GB2163114A

GB2163114A - Improvements in or relating to underwater vehicles

Info

Publication number: GB2163114A
Application number: GB08416830A
Authority: GB
Inventors: Douglas James Hampson; William Gordon Edwards
Original assignee: OFFSHORE SYST ENG OSEL
Current assignee: OFFSHORE SYST ENG OSEL
Priority date: 1984-07-02
Filing date: 1984-07-02
Publication date: 1986-02-19
Also published as: GB2163114B

Abstract

An underwater vehicle for pipeline and route survey work which is adapted to be towed submersed on a general heading, for example by a surface vessel. In order to provide positional control of the vehicle it is provided with thrusters (31, 33, 35) and rotors (43, 45, 47) acting in combination. The rotors are in the form of elongate cylindrical members. Depth and lateral control is provided by three thrusters, two horizontal pairs of rotors and one vertical rotor. A thruster is associated with at least one rotor. The thruster provides the necessary flow for the rotors to create sufficient vector force for accurate positional control even at low speeds. <IMAGE>

Description

SPECIFICATION Improvements in or relating to underwater vehi cles The-present invention relates to an underwater ve hicle and in particular to a vehicle for use in pipe line and route survey work.

Sub-sea-survey work is usually carried using var ious towfish or remote operated vehicle (ROV) sys tems.-Towfish, whilst fast and inexpensive, have the disadvantage that they cannot be controlled.

-On the other hand, ROV's are too expensive and have limited speed performance. More recent high speed ROV developments have been found to be too fast to be able to perform adequate visual in spection activities.

The aim of the present invention is to overcome the drawbacks with the known art and to provide a fast multifunction vehicle which is ideal as a sur vey vehicle and capable of both high and low speed controlled operation for all aspects of pipe line and route survey work.

According to the present invention there is pro vided an underwater vehicle for pipeline and route survey work which is provided with positional con trol means comprising thrusters and rotors acting in combination.

The term rotor means a so-called "Magnus ro tor" in which rotation of an elongate cylindrical member in a fluid generates a vector thrust. The term thruster means a propeller, fan or other blade-like device which generates a substantially axial'thrust on rotation thereof.

It is known that so-call Magnus rotors create a high downforce for a small power input at high forward speeds. The present invention compen sates for the low speed operation by providing thrusters which provide the flow necessary for the rotors to create sufficient downforce to allow the vehicle to act as a remotely operated vehicle.

Preferably the rotors are used to control depth and lateral position. More preferably, three thrus ters are used in conjunction with two horizontal pairs of rotors for depth control, and one vertical rotor for lateral control. The thrusters are aligned with the rotors so that the rotors can act on the horizontalflow velocity generated by the thrusters to thereby act as highly sensitive thrust vectoring units. The flow from the thrusters can be the exit flow or the reverse entry flow. By utilising several thrusters generating flow in opposite directions a zero net forward thrust can be arrived at whilst full control of the depth and lateral position is achieved.

The preferred embodiment of the invention in corporati'ng three thrusters, two horizontal pairs of rotors and one vertical rotor is intended to be towed on a general heading by a surface vessel to which the vehicle is connected by an umbilical ca ble which is capable of lifting the vehicle as well as transmitting power, telemetary and video signals.

The umbilical cord is terminated through a univer sally jointed docking bullet which passes through the centre of the vehicle. In the preferred embodiment the vertical rotor is disposed forward of the umbilical attachment point on the axial centre line of the vehicle. It is preferred that the three thrusters are disposed in substantially the same plane which lies perpendicular to the axis of the vehicle and it is further preferred that the three thrusters are disposed forwardly of the rotors. The four horizontal rotors are formed in two pairs which are spaced apart in the longitudinal and vertical directions with the rearmost pair projecting from either side of a central fin carried on the hull of the vehicle and the forward pair projecting from the sides of the hull and disposed rearwardly of the two side mounted thrusters.

Each of the thrusters is driven from its own motor and can be driven in the forward or reverse directions and each of the pairs of horizontal rotors and the vertical rotor is driven from a separate motor. Control means is provided for controlling the speed and direction of rotation of the thrusters and rotors. For protection a side fin is provided which accommodates the end plates of the rotors and a deflector frame interconnects the side thrusters with the side fin.

The number of thrusters and rotors and their relative position on the vehicle is determined by the number of movements which the vehicle has to perform. Thus whilst in the present embodiment the vehicle is provided with four horizontal rotors in two pairs and one vertical rotor and three horizontal thrusters it will be appreciated that in certain circumstances a single rotor and thruster may be sufficient to control movement in any one direction.

The present invention will now be described further hereinafter, by way of example only, with reference to the accompanying drawings; in which: Figure 1 is a perspective view of one embodiment of underwater vehicle according to the present invention, and Figure 2 is a cut away perspective view of the vehicle of Fig. 1 showing internal detail.

Referring to the drawings there is shown an underwater vehicle comprising a frame work 1, preferably of aluminium alloy, fitted with glass reinforced plastic body shells and fairings. The vehicle has a pair of rear tail fins 3 with respective end mounted rudders 5. A central fin 7 projects upwardly from the top of the hull and an umbilical cable 9 is attached to the fin remote from the hull by way of a universally jointed docking bullet. This connection is disposed approximately on the foreaft centre line of the vehicle. The cable is so-called electro-mechanical umbilical cable capable of lifting the vehicle as well as transmitting power, telemetry and video signals. The vehicle is provided with aft-fin surfaces 11 which are connected to the frame work of the hull by way of mounting arms 13, 14.The arm 14 forms part of a deflector frame for the sides of the vehicle and the upper part of the vehicle is provided with a similar deflector frame described further hereinafter.

The various items of equipment required to operate the vehicle and to carry out the required survey work is mounted on the frame. These include such items as a control pod 15, a giro pod 17 which is optional, transformers, and sensor equip ment including sonar 19, side-scan sonar 21, sub bottom profilers 23, video cameras with tilt 25, lights 27, and cameras 29.

The vehicle further comprises three thrusters 31, 33, 35 and three drive motors, 37, 39, 41 driving re spectively a vertical rotor 43 and two pairs of hori zontal rotors 45, 47. The rotors are so-called "Magnus Rotors" which utilise the principles of thrust derived from rotation of an elongate cylin drical member in a moving fluid. The thrusters and Magnus rotors serve to control the depth and lat eral position of the vehicle-when it is being-towed.

More particularly the lateral position is controlled by the single vertical rotor 43 whilst the depth is controlled by the two pairs of horizontal rotors 45, 47. The derive to the vertical rotor 43 is from motor 37 by way of a stepdown gear 49 with the motor and gear being mounted on the frame 1. The rotor can be operated in either direction of rotation.

Similarly, the pair of horizontal rotors 45 are driven from motor 39 by way of a step-down gear 51 and the pair of horizontal rotors 47 are driven from motor 41 by way of a gear 53. In the illustrated em bodiment each pair of rotors 45, 47 comprises two rotors mounted on a common shaft each of which projects from an opposite side of the vehicle centre line. In the described embodiment the motor 39 drives the two rotors of the rotor 45 simultane ously and similarly the motor 41 drives the two ro tors of rotor 47 simultaneously. However, it will be appreciated that in certain circumstances it may be desirable to drive each of the two rotors of each pair independently for example if it is wished to control the roll angle of the vehicle and in this case separate drive motors would be provided for each rotor of the pair.

Each thruster comprises a motor mounted on the frame by way of respective arms and each motor drives a propeller, fan or equivalent blade-like de vice which is preferably accommodated within a cylindrical cowling 55. The axis of the motors and blades is aligned with the longitudinal axis of the vehicle such that rotation of the propellers gener ates a flow velocity in the direction of the longitu dinal axis of the vehicle. The motors can be operated in a clockwise or anti-clockwise direction in order to generate a forward or reverse flow.

As shown the three thrusters are disposed in substantially the same plane which is transverse to the longitudinal direction of the vehicle, and in a triangular configuration with the thruster 31 dis posed upwardly of the hull and aligned with the rotor 43 and fin 7 whilst the rotors 33 and 35 are disposed laterally of the hull and aligned with the pair of rotors 45. The pair of rotors 47 are disposed upwardly and aft of the rotors 45 and approxi mately aligned with the axis of the thruster 31. In order to protect the vehicle from damage in use the ends of the horizontal rotors are shielded by theft fin surfaces 11 and the arm 14 connects be tween the thruster and the forward end of the aft fin surface to serve as a deflector frame to reduce snagging risks.Similarly, a member 59, curved as illustrated, extends from the top of the fin 7 to the housing of thruster 31 and served to protect the vertical rotor 43 from damage which is located inwardly of the member 59.

In operation, the thrusters 31,33 and 35 generate a flow velocity over the hull which is acted on by the Magnus rotors 43, 45 and 47. The rotors act on either the exit flow or the reverse entry flow of the appropriate thruster and so act as highly sensitive thrust vectoring units. By controlling the directionof flow of the three thrusters independently it is possible to arrive at a zero net forward velocity or any other desired forward velocity up to an operating speed of 7 knots (3.5 m/sec) whilst having the necessary flow velocity to get maximum effect from the rotors.For example, thrusters 33 and 35 could be generating a rearward flow velocity whilst thruster 31 generates a forward flow velocity and in conjunction with rotational speed of the rotors the desired depth can be maintained. Similarity, the thruster 31 acting in conjunction with the vertical rotor 43 can be utilised to change the lateral position of the vehicle. Since the rotor 43 is disposed adjacent the central axis of the vehcile which coincides approximately with the location of the- umbilical cord 9 it will be appreciated that only small positional changes in the vehicle can be-achieved relative to this effective pivot axis. If it is desired to effect heading changes to the vehicle as a whole then additional vertical rotors may be provided at a location spaced a greater distance from the connection of the umbilical cord.For example a further single vertical rotor may be provided towards the aft of the vehicle with an associated thruster or alternatively two laterally spaced vertical rotors may be provided, again with associated thrusters.

It will be further appreciated that if maximum efficiency is required from the thrusters two thrusters may be provided for each rotor so as to avoid having to use either the exit flow or the reverse entry flow from a single thruster. That is to say one thruster would be used for forward velocity and another for rearward velocity with the rotor acting on the exit flow velocity in each case.

The use of thrusters in conjunction with rotors has several advantages over swivelling thrusters, fixed vertical thrusters or other more conventionai means of providing vertical or horizontal (lateral) forces, such as: absence of linear or rotary actuators; lower power requirement than the equivalent fixed thruster; simple installation of the essential forward thrust units; the inefficient operation and momentum drag associated with turning flow through 90 into a thruster is eliminated; one fixed thruster can serve several duties simultaneously or without change of setting; no direct suction of mud from the sea bed, and less direct 'jetting', compared with a direct thruster; highly sensitive control of vertical force and position, pitch angle, roll angle (if required) and lateral motion can be achieved with the three standard thrusters and the three Magnus rotors; all the components are fixed rigidly and less exposed or prone to damage, the rotors being rugged and easy to replace at sea; none of the control system components can fail or become jammed due to damage in transient position; and fewer moving parts are involved to achieve the required control.

A typical vehicle will have a length of 2.2 metres, a width of 1 metre and a height of .7 metres with a working depth of 200 metres behind or abeam of the surface control vessel at a distance of 400 metres from the control vessel. The vehicle is capable of carrying a variety of sensors to perform tasks such as bathymetry, seabed survey, pipeline survey, pipeline leak detection, wreckage survey, telecommunications cable survey, ocean mining survey and environmental survey. The various sensors and attachments to carry out this work can be accommodated on the frame work of the vehicle.

The control of the vehicle can be by way of the umbilical cord and three axis joystick on the surface vessel.

As mentioned above additional rotors and thrusters may be provided on an alternative vehicle to perform other positioning movements and it is possible that the combination of thrusters and rotors could be used on a completely independent underwater vehicle utilising remote control operation or even manned operation. Full control may be achieved by having three thrusters aligned in the longitudinal direction of the vessel and a further three thrusters aligned in the transverse direction of the vessel. These being associated with respective horizontal and vertical rotors.

Claims

1. An underwater vehicle for pipeline and route survey work which is provided with positional control means comprising thrusters and rotors acting in combination.

2. An underwater vehicle as claimed in claim 1 in which three thrusters are used in conjunction with two horizontal pairs of rotors and one vertical rotor, with a thruster aligned with at least one rotor.

3. An underwater vehicle as claimed in claim 1 or 2 in which the thrusters are aligned to generate a flow velocity which is parallel to the longitudinal axis of the vehicle, and the rotors act on this flow.

4. An underwater vehicle as claimed in claims 1, 2 or 3 in which the three thrusters are disposed in substantially the same plane, two opposite one another on opposite sides of the vehicle hull and the other vertically offset therebetween.

5. An underwater vehicle as claimed in any of claims 1 to 4 in which the two horizontal pairs of rotors are offset axially and vertically with respect to one another.

6. An underwater vehicle as claimed in claim 5 when appendent to claim 4 in which the rotors of one horizontal pair are disposed in alignment with and astern of a respective side thruster, and the vertical rotor is disposed in alignment with and astern of the vertical rotor.

7. An underwater vehicle as claimed in claim 6 in which the other horizontal pair of rotors is disposed vertically in between the two side thrusters and beneath the third thruster and astern of the vertical rotor and the said one horizontal pair of rotors.

8. An underwater vehicle as claimed in any of claims 2 to 6 in which a towing line is adapted to be attached to an attachment point on the vehicle, which attachment point is disposed on the vertical centre line of the vehicle which lies astern of the vertical rotor.

9. An underwater vehicle as claimed in claim 8 and comprising a central fin depending vertically upwardly from the hull and carrying the attachment point for the towing line.

10. An underwater vehicle as claimed in claim 9 in which one horizontal pair of rotors project outwardly from the central fin.

11. An underwater vehicle as claimed in any of claims 2 to 10 in which a respective aft-fin surface is carried by the hull and disposed on each side of the hull outwardly of the ends of the two horizontal pairs of rotors.

12. An underwater vehicle for pipeline and route survey work which is adapted to be towed submersed through the water, comprising an elongate hull defining a longitudinal axis and provided with positional control means to control the depth and lateral position, said positional control means comprising three thrusters, two horizontal pairs of rotors and one vertical rotor, each thruster being associated with at least one rotor, two of the thrusters being disposed opposite one another on opposite sides of the hull and the third being disposed vertically aligned with and offset from the longitudinal axis and the two side thrusters, the horizontal pairs of rotors being arranged to project on opposite sides of the hull and spaced axially and vertically from one another.

13. An underwater vehicle as claimed in claim 12 further comprising a central fin projecting vertically from the hull, and two aft-fin surfaces suspended from each side of the hull, one of the horizontal pairs of rotors depends from opposite sides of the central fin, and the other depends from opposite sides of the hull, with the aft-fin surfaces positioned outwardly of and overlapping with the ends of the two horizontal pairs of rotors.

14. An underwater vehicle as claimed in claim 13 in which a respective deflector frame connects between the hull and the top leading edge of the central fin and each of the leading edges of the aftfin surfaces.

15. An underwater vehicle as claimed in claim 14 in which the deflector frame incorporates the thruster mounting.

16. An underwater vehicle constructed and arranged and adapted to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.