EP0290325A1 - System for exploring and surveying the sea bottom by means of an under-water vehicle, and for controlling it - Google Patents

Abstract

This system, of the type comprising at the end of a primary cable (3), a first fish (5), to which is connected a secondary cable (7) towed by a second fish, is characterized in that it comprises, near the first fish (5), means (18) for measuring the angle between the direction of the relative current and the vertical plane passing through the secondary cable (7), and means for measuring the angle of inclination of the secondary cable (7), relative to the horizontal, connected to means for automatic piloting of the second fish to bring said angles to predetermined values.

Description

The technical sector of the invention is that of underwater vehicles which are supplied with electrical energy by a cable, commonly called "umbilical cable", from a ship on the surface.

We know from French Patent No. 2,270,141 of the Applicant, a system for exploring and monitoring sub-aquatic bottoms for fish towed by cables, by a ship, comprising at the end of a primary cable of support and towing, a first fish automatically stabilized in altitude towards the bottom and, starting from this first fish, a secondary cable towed by a second self-propelled fish stabilized in the same way, remote controllable and carrying detection instruments , the primary cable being a towing cable and the two cables, transmitters of energy developed on the vessel, of remote control signals of the second fish, as well as detection signals coming from the latter and thus returning to on-board reading devices at on the ship.

This arrangement considerably increases the immersion and speed performance compared to the water of such a system.

The first fish, also called "depressor", is hooked at a point on the umbilical cable and is used to tension down the section of cable between the vessel and the depressor, by the effect of its hydrodynamic lift and / or its apparent weight in water. The section of cable extending between the vessel and the depressor is also called a "trailer".

The section of cable extending between the depressor and the second fish, also called "main gear", can then be approximately rectilinear and horizontal, and directed in the direction of movement of the system in the water. The section of cable between the depressor and the main machine is also called a "leash".

The main machine can therefore pull the whole system with very little effort, even when this machine has to move far ahead of the ship.

Furthermore, a winch installed, either in the main gear in accordance with the aforementioned patent, or in the depressor, in accordance with the applicant's French certificate of addition no. 2 325 557, makes it possible to vary the useful length of the leash and therefore the longitudinal position of the main machine relative to the depressant.

However, this system has a number of drawbacks. Indeed, when a force, generally hydrodynamic, is applied to the main machine, transversely to the leash, that is to say vertically or laterally, hydrodynamic forces due to the speed relative to the water, act on the leash and bend it, increase the transverse displacement of the main gear and make it move back.

This transverse force can be applied voluntarily to the main machine to move it transversely, as indicated in the patent mentioned above, or involuntarily due to an imprecision in the adjustment of the transverse force by ballast, control surfaces or propellants, with effects eminently harmful.

The object of the invention is therefore to solve these problems.

To this end, the subject of the invention is a system of the type as described above, characterized in that it comprises, near the first fish, means for measuring the angle between the direction of the relative current and the plane vertical passing through the secondary cable, these measuring means being connected to means for automatically piloting the second fish to bring this angle to a predetermined value.

According to another characteristic, the system comprises, near the first fish, means for measuring the angle of inclination of the secondary cable relative to the horizontal, these measuring means also being connected to the means for automatically piloting the second fish. to bring this angle to a predetermined value.

According to yet another characteristic, the first and second fish include means for measuring their immersion depth, these means also being connected to the means for automatically piloting the second fish to bring the difference in the immersion depth of the two fish to a predetermined value.

Advantageously, these predetermined values are equal to zero.

The means for automatically piloting the second fish therefore receive information enabling them to control the thrusters as well as the control surfaces of the second fish, in order to bring the various values mentioned above to their set values.

Thus the leash generally remains rectilinear in the plane passing through the ship, the trailer and the depressor and in a horizontal plane.

This device makes it possible to make the system stable with respect to parasitic transverse forces on the main machine. A winch installed on the ship, allows by spinning or by swallowing the trailer, to increase or reduce the depth of immersion of the depressor and therefore that of the main machine thanks to the different measurement means and the automatic piloting means.

Furthermore, another winch can also be provided on the depressor or on the main gear, this winch making it possible, by spinning or by swallowing the leash, to advance or retreat the main gear relative to the depressor and to the ship.

However, it is then no longer possible to move the main vehicle laterally by acting on its control surfaces or its lateral thrusters, as was the case in patent No. 2,270,141 mentioned previously.

To overcome this drawback, the first fish includes roll control means. When the depressor is tilted laterally, its hydrodynamic lift acquires a lateral component which laterally separates the lower end of the trailer and the depressor. The main machine then deviates laterally by the same length as the depressor, thanks to the various measurement means and to the automatic pilot means.

In addition, the winch installed on the depressor or on the main gear is bulky, delicate and expensive.

This winch can be eliminated by providing a tube articulated, on the primary cable above the first fish, and in which slides the second cable, the end of which forms a loop and is hooked to the first fish.

This loop is stretched either by the relative current, or by means provided for this purpose and which will be described in more detail below, so that a parasitic transverse force on the main machine does not result in an excessive curvature. the leash just in front of the trailer and an excessive transverse deviation from the main gear.

The tensioning means of the loop may for example be constituted by a pulley around which the loop passes, this pulley being rotatably mounted between two arms secured to a body of high hydrodynamic drag such as a plate parallel to the axis pulley rotation.

By varying the thrust of the longitudinal engine (s) of the main engine, it is then possible to make the main engine move forward or backward relative to the depressor and / or the ship, by sliding the leash in the tube.

• La figure 1 représente un système d'exploration et de surveillance de l'état de la technique.
• La figure 2 illustre l'effet d'un effort transver­sal appliqué à un engin principal entrant dans la constitu­tion d'un système de l'état de la technique.
• La figure 3 représente un premier mode de réalisa­tion d'un dépresseur entrant dans la constitution d'un sys­tème selon l'invention.
• La figure 4 représente un second mode de réalisa­tion d'un dépresseur entrant dans la constitution d'un sys­tème selon l'invention.

The following description, with reference to the accompanying drawings from a non-limiting example, will make it possible to understand clearly how the invention can be put into practice.

• FIG. 1 represents a system of exploration and monitoring of the state of the art.
• Figure 2 illustrates the effect of a transverse force applied to a main machine entering into the constitution of a system of the state of the art.
• FIG. 3 represents a first embodiment of a depressant forming part of a system according to the invention.
• FIG. 4 represents a second embodiment of a depressant forming part of a system according to the invention.

As shown in FIG. 1, which shows a use at sea of the main components described in French patent no. 2 270 141, a ship 1 carries a winch 2 by means of which a primary cable 3 is spun or swallowed up. which will also be called a trailer thereafter.

This trailer is provided for example with hulls, hair or ribbons 4, which reduce its hydrodynamic drag and allow it to sink deeper into the sea, despite the effect of the speed of movement of the ship and that of the current on the contrary, thanks to the downward traction exerted by a first fish 5, which will also be called a depressor, attached to the end of this trailer.

This traction is obtained either by the effect of the apparent weight in water of this depressor 5 or by that of the downward hydrodynamic lift due to one or more wings 6 with which this depressor is equipped, or more generally by a combination of these two effects.

It should be noted that this depressant may not contain any specific means of propulsion.

In the lower part of the trailer 3 or on the depressor 5 is fixed a secondary cable 7 also called "leash", at the front end of which is fixed a second fish 8 which will also be called "main gear".

The primary and secondary cables comprise electrical conductors for supplying electrical energy to the main vehicle 8 and for transmitting different information.

The secondary cable can be smooth and advantageously has a slightly positive buoyancy so that, in equilibrium in the current and straight, it descends slightly downward from the depressant.

The main vehicle 8 is equipped with various components not shown in this figure, such as cameras, sonar, manipulator arms or jettisonable loads necessary for the accomplishment of its various missions at sea.

This machine also comprises one or more longitudinal thrusters 9 and transverse thrusters 10 and / or control surfaces, of known type, allowing it to move for example transversely with respect to the leash, that is to say vertically or laterally.

It should be noted that a transverse force can be obtained by the hydrodynamic lift of the machine due to its inclination relative to the current, this inclination itself being obtained by a differential thrust of two parallel propellants.

This main machine 8 can also include a winch, not shown, with a rotating electrical contact, thanks to which it is possible to vary the useful length of the secondary cable or leash, that is to say it is possible to make forward or backward this machine with respect to the depressor 5 and therefore to the ship 1.

The electrical energy and the various signals necessary for the operation of the thrusters and of the various equipments with which the main vehicle 8 is provided, pass through the rotary electrical contact mentioned above, the leash 7, the trailer 3 and a rotating electrical contact of the winch 2 up to ship 1 where a control station and a source of electrical energy are arranged, ensuring the operation of the entire system.

As explained in the patent mentioned above, the use of the depressor 5 makes it possible to reduce the energy necessary for the main machine 8 to tension the leash 7 in rectilinear equilibrium relative to that which would be necessary if it there was only one curved cable between main gear 8 and ship 1.

This FIG. 1 illustrates the behavior of a system, when a longitudinal traction force 11 is applied to the vehicle 8 relative to the leash 7.

In FIG. 2, in addition to this longitudinal force, a transverse force is also applied to the machine 8.

This transverse force may be due to a variation in the apparent weight of the main vehicle 8 or the hydrodynamic effect of the control surfaces or transverse thrusters or else to hydrodynamic asymmetries. In this figure 2, a vertical force has been represented but it goes from you would get the same result with lateral effort.

For a low value, 12a, of this effort the leash curves in the relative current and the machine 8 deviates transversely. It should be noted that the angle made by the leash with its initial position and its curvature are maximum near its point of attachment to the trailer.

When the transverse force increases, that is to say 12b, the angle and the curvature increase more and more rapidly, then the leash forms a loop behind the trailer. The machine 8 then continues to move transversely and it recedes in an increasingly important manner.

The pace of these phenomena is such that one cannot use the transverse force to control the machine 8 and for example move it laterally, that is to say perpendicular to the plane of the figure, like this was mentioned in the patent mentioned above. Indeed, the slightest imprecision around the value of the transverse force that would be necessary, creates uncontrolled movements of the machine.

The system according to the invention, the depressor 5 of which is shown in FIG. 3, comprises a rigid tube 13, of which the leash 7 is integral. The end of the leash is fixed to this depressor 5. A socket or sleeve 14 is rotatably mounted around the trailer 3 where it is held by one or two collars 15, so as not to slip.

A pin 16 passing through a lug carried by the sleeve 14 and another lug carried by the tube 13 constitutes a joint with two degrees of freedom between the trailer 3 and the leash 7. It goes without saying that other embodiments of this articulation can be considered.

Behind the joint, the leash forms a loop to keep the joint all its flexibility and it is electrically connected to the depressor as will be described in more detail below.

A heavy arm 17 is articulated around the tube 13 by a bushing or a sleeve 17a so that its axis remains roughly in a vertical plane. At its lower end is disposed a hydrodynamic wind vane 18 mounted at rotation around the axis of the arm.

The wind vane 18 comprises, in a manner known per se, in its rear part, a vertical fin 18a and in its front part a balancing counterweight 18b. The angle made by the wind vane, that is to say practically the local current, with the approximately vertical plane passing through the leash 7 and the arm 17 is measured by an electric angle sensor arranged for example in a arm housing 19.

It goes without saying that this wind vane could be replaced by any other known measuring device making it possible to measure this angle, such as for example by a manometric antenna with a pressure sensor or a sensitive head mounted on a blade with strain gauges.

The electrical signal from the sensor passes through a cable 20 linked for example successively to the arm 17, to the tube 13, and to the leash 7 in order to be electrically connected to this leash and / or to the trailer, preferably in a housing 21 contained in the depressant 5.

The signal is then used in a manner known per se in automatic piloting means of the main vehicle 8, of known type, to control the control surfaces or the lateral thrusters thereof so that, near the trailer, leaves it 7 and the direction of the current are maintained for example in the same vertical plane.

The device also comprises, still close to the first fish or depressor 5, means for measuring the angle of inclination of the leash 7 relative to the horizontal. These means are for example constituted by an electrical attitude sensor such as a pendulum or an accelerometer housed in the housing 19 and measuring the angle made by the arm 17 with the vertical.

Furthermore, the depressor 5 and the main machine 8 may also include means for measuring their immersion depth. The depressor 5 sensor can for example be placed in the arm 17.

The one-axis wind vane, 18, can also be replaced by a two-axis vane, comprising, in its rear part, an additional horizontal wing, a articulation with two axes, of the Cardan type at the lower end of the arm 17 and, on each axis, an electrical angle sensor.

However, this wind vane can be replaced by any other angle of attack and sideslip sensor of known type.

The electrical signals supplied by these various measurement means pass through the cable 20 to the depressor 5 from where they are routed to the automatic pilot means preferably housed in the main machine 8 to control the control surfaces and / or the thrusters. of it so that:
- the angle made by the leash 7 and the projection of the direction of the relative current on the vertical plane passing through the leash near the trailer,
- the angle made by the leash or the horizontal plane near the trailer, and
- The difference in immersion depth between the depressor 5 and the main machine 8, are maintained at predetermined values, for example equal to zero.

The depressor 5 comprises, as mentioned previously, roll control means, constituted for example by control surfaces 22 provided on the trailing edges of the wings 6 thereof. These control surfaces are for example actuated by an electric actuator controlled from the ship.

This command allows, as explained previously, to tilt the depressor 5 and in response to move the main machine 8.

In this case and in an end view of the system, along the axis of movement in the water, the trailer no longer appears vertical but oblique and slightly curved downwards. The arm 17 remains vertical due to its weight and its articulation on the tube 13. Thanks to the wind vane 18 and possibly to the attitude sensor or the immersion sensors, acting on the control surfaces and / or the transverse thrusters of the machine 8, the leash remains in the vertical plane containing the tube 13 and the arm 17, near the depressor 5 with possibly a small immersion gap between the two fish which remains unchanged, the leash remaining more or less rectilinear and requiring little traction effort from the machine 8.

In the embodiment shown in this FIG. 3, the leash 7 is integral with the tube 13. However, and as shown in FIG. 4, the leash 7 can also be slidably mounted in a tube 13a. This tube then advantageously includes guide rings at each of its ends.

A hydrodynamic tensioner 23 can then be provided to keep the leash 7 under tension. The tensioner, of almost zero apparent weight in water, comprises for example a circular plate 23a mounted at the rear of a cone, thus giving the tensioner both great drag and great hydrodynamic stability.

The front part of the clevis-shaped tensioner comprises two arms between which is rotatably mounted a pulley 24 with an axis parallel to the circular plate. The leash 7 passes around this pulley and guide means can be provided to prevent the leash from jumping from the pulley.

The leash is hung on the trailer, for example at 25 at a point located below the tube 13a, in a flexible and articulated manner but without possible sliding.

The end of the leash is electrically connected to the trailer arm, preferably in the housing 21, a signal transmission cable 20a being fixed on the trailer 3 and being connected to this housing 21.

The leash 7 having a certain tangential drag per unit of length, it is possible to vary the length which it occupies from the pulley 24 to the machine 8 by varying the longitudinal traction force, 11, than that -that exercises on the leash.

The tensile force is smaller at the level of the tube 13a, but, thanks to the tensioning means 23, it always remains sufficiently high. Despite the imprecision of the transverse force, the tube 13a does not deviate from an angle important compared to the direction of the local current and the leash remains more or less straight.

Thus by varying the number of turns wound with the winch 2 on the ship, the turning of the control surfaces 22 of the depressor 5 and the traction 11 of the longitudinal thrusters 9 of the main machine 8, which remains quite small thanks to the depressor 5, navigating the second fish 8, fed by cable, in a stable manner, in a wide range of speeds relative to the water and of vertical, lateral and longitudinal deviations from the ship.

Claims (19)

1. Exploration and monitoring system for underwater funds, with fish towed by a vessel (1), of the type comprising at the end of a primary cable (3) for support and towing, a first fish ( 5), to which a secondary cable (7) towed by a second fish (8) is connected, characterized in that it comprises, near the first fish (5), means (18) for measuring the angle between the direction of the relative current and the vertical plane passing through the secondary cable (7), these measuring means (18) being connected to means for automatically controlling the second fish (8) to bring this angle to a predetermined value. 2. System according to claim 1, characterized in that it comprises, near the first fish (5), means for measuring the angle of inclination of the secondary cable (7) relative to the horizontal, these measuring means being connected to the means for automatically piloting the second fish (8) to bring this angle to a predetermined value. 3. System according to claim 1, characterized in that it comprises near the first fish (5) means (18) for measuring the angle made by the secondary cable (7) with the projection of the direction of the current relative on the vertical plane passing through the secondary cable (7), these measuring means (18) being connected to means for automatically controlling the second fish (8) to bring this angle to a predetermined value. 4. System according to any one of claims 1 to 3, characterized in that the first (5) and second (8) fish comprise means for measuring their depth of immersion, these measuring means being connected to the means of automatic control of the second fish (8) to bring the difference in the depth of immersion of the two poisons to a predetermined value. 5. System according to any one of the preceding claims, characterized in that the predetermined value or values are equal to zero. 6. System according to any one of the preceding claims, characterized in that the first fish (5) comprises means (22) for controlling roll. 7. System according to claim 6, characterized in that the control means are constituted by control surfaces (22) provided on the trailing edges of wings (6) of the first fish (5). 8. System according to any one of the preceding claims, characterized in that the secondary cable (7) is articulated on the primary cable (3), the corresponding end of the secondary cable (7) being connected to the first fish. (5) by forming a loop. 9. System according to claim 8, characterized in that the secondary cable (7) is integral with a tube (13) connected by means of articulation to a socket (14) rotatably mounted around the primary cable (3). 10. System according to claim 8, characterized in that the secondary cable (7) is slidably mounted in a tube (13a) connected by means of articulation to a socket (14) rotatably mounted around the primary cable (3). 11. System according to claim 10, characterized in that it comprises means (23) for tensioning the secondary cable (7). 12. System according to claim 11, characterized in that the tensioning means (23) are constituted by hydrodynamic tensioning means. 13. System according to claim 12, characterized in that the tensioning means comprise a pulley (24), around which passes the loop of the secondary cable (7), this pulley being rotatably mounted between two arms integral with a body (23a) of high hydrodynamic drag. 14. System according to claim 13, characterized in that the drag body is constituted by a plate (23a) extending parallel to the axis of rotation of the pulley (24). 15. System according to any one of the preceding claims, characterized in that the means for measuring the angle between the direction of the relative current and the vertical plane passing through the secondary cable (7) comprise a hydrodynamic wind vane (18) rotatably mounted at the end of a heavy support arm (17) itself rotatably mounted around the secondary cable (7). 16. System according to claim 15, characterized in that the support arm (17) is rotatably mounted around the tube (13, 13a). 17. System according to any one of claims 2 to 16, characterized in that the means for measuring the angle of inclination of the cable relative to the horizontal are constituted by an electric attitude sensor. 18. System according to claim 17, characterized in that the attitude sensor is carried by the support arm and measures the angle which the latter makes with the vertical. 19. The system of claim 15 when dependent on claim 3, characterized in that the means for measuring the angle made by the cable with the projection of the direction of the relative current on the vertical plane passing through the cable secondary (7) are obtained by a second axis of rotation of the hydrodynamic wind vane (18), perpendicular to the first.

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