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16 November 2020

Article by Nuno Mathias, naval engineer at INEGI


Autonomous underwater vehicles (or AUV) are a valuable resource for a wide range of applications. From science, both exact and human sciences, to the commercial area, for determining mining sites or for the future installation of offshore structures, keeping in mind also military activities, for border control and removal of explosive or incendiary devices.

However, whatever their mission, at some point these vehicles have to return to recharge their batteries. An especially problematic limitation when the objective is to travel great distances to explore the depths of the ocean.

Technological obstacles limit underwater exploration

With the advent of the Industrial Revolution and the Enlightenment, allied to the appearance of the scientific method, an increased interest in the knowledge of the world fauna and flora, as well as the geological phenomena of the land masses, was generated in the scientific community. And it was this interest that drove the creation of new agricultural, industrial and transportation artefacts.

However, unlike their terrestrial counterpart, the oceans preserve their component of mystery. Human knowledge is largely limited to the phenomena that occur on the surface, with an estimated 95% of the depths of the ocean unexplored1. The inability to observe the ocean floor directly is often associated with technical limitations, namely the high pressures and low temperatures, related to the water column and low solar incidence, which prevent a direct human presence.

These obstacles led engineers Stan Murphy and Bob François of the University of Washington to develop the first autonomous underwater vehicle in 19572, followed by the first remotely operated vehicle (or ROV), developed by the American navy in the 1960s3. Their original purposes were different, however they converged on the need to explore the different seas with greater diligence and precision. The big difference between both is related to the need to have an umbilical cable (case of ROVs) or to be completely autonomous (case of AUVs).

Docking stations are the answer to the challenge of autonomy

The autonomous underwater vehicles used today, more than fifty years later, have a range of only a few hours4, and, like electric cars, are limited to a few nautical miles. Creating charging stations and data transmission is therefore crucial to extend the use of this emerging technology.

In this context, service stations, called docking stations, appear at the forefront of technological development, for data transfer and battery charging. The need to download data is equally important, so that onshore processing can make the measured standards clear and determine new missions.

These can be located along the entire water column, from the surface, to the bottom, through suspended or towable. Most docking stations stand out for their conical shape and a purely mechanical adhesion via pins, however, they are limited to a single AUV geometry and dimension. Its manufacturing price is still high and its technological maturity is low, so the margin for progress in terms of development is wide.

Another problem often associated with docking stations is related to the precise positioning of the AUV. This challenge becomes particularly complex in the presence of AUVs with a longitudinal propulsion system, since the associated error, derived from the presence of chains and imprecision of the installed equipment, prevents correct docking at first, making the AUV have to proceed to a series of attempts to dock properly, often causing considerable damage to its hull. Thus, it is necessary for AUVs and docking stations to move to a common point in order to allow a faster and more reliable implementation of technology on the seabed for long periods of time.

The challenges imposed to underwater robotics are also challenges assumed by INEGI. These challenges have led to a particular interest in the recent technological development of underwater robotics, which refers to fixed stations for continuous monitoring from a fixed location, as well as docking stations, to increase vehicle autonomy and data transfer.

Technological innovation paves the way for autonomous recharge on the high seas

In view of the emergence of this development, INEGI stood out, through its expertise in mechanical design, hydrodynamic analysis and structural analysis, in the development of a fixed, modular station capable of serving multiple uses, with the capacity to insert a vast payload for ocean monitoring (within the AMALIA project). Also noteworthy is the development of an AUV docking station capable of providing service to 4 different AUV geometries, as well as solving the AUV docking accuracy challenge (INTENDU).

The latter significantly changes the paradigm associated with docking stations, as it allows to accommodate AUVs with standard dimensions, as well as to correct divergences in its positioning, through a disruptive design able to align with the chains and a fixation system capable of combating local inaccuracies.

The technological development of solutions for the underwater environment, through the creation of docking stations, represents a more efficient approach to a known problem, thus allowing to generate more knowledge of the environment. This approach also allows companies to, in the near future, be empowered with new tools capable of generating accurate data, thus allowing them to reach new horizons in terms of science, the market economy and defense, and generate greater added value for themselves. and their associates.

To this end, it is essential to continue investing in R & D + I so that technological development can serve and add knowledge to a world hitherto unknown.



1. The Ocean Portal Team. The Deep Sea | Smithsonian Ocean Portal. (2016).

2. Widditsch, H. R. SPURV-The First Decade. APL-UW 7215, Appl. Phys. Lab. Univ. Washingt. (1973).

3. Robison, B. H. The Coevolution of Undersea Vehicles and Deep-Sea Research. Mar. Technol. Soc. J. 33, 65–73 (1999).

4. AUVAC. Configurations - AUVAC. Available at: http://auvac.org/explore-database/advanced-search. (Accessed: 22nd June 2018)