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The Small Autonomous Underwater Vehicle -
Maya
Maya AUV uses a single underwater motor to propel
itself through the water. It has two stern planes
and a single rudder to control diving and heading
maneuvers respectively. The nose section is removable
and different sensors can be fitted on to it for
specific missions at sea. The AUV can receive
commands from the shore over a high-speed radio
link or download data over the same link. Underwater
navigation uses a Doppler Velocity Log (DVL) to
measure speed and a navigation filter that estimates
it’s position below sea surface. Surface
navigation is based on GPS ( Global Positioning
System)
Vehicle parameters :
| Total length |
1.8 m |
| Diameter |
0.234 m |
| Shape |
Slender Ellipsoid |
| Hull |
Aluminium 6082 |
| Nose and rear Cone |
Acetal homopolymer |
| Depth range |
200 m |
| Propulsion |
Single electric DC brushless
motor |
| Nominal speed |
1.2 m/s |
| Endurance |
~ 6 hrs |
| Power source |
Lithium polymer cells |
| RF Communication |
2.4 Ghz, 115 kbaud |
| Scientific Payloads |
Chlorophyll, CTD, Oxygen optode,
radiometers, camera, fluorometer |
The Maya AUV has many applications in oceanography
as it can collect standard oceanographic data
in confined areas; do shallow water bathymetry
in coastal waters ; or detect phytoplankton blooms
with the help of optical radiometers and fluorometer;
it can be used as a platform for testing new marine
sensor technologies. In its present version Maya
has been used for oceanographic data collection
only.
The following are the payload sensor used on
AUV Maya :
AHRS400CC-100, MZ104, Battery Monitoring Node,
SonTek DVL, M12 GPS, Freewave Radio, Volz motors
x 4, Vicor DC-DC x 2, Honeywell PPTR, Thruster
and Actuator node, Tritech Sonar, Technadyne Thruster,
Thruster Instrumentation, RBR XR-420 CTD, Aanderaa
Oxygen Sensor, IQEye Camera, TriOS Radiometers
x 2, Chlorophyll Sensor, Science Node
Data logging of science based sensors
Sensor payloads of Dissolved Oxygen (DO) , Chlorophyll,
Turbidity, Temperature, Conductivity were interfaced
to a Rabbit Core micro-conntroller through RS
232 serial ports. The data records of each sensors
are stamped with date, time, and GPS values which
are transmitted from the MZ 104 main controller.
The DO and chlorophyll cum turbidity sensors are
mounted on a nose cone. A separate nose accommodates
the larger CTD sensor.
The stern and rudder planes of the AUV (called
foils) are designed to follow a NACA 0015 section.
What are the advantages of this section ?
- A symmetrical foil – easy to manufacture.
- Zero lift at zero angle of attack.
- Good torsional rigidity with a high thickness
ratio
Table 1 : Major foil characteristics
| Foil parameter |
symbol |
value |
| Single fol |
b |
0.160 m |
| Root chord |
Cr |
0.09 m |
| Tip chord |
Ct |
0.06 m |
| Mean chord |
ê |
0.076 m |
| Thickness chord |
(t/ê) |
0.16 |
| Taper ratio |
^=(Ct/Cr) |
0.67 |
| Exposed foil area |
Se |
0.0158 m² |
| Aspect ratio (foil) |
ARe |
2.79 |
Aspect ratio
(body + foil) |
b² /Surface area |
6.4 |
| Leading edge angle |
^le |
10.6° |
| Sweep angle at |
^c/4 |
8.03° |
| Ruder L.E. to nose |
Xr |
1.177 m |
| Fin L.E. to nose |
Xle |
1.127 m |
Table 2 : body parameters of the
small AUV (according to Myring)
| Parameter |
Value |
| Length (Lpp) |
1.67 m |
| Diameter (d) |
0.20 m |
| Span tip to tip (B) |
0.51 m |
| Nose length (a) |
0.216 m |
| Nose tip to rear (b) |
1.416 m |
| n (myring) |
2 |
| Ø(myring) |
25 degs |
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