EoW May 2009

EuroWire – May 2009

technical article

Another advantage of the ROV was its

ability to provide real-time high-resolution

video images via a high-resolution camera

and sophisticated lighting, as seen in

Figure 3

Since the ROV’s buoyancy, yaw and

pitch could be adjusted on the fly, this

ROV could be very effective on missions

requiring tricky manoeuvres.

3.4 Disadvantages

The Deep-Sea ROV was designed for a

niche application. Because it was a slow

moving vehicle (< 3 knots) and it had a

finite amount of battery life, the ROV had

to be placed in very close proximity to the

inspection site.

A majority of the time it would be carried

to the site via a manned submersible in a

launch and recovery enclosure (LARE) as

seen in

Figure 4

. The BOT could operate in

currents of 2 knots or less.

4 Hybrid AUV/ROV

4.1 Purpose

The purpose of the hybrid vehicle is to

take the advantage of the Deep-Sea

ROV technology and couple that with

the advantages of an autonomous, free

swimming vehicle. This was achieved by

using a Myring hull design vice the box

shape of the first generation Deep-Sea ROV.

The Hybrid AUV/ROV is capable of greater

distances as well as the handling of strong

water currents. The Hybrid AUV/ROV has

two modes of operation: (1) autonomous

and (2) ROV. In the autonomous mode, the

vehicle can be programmed via mission

planning software to operate using

waypoint navigation. In this mode the fibre

optic tether can be used to monitor the

vehicle’s activities and allow the operator

to take control of the vehicle at any time.

Additionally, if the fibre optic tether were

to break, the vehicle is pre-programmed

to return to a selected location for

recovery. In the ROV mode, the operator

can take control of the vehicle to conduct

inspections such as to check damage on

hulls of ships, potential faults in dams, and

leaks in potable water tunnels.

4.2 Description

The shape of the Hybrid AUV/ROV is

drastically different from that of the

original Deep-Sea ROV. The profile of the

vehicle mimics the contours of a standard

submarine or torpedo design.

The body shape allows the vehicle to

speed (> 3.5 knots) through rough waters

and heavy currents.

The Hybrid AUV/ROV is 6" in diameter and

over 62" in length. Though larger than the

Deep-Sea ROV, it has the agility needed

to position itself for near field inspections.

The vehicle has a main propulsion screw

for forward and reverse motion as well as

vertical and lateral thrusters located in the

fore body. Refer to

Figure 5

for a schematic

of the AUV/ROV.

The Hybrid AUV/ROV is similar to the

Deep-Sea ROV in that it has an onboard

power supply and is tethered to the

command station via the same Deep-Sea

ROV cable. Cable is paid out of the

vehicle in a more simplistic manner than

the original Deep-Sea ROV, storing up

to 2,000metres of cable within its hull.

The tether leaves the vehicle via a small

tube called the stinger, so as to prevent

the cable from getting caught up in the

propulsion system.

The Hybrid AUV/ROV has improved

electronics and sensors to allow it to

perform its role as a piece of inspection

equipment.

4.3 Advantages

The Hybrid AUV/ROV has the capability

of travelling long distances without any

human intervention via its autonomous

operation mode.

The advantages of the autonomous

mode are that: (1) it provides a stand-off

capability from the work site and (2) it

eases operator loading by not having to

steer the vehicle at high speed over a long

distance. Without a stand-off capability,

the Hybrid AUV/ROV would have to be

delivered to the work site via a manned

submersible, more like the Deep-Sea ROV.

Additionally, the vehicle’s autonomous

capability provides a means to recover

the vehicle if the fibre optic tether were

to sever or break during the operation.

The vehicle can be pre-programmed

prior to the start of the operation

with a geodetic location to return to if

communication is lost. This could be as

simple as a single location or instruction

to swim out on the same path as was used

to reach the work site.

To assist with autonomous navigation the

Hybrid AUV/ROV is equipped with a GPS

(Global Positioning System). The vehicle

can be programmed to come to the

surface during transit to the work site to

obtain a navigational fix. Once the fix has

been obtained the vehicle can correct its

course and proceed to the next waypoint.

The vehicle is also equipped with

high-frequency sonar, as seen in

Figure 6

which is employed for obstacle avoidance

and to help locate the work site.

Once the Hybrid AUV/ROV has reached its

destination the operator shifts to the ROV

mode and monitors the high-resolution

imagery available from the two video

cameras. One camera is located on the

nose and the other on the GPS mast.

The camera located on the GPS mast

is used both surfaced and submerged.

This camera can assist with navigation

when surfaced and provide a different

perspective when submerged since

the nose of the vehicle is visible in the

viewing area.

In addition, the Hybrid AUV/ROV has two

lasers located on the nose, used to provide

a fixed reference frame for sizing objects

seen through the nose camera.

4.4 Disadvantages

The Hybrid AUV/ROV was not designed to

penetrate shipwrecks or small void areas;

the long length of the vehicle offsets the

small diameter size.

Figure 3

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Figure 4

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Figure 5

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Figure 6

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