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Majlesi Journal of Electrical Engineering Vol. 6, No. 2, June 2012
1
Investigation and Evaluation of Low cost Depth Sensor
System Using Pressure Sensor for Unmanned Underwater
Vehicle
Aras M.S.M
1
, Abdullah S.S
2
, Shafei S.S.
1
1- Department of Mechatronics, Faculty of Electrical Engineering, Universiti Teknikal Malaysia Melaka, Hang Tuah
Jaya, 76100 Durian Tunggal, Melaka Malaysia.
2- Department of Electric and Electronics, Malaysia-Japan International Institute of Technology, Universiti
Teknologi Malaysia, International Campus Jalan Semarak, Kuala Lumpur, Malaysia.
3- Department of Mechanical And Manufacturing Engineering, Faculty of Engineering, University Malaysia
Sarawak, Jalan Dato’ Muhammad Musa, 94300 Kota Samarahan, Sarawak.
Received X X X Revised X X X Accepted X X X
ABSTRACT:
This paper presents the investigation and evaluation of low cost depth sensor system design for unmanned underwater
vehicle (UUV) using pressure sensor. Two types of low cost pressure sensor system design are proposed for
underwater vehicle. The pressure sensors are expected to prevent buckling or damaging to the UUV. The first design
uses barometric pressure sensor, while the second design uses MPXAP which is an integrated silicon pressure sensor
on-chip signal conditioned and temperature compensated. There are two different sub model of MPXAP put forward
in this research namely, MPX4250AP and MPX5700AP. These pressure sensors are tested in three different
conditions: in water tank, lake and swimming pool to study their effect on various densities. Details of the designs are
discussed and implementations of these sensors on UUV are analyzed. Experimental results showed these pressure
sensors have different performances. Based on the analysis of the results, MPX AP sensor is more suitable to be
applied to UUV with low cost budget. For the depth from 0 to 30 meter, MPX 4250 AP is selected while MPX 5700
AP is for the range of depth up to 70 meter.
KEYWORDS: Pressure Sensor System; Unmanned Underwater Vehicle; Absolute Pressure; Barometric Pressure
Sensor; Integrated Silicon Pressure Sensor; Water Density
1. INTRODUCTION
Underwater vehicle was first developed to study
diffusion, acoustic transmission and submarine wakes.
Since then, UV technology has evolved tremendously,
applied and used in more tasks and roles and missions
constantly evolving. The development of more
advanced processing capabilities and high yield power
supplies, underwater vehicle (UV) are now accepted
and widely used for underwater mission [1]. Most of
UVs is used in commercial field for oil and gas
industry, military mission, underwater researcher and
also as a hobby. Underwater vehicle is an application
use to observe and monitor any events that occur
under water. Generally, there are three types of
underwater vehicle used for the application such as
autonomous underwater vehicle (AUV), remotely
operated vehicle (ROV), underwater gliders and
human occupied vehicle. Despite the growing use of
UV, a major problem face by the UV is still not
solved. UV tends to buck in a certain unknown under
water pressure. Normally, each underwater vehicle
operates at a depth that has been determined by the
engineers. However, by knowing the operating depth
without knowing the pressure at that determined depth
can cause buckling to UV body. By knowing the
pressure on the determined depth, underwater vehicle
can be prevented from buckling. To overcome these
problems, the underwater vehicle needs a system to
measure accurately pressure value at the determined
depth. It is also important that the system must be
designed esthetically and easy to handle. The system
accuracy and reliability are of paramount importance.
Suitable material for the UV body should also be
considered meticulously.
A suitable device or sensor should be employed on
the UV in order to know the depth that can be
tolerated by the underwater vehicle. In previous
research, there are various measurements method for
Majlesi Journal of Electrical Engineering Vol. 6, No. 2, June 2012
2
underwater application [4]-[8][11][13]-[15]. To date,
even though many researchers have successfully
developed different design/measurement method for
the UUV, the system is expensive to
develope.Therefore, the low cost pressure sensor
would offer advantage over existance measurement
method. A pressure sensor usually acts as a transducer
where it generates a signal as a function of the
pressure imposed. Pressure sensors are used for
controlling and monitoring most of the application in
a daily life. It can be used indirectly to measure
various variables such as fluid, gas flow, speed, water
level, and altitude. Regardless of the quality of the
pressure sensor, the measurement of the pressure is
influenced by environmental factors, such as wave,
tide, atmospheric pressure and sea water density [2].
By using small and low power, pressure sensor is an
attractive approach to measure waves and depth of a
small scale unmanned underwater vehicle (UUV).
The transducers are placed on the bow, port and
starboard sides of the UUV and these will be used to
determine the proximity of obstacles around
underwater vehicle (UV) [3].
In this paper, two types of low cost pressure
sensors design are proposed to obtain the pressure
value at the determined depth. The design of the depth
sensor system is focus on the underwater application.
The improvement is made for the pressure sensor
system that use barometric pressure sensor module.
Then, the second system that use MPX AP sensor is
developed. For the second system, the value is
obtained from output voltage that is proportional to
the value of pressure, and then the pressure value is
obtained from the calculation. Their accuracy and
reliability are analyzed in three types of condition
such as water tank, lake and pool on the same fixed
depth. The system with the best performance will be
chosen as sensor system for underwater vehicle. This
paper is organized as follows; section 2 presents the
theoretical about pressure sensor; section 3 describes
system methodology. Section 4 and Section 5
illustrates the field testing results. Finally, section 6 is
a final remark.
2. THEORETICAL
The definition for pressure is difference when it’s
come to water pressure. This is because the pressure
of water should consider the depth of water and its
density [4]. Equation 1is the formula for pressure
measurements which is;
P = ρgh (1)
Where;
P is a pressure, ρ is a density of the water, g is gravity,
and h is height of the fluid/depth of water.
Since ρ and g are constants, the pressure of a fluid
is directly proportional to the depth of the fluid. In
context of this project, depending on the structural
strength of a submarine, it can only submerge safely
to certain depth in the ocean. The submarine that has
been built in a wrong shape would collapse when it
submerges in the deep water. Further, the high
pressure of the water would destroy the submarine
[5]. In order to prove the relation between the
pressure and depth of water, there are few theories
that state the relationship between the pressure and
depth of the water. Figure 1 shows one of the example
of relationship between the pressure and depth; the
pressure increases when the depth is deeper. This
shows that the range of the diverse rates of pressure in
water is various at different depth.
Fig. 1: Relation between Pressure and Depth [5]
Water density is a part of physical characteristic of
water that depends on surrounding temperature and
atmospheric pressure. The density of lake water is
said to be higher than the density of pool water due to
the existence of impurities in lake water. The pool
water is fresh and clean, thus giving a lower density
and lead to low pressure compares to lake water. The
density for pure water is 1000 kg/m
3
and sea water
has the density of 1027 kg/m
3
[6]. However, the
temperature is said to have great effect on the density
[6]. Figure 2 shows that the pressure increases
proportional to the temperature.
Majlesi Journal of Electrical Engineering Vol. 6, No. 2, June 2012
3
Fig. 2: Pressure versus Temperature [6]
3. METHODOLOGY
This project consists of two major parts which are
the hardware part and the software part. The hardware
parts involve the fabrication of two pressure sensor
systems which consist of electronic board and their
casings. Figure 3 shows the process requires to
accomplish this project. In the first phase, the
improvement of the first pressure sensor is done by
providing an external switching device to the system.
Meanwhile, an integrated silicon sensor is fabricated
for the second pressure system. The second phase is
the software development for the pressure sensor
system to display the pressure value on the LCD. At
this stage, a suitable casing is chosen to protect the
system, thus it is water resistant. The final stage
involves analyses of the data pressure obtain from the
experiment of both pressure sensor systems at three
different places which are in water tank at laboratory,
at UTeM’s lake, and at swimming pool.
Fig. 3: Flow chart of project
3.1 Hardware Constructions
Figure 4 shows the details of the hardware process
for this research. A thorough research on the
suitability of the components for pressure sensor
system is done. Then, the design of the hardware part
is reviewed before continue with procuring of all
other necessary components. The hardware parts
include the electronic components on the board and
the casing for the pressure sensor system. The
functional circuit board consists of two different
pressure sensor systems, which is barometric pressure
sensor and MPXAP. For the first system, the electrical
part consists of microcontroller 16F876A, a
barometric pressure sensor, compass module,
capacitive sensor, voltage regulation, and LCD. PIC
board is assembled with the barometric pressure
sensor and compass module as the main controller for
detecting the pressure surrounding the UV vehicle.
Since this project is a combination of the existed
technologies, the assembly process is very important
part in order to make sure the pressure sensor system
Majlesi Journal of Electrical Engineering Vol. 6, No. 2, June 2012
4
for this project is well functioning. Meanwhile for the
second system, it consists of integrated silicon
pressure sensor, filtering circuit, and also op- amp
circuit. First, an integrated silicon pressure system is
fabricated. Then, the components are soldered on the
board.
After the assembly process, the circuit connection
for both systems is tested by checking its continuity
before placing the systems inside the casing. For the
first pressure sensor system this procedure must be
done to make sure the pressure sensor is functioning
and in contact to the PIC. It must also be ensured that
the casing used is suitable and able to protect the
system while it is in the water. The details of the
electronic components connection use in this project
will be explained in next section.
Fig. 4: flow of the hardware process
3.2 Electrical Component
The main board used for both pressure sensors are
printed circuit board. The control circuit board
consists of a functional circuit, PIC 16F876A and
LCD. The sensor use to read the pressure value is
barometric pressure sensor. Figure 5 shows the
SCP1000 input pins where SCK (SPI clock input) is
connected to the RC3 and MOSI (SPI data input) to
the RC4. Figure 6 shows that the signal between
sensor and PIC 16F876A is converted to the voltage
level. Since this sensor requires 3.3V, the pins at
sensor are connected to other components to regulate
the voltage for the suitable supply required.
Fig. 5: Connection of sensor to PIC
Fig. 6: Component to Regulate the Require Voltage
Then the LCD and switching is constructed on the
external board and connects to the main board by
using bus cable. Since the LCD is connected on the
external board, components are connected using
jumper with header pin.
3.3 PCB Design for Depth Sensor
Next step is PCB design process. PCB design
process for the pressure sensor consists of four
important stages. In fabrication process,extra
precaution has to be taken since the design process is
very sensitive to the tolerance in the dimension. The
first stage is to prepare the master layout and followed
by creating the photoresist pattern, etching and
soldering.The mark layout is a scaled conductor
pattern as shown in Figure 7. Once the proteus
software had been optimized and the exact patterns are
obtained then the file is translated to form the layout
of design.
(a) (b)
Fig. 7: (a)Te mark layout for pressure sensor;
(b) PCB after etching process
Majlesi Journal of Electrical Engineering Vol. 6, No. 2, June 2012
5
Fig. 8: Complete circuit
Finally, the pressure sensor is soldered on the PCB as
shown in Figure 8. The continuities are checked using
multimeters to ensure the complete and good flow of
signal in the design circuit. Once the continuity test is
completed, the pressure sensor now ready to measure
depth of water. This is second sensor pcb board
design.
3.4 Software Development
Figure 9 shows the flowchart of the operation for
the pressure sensor system one. This system is
operated once the switch is on and it displays the value
based on the mode switch press. Each switch
represents the sensor use in the system.
Fig. 9: the flow of software operation
The sensor system two not used PIC programming
(software development). Only measurement on output
pin so that the output obtained in Volts unit. So,
needed to convert to depth using converter in another
section.
4. EXPERIMENT
Figure 10 shows the pressure sensor design in this
research which is ready to be tested. The method to
test the pressure sensor is developed. First experiment
was performed in the pool filled with tap water with a
depth of about 1 m. The second test was performed in
the lake which has a depth of about 10 m. The last test
was performed in the pool with the depth of about
10m. For the first experiment the depth is limited
because of the height of water tank is only about 1 m,
thus the range to determine the pressure is from 0 to 1
m. However, in the second test the lake has depth of
about 10 m and the range of depth is from 0 to 10 m.
The same case happens for the last test in the pool
where the depth range is from 0 to 10m. The long and
adjustable pipe is used to submerge the pressure
sensor systems with casing into the water in order to
obtain the deepest rate of water.
(a) System 1: Barometric Pressure Sensor
(b) System 2: Integrated Silicon Pressure Sensor
Fig. 10: Pressure Sensor design for unmanned
underwater vehicle
4.1 Testing in the Water Tank at Underwater
Laboratory
The first test for two pressure sensor was
performed by submerging underwater in the water
tank to test the pressure rate. Figure 11 shows the
experiment carried out at the water tank with the
increasing depth of tap water. The results of two
pressure sensor systems are recorded in two different
tables that include range from 0 to 1m. The rate was
increased 0.05 m for each increment of depth. The test
of two pressure sensor systems was done three times
to get more accurate results. The results are plotted in
the graph of pressure (kPa) versus depth (cm) for
system one and graph of voltage (V) versus depth (m)
for system two.
Majlesi Journal of Electrical Engineering Vol. 6, No. 2, June 2012
6
Fig. 11: The experiment conducted in water tank
4.2 Testing in the UTeM’s Lake
The second test for the pressure sensor system was
performed in the lake as shown in Figure 12. This
second test involved two pressure sensor systems as
the main tools. This second place was chosen to
investigate whether the lake water and its depth affect
the pressure sensor performance. The same method
was done at water tank to obtain the result which is
the pressure sensor system with casing was
submerging into the lake water. The results of two
pressure sensor systems are recorded in two different
tables. The results are recorded from range 0 to 10 m
depth with each increment of 1m. The range of depth
is bigger because the lake depth deeper than the water
tank. The test was repeated three times to get more
accurate results. The results was plotted in the graph
of pressure (kPa) versus depth (m) for first system and
voltage (V) versus depth (m) is plotted for second
system.
Fig. 12: The experiment conducted in lake
4.2 Testing at swimming Pool
The third experiment was done in the pool as
shown in Figure 13. The aim of the third experiment is
to obtain the pressure value as compare to the previous
experiments since the depth of the previous place is
limited. The same method was applied at swimming
pool where the pressure sensor system with casing was
submerged into the water. The results for two pressure
sensor were recorded in two different tables. The
results were recorded from range 0 to 10m depth with
each increment of 20 cm since the range was also
increase compare to the previous experiment. The
pressure value for the two pressure sensor systems was
recorded in the tables. The test was repeated three
times to get the accurate result and the result also was
plotted in the graph of pressure (kPa) versus depth (m)
for system one and voltage (V) versus depth (m) is
plotted for system two.
Fig. 13: The experiment conducted at pool
5. RESULT
5.1 Experimental Results
From the result recorded, the average of output
pressure and voltage of two systems for each depth of
water is calculated by using the below equations
accordingly;
5.1.1 System 1
Average Pressure (kPa) = (2)
Example of calculation;
At depth = 9 m, output pressure for system 1 is;
Pressure1 = 102.940 kPa,
Pressure2 = 103.031 kPa,
Pressure3 = 102.980 kPa
Pave =
= 102.984 kPa
5.1.2 System 2
Average Voltage (V) = (3)
Example of calculation;
At depth = 9 m, output voltage for system 2 is;
Voltage 1 = 0.753 V, Voltage 2 = 0.750 V, Voltage
3 = 0.748 V
Average Voltage (V) =
= 0.750 V
Majlesi Journal of Electrical Engineering Vol. 6, No. 2, June 2012
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From the results obtained, the graph of pressure
versus depth for System 1 and System 2 were plotted.
Figure 14 shows the graph value of pressure on three
different types of water for system 1. While for the
Figure 15 shows the graph value of pressure on three
different types of water of pressure sensor for system
two.
Fig. 14: Graph of Pressure at Three Difference Types
of Water for System 1
Fig. 15: Graph of Pressure at Three Difference Types
of Water for System 2
5.1.3 Performance of Pressure System
To evaluate performance of the pressure system in
this reseach, error is defined as follows,
Error= (4)
% of error = Error x (100/100)
The theoretical value for pressure can be calculated or
obtained from the software that can be used to convert
the depth of water into pressure value. Figure 16 show
the software used to obtain the theory value for
pressure at the given depth.
Fig. 16: Pressure Converter
Example of calculation to obtain pressure value at
given depth is shown below;
For depth, h = 5m, by using eq (1) yield
g = 9.81
ρ = 1000 kg/m
3
P = (1000 kg/m
3
) (9.81) (5)
P = 49.05 kPa
In order to get the actual value of pressure from the
experiment, the output values that obtain from these
two systems were set to be bonding equation or for the
calibration.
5.2 Pressure Sensor System 1 (Barometric
Pressure Sensor)
The first value obtained from pressure sensor system
is set to be as reference value. The calculation for each
pressure at different depth is continued by using the
equation (4). Each of the value for the theory and
calculation of the pressure from the experiment for the
system one was recorded in the Figure 14 and Figure
15. In graph for the Figure 14 and 15, the equation
used to obtain the error between theory and
calculation given by:
Error= (5)
% of error = Error x (100/100)
Calculation;
Taking the maximum error from the graph of theory
and calculation for experiment done by referring to
the graph;
1) Water tank
% of error = Error x (100/100)
= x (100/100)
= ±38.38%
Majlesi Journal of Electrical Engineering Vol. 6, No. 2, June 2012
8
2) Lake
% of error = Error x (100/100)
= x (100/100)
= ±55.84%
3) Pool
% of error = Error x (100/100)
= x (100/100)
= ±56.82%
5.3 Pressure Sensor System 2 (Integrated
Silicon Pressure Sensor)
5.3.1 MPX 4250 AP
Experiment 1 held on swimming pool with depth up
to 12.5 feet. Result of this experiment as shown in
Table 1. Three reading measuring of output stated in
Table 1. Figure 17 is shows the output pressure
(voltage) plotted in graph.
Fig. 17: Output vs absolute pressure
Table 1. The result of experiment 2
Depth
(feet)
Depth
(meter)
Depth
(cm)
Output
reading
1 (V)
Output
reading
2 (V)
Output
reading 3
(V)
0 0 0 1.622 1.614 1.593
1 0.3048 30.48 1.683 1.671 1.648
2 0.6096 60.96 1.731 1.716 1.694
3 0.9144 91.44 1.779 1.758 1.735
4 1.2192 121.92 1.825 1.802 1.774
5 1.524 152.4 1.869 1.846 1.826
6 1.8288 182.88 1.922 1.896 1.87
7 2.1336 213.36 1.973 1.944 1.886
8 2.4384 243.84 2.024 1.994 1.938
9 2.7432 274.32 2.054 2.03 1.983
10 3.048 304.8 2.122 2.085 2.032
11 3.3528 335.28 2.168 2.156 2.097
12 3.6576 365.76 2.223 2.207 2.174
Fig. 18: Outputs graph of three reading
From Figure 18, we can see the output of pressure
sensor linearly proportional to the depth of water. The
deep the pressure sensor submerges into underwater,
the pressure will be increasing until it saturated when
the pressure sensor limit for the depth up to 25.5 meter.
The three reading of output almost got same pattern
that is linearly output. Mention earlier, we assumed
when the output 1.622 V, the depth will be on surface
(0m) and when the output is 2.223 V the depth is
3.66m. It is almost similar with our depth setting.
From Table 2 the setting depth between 1.622 V and
2.223 V is 3.2 meter. So, the error is up 12 %
equivalent to 46 cm. As the conclusion, this pressure
sensor can be applied in underwater vehicle to
determine the depth of water based on changes in
pressure. The water pressure changes are linearly
proportional to the depth of water. The pressure will be
increase as the depth of water increase. The change in
depth (or weight of the water) will influence the
pressure as defined in equation 4 where p is pressure, w
is weight of the fluid and h is the depth.
Table 2. Data sheet of pressure sensor
Pressure (kPa) Meter (m) Typical (V)
10 1.02 0.3
20 2.04 0.3
30 3.06 0.4
40 4.08 0.6
50 5.1 0.8
60 6.12 1
70 7.14 1.2
80 8.16 1.4
90 9.18 1.6
100 10.2 1.8
110 11.22 2
120 12.24 2.2
5.3.2 MPX 5700AP
In the next experiment, we change our pressure
sensor to MPX 5700 AP. The circuit for MPX 5700 AP
similar with MPX 4250 A. From data sheet for
MPX4250AP every 25kPa give an output of 0.4V
Majlesi Journal of Electrical Engineering Vol. 6, No. 2, June 2012
9
while MPX5700AP that every 25kPa give an output of
0.25V. MPX 5700 can measure up to 700 kPa
equivalent to 71.38 meter deep as shown in Figure 19.
Fig. 19: Output vs absolute pressure
Table 3. The result of experiment 3
Depth (cm) output
1
output
2
output
3
Depth (cm)
from
datasheet
0 0.737 0.736 0.728 4.748
5 0.740 0.740 0.731 4.767
10 0.743 0.743 0.734 4.786
15 0.746 0.746 0.737 4.805
20 0.749 0.749 0.740 4.824
25 0.752 0.752 0.743 4.843
30 0.755 0.755 0.746 4.862
35 0.758 0.758 0.749 4.881
40 0.761 0.761 0.752 4.900
45 0.764 0.764 0.755 4.919
50 0.767 0.767 0.758 4.938
55 0.770 0.770 0.761 4.957
60 0.773 0.773 0.764 4.976
Fig. 20: output graph of three reading from three
experiments
From Figure 20 we can see the output of pressure
sensor also linearly proportional to the depth of water.
The deep the pressure sensor submerges into
underwater the pressure will be increasing until it
saturated when the pressure sensor limit for the depth
up to 70 meter. The three reading of output almost got
same pattern that is linearly output. Mention earlier, we
assumed when the output 0.737 V, the depth will be on
surface (0m) and when the output is 0.773 V the depth
is 60 cm. From Table 2 the setting depth between
0.737 V and 0.773 V is 22.8 cm. So the error is 60 %.
As the conclusion, this pressure sensor cannot suitable
to apply in our underwater vehicle to determine the
depth of water based on changes in pressure because
this pressure sensor MPX5700AP give an output of
0.25V every 25kPa. So it is not suitable for shorter
depth. It is suitable for more deep up to 70 meters.
Figure 4 is shows a experiments set up for pressure
sensor, (a) is MPX 4250 A and (b) is MPX 5700 AP.
The outputs obtain from the experiment done for
the second pressure sensor system in three difference
types of water was in voltage value. In order to get the
value of pressure, the characteristic graph was plotted
by using excel based on the given specification of the
MPX5700AP sensor. Figure 21 shows the plotted
characteristic graph of MPX5700 AP.
Fig. 21: Characteristic Graph of MPX5700AP
The equation was obtained from this graph to find
the pressure value for the experiment done at the three
different types of water. The equation is;
The general equation, y = mx + c (5)
Equation obtained, y = 0.0055x + 0.265
Calculation;
At depth = 0 m;
y = 0.0055x + 0.265,
y = 0.748 V.
Output voltage obtained from experiment, the value
obtained for the first calculation was set to be
reference value.
Majlesi Journal of Electrical Engineering Vol. 6, No. 2, June 2012
10
x = Pressure value (kPa)
Pressure (kPa) =
=
= 87.818 kPa is equal to reference pressure
After the value for each pressure for the experiment
done was obtain, the actual value for pressure for
each depth was then calculated by using the equation
(6).
By referring to the eq. (4)
% of error = Error x (100/100)
Calculation;
1) Water tank
% of error = Error x (100/100)
= x (100/100)
= ±9.40%
2) Lake; The value of mode of error in the graph is
consider compare to maximum value
% of error = Error x (100/100)
= x (100/100)
= ±23.59
3) Swimming Pool
% of error = Error x (100/100)
= x (100/100)
= ±28.31%
From the data obtained, the pressure will always
increase when collaboration with increasing water in
depth. From the graph plotted for system one and
system two, both system showed the increment value
of pressure for each increment of depth. The system 1
shows that the pressure value at water tank and pool
has the higher value compare to the pressure value at
lake. System two shows that the value of pressure at
lake is higher than the value of pressure at water tank
and pool.
However for the both system, its shows that the
pressure value for water tank and pool at the same
depth is almost the same. These according to the theory
of water pressure which the pressure is increase when
the depth of water is increase and the pressure is also
affected by the water density. The pressure for water
tank and pool is almost the same since both of it is
fresh water. The lake water should have high water
density based on the theory of water because of its
impurities. Based on the theory, the system two give
the accurate result compare to the system one since its
shows that lake has high pressure compare to water
tank and pool.
Calculation of percentage of error to see
performance of the two pressure sensor also done by
taking the maximum error from the plotted graph in
those three different types of water. By the calculation
done, the result clearly shows that value of percentage
error for system one is higher which is equal ±38.38%
at water tank compare to system two that equal to
±9.40%. For the second percentage error value at lake
system one equal to ±55.84%, while system two equal
to ±23.59%. For the last place, at pool the percentage
of error for system one is equal ±56.82%, while for
system two is equal ±28.31%.
Fig. 22: Comparison of three types of pressure sensor
6. CONCLUSION
The experiments carried out for the various types of
pressure sensors in 3 type of water (Pool, lake and lab
tank) and different water depth showed:
1.The appropriate pressure for water vehicle to move
without buckling
2.The surrounding pressure can be determined where
the UV can be safely maneuvered
3.The appropriate pressure sensor system for under
water activity is MPX AP. It is reliable, accurate and it
can be used as a depth sensor as well. The margin of
error is about 4 kPa
4.MPX AP matches most of the application for UV
since it has a wide range of pressure measurements
Majlesi Journal of Electrical Engineering Vol. 6, No. 2, June 2012
11
5.Water in tank and water in the pool do not exhibit the
same characteristics namely: same pressure, and
temperature which affect its density.
After completing this project, this project can help
in research activity to determining the appropriate
pressure to move the underwater vehicle in the water.
This research also has many advantages that can help to
determine the level of underwater vehicle by referring
to the surrounding pressure of the underwater vehicle.
By referring to the objective of this project, the selected
pressure sensor system for underwater vehicle in this
project is pressure sensor system that use MPX AP
sensor. This sensor shows a good performance in
measuring the pressure value at underwater. Other than
that, this sensor also is able to be use as depth sensor
that matches most of the application for underwater
vehicle since it has a wide range of pressure
measurements.
The selected pressure sensor system also based on
the performance shows in measuring the pressure value
at underwater. The analysis shows that this system is
accurate in measuring the pressure at underwater since
it is approximate the theory value of water pressure.
The error shows in measurement for system two only ±
4 kPa (maximum error) compare to system one which
is ± 5 kPa (maximum error). Other than that, from
Percentage of error obtained, the results clearly shows
that value of percentage error for system 1 is higher
which is equal ±56.82%, while for system 2 is equal
±28.31%.
This system also shows that the pressure value on
the lake water is higher than at water tank and pool due
to its density of water. Other than that, water density
also depends on temperature of water. Normally lake
water gets denser as the temperature goes down
compare to the water tank and pool that has higher
temperature. This is happen because the lake water is
in open area and it does affected by nature element.
7. RECOMMENDATION
UV can use the pressure sensor to measure the
appropriate depth and conditions (water pressure,
temperature and salinity) where the UV can safely be
utilized without buckling. The improvement in the
design, structure and components used for UV can
vastly benefit the military. A Vibration SENSOR, can
be installed in the UV as an added security.
Although the underwater vehicle can use the
pressure sensor in order to prevent buckling and
knowing its operating pressure, the improvement to this
underwater vehicle can give many benefit to many
parties such as military field for used to tracking any
kind activities happen in the water. In order to improve
this sensor performance, vibration sensor can be
implementing to the system. The operation of the
vibration sensor is should be dividing by two sensing
elements, which are first sense the vibration or unusual
vibration situation around the underwater vehicle. This
sensor can be categorized as an alarm function for the
selected sensor system for the underwater vehicle. A
vibrator sensor should be synchronized with the
pressure sensor system that can generate the warning
signal, then able to vibrate and send the information
once the underwater vehicle has undergo the high limit
of pressure.
ACKNOWLEDGEMENT
Special appreciation and gratitude to honorable
University (UniversitiTeknikal Malaysia Melaka,
UTeM and UniversitiTeknologi Malaysia, UTM)
especially to the both Faculty of Electrical Engineering
for providing the financial as well as moral support to
complete this project successfully.
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