the safety no longer an issue, cable-lifted elevator
soon became the dominant form of elevator.
True cable-lifted elevators resemble the hand-powered one we have just
discussed, except that machines pull the cables. In early cable-lifted elevators, the
cables were pulled by steam-powered hydraulic rams. Steam was used to pump fluid
into or out of the ram and the ram’s movement was used to pull the cables. Usually,
the ram was used to separate the two halves of a multiplepulley. The cable coming
out of this multiple pulley ran over a pulley at the top of the elevator shaft and down
to the elevator car itself. As the two halves of the multiple pulleys were drawn apart,
they drew in more cable and lifted the elevator car. As fluid was released from the
hydraulic ram, the multiple pulley released cable and the elevator car descended.
The first improvement that appeared in cable-lifted elevators was the
counterweight. Lifting the elevator car by itself requires a considerable amount of
work because the car’s gravitational potential energy increases as it rises. It would be
nice to get back this stored energy when the car descends. Unfortunately, it’s hard to
turn gravitational potential energy back into highpressure steam. However, it’s
possible to use that energy to lift a counterweight. The counterweight in an elevator
descends when the car rises and rises when the car descends. Because the two objects
have similar masses, the total amount of mass that is rising or falling as the elevator
moves is almost zero. The overall gravitational potential energy of the elevator is not
changing very much; it’s simply moving around between the various parts of the
machine.
20 The counterweight balances the car so that it takes very little power to move the
system. The elevator and counterweight resemble a balanced seesaw, which requires
only a tiny push to make it move.
The counterweight on most elevators hangs from its own cable attached to
the elevator car. That cable travels from the car, over pulleys at the top of the
elevator shaft, and down to the counterweight.
“As stated by John Willey and Sons [1], the counterweight is usually equalto the
mass of the empty elevator car plus about 40% of the elevator’s rated load.”
Thus, when the elevator is 40% filled, the counterweight will exactly balance
thecar and very little work will be done in raising or lowering the car. Most modern
elevators are driven by electric motors. The advantages of electric motors are their
variable speeds of rotation, high torque, and reliability. While we will save our
discussion of electric motors for a later chapter, we will note here that electric motors
can be made to operate efficiently at many rotational speeds, torques, and overall
power-levels. The output power of an electric motor is frequently rated in
horsepower and the motors used in elevators may be as large as several hundred
horsepower.
Because early electric motors could not deliver so much mechanical power,
the first electric elevators used winches to lift their elevator cars. The cable from
the elevator car was actually wound up on a drum at the top of the elevator shaft.
The counterweight was attached to a cable that was also wound on the drum.
The two cables were arranged so that the counterweight cable unwound as the
car cable wound up. An electric motor used gears to turn the drum. This winch
mechanism had a number of disadvantages. It raised or lowered the car relatively
slowly because the gearing limited the rate at which the drum could be turned. The
21 overall height of the elevator was limited because the drum had to be able to hold all
of the cable when the elevator was at the top of its travel. The diameter of the drum
was constrained by the need to keep torques low and only about 100 m of cable
could be accommodated.
Instead of winding and unwinding cable from a drum, most modern elevators use
traction to draw a cable over a drum.
The cable rises from the elevator car, travels over the traction drive drum and
then descends into the elevator shaft where it’s attached to the counterweight. An
electric motor turns the traction drive drum. When high speed is not important, the
drum can be turned by a small motor through the use of gears. However, in tall
buildings, the drum is usually turned directly by a large motor. Elevators of this type
can run at speeds as high as 10 m/s (22 mph) in buildings of any height.
The mechanical power required from the drive motor depends on how well
balanced the car and counterweight are. If the elevator car is loaded to 40% of
capacity so that the two weights are balanced, the motor will have little difficulty
in moving the car up or down. If the car is particularly empty or particularly full,
the motor will have to provide considerable mechanical power when lifting the heavy
side of the system and various brakes will have to absorb energy released by the
elevator when the heavy side descends. The motor’s maximum mechanical power,
together with the strength of the cables, limits how much weight the elevator can lift.
In many freight elevators, the car is lifted by a multiple pulley so that a single
segment of cable doesn’t have to support the entire load. Even when a single pulley
is used, several separate cables support the car, both for safety and to reduce cable
stretching. Cable stretching is a serious problem in tall elevators. Tension always
tends to pull things apart, so a cable becomes longer. Like most objects, a cable
behaves as a spring when it’s subject to tension. Its length increases by an amount
22 proportional to the tension it experiences. As people enter the elevator car and its
total weight increases, the tension on its support cable increases and that cable
stretches slightly. Modern elevators are equipped with automatic leveling systems
that turn the traction drum to make up for the stretching of the cables.
The passengers are unaware of this careful adjustment taking place as they
step on or off the elevator. Nonetheless, we may be able to feel the cable stretch if
you bounce up and down on a cable-lifted elevator.
2.3.
BALANCE
“According to John Willey & Sons [1], the elevator cars must remain level no
matter where the passengers choose to stand. The only way to keep the car level is to
make it run along a vertical track.” To see why the track is necessary, consider the
case of an empty car, figure 2.3(a). The lifting force on the car is exerted at the
middle of the elevator car, at either its top or its bottom. The center of mass of the
empty car is also at the middle of the elevator car so the lifting force exerts no torque
on the car about its center of mass. The car remains level. Now consider what
happens when passengers enter the car and begin to walk around inside, figure
2.3(b). The center of mass of the car moves with the people inside. Now the lifting
force exerts a torque on the car about its new center of mass and it tends to rotate.
The best way to prevent the car from tilting is to confine the car on a track. The rails
of the track exert the torques needed to keep the car level.
23 Figure 2.3(a): Empty car
2.4.
Figure 2.3(b): Occupied car
SAFETY
All cable-lifted elevators have safety devices to keep them from falling if
their cables break. Most modern elevators have more than one lifting cable, but they
still require mechanisms to ensure that there are no accidents.
The original safety device that Otis developed for his first elevators had
jaws that would grab onto the rails of the elevator track if there were a loss of
tension in the supporting cable. If the cable broke and its tension vanished,
springs would force the jaws into the track.
Modern elevators use mechanisms that monitor the vertical speed of the
elevator. If the speed exceeds a certain permissible value, brakes on the car grab
the tracks. This speed control prevents a nearly empty elevator from moving
24 upward too quickly just as it prevents a full elevator from falling. One such
speed-sensing device is the centrifugal governor, a mechanism that senses how
quickly a shaft is turning. This is shown in figure 2.4(a) below. When it’s used with
an elevator, the shaft is turned by a pulley on a special cable attached to the elevator
car. The faster the elevator moves, the faster the shaft turns. The centrifugal governor
swings several masses around in a circle. Since the masses travel in uniform circular
motion, they need some centripetal force to accelerate them toward the center of the
circle. In the centrifugal governor, this centripetal force is exerted by several rods
that are held apart by a spring.
As long as the shaft is turning slowly, the spring can keep the rods from
moving together. But when the shaft is turning quickly, the centripetal force becomes
very large and the rods compress the spring. As the rods move, they push
on a lever. In the case of the elevator, this lever activates brakes that slow the
elevator
down.
Figure 2.4(a): Centrifugal governor
25 A centrifugal governer uses the principle that a central force is required to
accelerate masses around in a circle. As long as the shaft is stopped or spinning
slowly, the spring can keep the upper and lower rods apart. But once the shaft spins
too quickly, the masses swing outward and the sense lever is shifted.
2.5. LIFT PULLEY SYSTEM
There are many ways to lift an object by using the pulley system. But, each
method use have their own advantage compare with others. There are three types of
pulleys which is a fixed pulley, a movable pulley and a combined(compound) pulley.
Fixed Pulley
Movable Pulley
Combined Pulley
Combined Pulley
26 2.6.
MULTIPLE PULLEY
In a multiple-pulley, the cord goes back and forth between a fixed set of
pulleys and a moving set of pulleys as shown in figure 2.6 (a). The far end is tied to
one of the pulley sets. It’s important that the cord pass easily over the pulleys. Now
when you create tension in the cord, that same tension appears on every segment of
cord between the two sets of pulleys. If you exert 500 N of force on the cord, each
cord segment will have 500 N of tension. As a result, the two sets of pulleys will be
pulled together with 500 N of force for each segment of cord connecting them.
If there are 4 cord segments attached between the top of the elevator and the fifth
floor, then the total lifting force on the elevator and bathtub will be 2000 N. Since the
bathtub and elevator only weigh 1800 N, they will experience a net upward force and
will accelerate upward.
While it takes less force on the cord to lift the bathtub and elevator with a
multiple pulley than with a single pulley, you don’t get something for nothing.
To lift the elevator 1 m, you must shorten each segment of cord by 1 m. Since
there are 4 segments, you will have to pull 4 m of cord through the system of pulleys.
You are obtaining mechanical advantage, using a modest force exerted over
a long distance to obtain a larger force exerted over a shorter distance. The
amount of work required to lift the bathtub and elevator to your apartment is the
same, whether you use a single or multiple pulley. The multiple pulley merely
allows you to do this work more gradually, with a smaller force exerted over a
longer distance.
27 Figure 2.6(a): Multiple Pulley
2.7. POWER FLOW THROUGH A TYPCAL ELEVATOR:
The simplest theory of operation for pulley system assumes that the pulleys
and lines are weightless and that there is no energy loss due to friction. Its also
assumed that the lines do not stretch. In equilibrium, the total force on the pulley
must be zero which is meana that the force on the axle of the pulley is shared equally
by the two lines looping through the pulley.
28 The product of the weight lifted times the distance it is moved is equal to the
product of the lifting force (the tension in the lifting line) times the distance the
lifting line is moved. The advantage of the pulley system is defined as the weight
lifted divided by the lifting force.
There is a transfer of power throughout the elevator system. Electrical power
put into the motor is equal to:
(for an AC motor)
(2.71)
This power is then transferred through the output of the motor shaft,
(2.72)
.
Where T is the torque and ω is the rotational speed. Once the power is transferred
through the gear reducer the output speed will be reduced and the torque will be
greater. The overall power will be slightly lower as the system is not 100% efficient.
Tension on the rope from the elevator pulley is equal to the weight of the elevator,
We. The tension on the rope from the counter weight is Wc.
29 Figure 2.7(a): Force on Pulley
By refering to the figure 2.7(a), “the analysis has been done by Rhonda
Salzmon that conclude the force on the driving pulley is equal to the difference of the
two exerted tensions on each side [2].” On one side, this force is equal to We and on
the other side, it is Wc. Therefore, the net force exerted on pulley 1 (the drive pulley)
is:
F = (We – Wc) / 2
(2.73)
In order to find the power required for elevator movement, either the rotational speed
of the drive shaft (attached to pulley 1) or the velocity of the elevator must be known.
The output power is (assumming 100% efficiency),
30 (2.74)
where r is the radius of the pulley (pulley 1).
Figure 2.7(b): Pulley system implementation
A roping system is used to attach the motor/gear reducer, the elevator car and
the counter weight. There are many different kinds of arrangements that can be used.
In one possible arrangement, such as shown in figure 2.7(b), both ends of the
elevator rope are anchored to the overhead beam. Both the elevator car and the
counter weight are attached to free moving pulleys. The traction drive is attached to a
stationary pulley.
The traction drive is the method of converting the input mechanical power (in
this case the turning of a shaft) into useable mechanical power in the system (the
vertical movement of the elevator). The friction between the ropes and the sheave
grooves, which are cut on the pulley, initiates the traction force between the traction
drive and the rope.
31 When the traction drive, rotated power is transferred from the traction drive to
the elevator car and counter weight. Power is only needed to move the unbalanced
load between the elevator and the counterweight.
2.8.
ELEVATOR OPERATION STATE
2.8.1 Single Elevator
The elevator have three operation states generally. This states are normal
mode, fire-protection mode anf maintenance mode. The most priority is depend on
maintenance mode which have the ability to cancel all the operation.
The second priority is considered to fire-protection mode where it will return
to bottom floor or base immediately in case there is a fire accident. It will goes to
normal mode when the fire switch for the fire-protection mode is reset.
“The basic task for the elevator control system as stated by X.Ying, Q.Zhu &
H.Xu [3] is to command the elevator to move up or down, to stop or start operation,
and to open or close the door. However, for a few case it have some constraints for
example in the case where there is a calling/requests from users in different level.”
The cab will visit the corresponding floor and the illumination is canceled
when the corresponding floor is visited by the cab elevator.
The common elevator has two buttons on the floor control panel except the
first and the top floor to request either to go up or down level.
The elevator cannot stop at a floor unless there is a request from the user. If
there is no request, it will remains at its current floor with the close door.
32 2.8.2 Two Parallel Elevator
For this system, the basic operation is the same as the system for the single
elevator, but it has the extra operation cause by the related operation of two elevator.
The elevator will test if the stop is required or not depending on the request from the
user.
“According to X.Ying,Q.Zhu & H.Xu [3], to balance the number of stops, the
operation of two elevator will follow a certain dispatching principle. An elevator will
not to stop at a floor if the another elevator was readily stop. In order word, it must
be at least one elevator operate when the another elevator is at the stop operation.
Besides, the first elevator will not to stop at the floor where the second elevator has
been stopped. This level request will make the second elevator to be operate.”
2.9.
ELEVATOR MOTOR DRIVE
The types of motor drive used in real elevator system is depend on its
application. For the one to six storey buildings its often use hydraulic elevators. In
this system, it have A/C motors connected to hydraulic pump and work similar to car
lift at service station.
For the low and mid rise buildings, it is most often use geared traction
elevator systems. In this system, the motor drive used is either A/C motor or D/C
motor that is connected to gearbox and then to a drive sheave that moves the cables.
33 2.9.1 D/C geared motor
For the geared D/C machine, it will typically use either Silicon Control
Rectifier,SCR drive or Motor Generator Set,MGS. The MGS is the older technology
used adn seldomto seen on new installation.
2.9.2 A/C geared motor
In other side, the geared A/C machine will use a Variable Voltage Variable
Frequency,VVVF which can give precise elevator control. The example model of
VVVF A/C geared motor can be refer to the Appendix A. The model is from
Reuland Electric company. The Variable Frequency A/C drives can be divided into
two categories which is inverter drives and flux vector drives. Inverter drives
typically used for low speed and open loop application. The simplest types of this
drives are non-regenerate, where it don’t have teh ability to return regenerated energy
back to the A/C line when overhauling. Regenerated energy must be dissipated
across resistor in the form of heat. For the Flux vectoe drives, it is typically used for
high performance and closed loop applications with speeds above 150 fpm. The
standard os Flux vector drives is also non-regenerative. The resistor is required for
dissipating regenerated energy.
The gearless A/C or D/C machine is used on the most mid to high rise
buildings. For this system, the motor has the drive sheave attached directly to the
motors shaft. The drive systems used for this gearless machine is the same types as
used in the geared machines. “ According to Motion Control Engineering
Incorporated [4], in the most gearless applications, the best choice is D/C machine.
However, if the D/C motor is damaged or defective, the replacing with an A/C motor
will not result in improved performance.”
34 For the A/C gearless applications, there are two major concern to drives the
decision making process which is heat and cost.
2.10.
A/C vs D/C DRIVE EFFICIENCY
Generally, the A/C regenerated drives is the most efficient drive system. This
is because the A/C regenerated drives has unity power factor under all operation
conditions. For a non-regenerative A/C drive, it cannot return regenerated enery back
to the A/C line when overhauling. Instead, this regenerated energy must be
dissipared across resistor in the form of heat.
“ As stated by Motion Control Engineering Incorporated [4], the D/C drives is
more efficient compare to the A/C non regenerated due to the fact that all elevator
D/C drives are regenerative which is capable of returning power back to the power
line.”
Besides, the A/C non-regenerative drives dissipates regenerated energy in the
form of heat into machine room environment. If the air conditioning equipment is
needed to dissipate this energy, it will provide to the loss in efficiency. However, if it
is seen by the issue of power factor, the A/C non-regenerative drive have a closer to
the unity rather than D/C drive which is highly variable for the power factor.
The amount of energy returned during regeneration increses in proportion to
the machine efficiency whether it is a geared or gearless system. For a 30 Horse
Power(30 HP) geared machine regenerated power amount, it could reach 9KW or
more regenerative power in the form of heat at 64% efficiency. In other side, for the
gearless machines, heat dissipation can easily exceed 16KW of regenerative power
for 30 HP motor at 80-90 % efficiency.
35 2.11.
PROGRAMMABLE LOGIC CONTROLLER (PLC)
2.11.1.
Introduction
The first Programmable Logic Controller, PLC was developed by a group of
engineers at General Motors in 1968. It was developed when that company were
looking for an alternative to replace complex relay control system. The term
‘programmable logic controller’ is defined by EN 61131-1 as a digitally operating
electronic system which uses a programmable memory for the inernal storage of
user-oriented instructions for implementing specific functions such as logic,
sequencing, timing, counting and arithmetic to control through digital or analogue
inputs and outputs, various machines or process.
PLCs have been gaining popularity on the factory floor and will probably
remain predominant for some time to come. “ The advantage of PLC as stated by Dr.
Hisham El-Sherif [5] are: ”
I.
II.
Effective cost for controlling complex systems.
Flexible and can be reapplied to control other systems quickly and
easily.
III.
Computational ability allow more sophisticated control.
IV.
Trouble shooting aids make programming easier and reduce
downtime.
V.
Reliable components make these likely to operate for years before
failure.
36 “ The PLC which is stated by Festo Didactic [5], is represents such a
universal controller where it can be used for different applications and via the
program installed in its memory, provides the user with a simple means of changing,
extending and optimising control process.”
The PLC has sizing into three categories which is small, medium, and large.
The small PLC covers units with up to 128 inputs outputs, I/O and memories up to 2
Kbytes. This PLC’s are capable of providing simple to advance levels or machine
controls. The medium size have up to 2048 I/O’s and memories up to 32 Kbytes. The
larger PLC is the most sophisticated units of the PLC family. They have up to 8192
I/O’s and memories up to 750 Kbytes. It can control individual production processes
or entire plant.
2.11.2. Basic Design of PLC
Figure 2.11(a): PLC design
37 By refering to the programmaable logic controller, PLC design as shown in
figure 2.11(a) above. The function of each components are:
Function:
1. Input Module -
Convert incoming signals into signal which can be
processed by PLC and pass it to central control unit.
2. Output Module -
Perform a reverse task of input module. It converts the
PLC signal into signal suitable for the actuators.
3. Central Control Unit -Process the signal accordiing to the program stored in
memory. Its also provides intelligence to command and
govern the activities of thenentire PLC systems.
4. PLC Program -
The desired program of sequence of operation and
control instruction which is entered by programmer.
2.11.3. PLC Programming Language
The program of PLC can be created in various ways which is via assembler
type commands in ‘statement list’ (higher level), problems-oriented languages such
as ‘structured text’ or in the form of flow chart which represented by ‘sequential
function chart’. The other programming language that be used are ‘function block
diagram’ based on function charts with graphic symbols and ‘ladder diagram’.
38 The function block diagrams is widely used in Europe and the ladder diagram is
preferred language by users in America.
Ladder Diagram:
Ladder diagram is the main programming method for PLC. It has been
developed to mimic the relay logic. A relay is a simple device that use magnetic field
to control a switch. When the voltage is supplied to input coil the resulting current
will create a magnetic field. This magnetic field will attract a metal switch toward it
and make it to contact the other part. This programming language is a computer
program where the user can enter and change. For the logic input, there were three
types of input. There are normally open, normally close and immediate input
fuction,IIT. The IIT function allow inputs to be read after the input scan while the
ladder logic is being scanned. The example of these ladder diagram is shown in the
figure 2.11(b) below.
Figure 2.11(b): Ladder diagram input symbols
39 For the Ladder Logic Output, there are multiple types of outputs but there are
not consistently available on all PLCs. Some of these output will externally
connected to devices outside PLC but its also possible to use internal memory
locations in the PLC. The figure 2.11(c) shows the six type of output which are
normal output, normally on, one short relay (OSR), latch (L), unlatch (U) and the
Immediate output (IOT).
Figure 2.11(c): Ladder diagram output symbols
40 Sequential Function Chart (SFC):
SFC have been developed to accomodate the programming of more advanced
systems. It is similar to flowcharts but much more powerful. By referring to the
instruction show by the figure 2.11(d), to read the chart, start at the top by says start.
Below this, there is the double horizontal line that says follow both paths. The result
for this instruction will make the PLC start to follow the branch on the left and right
hand sides separately and simultaneously. For the left, there are two functions where
the first is power up function and the second is power down. On the right hand side is
the flash function that will be run until it is done. This method is different from
flowcharts because it does not have to follow a single path through the flowchart.
Figure 2.11(d): Sequental function chart
41 Structured Text (ST):
Structure text programming has been developed as another modern
programming language. It is quite similar to BASIC language. The example of this
programming language is shown below. In this example, ‘i’ is used as a PLC
memory location for an integer. The ‘RETURN’ is used to recall the value in
location ‘i’. Then it will add by 1 and returns it to the same location. The next line
will check to see if the loop should quit. If ‘i’ is greater than or equal to 10, the loop
will quit but otherwiae the program will go back to the ‘REPEAT’ statement.
Everytime the program goes through this loop, i will increase by 1 untill it reach the
value of 10.
CHAPTER 3
METHODOLOGY
3.1
Introduction
Programmable Logic Controller (PLC) play an important function for
this project to control its overall operation. These operation include the instruction
for lift up/down and open/close door. Input from calling button and level sensor(limit
switch) will feed into PLC input module. These input will be send to Central
Processing Unit(CPU) inside PLC to process as required by instruction program. The
instuction program will determine the sequence of operation. After being process by
CPU, it will send the signal as the output to be feed to actuator like motor for this
case. The process diagram is shown in figure 3.1(a) below.
43 Figure 3.1(a):
3
PLC
C process diaagram
3.2
Hardw
ware Impleementation
LIFT SR
RUCTUREE
SENSO
OR
LEVEL SENSOR
PULLEY
SLIDING DOO
OR
COMBINE
D PULLLEY
44 3.2.1
Pulley System
The types of pulley used is combined pulley. For this types, the two
end joint will be hanging or fixed so that it will reduced the power or energy
consumed to lift the cab. The figure and general mathematical model for this
system is shown in figure 3.2(a) below:
Figure 3.2(a): Pulley system
Double side pulley was used for this project to provide stronger tied so that it
can avoid the cab falling down when there is broke up on the rope. The second
side pulley will cover the cab from falling down when the first side has the rope
broken. The example is shown in figure 3(b) below.
45 Figure 3.2(b): Double side pulley
3.2.2
Sensor
Level sensor was used for this project to detect the level arrived. This
sensor also functioning as the system input to tell the programmable logic
controller(PLC) about the current situation of the system(cab position). The
type of level sensor used for this purpose is limit switch. This is shown in
figure 3.2(c) and the implementation of it is shown in figure 3.2(d) below.
Figure 3.2(c): Limit switch
46 Specification:
a) Long lever with roller
b) Lever length: 27.5mm
c) Size: 10mm x 28mm x 16mm
Figure 3.2(d): Level sensor implementation
3.2.3
Sliding Door
There are a several components used for this part. The component
used for real sliding door is not provided for prototype uses. Therefore the
implementation for
this part come from my creativity that i have so that it will
operate like real sliding door operation. The components used are nilon rope, holding
metal, roller, dc geared motor,limit switch and others. The system implement is
shown in figure 3.2(e) below.
47 Figure 3.2(e): Sliding door implementation
Limit switch also used for this system to get the information of door position.
When holding metal touch the first limit switch during open door operation, it will
send the signal as the input for programmable logic controller(PLC) to tell that the
door is fully open so that the PLC will give the command according to the instruction
that was programmed. Usually, the instruction for this case is to stop the motor so
that it will not pull the door anymore.
3.2.4
DC Geared Motor
There are two DC Geared Motor used for this project which is for lift
up/down and open/close door. Even this two motor have same voltage capacity (12
volt), but it is different from the the torque and load capacity.
48 3.2.4.1 DC Geared Motor SPG 50 (12 Volt)
For lift up/down motor, 12 volt DC Geared Motor SPG 50 model from
Cytron company was used. The model is shown below in figure 3.2(f). The
implementation of it is shown in figure 3.2(g).
Figure 3.2(f): DC Geared Motor SPG 50
Specification:
Rated
Voltage(V)
12
No Load
Rated
Current
Speed
Current
Speed
mA
r/min
A
r/min
≤ 200
225
≤ 1.1
170
Output
Torque
kgf.
mN.
cm
m
2.0
196
Table 3.2(a): DC Geared Motor SPG 50 specification
Weight
Power
W
3.4
g
280
49 Figure 3.2(g): Motor Up/Down implementation
3.2.4.2 DC Geared Motor SPG 20 (12 Volt)
This motor is used to open and close the cab door. It have same rated voltage
as the motor Up/Down but it have its own criteria especially on torque, speed
and
output power. This model is shown in figure 3.2(h) below and the implementation of
it is shown in figure 3.2(i).
Figure 3.2(h): DC Geared Motor SPG 20
50 Specification:
Rated
No Load
Rated
Voltage(V) Current Speed Current Speed
mA
12
≤ 30
r/min
150
A
≤ 200
Output Weight
Torque
Power
r/min
kgf.cm mN.m
W
130
0.6
58.8
0.6
Table 3.2(b): DC Geared Motor SPG 20 specifcation
Figure 3.2(i): Open/Close door motor implementation.
g
60
51 3.2.5
Relay
Relays play an important role for most operation. It will determined the
direction of DC Geared motor for both operation (up/down and open/close). Two
relays was used for up/down operation circuit and two for open/close door. When
relay one is turn on by the PLC according to instruction, it will change the polarity so
that the motor will have potential different to make it running in one direction. This
operation also the same when relay two was turning on by PLC in other situation to
make it run in other direction. Single pole double through types of relay was used for
this project with relay voltage of 24 volt. This component is shown by figure 3.2(j)
below.
Figure 3.2(j): Relay
52 3.2.5.1
RELAY CIRCUIT
Figure 3.2(k): Relay circuit
The circuit in figure 3.2(k) show the relay circuit for up/down cab and
open/close door operation. There are two voltage supply which is from external
supply and from PLC. The external voltage will supply 9 volt fixed voltage for
open/close door motor and 12 volt fixed for up/down motor. In normal situation, the
motor doesn’t have voltage different and will stay until one of the relay change its
polarity to provide voltage different.
53 3.2.6
OMRON PROGRAMMABLE LOGIC CONTROLLER (PLC)
The programmable logic controller(PLC) is used to control the whole
operation of the system according to the instruction given by the programmer/user. It
is the main part which is give the figure of the electrical controller in that mechanical
system. Without PLC, the system is just a mechanical system which is not operates.
The OMRON SYSMAC CPM2A model PLC is used for this project which is have
22 input and 14 output modul. This PLC is programmed by using Ladder
Diagram(LD) method. The PLC used is shown in figure 3.2(l) below.
Figure 3.2(l): OMRON PLC
54 There are two PLC used for this project according to limited input output.
Therefore the operation of the system is separate by two part which is lift up/down
for PLC 1 and open/close door operation for PLC 2. To synchronize this two
operation, some of the output from PLC 1 is feed to the input of PLC 2. The output
of PLC 1 is used to give the information to PLC 2 about the current situation so that
PLC 2 will operate as the information given is matching to the instruction that is
programmed.
3.2.7
OTHERS COMPONENTS
3.2.6.1 Counterweight
Counterweight is used to balanced the cab and support drive system so that the motor
will used minimal energy to pull the load. The example is shown in figure 3.29(m)
below.
Figure 3.2(m): Counterweight
55 3.3
Software Implementation
The software used for programming the programmable logic
controller(PLC). The name of the software used for this project is CXProgrammer which is used to make the program for OMRON PLC. It
implement the program in the form of Ladder Diagram(LD). The software
used is shown in figure 3.3(a) below.
Figure 3.3(a): CX-Programmer software
Before build the Ladder Diagram, the overall operation is implement in the
state diagram. State diagram will make the operation easily to form in Ladder
Diagram. We cannot easily build Ladder Diagram for the whole operation before
simplify it with state diagram.
56 3.3.7
State Diagram
For this system, there are two general operation to be controlled by
programmable logic controller,PLC. That operations are lift up/down and open/close
door operation. There is other operation which is on/off indicator but it was included
to up/down operation by using PLC 1. The state diagram for both operation is shown
in the diagram below. The symbols used in this diagram can be refer to list of
symbols in page ?.
Open/Close Door Operation
57 Lift Up/Down Operation
START SU1.SD1
Ro R15.SD1
(CB2 + CB3 + CB4 + CB5).R0.D’.CB1’
R15 R1 R14.CB1.CB2’. D’
R15. MU’
R1.SU2
R14.CB1’.(CB3+CB4+CB5)
R2 R14 R1.MD’
(CB3+CB4+CB5).
R13. MU’
R13.SD2
CB1. R2. CB3’. CB4’. CB5’
CB2’. D’. R2
R3 R13 MD MU (CB1+CB2). R12. D’. CB3’
R3.SU3
R12. CB2’. CB1’.(CB4+CB5)
R3.MD’
R4 R12 R11. MU’
R11.SD3
R4.CB4’.CB5’(CB1+CB2)
R5.MD’
(CB4+CB5).CB3’. D’. R4
R11 R5 CB1+CB2+CB3). R10. D’. CB4’
R6 R10 R9. MU’
R5.SU
R10.CB2’.CB1’.CB3’.CB5
R6. CB5’. (CB3+CB2+CB1)
R6.CB5.CB4’.D’
R9. SD4
R7 R9 (CB1+CB2+CB3+CB4). R8. D’. CB5’
R7.SU5
R8 R7.MD’
58 3.3.8
Ladder Diagram
CX-Programmer software will implement the instruction program in
the form of Ladder Diagram. The figure 3.3(b) below shown the example of
Ladder Diagram by using the CX-Programmer software.
Figure 3.3(b): CX Progrmmer ladder diagram
CHAPTER 4
RESULT AND DISCUSSION
4.1
Introduction
This project involve hardware and software for support the operation. Mostly,
the focus is given to build the system hardware. The software is used to program the
Programmable Logic Controller, PLC to govern the operation for elevator. Besides,
this programming also can be used to monitor the operation of the system as it is
programmed. The programming used for this project is Ladder Diagram provided by
CX-Programmer software for OMRON PLC. Therefore, the result will be take for
the hardware operation and the programming simulation.
60 4.2
Result
4.2.1
Hardware Result
Eventhough this project result will be seen for the system operation, its
operation generally just involved lift up down and open close door. The other
operations like the priority of the calling button or user request cannot be seen by
picture. It will limit our hardware result to showed and can be represented by the
basic operation of the elevator for the request to move up or down and to open or
close the door.
For the lift up and down, the result can be observed that, when the cab have
arrived at certain level, it will touch the sensor level (limit switch for this case). At
this time the sensor will close the circuit and make a current to flow. The current will
be feed to the PLC input as a input signal so that the processor will matching the
information with instruction program to take the action. As a result, the lift motor
will be stopped and turn on the indicator. This result is shown in figure 4.2(a) and
figure 4.2(b) below for transition state and final state operation.
61 Lift Up/Down operation:
Figure 4.2(a): Transition State
The PLC will execute the program after receive the input signal and then send
the output signal to the motor. The cab will be moved upward or downward
according to request from or to other level. the transition state operation is shown in
figure 4.2(a) above.
62 Figure 4.2(b): Final State
After the cab arrive at certain level (request level), it will touch the level
sensor and feed the signal to the PLC as input signal. The processor wil execute the
program and send the output signal to motor and indicator. If the level is requested
by the user, the PLC will sent the output signal to the motor to make it stop the
operation and to turn on the indicator. The result is shown in figure 4.2(b) above.
63 4.2.2
Programming Result
For the CX-programmer ladder diagram, the operation state is shown by the
green highlighting colour. It can provide the monitoring operation without
connecting the PLC with the system hardware to observe the operation. We can
easily simulate the program by using the indicator output in OMRON PLC before
connecting it to the system hardware.
4.2.2.1. Up and Down operation
CASE 1 : The cab at the base level. When there is a calling button from level three,
the instruction will turn ON the motor up,MU and make the cab going
upward. The simulation will show the program running by green highlight.
Figure 4.2(c): Basement Level
64 Transition State R1:
When there is a call button from level three, the program will run the state
R1. This state will turn the motor up, MU to move the cab. The program running is
shown in figure 4.3(b) below.
Figure 4.2(d): Request from level three
65 Level 2 (state R2):
The cab will touch sensor at level two/ state R2. The program will identify
either there is request from this level. If there is no request from this level, the
program will run the next state R3 to turn on motor up, MU to continue the
operation. This running program is shown in figure 4.3(c) below.
Figure 4.2(e): State R3 operation
66 Level 3(state R4):
When the cab touch the sensor at level three, the program will detect the
request and turn off the motor as shown in figure 4.3(d).
Figure 4.2(f): State R4 detected
67 If the level is the same as requested by the user, the program will give the
instruction to off the motor. The motor up off is shown by figure 4.3(e) below.
Figure 4.2(g): Motor Up/Down off
68 CASE 2:
The cab is in stop operation at level three. When there is request from
level 1 by the user, the program will run and make the system to
operate.
Request from level 1(CB1) 69 Transition state, R12:
For this state, the program will turn on the motor down to move the cab
downward. The simulation result is shown in figure 4.3(f) below.
Figure 4.2(h): Motor down on
70 Level 2(state R14):
The cab will touch the sensor down for the level two and the
program will identify any request from this level. If there is no
request, the program will execute the next state, R15 to
continue motor down, MD on. The simulation is shown in
figure 4.2(i) below.
Figure 4.2(i): State R14 detected
71 Final state, R0:
When the cab touch the sensor down at level one, the program will
turn the motor down, MD off as shown on figure 4.3(j) below.
Figure 4.2(j): Motor down off
72 4.2.3. Open and Close door operation
CASE 1: Open door operation
When the cab arrive at level 1 and there is request for this level, the program
will turn on the state for door open, DO. The simulation program is shown in figure
4.3(i) below.
Figure 4.2(k): Door open operate
73 Fully Open : When the door touch the sensor open, SO the motor open will turn off
and turn on the timer for a few second (10 second for this case)
before close the door. The simulation program is shown in figure
4.3(j) below.
Figure 4.2(l): Timer count
74 Door Close:
When the timer is off, the program will turn on motor to close the
door as shown in figure 4.3(k) below.
Figure 4.2(m): Door close operate
75 Fully Close: When the door touch the sensor close, the program will turn off the
motor to indicate that the system is fully close now. The simulation is
show in figure 4.3(n) below.
Figure 4.2(n): Sensor Close detected
76 4.3 Discussion
Besides the operation result, its also can be observed that there is other
information that can be find out from the operation. This information will discussed
by the topic below.
4.3.1
Sensor level circuit
The limit switch which is used as a sensor level will initially at normally
open position. After the cab arrive at certain level and touch the limit switch, it will
make the switch to be close and make the current flowing in the circuit. From the
finding, the current flow to the circuit is about 0.08 Amps with 12 Volt supply
voltage. The resistor, R is used to limit the current flow to the circuit. The resistor
value used is 100 ohm.
Power dissipating in resistor, P = I2R
= (0.08)2(100)
= 0.64 Watt
77 4.3.2
Relay action
The relay with the 24 volt action voltage is used for this project in up/down
and close door motor operation circuit. After doing some test to this relay, when the
voltage is varried from 0 volt to 24 volt voltage supply, the relay turn on when it is
supplied by plus minus 15 volt supply voltage. The relay will be in normally open as
shown in figure 4.3(a) for 0 – 14 volt supply voltage and will be close for the voltage
above 15 volt as shown in figure 4.3(b) below.
Figure 4.3(a): Normally open
Figure 4.3(b): Normally close
CHAPTER 5
CONCLUSION
5.1
CONCLUSION
From the objective of this project, we can see that the knowledge and skills
will combined together in order to complete this task. For this project, the
knowledge and skills that involve is not depending to electrical system but its also
involve the mechanical system. Without relation of each part, the system will having
the problems and this project cannot completely finished.
Besides, in this project, its also will give the challenges to students for having
the knowledge and understanding in other field besides the electrical knowledge.
Automatically, it will train the students in solving the problems eventhough it is
outside of their field of study.
79 From the objective of this project also, it will give a lot of knowledge which
is involved especially in PLC control system. Indirectly, from this project, the
students just not learn in controlling the system, but they also can learn about
programming the PLC in order to running the system. The students also can get the
creativity skills in programming the PLC so that it will running with their own way
operation.
5.2
Problems
Eventhough the system use two programmable logic controller, PLC because
of its limited input output, I/O, its still have the problem to communicate the first
PLC with the second PLC. This communication of these PLC is needed to ensure
that the system operate synchronously between the open close door operation and up
down operation.
Besides, there are over current from the sensor level circuit that make the
resistor burn after the current flow for long time. After that the signal from the
sensor cannot be detected and cannot sense the current position of the cab anymore.
When the sensor can’t be detected, the program cannot run the operation because it is
depend on the position of the cab.
The design also is the one problems that limited the space to installed extra
component like IR sensor to used as the safety. It should have the sensor to detect the
user that want to enter or go out to from tthe cab as a safety equipment so that the
user can’t be hitted by the door.
`
There is no breaking system installed for this prototype due to limited time
for finishing the project. The breaking system is used as a safety in case the cable is
broken to avoid the cab falling down with the high speed.
80 5.3
Recommendation
The efficient operation can be achieve when there is enough Input Output for
all the component used in this system. We can use the medium size of PLc to provide
enough input output, I/O.
There is a sensor that can use as a safety in the sytem so that the user will not
hitted by the door during the entering and out of the cab. The Infrared sensor can be
used as the one of the suitable sensor that can detect the movement through the cab.
We can used the fius in the circuit to avoid the the current overflow and make
resistor burn. The fius can be instaled in each circuit so that when there is a overload
current flow, it will shot the fius without effectinh other equipment.
The breaking system should be installed for one of the safety requirement to
avoid the excident when there are problems with the cable used in drive system.
Besides, for this case we can overcome the excident by make the program to give the
instruction to either stop the operation at close level to the current position.
81 REFERENCE
1) John Willey (2001). Elevator. London: John Willy & Sons. 1-8
2) Rhonda Salzmon (1998 & 1999). How Elevator Works: Martin L.
Culpepper. 1-3
3) X.Ying, Q.Zhu, H.Xu (2008). Design and Practice of an Elevator
Control System Based on PLC: IEEE, DOI 10.1109/PEITS: 94-96
4) Motion Control Engineering Incorporated (March 1999). AC Motor
Controls for Elevators: Motion Control Engineering Incorporated.
5) FESTO Didactic (2002). Programmable Logic Controller Basic Level.
(TP 301).
6) Dr. Hisham El-Sherif. Basic PLC. Industrial Park: GUC. 5-33; 2001
7) G.C Barney (1986) “ Elevator Technology”, Chister : Elis Honwood.
8) G.C Barney (1935) “ Elevator Traffic Handbook” , London : Taylor &
Francis, 2003
9) Janovsky, Lubomir “ Elevator Mechanical Design” 2nd Edition, New York :
Ellis Horwood, 1993
10) Lemony Snicket “ The Ersatz Elevator” , HarperChildren’s Audio, August
1st 2003.
82 11) http://en.wikipedia.org/wiki/Elevator (10/9/2008: 2130)
12) http://www.delorenzo.it/dl/eng/prodotti-en/automazione-en.htm
(15/9/2008: 2200). 13) http://howthingswork.virginia.edu/supplements/elevators.pdf
(15/9/2008: 2230).
14) http://www.columbia-elevator.com/info/history.html (15/9/2008: 2245).
83 APPENDIX A
Elevator motor from the Reuland company
VVVF A/C motor by Reulend Electric Company:
84 Single Speed A/C Elevator Motor (Reuland Electric company):
Specification
85 Two Speed A/C Elevator Motor (Reuland Electric company):
Specification
86 APPENDIX B
THE PROJECT MODEL
87 CONTROL PANEL
ELEVATOR CAB