UUVs formation clock synchronization method and system based on opposite virtual observation
By adopting a clock synchronization method based on opposite virtual observations in the UUVs formation, using the IMU and the pressure depth meter to obtain position information, calculate the relative clock difference and adjust the difference, the problem of low clock alignment accuracy in the UUVs formation is solved, and high-precision clock synchronization and collaborative navigation are achieved.
Patent Information
- Application Number
- CN202411673824.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-21
- Publication Date
- 2025-04-08
AI Technical Summary
In the collaborative navigation of UUVs formations, the clock difference calculation is not tight, the clock alignment accuracy is low, and high-precision clock synchronization cannot be achieved.
The UUVs formation clock synchronization method based on opposing virtual observations is adopted, and the horizontal component and depth change information is obtained through the IMU and the pressure depth meter, the relative clock difference between all UUVs in the UUVs formation is calculated, and the difference is performed through the least squares principle to eliminate clock inconsistencies.
It improves the synchronization accuracy of UUVs formation clocks, improves the accuracy of collaborative navigation, reduces the cost of UUV manufacturing, and promotes the efficiency of underwater activities during long-term flights.
Smart Images
Figure CN119781509A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of collaborative navigation and positioning data processing of multiple unmanned underwater vehicles (UUVs), and in particular to a clock synchronization method and system for a UUVs formation based on opposite virtual observation. Background Art
[0002] Multi-robot collaborative operation is one of the effective ways to improve the efficiency and quality of robot operations. In underwater missions such as ocean exploration and scientific investigation, the collaborative work of UUVs formation has become a research hotspot and one of the main development trends of UUVs. In the process of UUVs formation collaborative operation, the relative position and posture between each UUV play a key role, especially in underwater tasks with high precision requirements such as underwater terrain measurement and target tracking. Therefore, the collaborative navigation of UUVs formation has become a key factor restricting the collaborative operation of UUVs formation. At present, the collaborative navigation of UUVs formation is mainly achieved through mutual hydroacoustic ranging observations, but hydroacoustic ranging requires clock synchronization between UUVs. In order to ensure that the clocks of each UUV in the UUVs formation are synchronized, one of the existing methods is: UUVs regularly surface to receive GNSS signals, solve the UUV position and clock error to correct the UUV position and clock, so as to achieve clock synchronization between UUV and GNSS system. This method requires the UUVs formation to surface regularly, which will consume a lot of energy and reduce the operating efficiency of the UUVs formation. The second existing method is: the UUV is equipped with a high-precision clock, and the clock is aligned through GNSS signals before the UUV is launched. During underwater activities, the influence of clock drift is directly ignored. This method requires a high-precision clock, which increases the manufacturing cost of the UUV and is difficult to apply to long-duration underwater operation scenarios. The third existing method is: using the opposite distance observation value between the UUVs (the distance observation value from UUV1 to UUV2 and the distance observation value from UUV2 to UUV1 are called opposite distance observation values) and the average sound speed c to calculate the clock difference between the two, such as Figure 1 shown.
[0003] exist Figure 1 In the example, UUV1 sends an acoustic signal at time t1 (UUV1 is at point A1 at this time), and UUV2 receives the signal at time t2 (UUV2 is at point B1 at this time) to complete the distance measurement S from point A1 to point B1. AB =(t2-t1)c, where: the time value of t1 is provided by the clock carried by UUV1, and the time value of t2 is provided by the clock carried by UUV2; UUV2 transmits an acoustic signal at time t3, and UUV1 receives the signal at time t4 to complete the distance measurement S from point B2 to point A2 BA =(t4-t3)c, where: the time value of t3 is provided by the clock carried by UUV2, and the time value of t4 is provided by the clock carried by UUV11. The clock difference calculation formula of method three is:
[0004]
[0005] Obviously, this method ignores the influence of the dynamic change of the UUV position. Due to the influence of ocean phenomena such as ocean currents and internal waves, the position change of the UUV is inevitable and it is impossible to achieve absolute stillness. Therefore, this method is not rigorous in theory and cannot achieve high-precision clock alignment. Summary of the invention
[0006] The present invention aims to solve the problems of inaccurate clock error calculation and low clock alignment accuracy caused by UUV position changes, and proposes a UUVs formation clock synchronization method and system based on opposite virtual observation. The IMU and pressure depth gauge are used to obtain horizontal component and depth change information, which can effectively improve the clock synchronization accuracy of the UUVs formation, thereby improving the collaborative navigation accuracy of the UUVs formation.
[0007] To achieve the above purpose, the technical solution adopted is:
[0008] A clock synchronization method for a UUVs formation based on opposite virtual observation, comprising:
[0009] Firstly, the acoustic signal propagation delay and average sound speed are used to calculate the underwater acoustic ranging value, and the forward and reverse distance observation values between all UUVs in the UUVs formation are obtained;
[0010] According to the UUV autonomous navigation results, the horizontal displacement and vertical displacement of UUV1 from the moment when UUV1 sends an acoustic signal to UUV2 to the moment when UUV1 receives the acoustic signal sent by UUV2, and the horizontal displacement and vertical displacement of UUV2 from the moment when UUV2 receives the acoustic signal sent by UUV1 to the moment when UUV2 sends an acoustic signal to UUV1 are obtained;
[0011] Using the position information obtained by the autonomous navigation of the two UUVs, the direction vector from the position of UUV2 at the time when UUV2 sends the acoustic signal to UUV1 to the position of UUV1 at the time when UUV1 receives the acoustic signal sent by UUV2 is calculated;
[0012] Construct the opposite virtual distance observation value between the two UUVs, and convert the reverse distance observation value into the opposite observation value of the corresponding spatial position of the forward distance observation value;
[0013] The relative clock difference between the two UUVs is calculated using the forward distance observations and the opposite virtual distance observations.
[0014] According to the above steps, the relative clock differences between all UUVs are calculated to eliminate the inconsistency of the UUV clock caused by calibrating the UUV clock with different relative clock differences.
[0015] According to the clock synchronization method of the UUVs formation based on opposite virtual observation of the present invention, further, obtaining the forward and reverse distance observation values between all UUVs in the UUVs formation includes:
[0016] Any two UUVs in the UUVs formation are UUV1 and UUV2, and the forward and reverse distance observation values between them are S AB , S BA Since both UUVs are in motion, the forward and reverse distance observation values S AB , S BA The distances are not the same spatial positions; UUV1 sends an acoustic signal at time t1, and UUV2 receives the acoustic signal at time t2; UUV2 sends an acoustic signal at time t3, and UUV1 receives the acoustic signal at time t4; where S AB is the spatial distance from the position of UUV1 at time t1 to the position of UUV2 at time t2, S BA It is the spatial distance from the position of UUV2 at time t3 to the position of UUV1 at time t4. t1, t2, t3, and t4 are arranged in chronological order.
[0017] According to the UUVs formation clock synchronization method based on opposite virtual observation of the present invention, further, according to the IMU carried by the UUV, the horizontal displacement (Δx1, Δy1) of UUV1 from time t1 to time t4 and the horizontal displacement (Δx2, Δy2) of UUV2 from time t2 to time t3 are obtained.
[0018] According to the clock synchronization method of UUVs formation based on opposite virtual observation of the present invention, further, according to the depth value measured by the pressure depth gauge carried by the UUV, the vertical displacement Δh1 of UUV1 from time t1 to time t4 and the vertical displacement Δh2 of UUV2 from time t2 to time t3 are obtained.
[0019] According to the clock synchronization method of UUVs formation based on opposite virtual observation of the present invention, further, the direction vector from the position of UUV2 at time t3 to the position of UUV1 at time t4 is calculated. The calculation formula of the direction vector in the navigation coordinate system is as follows:
[0020] Δp 21 =S BA ·(p1-p2) / ||p1-p2||
[0021] In the formula, Δp 21 =[Δx 21 Δy 21 Δh 21 ] TIt is the three-dimensional coordinate vector from the position of UUV2 at time t3 to the position of UUV1 at time t4; p1 represents the spatial position of UUV1 at time t4, and p2 represents the spatial position of UUV2 at time t3.
[0022] According to the clock synchronization method of UUVs formation based on opposite virtual observation of the present invention, further, the opposite virtual distance observation value between two UUVs is constructed, and the calculation formula is as follows:
[0023]
[0024] According to the clock synchronization method of UUVs formation based on opposite virtual observation of the present invention, further, using the forward distance observation value S AB and the opposite virtual distance observation value S′ BA , calculate the relative clock difference between the two UUVs, the calculation formula is as follows:
[0025]
[0026] Where c is the average speed of sound.
[0027] According to the clock synchronization method of a UUVs formation based on opposite virtual observation of the present invention, further, eliminating the inconsistency of the UUV clock caused by calibrating the UUV clock using different relative clock differences comprises:
[0028] First, the error equation is established with the relative clock error as the observation value:
[0029]
[0030] Where i and j represent the UUV number, ΔT ij is the relative clock difference observation value of the clocks on board the two UUVs; It indicates the clock value of the two UUVs under the same time reference, that is, the calibrated clock;
[0031] Then the least squares principle is used to calculate Where n represents the number of UUVs in the UUVs formation;
[0032] Finally, the relative clock difference between each UUV is calculated And perform clock alignment.
[0033] Furthermore, the present invention also provides a UUVs formation clock synchronization system based on opposite virtual observation, comprising:
[0034] The underwater acoustic ranging value calculation module is used to calculate the underwater acoustic ranging value by using the acoustic signal propagation delay and the average sound speed, and obtain the forward and reverse distance observation values between all UUVs in the UUVs formation;
[0035] The horizontal and vertical displacement acquisition module is used to acquire the horizontal displacement and vertical displacement of UUV1 from the moment when UUV1 sends an acoustic signal to UUV2 to the moment when UUV1 receives the acoustic signal sent by UUV2, and the horizontal displacement and vertical displacement of UUV2 from the moment when UUV2 receives the acoustic signal sent by UUV1 to the moment when UUV2 sends the acoustic signal to UUV1 according to the UUV autonomous navigation result;
[0036] A direction vector calculation module is used to calculate the direction vector from the position of UUV2 at the time when UUV2 sends an acoustic signal to UUV1 to the position of UUV1 at the time when UUV1 receives the acoustic signal sent by UUV2 using the position information obtained by the autonomous navigation of the two UUVs;
[0037] The opposite virtual distance observation value construction module is used to construct the opposite virtual distance observation value between the two UUVs, and convert the reverse distance observation value into the opposite observation of the corresponding spatial position of the forward distance observation value;
[0038] The relative clock error observation value calculation module is used to calculate the relative clock error between two UUVs using the forward distance observation value and the opposite virtual distance observation value;
[0039] The adjustment module is used to calculate the relative clock differences between all UUVs and eliminate the inconsistency of the UUV clock caused by calibrating the UUV clock with different relative clock differences.
[0040] The beneficial effects achieved by adopting the above technical solution are:
[0041] In view of the clock synchronization problem faced by the UUVs formation cooperative navigation based on hydroacoustic ranging observation values, the present invention proposes a UUVs formation clock synchronization method based on opposite virtual observation. First, the UUV does not need to be equipped with a high-precision clock, which reduces the manufacturing cost of the UUV; second, it does not need to surface regularly, which ensures the operating efficiency of the UUV and promotes the long-term underwater activities of the UUV; third, the acoustic transducer, inertial sensor (IMU) and pressure depth gauge measurement information carried by the UUV are fully utilized, and the clock error calculation method is theoretically rigorous and highly accurate. Under the premise of not affecting the UUV structure, not increasing the UUV manufacturing cost, and not reducing the UUV operating efficiency, the present invention only uses the inherent information of the UUV-carried sensor to achieve high-precision clock synchronization, thereby improving the UUVs formation cooperative navigation accuracy and task execution capability. BRIEF DESCRIPTION OF THE DRAWINGS
[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings of the embodiments of the present invention, wherein the drawings are only used to illustrate some embodiments of the present invention, but not to limit all embodiments of the present invention thereto.
[0043] Figure 1This is a schematic diagram of the mutual observation between UUVs under dynamic navigation;
[0044] Figure 2 It is a flow chart of a clock synchronization method for a UUVs formation based on opposite virtual observation according to an embodiment of the present invention. DETAILED DESCRIPTION
[0045] The following will be combined with the drawings of specific embodiments of the present invention to clearly and completely describe the exemplary scheme of the embodiment of the present invention. Unless otherwise defined, the technical terms or scientific terms used in the present invention should be the common meanings understood by people with ordinary skills in the field.
[0046] High-precision cooperative navigation of UUVs formation has become a research hotspot in the field of robotics and underwater navigation. Improving the clock alignment accuracy between UUVs will directly improve the accuracy of hydroacoustic ranging, thereby improving the relative position accuracy of the UUVs formation. Therefore, clock synchronization is an important factor in determining the accuracy of UUVs formation cooperative navigation. Among the three existing clock synchronization methods, method three does not require regular surfacing, nor does it require a high-precision clock, which is beneficial to the long flight time and low cost of UUVs. However, the existing method three has the problem of inaccurate theory and low clock alignment accuracy due to the failure to consider the dynamic changes in the spatial position of UUVs. To this end, this embodiment discloses a clock synchronization method for UUVs formation based on opposing virtual observations, such as Figure 2 As shown, the following steps are included:
[0047] Step S101, using the acoustic signal propagation delay and the average sound speed to calculate the underwater acoustic ranging value, and obtain the forward and reverse distance observation values between all UUVs in the UUVs formation.
[0048] Take any two UUVs in the UUVs formation as an example (named UUV1 and UUV2), the forward and reverse distance observation values between the two are S AB , S BA .like Figure 1 As shown, since both UUVs are in motion, the forward and reverse distance observation values S AB , S BA Not the distance of the same spatial position. UUV1 sends an acoustic signal at time t1, and UUV2 receives the acoustic signal at time t2; UUV2 sends an acoustic signal at time t3, and UUV1 receives the acoustic signal at time t4. AB is the spatial distance from the position of UUV1 at time t1 to the position of UUV2 at time t2, S BA It is the spatial distance from the position of UUV2 at time t3 to the position of UUV1 at time t4. t1, t2, t3, and t4 are arranged in chronological order.
[0049] Step S102: According to the IMU carried by the UUV, the horizontal displacement (Δx1, Δy1) of UUV1 from time t1 to time t4 and the horizontal displacement (Δx2, Δy2) of UUV2 from time t2 to time t3 are obtained.
[0050] Step S103 , obtaining the vertical displacement Δh1 of UUV1 from time t1 to time t4 and the vertical displacement Δh2 of UUV2 from time t2 to time t3 according to the depth value measured by the pressure depth gauge carried by the UUV.
[0051] Step S104: Calculate the direction vector from the position of UUV2 at time t3 to the position of UUV1 at time t4 using the position information obtained by the autonomous navigation of the two UUVs. The calculation formula of the direction vector in the navigation coordinate system is as follows:
[0052] Δp 21 =S BA ·(p1-p2) / ||p1-p2||
[0053] In the formula, Δp 21 =[Δx 21 Δy 21 Δh 21 ] T is the three-dimensional coordinate vector from the position of UUV2 at time t3 to the position of UUV1 at time t4; p1 represents the spatial position of UUV1 at time t4 (obtained by autonomous navigation); p2 represents the spatial position of UUV2 at time t3 (obtained by autonomous navigation).
[0054] Step S105: construct the virtual distance observation value between the two UUVs, and convert the distance observation value S BA Calculated as S AB The calculation formula for the opposite observation of the corresponding spatial position is as follows.
[0055]
[0056] Step S106: Calculate the relative clock difference between the two UUVs. The calculation formula is as follows:
[0057]
[0058] Where c is the average speed of sound.
[0059] Step S107, calculate the relative clock differences between all UUVs according to steps S101-S106. Since the calculated relative clock differences contain errors, there will be inconsistencies when a certain UUV clock is calibrated with different relative clock differences. For example, the clock of UUV3 is calibrated by the relative clock difference between UUV1 clock, UUV1 UUV2, and the relative clock difference between UUV2 UUV3, which is different from the result of calibrating the clock of UUV3 by the relative clock difference between UUV1 clock and UUV1UUV3. Therefore, it is necessary to eliminate the inconsistency of the UUV clock caused by calibrating the UUV clock with different relative clock differences.
[0060] (1) Taking the relative clock error as the observation value, the error equation is established as follows:
[0061]
[0062] Where i and j represent the UUV number, ΔT ij is the relative clock difference observation value of the clocks on board the two UUVs; It indicates the clock value of the clocks on the two UUVs under the same time reference, that is, the calibrated clock.
[0063] (2) The relative clock error is regarded as an independent observation with equal precision (that is, equal weight) and is calculated using the least squares principle. Where n represents the number of UUVs in the UUVs formation.
[0064] (3) Calculate the relative clock difference between UUVs The clocks are aligned to keep the UUVs formation on a unified time basis. The clock error after adjustment using the least squares principle can ensure that the clock error after calibration on different routes remains consistent.
[0065] Corresponding to the above method, this embodiment also discloses a UUVs formation clock synchronization system based on opposite virtual observation, including:
[0066] The underwater acoustic ranging value calculation module is used to calculate the underwater acoustic ranging value using the acoustic signal propagation delay and the average sound speed, and obtain the forward and reverse distance observation values between all UUVs in the UUVs formation.
[0067] The horizontal and vertical displacement acquisition module is used to obtain the horizontal displacement and vertical displacement of UUV1 from the moment when UUV1 sends an acoustic signal to UUV2 to the moment when UUV1 receives the acoustic signal sent by UUV2, and the horizontal displacement and vertical displacement of UUV2 from the moment when UUV2 receives the acoustic signal sent by UUV1 to the moment when UUV2 sends the acoustic signal to UUV1 according to the UUV autonomous navigation result.
[0068] The direction vector calculation module is used to calculate the direction vector from the position of UUV2 at the time when UUV2 sends the sound signal to UUV1 to the position of UUV1 at the time when UUV1 receives the sound signal sent by UUV2 using the position information obtained by the autonomous navigation of the two UUVs.
[0069] The opposite virtual distance observation value construction module is used to construct the opposite virtual distance observation value between two UUVs and convert the reverse distance observation value into the opposite observation of the corresponding spatial position of the forward distance observation value.
[0070] The relative clock difference observation value calculation module is used to calculate the relative clock difference between two UUVs using the forward distance observation value and the opposite virtual distance observation value.
[0071] The adjustment module is used to calculate the relative clock differences between all UUVs and eliminate the inconsistency of the UUV clock caused by calibrating the UUV clock with different relative clock differences.
[0072] The present invention effectively utilizes the information of sensors such as acoustic transducers, IMUs, and pressure depth gauges carried by UUVs, and constructs opposite virtual distance observation values to calculate the relative clock difference between any two UUVs. On this basis, the optimal estimate of the relative clock difference between each UUV is calculated using the least squares principle, thus achieving clock synchronization of the UUVs formation.
[0073] Unless otherwise specifically stated, the relative steps, numerical expressions and values of the components and steps set forth in these embodiments do not limit the scope of the present invention.
[0074] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.
[0075] The units and method steps of each example described in conjunction with the embodiments disclosed herein can be implemented by electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. A person of ordinary skill in the art may use different methods to implement the described functions for each specific application, but such implementation is not considered to be beyond the scope of the present invention.
[0076] Those skilled in the art will appreciate that all or part of the steps in the above method can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable storage medium, such as a read-only memory, a disk or an optical disk. Optionally, all or part of the steps in the above embodiment can also be implemented using one or more integrated circuits, and accordingly, each module / unit in the above embodiment can be implemented in the form of hardware or in the form of software function modules. The present invention is not limited to any specific form of combination of hardware and software.
[0077] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention is described in detail with reference to the above-described embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the above-described embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims
1. A clock synchronization method for UUVs formation based on opposite virtual observation, characterized in that: include: Firstly, the acoustic signal propagation delay and average sound speed are used to calculate the underwater acoustic ranging value, and the forward and reverse distance observation values between all UUVs in the UUVs formation are obtained; According to the UUV autonomous navigation results, the horizontal displacement and vertical displacement of UUV1 from the moment when UUV1 sends an acoustic signal to UUV2 to the moment when UUV1 receives the acoustic signal sent by UUV2, and the horizontal displacement and vertical displacement of UUV2 from the moment when UUV2 receives the acoustic signal sent by UUV1 to the moment when UUV2 sends an acoustic signal to UUV1 are obtained; Using the position information obtained by the autonomous navigation of the two UUVs, the direction vector from the position of UUV2 at the moment when UUV2 sends the acoustic signal to UUV1 to the position of UUV1 at the moment when UUV1 receives the acoustic signal sent by UUV2 is calculated; Construct the opposite virtual distance observation value between the two UUVs, and convert the reverse distance observation value into the opposite observation value of the corresponding spatial position of the forward distance observation value; The relative clock difference between the two UUVs is calculated using the forward distance observations and the opposite virtual distance observations. According to the above steps, the relative clock differences between all UUVs are calculated to eliminate the inconsistency of the UUV clock caused by calibrating the UUV clock with different relative clock differences.
2. The clock synchronization method for UUVs formation based on opposite virtual observation according to claim 1 is characterized in that: Obtaining the forward and reverse distance observation values between all UUVs in the UUVs formation includes: Any two UUVs in the UUVs formation are UUV1 and UUV2, and the forward and reverse distance observation values between them are S AB , S BA Since both UUVs are in motion, the forward and reverse distance observation values S AB , S BA The distances are not the same spatial positions; UUV1 sends an acoustic signal at time t1, and UUV2 receives the acoustic signal at time t2; UUV2 sends an acoustic signal at time t3, and UUV1 receives the acoustic signal at time t4; where S AB is the spatial distance from the position of UUV1 at time t1 to the position of UUV2 at time t2, S BA It is the spatial distance from the position of UUV2 at time t3 to the position of UUV1 at time t4. t1, t2, t3, and t4 are arranged in chronological order.
3. The clock synchronization method for UUVs formation based on opposite virtual observation according to claim 2 is characterized in that: According to the IMU carried by the UUV, the horizontal displacement (Δx1, Δy1) of UUV1 from time t1 to time t4 and the horizontal displacement (Δx2, Δy2) of UUV2 from time t2 to time t3 are obtained.
4. The clock synchronization method for UUVs formation based on opposite virtual observation according to claim 3 is characterized in that: According to the depth value measured by the pressure depth gauge carried on the UUV, the vertical displacement Δh1 of UUV1 from time t1 to time t4 and the vertical displacement Δh2 of UUV2 from time t2 to time t3 are obtained.
5. The clock synchronization method for UUVs formation based on opposite virtual observation according to claim 4 is characterized in that: Calculate the direction vector from the position of UUV2 at time t3 to the position of UUV1 at time t4. The calculation formula of the direction vector in the navigation coordinate system is as follows: Δp 21 =S BA ·(p1-p2) / ||p1-p2|| In the formula, Δp 21 =[Δx 21 Δy 21 Δh 21 ] T It is the three-dimensional coordinate vector from the position of UUV2 at time t3 to the position of UUV1 at time t4; p1 represents the spatial position of UUV1 at time t4, and p2 represents the spatial position of UUV2 at time t3.
6. The clock synchronization method for UUVs formation based on opposite virtual observation according to claim 5 is characterized in that: Construct the virtual distance observation value between the two UUVs, and the calculation formula is as follows:
7. The clock synchronization method for UUVs formation based on opposite virtual observation according to claim 6 is characterized in that: Using the forward distance observation S AB and the opposite virtual distance observation value S′ BA , calculate the relative clock difference between the two UUVs, the calculation formula is as follows: Where c is the average speed of sound.
8. The clock synchronization method for UUVs formation based on opposite virtual observation according to claim 7 is characterized in that: Eliminating the inconsistency of the UUV clock caused by calibrating the UUV clock with different relative clock errors includes: First, the error equation is established with the relative clock error as the observation value: Where i and j represent the UUV number, ΔT ij is the relative clock difference observation value of the clocks on board the two UUVs; It indicates the clock value of the two UUVs under the same time reference, that is, the calibrated clock; Then the least squares principle is used to calculate Where n represents the number of UUVs in the UUVs formation; Finally, the relative clock difference between each UUV is calculated And perform clock alignment.
9. A UUVs formation clock synchronization system based on opposite virtual observation, characterized in that: include: The underwater acoustic ranging value calculation module is used to calculate the underwater acoustic ranging value by using the acoustic signal propagation delay and the average sound speed, and obtain the forward and reverse distance observation values between all UUVs in the UUVs formation; The horizontal and vertical displacement acquisition module is used to acquire the horizontal displacement and vertical displacement of UUV1 from the moment when UUV1 sends an acoustic signal to UUV2 to the moment when UUV1 receives the acoustic signal sent by UUV2, and the horizontal displacement and vertical displacement of UUV2 from the moment when UUV2 receives the acoustic signal sent by UUV1 to the moment when UUV2 sends the acoustic signal to UUV1 according to the UUV autonomous navigation result; A direction vector calculation module is used to calculate the direction vector from the position of UUV2 at the time when UUV2 sends an acoustic signal to UUV1 to the position of UUV1 at the time when UUV1 receives the acoustic signal sent by UUV2 using the position information obtained by the autonomous navigation of the two UUVs; The opposite virtual distance observation value construction module is used to construct the opposite virtual distance observation value between the two UUVs, and convert the reverse distance observation value into the opposite observation of the corresponding spatial position of the forward distance observation value; The relative clock error observation value calculation module is used to calculate the relative clock error between two UUVs using the forward distance observation value and the opposite virtual distance observation value; The adjustment module is used to calculate the relative clock differences between all UUVs and eliminate the inconsistency of the UUV clock caused by calibrating the UUV clock with different relative clock differences.
10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 8 are implemented.