An underwater vehicle navigation and positioning method considering in-situ sound velocity observations

Abstract

The present invention discloses an underwater vehicle navigation and positioning method considering in-situ sound velocity observation, belonging to the technical field of navigation and positioning, and is used for underwater vehicle navigation and positioning. It includes implementing attitude correction for the position of the GNSS antenna by using the attitude observation data obtained by the attitude sensor to obtain the position of the center of the ultra-short baseline USBL array element; real-time obtaining in-situ sound velocity observation information through the CTD acoustic sensor carried by the underwater vehicle, and correcting the historical fixed sound velocity profile SVP based on the real-time in-situ sound velocity information; re-performing ray tracing based on the corrected historical fixed sound velocity profile to perform real-time positioning of the underwater vehicle. Compared with the prior art, the present invention realizes the time-varying correction of the adopted fixed sound velocity profile by using the in-situ sound velocity observation information carried on the underwater vehicle, weakens the influence on the underwater vehicle navigation and positioning, and improves the accuracy of the underwater vehicle navigation and positioning.

Description

Technical Field

[0001] The present invention discloses an underwater vehicle navigation and positioning method considering in-situ sound velocity observation, belonging to the technical field of navigation and positioning. Background Technique

[0002] Underwater positioning technology plays an important role in marine activities. Different from satellite positioning technology on land, electromagnetic waves cannot penetrate thick water layers and attenuate severely in water. On the contrary, sound waves have good propagation characteristics in seawater, which makes them widely used as means of communication, navigation and monitoring in various marine activities. 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, and geological resource survey.

[0003] The USBL positioning system has the advantages of small volume, flexible installation, and portable operation, making it widely applicable to the acoustic positioning of autonomous remotely operated underwater vehicles (ARVs) in shallow water environments and providing auxiliary integrated navigation for deep-water tasks. In most common navigation and positioning methods, time measurement is carried out based on a historically fixed sound velocity profile to obtain the propagation delay for navigation and positioning. However, in the actual underwater operation environment, the sound velocity structure changes due to the changes of factors such as temperature and salinity in the underwater environment, resulting in the time-varying characteristics of the sound velocity profile. Especially in shallow water, the changes of sound velocity in time and space are larger than those in the deep-water environment. The historically fixed sound velocity profile cannot reflect this time-varying characteristic, which will seriously affect the navigation and positioning effect of underwater vehicles in the actual underwater environment. Therefore, it is necessary to study a real-time positioning method for underwater vehicles considering the time-varying characteristics of the sound velocity profile.

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

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

[0006] An underwater vehicle navigation and positioning method considering in-situ sound velocity observation includes:

[0007] 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;

[0008] 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;

[0009] S3. Re-track the sound line based on the corrected historical fixed sound speed profile to locate the underwater carrier in real time.

[0010] 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.

[0011] 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 :

[0012] .

[0013] 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 :

[0014] ;

[0015] 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.

[0016] 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 speed profile is composed of depth and sound speed data;

[0017] S2.2. Obtain temperature, salinity, and depth observation data through a CTD acoustic sensor carried by an underwater vehicle, and calculate the in-situ observed sound speed value related to time and depth according to the empirical sound speed formula. .

[0018] S2 includes S2.3. Set a sliding window, and calculate the difference between the reference sound speed profile and the in-situ sound speed observation according to the depth . Select a sliding window with a width of and perform weighted averaging of the sound speed difference data within the window to obtain the current sound speed correction value based on the in-situ sound speed observation. :

[0019] ;

[0020] In the formula, is the weight factor, which is affected by the degree of time correlation between the observation epochs in the moving window and the selected sampling time. is the epoch index within the window. is the epoch index time within the window.

[0021] S3 includes performing time measurement based on the corrected historical fixed sound speed profile, obtaining the propagation time delay and the corrected sound speed, and re-positioning the underwater vehicle.

[0022] S3 includes S3.1. Perform an overall correction of the reference profile based on the sound speed correction value to obtain the corrected sound speed profile , and perform ray tracing according to to obtain the representative sound speed value .

[0023] S3 includes S3.2. Calculate the direction vector of the underwater vehicle between the USBL receiver on the sea surface and the underwater target according to the time difference of arrival of each transmitter : :

[0024] ;

[0025] ;

[0026] ;

[0027] In the formula, is the intermediate parameter. is the time difference of arrival. 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 surface USBL receiver in the east, north, and zenith directions respectively, , and are the components of the direction vector between underwater targets in the east, north, and zenith directions respectively, , and are the components of the direction vector of the underwater vehicle in the east, north, and zenith directions respectively;

[0028] is expressed as:

[0029] .

[0030] S3 includes S3.3. Re-perform ray tracing based on the corrected historical fixed sound speed profile to obtain updated time measurement, calculate the underwater target position based on the updated time measurement, corrected sound speed, and direction vector, and average the results obtained for N transmitters to obtain the real-time position of the underwater vehicle in the geographical coordinate system :

[0031] ;

[0032] In the formula, is the transmitter number in the transmitting array, is the transmitter 's time measurement, is equivalent to the direction vector of the underwater vehicle, , and are respectively 's components in the east, north, and zenith directions, , and are the components of the real-time position of the underwater vehicle in the geographical coordinate system in the east, north, and zenith directions respectively.

[0033] Compared with the prior art, the present invention has the following beneficial effects: Considering the time-varying characteristics of the sound speed profile in the actual underwater environment, by using the in-situ sound speed observation information carried on the underwater vehicle, the time-varying correction of the adopted fixed sound speed profile is realized, the influence on the navigation and positioning of the underwater vehicle is weakened, and the accuracy of the navigation and positioning of the underwater vehicle is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is the technical flow chart of the present invention;

[0035] Figure 2 It is the trajectory diagram of the underwater vehicle's planar motion;

[0036] Figure 3 It is the trajectory diagram of the underwater vehicle's vertical motion;

[0037] Figure 4 It is the fixed sound speed profile diagram;

[0038] Figure 5 It is the time-varying diagram of the sound speed profile;

[0039] Figure 6 It is the diagram of the sound speed change observed in-situ by the underwater vehicle;

[0040] Figure 7 It is the equivalent sound speed sequence diagram corresponding to the underwater vehicle at a water depth of 50m;

[0041] Figure 8 It is the equivalent sound speed sequence diagram corresponding to the underwater vehicle at a water depth of 150m;

[0042] Figure 9 It is the equivalent sound speed sequence diagram corresponding to the underwater vehicle at a water depth of 300m;

[0043] Figure 10 It is the correlation diagram between the equivalent sound speed sequence and the in-situ sound speed observation;

[0044] Figure 11 It is the comparison diagram of the positioning results between the method of the present invention and the fixed sound speed profile method. Detailed implementation manners

[0045] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be described clearly and completely below. Apparently, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative efforts shall fall within the protection scope of the present invention.

[0046] An underwater vehicle navigation and positioning method considering in-situ sound speed observation includes:

[0047] S1. For the position of the GNSS antenna, attitude correction is implemented using the attitude observation data obtained by the attitude sensor to obtain the position of the center of the ultra-short baseline USBL array element;

[0048] S2. The in-situ sound speed observation information is obtained in real time through the CTD acoustic sensor carried by the underwater vehicle, and the historical fixed sound speed profile SVP is corrected based on the real-time in-situ sound speed information;

[0049] S3. Re - perform ray tracing based on the corrected historical fixed sound - speed profile to perform real - time positioning of the underwater vehicle.

[0050] S1 includes obtaining the position of the USBL at the sea surface. S1.1. Obtain the position of the GNSS receiver on the sea - surface vehicle through GNSS , 、 and are the components of the position of the GNSS receiver on the sea - surface vehicle in the east, north, and zenith directions respectively.

[0051] S1 includes S1.2. Obtain the parameters required for attitude correction through the sensors mounted on the USBL at the sea surface. The parameters required for attitude correction include the heading angle , pitch angle and roll angle , and establish the coordinate transformation matrix :

[0052] .

[0053] S1 includes S1.3. Utilize the lever - arm measurement information between the GNSS receiver and the center of the USBL transmitting unit on the sea - surface vehicle to calculate the position of the center of the USBL array unit on the sea surface :

[0054] ;

[0055] In the formula, , and are the components of the position of the center of the USBL array unit on the sea surface in the east, north, and zenith directions respectively, , and are the components of the lever - arm measurement information between the GNSS receiver and the center of the USBL transmitting unit on the sea - surface vehicle in the east, north, and zenith directions respectively.

[0056] S2 includes S2.1. Select the average sound - speed profile of the set of historically measured sound - speed profiles as the reference profile , and the reference sound - speed profile is composed of depth and sound - speed data;

[0057] S2.2. Obtain the temperature, salinity, and depth observation data through the CTD acoustic sensor carried by the underwater vehicle, and calculate the in - situ observed sound - speed value related to time and depth according to the sound - speed empirical formula .

[0058] S2 includes S2.3. Set a sliding window and, according to the depth Calculate the difference between the calculated reference sound speed profile and the in-situ sound speed observations, select a sliding window with a width of , and perform a weighted average of the sound speed difference data within the window to obtain the current sound speed correction value based on the in-situ sound speed observations :

[0059] ;

[0060] wherein, is the weight factor, which is affected by the degree of temporal correlation between the observation epochs in the moving window and the selected sampling time, is the epoch index within the window, is the epoch index time within the window.

[0061] S3 includes performing time measurement based on the corrected historical fixed sound speed profile, obtaining the propagation delay and the corrected sound speed, and re-positioning the underwater vehicle.

[0062] S3 includes S3.1. Overall correction of the reference profile based on the sound speed correction value to obtain the corrected sound speed profile , and performing ray tracing according to to obtain the representative sound speed value .

[0063] S3 includes S3.2. Calculating the direction vector between the surface USBL receiver and the underwater target according to the time difference of arrival of each transmitter :

[0064] ;

[0065] ;

[0066] ;

[0067] wherein, is the intermediate parameter, is the time difference of arrival, is the relative position of the receiver combination, is the first-order difference operator matrix, is the coordinates of N receivers in the USBL array element, , and are the components of the surface USBL receiver in the east, north, and zenith directions respectively, , and are the components of the direction vector between the underwater targets in the east, north, and zenith directions respectively, , and are respectively the components of the direction vector of the underwater vehicle in the east, north, and zenith directions;

[0068] It is expressed as:

[0069] .

[0070] S3 includes S3.3. Re - conduct ray tracing based on the corrected historical fixed sound speed profile to obtain updated travel times, calculate the underwater target position based on the updated travel times, corrected sound speed, and direction vector, and average the results obtained for N transmitters to obtain the real - time position of the underwater vehicle in the geographic coordinate system :

[0071] ;

[0072] In the formula, is the transmitter number in the transmitting array, is the transmitter 's travel time, is equivalent to the direction vector of the underwater vehicle, , and are respectively 's components in the east, north, and zenith directions, , and are respectively the components of the real - time position of the underwater vehicle in the geographic coordinate system in the east, north, and zenith directions.

[0073] The technical flow chart of the present invention is as shown in Figure 1 and includes obtaining the position of the GNSS antenna, using the attitude observation data obtained by the attitude sensor to perform attitude correction to obtain the position of the center of the ultra - short baseline USBL array element; obtaining real - time in - situ sound speed observation information through the CTD acoustic sensor carried by the underwater vehicle, and correcting the historical fixed sound speed profile SVP based on the real - time in - situ sound speed information; re - conducting ray tracing based on the corrected historical fixed sound speed profile to perform real - time positioning of the underwater vehicle.

[0074] The embodiments of the present invention use the real observation data during the operation of the underwater vehicle. First, a rough motion trajectory of the underwater vehicle is given. The rough motion trajectories in the horizontal direction and the vertical direction are respectively as shown in Figure 2 and Figure 3As shown, it can be seen that as the underwater vehicle goes through the operation process of "diving, performing tasks, and surfacing", the depth changes significantly. Generally, a fixed sound speed value is adopted in underwater positioning, or a certain historical sound speed profile is selected as the fixed sound speed profile. Therefore, in order to verify the comparison of the modified sound speed profile corrected based on in-situ sound speed observation adopted in the present invention with the effect of using a fixed sound speed value, the fixed empirical sound speed profile used for comparison is as Figure 4 shown, which is obtained by averaging the data of the sound speed profile set acquired by the shipborne profiler, and this is used as the fixed sound speed profile. At 4-hour intervals, Figure 5 shows the time variation of the sound speed profile. It can be seen that at a water depth of 50m, the sound speed changes are relatively complex. In other water depth areas, the variation range is relatively small, but the characteristics of significant variation with time can still be seen. Therefore, the assumption of "constant sound speed over time" on which the traditional method using a fixed sound speed profile is based does not conform to the actual situation.

[0075] In order to correct the fixed sound speed profile using the in-situ sound speed observation information, the characteristics of the in-situ sound speed observation data were first analyzed. Figure 6 shows the variation of the sound speed observed in-situ by the acoustic sensor carried by the underwater vehicle over time, which has a strong correlation with the depth of the underwater vehicle. In order to determine the feasibility of correcting the in-situ sound speed observation, a comparison between the in-situ sound speed and the equivalent sound speed at a fixed water depth was first carried out. Three typical cases of the shallow part, middle part, and deep part at 50m, 150m, and 300m were respectively selected, and the acoustic ray tracing was used to calculate the equivalent sound speed. The differences between the two are respectively as Figure 7 , Figure 8 and Figure 9 shown. It can be seen that the difference trends in the three cases are generally consistent, especially in the cases of 150m and 300m, the variation trends are more consistent. Further, the correlation between the two was calculated from a quantitative perspective, and the calculation results are as Figure 10 shown. It can be seen that in the water depth environment of 300m, under most water depth conditions, the in-situ sound speed and the equivalent sound speed show a good positive correlation. Especially in the case of the underwater vehicle operating near the bottom, the correlation is obvious, providing an analysis reference for using the in-situ sound speed observation to correct the sound speed profile.

[0076] The positioning effects were compared using three methods respectively, and the results are as Figure 11 shown. The positioning result of the method using a fixed sound speed value is most affected by the representative error of the sound speed and has the worst positioning effect. The method using a fixed sound speed profile improves the positioning accuracy of the above method to a certain extent. The method of the present invention further corrects the sound speed profile based on the in-situ sound speed observation information, taking into account the actual situation of the sound speed changing over time, and is more in line with the characteristics of the real ocean environment, so the positioning accuracy is the highest.

[0077] Considering the actual situation of the underwater vehicle navigation and positioning environment and taking into account the time-varying characteristics of SVP, the present invention uses the real-time information obtained by the relevant sensors carried on the underwater vehicle, combines in-situ sound velocity observations, corrects the historical sound velocity profile, thereby obtaining the corrected sound velocity profile. Then, based on the corrected sound velocity profile, ray tracing is performed to obtain a new representative sound velocity value, and distance information is obtained based on the propagation delay and the representative sound velocity value to locate the underwater moving target. The present invention improves the defect that the historical sound velocity profile cannot reflect the time-varying characteristics during the underwater vehicle navigation and positioning process, and improves the underwater navigation and positioning results.

[0078] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features, 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; 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 ; 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.

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: 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.

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

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 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: 。 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.

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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