Method for establishing a consolidated water current velocity profile

Abstract

The invention relates to a method for determining a water current velocity profile in a water column by registration of a deviation between a first position and a second position of an underwater vehicle travelling in the water column. A batch of underwater vehicles is deployed from a surface vessel into the water. The vehicle(s) steers to the first position, which for the first batch is a predefined estimated position (PEP). The vehicle is by first means recording the second position, which is the actual position (AP). The difference ?P between the predefined estimated position PEP and the actual position is registered and based on the difference a deviation data set is calculated. An updated current profile or stack of horizontal water current velocities UV is determined.

Claims

1. A method for determining a water current velocity profile in a water column by registration of a deviation between a first position and a second position of an underwater vehicle travelling in the water column, said method comprising: deploying a first batch of underwater vehicles comprising at least one vehicle from a surface vessel into the water, said at least one vehicle steering to the first position which for the first batch is a predefined estimated position (PEP) calculated by a first predefined water current velocity profile wherein the at least one vehicle by first means is recording the second position, which is the actual position (AP), the difference ?P between the predefined estimated position PEP and the actual position (AP) is registered and based on said difference a deviation data set is calculated and an updated horizontal water current velocity UV is determined in said water column, the updated water current velocity UV is sent to a controller, said controller is updating the predefined estimated position PEP to an updated estimated position UEP based on the predefined estimated position PEP and the updated water current velocity UV, and a next batch of vehicles dropped into the water are steering to the first position based on the updated estimated position UEP.

2. The method according to claim 1, wherein every new batch of vehicles travelling in the water after the first batch of vehicles is using the updated estimated position UEP calculated by the data set obtained by a batch of vehicles recently deployed, said this position now being the first position.

3. The method according to claim 1, wherein the predefined estimated position PEP and the first position is based on a digital twin hydrodynamic model and information data obtained by measuring 6-axis changes in inclination, acceleration and direction and at least one pressure sensor recording pressure or water depth and a compass for measuring the at least one vehicle heading.

4. The method according to claim 1, wherein the actual position AP is determined by an acoustic transducer carried by the at least one vehicle, said acoustic transducer is recording data in semi real time.

5. The method according to claim 1, wherein a profile for the water current velocity deviation is depicted in a 3D model in vertical and horizontal direction thereby providing a grid pattern.

6. The method according to claim 1, wherein the updated horizontal current velocity profile UV is calculated by a topside CPU-capacity such as a computer comprising a software patch said UV is used for calculating the updated estimated position UEP as the first position.

7. The method according to claim 1, wherein a water current velocity deviation ?D between the predefined estimated water velocity current profile and a calculated water velocity current profile is determined based on the data set.

8. The method according to claim 1, wherein the first position and a first trajectory is determined by a data set comprising a first water current data profile and the second position and a second trajectory is determined by dataset comprising a second water current data profile.

9. Use of the method according to claim 1, for determining an improved and precise position when deploying nodes, underwater vehicles and other devices into the water, and for determining a precise position of nodes, underwater vehicles and other devices already deployed in the water.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is showing a flowchart of a method for navigating a batch of underwater vehicles to a more precise position.

(2) FIG. 2A is a sketch view of a vessel deploying a batch of underwater vehicles into the water.

(3) FIG. 2B is a 2D view of a water current profile.

(4) FIG. 3 is showing a flowchart of a method for navigating a batch of underwater vehicles to a more precise position.

(5) FIG. 4 is showing a flowchart of a method for providing a 3D picture of a water current profile provided by the method.

(6) The invention will be explained with reference to FIG. 1.

(7) FIG. 1 is showing a flowchart of a process for navigating a batch of underwater vehicles to a more precise position. A deviation ?P is determined and used for determining a more precise position: an updated estimated position UEPa first positionfor the next batch of vehicles. The deviation between this first position and a second position ?P is determined. The second position is an actual position AP of an underwater vehicle travelling in the water column. A batch of underwater vehiclesnormally 9is deployed from a surface vessel into the water. The vehicles are steering to the first position, which for the very first batch is a predefined estimated position PEP. This PEP is determined by an estimated water current velocity profile. The estimated water current velocity profile is based on a hydrodynamic model, and information data obtained by measuring 6-axis changes in inclination, acceleration and direction and at least one pressure sensor recording pressure and a compass.

(8) Each vehicle is by first means such as an acoustic transducer recording the second position, which is the actual position AP.

(9) The difference ?P between the predefined estimated position PEP and the actual position ?P is registered, and based on said difference a deviation data set is calculated. A water current velocity deviation ?D between the predefined estimated water current velocity profile and a calculated water current velocity profile might also be determined.

(10) The value of ?Pand when appropriate ?Dis sent to a topside controller, and the controller is updating the predefined estimated position PEP to an updated estimated position UEP based on the predefined estimated position PEP and the ?P. The next batch of vehicles is dropped into the water and are steering to the first position based on the updated estimated position UEP. In this way the deviation between actual position AP and planned position UEP will be less and less for an increasing number of batches of vehicles deployed in the water.

(11) FIG. 2A is a sketch of a vessel 1 deploying underwater vehicles 2 into the water 3. The travelling of the vehicle through the water is shown by different positions of the same vehicle and marked 2, 2, 2. The end position 4 is where the vehicle 2 is placed. The AP is registered by using signals from a transducer and signals 6 from already deployed vehicles 5 placed on the seabed. These vehicles 5 are also sending signals back to the vessel 1. The predefined position PEP or predefined trajectory is shown with a dotted line. The actual position AP is offset in relation to PEP. The advantages are: less need for extensive acoustic ranging, date recording is up to date, there is less flow and it is more accurate. Further, the digital twin is used. FIG. 2B shows the current velocity profile in 2D that is the profile in horizontal direction for different depths. In reality, this profile will be a 3-D representation, taking compass heading of the current into consideration.

(12) FIG. 3 is showing flowchart of a method for navigating a batch of underwater vehicles to a more precise position. The flowchart also shows how acoustics ranges are used in order to calculate the actual position. A pre-plot position is received and the last-known GPS-position is also registered. The information is used to upload the latest current profile and calculate a trajectory. Then the vehicles are deployed and steering towards the pre plotted position. The actual position is determined based on acoustics information and the value of ?P is now calculated and stored. This value is the used for the next batch of vehicles.

(13) FIG. 4 is showing a flowchart of a method for providing a 3D picture of consolidated water current profiles provided by the method. ?P is registered at certain depths for a number of vehicles and is used for calculating an updated 3D current profile topside. This 3-D current profile is then uploaded and used by nodes to be deployed later.