An automatic wave probe reference setting mechanism

IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
__________________________________________________________________________________________
Volume: 02 Issue: 09 | Sep-2013, Available @ http://www.ijret.org 515
AN AUTOMATIC WAVE PROBE REFERENCE SETTING MECHANISM
IN A HIGH SPEED TOWING TANK
A.Adithya Kashyap1
, B.Prasad Rao2
, Y.Srinivasa Rao3
, K.Srinivasa Rao4
1
Assistant Professor, Dept of EIE, VNRVJIET, Hyderabad, India.
2
Research Scholar, 3&4
Professor, Dept of Instrument Technology, AU College of Engineering, Vishakhapatnam, India
kashyapadithya@yahoo.co.in
Abstract
The wave generation system in a High Speed Towing Tank (HSTT) generates regular and irregular waves to simulate wave condition
during ship model testing. A wave probe is used to measure the height of waves generated by the wave generation system which is
placed at the centre of the towing tank from the wave generation system. Generally the initial wave height reference (zero-point) at no
wave condition is set manually and it is difficult to set reference accurately and the procedure is time consuming. The work aims at
development of an automatic mechanism for adjustment of zero point in HSTT. The intended system enables remote monitoring and
setting wave probe height reference with better accuracy minimizing human intervention. The prototype results confirmed the efficacy
of the proposed mechanism.
Keywords: Towing Tank, Wave probe, Wave generating system.
--------------------------------------------------------------------***----------------------------------------------------------------------
1. INTRODUCTION
The High Speed Towing Tank (HSTT) is a test facility for
carrying out model testing under various conditions including
simulated sea conditions for determining the performance of
the surface and submerged bodies and evaluation of their
hydrodynamic characteristics.
The dimensions of HSTT is considered as 500m x 8m x 8m
(LxBxD). The facility has a high speed towing carriage which
runs on parallel rails upto a maximum speed of 20m/sec with
an accuracy of 0.1% of set speed. HSTT features a dual flap
type wave generator capable of generating regular and
irregular waves (unidirectional) up to wave height of 0.5m.
The waves generated by the wave generation system are
measured using a conductive type wave gauge (wave probe).
The wave probe is placed at the centre of the towing tank 20m
from the wave generation system.
At present the initial wave height reference (zero-point) at no
wave condition is set manually, i.e. a person goes into the tank
and fixes the probe to the reference point at the no wave
condition. It is difficult to set the reference accurately and the
procedure is time consuming. Thus a mechanism for remote
monitoring with a provision for adjustment of the reference
point (‘zero’) in an HSTT is highly desired.
2. METHODOLOGY
2.1 BLOCK DIAGRAM
The mechanism used in the system for setting the wave probe
reference consists of two sections; Transmitter section and the
Receiver section.
Fig 1: Block diagram of the proposed mechanism
As shown in the block diagram of the system in Fig 1, there
are two microcontroller units. First unit is used to display the
position of wave probe and transmit the control signal to the
other microcontroller unit. The second microcontroller unit is

__________________________________________________________________________________________
used to set the position of wave probe according to the
received control signal.
Waves are generated by wave generation system and are
measured using a wave probe which gives voltage in the range
of +/-10V according to the wave level. This voltage is feed to
the ADC through a cable. The microcontroller receives the
digital output of the ADC. According to the digital data the
microcontroller displays the position (cm) and the output
voltage (V) of the wave probe which is presented on the LCD
display. If the wave probe is not at the ‘zero’ reference
position, the microcontroller displays other than ‘zero’ value
To bring the wave probe position at ‘zero’ reference point we
use a keypad by which a control signal is sent to other
microcontroller unit through the transmitter.
At the other microcontroller unit the receiver receives the
control signal and feeds the microcontroller. According to the
control signal, the microcontroller drives the stepper motor in
forward or reverse direction. The wave probe is mechanically
attached to the stepper motor. Therefore when the stepper
motor rotates the wave probe moves upward or downward
direction till the position at the ‘zero’ reference point.
2.2 CIRCUIT DETAILS
As shown in the circuit in Fig 2 the 50Ω metal resister
attached between REFOUT and REFIN, is used to operate in
unipolar mode (i.e. 0 to +10V and 0 to +20V). In this case the
BIPOFF is connected to the ground. If the BIPOFF is
connected as shown in the circuit, the ADC operates bipolar
input (i.e. +/-10V and +/-5V).
Figure 2
Now the analog signal should be converted into the digital
data and the MAX174 ADC uses a successive approximation
technique to convert unknown analog input to a 12-bit digital
output code according to the control signal as shown in the
truth table.
Table 1: Truth Table
CE CS R/C 12 /8 A0 OPERATION
1 0 0 X 0 Initial 12-bit
conversion
1 0 0 X
1
Initial 8-bit
conversion
1 0 1 0 X Enable 12-bit
parallel output
1 0 1 1 0 Enable 8-bit
MSB parallel
output
The output of the ADC signal also depends upon the control
signal as shown in the truth table. These control signals are
connected to the higher nibble of port-2 of the microcontroller.
The digital outputs of the ADC pins are connected to port-0
and to the lower nibble of the port-2 of microcontroller. The
microcontroller receives the digital data and accordingly
displays the position and the output voltage of wave probe on
LCD. The LCD data pins are connected to the port-1 and the

__________________________________________________________________________________________
control signal pins of LCD are connected to the some of the
port-3 of controller.
For the LCD display other than ‘zero’ reference value we use
normally on-off-on switch which is connected to external
interrupts of the micro controller. When these push buttons are
used some controlling message will pass through the serial
TxD pin to the ST-FTX01-FSK transmitter module. The
controlling message takes FSK modulation with 434/868MHz
frequency range. This modulated signal takes the transmitter.
The receiver receives the 434/868MHz range of frequency
signals and demodulates the digital data. The data is given to
the microcontroller through serial RxD pin. Now the
microcontroller compares the controlling message by using a
program. According to that data it drives the stepper motor in
forward or reverse direction. But the microcontroller cannot
drive the stepper motor because it does not give sufficient
current to the motor. IRI44N power MOSFET is used like a
driver to drive the stepper motor
Figure 3
Each MOSFET is connected to microcontroller and stepper
motor as shown in the Figure 3.
The systems in Figure 2 and Figure 3 require individual power
supply. In the power supply unit we use step down transformer
to get the required voltage from the 230V AC input. This
voltage is converted into DC voltage by using rectifiers
(diodes like IN4007 and IN5409). The output of the rectifiers
consist some amount of the ripples and to filter the AC ripples
we use a smoothing capacitor. This DC voltage is regulated by
the regulators according to the application.
The stepper motor is allowed to the wave probe with
mechanical interface as shown in Figure 4.
Figure 4
The wave probe is based on a conductivity type wave gauge
which comprises two thin parallel stainless steel electrodes.
When immersed in water, the meter measures the conductivity
of the water volume between the two electrodes that changes
proportionally with the change in water surface elevation, i.e.
the wave height between electrodes.
3. FLOWCHART:
The wave probe reference setting is controlled by the
microcontroller software. The embedded software
development is carried out with the keil vision3IDE
(Integrated Development Environment). By using the software
we select conversion and read mode as shown in Figure 5.
After the completion of the conversion the reading data is kept
in two registers since the reading data is of 12-bit size. This
12-bit data should be converted into 8-bit data by using
embedded software since the LCD used can receive and
display 8-bit data only at a time.

__________________________________________________________________________________________
The LCD control signals are also controlled by the
microcontroller software. When the program is executed it
checks the interrupts every time. If any interrupt takes place
then it will send data i.e. controlling data to the other
microcontroller through serial communication.
Here the serial communication takes place with 9600 baud rate
and this baud rate can also be changed by using the program.
Now the received data in other microcontroller compares. If
this data equals to the reference data the microcontroller
software rotates the stepper motor in the direction of reverse
or forward according to the data. Otherwise the
microcontroller will wait till the required data received.
Figure 5 - Flowchart
4. RESULTS AND ANALYSIS:
The hardware and software test is done thoroughly and the
bench test is done. The output of the wave probe and the
length of probe manual are compared with multi meter &
vernier scale and are listed in Table 2.
Table 2
The error profile plots shown in Fig 6 which are measured
from the difference between the system readings and manually
measured readings are obtained.
Figure 6 - Error Profile plots
The mechanical arrangement and the environmental
conditions result in slight change in the measured values from
the expected result, so the expected output is not exactly same
as the system reading. The significance of these plots is that, it
indicates the variation of the error value for different
instances.
CONCLUSIONS
An automatic mechanism for remote monitoring with a
provision for adjustment of reference point (“ZERO’) in a
HSTT was proposed. There is an observed increase in
performance with the designed system and this system
adjusted the wave probe at the reference point (‘zero’)
remotely. The system can be programmed to work in
WAVE PROBE
POSITION (cm)
WAVE PROBE
OUTPUT VOLTAGE
(V)
Scale
readings
(cm)
System
readings
(cm)
Multi
Meter
readings
(V)
System
readings
(V)
0 0.009 -0.004 0.014
0.6 0.504 0.129 0.136
1.1 1.011 0.278 0.283
2.2 2.005 0.555 0.561
3.2 3.016 0.833 0.844
5.3 5.075 1.393 1.406
10.3 10.069 2.786 2.797

__________________________________________________________________________________________
automatic mode by making changes in the program where the
system checks the reference value and if there is no reference
value automatically it comes to reference value.
REFERENCES
[1] J.Tukker, J.J.Blok, G.Kulper, R.H.M.Huijsmans, “Wake
flow measurements in Towing Tanks with PIV” at 9th
International symposium on Flow visualization 2000.
[2] Johnson, B. and S. Enzinger, "Inexpensive Side Beaches
for Improving Calm Water Testing Efficiency”, Proceedings
of the 18th International Towing Tank Conference, 1987.
[3] Jeng Horng Chen, Che-Chun Chang, “A moving PIV
system for ship model test in a Towing tank”, Science Direct,
2006
[4] Gregory Payne, “Guidance for the experimental tank
testing of wave energy converters”, Supergenmarine,
University of Edinburgh
[5] J.M.J. Journée and Jakob Pinkster “Introduction to Ship
hydromechanics” Draft Edition, April 2002
[6] A Maggi, G Thomas and B McRae “A comparision of
Numerical and Towing Tank predictions with full scale
measurement” RINA International Conference, 1998.

An automatic wave probe reference setting mechanism

More Related Content

What's hot (20)

Viewers also liked (20)

Similar to An automatic wave probe reference setting mechanism (20)

More from eSAT Publishing House (20)

Recently uploaded (20)

An automatic wave probe reference setting mechanism