Autonomous underwater system for a 4D environmental monitoring

An autonomous underwater system for environmental monitoring including a multidisciplinary underwater station including onboard instrumentation, at least one autonomous modular underwater vehicle movable inside an area to be monitored along an assigned route, and at least one external instrumental modulus which can be connected to the vehicle, wherein the multidisciplinary underwater station includes a docking area, an interface system, an equipping system for supplying the vehicle with instrumental moduli, and a management system.

The present invention relates to an autonomous underwater system for continuous, in-situ, long-term and wide-range environmental monitoring, in particular for measuring environmental parameters close to the seabed and along the water column.

Surveying environmental parameters in an underwater environment represents a particularly important activity, above all close to risk areas such as oil extraction areas.

In order to perform environmental monitoring in the sea, periodical measurement campaigns are traditionally effected, with the deployment of instruments and collection of samples for subsequent laboratory analyses. This approach is clearly insufficient for guaranteeing a complete understanding of the dynamics of phenomena underway and is not capable to detect the occurrence of anomalous events in useful time.

When a continuous observation capacity is required, permanent underwater observatories are used which, by means of suitable instrumentations, collect data on the surrounding environment.

This accurate approach is useful for the monitoring of parameters relating to long-term environmental phenomena such as earthquakes, tsunamis, volcanism, but which cannot be easily used for wide-range monitoring.

In order to overcome this drawback, autonomous underwater vehicles, known in the state of the art as AUVs (Autonomous Underwater Vehicle) are being increasingly used.

These vehicles are generally equipped with propulsion and driving systems for underwater movement, and various measurement instruments for collecting data relating to the underwater environment.

If suitably programmed, AUVs allow underwater explorations on predefined areas without human intervention for several hours.

The duration of these explorative campaigns, however, is influenced by the degree of energy autonomy of the vehicle which, at the end of each survey, must reach a base to download the information collected and recharge the energy reserves.

These bases or stations are generally situated on the surface to facilitate human operations, in particular for a simpler management of data parking, reconfiguration and recharging of the vehicles.

Underwater stations are also known in the state of the art, which allow the vehicle to be managed in an underwater environment.

In particular, these stations allow the energy recharging of the vehicle, reconfiguration of the same for the subsequent survey and uploading/downloading of the data collected by the instruments present onboard.

This technique has led to an improvement in the degree of autonomy of the vehicles which can therefore continue to explore the seabed for a theoretical indefinite period of time.

Patent application US 2009/0095209 describes an underwater station equipped with means for receiving an AUV, charging its batteries and exchanging information with it.

This solution allows long explorations completely handled in an underwater environment.

A further example of an underwater station for AUVs is represented in patent application US 2009/0114140 which describes a system for supporting underwater operations. This system allows the handling of an AUV, ROV (Remotely Operated Vehicle) and HROV (Hybrid Remotely Operated Vehicle) from an energy, communication and maintenance point of view.

In particular, when these vehicles enter into contact with this system, they can receive energy for explorations, exchange information, i.e. the data collected by the instruments onboard, and undergo maintenance.

This system, however, as also the current techniques known in the art, do not allow the explorative mission of the vehicle to be adapted to the specific requirements of the moment, and in particular they do not allow the reconfiguration of the instrumental equipment of the vehicle in an underwater environment.

This aspect requires that, for each type of exploration, vehicles must be equipped a priori and ad hoc.

This lack of flexibility of the methods and systems known in the art, limits the autonomy of use of current explorative solutions in an underwater environment.

The Applicant has found that by using underwater stations for energy recharging and exchange of communications with these vehicles, the necessity of creating independent and autonomous systems capable of effecting long-term and wide-range underwater explorative campaigns, can only be partly satisfied.

In the state of the art, the use is also known of autonomous underwater vehicles constructed according to modula which allow a certain set-up flexibility of the vehicle. This technique allows to achieve AUVs which are suitable to meet various operative requirements.

Patent application WO 03/059734, for example, describes an AUV constructed with mechanical modula which, when combined with each other, form an AUV which satisfies the specific explorative requirements of the moment.

In this case, the assembly of the various modula forming the AUV is effected manually in the open air and not in an underwater environment.

With the autonomous underwater vehicles currently known, a timely and autonomous modulability of AUVs directly in an underwater environment, is not possible. The necessity of re-emerging the AUV from the depths to be able to add or modify the instruments onboard, represents a considerable waste of time, which greatly limits the operative flexibility of these systems.

The Applicant has therefore conceived an autonomous underwater vehicle capable of housing one or more external instrumental modula that can be interchanged directly onsite and without requiring the manual intervention of an operator, thus allowing a complete adaptability of the means to the specific explorative requirements of the moment.

An objective of the present invention is to overcome the drawbacks mentioned above and in particular to provide an autonomous underwater system for effecting long-term monitoring, in continuous, onsite and with a wide range of parameters relating to the marine environment, consisting of a multidisciplinary underwater station and at least one autonomous underwater vehicle, cooperating with each other to allow various kinds of environmental explorations.

In particular, for monitoring the environmental impact of offshore activities, characterizing unexplored sites, supporting the management of polluted areas, monitoring the integrity of structures installed in underwater environments and verifying the possible intrusion of third-parties in an area to be monitored.

A further objective of the present invention is to provide an autonomous underwater vehicle for various kinds of environmental explorations that can be modulated by means of external instrumental modula which can be connected to the main body of the vehicle.

Further objective of the present invention is to provide a multidisciplinary underwater station equipped with means and instruments for performing various types of environmental surveys.

Another objective of the present invention is to provide a multidisciplinary underwater station equipped with means for handling and equipping autonomous modular underwater vehicles.

Yet another objective of the present invention is to provide a method for four-dimensional environmental monitoring capable of detecting data in relation to time along the three dimensions of space.

These and other objectives of the present invention are achieved by providing an autonomous underwater system for four-dimensional environmental monitoring as specified in claims1,18and40.

Further characteristics of the autonomous underwater system for four-dimensional environmental monitoring are object of the dependent claims.

With reference to the figures, these show an autonomous underwater system for four-dimensional environmental monitoring, indicated as a whole with100.

A first object of the present invention relates to an autonomous underwater system for environmental monitoring100comprising a multidisciplinary underwater station101equipped with onboard instrumentation202, at least one autonomous, modular underwater vehicle102movable inside an area to be monitored107along an assigned route106and at least one external instrumental modulus206which can be connected to said vehicle102, wherein said multidisciplinary underwater station101is characterized in that it comprises:at least one docking area204suitable for accommodating said vehicle102;at least one interface system220suitable for communicating with said docked vehicle102;at least one equipping system207suitable for providing said docked vehicle102with said instrumental modula206and comprising at least one parking area208suitable for the storage of said modula206;at least one management system201suitable for managing the functionalities of said station101.

Said area to be monitored107can be a generic underwater area involved in offshore activities in which there are extraction and interface infrastructures of reservoirs103, pipelines and cables105connected with a surface structure104and whatever is normally present in an underwater area involved in oil and gas activities.

In particular, the surface structure104connected by means of cables and pipelines105with the underwater area, can be a floating platform or a structure attached to the seabed.

In a preferred embodiment of the present invention, said autonomous modular underwater vehicle102inspects said area to be monitored107by moving along the assigned route106according to tracks pre-programmed or autonomously calculated by the same vehicle.

In particular, said assigned route106can consist of straight trajectories and/or curved trajectories, routes at a constant and/or variable depth, preferably ranging from 0 to 1,500 meters.

In a preferred embodiment of the present invention, said multidisciplinary underwater station101comprises a metallic structure205, preferably made of an aluminium alloy, capable of resting on the sea bed by means of legs210having supporting feet212.

Said structure205allows the physical protection from accidental events of the instrumentation onboard202, instrumental modula206, underwater vehicle102when docked in the station101, and anything else contained in the station101.

Said structure205also allows the interface system220, the equipping system207, the management system201and also the various parts inside the multidisciplinary underwater station101, to be contained in its interior.

In a preferred embodiment of the present invention, said autonomous modular underwater vehicle102carries out monitoring campaigns in said area to be monitored107, collecting data on the submarine environment and on the integrity of the infrastructures operating therein, by means of instruments installed onboard the vehicle102and/or by means of said external instrumental modula206.

In a preferred embodiment of the present invention, said equipping system207provides said vehicle102with the most suitable instrumental modulus206for the purpose of the monitoring mission to be effected, according to the instructions received from said management system201.

In a preferred embodiment of the present invention, said external instrumental modula206are kept in a parking area208, present inside the structure205, equipped with electromechanical instruments (not illustrated) which allow the connection/disconnection of the modula206from the station.

In particular, said instrumental modula206are stored in said parking area208and when connected to said parking area208, can be recharged, configured, programmed and run by means of the management system201.

In a particular embodiment of the present invention, said parking area208can be an automated system, preferably a revolver (FIG. 4b), which handles the instrumental modula206for loading/unloading operations from the underwater vehicle102, on the basis of the explorative mission programmed or driven by remote control.

Once said instrumental modula206have been disconnected from said parking area208, they can be positioned on the underwater vehicle102by means of electromechanical means (not illustrated) present in the equipping system207.

In a preferred embodiment of the present invention, said multidisciplinary underwater station101comprises onboard instrumentation202, which can be fixed209or movable213, suitable for measuring at least one of the following parameters:temperature;electric conductivity;concentration and/or saturation percentage of dissolved oxygen;turbidity;concentration and/or profile of the particulate in suspension;fluorescence (relating, for example, to chlorophyll and CDOM);pH;concentration of dissolved gases (for example CH4, H2S, CO2);concentration of hydrocarbons (for example PAH);concentration of nutrients (for example, nitrates, phosphates, silicates, ammonia);concentration of trace metals;velocity profile and direction of the sea current;height and direction of the waves;tide level;sound wave pressure (for example acoustic monitoring of the presence and passage of marine species such as cetaceans by means of hydrophones);biological responses of living organisms (for example the opening/closing frequency of the clams of specifically instrumented molluscs).

In a preferred embodiment of the present invention, said fixed onboard instrumentation209is fully contained inside a structure205, and comprises at least one sensor214and at least one local control unit215suitable for managing all the functionalities of the sensors, for example acquisition, power, control, etc.

In a preferred embodiment of the present invention, said movable onboard instrumentation213is different with respect to the fixed onboard instrumentation209in that it can move the measurement instrumentation away from the station101thanks to a floating unit217, containing in its interior at least one sensor221and a cable218which prevents its disconnection from the station101.

Said cable218, when wound by the action of a winch216, allows the floating unit217equipped with sensors221to be returned inside the station101for interface activities with the station101itself.

This vertical movement of the floating unit217allows the profiling of the water column, revealing, by means of the sensors contained therein, data on the underwater environment at different heights from the sea bottom.

In a preferred embodiment of the present invention said multidisciplinary underwater station101comprises, inside said structure205a management system201suitable for managing the functionalities of the station, in particular the communication between the various instrumentations onboard, the interface with a surface structure104, the distribution and regulation of the electric feeding, the monitoring of the technical parameters of the system (status, alarms, etc.), the collection and storage of the data obtained by the various instruments, the configuration and selection of the external instrumental modula206and the programming of the monitoring missions.

In particular, said management system201can be connected with a surface structure104by means of at least one umbilical cable211, which allows the transmission of data and/or energy feeding of the station101.

In a preferred embodiment of the present invention, said multidisciplinary underwater station101comprises, inside said structure205, a docking area204suitable for allowing the entrance/exit and temporary docking of the vehicle102inside the underwater station101.

The entrance and exit of the vehicle102in this docking area204are facilitated by suitable guiding devices, selected from: acoustic positioning systems, television cameras, lights, proximity sensors219, entrance bulkheads.

In particular, said guiding devices forming part of said docking area204, can be connected to the management system201.

Preferably, said docking area204may comprise a horizontal plane on which the vehicle102rests after entering the station101, and an opening203in the horizontal plane through which the equipping system207connects the instrumental modula206to the docked vehicle102.

It should be pointed out that when the autonomous modular underwater vehicle102is positioned in the docking area204, said interface system220of said station allows at least one of the following operations to be effected:data communication between vehicle102and station101;recharging of the batteries312of the vehicle102.

In a preferred embodiment of the present invention, said interface system220consists of direct connection means such as connection sockets or contact elements.

In an alternative embodiment, said interface system220between said station101and said vehicle102consists of wireless communication means.

In this particular solution, the batteries312of said vehicle102can be recharged by means of electromagnetic induction systems.

It should be pointed out that these induction systems are known in the art and available to experts in the field without imposing additional constraints with respect to normal routine work.

A second object of the present invention relates to an autonomous modular underwater vehicle102equipped with onboard measurement sensors311, comprising at least one main thruster302, at least one auxiliary thruster for fine positioning305,306,307, a hull301, at least one electronic control modulus313, at least one energy reserve312, al least one connection system308, characterized in that it comprises means317for attaching at least one instrumental external modulus206, wherein said instrumental external modulus206is equipped with at least one measuring sensor314.

In a preferred embodiment of the present invention, said main thrusters302and fine positioning thrusters305,306,307have a propeller and are operated by at least one motor310inside the hull301, said motor310is preferably electric.

In particular, the side thrusters305, front thrusters306and upper/lower thrusters307serve for a fine displacement of the vehicle102in space, giving this a wide manoeuvring and positioning capability.

The manoeuvring of the vehicle102can be further facilitated by one or more rudders303.

In a preferred embodiment of the present invention, said hull301is made of a non-corrodible material, preferably a composite material.

The internal components which must operate in air, such as the electronic control modulus313and the energy reserve312, are housed in one or more watertight containers309preferably made of titanium and capable of tolerating high pressures, preferably up to 300 bar.

In a preferred embodiment of the present invention, said onboard measuring sensors311effect measurements of at least one of the following parameters:temperature;electric conductivity;saturation concentration and/or percentage of dissolved oxygen;turbidity;fluorescence (relating to chlorophyll and/or CDOM);pH;dissolved gas concentration (for example CH4, H2S, CO2);hydrocarbon concentration (for example PAH).

In particular, said onboard measuring sensors311positioned inside the hull301can get in contact with seawater by means of one or more openings304present on the hull301itself.

In a preferred embodiment of the present invention, said attaching means317may be means activated electromechanically and allow the hooking of the modulus206to the vehicle102.

Said vehicle102can comprise communication means (not illustrated) with the external instrumental modulus206, allowing a bidirectional exchange of information for synchronizing the data collected by the various sensors, in addition to a possible energy exchange.

In a preferred embodiment of the present invention, said autonomous underwater modular vehicle102comprises a connection system308capable of being interfaced with an interface system220for the exchange of communications between the vehicle102and the underwater station101. Said connection system308also allows the recharging of the energy reserves on board312.

In a preferred embodiment of the present invention, said autonomous underwater modular vehicle102can comprise an electronic control modulus313which manages the functioning and control of the thrusters, the sensors311onboard, the energy reserves312, the attaching means317, the connection system308and possible communication means with the external instrumental modulus206.

In a particular embodiment of the present invention, said energy reserve312is an electric battery, preferably a lithium ion or lithium polymer battery.

It should be pointed out that the vehicle can be produced with a hull301having a flattened form and in particular with a flat lower surface in order to facilitate the resting of the vehicle102on the multidisciplinary underwater station101or on the seabed.

In particular, when the vehicle102approaches the station101, the lower surface of the hull301can easily rest on the surface of the docking area204, allowing the equipping system207to intervene on the vehicle through the opening of203of the surface.

In a preferred embodiment of the present invention, said external instrumental modulus206equipped with measuring sensors314may comprise:connection means319;communication means320;a hull318;a control unit316.

In a particular embodiment of the present invention, said external instrumental modulus206comprises at least an inner energy source315, preferably an electric battery.

In a preferred embodiment of the present invention, the control unit316and energy source315can be contained in one or more watertight containers321positioned inside the hull318and capable of tolerating high underwater pressures.

Said watertight container321is preferably made of titanium.

It should be pointed out that said control unit316, said sensors314and said internal energy source315are contained inside said hull318for a better protection from possible impact and to ensure that the vehicle has an adequate hydrodynamicity. Said hull318is preferably made of a composite material or another non-corrodible material.

In a preferred embodiment of the present invention, said connection means319allow the hooking of the instrumental modulus206to the equipping system207of the underwater multidisciplinary station101or to the vehicle102, guaranteeing an integral coupling during the displacement of the vehicle102in the water.

In a particular embodiment of the present invention, said connection means319can be mechanical or electromechanical driven by said control unit316or consisting of suitably shaped grooves present on the hull318.

In a preferred embodiment of the present invention, said communication means320allow the exchange of information and/or the supply of energy with external structures such as the vehicle102or the equipping system207of the multidisciplinary underwater station101.

In a particular embodiment of the present invention, said communication means320allow the synchronization of the measurements effected by the sensors314with those effected by the sensors311onboard said vehicle102.

In a preferred embodiment of the present invention, said control unit316controls the functioning of the measuring sensors314, the regulation and distribution of the energy feed and the interface with the vehicle102.

In a preferred embodiment of the present invention, said measuring sensor314installed in said external instrumental modulus206can be selected from the following types of sensors:optical (photocameras, videocameras);acoustic (sonars, echo-sounders);automatic hydrocarbon analyzer;automatic phenol analyzer;automatic analyzer of trace metals;automatic analyzer of nutrients.

A third object of the present invention relates to a 4D environmental monitoring method, in an underwater environment, comprising a multidisciplinary underwater station101, according to the present invention, at least one external instrumental modulus206, according to the present invention, and at least one autonomous modular underwater vehicle102, according to the present invention, characterized by the following phases:selection and supply of at least one external instrumental modulus206to the autonomous modular underwater vehicle102by the multidisciplinary underwater station101;attaching of the external instrumental modulus206to the autonomous modular underwater vehicle102;departure of the autonomous modular underwater vehicle102and the external instrumental modulus206attached to it, from the multidisciplinary underwater station101;execution of the survey by the autonomous modular underwater vehicle102and external instrumental modulus206attached to it, along a trajectory predefined or calculated in real time on the basis of data measured by the sensors;execution of measurements and data collection on the underwater environment by the sensors present in the autonomous underwater vehicle102and in the external instrumental modulus206attached to it.return of the autonomous modular underwater vehicle102to the multidisciplinary underwater station101;download of data collected data by the underwater multidisciplinary station101;recharging of the batteries of the autonomous modular underwater vehicle102by the multidisciplinary underwater station101;docking of the autonomous modular underwater vehicle102inside the multidisciplinary underwater station101until the subsequent mission;measurement and data collection on the underwater environment by the instrumentation202onboard the multidisciplinary underwater station101;processing of the combination of data collected by the autonomous modular underwater vehicle102, the external instrumental modulus206and the instrumentation onboard202for the analysis of the underwater environment.

In a preferred embodiment of the present invention, said method allows environmental monitoring by correlating data collected at the moment of detection and the survey position.

In a preferred embodiment of the present invention, said data collected represent measurements of at least one of the following parameters:temperature;electric conductivity;saturation concentration and/or percentage of the oxygen dissolved;turbidity;concentration and/or profile of the particulate in suspension;fluorescence (relating for example to chlorophyll and CDOM);pH;concentration of dissolved gases (for example CH4, H2S, CO2);hydrocarbon concentration;nutrients concentration;concentration of trace metals;phenol concentration;velocity profile and direction of the sea current;height and direction of the waves;tide level;sound wave pressure (for example for the acoustic monitoring of the presence and passage of marine species such as cetaceans by means of hydrophones);biological responses of living organisms (for example the opening/closing frequency of the clams of specifically instrumented molluscs);optical and/or acoustic images, for example of the seabed and infrastructures being inspected.

In a preferred embodiment of the present invention, said trajectory selected can be autonomously identified by the management system201on the basis of pre-formulated maps or on the basis of processings effected in real time on the data collected, or, alternatively, it is imposed by a surface system (not illustrated) connected with the station101.

In a preferred embodiment of the present invention, said data collected in relation to time provide, after processing, an overall vision, i.e. a four-dimensional vision, of the underwater environment monitored.

EXAMPLE

An autonomous underwater system100was used for the purpose, positioned inside an area107involved in oil&gas activities, situated on the seabed according toFIG. 1, in which an autonomous modular underwater vehicle102moves along a route106defined a priori on the basis of the positioning of the infrastructures103and pipelines105that connect said infrastructures with the platform situated on the surface104.

During the explorative mission106, the autonomous modular underwater vehicle102acquires data relating to the sea environment and integrity of the infrastructures operating therein by means of the sensors installed onboard and/or present on the instrumental modulus206, returning, at the end of the mission, to the multidisciplinary underwater station101positioned on the seabed.

In particular, the area to be monitored with said autonomous underwater system100extends for about 4 km in width and 4 km in length and is situated at a depth of about 1000 meters.

The multidisciplinary underwater station101includes a metal structure205according toFIG. 2, which is firmly positioned on the seabed thanks to four supporting legs210provided with the same number of supporting feet212.

Various systems necessary for the functioning of the station are positioned inside said structure205, which has a base of 5×5 meters and a height of 3.5 meters. In particular, the station comprises a control system201which communicates, by means of an umbilical cable211, with the floating platform104.

This control system201sends information on the monitoring missions effected and receives information on the configuration of future missions.

The control system201also handles the distribution and regulation of the electric power received through the umbilical cable211from the surface structure.

The control system201also manages communication with the various onboard instrumentations, collecting the data measured and storing them before processing.

Said control system201also guarantees control of the various technical parameters of the system (status, alarms, etc.).

The station101contains in its interior two types of onboard instrumentation202, of the fixed type209and movable type213, which allow the measurement of various parameters of the underwater environment.

Some of the sensors used for the instrumentation onboard are indicated hereunder.

A conductivity, temperature and depth sensor for measuring the temperature, electric conductivity and parameters deriving therefrom (salinity, density, sound velocity). In particular, a CTD SBE-16 sensor of the company Seabird Electronics was used.

An optical type sensor for measuring the saturation concentration and/or percentage of the oxygen dissolved. In particular, a sensor model 4330F of the company AADI was used.

A sensor for measuring the turbidity by means of wavelengths in the blue zone. In particular, a sensor model ECO-NTU of the company WETLABS was used.

A sensor for the concentration and/or profile of the suspended particulate of the high-frequency acoustic type. In particular, a sensor model AQUAscat 1000 of the company Aquatec was used.

A fluorometer for measuring the fluorescence, for example of chlorophyll and CDOM. In particular, a fluorometer model ECO FL of the company WETLABS was used.

A pH measurement sensor. In particular, a sensor model SBE-27 of the company Seabird Electronics was used.

A sensor for measuring the concentration of dissolved methane. In particular, a sensor model METS of the company Franatec was used.

A sensor for measuring the hydrocarbon concentration was used. In particular, a sensor model HydroC of the company Contros was used.

A sensor for measuring the concentration of nutrients: nitrates, phosphates, silicates, ammonia. In particular, an onsite sensor nutrients model NAS3-X of the company Envirotech Instruments was used.

A sensor for measuring the concentration of trace metals such as Cu, Pb, Cd, Zn, Mn and Fe. In particular, an underwater voltammetric probe model VIP of the company Idronaut was used.

A sensor for measuring the velocity profile and direction of the sea current. In particular, a sensor Acoustic Doppler Current Profiler model Workhorse Monitor ADCP of the company RD Instruments was used.

A sensor for measuring the tide level. In particular, a high-pressure depth sensor of the series 8CB of the company Paroscientific was used.

A sensor for measuring the acoustic wave pressure. In particular, a hydrophone model TC-4042 of the company RESON was used.

A sensor for measuring the biological responses of molluscs. In particular a system developed by the company Biota Guard was used.

As far as the movable instrumentation213is concerned, this comprises a floating unit217made of a composite material, containing one or more measurement sensors. As the casing217is buoyant in water, it allows profiling along the water column.

Once these operations have been effected, an electric winch216rewinds the cable218which connects the floating unit217to the station101, repositioning the movable instrumentation213inside the structure205.

The fixed instrumentation209, on the contrary, is firmly constrained to the structure205, but can be substituted in the case of necessity by means of a normal underwater intervention using a ROV equipped with an adequate manipulating arm.

The station101contains inside the structure, a docking area204, according toFIGS. 2, 4aand5, comprising a horizontal plane having indicative dimensions of 4,000×2,000 mm capable of easily housing the autonomous modular underwater vehicle102.

Said docking area204also includes some instruments which operate to support the vehicle102to facilitate its positioning inside the station101. In particular, some acoustic positioning systems and proximity sensors219are installed in the docking area204, which detect the approaching of the vehicle102towards the area in question.

The docking area204also has an opening203in the horizontal supporting plane through which the external instrumental modula206are installed on the vehicle102.

On entering the station101, the vehicle102is positioned on the plane of the docking area204in a particular position which allows the equipping system207to easily operate on the vehicle102, through the opening of the plane203, for the parking and substitution of the external instrumental modulus206.

In particular, the equipping system207positions the instrumental modulus206detached from the vehicle102inside the parking area208and receives instructions from the control system201for removing a new external instrumental modulus206to be positioned on the vehicle102.

All the external instrumental modula206available are contained inside the parking area208, and in particular they are contained in a carousel system which, by rotating, facilitates the removal of the modulus206preselected for the monitoring mission to be effected; the remaining modula206remain connected to the carousel for the recharging and configuration operations.

Once the instrumental modulus206has been removed, the equipping system207brings the instrumental modulus in correspondence with the attaching means317present underneath the vehicle102and then effects the connecting operation of the external modulus206to the vehicle102.

The external instrumental modulus206used, has connection means319which protrude with respect to the hull318, as shown inFIG. 4c.

These connection means319allow the modulus to be connected to both the equipping system207and to the attaching means317of the vehicle.

In particular, the hull318of the external instrumental modulus206is made of a composite material.

The components inside the modulus which must operate in air, such as the control unit316and the internal energy source315, are contained in a watertight container321capable of tolerating high pressures.

The external instrumental modulus206has a cylindrical form with flat ends and in some configurations reaches 1,500 mm in length and 250 m in diameter.

When the modulus206has been correctly positioned by the equipping system207, the attaching means317block the external instrumental modulus206to the vehicle102.

Only subsequently the modulus206is released by the electromechanical means of the equipping system207, returning to rest position.

The instrumental modulus206also has a suitable connection, which acts as a communication means320for the exchange of information and data with the vehicle102or with the underwater station101.

This connection allows the exchange of information at the input and output with the modulus206.

In particular, when the modulus206is connected to the vehicle102by the attaching means317, the communication means320comes into contact with the connection means (not illustrated) of the autonomous modular underwater vehicle102.

The instruments311and314are synchronized through this connection so as to obtain a univocal measurement in relation to the time.

The autonomous modular underwater vehicle102used has a hull301having a flattened form to provide a better support on the seabed and on the plane204of the station101and includes a series of thrusters which allow the means to be moved in three dimensions (FIG. 3b). In particular, there are two main thrusters302positioned at the stern of the vehicle102, whereas there are two rear305and four front306auxiliary side thrusters which are positioned on the two sides of the vehicle102. Finally, there are two upper and lower auxiliary thrusters307for each side, positioned at the prow and stern of the vehicle102. All the thrusters are activated by electric motors.

The combination of all the thrusters gives the vehicle the maximum flexibility of movement and positioning in space and also the possibility of horizontally stabilizing the vehicle102while running.

The thrusters are fed with rechargeable lithium ion batteries312capable of guaranteeing at least 8 hours of autonomy.

The rudder303also facilitates the manoeuvring and establishment of the trajectories to be followed during the monitoring explorations106.

The onboard sensors311of the vehicle102get in direct contact with seawater by means of the openings304present on the hull301.

The vehicle102reaches the following dimensions: 3,750×1,500×750 mm (length×width×height).

The onboard sensors311of the vehicle102and the measurement sensors314of the external instrumental modulus206allow numerous parameters to be measured in relation to the time and position. In particular the vehicle is equipped with onboard instrumentation for measuring the following parameters:temperature, electric conductivity and pressure, by means of the probe CTD SBE-49 of SeaBird,turbidity by means of the sensor ECO NTU of WETLABS,fluorescence for chlorophyll and CDOM by means of the sensor ECO FL of WETLABS,concentration of dissolved oxygen and saturation percentage by means of the sensor 4330F of AADI,volumetric concentration of PAH hydrocarbons by means of the sensor HydroC of CONTROS.

The external instrumental modulus206connectable to the vehicle and selectable, depending on the mission program, envisages the following solutions:water sampling modulus, equipped with the automatic sampler Aqua Monitor of the company Envirotech Instruments,Observation modulus, to be used for leakage detection or for the visual inspection of underwater infrastructures such as, for example, flowlines, manifolds, PLEMS etc. It is equipped with instruments for monitoring the following parameters/data:images and videos revealed by means of high-resolution colour videocameras INSPECTOR HD produced by the company ROS (Remote Ocean Systems);methane concentration revealed by means of the sensor METS of the company Franatech;volumetric concentration of PAH hydrocarbons revealed by means of the sensor HydroC of the company CONTROS;the presence of dye tracers revealed by means of the optical measurement system Bowtech using a LED-540 lamp and a monochromatic telecamera 600TVL.Polluttant analysis modulus, for the in-situ measurement of the following parameters:concentration of trace metals by means of the probe VIP of the company Idronaut;concentration of specific hydrocarbons by means of one or more analyzers;concentration of phenols by means of an analyzer;concentration of nutrients by means of the sensor NAS3-X of the company Envirotech Instruments.Acoustic surveys modulus using the synthetic opening sonar Prosas Surveyor produced by Applied Signal Technology Inc.

Finally, it is clear that the system thus conceived can undergo numerous modifications and variants, all included in the invention; furthermore, all the details can be substituted by technically equivalent elements. In practice, the materials used, as also the dimensions, can vary according to technical requirements.