NO306705B1 - Method and apparatus for searching for an object - Google Patents

Description

Field of the invention

The present invention relates to a method for searching for an object, in particular an object that is underwater, using a mother vessel or an intermediate vessel, equipped with sonars for sending out and reflecting search beams which on a display on the vessel indicate one or more objects in the search area under water.

The invention also relates to a device for this purpose.

The invention can be used to search for any objects, but will be described in the following in connection with a special area of application, namely in connection with demining.

Known technique

Mine clearance from a surface vessel involves a number of activities or problems. The vessel must first detect the object in order to be able to classify and then destroy the object.

This is currently done by a combination of hull-mounted sonar for detection/classification, ROV for visual classification/inspection and then deployment and detonation of the charge.

This process is time-consuming because visual inspection from the ROV is required. After the ROV has placed the charge, it must be brought to a safe distance before the charge is set off. In addition, the charge must be large, because you want to avoid getting too close to the mine with the expensive ROV.

Purpose of the invention

The present invention is based on the task of presenting a concept for a new system for searching for an object, in particular a new system for the inspection and destruction of mines, MINESNIPER, which uses existing mine sonar and a light and cheap guided weapon with a small charge. The system allows, via the TV camera in the weapon, the visual classification of mines before they are laid, and involves a significant reduction in the time from discovery to destruction of the target.

The task is solved by a method of the type indicated at the outset, which according to the invention is characterized by the use of a search unit that can be controlled from the vessel or craft, which includes at least one transponder/responder or the like, for sending out signals corresponding to the search beam, and that said signal ( are) registered on the display on the mother vessel and used to control the search unit towards a designated object along the sonar's search beams.

An advantageous feature of the method is that signals from the transponder/responder are controlled in such a way that the signal is received in the time interval that coincides with the reflected echo of the search beam.

Appropriately, sensors are mounted on the search unit for measuring direction, angle with the horizontal plane and distance above the bottom, and furthermore, a plurality of hydrophones can be placed on the mother vessel and/or vessel, possibly on the mine hunting sonar's transducer, as when measuring transponder/ the responder signal's phase or time delay at the hydrophones can determine the search unit's position in the horizontal and/or vertical plane.

Communication between the search unit and mother vessel and/or vessel takes place via a suitable link, in particular a fiber optic wire arranged on a coil on the search unit, as the search unit includes TV equipment and light sources, as well as drive devices, so that the operator on the mother vessel can control the unit which a remote controlled device and inspect the designated object via TV screen.

Appropriately, the search unit is used for mine clearance from a surface vessel or an intermediate vessel, as the unit includes a charge, especially a hollow charge or a directed charge that can be fired from the mother vessel, preferably after inspection via a TV camera which can constitute an aiming device, possibly via a signal from proximity switch.

In particular, it should be understood that the retrieval unit is used as a practice unit, as it comprises a gas cartridge and gas inflatable balloon, or a buoyancy chamber that can be activated by the operator.

A device for searching for an object, especially an object that is underwater, the device being adapted to a mother vessel or an intermediate vessel, equipped with sonars for sending out and reflecting search beams which indicate one or more objects on a display on the vessel in the underwater search area, according to the invention, the device is characterized by the fact that the device includes a search unit that can be controlled from the vessel or craft, which includes at least one transponder/responder or similar for sending out signals corresponding to the search beams, as well as organs that process markings on the projector in relation to a designated object, this relationship is used for automatic or manual remote control of the search unit towards the designated object along the sonar's search beam.

Further features and advantages of the present invention appear from the attached patent claims, as well as the following description taken in connection with the attached drawings.

Brief description of the te<g>nin<g>sfi<g>ures

Figure IA schematically shows the principle of the present invention, especially in connection with searching for mines.

Figure IB schematically shows the principle of the present invention used in connection with an intermediate vessel, for example an ROV. Figures 2A, 2B and 2C respectively show a side view, longitudinal section and front view of a weapon in which the idea behind the present invention is incorporated. Figures 2D and 2E show sections taken along lines A-A and B-B respectively in figure 2A. Figures 3A and 3B show the hydrophone location on the transducer, seen from the front and from the side, respectively. Figures 4A, 4B and 4C show various screens from the operator console.

Mention of embodiments

A system in which the present invention finds application is schematically shown in figure IA. It comprises a system unit that is permanently installed on board a minesweeper or mother vessel 1, and a set of disposable weapons called destroyers 2 that are stored on board. The system unit contains modules for launching destroyers, launcher 3, acoustic positioning (APS) and a central unit connected to a mine hunting sonar 3a. The central unit will contain an operator's console and a central processor which calculates course and position at all times, and which gives maneuvering commands to the destructor 2 via a thin fiber channel 4. An outline of the system in operation is shown in figure IA, where the different operational phases are also drawn.

For the detection and classification of objects, especially mines 2a, a modern mine hunting sonar 3a is used which can include, for example, 100 receiver beams, which together form a fan-shaped search area in the horizontal plane. Each beam 3n is narrow in the horizontal plane, but relatively wide in the vertical plane, so that when incident obliquely it covers a large distance along the bottom la.

If a weapon or a destroyer 2 can be guided down along the beam 3n that hits the mine 2a, it will have the correct course. For this, for example, the classification sonar can be used, but due to the poor vertical resolution, a simple device must be installed to measure the weapon's vertical position.

It must be understood that the weapon must be light and affordable, so that it can be considered as ammunition. It may suitably comprise a light warhead, for example a hollow charge.

Due to the light warhead, the weapon can be made light and compact with good hydrodynamic properties. Relatively little power will be able to give the weapon a speed of 8 knots.

The propulsion can be provided by, as can be seen from Figure 2, two electrically driven propellers. Steering can be done at high speed by rudder, and at low and stationary maneuvering by means of trusters 9 in the same way as an ROV, combined with internal center of gravity displacement.

The weapon can have the center of gravity and the buoyancy point positioned so that you get natural roll stabilization.

The weapon 2 further comprises sensors 10 for measuring direction, angle with the horizontal plane, depth and distance above the bottom. In addition, it is equipped with a TV camera 11 covered by a spherical dome and light 12 for use during the classification of the mine.

The distance and direction of the weapon or destroyer 2 is measured by the mine hunting sonar 3a by equipping the weapon with an acoustic transponder 13 which responds to the mine hunting sonar 3a's broadcast.

All communication between the weapon 2 and the minesweeper 1 takes place via the fiber optic wire 4 which is pulled out from a coil 14 in the tail 14a of the weapon 2. The large data bandwidth means that the bulk of the processing can be done on the minesweeper 1, so that the weapon 2 only contains a minimum of electronics, see especially figures 2D and 2E. An optical transceiver 14b converts the possible signals into optical signals, and controls the sending and receiving of such.

Typical measurements will be a length of approx. 100 cm, a diameter of approx. 2 0 cm and a weight less than 20 kg.

The weapon can be made of two-component thermosetting plastic molded in one part. In the case of larger series, 250 units or more, this will result in rational production.

Control of the weapon 2 takes place so that when the weapon has entered the coverage area of the classification sonar, the transponder signal from the weapon 2 will appear on the display, see figure 1 and figures 4A-4C. This allows for very accurate positioning in the horizontal plane, and the weapon 2 can be steered precisely into the beam or beams 3n which receive the echo from the mine.

A separate acoustic positioning system, APS, 13 is used to guide the weapon into the coverage area of the classification sonar after deployment, and to possibly check the position in the vertical plane on the way to the mine. The hydrophones 15 in this system can be placed on the mine hunting sonar's 3a transducer as shown in Figure 3.

Optionally, said hydrophones can be placed on the mother vessel itself and/or an intermediate vessel, for example a

ROBBERY.

The destroyer 2 can be equipped with a transponder/responder that transmits on the mine hunting sonar's 3a frequency and with a selectable code. The transmission is controlled in time so that the transponder/responder signal is received in a time interval that falls within the time window shown by the mine hunting sonar. The echo from the mine or target 2a and the transponder/responder signal are processed in the same way in the classification sonar. The direction of the destroyer 2 can therefore be compared with high precision to the direction towards the target 2a, since both appear on the mine classification sonar's standard display 16a, see Figure 4C.

In addition, a signal is sent which is received by the four hydrophones 15 which are mounted on the classification transducer 3a. The signals from the four hydrophones 15 are measured and used to determine the destructor's direction in the vertical plane, and before the destructor 2 has entered the sonar beam 3n also in the horizontal plane.

In this phase, the operator only needs to concentrate on the direction. Based on the mine hunting sonar's 3a calculation of the distance to the target 2a and information about the water depth, the search system will calculate a vertical steering angle that brings the destroyer 2 close to the bottom a few meters before it reaches the mine 2a. The altimeter 10 will then take over the vertical control and ensure that the destructor 2 moves along the bottom until the mine 2 can be observed in the TV picture.

Then first the operator will visually control the destructor 2 as one

ROBBERY.

Alternatively, the destructor can be controlled automatically up to and including firing.

It is important to note that such automated management does not affect the cost of the destructor. All sonar detection, calculations of glide angles and control of the destructor 2 and so on takes place on the mine hunting vessel 1. The destructor 2 sends sensor signals unprocessed up through the fiber optic wire 4, and receives control signals through the same wire.

The operator console consists of a classification monitor from the mine hunting sonar 3a, a TV monitor and a console for entering depth and distance to the target as well as the transducer angle as it appears on the mine hunting sonar display 16a. In addition, there is a joy-stick for controlling the destructor 2.

By controlling the acoustic emissions from the destructor 2, a cursor/marker 16 is drawn on the mine hunting sonar's display 16a. The operator must use his joy-stick to hold his cursor on target 2a and the seeker system measures the distance and direction between the two cursors, in order to control the destructor with the support of height and any depth information. Because both cursors are generated acoustically through the same sonar system, the destroyer 2 will be steered on the correct course, regardless of varying current conditions, sound speed profiles or thermal fronts.

The destructor is automatically controlled to follow the bottom la at a pre-programmed distance as it approaches the target. When the distance is approx. 10 m, the speed is reduced to approx. 0.2 m/s. The operator still controls the direction of the destructor 2 by, for example, keeping his cursor on the target 2a. The height above the bottom is automatically controlled by the search system 10.

The weapon 2 can be controlled so that it reaches the height of the mine 2a above the bottom approx. 20 m before it arrives. If the mine is a bottom mine, the weapon will automatically flatten at a height of approx. 2 m.

The weapon will maintain this height automatically. The speed is reduced to approx. 0.2 m/s, and since the weapon is constantly guided in the beam that gives the mine echo, the mine will appear on the TV screen. The operator will then steer the weapon like an ROV and inspect the target, before aiming the weapon so that the charge points towards the center of the mine. When the weapon touches the mine, he will set off the hollow charge.

In order for the charge to be set off, the following three fuses must be triggered: 1) A mechanical fuse is broken, as the weapon is triggered in the launcher or dropped overboard. This allows: 2) A pressure detector can arm the charge after it has entered the water. 3) The charge can then be deposited by the operator via a special code that is transmitted via the fiber optic wire.

The charge can be automatically set off for a given time after it has entered the water. This is to prevent "live" charges from being left in the event of a fault. Alternatively, the charge can be set off by a special acoustic signal, for example from a hand grenade sent out from the minecraft. Destructor can be taken back by a pressure sensor 17 securing the charge when it approaches the surface.

The weapon is light, approx. 20 kg, and therefore easy to put out. With the aid of the hydrophones 15 which are placed on the mine hunting sonar 3a, one can follow the weapon 2 from its deployment and thus steer it into the sonar's coverage area. Launching can take place by a simple arm lifting the weapon over the ship's side and into the water.

The purpose of the present search system is to destroy the target in as short a time as possible after it has been classified as a mine or possible mine. The search system will therefore always have a weapon ready in the launcher 3, which is driven into position when the classification of the target starts. A time schedule can then be set up, where it is assumed that the target is at a distance of 300 m, and that the weapon can travel towards the target with an effective speed of 2 m/s.

For the last 10 m, the weapon travels at slow speed towards the target so that it can be detected visually in the TV camera. This should not be used for searching as the acoustic system ensures that the weapon has the correct direction towards the target.

The time consumption for verification and destruction of a target located at a distance of approx. 300 m, estimated at between 3 and 5 minutes.

A similar operation using an ROV can be estimated to take between 30 and 50 minutes.

If the present invention is used in connection with an exercise system, instead of the charge, the destructor will be equipped, for example, with a balloon that is inflated by a gas cartridge after exercise. Optionally, a buoyancy chamber can be used which is activated by the operator. The destructor will then float up, after which a flashing light will activate. It can then be picked up either from a light boat or the minesweeper.

The pre-exercise destructor can be used again, the following preparation must take place:

1) A new spool of fiber optic wire must be inserted

2) New balloon and gas cartridge insert are installed

3) Changing, possibly charging the battery pack

The exercise destructor is built to withstand many operations. It therefore has a different construction to the war destroyer, which is only supposed to operate for 10-30 minutes.

In connection with figure IA, both sonar and launcher are arranged in connection with the mother vessel itself 1.

Figure IB shows a system according to the present invention where an intermediate auxiliary vessel 101 or a vessel, for example an ROV, a rope-like vessel or the like, is also used. This ROV or craft can, in turn, be equipped with its own launcher and its own hydrophones, but is still connected to the mother vessel 1 for control from there, for example by means of a link, comprising a first fiber cable 4a between destroyer 2 and craft 101, and a second possibly reinforced fiber cable 4b between vessel 101 and mother vessel 1.

In the case of a variant of a submerged auxiliary vessel, for example in the form of a towed vessel or ROV, this can carry its own launcher and its own hydrophones, but here too it is controlled from the mother vessel on the surface.

Claims (14)

1. Procedure for searching for an object under water, using a mother vessel (1) or an intermediate vessel (101) equipped with sonars (3a) for sending out and reflecting search beams (3n) as on a projector (16a) on the vessel (1) indicates one or more objects (2a) in the underwater search area, characterized by the use of a search unit (2) controllable from the vessel (1) or the vessel (101) which includes at least one transponder/responder (13) or similar, that the search unit (2) emits signals that are arranged in such a way that they can be distinguished from other echoes on the display, but still correspond to the search beam (3n), and that said signals are registered in a manner known per se on the display (16a) on the mother vessel ( 1), and is used to control the search unit (2) towards a designated object (2a) along the search beams (3n) of the sonar (3a). 2. Method as stated in claim 2, characterized in that signals from the transponder/responder are controlled so that the signal is received in the time interval that coincides with the reflected echo of the search beam. 3. Method as stated in claim 1 or 2, characterized in that sensors (10) are used on the search unit (2) for measuring direction, angle with the horizontal plane and distance above the bottom (la) and possibly depth. 4. Method as stated in claims 1-3, characterized in that a plurality of hydrophones (15) are used on the mother vessel and/or its intermediate auxiliary vessel (101), possibly on the mine hunting sonar (3a) transducer, as when measuring transponder-/ the responder signal's phase or time delay at the hydrophones (15) can determine the search unit's (2) position in the horizontal plane and/or vertical plane. 5. Method as stated in claims 1-4, characterized in that communication between the retrieval unit (2) and mother vessel (1), and/or the intermediate vessel (101) takes place via a suitable link (4; 4a, 4b), in particular a fiber optic wire (4) arranged on a coil (14) on the retrieval unit (2), the retrieval unit comprising TV equipment (11) and light sources (12), as well as drive means (9), and that the operator on the mother vessel controls the unit as a remote controlled device and inspects the designated object via TV screen. 6. Method as specified in claims 1-5, characterized in that the search unit (2) is used for mine clearance from a surface vessel (1) and/or an intermediate craft, the unit comprising a charge, especially a hollow charge or a directed charge that can is fired from the mother vessel (1), preferably after inspection via a TV camera (11) which constitutes an aiming device, possibly via a signal from a proximity switch. 7. Method as stated in claims 1-5, characterized in that the retrieval unit is used as a practice unit, as it comprises a gas cartridge and gas-inflatable balloon or buoyancy chamber that can be activated by the operator. 8. Device for searching for an object under water, the device being adapted to a mother vessel (1) or an intermediate vessel (101) equipped with sonars (3a) for sending out and reflecting search beams (3n) as on a projector (16a) on the vessel (1) indicates one or more objects (2) in the underwater search area, characterized in that the device comprises a search unit (2) controllable from the vessel (1) or the vessel (101) which comprises at least one transponder/responder (10, 13 ) or the like for sending out signals that are arranged in such a way that they can be distinguished from other echoes on the display, but still corresponding to the search beams (3n), as well as bodies that process markings on the display (16a) in relation to a designated object (2), as this relationship is used for automatic or manual remote control of the search unit (2) towards the designated object (2a) along the sonar's search beam (3n). 9. Device as stated in claim 8, characterized in that the transponder/responder (13) comprises a dynamically controlled time delay means for automatic/manual control of signals from the transponder/responder in a time interval, so that the signal is received in a time interval that falls together with the distance sector for the reflected echo of the search beams (3n). 10. Device as stated in claim 8 or 9, characterized in that the search unit (2) comprises sensors (10) for measuring direction, angle with horizontal plane and distance above bottom (la) and possibly depth. 11. Device as specified in claims 8-10, characterized in that a plurality of hydrophones (15) are suitably placed on the mother vessel and/or the vessel or on the mine hunting sonar (3a) transducer, and that the device includes means for measuring the transponder/responder signal (13) phase or time delay at the hydrophones (15) for determining the search unit's (2) position in the horizontal plane and/or vertical plane. 12. Device as specified in claims 8-11, characterized in that the device comprises a link (4; 4a, 4b) for communication between the search unit and mother vessel and/or vessel, in particular a fiber optic wire (4) arranged on a coil (14) ) on the search unit, and that the search unit comprises TV equipment (11) and light sources (12), as well as drive means (9), so that the operator on the parent vessel (1) can control the unit (2) as a remote-controlled unit and inspect the designated object (2a) via TV screen. 13. Device as specified in claims 8-12, characterized in that the search unit (2) is designed for mine clearance from a surface vessel (1) and/or an intermediate vessel (101), the unit comprising a charge, in particular a hollow charge or a directed charge which can be fired from the mother vessel (1), preferably after inspection via a TV camera (11) which can constitute an aiming device, possibly via a signal from a proximity switch. 14. Device as stated in claims 8-12, characterized in that the search unit is designed as a practice unit, as it comprises a gas cartridge and gas-inflatable balloon or buoyancy chamber that can be activated by the operator.