8/10/2019 Design and Modeling of Tank Control for Fluid Circulation System Using Simulink - TJ220.N68 2007 - Noorul Mannan Shaik Alawdeen http://slidepdf.com/reader/full/design-and-modeling-of-tank-control-for-fluid-circulation-system-using-simulink 1/26 UNIVERSITI TEKNIK L M L YSI MEL K Design and Modeling of Tank Control for Fluid Circulation ystem Using SIMULINK Thesis submitted in accordance wit the partial nquhments of the Universiti Teknikal Malaysia Melaka for the Bachelor of M anufeg Engineering Robotic and Automation) NOORUL M NN N BIN SH IK L WDEEN Faculty of Manufacturing Engineering May 2007
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Design and Modeling of Tank Control for Fluid Circulation System Using Simulink - TJ220.N68 2007 - Noorul Mannan Shaik Alawdeen
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8/10/2019 Design and Modeling of Tank Control for Fluid Circulation System Using Simulink - TJ220.N68 2007 - Noorul Mannan Shaik Alawdeen
Tank level control is one of the important system which been used widely in industrynowadays. This control system keeps developing to replace the ordinary system which
applies mechanical functions in controlling in order to improve the system reliability.
There re many applications in industries that using this system such s water dam
water treatment system industrialtank control and also boiler. In order to develop a
successful tank fluid level control system ll understanding on the functions and
principles of the system is required. In this project MatLab Simulink willbe used s a
main platform in developing the simulation of the exact control system for an industrial
fluid circulation system. The system willbe tested to gain the most su itable and desired
control function. The end result of this project willbe a smooth and low error rate
control system for controlling the tank fluid level of the circulation system.
8/10/2019 Design and Modeling of Tank Control for Fluid Circulation System Using Simulink - TJ220.N68 2007 - Noorul Mannan Shaik Alawdeen
According to Wikipedia online dictionary [I] control system is a device or set of devicesto manage command direct or regulate the behavior of other devices or systems.
Control systems are an integral part of modem society. There re a lot of the applications
that using the control syst m nowadays. From as simple application such s air-conditioner
washing machine and microwave to complicated application such s robotdevelopment self-guided vehicle and guided missile launcher were using the control
system. There are a lot of examples which using control system in human daily life.
Control system also exists naturally in the world. An example of natural control system is
pancreas in human body which regulates the human blood sugar level. Another
example of the natural control system are photosynthesis process done by trees and
plants.
A control system consists of subsystem and proc ses assembled for the purpose of
controlling the outputs of the processes [2]. For example an air conditioner produces
more cool air s a result of room temperature increase. To determine the m m emperatwe
the air conditioner use thermost t to measure the level of the tern . The thermostat is
called the subsystem in this process. The subsystem will be the input to system and thecontrol system will provide an appropriate output or response for the given input or
stimulus. This process is shown in Figure 2.1 [2].
Figure 2.1 Simplified description of a control system
8/10/2019 Design and Modeling of Tank Control for Fluid Circulation System Using Simulink - TJ220.N68 2007 - Noorul Mannan Shaik Alawdeen
commanded direction. If wind forces the antenna from its commanded position, or if noise
enters internally, the syst m must be able to deted the disturbance and c o r n he antenna s
position Obviously, the system s input will not change to make cormtion Consequently, the
system itself must measure the amount that the disturbance has repositioned the antenna
and then return the antenna to the position commanded by the input.
As stated earlier, a control system provides an output or response for a given input or
stimulus. The input represents a desired response, and the output is the actual response.For example, when the fourth-floor button of an elevator is pushed on the ground floor,
the elevator rises to the fourth-floor with a speed and floor-leveling accuracy designed for
passenger comfort as shown in Figure 2.2 [2] The push of the fourth-floor button is the
input and is represented by a step command. Note that in the interest of passenger
comfort, not to mention the limited power available, we would not want the elevator
to mimic the suddenness of the input. The input represents what we would like the
output to be fter th elevator has stopped th elevator itself follows th displacement describes
by the curve marked elevator response.
Figure 2 2: Elevator response
Two factors make the output different fiom the input. First, compare the instantaneous
change of the input against the gradual change of the output in Figure 2.2. Physical entities
cannot change their st te (such as position or velocity) instantaneously. The st te changes
8/10/2019 Design and Modeling of Tank Control for Fluid Circulation System Using Simulink - TJ220.N68 2007 - Noorul Mannan Shaik Alawdeen
through a path that is related to the physical device and the way it acquires or dissipates
energy Thus, the elevator undergoesa gradual change as it rises h m he irst floor to the f o
floor. This p rt ofthe mqwnse s called reqxme
After the transient response, a physical system approaches its steady-state response, which
is its approximation to the commanded or desired response. For the elevator example, this
r spons occurs when lhe elevator rtx hes th fanth floor. The accuracy of the elevator s
leveling with the floor is a second factor that could make the output different from the
input. We call this difference, as shown in Figure 2.2 steady-state error. Steady-state error
need not exist only in defective control systems. Often steadystate error is inherent in the
designed system, and the control systems engineer determines whether or not that the error
leads to significant degradation of system functions.
2 2 1 Open Loop nd losed Loop System
An open-loop system is a direct output system, which did not compensate to the
disturbance applied to the system. It starts with a subsystem called an input transducer,
which converts the form of the input to that used by the controller. The controller will
provides an output which also called the controlled variable. The limitation of the open-
loop system is that it could not make appropriate decision if disturbance wereadded to the controller s driving signal. Diagram of open-loop system is s own in Figure 2.3
Figure 2.3: Open Loop system
8/10/2019 Design and Modeling of Tank Control for Fluid Circulation System Using Simulink - TJ220.N68 2007 - Noorul Mannan Shaik Alawdeen
The first summing junction algebraically adds the signal from the input to the signal
from the output, which arrives via the feedback path, the return path from the output to
the summing junction. in Figure 2.4, the output signal is subtracted from the input
signal. The result is generally called the actuating signal. However, in systems where
both the input and output transducers have unity gain (that is, the transducer amplifies its
input by l , the actuating signal s value is equal to the actual difference between the
input and the output. Under this condition, the actuating signal is called the error.
The closed-loop system compensates for the disturbances by measuring the output
response, feeding that measurement back through a feedback path, and comparing that
response to the input at the summing junction. If there is any difference between the two
responses, the system drives the plant, via the actuating signal, to make a correction. If
there is no difference, the system does not drive the plant, since the plant s response is
already the desired response.
Closed-loop systems, then, have the obvious advantage of greater accuracy than open
loop systems. They are less sensitive to noise, disturbances, and changes in the
environment. Transient response and steady-state error can be controlled more
conveniently and with greater flexibility in closed-loop systems, often by a simple
adjustment of gain (amplification) in the loop and sometimes by redesigning the
controller. Redesign means compensating the system and to the resulting hardware as acompensator. On the other hand, closed-loop systems are more complex and expensive
than open-loop systems. standard, open-loop toaster serves s an example: it is simple
and inexpensive. closed-loop toaster oven is more complex and more expensive since
it has to measure both color (through light reflectivity) and humidity inside the toaster
oven.
8/10/2019 Design and Modeling of Tank Control for Fluid Circulation System Using Simulink - TJ220.N68 2007 - Noorul Mannan Shaik Alawdeen
one should not bother with it. However thef zzy logic paradigm may provide scalability
for large control systems where conventional methods become unwieldy or costly to
derive. Fuzzy electronics is an electronic technology that uses fuzzy logic instead of
the two value logic more commonly usedin digital electronics.
So simply we can say that systems that perf the previously d e s c r i i measurement and
correction are called closed-loop or feedback control systems. Systems that do not have this
p.operty of measurement and mmxtion are called open-loop systems
2 3 evel and low ontrol System
The liquid level control system is a pressure responsive element comprises a valve
including a pair of spaced moveable diaphragm members[4]-of a kind non-permeable to
fluids-associated for coordinated movement and a valve body cooperating with
respective ones of said associated diaphragm members to define first and second pressure
sensing cavities and cooperating with both of said diaphragm members to define a third
valve cavity and in which said first and second pressure sensing cavitiesare coupled to
respectively a reference pressuresource and said fluid amplifier means for displacing said
associated diaphragm members between said spaced positions in accordance with the
relative signal pressures introduced into said first and second pressure sensing cavities andhrther in which said pressure responsive element includesan inlet communicating with
said third valve cavity when said associated diaphragmmembers ~ in either of saidsp ced
positions and an outlet coupled to said third valve cavity and having a valve seat portion
spaced from said associated diaphragm memberswhen said members r n said fkd position
to pennit flow between said inletand outlet o f said third va lve cavity and in which one o f
said associated diaphragm members engages said valve seat portion of said third cavity
upon movement of said associated diaphragm members to said second position to close
said outlet of said third valvecavity said inlet and out of said thii valve c vity being
mupled in s ri s with t least one of said inlet and outlet of said reservoir means for
8/10/2019 Design and Modeling of Tank Control for Fluid Circulation System Using Simulink - TJ220.N68 2007 - Noorul Mannan Shaik Alawdeen
regulating flow through said one of said inlet and outlet of said reservoir meansto
maintain the liquid within said reservoir means t a desired level.
liquid level sensing system comprising a reservoir means having an inlet and an outlet
and adapted for receiving a quantity of liquid therein flow control means including a
pressure responsive element for regulating flow at least one of said inlet and outlet of
said reservoir means accordingto a sensed pl ssur condition; nd fluid amplifier means having
serially aligned inlet interaction and outlet zones comprisingan inlet flow channel
positioned above the desired liquid sensing level in said reservoir with the terminus of said
flow channel approximately contiguous said sensing leveland oriented for directing a liquid
flow transversely to the surface of the liquid in said reservoir meansnd htth r comprising
outlet means sep r ted h m aid inlet flow channel bythe free space o f said interaction
region and coupled to said flow control means the liquid from said inlet flow
channel im pinging on said outlet me ans with a first predetermined pressure when
the level in said reservoir is below said sensing level and second substantially lesser valuewhen the liquid in said reservoir moves above said sensing level for actuating said flow
control means.
Level control system comprising; reservoir means having an inlet and outlet andadapted
for receiving a quantity of liquid therein fluid amplifier means comprising an inlet for
developing a fluid power stream and an outlet spaced from said inlet said amplifier
means being constructed and arranged for developing at said outlet a fluid pressure
signal of a first predetermined magnitude when the liquid level in said reservoir is
displaced from a desired level and of a second substantially different
magnitude when said liquid is t said desired level and a valve means comprising a pair
of spaced diaphragm members of a kind non-permeable to fluidsassociated for
coordinated movement between a pair of spaced positions resilient means for normally
biasing one of said diaphragm members toward one of said spaced positions and a valvebody cooperatingwit ve ones of said diaphragm r n e m to define h t nd se ond
closed signal pressure sensing cavities and cooperating withboth of said diaphragm
8/10/2019 Design and Modeling of Tank Control for Fluid Circulation System Using Simulink - TJ220.N68 2007 - Noorul Mannan Shaik Alawdeen
members to define a third valve cavity and in which saidfirst and second pressure sensing
cav ities are coupled respectively to a reference pressure source and the outlet of
said fluid amplifierme ns ibr displacing said associateddi phr gm members etween said
sp ced positions in accordance with the relative signal pressures introduced into said first
and second pressure sensing cavities and M h e r comprising an inlet communicating with
said third valve cavity when said associated diaphragm membersre in either of said
spaced positions and an outlet coupledto said third valve cavity having valvese t
pottion sp ced f b m said associateddiaphragm memberswh n said members re in said fast
position to permit flow between said inlet and outlet of saidthii valve c vity and in whichone of saidassociated diaphragm mem ers eng ges said valve seat portion of said outlet of
said third cavity upon movement of said associated diaphragm members to said second
position to close said outlet of said third valvecavity s id inletand outlet of said third v lve
c vity eing coupled in series with t least one of said inlet and outlet of said reservoir
means to maintain the liquid within said reservoir means at a desired level.
8/10/2019 Design and Modeling of Tank Control for Fluid Circulation System Using Simulink - TJ220.N68 2007 - Noorul Mannan Shaik Alawdeen
As can seen in many of nowadays conventional system the mechanical input device that
been used can cause a lot of problem because of the wear that will occur. Example of the
mechanical input device is floating limit switch. ear is defined as the progressive loss
or removal of material from a surface [6] To avoid h m his kind of problem to occur
frequently the input device that more reliable can be replace such s ultrasonic sensor
Ultrasonic transmitter is on types of sensor which will give an input to the system.
Sensor is the first link between the typical automated system and the conventional
process [7].The transmitter emits an ultrasonic wave and determines the propagation
time of the signal reflected at a surface. On the basis of this time the device calculates
the distance between the lower edge of the sensor and the surface s illustrated in Figure2 8 [8] The influence of the sound velocity dependent on the surrounding atmosphere is
automatically compensated for by entering specific values and measurement of the
ambient temperature by the transmitter. If the distance between the lower edge of the
sensor and the bottom of a t nk is known the device is able to indicate the filling level
or if the tank geometry is known the volume still inside the tank can be indicated.
Various disturbance echo filters even enable use in containers with built-in fixtures
generating a disturbance echo.
8/10/2019 Design and Modeling of Tank Control for Fluid Circulation System Using Simulink - TJ220.N68 2007 - Noorul Mannan Shaik Alawdeen