Method for navigating an undersea vehicle

• US 8,380,374 B2
• Filed: 02/07/2008
• Issued: 02/19/2013
• Est. Priority Date: 03/19/2007
• Status: Active Grant

• Current Assignee: Atlas Elektronik GmbH (Thyssenkrupp AG)
• Original Assignee: Atlas Elektronik GmbH (Thyssenkrupp AG)
• Inventors: Rathjen, Dirk, Schmiegel, Armin, Engel, Robert
• Primary Examiner(s): Beaulieu, Yonel
• Application Number:
  US12/531,834
• Publication Number:
  US 20100106349A1
• Time in Patent Office: 1,839 Days
• Field of Search: 701/21, 701/400, 701/503, 701/408, 440/12.5, 114/257
• US Class Current: 701/21
• CPC Class Codes: G01S 15/86 Combinations of sonar systems with lidar systems; Combinations of sonar systems with systems not using wave reflection
• CPC Class Codes: G01S 5/186 Determination of attitude using inertial means G01C9/00; control of attitude G05D1/49

Abstract

In a method for navigating an undersea vehicle (12), navigation data about position, orientation, and absolute vehicle speed of the undersea vehicle (12) are determined from measurement data delivered by navigation sensors (17) via a navigation filter (18) which incorporates the measurement values of a Doppler log (14). To achieve a highly accurate tracking of the course taken by the undersea vehicle (12), particularly during submerging and surfacing phases, the stretch of water (10) traversed by the undersea vehicle (12) is divided into regions (13) which at least in the vertically oriented z-axis have a finite dimension within a Cartesian coordinate system (11). During the voyage of the undersea vehicle (12), the flow rates in the stretch of water (10) in relation to the individual spatial layers (13) are determined and stored from the relative vehicle speeds measured by the Doppler log (14) in successive measurement processes, and from the absolute vehicle speeds issued continuously by the navigation filter (18). The stored flow rates are input into the navigation filter (18) (FIG. 1) in accordance with the respective spatial layer (13) reached by the undersea vehicle (12).

Claims

1. A method for navigating an undersea vehicle (12), having navigation sensors (17) for measuring and continuously outputting data of the absolute speed of the undersea vehicle, a Doppler log (14) for measuring the relative speed of the undersea vehicle in successive measuring operations, and a navigation filter (18) for calculating navigation data relating to the position, attitude and absolute vehicle speed of the undersea vehicle (12) using data from navigation sensors (17) and the measured relative speed values from the Doppler log (14), said method comprising:

subdividing the water area (10) through which the undersea vehicle (12) travels into regions having a finite dimension (d) at least in the vertically oriented z axis of a Cartesian coordinate system (11);

determining currents in the water area inside the regions and storing determined currents as region-specific currents (₁s), at least during the submerging and/or surfacing phase of the undersea vehicle (12), wherein said region specific currents (₁s) are determined from the relative vehicle speeds (w_mⁿ) measured by the Doppler log (14) in successive measuring operations and the absolute vehicle speeds (v_F(t_n)) continuously output by the navigation filter (17);

inputting said stored region-specific currents (_ls) to the navigation filter (18) dependent upon the region through which the undersea vehicle (12) is respectively instantaneously traveling; and

calculating said navigation data.

2. The method as claimed in claim 1, wherein the measurement range of the Doppler log (14) is subdivided into measuring cells (16) which are adjacent to one another in the direction of measurement and preferably have the same cell depth (a) as seen in the direction of measurement, in that the relative vehicle speed (w_mⁿ) is determined for each measuring cell (16) in each measuring operation, and the measuring-cell-specific relative vehicle speeds (w_mⁿ) are transformed into the regions of the water area (10) in association with the measuring operations, and in that, in each measuring operation in each region of the water area (10), the current (_lsⁿ) is calculated from the region-specific relative vehicle speed (_lwⁿ) produced by the transformation of the measuring-cell-specific relative vehicle speeds and the absolute vehicle speed (v_F(t_n)) output by the navigation filter (18) at the time (t_n) of the measuring operation, and the region-specific current (_ls) is derived from the currents (_lsⁿ) calculated for the respective region in all measuring operations and is stored.

3. The method as claimed in claim 2, wherein in order to transform the measuring-cell-specific relative vehicle speeds (w_mⁿ), the respective measuring-cell-specific relative vehicle speeds (w_mⁿ) of those measuring cells (16) which have a sectional volume (_lv_mⁿ) with the same region, said speeds emerging from the same measuring operation (n), are weighted and the sum of the weighted relative vehicle speeds is divided by the sum of the weightings, and in that the transformation result is output in the form of a region-specific relative vehicle speed (_lwⁿ) in the respective region.

4. The method as claimed in claim 3, wherein in order to weight the measuring-cell-specific relative vehicle speeds (w_mⁿ), the latter are respectively multiplied by a weighting factor (_lg_mⁿ), in that the respective weighting factor (_lg_mⁿ) is calculated as the quotient of the sectional volume (_lV_mⁿ) cut from the region by the respective measuring cell (16) and the volume (V_m) of the respective measuring cell (16), and in that the sum of the weighting factors (_lg_mⁿ) represents the sum of the weightings.

5. The method as claimed in claim 1, wherein in order to derive the region-specific currents (_ls), all currents (_lsⁿ) calculated for the respective region in all measuring operations, including the instantaneous measuring operation, are averaged.

6. The method as claimed in claim 5, wherein the previously derived last region-specific current (_ls (old)) is multiplied by the total number (_lBⁿ⁻

1) of measuring operations carried out in the region, said number being reduced by “

1”

, is added to the current (_lsⁿ) calculated in the respective measuring operation and is divided by the total number (_lBⁿ) of measuring operations carried out in the region.

7. The method as claimed in claim 1, wherein the regions are space layers (13) which are above one another in the vertical direction and preferably have the same layer thicknesses (d).

8. The method as claimed in claim 1, wherein the regions are space cells (30) which are adjacent to one another in the x, y and z directions of the Cartesian coordinate system (11) and preferably have the same dimensions.

9. The method as claimed in claim 1, wherein each measuring operation is initiated by the Doppler log (14) emitting a sound pulse.

10. The method as claimed in claim 9, wherein the number (_lBⁿ) of measuring operations carried out in a region is calculated from the number of emitted sound pulses, the range of the Doppler log (14) and the attitude and position of the watercraft (12).

11. The method as claimed in claim 1, wherein the Doppler log (14) generates at least four sound cones (15) which are preferably inclined by the same angles in different directions with respect to the longitudinal and transverse axes of the undersea vehicle (12), and in that the measurement range is delimited by the sound cones (15) transversely with respect to the direction of measurement.