Method and autonomous underwater vehicle able to maintain a planned arrangement

1. A method for maintaining a planned arrangement of autonomous underwater vehicles, AUVs, deployed in water, the method comprising:

detecting, by an autonomous underwater vehicle, AUV, among the AUVs, one or more signals emitted at a predetermined moment by one or more among the AUVs, respectively;

automatically estimating a current position of the AUV relative to the one or more AUVs, based on the detected one or more signals by

calculating each of one or more distances between the AUV and the one or more AUVs emitting the one or more signals, based on times of arrival of the one or more signals,

measuring one or more angles to a reference direction from which the one or more signals have arrived, respectively,

determining positions of each of the one or more AUVs relative to the AUV, using corresponding ones among the distances and among the angles,

calculating possible corrective motions of the AUV to adjust the current position to better match the planned position thereof in the planned arrangement, based on the positions,

generating a box in a thrust versus heading space, the box covering representations of the possible corrective motions, and

selecting a corrective motion inside the box according to a predetermined rule; and

performing the corrective motion,

wherein any of the one or more AUVs emitting has potentially drifted to be away from a respective planned position in the planned arrangement, at the predetermined moment.

2. The method of claim 1 , wherein the corrective motion is defined by a heading and a thrust necessary to move the AUV toward the planned position.

3. The method of claim 1 , wherein the one or more signals have individual signatures enabling the AUV to associate an AUV identity with each signal among the one or more signals.

4. The method of claim 1 , further comprising:

preserving an orientation of the AUV relative to a reference direction.

5. The method of claim 1 , wherein the planned formation arrangement is substantially horizontal, and the method further comprises:

maintaining a predetermined depth by the deployed AUVs.

6. The method of claim 1 , wherein

multiple among the AUVs are configured to detect the one or more signals, each of the multiple among the AUVs then automatically estimating a current position thereof and performing a respective corrective motion to adjust the current position thereof to better match a planned position thereof in the planned arrangement.

7. The method of claim 6 , wherein the one or more among the deployed AUVs emit signals simultaneously at plural predetermined moments, the detecting of the one or more signals triggering the multiple among the AUVs to estimate the current position thereof relative to the one or more among the AUVs, and to perform the corrective motion.

8. The method of claim 7 , wherein the plural predetermined moments occur at a predetermined time interval.

9. An autonomous underwater vehicle, AUV, usable in a planned arrangement of autonomous underwater vehicles, AUVs, deployed in water, the AUV comprising:

a body hosting a motor able to move the body horizontally;

a vector receiver attached to the body and configured to detect one or more signals emitted at a predetermined time by one or more among the deployed AUVs, and to measure angles of the detected signals with a reference direction, respectively; and

a controller configured

to automatically estimate a current position of the body relative to the planned arrangement, based on the detected one or more signals, and

to control the motor to perform a corrective motion to adjust the current position to better match a planned position of the AUV in the planned arrangement,

wherein any of the one or more among the deployed AUVs emitting the signals has potentially drifted away from a respective planned position in the planned arrangement, at the predetermined time, and

wherein, to estimate the current position, the controller is configured:

to calculate distances between the AUV and each of the one or more AUVs emitting the one or more signals, using a time of arrival of the one or more signals,

to determine positions of each of the one or more AUVs relative to the AUV, using corresponding one of the distances and the angles,

to calculate possible corrective motions based on the positions, respectively,

to generate a box in a thrust versus heading space, the box covering representations of the possible corrective motions, and

to select the corrective motion inside the box according to a predetermined rule.

10. The AUV of claim 9 , wherein the controller determines and sends to the motor, a heading and a thrust characterizing the corrective motion.

11. The AUV of claim 9 , wherein the one or more signals have individual signatures enabling the controller to associate an AUV identity with each signal among the one or more signals.

12. The AUV of claim 9 , further comprising at least one of:

a compass which allow tracking the reference direction; and

a timer synchronized with timers on the one or more AUVs emitting signals to measure traveling times of the one or more signals from the one or more AUVs to the AUV.

13. The AUV of claim 9 , the AUV further comprising:

a depth maintaining mechanism configured to maintain a predetermined depth of the AUV.

14. The AUV of claim 9 , the AUV further comprising:

a pinger configured to emit a signal at the predetermined time.

15. A controller configured to control a motor of an autonomous underwater vehicle, AUV, usable in a planned arrangement of autonomous underwater vehicles, AUVs, the controller comprising:

an interface configured

to receive data related to one or more signals emitted at a predetermined time by one or more among the deployed AUVs, the one or more signals being detected by a vector receiver attached to the AUV that measures angles of the detected signals with a reference direction, respectively, and

to transmit commands to a motor able to move the AUV horizontally; and

a data processing unit configured

to automatically estimate a current position of the AUV relative to the one or more AUVs, based on the data, and

to generate the commands directing the motor to perform a corrective motion to adjust the current position to better match a planned position of the AUV in the planned arrangement,

wherein any of the one or more among the deployed AUVs emitting the one or more signals, has potentially drifted away from a respective planned position in the planned arrangement, at the predetermined time, and

wherein to automatically estimate the current position of the AUV relative to the one or more AUVs, the data processing unit is configured:

to calculate distances between the AUV and each of the one or more AUVs emitting the one or more signals, using a respective time of arrival of a signal among the one or more signals emitted by each of the one or more AUVs,

to determine positions of each of the one or more AUVs relative to the AUV, using corresponding one of the distances and a respective signal reception angle,

to calculate possible corrective motions based on the positions, respectively,

to generate a box in a thrust versus heading space, the box covering representations of the possible corrective motions, and

to select the corrective motion inside the box according to a predetermined rule.

16. The controller of claim 15 , wherein

the interface is further configured

to receive depth measurements from a depth measuring device,

to transmit the depth measurements to the data processing unit,

to receive depth adjusting commands received from the data processing unit, and

to transmit the depth adjusting commands to a depth adjusting mechanism of the AUV; and

the data processing unit is further configured to generate the depth adjusting commands based on the depth measurements.

17. The controller of claim 15 , wherein

the interface is further configured to transmit a sound emitting command to a pinger attached to the AUV, triggering the pinger to emit a signal at the predetermined time.