This paper is based on the REMUS 600 autonomous underwater vehicle
(AUV) designed by the Oceanographic Systems Laboratory of the Woods Hole
Oceanographic Institution. This 12.75 inch in diameter AUV was developed for
variety of underwater missions including environmental research, underwater
mapping, and performing mine countermeasures operations.
The REMUS 600 features a modular design, which allows for easily reconfiguring
of its sensors for different missions. The vehicles endurance is up to 70 hours
at speeds of 5 knots. The REMUS 600 can operate at depths up to 600 meters.
With its increased payload it has a range of 286 nautical miles (Patterson, 2009).
The vehicle is equipped with variety of sensors, which include a
Kearfott KN-4902 Inertial Navigation System (INS), and an Acoustic Doppler
Current Profiler (ADCP). A tail mounted GPS antenna also provides WIFI
connectivity at up a 2.5 miles range. An Iridium satellite link is used for
long range communications with the vehicle, enabling the AUV to “call home”
from virtually any location. The REMUS 600 also carries a micro modem
supporting the Compact Control Language. This feature allows real-time
transmission of acoustic vehicle parameters and data to either a laptop or the
vehicle tracking device. This control feature allows the operator to follow the
status of the AUV and monitor the mission progress.
Other sensors installed on the AUV include pressure sensor, side
scan sonar, temperature, and conductivity probes. Optional sensors include a dual
frequency side scan sonar, a video camera, an acoustic imaging sensor, a synthetic
aperture sonar, an acoustic modem, and a fluorometers (Kongsberg, n.d.).
These sensors provide data on the vehicle internal status and its
location as well as a variety of environmental data. Such information as water
quality, salinity, fluorescence, temperature, and bathymetry. The synthetic
aperture sonar produces high resolution images combined with a large swath
width as compared to conventional single beam side-scans. Laser The Scaler
Gradiometer (LSG)/ Re-acquisition Payload assembly combines a magnetometer with
an electronic still camera and short range, dual frequency side scan sonar. It
collects data from a large search area and provides classification of targets
such as buried mines. The sensor data is downloaded at the end of each mission
upon recovery of the AUV (Stokey
& Roup, n.d.).
By joining the sensor data with the navigation data, 2D and 3D
visualization of the environmental parameters can be displayed. Data
presentation methods range from color coded diagrams, still images acquired by
the camera, and navigation maps from sonar imagery taken by side scan sonar. The
temperature sensor data can be presented via diagrams with color coded
information and combined with depth sensor and navigation data to present a
complete picture of the area. Figure 1 presents the data presentation methods
in a form of diagram. Figures 2 and 3 present the data from the camera and side
scan sonar.
Figure 1. Water temperature at
various depths. Adapted from “Development
of REMUS 600 AUV,” by Stokey, R., & Roup, A. (n.d.). Copyright by WHOI.
Figure 2. Data presentation methods: 5 meter altitude electronic
still image, with 200 W-S strobe illumination (right) and 900 kHz, 30 meter
range scale sonar image (left). Adapted from Adapted from “Development of REMUS 600 AUV,” by Stokey, R., & Roup, A. (n.d.).
Copyright by WHOI.
Figure 3. SAMS II, MSN012, 300kHz Side Scan Image showing transit
across fault. Adapted from Adapted from “Development of
REMUS 600 AUV,” by Stokey, R., & Roup, A. (n.d.). Copyright by WHOI.
The control station of the REMUS AUV can be based on shore or on a
support ship. The operator is interacting with the vehicle using simple laptop.
The AUV control computer is based around the PC-104 technology. The CPU is
assembled on a motherboard with eight 12-bit analog to digital channels,
input/output ports, power supplies, and other interface circuitry. The user
controls the AUV and monitors its status through its diagnostic software and
communicates via an RS-232 serial link. The REMUS vehicle interface program,
called REMUS VIP is designed to run on a laptop equipped with Windows. The Vehicle
Interface Program (VIP) is used for control and monitoring of the AUV. The interface
program allows the operator to plan the mission, perform vehicle operational
maintenance checks, download and analyze sensor data. The VIP features a Windows
based operational interface, a quality control check, and an easy to read
vehicle parameters indicators ("REMUS,"
n.d.).
The vehicle diagnostic software display the status of all vehicle
sensors. The operator can easily control the vehicle via sliders and buttons.
The mission route can be uploaded via the VIP interface, which includes route
points and the location of the transponders. As we can see from the Figure 4
the status of all major sub-systems and diagnostic messages is available to
view on a single screen, which reduces the need to switch between screens and
allows the operator to focus his attention on one monitor. All telemetry data
is recorded by the vehicle during its mission and is available for later
review. This interface design allows the operator to control the vehicle while
monitoring vehicle health and sensor data at the same time (Woods Hole Oceanographic
Institution [WHOI], 2007).
Figure 4. Graphical user interface is highly intuitive. Adapted
from Adapted from Adapted from “Development of REMUS 600 AUV,” by Stokey, R.,
& Roup, A. (n.d.). Copyright by WHOI.
The REMUS AUV can also use
gateway buoy for communication with the control station. It allows for remote
monitoring, tracking, and control. The AUV may surface, uplink with the buoy,
and send information to the operator.
One of the challenges of
REMUS control pertain to the vehicle’s operational environment. The underwater
operational domain present such restrictions as control and datalink signal
constraints. GPS, Iridium, and WiFi signals are unavailable when AUV is
operating under water. Retrieval of the mission data is performed after the
vehicle surfaces. Most of the information from the vehicle needs to be
processed after retrieval. One of the suggestions for improving AUV operation
is installing data processing system directly onboard of the vehicle, therefore
data could be preprocessed before it is downloaded. When the AUV surfaces, the processed
data can be send over limited bandwidth to the operator. It can help review the
mission in real time and make decisions on how to proceed with the survey in the
most efficient way. If no bandwidth is available, the preprocessed data can be
quickly uploaded at the end of the mission and will require minimum processing
after upload.
Another improvement that can be recommended pertain to the control
station design. Most of the data from the REMUS is presented in a visual
format, which is a one-sided approach. Although the computer screen presents a
variety of useful sensory information for the controller, it can be
overwhelming and fatiguing. Although the control station feature a simple
interface based on a windows laptop, some improvements may help increase
operators situational awareness. For example, incorporation of audible alarms
in case of vehicle parameters are out of normal. Although most of the AUV
operation is autonomous, while vehicle is on the surface it is possible to control
it path by the use of a control joystick that could incorporated a haptic
feedback system.
References
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