Unmanned underwater vehicles: strategic allies of the marine industry

09/07/2021

The first record of a recorded underwater vehicle dates back to 1578, at which time an Englishman named William Bourne wrote about a submarine in his book Inventions and devices, and although there is no evidence that he built one, it means that the idea of such a means of transport had already emerged.

Approximately half a century later, in 1620, the first working prototype of such a vehicle was built, it was christened the Drebbel by its author, Cornelius Drebbel, and although its plans have not survived to the present day, there is evidence that it was the first submarine in history.

In the 18th century, approximately in 1775, the Turtle was created, an experimental vehicle built by the American David Bushnell, conceived for war purposes, for use during the American Revolution. A few years later, in 1800, what is considered the first modern submarine in history was created: The Nautilus, an underwater vehicle of approximately six and a half meters in length, designed by Robert Fulton. It successfully passed several test dives but was sold and dismantled because it failed to convince the French and British navies.

During the rest of the 19th and 20th centuries, various inventors of different nationalities continued to build submarines, perfecting them. Their use was extended during the First World War and at the end of it, the great powers of the world realized their value, so they decided to create smaller versions that had a better patrolling capacity because they were faster.

After the war, submarines have continued to be produced, both normal and their "dwarf" versions, however, their purpose is now more preventive than operational. Moreover, since knowledge of the seas is a subject of great global interest, a multitude of technologies are being developed to explore it. Currently, mini-submarines are used for exploration, as in the Deepsea Challenge expedition, rescue missions, such as the search for the Argentine submarine ARA San Juan, as well as in scientific research, an example of which is the Slocum Glider, used in research programs at Rutgers University. For some years now, with advances in technology, especially in the area of robotics, unmanned versions of these vehicles have been developed: the ROVs and AUVs.

ROV and AUV, what are they and how do they work?

Both ROVs (Remote Operated Vehicle) and AUVs (Autonomous Underwater Vehicle) are unmanned underwater vehicles, usually small in size, which can be equipped with a multitude of devices such as video cameras, sensors, and sonar, allowing them to perform a multitude of tasks underwater. The difference between the two types lies in their handling: ROVs are powered, received, and transmitted by cables; through these, the operator also maintains communication with the vehicle, controls it, and obtains information from its sensors and tools, all this through a control station. These control stations can be simple and contain the computer with which the vehicle is operated and the power sources with which the ROV is powered, they can include extra screens to display more information of the systems onboard the vehicle, or they can be quite complex stations, located in special rooms for them.

On the other hand, AUVs are autonomous, i.e. they do not require operator control and are independent of external cables, and are powered by rechargeable batteries. Since radio waves cannot penetrate far into the water, the use of GPS in these vehicles is not possible, so, to locate themselves, they resort to other types of techniques, such as dead reckoning navigation.

How big are these vehicles?

The size of an ROV or AUV depends a lot on the purpose of the vehicle and the depth to which it will be submerged. There can be small vehicles, less than 20 cm in diameter and barely a couple of kilograms, that are even capable of entering underwater pipelines to perform inspections, or vehicles that require very deep dives, five kilometers deep or more, that can weigh more than three tons, such as the ROV 'ISIS'.

What can they be used for?

In addition to underwater exploration, rescue operations, and scientific research, these vehicles are very versatile and have applications in several areas of great interest.

Fishing industry

One of these applications is in the fishing industry. A. Rojas Granados presented, in 2014, in Lima, Peru, a research on the development of an AUV autonomous underwater vehicle to help fishing vessels identify small fish and avoid catching them, since in the country, catching young specimens is punishable by fines proportional to the amount of the catch. In China, a former foreigner named Zhang Wuyi started a business building mini submarines to support local fishermen. In Querétaro, Mexico, a startup called Tecnologías Marinas México (TMMx) designed an ROV-type mini-submarine, whose purpose is to increase the productivity of fishing companies by providing them with a set of technologies such as sensors, cameras and sonars, which allow for the timely detection of shoals, improving catching capacity.

The incorporation of ROV-type unmanned vehicles in this process will increase the effectiveness of the capture of the marine resource. Currently, detection is mainly carried out by direct observation techniques from the ship, or by analyzing the behavior of creatures such as birds and dolphins, called visual localization. Observation by airplanes or small planes is also carried out, which, although more modern, only allows the detection of shallow shoals and requires a very experienced pilot and observers, as well as depending on very favorable maritime conditions, such as very good lighting and calm seas. Although direct observation has been supported in recent years by technologies such as ship-deployed sonar, its use is limited to a radius around the vessel.

The implementation of unmanned underwater vehicles gives the fishing industry a tool that allows searching the ocean and its depths without the need to move the vessels to do so, with the consequent savings that this implies: due to the increase in fuel prices, the operational cost of the engines is higher than that of supplying a mini-submarine. The aim is to use them as small, autonomous scouts that report their observations to the vessels.

Underwater maintenance

Another area where these vehicles are of great use is in the inspection and maintenance sector. From the inspection of the hulls of ships that make up fleets, whether merchant or fishing, to the inspection of marine structures, such as oil platforms, pipelines, dams, bridges, etc., ROVs can be used to perform these tasks.

Apart from the aforementioned tools, these vehicles can be equipped with robotic arms, cutters, welders, and ultrasound equipment, which allow them to extend their capabilities and move from an exploration role to one of inspection and maintenance. With advances in robotics, these devices are becoming more and more precise, making it possible to achieve accuracy very close to that of a human performing tasks.

Their use has a great advantage: it reduces the risk of employing divers for these tasks, which are usually quite dangerous, either because of the depth at which they are performed or because of the nature of the activity. Providing ultrasound equipment allows the vehicle to detect cracks and internal structural damage to the vessels, damage that cannot be detected by direct observation. Its onboard computers can form images from the data obtained by performing an ultrasound sweep. These images are then analyzed by the vehicle operator, who determines if there are any cracks in the analyzed surface.

Conclusion

Underwater vehicles, whether autonomous or remotely operated, have a bright future. The possibility of models and sizes that exist and can be created opens up a wide range of fields of use. In the fishing industry, they can increase the volume of fish caught, while reducing bycatch rates. Likewise, in the maintenance area, they can reduce the mortality rate in divers by managing to perform certain tasks without putting a human at risk. However, the fact that they cannot be reliably controlled by wireless transmission, coupled with the not so competitive prices today, means that there is still time for all companies or individuals who can make use of them, to implement them in their activities.

By Alexis Arturo Aguirre-Roldán and Santiago Miguel Mendez-Fraga, Source: CIENCIA UANL / No.96