NL2015802B1

NL2015802B1 - Method of and system for hauling a marine equipment unit, a marine equipment unit and a carrier.

Info

Publication number: NL2015802B1
Application number: NL2015802A
Authority: NL
Inventors: Pastor Chad; Kinnear Stephen; Sonnier Carl; Neil Thame Alick; Scholtens Marco
Original assignee: Fugro N V
Priority date: 2015-11-17
Filing date: 2015-11-17
Publication date: 2017-06-02
Also published as: GB201809092D0; GB2559710A8; WO2017086780A1; US20180327057A1; GB2559710A; NO20180834A1; AU2016357679A1

Abstract

The present document describes a method of hauling an equipment unit from the water onto a carrier. The carrier comprises a hauling ramp, which is arranged for being extended from a loading area into the water. The carrier further includes a first winch, and a suspension structure arranged for being extended outside the carrier over the water and over the hauling ramp. The suspension structure comprises a second winch. The method comprising the steps of: releasing, by the equipment unit, a hauling buoy. The hauling buoy is connected to a tow line extending from the equipment unit, and to a lift line extending from a lifting point on the unit. The method comprises a further step of recovering the hauling buoy from the water, connecting the tow line to the first winch and connecting the lift line to the second winch. Then, the equipment unit is hauled by towing it onto the hauling ramp using the first winch, while simultaneously guiding the equipment unit using the second winch. The method is in particular useful for hauling of an autonomous underwater vehicle (AUV) during bad weather conditions at sea. The document also describes the equipment unit and a system for hauling that can be installed on a carrier, as well as a carrier comprising such a system.

Description

Title: Method of and system for hauling a marine equipment unit, a marine equipment unit and a carrier.

Field of the invention

The present invention is directed at a method of hauling an equipment unit from the water onto a carrier. The invention is further directed at a marine equipment unit, at a marine equipment hauling system for use onboard a carrier and at a carrier comprising such a system.

Background

The present invention is in particular directed at the hauling of marine equipment onboard a vessel or other water based carrier under rough marine conditions, such as high seas and strong winds. A large variety of underwater sensor and survey systems is nowadays used for performing many different tasks. One class of equipment is for example formed by autonomous underwater vehicles (AUV’s) that are used for survey of the sea bed, e.g. to search for mining locations, wrecks, or other features, or to map the bottom surface structures or subsurface structures and elements. Such AUV’s are often equipped with sensitive and costly sensor equipment, such as interferometric sonar, multibeam echo systems, underwater camera’s, analysis systems and data communication systems for communicating with a surveyor vessel from where the AUV is operated. Other AUV’s, e.g. for defense systems, may be equipped with different equipment.

Although the AUV’s themselves may be operated well even under harsh conditions at sea, a drawback and limiting factor is formed by their method of deployment and recovery. In particular the recovery of an AUV in combination with the sensitivity of the costly onboard equipment forms a drawback, because the AUV may easily get damaged due to uncontrolled movement as a result of rough conditions at sea. Therefore, the deployment and recovery of AUV’s is often limited to mild conditions at sea, e.g. at wind force up to 5 Beaufort. This means that under worse conditions, e.g. wind forces of 5 Beaufort and up, survey teams have to wait for weather conditions to improve, or where possible apply different survey techniques that are not always available. As will be understood, there are many area’s where the weather conditions are more commonly to be classified as rough than mild. A good example is the southern ocean, e.g. greater than 40 degrees south of the Earth's equatorial plane. This area consists almost entirely of oceans, and waves can travel very long stretches eastward, without encountering any land. Hence, the seas are known to be high in this region. Other examples are the Bering sea, known for its bad and unpredictable weather conditions.

Summary of the invention

In view of the above, it is an object of the present invention to provide a recovery method for hauling marine equipment back onboard a carrier, that can be performed independent of the weather conditions, e.g. even at rough weather and sea conditions or at wind forces above 5 Beaufort.

To this end, there is provided herewith a method of hauling an equipment unit from the water onto a carrier, the carrier including a first winch arranged for towing the equipment unit towards the carrier, wherein the carrier further comprises a suspension structure extending, or arranged extending outside the carrier, the suspension structure comprising a second winch, the method comprising the steps of: releasing, by the equipment unit, a hauling buoy, wherein the hauling buoy is connected to a tow line extending from the equipment unit, and wherein the hauling buoy is further connected to a lift line extending from a lifting point on the equipment unit; recovering the hauling buoy from the water; connecting the tow line to the first winch and connecting the lift line to the second winch different from the first winch; and hauling the equipment unit by towing the equipment unit towards the carrier using the first winch, and by guiding the equipment unit using the second winch.

The method of the invention uses marine equipment that releases or launches a hauling buoy connected to two lines: a tow line and a lift line. The tow line is then used for towing the marine equipment unit towards the carrier, while the lifting line is connected to an additional winch (i.e. the second winch) that is used for providing an additional force on the lifting point of the equipment unit to enable guiding thereof during hauling onboard. The hauling may be performed with help of a hauling ramp installed on the carrier, or the equipment unit may be hauled directly on board the carrier. The carrier may be a vessel, e.g. a survey ship, or any other water based carrier, such as an offshore platform or structure. The equipment unit, e.g. an AUV, may now more easily be prevented from crashing onto the carrier or, in case a hauling ramp is used, accidentally end up underneath the hauling ramp. Close to the carrier, under influence of high or violent waves, the AUV may easily crash into the hull of the carrier. Additional guidance provided by means of the second winch, or even a controlled operation of the first and second winch, enables to prevent undesired contact between the equipment and any part of the carrier. Thereby, the method of recovering the equipment unit of the present invention can be performed under rough conditions at sea.

In accordance with some embodiments, the guiding of the equipment unit during the hauling step is performed by operating the second winch such as to maintain tension in the lift line exerted onto said lift point. Even without actually lifting the marine equipment unit out of the water, enough tension can be applied via the second winch to better control the movement of the unit in the water. For example, the nose of an AUV can be lifted upward to prevent it from ending up underneath the ramp. As another example, pulling the lifting point of the AUV will aid in maintaining it balanced and aligning the AUV in front of the ramp. This thereby allows to safely haul the marine equipment unit onto the hauling ramp.

In some embodiments, the suspension structure further comprises a guiding structure suspending from the suspension structure, wherein the guiding of the equipment unit comprises receiving, by the guiding structure, the equipment unit for aligning the equipment unit in a preferred alignment direction using the guiding structure. The guiding structure may for example comprise or be formed by a saddle cradle comprising one or two alignment beams. An equipment unit, e.g. an AUV, can be pulled by means of the second winch against the saddle cradle such that it is kept aligned with the one or more alignment beams. The equipment unit may thereby be brought in a preferred alignment direction to allow safe hauling thereof onto the hauling ramp. In some of these embodiments, the guiding structure suspends from the suspension structure by means of an extendable and retractable telescopic arm, the guiding structure being fixed to an end of the telescopic arm. The telescopic arm is a rigid structure suspending from the suspension structure. As result of the rigidity, once the marine equipment unit is being held by the guiding structure, its lateral position with respect to the hauling ramp and the ship is fixed. The height can be varied by means of the telescopic arm. As mentioned, in accordance with some embodiments of the present invention, the guiding of the equipment unit during the hauling step is performed by operating the second winch such as to lift at least a part of the equipment unit to a level above a loading plane of the hauling ramp during said hauling step.

The suspension structure may for example be an A-frame, launch boom or even an onboard crane. In this respect, it is noted that an A-frame or launch boom including a telescopic arm negates the height disadvantages of such structures as compared to cranes, while providing simplicity, stability and strength. Moreover, A-frames are more commonly available on existing vessels than cranes.

The hauling method may be applied for enabling recovery of all kinds of marine equipment. However, the method is in particular suitable for hauling sensitive equipment. Therefore, in accordance with some embodiments, the equipment unit is at least one element of a group comprising: an autonomous underwater vehicle, a para vane or water kite, or an air gun array. These units have also in common that their shape is cylindrical or bullet shaped, having a front or nose section and enabling alignment with a saddle cradle as described above. The vulnerability of such equipment calls for a more controlled hauling method as described herewith in connection with the present invention.

In accordance with a second aspect of the invention, there is provided -for use in a hauling method in accordance with the first aspect - a marine equipment unit comprising a front part and a housing, the equipment unit comprising hauling buoy, a tow line and a lift line, wherein the hauling buoy is launchable for releasing thereof by the equipment unit, the marine equipment unit further comprising a control unit for operating said launching of the hauling buoy, and wherein one end of the tow line and one end of the lift line is connected to the hauling buoy for being releasable with the hauling buoy, and wherein the tow line is further connected to the front part of the equipment unit, and the lift line is further connected to a lifting point on the housing of the equipment unit.

The marine equipment unit of the invention launches the tow line and the lift line by launching of the hauling buoy. By recovering the buoy from the carrier, the tow line can be connected to the first winch of the ship, and the lift line can be connected to the second winch. The tow line is connected to the front part of the equipment unit, e.g. the nose of a cylindrical or bullet shaped equipment unit, such as to enable easy towing thereof. As a result of the streamlined shape of the cylindrical or bullet shaped unit, the towing aligns the equipment unit behind the ship inline with the hauling ramp. The second winch connects to the lift line. The lift line may be connected to an upper part of the AUV, e.g. to a connection eye, for example above the center of gravity of the unit. The AUV may even have two lifting points, and the lifting line may split to connect to both lifting points. The lifting point or points may be displaceable to the back or front of the AUV to allow setting a slight unbalance that may cause the AUV to slant back slightly such as to bring the nose in an upward position. The hauling buoy may, prior to launching, be arranged on any suitable part of the housing of the equipment unit. In some embodiments, the hauling buoy is located at the front part, but in other embodiments the hauling buoy may located on the side or even towards the back of the equipment unit. For example, the hauling buoy may also be located at the location where the lift line connects to the AUV, e.g. near (above) the center of gravity.

In accordance with some embodiments, the hauling buoy is formed such as to close an opening in the housing, said opening providing access to a line storage cabinet inside the equipment unit wherein the tow line and the lift line are stored prior to release of the hauling buoy. In these embodiments, the tow line and lift line are safely stored inside the housing in the line storage cabinet, while the marine equipment unit is operated during normal operation in use. When the marine equipment unit is to be recovered, a command is issued to the marine equipment unit that triggers its control unit to deploy or launch its hauling buoy. This will deploy the tow line and the lift line that are connected to the hauling buoy. The lift line, when connected on the marine equipment unit on the housing, may during storage and before launch of the hauling buoy, be lead via the access opening of the line storage cabinet via the exterior of the marine equipment unit to the lifting point. This does not hinder normal operation of e.g. an AUV.

In accordance with some embodiments, the hauling buoy at least partly defines an outer shape of the front part of the marine equipment unit for complementing a shape defined by the housing. In particular, the shape of the marine equipment unit may be cylindrical or bullet shaped, the hauling buoy thereby preserving the streamlined shape. The marine equipment unit according to this aspect of the invention may for example be at least one element of a group comprising: an autonomous underwater vehicle, a para vane or water kite, or an air gun array unit.

In accordance with a third aspect of the invention, there is provided a marine equipment hauling system for use on a carrier and arranged for hauling of a marine equipment unit onboard the carrier, the system comprising a hauling ramp, wherein the hauling ramp extends or is arranged for being extended into the water, the system further including a first winch arranged for being connected to a tow line of the marine equipment unit for towing of the equipment unit towards the hauling ramp, a suspension structure extending or arranged for being extended over the water and over the hauling ramp, and a second winch located on the suspension structure and arranged for connecting thereof to a lift line of the marine equipment unit, wherein the system comprises a control unit for controlling operation of the first winch and the second winch in a cooperative manner such as to haul the equipment unit by towing the equipment unit onto the hauling ramp using the first winch, while simultaneously guiding the equipment unit using the second winch. The marine equipment hauling system in accordance with this aspect can be used for performing a recovery method as described above, in accordance with the first aspect.

In accordance with embodiments thereof, the suspension structure comprises an extendable and retractable telescopic arm suspending from an in use upper part of the suspension structure, wherein a guiding structure is connected to an end of the telescopic arm, wherein the guiding structure is arranged for receiving the marine equipment unit for aligning thereof in a preferred alignment direction during hauling. The advantages of these embodiments have been described above. Alternatively, in accordance with some embodiments, the suspension structure comprises a slidable beam, wherein the second winch is installed on the slidable beam. By providing a slidable beam that extends at a sufficient height (e.g. 2 or more meters above the deck to allow passing underneath) parallel to the deck of the ship, the second winch can be used for example to lift the nose of an AUV such as to haul it onto the hauling ramp without crashing of the nose into the ramp.

In accordance with a further aspect, there is provided a carrier, such as a vessel or other structure, comprising a marine equipment hauling system in accordance with the second aspect, which is installed onboard of the carrier for enabling hauling of a marine equipment unit from the water.

Brief description of the drawings

The invention will further be elucidated by description of some specific embodiments thereof, making reference to the attached drawings. The detailed description provides examples of possible implementations of the invention, but is not to be regarded as describing the only embodiments falling under the scope. The scope of the invention is defined in the claims, and the description is to be regarded as illustrative without being restrictive on the invention. In the drawings:

Figures 1A to ID schematically illustrate a method of the present invention;

Figure 2 schematically illustrates a suspension structure for use in a hauling system in accordance with the present invention;

Figure 3 illustrates a vessel on which there is installed a hauling system in accordance with the invention, performing a method in accordance with the invention;

Figure 4 schematically illustrates an equipment unit, in particular an autonomous underwater vehicle, in accordance with the invention;

Figure 5 schematically illustrates an equipment unit, in particular an autonomous underwater vehicle, in accordance with the invention;

Figure 6 schematically illustrates a vessel on which there is installed a hauling system in accordance with another embodiment of the invention, performing a method in accordance with the invention.

Detailed description

Figures 1A through ID schematically illustrate a method in accordance with the present invention, for hauling an equipment unit 2 from the water onto a vessel 1. The vessel 1 has installed thereon a system for hauling equipment units such as autonomous underwater vehicles (AUV’s) 2 for recovery. Autonomous underwater vehicles such as equipment unit 2 can be used for a variety of different tasks, amongst which are investigation and survey of the sea floor. For example, an AUV 2 may be used search for mining locations, wreckage, geological underwater structures (e.g. volcanoes, abysses, etc.). Other tasks that may be performed using an AUV is to perform seismic surveys of sub-bottom structures, such as to find possible locations of oil and gas fields. Moreover AUV’s may be applied for all kind of defensive tasks.

To perform these tasks, the AUV 2 comprises a variety of sensor units, communication units, processing means and other sensitive equipment, which may easily be damaged or offset by undesired shocking or bumping of the AUV 2.

During mild weather conditions, the AUV can be recovered without much risk of getting damaged. However, when the weather conditions or conditions at sea become more rough (strong winds, high or unpredictable waves, or other complicating factors) the recovery of the AUV may easily result in damaging thereof, e.g. by uncontrolled crashing into the vessel during hauling. For this reason, use of an AUV is usually limited to those moments on which the conditions at sea are favorable. The disadvantage of this is that, especially in areas where rough conditions are common, the available time for performing a survey is limited or the total time for finalizing the survey may be considerable.

The recovery method, the recovery system, the equipment unit, and the assembly of the equipment unit and the system of the present invention, overcome this drawback by enabling recovery during more severe conditions at sea. Figures 1A to ID illustrate an embodiment of the method, the system installed on a ship, and an equipment unit, all in accordance with embodiments of the present invention. In figure 1A the ship 1 comprises a hauling ramp 9 that is to be used for bringing the AUV 2 on board of the ship 1. The system for hauling the AUV 2 comprises the hauling ramp 9, a suspension structure 10, a first winch 12, and a second winch 13. In addition, an operator unit (not shown) including a controller (not shown) may be installed on the ship for controlling operation of the above-mentioned parts of the hauling system. The operating unit may be installed on the bridge 5 of the ship 1 or on deck 4, and may include control buttons (not shown) for enabling the operating crew of the ship 1 to operate the hauling system.

In the situation of figure 1A, the AUV 2 is located just below the surface at a determined distance from the ship 1. From the deck 4, the hauling ramp 9 of the hauling system has been extended into the water as schematically illustrated by figure 1A. The suspension structure 10 has been lowered such as to extend over the water and over the hauling ramp 9, outside the ship 1. In particular, in accordance with the present invention, the suspension structure 10 extends outwards the vessel at a determined distance. This distance establishes a security zone that restricts the AUV from going below the vessel or its associated equipment (e.g., ramps, propellers, etc.). When the hauling system is not used, the suspension structure 10 is kept in a position such that no elements substantially extend outside the vessel. The suspension structure 10 may be a standard A-frame, Π-frame present on many ships, as in the embodiment illustrated, which may be held in the upright position when it is not used. The suspension structure 10 may alternatively be a slidable boom, which may be retracted when it is not in use. For hauling purposes, in the figure, the suspension structure 10 has been tipped over slightly such as to extend outside the ship 1. The AUV 2 comprises a nose section including a hauling buoy 15 forming part of the nose. The AUV 2 is a bullet shaped autonomous vessel that can be controlled remotely from the ship 1. In the situation illustrated in figure 1A, the crew of the ship 1 may command, by operating the control buttons of the hauling system, the AUV 2 to launch the hauling buoy 15.

Next, in figure IB, the AUV 2 has received the command to launch the hauling buoy 15, and the hauling buoy 15 has been launched into the water as illustrated. Attached to the hauling buoy 15 there is a tow line 18 and a lift line 19. The tow line 18 and the lift line 19, in the embodiments of figures 1A to ID, connect both to the front part of the AUV. For example, both may be connected to one or more reels within the AUV or to a connection eye in or on the front part. As will be illustrated later in respect of other embodiments, the tow line 18 and the lift line 19 may alternatively be connected to different parts of the AUV. To recover the AUV 2, the crew of the ship 1 will have to recover the hauling buoy 15, e.g., by fishing it out of the water. This may be performed in many different ways and the skilled person will appreciate how to perform this step.

In figure 1C, the hauling buoy 15 has been recovered, and the tow line 18 and lift line 19 have been separated from one another. The tow line 18 is now connected to the first winch 12 while the lift line 19 is connected the second winch 13 of the hauling system. To recover the AUV 2, the first winch 12 is operated for towing the AUV 2 towards the ship 1. Furthermore, the second winch 13 will also be operated for putting tension on the lift line 19 such as to control the motion of the AUV 2 during hauling. This is illustrated in figure ID.

In figure ID the tow line 18 has towed the AUV 2 with its nose section over the hauling ramp 9. To prevent the AUV 2 from accidentally ending up underneath the hauling ramp 9 and/or crash into the ship 1, the second winch 13 has performed a controlled pulling of the lift line 19 such as to raise the nose section sufficiently and maintain the AUV 2 within a distance from the vessel 1, such distance is determined by the length that the suspension structure 10 extends outside the vessel 1. The nose section of the AUV 2 may be raised (note that raising may be performed while the AUV remains in the water) to a height level above the hauling ramp 9 to prevent it from ending up underneath. Although the illustration of figure ID is a two-dimensional representation of the hauling, it will be appreciated that the AUV 2 may also experience sideways movement (the direction into and out the paper). As will be appreciated, any sideways movement may be controlled to some extent by pulling the nose section of the AUV 2 upwards as illustrated in figure ID. Therefore, the AUV 2 can be recovered from the water, even under severe conditions such as strong winds or high waves that are frequently experienced at full sea, e.g. in arctic and sub-arctic regions. In a preferred embodiment, the tow line 18 is pulled towards the vessel 1 while keeping the AUV 2 under the surface of the water, once the AUV 2 is close to the vessel 1 (and, more preferably, below the suspension structure 10) the lift line 19 is tensioned in order to pull the nose of the AUV 2 over the surface. Given that the hauling ramp 9 is slightly under the surface, this method of recovering would prevent the AUV from accidentally getting under the hauling ramp 9.

In figure 2 a suspension structure 10 for use in a hauling system in accordance with the present invention is schematically illustrated. The suspension structure 10 is somewhat different from the embodiment illustrated in figures 1A through ID. In figure 2, the suspension structure 10 comprises a telescopic arm 25 that can be used for even better controlling undesired motion of an AUV 2 during recovery thereof. The suspension structure 10 comprises the second winch 13 at its upper end. The second winch 13 comprises a reel 20 from which a winch line 30 or chain suspends. At the end of the winch line 30 a connection unit 31, e.g. a carbine hook or other suitable connection, may be provided to allow a connection of the lift line 19 of the AUV 2. The telescopic arm 25 may comprise a plurality of telescopic sections 27A, 27B and 27C that allow extension and retraction of the telescopic arm upward and downward. The telescopic arm 25 extends from the suspension structure 10 via a rotatable connections which allows the telescopic arm to remain aligned with the directional gravity in use. At the end of the telescopic arm 25, a saddle cradle 28 may be attached thereto. The saddle cradle 28 is a supporting construction that may comprise one or more alignment beams that allow aligning of the AUV 2 therewith, such as to keep it in a preferred alignment direction. The connection between the saddle cradle 28 and the telescopic arm 25 may be such that the saddle cradle 28 may be tilted in a preferred orientation and be kept fixed in that orientation.

Figure 3 illustrates a vessel 1 comprising a hauling system in accordance with the present invention, wherein the suspension unit 10 illustrated in figure 2 is applied. The vessel 1, as schematically illustrated in figure 3, performs a method in accordance with the present invention for recovering equipment unit 2 (again an AUV) from the water. The suspension unit 10 has been lowered (and, therefore, maintaining the distance between the vessel and the lifting point on the AUV) by rotating the suspension unit 10 in the direction illustrated by the double arrow. Thereby the suspension unit 10 is extended over the waterline and over the hauling ramp 9 (even outside the hauling ramp 9).

The AUV 2 is illustrated at the moment of recovering of the AUV 2 on the hauling ramp 9; the hauling buoy 15 (not visible in figure 3) has already been launched, and the tow line 18 and lift line 19 have been connected respectively to the first winch 12 and the second winch 13. Moreover, in the position illustrated in figure 3, the lift line 19 has been pulled using the second winch 13 such as to pull the AUV 2 with its outer housing onto the alignment beams of saddle cradle 28. By keeping the lift line 19 under tension, alignment between the saddle cradle 28 and the AUV 2 is maintained. The telescopic arm 25 has been extended such as to maintain the AUV 2 in a desired height position. Note that the lift line 19 on the AUV connects to a connection point more or less above the center of gravity (i.e. mass center) of the AUV. This allows to keep the AUV in gravitational balance while it is being pulled by the lift line 19 into the saddle cradle 28.

Also visible in figure 3 are the actuator 33 and the hydraulic cylinder 35 that are used for controlling rotation of the suspension unit 10 such as to extend it over the water. As will be appreciated, the suspension unit 10 illustrated in figure 2 and 3, being hydraulically operated by means of the actuator 33 and cylinder 35, form just one embodiment of the suspension unit that can be used in combination with the present invention. Another embodiment may be formed of the slide-able beam construction that may be linearly extended by sliding the beam from the ship 1 over the water at a desired or fixed height, with the second winch installed on the slide-able beam. This embodiment is not illustrated, but does fall within the scope of the present invention.

Figure 4 schematically illustrates an equipment unit 2 in accordance with the present invention. The equipment unit 2 is an autonomous underwater vehicle (AUV) having a bullet shape such as to streamline the unit for underwater motion. Instead of being bullet shaped, the equipment unit 2 may be cylinder shaped or differently shaped without departing from the present invention. The equipment unit 2 comprises a control unit 45 which controls a plurality of different sensors and apparatuses on board. Just as an example, some possible sensor units and apparatuses are illustrated in figure 4. The AUV 2 of figure 4 for example comprises a sophisticated sonar unit 46 comprising a sonar transceiver 47 for scanning the sea bottom. The AUV 2 also comprises an underwater camera 49 and a communication unit 50 including an antenna 51 for enabling communication with a commanding ship 1. The rear part of the equipment unit 2 comprises the tailfin 53 that may be movable for maneuvering the AUV 2, and (not shown) a propulsion engine and means for enabling underwater motion.

In addition to the above, the equipment unit 2 comprises a launching unit 42 for launching the hauling buoy 15 upon receipt of a launching command from the ship 1. For example, the launching unit 42 may be spring-loaded to enable the launching. By launching the hauling buoy 15 into the water, tow line 18 and lift line 19 will be released as well. When the hauling buoy 15 is not launched, and the AUV is operated during normal operation under water, the tow line 18 is stored e.g. on a reel 38 in the line storage cabinet 37. The lift line 19 is also stored in the line storage cabinet 37, e.g. bundled in a clew 39 for storage. In the embodiment of figure 4, the lift line 19 is connected with one or more lift points 40 and led over the housing 36 of the AUV 2 toward the line storage cabinet 37.

Figure 5 illustrates the same AUV 2 of figure 4 when it is attached to the first winch 12 and the second winch 13 respectively. The tow line 18 extends towards the first winch 12 (not shown). The lift line 19 extends to the second winch 13 (not shown).

Figure 6 illustrates a further alternative embodiment that may be applied in case the carrier (e.g. survey ship) may not comprise an extendable hauling ramp. The use of a hauling ramp is completely optional and it is one of the advantages of the present invention that it may be applied without a hauling ramp. In the embodiment of figure 6, no hauling ramp is present and the AUV 2 is lifted out of the water using the suspension structure 10. During lifting, the telescopic arm 25 may be retracted while the second winch 13 keeps tension on the lift line to hold the AUV 2 in the saddle cradle 28. The suspension structure 10 is rotated to its upright position by hydraulic actuator 33. Thus, the AUV is lifted from the water. Note that also in figure 6, the tow line 19 is connected to the AUV at a connection point located above the center of gravity (i.e. mass center) of the AUV, to keep the AUV in gravitational balance while it is being pulled into the saddle cradle 28 by the lift line.

At the choice of the skilled person, the tow line 19 may be connected to the AUV at another suitable position, rather than to the front part or above the center of gravity. Also, the hauling buoy may be located at any suitable position on the AUV. For example, if the design of the AUV required sensors or other equipment to be located in the nose, the hauling buoy may be positioned behind the front part or near the point where the lift line connects to the AUV.

The present invention has been described in terms of some specific embodiments thereof. It will be appreciated that the embodiments shown in the drawings and described herein are intended for illustrated purposes only and are not by any manner or means intended to be restrictive on the invention. It is believed that the operation and construction of the present invention will be apparent from the foregoing description and drawings appended thereto. It will be clear to the skilled person that the invention is not limited to any embodiment herein described and that modifications are possible which should be considered within the scope of the appended claims. Also kinematic inversions are considered inherently disclosed and to be within the scope of the invention. In the claims, any reference signs shall not be construed as limiting the claim. The term 'comprising' and ‘including’ when used in this description or the appended claims should not be construed in an exclusive or exhaustive sense but rather in an inclusive sense. Thus the expression ‘comprising’ as used herein does not exclude the presence of other elements or steps in addition to those listed in any claim. Furthermore, the words ‘a’ and ‘an’ shall not be construed as limited to ‘only one’, but instead are used to mean ‘at least one’, and do not exclude a plurality. Features that are not specifically or explicitly described or claimed may be additionally included in the structure of the invention within its scope. Expressions such as: "means for ...” should be read as: "component configured for ..." or "member constructed to ..." and should be construed to include equivalents for the structures disclosed. The use of expressions like: "critical", "preferred", "especially preferred" etc. is not intended to limit the invention. Additions, deletions, and modifications within the purview of the skilled person may generally be made without departing from the spirit and scope of the invention, as is determined by the claims. The invention may be practiced otherwise then as specifically described herein, and is only limited by the appended claims.

Claims

A method of overtaking a unit of equipment from the water on a carrier, the carrier comprising a first winch adapted to drag the equipment unit to the carrier, wherein the carrier further comprises a suspension structure which extends, or is adapted to extend to extend outside the carrier, the suspension structure comprising a second winch, the method comprising the steps of: releasing by the equipment unit a catch-up buoy, wherein the catch-up buoy is connected to a tow line extending from the equipment unit, and wherein the catch-up buoy further is connected to a hoist line that extends from a hoist point on the equipment unit; retrieving the catch-up buoy from the water; connecting the tow line to the first winch and connecting the hoist line to the second winch other than the first winch; and overtaking the equipment unit by dragging the equipment unit toward the carrier with the help of the first winch, and guiding the equipment unit with the help of the second winch.

The method of claim 1, wherein guiding the equipment unit during the overtaking step is performed by operating the second winch such that tension is maintained in the hoist line exerted at the hoist point.

The method of claim 1 or 2, wherein the suspension structure further comprises a guide structure suspended from the suspension structure, wherein guiding the equipment unit comprises receiving the equipment unit for aligning the equipment unit in a preferred alignment direction using the guidance structure .

The method of claim 3, wherein the guide structure is suspended from the suspension structure by means of an extendable and retractable arm, the guide structure being attached to one end of the arm.

A method according to any one of the preceding claims, wherein the carrier comprises a catch-up ramp, in which the catch-up ramp extends, or is adapted to extend, from a loading area on the support in the water, wherein the guidance of the equipment unit during the step of overtaking is performed by operating the second winch for hoisting at least a portion of the equipment unit to a level above a loading surface of the catching ramp during the overtaking step.

A method according to any one of the preceding claims, wherein the second winch is operated for hoisting the equipment unit out of the water during towing.

A method according to any one of the preceding claims, wherein the equipment unit is at least one element from a group comprising: an autonomous underwater vehicle, a paravan or water kite, an autonomous surface vehicle, a towed vehicle or an air gun array.

A marine equipment unit comprising a front part and a housing, the equipment unit comprising a catch-up buoy, a tow line and a hoist line, wherein the catch-up buoy is launchable for release therefrom by the equipment unit, the marine equipment unit further comprising a control unit for operating the launch of the catching buoy, and wherein one end of the tow line and one end of the hoist line is connected to the catch buoy to be released with the catch buoy, and wherein the tow line is further connected to the front part of the equipment unit, and the hoist line is further connected to a hoisting point of the equipment unit.

A marine equipment unit according to claim 8, wherein the hoist point to which the hoist line is connected is located at the front part of the equipment unit.

A marine equipment unit according to claim 8, wherein the hoist point to which the hoist line is connected is located substantially at the center of gravity of the equipment unit.

A marine equipment unit according to claim 8, wherein the catch-up buoy is configured to close an opening in the housing, the opening providing access to a cable storage cabinet in the equipment unit or an external tow storage bag in which the tow line and the cable line are stored prior to releasing the catch-up buoy.

A marine equipment unit according to claim 11, wherein the catch-up buoy at least partially defines an external shape of the front part of the marine equipment unit to complement a shape defined by the housing.

A marine equipment unit according to any of claims 8-12, wherein the marine equipment unit is at least one element from a group comprising: an autonomous underwater vehicle, a paravan or water kite, an autonomous surface vehicle, a towed vehicle or an air gun grouping unit.

A marine equipment catch-up system for use on a carrier and adapted to overtake a marine equipment unit on board the carrier, the system comprising a first winch adapted to be connected to a towing line of the marine equipment unit for towing the equipment unit toward the catch-up ramp, suspension structure which extends or is arranged to extend above the water, and a second winch which is located on the suspension structure and is adapted for connecting it to a hoist line of the marine equipment unit, wherein the system comprises a management unit for managing the operation of the first winch and the second winch in a cooperative manner for overtaking the equipment unit by dragging the equipment unit in the direction of the carrier with the aid of the first winch and guiding the equipment unit with the aid of a second winch.

A marine equipment catching-up system according to claim 14, wherein the suspension structure comprises an extendable and retractable arm, such as a telescopic arm, a sliding beam, or a crane arm, wherein the extendable and retractable arm extends from an in-use upper part of the suspension structure, in which a guide structure is connected to an end of the arm, wherein the guide structure is adapted to receive the marine equipment unit for aligning it in a preferred alignment direction during overtaking.

A marine equipment catching-up system according to claim 14, wherein the suspension structure comprises a slidable beam or trolley system, and wherein the second winch is installed on the slidable beam or trolley system.

A carrier comprising a marine equipment catching system according to any of claims 14-16 installed on board the carrier for releasing a marine equipment unit from the water.