Soon after the vanishing of flight 370 Malaysia Airlines, authorities
approved the underwater search for the wreckage with an unmanned submersible
vehicle to chart the bottom of the sea in a meticulous procedure. With the
black boxes not transmitting a signal the Bluefin 21 autonomous underwater
vehicle was called to action to generate a detailed, three-dimensional chart of
the sea bottom 4,500 meters down with the side sonar. This type of unmanned
platform is designated as an autonomous underwater vehicle because of the stages
of autonomy necessary by the control, command, and communication encounters functioning
underwater.
Exteroceptive
Sensors Bluefin 21 Search and Rescue
The Bluefin-21 is an adaptable underwater vehicle configurable
with different sensors. The Bluefin-21 operates particular exteroceptive and
proprioceptive sensors that endure sea operations. The conditions they operate in
demands the use of inertial and ultrasonic sensors which gather information to
be analyzed after the task is completed. Bluefin has incorporated over seventy
sensors. Exteroceptive sensors consist of vision systems in particular the side
scan sonar from EdgeTech 2200-M 120/410 kHz, an efficient device for searches of
the bottom of the sea. Accurate images of the area are delivered with signal
technology called Full Spectrum® CHIRP Managing, Dynamic Aperture and
Dynamically Focused Arrays increase long range resolutions through better
signal-to-noise ratios. Multi-Pulse technology sends up to four pulses in the
water at once, allowing a four times inspection speed increase, or a noticeable
surge of pings on the objective, for greater feature recognition. The calibrated
wideband digital Frequency Modulation sonar provides quantifiable and estimate,
low-noise, high-resolution side scan pictures. It transmits straight swept
Frequency Modulated pulses placed at two separate frequencies. The transmission
of a longer duration, wide bandwidth pulse ends in higher resolution images
and, because more energy is projected into the water, a better signal to noise
ratio results in extended range (Subsea Technology Rentals, 2016). The Synthetic
Aperture Sonar (SAS) combines consecutive pings constantly along an identified path
to increase the azimuth resolution. SAS produces high-resolution images up to
hundreds of meters, down to centimeter resolution range. This makes SAS an
appropriate technique for search of small items and imaging of wreckages (Hanson,
2011). Multibeam echo sounders obtain water depth info in a search area; to establish
smallest sea depths over significant objects such as wrecks, and detection of objects
in general. The Multibeam echo scanner produces signals in the form of a wave
from underneath the vehicle. Estimating and recording the time it takes for the
sound signal to travel from the transducer to the bottom of the sea and back to
the receiver (National Oceanographic and Atmospheric Administration of Coast
Service, 2016).
Proprioceptive
Sensors Bluefin 21 Search and Rescue
The proprioceptive safety system sensors detect leakages and
faults, conduct drop weight analysis, track transponders, antennas strobe, RDF,
and Iridium. The navigational sensors include Inertial Navigation Sensor (INS) a
navigation technique where dimensions specified by gyroscopes and
accelerometers are utilized to trace the location and path of a target in
relation to a referenced initial position, course, and speed. Inertial
measurement units (IMUs) include three orthogonal rate accelerometers and three
orthogonal gyroscopes, estimating angular rate of displacement of an object and
linear rate of change of velocity of an object (Woodman, 2007). The Ultra-Short
Base Line sensor is a marine locating system that utilizes a craft attached
transceiver to sense the space and direction to an object utilizing sound signals.
USBL sensors are also comprised on other components, to include attitude
sensors for the precise determination of vessel roll, pitch and direction, and
for correction functions (Sonardyne, 2015). A transmissometer for measuring the
reduction of light as it travels through a water used for defining turbidity of
the ocean (WetLabs, 2016).
Research
Questions
The
implemented Global positioning System, the Ultra-Short Base Line and the
Inertial Navigational System sensors are specifically intended for the sea
environment to ease the restrictions of radio signal transmission and
navigation across seawater. A change to the system that would make the vehicle
more effective in marine search and rescue operations is the development of a better
battery technology such as high energy density batteries with deep cycle life
and performance to prolong the operating range and to sustain sensors and
propulsion systems for longer operating time and cover greater search areas. Unmanned
aircraft systems could be employed in conjunction with the Bluefin-21 to determine
locations of importance from drifting remains or oil spots to the vessel that
operates the unmanned vehicle via acoustic link. Incorporating the operation of
an unmanned aerial vehicle and the underwater unmanned vehicle in the same ship
would significantly reduce expenses and strategically control the management
roles and enabling interaction among operations. Unmanned maritime vehicles contribute
to individual welfare and budget balance over their manned counterparts.
NOAA Office of Coast Survey. (2016). Multibeam Echo Sounders. Retrieved from http://www.nauticalcharts.noaa.gov/hsd/multibeam.html#
Subsea Technology Rentals. (2016). EdgeTech 2200 Modular Sonar System. Retrieved from http://www.str-subsea.com/sales/edgetech-2200-modular-sonar-system#
Woodman, O. J. (2007). An introduction to inertial navigation. Retrieved from https://www.cl.cam.ac.uk/techreports/UCAM-CL-TR-696.pdf#
Wet Labs. (2016). C-Star Transmissometer. Retrieved from http://wetlabs.com/cstar#
Luis,
ReplyDeleteThe proprioceptive and exteroceptive sensing capabilities of the Bluefin-21 are nothing short of amazing. Your article is well written and informative. Excellent description of how sensors work in an underwater environment as well as how such technology can assist SAR.
Thank you Mark, one of the reason that caught my attention on the Bluefin 21is the significant design of hardware and software architecture. The state-of-the-art UUV includes GPS/INS/DVL navigation capability, low noise propulsion, and power sufficient to carry out task for more than 24 hours.
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