SUBMARINE EXPLORATION SYSTEM COMPRISING A FLEET OF DRONES

Abstract

The invention concerns a submarine exploration system (1) comprising: a master submarine drone (2) designed to move autonomously according to a predetermined flight plan (E) and comprising a communication module (C) for transmitting communication signals; a plurality of follower submarine drones (31, 32, 33, 34, 35, 36), each comprising at least one magnetic field detection system (D), each follower drone further comprising a communication module (C) for receiving communication signals from the master drone; the master drone being designed to transmit navigation instructions (I) to the follower drones and each follower drone being designed to move autonomously depending on the movement instruction such that its movement is slaved to the movement of the master drone.

Claims

1. Submarine exploration system (1) comprising: a. a master submarine drone (2) arranged so as to move autonomously according to a predetermined flight plan (E) and comprising a communication module (C) for transmitting communication signals; b. a plurality of follower submarine drones (31, 32, 33, 34, 35, 36), each comprising at least one magnetic field detection system (D), each follower drone further comprising a communication module (C) for receiving communication signals from the master drone; c. the master drone being arranged to transmit navigation instructions (I) to the follower drones and each follower drone being arranged so as to move autonomously depending on said movement instruction such that its movement is slaved to the movement of the master drone.

2. System (1) according to the preceding claim, wherein the communication modules (C) of the master (2) and follower (31, 32, 33, 34, 35, 36) drones are acoustic communication modules.

3. System (1) according to either of the preceding claims, wherein the master drone (2) is arranged so as to periodically transmit navigation instructions (I) to all the follower drones (31, 32, 33, 34, 35, 36), each follower drone being arranged so as to move in accordance with the last instruction received, until the following instruction is received.

4. System (1) according to the preceding claim, wherein the master drone (2) is arranged so as to periodically determine, from a flight plan (E), a heading to steer (Cm) and a formation geometry (GF) of the follower drones (31, 32, 33, 34, 35, 36), each navigation instruction (I) transmitted by the master drone to all the follower drones (31, 32, 33, 34, 35, 36) comprising said heading to steer and said formation geometry, and wherein each follower drone is arranged, upon receipt of each navigation instruction, so as to move in a direction in accordance with said heading to steer, and to determine and adopt a relative position (d1) with respect to the master drone, in accordance with said formation geometry, until the following navigation instruction is received.

5. System (1) according to any of the preceding claims, wherein each follower drone (31, 32, 33, 34, 35, 36) comprises a navigation system (N) arranged so as to determine a position (P1, P2, P3, P4, P5, P6) of the follower drone at a given moment, and to move from said determined position depending on the navigation instruction (I) received from the master drone (2).

6. System (1) according to the preceding claim, wherein the navigation system (N) of each follower drone (31, 32, 33, 34, 35, 36) is arranged so as to determine an altitude of the follower drone with respect to the sea bed at a given moment, each follower drone being arranged so as to move while maintaining a constant altitude with respect to the sea bed.

7. System (1) according to either claim 5 or claim 6, wherein the communication module (C) of each follower drone (31, 32, 33, 34, 35, 36) is arranged so as to transmit, to the master drone (2), a signal (S1, S2, S3, S4, S5, S6) including said determined position (P1, P2, P3, P4, P5, P6) of the follower drone.

8. System (1) according to the preceding claim in combination with claim 4, wherein the communication module (C) of each follower drone (31, 32, 33, 34, 35, 36) is arranged so as to transmit, to the master drone (2), a signal (S1, S2, S3, S4, S5, S6) including said determined position (P1, P2, P3, P4, P5, P6) of the follower drone and an operating state (E1, E2, E3, E4, E5, E6) of the follower drone, the master drone being arranged so as to determine, from the operating state of the follower drones, said heading to steer (Cm) and said formation geometry (GF).

9. System (1) according to either claim 7 or claim 8, wherein the communication module (C) of each follower drone (31, 32, 33, 34, 35, 36) is arranged so as to receive an echo (St) of the signal (S1) transmitted by the communication module (C) of the follower drone to the master drone (2), and reflected by the master drone, and to determine, from said echo, a relative distance (d1) separating the follower drone from the master drone; and wherein the navigation system (N) of the follower drone is arranged so as to determine said position (P1, P2, P3, P4, P5, P6) of the follower drone at said given moment, by means of said determined relative distance.

10. System (1) according to any of the preceding claims, wherein the master drone (2) comprises a plurality of systems of different types (MBS, LSS) for characterizing the sea bed.

11. System (1) according to any of the preceding claims, wherein the magnetic field detection system (D) of each follower drone (31, 32, 33, 34, 35, 36) comprises a magnetic field sensor which is capable of measuring the magnetic field in the vicinity of the follower drone, the system (1) comprising a data processing module which is arranged so as to extract, from the measured magnetic field, a value that is independent of the values of the ambient magnetic field and the follower drone's own magnetic field, and to detect, on the basis of said value, a magnetic anomaly (A).

12. Method of submarine exploration implemented by a submarine exploration system (1) according to any of claims 1 to 11.

Description

[0048] The present invention will now be described with reference to examples, which are given merely by way of example and in no way limit the scope of the invention, and on the basis of the accompanying drawings, in which:

[0049] FIG. 1 is a partial schematic view of a submarine exploration system according to an embodiment of the invention;

[0050] FIG. 2 shows a method of submarine exploration implemented by the submarine exploration system of [FIG. 1];

[0051] FIG. 3 shows a method of communication between the master and follower drones of the submarine exploration system of [FIG. 1];

[0052] FIG. 4 shows the movements of the master drone and one of the follower drones of the submarine exploration system of [FIG. 1];

[0053] FIG. 5 shows various steps of a method for detecting a magnetic anomaly, implemented by the submarine exploration system of [FIG. 1]; and

[0054] FIG. 6 is a cross-sectional view of a follower drone of the submarine exploration system of [FIG. 1].

[0055] In the following description, elements which are identical, in terms of structure or function, are provided with the same reference signs in different figures, unless otherwise specified.

[0056] FIG. 1 is a view of a submarine exploration system 1 according to an embodiment of the invention.

[0057] The system 1 comprises a master submarine drone 2 and a plurality of follower submarine drones 31 to 36. The drones 2 and 31 to 36 are submarine drones that are capable of moving autonomously. Each of the master 2 and follower 31 to 36 drones is equipped with a communication module C for transmitting and receiving signals, from a magnetic field detection system D that is capable of measuring a magnetic field and from a navigation system N that is arranged so as to determine a position of the drone at a given moment. Furthermore, and in contrast with the follower drones 31 to 36, the master drone 2 comprises a plurality of systems for characterizing the sea bed, including a bathymetric mapping system in the form of a multibeam bathymetric sounder MBS, and an acoustic imaging system in the form of lateral scanning sonar LSS. The master drone 2 is thus multi-sensor, and the follower drones 31 to 36 are thus single-sensor.

[0058] The navigation system N of each of the follower drones 31 to 36 comprises an attitude unit of the MEMS type, which is capable of determining the rolling and pitching of the follower drone. Furthermore, the magnetic field detection system D of each follower drone provides the navigation system N with a magnetic heading. In a variant, it would be possible for each follower drone to be provided with a second magnetic field detection system for providing said magnetic heading, the magnetic field detection system D being, in this case, dedicated to the measurement of the magnetic field. The navigation system N of the master drone 2 comprises an inertial unit of the FOG type, receiving information provided by an acoustic positioning system such as a DVL (Doppler Velocity Log), and comprising a data processing module for the position data, that integrates an algorithm of the Kalman filter type. The precision of the navigation system of the master drone 2 is thus far greater than that of the navigation system of each of the follower drones 31 to 36.

[0059] The communication modules C of the master 2 and follower 31 to 36 drones are acoustic communication modules, such that the drones can exchange data in the form of modulated acoustic signals transmitted by said communication modules, on the same communication channel, i.e. on the same wavelength. Furthermore, the acoustic signals transmitted by the master 2 and follower 31 to 36 drones on said communication channel are temporarily multiplexed, such that the communication modules C access the communication channel in turn, according to a Time Division Multiple Access technique, each of the drones thus transmitting an acoustic signal in at least one time period of a periodic data frame which is attributed to it.

[0060] FIG. 2 is a plan view of a method for submarine exploration of an exploration zone Z implemented by the exploration system 1, [FIG. 3] shows a method of communication between the master drone 2 and the follower drones 31 to 36 during the exploration, as well as a data frame F which thus moves in the communication channel formed between the drones, and [FIG. 4] shows an example of enslavement of a movement of one of the follower drones 31 to the movement of the master drone 2.

[0061] In advance of the exploration, a plurality of formation geometries is loaded into a memory of each of the master 2 and follower 31 to 36 drones. Each formation geometry describes, for a given number of follower drones and for each of said follower drones, its spatial position with respect to the master drone 2, i.e. whether it should be positioned to the left, to the right, in front or behind the master drone 2, and a lateral distance separating said follower drone from the master drone 2. Again prior to the exploration, the master drone selects a flight plan E, i.e. a given formation geometry GF, and a plan of navigation lines PL associated with said formation geometry GF and suitable for the intended exploration zone Z. Each line of the plan of lines PL thus defines the movement of a drone in the exploration zone Z (in solid lines for the master drone 2 and dotted lines for the follower drones 31 to 36 in [FIG. 2]). As described in [FIG. 2], the formation geometry GF defined in the selected flight plan E corresponds to a comb-shaped formation centered on the master drone 2, the follower drones being distributed on either side of the master drone 2 and being regularly spaced apart by 100 m.

[0062] The master drone 2 is arranged so as to move autonomously, with the aid of its navigation system N, in accordance with the flight plan E and with its own line in the plan of navigation lines PL. During its movement along the flight plan E, the master drone 2 transmits periodically, for example every 6 seconds, via its communication module C, a navigation instruction I to all the follower drones 31 to 36 comprising a heading to steer Cm, determined from the flight plan E, as well as a code identifying the formation geometry GF defined in the selected flight plan E. A plurality of navigation instructions I are thus transmitted to all the follower drones in a plurality of time periods of the data frame F.

[0063] Upon receipt of a navigation instruction I by its communication module C, each follower drone 31 to 36 determines its relative position with respect to the master drone 2, by selecting the formation geometry loaded into its memory and associated with said code contained in the navigation instruction I. Each follower drone 31 to 36 thus moves in an autonomous manner, in accordance with the navigation instruction I received, depending on the heading to steer and on the position of the follower drone estimated by its navigation system N, while maintaining its relative position with respect to the master drone 2, until the following navigation instruction is received. More specifically, each follower drone 31 to 36 adopts a navigation mode referred to as “dead reckoning,” in which it estimates its position P1 to P6 depending on its movement, determined by the magnetic heading measured by the magnetic field detection system, and its attitude measured by the attitude unit, on the basis of its last estimated position. The follower drone thus moves towards a new position determined by its estimated position and by the heading to steer Cm contained in the navigation instruction I, and in a manner maintaining its relative position with respect to the master drone 2 defined in the formation geometry GF.

[0064] As shown in [FIG. 4], the dead reckoning navigation mode introduces a drift in the movement of each follower drone (illustrated by the follower drone 31) due to the positioning uncertainty introduced by the estimation of the position P1 to P6. In other words, the positioning uncertainty (represented by the circle IP in [FIG. 4]) increases over time, which can result, on the one hand, in a deviation of the follower drone 31 with respect to its line of navigation in the plan of lines PL and, on the other hand, in a difference between the actual lateral distance d1 between the master drone 2 and the follower drone 31, and that fixed in the formation geometry GF.

[0065] Each follower drone 31 to 36 transmits a signal S1 to S6 to the master drone 2 containing its estimated position P1 to P6 as well as an operating state E1 to E6, i.e. a viable state or a failure state, in a time period in the data frame F which is attributed to it. In order to overcome the drifts of the movements of the follower drones described above, the communication module C of each follower drone receives an echo S1′ of the signal S1 reflected by the master drone 2, and determines, from said echo, the actual relative distance d1 separating the follower drone from the master drone. The follower drone 31 thus passes from the dead reckoning navigation mode to a navigation mode referred to as “in contraction,” in which said relative distance d1 determined by echolocation is integrated in the determination of the position of the follower drone by the navigation system N, and in the movement of the follower drone. On the one hand, this determined relative distance d1 makes it possible to reduce the positioning uncertainty. On the other hand, the comparison between the actual relative distance d1 and that fixed in the formation geometry GF allows the follower drone 31 to regain its navigation line, and thus to comply with said formation geometry GF.

[0066] In the example described, the navigation instructions I transmitted by the master drone 2 lack any instructions regarding an altitude to follow. Furthermore, the navigation system N of each follower drone 31 to 36 comprises an altimeter which is arranged so as to determine an altitude of the follower drone with respect to the sea bed at a given moment, each follower drone being arranged so as to move while maintaining a constant altitude with respect to the sea bed.

[0067] In the example of [FIG. 1], the drone 32 suffers damage and thus sends, in its time period, a signal S2 containing its position P2 and an operating state E2 indicating a failure. Following the sending of the signal S2, the drone 32 is no longer in a state to continue the exploration, and leaves the exploration zone Z, for example to rejoin a base. Upon receipt of the signal S2 indicating the failure state E2 of the follower drone 32, the master drone selects a new flight plan E defining a new formation geometry GF suitable for the remaining follower drones 31 and 33 to 36. In the example described, the follower drone 36 replaces the follower drone 32 and thus assumes its position. In order to maintain homogeneous exploration of the exploration zone Z, the master drone 2 furthermore determines a new plan of navigation lines PL. The master drone 2 thus performs a reconfiguration of the fleet of drones.

[0068] As described in [FIG. 4], a guard time period G separates the successive transmission of signals by the master 2 and follower 31 to 36 drones in the data frame F. It will furthermore be noted that the time periods attributed to the follower drones 31 to 36 are distributed among the various time periods attributed to the master drone 2.

[0069] Finally, the master drone 2 transmits an item of state information E of the submarine exploration system to a remote control unit, for example located on a boat on the surface of the exploration zone Z, in the last time period of the data frame F.

[0070] The duration of the time periods attributed to the communication modules C of the master 2 and follower 31 to 36 drones is identical for all these communication modules. Furthermore, the period of transmission of the navigation instructions I by the master drone is such that the movement of each of the follower drones 31 to 36 between two successive navigation instructions is substantially equal to 15 meters, according to a speed of 3.5 knots. It is thus found that the follower drones 31 to 36 move according to elementary movements of 15 meters according to the flight plan E, which makes it possible to achieve precise enslavement of the trajectory of the follower drones 31 to 36 to that of the master drone 2, while ensuring a robustness of the exploration system 1 in the event of drift or of failure of one of the follower drones.

[0071] Each magnetic field detection system D of the master 2 and follower 31 to 36 drones comprises a magnetic field sensor, in the form of what is known as a 3-component vectorial magnetometer, comprising three directional magnetometers arranged at 90° with respect to one another, each being capable of measuring the magnetic field in the vicinity of the drone. [FIG. 4] thus shows, in the first graph G1, an example of measurements of the three components of the magnetic field, obtained by each of the directional magnetometers of one of the follower drones 31 to 36 during the exploration of the zone Z.

[0072] The exploration system 1 comprises a data processing module (not shown), which is external to the drones 2 and 31 to 36 and is arranged so as to calculate a total magnetic field from the measurements of the three components of the magnetic field shown in the graph G1. Said total magnetic field has been shown in the second graph G2.

[0073] The data processing module recovers, from the navigation system N during the exploration, the data relating to the movement of the follower drone during the exploration of the zone Z, and in particular its heading which has been shown in the third graph G3, and its rolling and pitching which have been shown in the fourth graph G4. Furthermore, the data processing module determines the magnetic susceptibility tensor of the follower drone, as well as the remanent magnetization vector, for example by means of a magnetic dataset referred to as the calibration dataset. The data processing module corrects, from this set of data, the total magnetic field of the graph G2, in order to eliminate therefrom the induced and permanent magnetic fields as well as the ambient magnetic field, in order to extract therefrom a value shown in the graph G5. It is noted on said graph G5 that the extracted value exhibits a variation, corresponding to a magnetic anomaly A in the exploration zone. Furthermore, the data gathered by the systems for characterizing the sea bed (MBS and LSS), of the master drone, make it possible to characterize the source of the magnetic anomaly A and in particular to determine whether it is an inactive hydrothermal site having mineral potential.

[0074] Finally, [FIG. 5] is a cross section of one of the follower drones 31, it being understood that the structure of all the follower drones 31 to 36 is identical. The drone 31 comprises a body 4 formed of a rear compartment 41, a central compartment 42, and a front compartment 43. Each compartment is isolated from the others.

[0075] The follower drone 31 comprises a propulsion system 5 which is arranged in the rear compartment 41, and a battery 6 which is arranged in the central compartment 42. The magnetic field detection system D, the acoustic communication module C, and the navigation system N are arranged in the front compartment 43, so as to limit the impact of the induced and permanent magnetic fields of the propulsion system and of the battery on the magnetic field detection system D.

[0076] The description above clearly explains how the invention makes it possible to achieve the aims it has set itself, and in particular by proposing a submarine exploration system made up of a fleet of submarine drones comprising an autonomous master drone and follower drones, the movements of which are slaved to that of the master drone. The system which has been described thus allows for rapid and effective exploration of deep sea beds, making it possible to detect and distinguish the active sties from the inactive sites, and for which the exploration cost is controlled.

[0077] In any event, the invention is not limited to the embodiments specifically described in this document, and extends in particular to all equivalent means and to any technically possible combination of said means. In particular, it is possible to envisage other types of formations of the master and follower drones. It is also possible to envisage the use of another type of method for communication between the master and follower drones, other than a TDMA, or indeed an internal structure of the follower drones which is different from that which has been described.