Underwater carrier navigation positioning method considering in-situ sound velocity observation

Abstract

The invention discloses an underwater carrier navigation and positioning method considering in-situ sound velocity observation, which belongs to the technical field of navigation and positioning, is used for underwater carrier navigation and positioning, and comprises the following steps: for the position of a GNSS (Global Navigation Satellite System) antenna, adopting attitude observation data obtained by an attitude sensor, implementing attitude correction, and obtaining the position of the center of an ultra-short baseline USBL (Universal Serial Bus Language) array element unit; the method comprises the following steps: acquiring in-situ sound velocity observation information in real time through a CTD acoustic sensor carried by an underwater carrier, and correcting a historical fixed sound velocity profile SVP based on the real-time in-situ sound velocity information; and carrying out sound ray tracking again based on the corrected historical fixed sound velocity profile, and carrying out real-time positioning on the underwater carrier. Compared with the prior art, the time-varying correction of the fixed sound velocity profile is realized by using the sound velocity in-situ observation information carried on the underwater carrier, the influence on the navigation and positioning of the underwater carrier is weakened, and the navigation and positioning precision of the underwater carrier is improved.

Description

Technical Field

[0001] The invention discloses an underwater carrier navigation and positioning method taking into account in-situ sound velocity observation, and belongs to the technical field of navigation and positioning. Background Art

[0002] Underwater positioning technology plays an important role in marine activities. Unlike satellite positioning technology on land, electromagnetic waves cannot penetrate thick water layers and are severely attenuated in water. On the contrary, sound waves have good propagation characteristics in seawater, which makes them widely used in various marine activities as a means of communication, navigation and monitoring. With the development of satellite communication technology, the method of combining satellite positioning technology with underwater acoustic positioning has also been successfully applied to marine activities such as marine exploration and development, geological resource surveys, etc.

[0003] The USBL positioning system has the advantages of small size, flexible installation, and portable operation, making it widely used in acoustic positioning of autonomous remote-controlled underwater robots (ARVs) in shallow water environments, and providing auxiliary combined navigation for deep-water missions. Most of the commonly used navigation and positioning methods are based on time measurement based on a historically fixed sound velocity profile to obtain propagation delay for navigation and positioning. However, in actual underwater operating environments, the sound velocity structure changes due to changes in factors such as temperature and salinity in the underwater environment, resulting in a time-varying characteristic of the sound velocity profile. Especially in shallow water, the change in time and space of the sound velocity is greater than that in deep water environments. The historically fixed sound velocity profile cannot reflect this time-varying characteristic, which will seriously affect the navigation and positioning effect of the underwater carrier in the actual underwater environment. Therefore, it is necessary to study the real-time positioning method of the underwater carrier considering the time-varying characteristics of the sound velocity profile.

[0004] The method of the present invention can take into account the time-varying characteristics of the sound speed profile in the actual underwater environment, use the relevant information obtained by the relevant sensors carried on the underwater carrier to correct the historical sound speed profile, establish a real-time positioning model that is more in line with the underwater carrier operation environment, improve the defect that the historical sound speed profile cannot reflect the time-varying characteristics, weaken its influence on the navigation and positioning of the underwater carrier, and improve the accuracy of the navigation and positioning of the underwater carrier in shallow water. Summary of the invention

[0005] The object of the present invention is to provide an underwater vehicle navigation and positioning method taking into account in-situ sound velocity observation, so as to solve the problem in the prior art that the underwater vehicle navigation and positioning accuracy is low due to the change of temperature and salinity elements in the underwater environment caused by the sound velocity structure.

[0006] A method for underwater vehicle navigation and positioning taking into account in-situ sound velocity observations, comprising: S1. For the position of the GNSS antenna, the attitude observation data obtained by the attitude sensor is used to implement attitude correction and obtain the position of the center of the ultra-short baseline USBL array element unit; S2. Obtain the in-situ sound velocity observation information in real time through the CTD acoustic sensor carried by the underwater carrier, and correct the historical fixed sound velocity profile SVP based on the real-time in-situ sound velocity information; S3. Re-track the sound line based on the corrected historical fixed sound speed profile to locate the underwater carrier in real time.

[0007] S1 includes obtaining the position of the USBL at the sea surface end, S1.1. obtaining the position of the GNSS receiver of the sea surface carrier through GNSS , , and They are the components of the GNSS receiver position on the sea surface in the east, north and zenith directions respectively.

[0008] S1 includes S1.2. Obtain the parameters required for attitude correction through the sensors carried on the USBL at the sea surface end. The parameters required for attitude correction include heading angle , Pitch angle and roll angle , establish the coordinate transformation matrix : .

[0009] S1 includes S1.3. Using the arm measurement information between the GNSS receiver and the USBL transmitting unit center on the sea surface carrier , calculate the center position of the USBL array unit on the sea surface : ; In the formula, , and are the components of the USBL array unit center position on the sea surface in the east, north and zenith directions, , and They are the components of the arm measurement information between the GNSS receiver and the center of the USBL transmitting unit on the sea surface carrier in the east, north and zenith directions respectively.

[0010] S2 includes S2.1. Selecting the average sound speed profile of the historically measured sound speed profile set as the reference profile ,The reference sound velocity profile is composed of depth and sound velocity data; S2.2. Obtain temperature, salinity and depth observation data through the CTD acoustic sensor carried by the underwater carrier, and calculate the in-situ observed sound velocity value related to time and depth based on the sound velocity empirical formula .

[0011] S2 includes S2.3. Setting the sliding window according to the depth Calculate the difference between the reference sound velocity profile and the in-situ sound velocity observation, and choose the width to be The sliding window is used to perform weighted average of the sound velocity difference data within the window to obtain the current sound velocity correction value based on the in-situ sound velocity observation. : ; In the formula, is a weight factor affected by the degree of temporal correlation between the observed epochs in the moving window and the selected sampling time, is the epoch index within the window, Index time for the epoch within the window.

[0012] S3 includes time measurement based on the corrected historical fixed sound speed profile, obtaining the propagation delay and the corrected sound speed, and repositioning the underwater carrier.

[0013] S3 includes S3.1. Based on the sound velocity correction value, the reference profile is corrected as a whole to obtain the corrected sound velocity profile. , and according to Perform sound ray tracing to obtain representative sound velocity values .

[0014] S3 includes S3.2. Perform sea surface USBL receiver according to the time difference of each transmitter Direction vector to the underwater target Calculate the direction vector of the underwater carrier : ; ; ; In the formula, is the intermediate parameter, To cope with the jet lag, is the relative position of the receiver combination, is the first-order difference operator matrix, are the coordinates of N receivers in the USBL array element, , and are the components of the USBL receiver on the sea surface in the east, north and zenith directions, , and are the components of the direction vector between the underwater targets in the east, north and zenith directions respectively, , and are the components of the direction vector of the underwater carrier in the east, north and zenith directions respectively; It is expressed as: .

[0015] S3 includes S3.3. Based on the corrected historical fixed sound velocity profile, re-track the sound line to obtain the updated timing, calculate the underwater target position based on the updated timing, corrected sound velocity and direction vector, and average the results obtained by N transmitters to obtain the real-time position of the underwater carrier in the geographic coordinate system. : ; In the formula, is the number of the transmitter in the transmitting array, For the transmitter The timing of Equivalent to the direction vector of the underwater carrier, , and They are Components in the east, north and zenith directions, , and They are respectively the components of the real-time position of the underwater carrier in the geographic coordinate system in the east, north and zenith directions.

[0016] Compared with the prior art, the present invention has the following beneficial effects: taking into account the time-varying characteristics of the sound velocity profile in the actual underwater environment, by utilizing the in-situ sound velocity observation information carried on the underwater submersible, the time-varying correction of the fixed sound velocity profile adopted is realized, the influence on the navigation and positioning of the underwater submersible is weakened, and the accuracy of the navigation and positioning of the underwater submersible is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a technical flow chart of the present invention; Figure 2 It is the motion trajectory diagram of the underwater carrier in the plane direction; Figure 3 It is the vertical motion trajectory diagram of the underwater carrier; Figure 4 is a constant sound speed profile; Figure 5 is the time variation diagram of the sound speed profile; Figure 6 It is the sound velocity variation diagram of the underwater carrier in situ observation; Figure 7 It is the equivalent sound velocity sequence diagram corresponding to the carrier at a water depth of 50m; Figure 8 It is the equivalent sound velocity sequence diagram corresponding to the carrier at a water depth of 150m; Fig. 9 It is the equivalent sound velocity sequence diagram corresponding to the carrier at a water depth of 300m; Fig.10 is the correlation diagram between the equivalent sound velocity series and the in-situ sound velocity observation; Fig.11 It is a comparison chart of the positioning results of the method of the present invention and the fixed sound velocity profile method. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention is described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] A method for underwater vehicle navigation and positioning taking into account in-situ sound velocity observations, comprising: S1. For the position of the GNSS antenna, the attitude observation data obtained by the attitude sensor is used to implement attitude correction and obtain the position of the center of the ultra-short baseline USBL array element unit; S2. Obtain the in-situ sound velocity observation information in real time through the CTD acoustic sensor carried by the underwater carrier, and correct the historical fixed sound velocity profile SVP based on the real-time in-situ sound velocity information; S3. Re-track the sound line based on the corrected historical fixed sound speed profile to locate the underwater carrier in real time.

[0020] S1 includes obtaining the position of the USBL at the sea surface end, S1.1. obtaining the position of the GNSS receiver of the sea surface carrier through GNSS , , and They are the components of the GNSS receiver position on the sea surface in the east, north and zenith directions respectively.

[0021] S1 includes S1.2. Obtain the parameters required for attitude correction through the sensors carried on the USBL at the sea surface end. The parameters required for attitude correction include heading angle , Pitch angle and roll angle , establish the coordinate transformation matrix : .

[0022] S1 includes S1.3. Using the arm measurement information between the GNSS receiver and the USBL transmitting unit center on the sea surface carrier , calculate the center position of the USBL array unit on the sea surface : ; In the formula, , and are the components of the USBL array unit center position on the sea surface in the east, north and zenith directions, , and They are the components of the arm measurement information between the GNSS receiver and the center of the USBL transmitting unit on the sea surface carrier in the east, north and zenith directions respectively.

[0023] S2 includes S2.1. Selecting the average sound speed profile of the historically measured sound speed profile set as the reference profile ,The reference sound velocity profile is composed of depth and sound velocity data; S2.2. Obtain temperature, salinity and depth observation data through the CTD acoustic sensor carried by the underwater carrier, and calculate the in-situ observed sound velocity value related to time and depth based on the sound velocity empirical formula .

[0024] S2 includes S2.3. Setting the sliding window according to the depth Calculate the difference between the reference sound velocity profile and the in-situ sound velocity observation, and choose the width to be The sliding window is used to perform weighted average of the sound velocity difference data within the window to obtain the current sound velocity correction value based on the in-situ sound velocity observation. : ; In the formula, is a weight factor affected by the degree of temporal correlation between the observed epochs in the moving window and the selected sampling time, is the epoch index within the window, Index time for the epoch within the window.

[0025] S3 includes time measurement based on the corrected historical fixed sound speed profile, obtaining the propagation delay and the corrected sound speed, and repositioning the underwater carrier.

[0026] S3 includes S3.1. Based on the sound velocity correction value, the reference profile is corrected as a whole to obtain the corrected sound velocity profile. , and according to Perform sound ray tracing to obtain representative sound velocity values .

[0027] S3 includes S3.2. Perform sea surface USBL receiver according to the time difference of each transmitter Direction vector to the underwater target Calculate the direction vector of the underwater carrier : ; ; ; In the formula, is the intermediate parameter, To cope with the jet lag, is the relative position of the receiver combination, is the first-order difference operator matrix, are the coordinates of N receivers in the USBL array element, , and are the components of the USBL receiver on the sea surface in the east, north and zenith directions, , and are the components of the direction vector between the underwater targets in the east, north and zenith directions respectively, , and are the components of the direction vector of the underwater carrier in the east, north and zenith directions respectively; It is expressed as: .

[0028] S3 includes S3.3. Based on the corrected historical fixed sound velocity profile, re-track the sound line to obtain the updated timing, calculate the underwater target position based on the updated timing, corrected sound velocity and direction vector, and average the results obtained by N transmitters to obtain the real-time position of the underwater carrier in the geographic coordinate system. : ; In the formula, is the number of the transmitter in the transmitting array, For the transmitter The timing of Equivalent to the direction vector of the underwater carrier, , and They are Components in the east, north and zenith directions, , and They are respectively the components of the real-time position of the underwater carrier in the geographic coordinate system in the east, north and zenith directions.

[0029] The technical flow chart of the present invention is as follows: Figure 1 As shown, for the position of the GNSS antenna, the attitude observation data obtained by the attitude sensor is used to implement attitude correction and obtain the position of the center of the ultra-short baseline USBL array element unit; the in-situ sound velocity observation information is obtained in real time through the temperature-salinity-depth instrument CTD acoustic sensor carried by the underwater carrier, and the historical fixed sound velocity profile SVP is corrected based on the real-time in-situ sound velocity information; the sound line tracking is re-performed based on the corrected historical fixed sound velocity profile to locate the underwater carrier in real time.

[0030] The embodiment of the present invention uses the real observation data during the underwater carrier operation, firstly gives the approximate motion trajectory of the underwater carrier, and the approximate motion trajectories in the plane direction and the vertical direction are respectively as follows: Figure 2 and Figure 3 As shown. It can be seen that as the underwater carrier goes from diving to performing tasks and then surfacing, the depth changes significantly. Generally, a fixed sound velocity value is used in underwater positioning, or a certain historical sound velocity profile is selected as a fixed sound velocity profile. Therefore, in order to verify the effect of the modified sound velocity profile based on the in-situ sound velocity observation used in the present invention and the fixed sound velocity value, the fixed empirical sound velocity profile used for comparison is as follows: Figure 4 As shown in the figure, the sound speed profile set data obtained by the ship-borne profiler is averaged and calculated as a fixed sound speed profile. Figure 5 The time variation of the sound velocity profile is shown. It can be seen that at a water depth of 50m, the sound velocity variation is more complex, and the variation in other water depths is relatively small, but significant time variation characteristics can still be seen. Therefore, the traditional method of using a fixed sound velocity profile is based on the assumption that "the sound velocity remains unchanged over time", which is inconsistent with reality.

[0031] In order to use the in-situ sound velocity observation information to correct the fixed sound velocity profile, the characteristics of the in-situ sound velocity observation data were first analyzed. Figure 6 The change of sound velocity observed by the acoustic sensor on the underwater carrier over time is shown, which is highly correlated with the depth of the underwater carrier. In order to determine the feasibility of in-situ sound velocity observation correction, the in-situ sound velocity was compared with the equivalent sound velocity at a fixed water depth. Three typical cases of shallow, middle and deep water depths of 50m, 150m and 300m were selected, and the equivalent sound velocity was calculated by acoustic line tracking. The differences between the two are as follows: Figure 7 , Figure 8 and Fig. 9As shown in the figure, the difference trends in the three cases are roughly the same, especially in the 150m and 300m cases. Further, the correlation between the two was calculated from a quantitative perspective, and the calculation results are shown in the figure. Fig.10 It can be seen that under the water depth of 300m, under most water depth conditions, the in-situ sound velocity and the equivalent sound velocity show a good positive correlation, especially for the underwater carrier near the bottom operation, the correlation is obvious, which provides an analytical reference for correcting the sound velocity profile using in-situ sound velocity observation.

[0032] The positioning effects of the three methods were compared. The results are as follows: Fig.11 As shown in the figure. The positioning result of the method using a fixed sound speed value is most affected by the representative error of the sound speed, and the positioning effect is the worst. The method using a fixed sound speed profile improves the positioning accuracy of the above method to a certain extent. This method further corrects the sound speed profile based on the in-situ sound speed observation information, taking into account the actual change of sound speed over time, which is more in line with the characteristics of the real ocean environment, and thus has the highest positioning accuracy.

[0033] The present invention considers the actual situation of the underwater vehicle navigation and positioning environment, takes into account the time-varying characteristics of SVP, uses the real-time information obtained by the relevant sensors carried on the underwater vehicle, and combines the in-situ sound speed observation to correct the sound speed profile of the historical sound speed profile, thereby obtaining the corrected sound speed profile, and then performs sound line tracking based on the corrected sound speed profile to obtain a new representative sound speed value, obtains distance information based on the propagation delay and the representative sound speed value, and locates the underwater mobile target. The present invention improves the defect that the historical sound speed profile cannot reflect the time-varying characteristics during the underwater vehicle navigation and positioning process, and improves the underwater navigation and positioning results.

[0034] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features may be replaced by equivalents, and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for underwater vehicle navigation and positioning taking into account in-situ sound velocity observation, characterized in that: include: S1. For the position of the GNSS antenna, the attitude observation data obtained by the attitude sensor is used to implement attitude correction and obtain the position of the center of the ultra-short baseline USBL array element unit; S2. Obtain the in-situ sound velocity observation information in real time through the CTD acoustic sensor carried by the underwater carrier, and correct the historical fixed sound velocity profile SVP based on the real-time in-situ sound velocity information; S3. Re-track the sound line based on the corrected historical fixed sound speed profile to locate the underwater carrier in real time.

2. The underwater carrier navigation and positioning method taking into account in-situ sound velocity observation according to claim 1 is characterized in that: S1 includes obtaining the position of the USBL at the sea surface end, S1.

1. obtaining the position of the GNSS receiver of the sea surface carrier through GNSS , , and They are the components of the GNSS receiver position on the sea surface in the east, north and zenith directions respectively.

3. The underwater carrier navigation and positioning method taking into account in-situ sound velocity observation according to claim 2 is characterized in that: S1 includes S1.

2. Obtain the parameters required for attitude correction through the sensors carried on the USBL at the sea surface end. The parameters required for attitude correction include heading angle , Pitch angle and roll angle , establish the coordinate transformation matrix : 。 4. The underwater carrier navigation and positioning method taking into account in-situ sound velocity observation according to claim 3 is characterized in that: S1 includes S1.

3. Using the arm measurement information between the GNSS receiver and the USBL transmitting unit center on the sea surface carrier , calculate the center position of the USBL array unit on the sea surface : ； In the formula, , and are the components of the USBL array unit center position on the sea surface in the east, north and zenith directions, , and They are the components of the arm measurement information between the GNSS receiver and the center of the USBL transmitting unit on the sea surface carrier in the east, north and zenith directions respectively.

5. The underwater carrier navigation and positioning method taking into account in-situ sound velocity observation according to claim 4 is characterized in that: S2 includes S2.

1. Selecting the average sound speed profile of the historically measured sound speed profile set as the reference profile ,The reference sound velocity profile is composed of depth and sound velocity data; S2.

2. Obtain temperature, salinity and depth observation data through the CTD acoustic sensor carried by the underwater carrier, and calculate the in-situ observed sound velocity value related to time and depth based on the sound velocity empirical formula .

6. The underwater carrier navigation and positioning method taking into account in-situ sound velocity observation according to claim 5, characterized in that: S2 includes S2.

3. Setting the sliding window according to the depth Calculate the difference between the reference sound velocity profile and the in-situ sound velocity observation, and choose the width to be The sliding window is used to perform weighted average of the sound velocity difference data within the window to obtain the current sound velocity correction value based on the in-situ sound velocity observation. : ； In the formula, is a weight factor affected by the degree of temporal correlation between the observed epochs in the moving window and the selected sampling time, is the epoch index within the window, Index time for the epoch within the window.

7. The underwater carrier navigation and positioning method taking into account in-situ sound velocity observation according to claim 6, characterized in that: S3 includes time measurement based on the corrected historical fixed sound speed profile, obtaining the propagation delay and the corrected sound speed, and repositioning the underwater carrier.

8. The underwater carrier navigation and positioning method taking into account in-situ sound velocity observation according to claim 7, characterized in that: S3 includes S3.

1. Based on the sound velocity correction value, the reference profile is corrected as a whole to obtain the corrected sound velocity profile. , and according to Perform sound ray tracing to obtain representative sound velocity values .

9. The underwater carrier navigation and positioning method taking into account in-situ sound velocity observation according to claim 8, characterized in that: S3 includes S3.

2. Perform sea surface USBL receiver according to the time difference of each transmitter Direction vector to the underwater target Calculate the direction vector of the underwater carrier : ； ； ； In the formula, is the intermediate parameter, To cope with the jet lag, is the relative position of the receiver combination, is the first-order difference operator matrix, are the coordinates of N receivers in the USBL array element, , and are the components of the USBL receiver on the sea surface in the east, north and zenith directions, , and are the components of the direction vector between the underwater targets in the east, north and zenith directions respectively, , and are the components of the direction vector of the underwater carrier in the east, north and zenith directions respectively; It is expressed as: 。 10. The underwater carrier navigation and positioning method taking into account in-situ sound velocity observation according to claim 9, characterized in that: S3 includes S3.

3. Based on the corrected historical fixed sound velocity profile, re-track the sound line to obtain the updated timing, calculate the underwater target position based on the updated timing, corrected sound velocity and direction vector, and average the results obtained by N transmitters to obtain the real-time position of the underwater carrier in the geographic coordinate system. : ； In the formula, is the number of the transmitter in the transmitting array, For the transmitter The timing of Equivalent to the direction vector of the underwater carrier, , and They are Components in the east, north and zenith directions, , and They are respectively the components of the real-time position of the underwater carrier in the geographic coordinate system in the east, north and zenith directions.

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