Autonomous underwater vehicle recovery system

Abstract

AUTONOMOUS UNDERWATER VEHICLE RECOVERY SYSTEM An autonomous underwater vehicle recovery system which is attachable at a first end to a surface vessel The recovery system including: a plurality of resiliently deformable gripping members, each gripping member being configured, when gripping a portion of an autonomous underwater vehicle, to have an asymmetrical restoring bias; and a conveying mechanism, configured to urge the autonomous underwater vehicle gripped by one or more of the plurality of gripping members towards the first end of the recovery system. [Figure 2] Figure 2

Description

AUTONOMOUS UNDERWATER VEHICLE RECOVERY SYSTEM

[0001] This application claims priority from GB2418797.3, filed 20 December 2024, the contents and elements of which are herein incorporated by reference for all purposes.TECHNICAL FIELD

[0002] The present disclosure relates to an autonomous underwater vehicle recovery system, a surface vessel, a recovery wheel, and a method of recovering autonomous underwater vehicles.BACKGROUND

[0003] The use of autonomous underwater vehicles is of increasing interest, with applications such as seismic surveying causing an increased focus in this area. For example, an autonomous data acquisition might include a large number of autonomous nodes located on respective autonomous underwater vehicles, each carrying sensors for sensing or measuring and collecting data.

[0004] However, such fleets of autonomous vehicles may comprise quite a large number of physically large vehicles. The vehicles require recovery onto a surface support vessel, for example to replace or charge batteries and other consumables and perform repair operations. Conventionally, cranes have been used to recover autonomous underwater vehicles from the sea onto a support vessel. However, this can be costly, dangerous, and time consuming. A crane might only lift one vehicle at a time, and require constant supervision and direction from an operator. This bottleneck in the deployment and recovery of autonomous underwear vehicles throttles the scale at which they may be deployed.

[0005] The present disclosure was arrived at in light of the above considerations.SUMMARY

[0006] Accordingly, in a first aspect, embodiments of the invention provide an autonomous underwater vehicle recovery system, attachable at a first end to a surface vessel, the recovery system including: a plurality of resiliently deformable gripping members, each gripping member being configured, when gripping a portion of an autonomous underwater vehicle, to have an asymmetrical restoring bias; and a conveying mechanism, configured to urge the autonomous underwater vehicle gripped by one or more of the plurality of gripping members towards the first end of the recovery system.

[0007] Such a recovery system allows for the safe and efficient recovery of autonomous underwater vehicles from the water onto a surface vessel.

[0008] Each gripping member may have a stronger restoring bias in a direction towards the first end of the recovery system, and a weaker restoring bias in a direction in a direction away from the first end of the recovery system. In some examples, when fitted to the surface vessel, the first end (attached to the surface vessel) may be higher than the opposing end of the recovery system. Such an asymmetrical restoring bias allows the autonomous underwater vehicle to be effectively held in the recovery system against gravity whilst allowing it to easily move towards the first end of the recovery system.

[0009] The restoring bias may be non-linear as a function of deformation of the gripping members. For example, the restoring bias may have a step change after a threshold deformation amount of the respective gripping member. This can allow the gripping members to easily move to a position in which the autonomous underwater vehicle is held, but then to hold the vehicle in position once it is gripped.

[0010] Each gripping member may include a plurality of stopping elements, which are configured to be brought into contact with one or more supports when a force is applied to the gripping member, the contact providing a further restoring bias component. The support(s) may be others of the plurality of stopping elements.

[0011] Each gripping member may be formed at least in part from an elastomer. The elastomer may be UV-resistant and compatible with total immersion in sea water (for example, by being made of silicone).

[0012] The conveying system may include one or more rotating shafts, with a plurality of recovery wheels disposed long the or each rotating shaft at axially separated points, each recovery wheel including a set of deformable gripping members circumferentially disposed around the wheel. Each recovery wheel may include an even number (for example two, four, six, or eight) of gripping members circumferentially disposed around a portion of the or each wheel. They may be equally circumferentially disposed around the wheel.

[0013] The conveying mechanism may be a slat conveyor, each slat of the slat conveyor including one or more of the gripping members. The slat conveyer may be configured to move the or each gripping member along a stadium shaped path through the recovery system. There may be a plurality of gripping members, disposed across a width of the slat in the slat conveyor.

[0014] The conveying mechanism may be further operable to move an autonomous underwater vessel away from the first end. For example, it may be configured or operable to run in reverse so as to move an autonomous underwater vehicle from the surface vessel into the

[0015] A second end of the recovery system, distal to the first, may be connected to one or more flotation or buoyancy aids.

[0016] In a second aspect, embodiments of the invention provide a surface vessel, including the recovery system of the first aspect. The recovery system is attached, at the first end, to the surface vessel, with a second distal end being located in the water. The recovery system as used in the second aspect may have any one, or any combination insofar as they are compatible, of the optional features as set out with reference to the first aspect.

[0017] In a fourth aspect, embodiments of the invention provide a recovery wheel for use in the recovery system of the first aspect (and including any one, or any combination insofar as they are compatible, of the optional features set out with reference thereto), wherein the recovery wheel includes a plurality of resiliently deformable gripping members disposed around a circumference of the recovery wheel, each gripping member being configured, when gripping a portion of an autonomous underwater vehicle, to have an asymmetrical restoring bias.

[0018] In a fifth aspect, embodiments of the invention provide a method of recovering an autonomous underwater vehicle from a body of water using the recovery system of the first aspect, wherein the method comprises conveying an autonomous underwater vehicle gripped by one or more of the plurality of resiliently deformable gripping members towards the first end of the recovery system using the conveying mechanism.

[0019] The invention includes the combination of the aspects and preferred features described except where such a combination is clearly impermissible or expressly avoided.BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Fig. 1 shows a recovery wheel for a recovery system;

[0021] Fig. 2 shows a recovery system;

[0022] Fig. 3 shows an alternative recovery system; and

[0023] Fig. 4 shows a surface vessel to which is attached a recovery system.DETAILED DESCRIPTION

[0024] Aspects and embodiments of the present invention will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilledin the art.

[0025] Fig. 1 shows a recovery wheel 100 for a recovery system. The wheel includes a plurality, in this example, six, resiliently deformable gripping members 102a-f which are arranged around and connected to a central hub 106. The circumferential distance between adjacent pairs of resiliently deformable gripping members is the same around the wheel. Each of the resiliently deformable gripping members extends radially away from the central hub 106, and in this example they extend away in a curved manner. The radial extent of each of the resiliently deformable gripping members is the same, and they have substantially identical forms. The central hub 106 includes a toothed region 108 for engagement with a drive gear.

[0026] Each of the resiliently deformable gripping members has a central region 110, which is provided as a curved strip portion extending away from the central hub 106. On a first surface of the curved strip portion are a series of concave regions 112, and on a second opposing surface of the curved strip portion are a series of protruding stops 104a, 104b. The protruding stops are at least partially, and in some examples predominantly, circular in crosssection and may have an outer profile which at least partially matches a corresponding one of the concave regions in a circumferentially adjacent resiliently deformable gripping member. Some of the protruding stops include an initial projection, which has a substantially uniform cross-section and which extends in a circumferential direction away from the curved strip portion. This initial projection gives way to the circular cross-section region, providing a generally cylindrical geometry. In this example, a radially outermost protruding stop includes a circumferentially extending ramp portion which is tangential to a point on the circular crosssection region of the stop. A radially innermost protruding stop can be provided as a partial cylinder embedded in the central hub 106. In the example shown, four protruding stops are provided, generally equally spaced in the radial direction away from the hub 106. However, more or fewer protruding stops and / or concave regions 112 may be provided depending on the desired asymmetry of the restoring bias.

[0027] When a force is applied against the first surface of the curved strip portion (in the figure, in a clock-wise direction) the resiliently deformable member will bend such that radially adjacent protruding stops 104a and 104b at least will contact one another. This contact then resists further deformation. Similarly, the concave regions 112 lessen the resistance to deformation in the opposite direction (in the figure, in a counter-clockwise direction) due to the missing material. In this way, an asymmetric restoring bias can be provided for each of the resiliently deformable gripping members. The protruding stops 104a, 104b also allow for the restoring bias provided thereby to be stepped in profile. The restoring bias may increase linearly with a first gradient on initial deformation, and then with a second gradient once one or more of the protruding stops are in contact with one another. Thus the restoring bias provided by them may be non-linear over the range of available deformation.

[0028] Said another way, the recovery wheel (which may be referred to as a compliant elastomer wheel), conforms to the shape of an autonomous underwater vehicle as it lands on it. However, when installed as an assembly of many wheels it also provides stiffness to stop the vehicle from slipping away. The resiliently deformable gripping members (also referred to as protrusions or fingers) provided around the circumference of the wheel are compliant in one direction tangential to the wheel axis of rotation but are relatively stiff in the other direction (and relatively stiff parallel to the wheel axis of rotation). The protrusions are made from an elastomer, which is able to sustain repeated high-strain rates in its elastic zone. This allows the resiliently deformable gripping members to flex in the desired directions, and the geometry of the material can also provide the relative stiffness in the other directions. The elastomer should be UV-resistant, and also compatible with total immersion in sea water (e.g., silicone).

[0029] Each of the protrusions has a main body, projecting from a central region (e.g., the wheel attached to the shaft). The main body includes one or more cut-outs on a first side, which weaken the restoring bias on that side. The main body may be arcuate, in that it may not extend directly radially from the central region. On a second side, the main body includes one or more stopping elements (e.g., cylinders) which protrude from a side of the body and engage with one another when the main body is bent to further resist deformation in that direction (and so provide a non-linear restoring force).

[0030] Such a recovery wheel allows for the more secure conveying of vehicles from the water to a surface vessel (and vice versa) where the relative movement between the conveyer / vessel and the vehicle (as well as wave loading on the vehicle or recovery system) can make recovery difficult. It also resists the vehicle being able to slip backwards on the conveyer, and resist the vehicle slipping transversely.

[0031] Fig. 2 shows a recovery system 200. The recovery system includes a plurality of drive shafts 204 extending laterally across the recovery system, and the drive shafts themselves are coupled to a central drive mechanism (e.g., electric motor or similar). At opposing longitudinal ends of the drive shafts a support frame 201 is provided. It is one end of this support frame which may be attached to the surface vessel, and the other end of this support frame may be connected to a respective flotation aid 206a or 206b (for example, buoys floating on the surface attached to the support frame by a cable or chain). The flotation aids may be configured such that they maintain the second end in a relatively neutral position in the water (e.g., not on the surface, and equally not directly pointed towards the seabed).

[0032] Along each drive shaft are a plurality of recovery wheels 202 of the type discussed in relation to Fig. 1 . These engage with gears on the drive shaft via their respective toothed regions 108, and so when the drive shaft is rotated the recovery wheels (and so the resiliently deformable gripping members) rotate also. An autonomous underwater vehicle 250, can therefore land or beach itself on the recovery system 200 and thereafter be conveyed towards the surface vessel by rotation of the drive shafts.

[0033] In this way, the recovery system 200 resembles and functions like a conveyor system to remove vehicles from the ocean. It is shown recovering an autonomous underwater vehicle (AUV), but could also be used to recover other marine objects including other vehicles (such as surface vehicles, and autonomous surface vehicles). It achieves this by being partially submerged, with one end (the inlet) beneath the surface, such that a vehicle can land on the conveyor. The other end of the conveyor (the outlet) is attached to the vessel to which the vehicles are being recovered. The recovery system (also referred to as a conveyor) is an assembly of a plurality of compliant wheels that can grab the vehicle and advance it up the conveyor, from the inlet to the outlet, as the wheels turn.

[0034] Multiple wheels can be fitted to a shaft and rotated together, and multiples of these shafts are assembled into a recovery system (aka a conveyor system). This allows a vehicle to land on the conveyor, and easily deflect the protrusions forward (in the direction of the wheel as it turns), but backwards sliding will be resisted by the protrusions which are relatively stiff when bending in the opposite direction due to their geometry (and / or material property). Further, the protrusions are relatively stiff in a direction parallel to the axis of wheel rotation (along the shaft), which means that transverse motions of the vehicle can be resisted. In this example, the wheels are spaced (e.g., equidistantly) from one another along the same shaft, with gaps to allow sea water to pass through, and thereby reduce the effects of wave loading. Of course the wheels could be spaced non-equidistantly along the axial direction. The wheels are installed such that successive wheels on the same shaft are installed at an angle half that of the angle between two protrusions on a given wheel. Other angles may be chosen, so that the circumferential position of the protrusions varies as a function of axial position along the shaft. The shafts are also installed so that the wheels on adjacent shafts are staggered, e.g., the plane of one wheel is halfway between the planes of two wheels on the adjacent shaft.

[0035] Fig. 3 shows an alternative recovery system 300. It includes a plurality of protrusions 302 (of the type discussed above, but shown schematically), fitted to the slats 304 of a slat conveyor. The mounting of the conveyor is not shown, but the lower end is (in use) partially submerged. This can be achieved by fixing the lower ends to buoys via cables. In both examples shown in Figs. 2 and 3, multiple conveyors can be arranged in series to lessen the angle of approach as a vehicle mounts the conveyor. In Fig. 3, alternating slats are provided with the protrusions. However, each slat may be provided with protrusions. The recovery system 300 may share features in common with the recovery system 200 insofar as they are compatible (such as the staggered nature of protrusions on adjacent slats).

[0036] Fig. 4 shows a surface vessel 400 to which is attached a recovery system 200, 300. The first end of the recovery system 200, 300 is attached to supports on the surface vessel 400. The second, opposing end, of the recovery system is attached to buoys 402, 404 (for example, via chains or a cable). This allows the second end of the recovery system to be submerged.

[0037] While the disclosure has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the disclosure set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the disclosure.

[0038] In particular, although the methods of the above embodiments have been described as being implemented on the systems of the embodiments described, the methods and systems of the present disclosure need not be implemented in conjunction with each other, but can be implemented on alternative systems or using alternative methods respectively.

[0039] The features disclosed in the description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the disclosure in diverse forms thereof.

[0040] While the disclosure has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the disclosure set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the disclosure.

[0041] For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations.

[0042] Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

[0043] Throughout this specification, including the claims which follow, unless the context requires otherwise, the word “comprise” and “include”, and variations such as “comprises”, “comprising”, and “including” will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0044] It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” one particular value, and / or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it will be understood that the particular value forms another embodiment. The term “about” in relation to a numerical value is optional and means for example + / - 10%.

Claims

CLAIMS1 . An autonomous underwater vehicle recovery system, attachable at a first end to a surface vessel, the recovery system including: a plurality of resiliently deformable gripping members, each gripping member being configured, when gripping a portion of an autonomous underwater vehicle, to have an asymmetrical restoring bias; and a conveying mechanism, configured to urge the autonomous underwater vehicle gripped by one or more of the plurality of gripping members towards the first end of the recovery system.

2. The recovery system of claim 1 , wherein each gripping member has a stronger restoring bias in a direction towards the first end of the recovery system, and a weaker restoring bias in a direction away from the first end of the recovery system.

3. The recovery system of claim 1 or claim 2, wherein the restoring bias is non-linear as a function of deformation of the gripping members.

4. The recovery system of any preceding claim, wherein each gripping member includes a plurality of stopping elements, which are configured to be brought into contact with one or more supports when a force is applied to the gripping member, the contact providing a further restoring bias component.

5. The recovery system of any preceding claim, wherein each gripping member is formed at least in part from an elastomer.

6. The recovery system of any preceding claim, wherein the conveying mechanism includes one or more rotating shafts, with a plurality of recovery wheels disposed along the or each rotating shaft at axially separated points, each recovery wheel including a set of deformable gripping members circumferentially disposed around the wheel.

7. The recovery system of claim 6, wherein each recovery wheel includes an even number of gripping members circumferentially disposed around a portion of the or each wheel.

8. The recovery system of any of claims 1 - 5, wherein the conveying mechanism is a slat conveyor, each slat of the slat conveyor including one or more of the gripping members.

9. The recovery system of claim 8, wherein the slat conveyer is configured to move the or each gripping member along a stadium shaped path through the recovery system.

10. The recovery system of claim 8 or 9, wherein there are a plurality of gripping members disposed across a width of each slat in the slat conveyor.11 . The recovery system of any preceding claim, wherein the conveying mechanism is further operable to move an autonomous underwater vessel away from the first end.

12. The recovery system of any preceding claim, wherein a second end of the recovery system, distal to the first, is connected to one or more flotation aids.

13. A surface vessel, including the recovery system of any preceding claim.

14. A recovery wheel for use in the recovery system of any of claims 1 - 12, wherein the recovery wheel includes a plurality of resiliently deformable gripping members disposed around a circumference of the recovery wheel, each gripping member being configured, when gripping a portion of an autonomous underwater vehicle, to have an asymmetrical restoring bias.

15. A method of recovering an autonomous underwater vehicle from a body of water using the recovery system of any of claims 1 - 12, wherein the method comprises conveying an autonomous underwater vehicle gripped by one or more of the plurality of resiliently deformable gripping members towards the first end of the recovery system using the conveying mechanism.

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