US20070283871A1

US20070283871A1 - Underwater remotely operated vehicle

Info

Publication number: US20070283871A1
Application number: US11/805,413
Authority: US
Inventors: Collin Millum; Gordon Durward
Original assignee: Sub Atlantic Ltd
Current assignee: Sub Atlantic Ltd
Priority date: 2004-11-23
Filing date: 2007-05-23
Publication date: 2007-12-13
Also published as: NO20073127L; GB0425694D0; WO2006056765A1; EP1819589A1

Abstract

An underwater vehicle having at least one thruster that is pivotally mounted on the vehicle. Preferred embodiments comprise a remotely operated vehicle (ROV) with a thruster in each of four corners. Each thruster may be pivoted during use in order to direct the thrust in the optimum direction to move the ROV in the desired direction. Embodiments of the present invention are more efficient than conventional ROVs which utilise fixed thrusters.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §§119, 120 of Patent Cooperation Treaty Application Serial No. PCT/GB2005/004493, filed Nov. 23, 2005, and entitled “Underwater Remotely Operated Vehicle,” as well as United Kingdom Patent Application Serial No. 0425694.7, filed Nov. 23, 2004, and entitled “Underwater Remotely Operated Vehicle,” the disclosures of which are incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to a vehicle, and particularly to an underwater vehicle such as a remotely operated vehicle commonly called an ROV. ROVs are remote-controlled submersible vehicles often used for subsea tasks such as conducting repairs or inspections to underwater equipment.
Most ROVs are electrically powered via an umbilical from a control ship, which supplies power to onboard thrusters. The thrusters are generally in the form of impellers able to operate in forward and reverse directions and are usually contained within a housing or cowling fixed to the corners of the ROV. The thrusters are generally fixed at 45° with respect to the sides to direct their thrust through apertures in the front, rear or sides of the ROV.

INTRODUCTION OF THE INVENTION

According to the present invention there is provided an underwater vehicle having at least one thruster that is pivotally mounted on the vehicle. In exemplary form, the vehicle has a number of thrusters that are pivotally mounted. For example, four thrusters, one at each corner of a generally rectangular vehicle, can be pivotally mounted to the vehicle and the attitude of the thrusters can be variable so as to direct the thrust at various angles with respect to the vehicle. The attitude of the thrusters is optionally variable during use of the thrusters.
In exemplary form, the thrusters are contained within the boundaries of a frame of the vehicle, and are arranged to direct thrust through apertures in the frame.
In exemplary form, the attitude of the thrusters can be varied by a limited amount, for example by up to 40° to 50°, although a greater amount of variability in the thrusters can be provided with some embodiments. In such embodiments with greater variability for thruster attitude, the frame and/or the apertures for directing thrust can be larger to accommodate the wider ranges of variability.
In exemplary form, a variable attitude thruster is disposed at each corner of the vehicle.
In exemplary form, a control system centrally controls the attitude of all the variable attitude thrusters on the vehicle, co-ordinating their attitudes to focus the overall thrust of the vehicle in a particular desired direction.
In certain embodiments of the invention, the thrusters can be mounted on pivot bosses with stops or rebates to control the maximum deflection of individual thrusters, and mechanical linkages such as bars or rods can link the thrusters to a central control bar that can be actuated (e.g. rotated) in order to adjust the attitude of all of the thrusters simultaneously. This is an advantage as the overall thrust of the vehicle can be adjusted by actuating the single control bar to adjust the direction of thrust of all adjustable attitude thrusters, and thereby centrally focus the overall thrust of the vehicle.
In other embodiments, the attitude of the thrust can be centrally controlled by electronic means, for example by semi-automatic electronic systems.
In exemplary form, the underwater vehicle is a remotely operated vehicle.
In exemplary form, the remotely operated vehicle comprises a camera and at least one grappling arm.
The thrusters can typically pivot in a single plane, such as a horizontal plane of the ROV, for example the plane of the deck of the ROV. Other planes of the ROV parallel to this can also be used. In some embodiments, the thrusters can pivot in a different, non-horizontal plane.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:
FIG. 1 is a perspective view of a vehicle according to the invention;
FIG. 2 is a view from beneath the FIG. 1 vehicle, showing the thrusters in a 45° orientation with respect to the front-to-rear axis of the vehicle;
FIG. 3 shows a similar view to FIG. 2 with thrusters in a 25° orientation;
FIG. 4 shows a view from beneath similar to FIG. 2, with the thrusters in a 65° orientation;
FIG. 5 is a perspective view of a vehicle showing a control system for controlling the attitude of the thrusters, with the thrusters in a 45° orientation;
FIG. 6 is a plan view (from above) of the FIG. 5 arrangement;
FIG. 7 is a perspective view of a vehicle showing a control system for controlling the attitude of the thrusters, with the thrusters in a 250 orientation;
FIG. 8 is a plan view (from above) of the FIG. 7 arrangement;
FIG. 9 is a perspective view of a vehicle showing a control system for controlling the attitude of the thrusters, with the thrusters in a 65° orientation; and
FIG. 10 is a plan view (from above) of the FIG. 9 arrangement.

DESCRIPTION OF ONE OR MORE EMBODIMENTS OF THE INVENTION

The exemplary embodiments described herein relate to vehicles, and particularly to underwater vehicles. While an exemplary embodiment of the invention is described herein, it should be understood that this exemplary embodiment does not limit the scope of the invention.
Referring now to the drawings, a remotely operated vehicle (ROV) has a generally rectangular shape and comprises a frame having port and starboard sides 5, 6 arranged parallel to one another, a base 7 and a deck 8. The deck 8 has a cutaway C at the front to accommodate a camera. Only certain parts of the frame and the thrusters of the vehicle are shown in the drawings to enhance understanding of the invention. Normally, the vehicle would be loaded with other parts and fittings that are not important to the invention and therefore are not shown in the drawings.
The deck 8 is supported by cross braces extending perpendicularly between the side frames 5, 6, and carries on its underside four thrusters disposed at each corner of the deck 8. Two thrusters are disposed at the front port and starboard corners, and are designated herein as FP and FS respectively. A further two thrusters are disposed at the rear port and starboard corners and are designated herein as RP and RS respectively. The thrusters are bi-directional, and can operate in forward or reverse mode. For example, the impeller of thruster RS can be rotated in a clockwise direction as shown by arrow A in FIG. 1 and when thus operated can direct thrust through the aperture 5R in the starboard side plate 5. Alternatively, the impeller can operate in the opposite direction and direct thrust through the rear of the vehicle.
A single thruster T is disposed in the plane of the deck 8 to provide horizontal thrust in either direction.
The corner thrusters are conventionally fixed in prior art devices at angles of 45° with respect to the perpendicular cross braces, and the vehicle is typically moved either forwards, backwards or to either side simply by coordinating the direction of thrust (i.e., forwards or reverse) of each of the fixed thrusters. For example, in order to move forwards (to the right as shown in FIGS. 1 to 4) all thrusters FS, FP, RS and RP direct thrust towards the rear of the vehicle (to the left as shown in the drawings). Thrusters RP and RS direct thrust through the rear opening of the vehicle, and the front thrusters FS and FP direct thrust through the apertures in the starboard and port side plates respectively. The resolved thrust applied to the whole vehicle is less than the sum of the thrust individually exerted by the four thrusters because of the 45° vectors of the individual thrusters, so although the vehicle moves forward, the total forward thrust is only 0.71 of the total thrust exerted by the four thrusters.
Likewise, when the vehicle is to move in reverse, the front thrusters FS and FP are driven in reverse to direct thrust through the front aperture of the vehicle, and the rear thrusters RS and RP are reversed to direct thrust through the apertures in the side plates 5 and 6 respectively.
Similarly, when the vehicle is to move toward its starboard side, the port thrusters RP and FP are driven through the apertures in the port side, and the starboard thrusters RS and FS through the rear and front apertures respectively. The situation is reversed when the vehicle is to be moved to the port side.
Inefficiencies arise in this system because of the fixed attitude of the thrusters. In the FIG. 1 embodiment of the present invention, the thrusters FS, FP, RP and RS are pivotally mounted on pivot bosses extending perpendicular to the lower surface of the deck 8 so that each thruster can move pivotally around the axis of the pivot boss in a plane that is parallel to the plane of the deck 8.
Referring now to FIG. 3, when the vehicle is to move against a strong head or tail current, the thrusters can be pivotally moved to the position shown in FIG. 3, in which their attitude with is more aligned with the front to rear axis of the vehicle. In the embodiment shown in FIG. 4, the thrusters have each been pivotally moved around the pivot bosses, so that the total thrust is more focussed along the central front-to-rear axis of the vehicle, parallel to the side frames 5, 6. In the embodiment shown, the thrusters are adjusted to an angle of 25° with respect to the front-to-rear axis of the vehicle.
When the thrusters of the vehicle are in the attitude as shown in FIG. 3, the vehicle can more easily move forwards against a strong head current by directing the rear thrusters RS and RP aft through the rear aperture, and the front thrusters FS and FP aft through the starboard and port side plates 5 and 6 respectively. Likewise when the vehicle is to be driven against a strong aft current, the directions of rotation of the impellers can be reversed, so that the thrust from the front thrusters FP and FS is directed through the front cavity of the vehicle, and the thrust from the rear thrusters RP and RS is directed through the port and starboard side plates 6 and 5 respectively.
If the vehicle is working in a strong sideways current it can be advantageous to direct the thrust that is exerted by the thrusters more directly against the path of the current. In such circumstances, the arrangement shown in FIG. 4 can be adopted, where the thrusters are all pivoted to adopt an angle of 65° with respect to the front-to-rear axis of the vehicle, thereby directing more of the force in the required direction. When the vehicle is to face a strong current coming from the starboard side, the starboard thrusters FS and RS can be arranged to direct the thrust through the front and rear apertures respectively, whereas the port thrusters RP and FP are arranged to direct more of their thrust through the apertures in the port side plate 6. Conversely when moving against a strong current from the port side, the directions of rotation of the impellers in the thrusters would be reversed, so that the port side thrusters FP and RP are arranged to direct thrust through the front and rear apertures, and the starboard thrusters FS and RS are arranged to direct thrust through the apertures in the starboard side plate 5.
Clearly, the thrusters can be adjusted to other angles, but the boundaries of useful adjustment for the angles are typically set by the architecture of the vehicle frame, since the thrust path from each thruster should ideally be free from obstruction by the vehicle frame, or the components of the vehicle. Therefore, the range of variation of the angles is usefully restricted to about 40° for each thruster. The thrusters can be set to individually different attitudes if desired.
Typically the attitude of the thrusters are controlled centrally through a control mechanism, ideally constituting a mechanical linkage between a central control arm and each thruster body. In preferred embodiments, the control arm is disposed centrally on the deck of the vehicle, and mechanical linkages such as tie rods or wires connect the central control rod to a fixing on each of the thruster bodies so that actuation (e.g. by rotation via a solenoid, a servo actuator, or a servo-gearbox) of the central control arm moves each of the control rods attached to a thruster, in order to pivot the thrusters in a co-ordinated manner. The central control arm can typically be actuated from the surface control room by the ROV operator, and can usefully be actuated independently of the other ROV controls, so as to select a “side current” setting where the control arm moves the thrusters simultaneously into the position shown in FIG. 4, with a 65° angle, or alternatively can be set to a “fore-aft current” setting in which the control arm moves each of the thrusters in concert into the position shown in FIG. 3.
FIGS. 5-10 show a typical control system for the attitude control. A servo-actuator 10 is attached to the underside of the deck 8. The servo-actuator 10 rotates a pin extending through the deck 8 and a disc 11 connected to the pin on the upper side of the deck 8. The rotating movement of the disc 11 is transmitted via linkage bars 13 and 14 to similar disc and pin arrangements 12 on each of the thrusters, so that rotation of the disc 11 by 20° simultaneously rotates the other discs by the same amount, but typically in opposite directions. FIGS. 5 and 6 show the control mechanism set to the 45° setting. When the ROV is to be moved against a strong head current, the solenoid rotates the disc 12 anticlockwise (when viewed in plan), which rotates the discs 12 on the thrusters FP and RS in the same direction, while rotating the discs 12 on the thrusters RP and FS in the opposite direction at the same time. This moves the thrusters into the 25° position as shown in FIGS. 7 and 8. When the ROV is to be moved against a strong sideways current, the solenoid is signalled from the control box to rotate the disc 11 clockwise to the position shown in FIGS. 9 and 10, which rotates the discs 12 on the thrusters FP and RS in the same direction, while rotating the discs 12 on the thrusters RP and FS in the opposite direction at the same time. This moves the thrusters into the 65° position as shown in FIGS. 9 and 10.
In other embodiments, the adjustment of the thruster attitudes can optionally be coordinated by an automatic mechanism linked to the thruster joy stick controls.
Modifications and improvements can be incorporated without departing from the scope of the invention.
Following from the above description and invention summaries, it should be apparent to those of ordinary skill in the art that, while the methods and apparatuses herein described constitute exemplary embodiments of the present invention, the invention contained herein is not limited to this precise embodiment and that changes may be made to such embodiments without departing from the scope of the invention as defined by the claims. Additionally, it is to be understood that the invention is defined by the claims and it is not intended that any limitations or elements describing the exemplary embodiments set forth herein are to be incorporated into the interpretation of any claim element unless such limitation or element is explicitly stated. Likewise, it is to be understood that it is not necessary to meet any or all of the identified advantages or objects of the invention disclosed herein in order to fall within the scope of any claims, since the invention is defined by the claims and since inherent and/or unforeseen advantages of the present invention may exist even though they may not have been explicitly discussed herein.

Claims

1. An underwater vehicle having a thruster that is pivotally mounted on the vehicle.

2. The underwater vehicle of claim 1, wherein the vehicle has a plurality of thrusters that are pivotally mounted on the vehicle.

3. The underwater vehicle of claim 1, wherein the pivotally mounted thruster is disposed proximate to a corner of the vehicle.

4. The underwater vehicle of claim 1, wherein the pivotally mounted thruster is pivotable in a single plane.

5. The underwater vehicle of claim 1, wherein the underwater vehicle comprises a frame, the frame defining at least one aperture, the thruster being contained within the frame and being arranged to direct thrust through the at least one aperture.

6. The underwater vehicle of claim 1, wherein an attitude of the pivotally mounted thruster is variable during use of the underwater vehicle.

7. The underwater vehicle of claim 6, wherein during use of the underwater vehicle, the attitude of the thruster is variable by up to 50 degrees.

8. The underwater vehicle of claim 1, wherein the pivotally mounted thruster is mounted on pivot bosses with stops to control the maximum deflection of the pivotally mounted thruster.

9. The underwater vehicle of claim 1, further comprising a control system which centrally controls an attitude of the pivotally mounted thruster on the vehicle.

10. The underwater vehicle of claim 9, wherein the vehicle has a plurality of thrusters that are pivotally mounted on the vehicle, and wherein the control system co-ordinates attitudes of the plurality of thrusters to focus the overall thrust of the vehicle in a particular desired direction.

11. The underwater vehicle of claim 9, wherein the vehicle has a plurality of thrusters that are pivotally mounted on the vehicle and wherein the control system comprises mechanical linkages to link the plurality of thrusters to a central control bar that is actuable in order to adjust the attitude of all of the plurality of thrusters simultaneously.

12. The underwater vehicle of claim 11, wherein the central control bar is mounted on a rotatable actuator.

13. The underwater vehicle of claim 1, wherein an attitude of a thrust from the thruster is centrally controlled by an electronic mechanism.

14. The underwater vehicle of claim 1, wherein the underwater vehicle is a remotely operated vehicle.

15. The underwater vehicle of claim 14, wherein the remotely operated vehicle comprises a camera and at least one grappling arm.

16. The underwater vehicle of claim 2, wherein at least one of the plurality of pivotally mounted thrusters is disposed proximate to a corner of the vehicle.

17. The underwater vehicle of claim 2, wherein at least one of the plurality of pivotally mounted thrusters is pivotable in a single plane.

18. The underwater vehicle of claim 3, wherein at least one of the plurality of pivotally mounted thrusters is pivotable in a single plane.

19. The underwater vehicle of claim 2, wherein the underwater vehicle comprises a frame, the frame defining at least one aperture, and wherein at least one of the plurality of pivotally mounted thrusters is contained within the frame and arranged to direct thrust through the at least one aperture.

20. The underwater vehicle of claim 3, wherein the underwater vehicle comprises a frame, the frame defining at least one aperture, and wherein at least one of the plurality of pivotally mounted thrusters is contained within the frame and arranged to direct thrust through the at least one aperture.