Underwater cluster vehicle cooperative positioning system and method based on wireless optical communication

Abstract

The present application relates to underwater cluster vehicle positioning system and method, specifically relates to a kind of underwater cluster vehicle cooperative positioning system and method based on wireless optical communication, solve the technical problems that existing underwater cluster vehicle is difficult to guarantee the consistency and cooperation between nodes.The underwater cluster vehicle cooperative positioning system based on wireless optical communication provided by the present application is based on underwater wireless optical communication technology, communication rate is high, delay is low, transmission capacity is large, and the time reference unit of main node positioning device is used to synchronize and tame the crystal oscillator in clock synchronization and tame unit in slave node positioning device, to realize the cooperative time service of multiple slave node underwater vehicles, and further ensure positioning accuracy;At the same time, the autonomous navigation unit of underwater vehicle itself can be used, and only one main node underwater vehicle equipped with high-precision main node autonomous navigation unit and time reference unit can realize the cooperative positioning of underwater cluster vehicle.

Description

TECHNICAL FIELD

[0001] The present application relates to an underwater cluster vehicle positioning system and method, in particular to an underwater cluster vehicle cooperative positioning system and method based on wireless optical communication. BACKGROUND

[0002] At present, the global navigation satellite system (GNSS) represented by the GPS system of the United States, the GLONASS system of Russia, the BDS system of China and the Galileo system of the European Union has obtained extremely wide application in resource environment, surveying and mapping, disaster prevention and mitigation, power and telecommunications, transportation and other fields, and plays an irreplaceable role. However, due to the rapid and strong attenuation of radio signals in water, it cannot be transmitted over long distances, so GNSS is limited to space, land, water surface and other environmental applications.

[0003] Underwater vehicles, as multipliers of ocean exploration forces, can carry out scientific activities in great depths and dangerous waters that humans cannot reach, and have received widespread attention and attention from scientists around the world. Underwater cluster vehicles not only can complete all functions and efficiency of single underwater vehicles, but also can undertake many complex tasks that single underwater vehicles cannot handle, and ultimately can achieve greater working area, stronger maneuvering flexibility, higher working efficiency, better reliability and fault tolerance.

[0004] For underwater vehicles, inertial navigation system is a completely autonomous navigation mode that does not rely on external information, so it has been widely used in underwater navigation field. However, its inherent navigation error accumulates with time, which is not conducive to long-time high-precision navigation of underwater vehicles, and may also be affected by factors such as ocean environment, ocean current interference, and hydrological parameter changes. Further, high-precision inertial navigation systems are often expensive, which is not conducive to the expansion of large-scale commercial applications. Therefore, it has become a development trend to realize cooperative positioning and calibration of underwater cluster vehicles equipped with low-precision inertial navigation systems by equipping a single / few underwater vehicles with high-precision inertial navigation systems or regularly surfacing to obtain high-precision time and position coordinates. However, for high-precision cooperation among underwater cluster vehicles, how to ensure the consistency and cooperation of each node of underwater cluster vehicles has become a key technical problem to be solved. SUMMARY

[0005] The purpose of the present application is to solve the technical problem that the existing underwater cluster vehicles are difficult to ensure the consistency and cooperation among nodes, and to provide an underwater cluster vehicle cooperative positioning system and method based on wireless optical communication.

[0006] To achieve the above purpose, the technical scheme adopted by the present application is:

[0007] An underwater cluster vehicle cooperative positioning system based on wireless optical communication, the underwater cluster vehicle comprising one master node underwater vehicle and N slave node underwater vehicles, wherein N is an integer and N≥2; the master node underwater vehicle is provided with a master node autonomous navigation unit for measuring the real-time position of the master node; the N slave node underwater vehicles are respectively provided with slave node autonomous navigation units for measuring the position change of the slave nodes; the special feature is that it comprises a master node positioning device arranged on the master node underwater vehicle and N slave node positioning devices respectively arranged on the N slave node underwater vehicles.

[0008] The master node positioning device comprises a time reference unit and a master node underwater wireless optical communication unit, the first output end of the time reference unit is connected with the first input end of the master node underwater wireless optical communication unit, the second output end is connected with the control end of the master node autonomous navigation unit, for measuring the time of local receiving and sending data, and generating the control clock of the master node autonomous navigation unit; the second input end of the master node underwater wireless optical communication unit is connected with the output end of the master node autonomous navigation unit, and the output end is connected with the input end of the time reference unit.

[0009] The slave node positioning device comprises a clock synchronization and taming unit, a slave node underwater wireless optical communication unit and a ranging and positioning unit.

[0010] The first output end of the clock synchronization and taming unit is connected with the input end of the slave node underwater wireless optical communication unit and the first input end of the ranging and positioning unit respectively, and the second output end is connected with the control end of the slave node autonomous navigation unit, for obtaining the time clock difference of the master node positioning device and the slave node positioning device, and performing collaborative timing and taming, and generating the control clock of the slave node autonomous navigation unit;

[0011] The first output end of the slave node underwater wireless optical communication unit is connected with the input end of the clock synchronization and taming unit, and the second output end is connected with the second input end of the ranging and positioning unit; the third input end of the ranging and positioning unit is connected with the output end of the slave node autonomous navigation unit, and the output end is connected with the input end of the slave node autonomous navigation unit, and the ranging and positioning unit is used for calculating the real-time position of the slave node underwater vehicle, and completing the collaborative positioning of the underwater vehicle.

[0012] Further, the master node positioning device further comprises a master node power supply unit, the input end of the master node power supply unit is connected with the output end of the master node external power unit, and the output end is connected with the power supply end of the time reference unit and the master node underwater wireless optical communication unit respectively;

[0013] The slave node positioning device further comprises a slave node power supply unit; the input end of the slave node power supply unit is connected with the output end of the slave node external power unit, and the output end is connected with the power supply end of the clock synchronization and taming unit, the slave node underwater wireless optical communication unit and the ranging and positioning unit respectively.

[0014] Further, the master node positioning device further comprises a master node watertight packaging shell and a master node network data interaction cable;

[0015] The time reference unit, the master node underwater wireless optical communication unit and the master node power supply unit are located in the master node watertight packaging shell, the master node watertight packaging shell is provided with a master node interaction port, one end of the master node network data interaction cable is connected with the second output end of the time reference unit, the second input end of the master node underwater wireless optical communication unit and the input end of the master node power supply unit through the master node interaction port respectively, and the other end is connected with the control end and the output end of the master node autonomous navigation unit and the output end of the master node external power unit respectively;

[0016] The slave node positioning device further comprises a slave node watertight packaging shell and a slave node network data interaction cable;

[0017] The clock synchronization and domestication unit, the slave node underwater wireless optical communication unit, the ranging and positioning unit and the slave node power supply unit are located in the slave node watertight packaging shell, the slave node watertight packaging shell is provided with a slave node interaction port, one end of the slave node network data interaction cable is connected with the second output end of the clock synchronization and domestication unit, the third input end and the output end of the ranging and positioning unit and the input end of the slave node power supply unit through the slave node interaction port, and the other end is connected with the control end, the input end and the output end of the slave node autonomous navigation unit and the output end of the slave node external power unit respectively.

[0018] The connection between the master node interaction port and the master node network data interaction cable and the connection between the slave node interaction port and the slave node network data interaction cable adopt watertight plug connectors.

[0019] Further, the master node watertight packaging shell and the slave node watertight packaging shell adopt a two-eye optical window structure including two communication windows, and the two-eye optical window structure is perpendicular to the sailing direction, and the two communication windows are respectively used for receiving and transmitting optical signals.

[0020] The master node underwater wireless optical communication unit and the slave node underwater wireless optical communication unit adopt a large-area photoelectric detector and an array LED for data transmission and reception respectively.

[0021] Further, the master node positioning device further comprises a master node acoustic communication unit, the first input end of the master node acoustic communication unit is connected with the first output end of the time reference unit, the second input end is connected with the output end of the master node autonomous navigation unit, and the output end is connected with the input end of the time reference unit.

[0022] The slave node positioning device further comprises a slave node acoustic communication unit, the input end of the slave node acoustic communication unit is connected with the first output end of the clock synchronization and domestication unit, the first output end is connected with the input end of the clock synchronization and domestication unit, and the second output end is connected with the second input end of the ranging and positioning unit.

[0023] The application also provides an underwater cluster vehicle cooperative positioning method based on wireless optical communication, which adopts the underwater cluster vehicle cooperative positioning system based on wireless optical communication, and the difference lies in that the method comprises the following steps:

[0024] Step 1, the master node underwater wireless optical communication unit of the master node positioning device and the slave node underwater wireless optical communication unit of the N slave node positioning devices are used to establish wireless optical communication links between the master node underwater vehicle and the N slave node underwater vehicles respectively.

[0025] Step 2, the time reference unit of the master node positioning device, the clock synchronization and taming unit of the N slave node positioning devices respectively generate data packet messages including the master node local transmit-receive time and the slave node local transmit-receive time, and the master node underwater wireless optical communication unit and the slave node underwater wireless optical communication unit are used to transmit and receive the data packet messages through the wireless optical communication link, so that the slave node underwater wireless optical communication unit of the N slave node positioning devices respectively obtains the master node local transmit-receive time and the slave node local transmit-receive time of the slave node positioning device, and sends them to the corresponding clock synchronization and taming unit;

[0026] Step 3, the clock synchronization and taming unit of the N slave node positioning devices respectively obtains the time clock difference between the master node positioning device and the N slave node positioning devices according to the master node local transmit-receive time and the slave node local transmit-receive time of the slave node positioning device, and performs cooperative time service and taming according to the time clock difference;

[0027] Step 4, start ranging, according to the method of step 2, the slave node underwater wireless optical communication unit of the N slave node positioning devices respectively obtains the master node local transmit-receive time and the slave node local transmit-receive time of the slave node positioning device at the ranging time, and sends them to the corresponding ranging and positioning unit;

[0028] At the same time, the time reference unit of the master node positioning device generates a control clock for the master node autonomous navigation unit and sends it to the master node autonomous navigation unit, the master node autonomous navigation unit measures the real-time position of the master node, and then uses the master node underwater wireless optical communication unit to transmit it to the slave node underwater wireless optical communication unit of the N slave node positioning devices through the wireless optical communication link, and the slave node underwater wireless optical communication unit receives and sends the real-time position of the master node to the ranging and positioning unit;

[0029] The clock synchronization and taming unit of the N slave node positioning devices respectively generates a control clock for each slave node autonomous navigation unit and sends it to the corresponding slave node autonomous navigation unit, and the slave node autonomous navigation unit measures the slave node position and sends it to the ranging and positioning unit;

[0030] Step 5, repeat step 4 according to the preset ranging time interval until I times of ranging are completed, where I is an integer and I≥3;

[0031] Step 6, the ranging and positioning unit of the N slave node positioning devices respectively calculates the time delay of the master node positioning device and the N slave node positioning devices during I times of ranging according to the master node local transmit-receive time and the slave node local transmit-receive time obtained during each ranging, and then calculates the real-time position distance between the master node underwater vehicle and the N slave node underwater vehicles during I times of ranging according to the time delay;

[0032] Step 7, the ranging and positioning units of the N slave node positioning devices respectively calculate the change amount between the positions of the slave nodes when the two adjacent times of ranging of the corresponding slave node underwater vehicle, obtain I-1 slave node position change amounts, and then respectively solve the real-time positions of the N slave node underwater vehicles according to the real-time positions of the I master nodes, the I-1 slave node position change amounts, and the real-time position distances between the master node underwater vehicle and the slave node underwater vehicles, and send the real-time positions to the slave node autonomous navigation unit for position coordinate correction, so as to complete the cooperative positioning of the underwater vehicles.

[0033] Further, in step 6, the time delays of the master node positioning device and the N slave node positioning devices in the I times of ranging are respectively calculated by the following formula:

[0034]

[0035] wherein, is the time delay of the master node positioning device and the n th slave node positioning device in the i th time of ranging, n and i are integers, and 1≤n≤N, ; is the master node local sending time in the i th time of ranging, is the slave node local receiving time of the n th slave node positioning device in the i th time of ranging, is the slave node local sending time of the n th slave node positioning device in the i th time of ranging, is the master node local receiving time in the i th time of ranging;

[0036] In step 6, the real-time position distances between the master node underwater vehicle and the N slave node underwater vehicles in the I times of ranging are respectively calculated by the following formula:

[0037]

[0038] wherein, is the real-time position distance between the master node positioning device and the n th slave node positioning device in the i th time of ranging, is the transmission speed of light signal in water.

[0039] Further, in step 7, the real-time positions of the N slave node underwater vehicles are respectively solved by the following formula:

[0040]

[0041] wherein, , , are respectively the X, Y and Z axis coordinates of the real-time position of the n th slave node underwater vehicle, , , X, Y, Z axis coordinates of the master node real-time position at the i-th ranging, , , X, Y, Z axis variation between the n-th slave node underwater vehicle slave node positions obtained by the first and second ranging, , , X, Y, Z axis variation between the n-th slave node underwater vehicle slave node positions obtained by the second and third ranging, , , X, Y, Z axis variation between the n-th slave node underwater vehicle slave node positions obtained by the i-1-th and i-th ranging.

[0042] Further, step 2 is specifically:

[0043] Step 2.1, the time reference unit of the master node positioning device generates a reference clock signal, and measures the master node local sending time according to the reference clock signal, and then sends the master node local sending time as data packet message I to the master node underwater wireless optical communication unit, and the master node underwater wireless optical communication unit modulates the optical signal according to the data packet message I and sends it to the N slave node positioning devices through the wireless optical communication link respectively;

[0044] Step 2.2, the slave node underwater wireless optical communication unit of the N slave node positioning devices receives and demodulates the data packet message I respectively, and then sends the demodulated data packet message I to the clock synchronization and domestication unit; at the same time, the clock synchronization and domestication unit measures the slave node local receiving time;

[0045] Step 2.3, the clock synchronization and domestication unit of the N slave node positioning devices generates a clock signal, and measures the slave node local sending time according to the clock signal, and then sends the slave node local sending time and the slave node local receiving time as data packet message II to the slave node underwater wireless optical communication unit, and the slave node underwater wireless optical communication unit modulates the optical signal according to the data packet message II and sends it to the master node positioning device through the wireless optical communication link respectively;

[0046] Step 2.4, the master node underwater wireless optical communication unit of the master node positioning device receives and demodulates the data packet message II sent by the N slave node positioning devices respectively, and then sends the demodulated data packet message II to the time reference unit; at the same time, the time reference unit measures the master node local receiving time and sends it as data packet message III to the master node underwater wireless optical communication unit; the master node underwater wireless optical communication unit modulates the optical signal according to the data packet message III and sends it to the N slave node positioning devices through the wireless optical communication link respectively;

[0047] Step 2.5, the slave node underwater wireless optical communication unit of the N slave node positioning device respectively receives and demodulates the data packet message III, and then sends the demodulated data packet message III to the clock synchronization and taming unit.

[0048] Further, step 3 is specifically:

[0049] Step 3.1, the clock synchronization and taming unit of the N slave node positioning device respectively obtains the time clock difference of the master node positioning device and the N slave node positioning device according to the master node local sending time, the slave node local receiving time of the slave node positioning device and the following formula:

[0050]

[0051] Wherein, is the time clock difference of the master node positioning device and the n-th slave node positioning device, is the master node local sending time, is the slave node local receiving time of the n-th slave node positioning device, is the slave node local sending time of the n-th slave node positioning device, is the master node local receiving time;

[0052] Step 3.2, the clock synchronization and taming unit of the N slave node positioning device respectively time the crystal oscillator in it according to the time clock difference of the master node positioning device and the slave node positioning device, and complete the cooperative time service;

[0053] Step 3.3, the clock synchronization and taming unit of the N slave node positioning device respectively removes the outliers in the time clock difference of the master node positioning device and the slave node positioning device by using filtering and control algorithm, and then calculates the frequency deviation of the master node positioning device and the slave node positioning device, and converts it into an analog quantity and then performs high-frequency filtering to obtain a control voltage;

[0054] Step 3.4, the clock synchronization and taming unit of the N slave node positioning device respectively adjusts the output frequency of the crystal oscillator in it by using the control voltage, and completes the taming.

[0055] Compared with the prior art, the present application has the following beneficial effects:

[0056] 1, the underwater cluster vehicle cooperative positioning system based on wireless optical communication provided by the present application is based on underwater wireless optical communication technology, has high communication rate, low delay and large transmission capacity, and at the same time, the time reference unit of the master node positioning device is used to time synchronize and tame the crystal oscillator in the clock synchronization and taming unit of the slave node positioning device, so as to realize the cooperative time service of the N slave node underwater vehicles, and further ensure the positioning accuracy;

[0057] 2. The underwater cluster vehicle cooperative positioning system based on wireless optical communication provided by the present application can realize cooperative positioning of underwater cluster vehicles by using the autonomous navigation unit of the underwater vehicle itself, without external auxiliary positioning equipment, thereby avoiding the problem that data of the external auxiliary positioning equipment and data of the autonomous navigation unit of the underwater vehicle itself are difficult to fuse due to reference differences;

[0058] 3. The underwater cluster vehicle cooperative positioning system based on wireless optical communication provided by the present application only needs one master node underwater vehicle equipped with a high-precision autonomous navigation unit and a time reference unit, and can realize high-precision positioning of N slave node underwater vehicles, thereby avoiding the problem that the traditional "three-ball positioning" method needs multiple master node underwater vehicles equipped with high-precision devices to realize cooperative positioning of slave node underwater vehicles, and can greatly reduce the cost;

[0059] 4. The underwater cluster vehicle cooperative positioning system based on wireless optical communication provided by the present application only needs the slave node underwater wireless optical communication unit to receive optical signals of the master node underwater wireless optical communication unit, thereby avoiding the problem that the traditional "three-ball positioning" method needs the slave node underwater wireless optical communication unit to have a nearly full-angle divergence angle and a receiving field angle to receive optical signals of multiple master node underwater wireless optical communication units, and reducing the technical difficulty of engineering implementation;

[0060] 5. The underwater cluster vehicle cooperative positioning system based on wireless optical communication provided by the present application adopts a double-eye light window structure for the master node water-tight packaging shell and the slave node water-tight packaging shell, can fully suppress backscattering light, and improves ranging and positioning accuracy;

[0061] 6. The underwater cluster vehicle cooperative positioning system based on wireless optical communication provided by the present application further comprises an acoustic communication unit, can be extended to an acoustic-optical cooperative mode, uses acoustic signals to realize "long-distance, loosely coupled cooperation" of underwater vehicles, and uses optical signals to realize "short-distance, tightly coupled cooperation" of underwater cluster vehicles. BRIEF DESCRIPTION OF DRAWINGS

[0062] Figure 1 FIG. 1 is an application scenario schematic diagram of the underwater cluster vehicle cooperative positioning system based on wireless optical communication of the present application;

[0063] Figure 2 FIG. 3 is a structure schematic diagram of the master node positioning device in the underwater cluster vehicle cooperative positioning system based on wireless optical communication of the present application;

[0064] Figure 3 FIG. 5 is a schematic diagram of the master node water-tight packaging shell in the underwater cluster vehicle cooperative positioning system based on wireless optical communication of the present application;

[0065] Figure 4It is the installation schematic view of the master node positioning device in the first embodiment of the underwater cluster vehicle cooperative positioning system based on wireless optical communication of the present application.

[0066] Figure 5 It is the structural schematic view of the slave node positioning device in the first embodiment of the underwater cluster vehicle cooperative positioning system based on wireless optical communication of the present application.

[0067] Figure 6 It is the principle diagram of the ranging and positioning in steps 4-7 in the first embodiment of the underwater cluster vehicle cooperative positioning method based on wireless optical communication of the present application.

[0068] Figure 7 It is the structural schematic view of the second embodiment of the underwater cluster vehicle cooperative positioning system based on wireless optical communication of the present application.

[0069] The reference signs are explained as follows:

[0070] 01-master node underwater vehicle, 02-slave node underwater vehicle;

[0071] 1-master node positioning device, 2-time reference unit, 3-master node underwater wireless optical communication unit, 4-master node autonomous navigation unit; 5-slave node positioning device, 6-clock synchronization and taming unit, 7-slave node underwater wireless optical communication unit, 8-ranging and positioning unit, 9-slave node autonomous navigation unit; 10-buoyancy material. DETAILED DESCRIPTION

[0072] The underwater cluster vehicle cooperative positioning system and method based on wireless optical communication of the present application are further explained in detail in combination with the drawings and specific embodiments. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present application, and the purpose is not to limit the protection scope of the present application.

[0073] Embodiment one

[0074] An underwater cluster vehicle cooperative positioning system based on wireless optical communication comprises one master node positioning device 1 and N slave node positioning devices 5, and in this embodiment, N=4. As shown in the figure, Figure 1 the underwater cluster vehicle comprises one master node underwater vehicle 01 and four slave node underwater vehicles 02. The master node underwater vehicle 01 is provided with a master node autonomous navigation unit 4 for measuring the real-time position of the master node, and the four slave node underwater vehicles 02 are respectively provided with slave node autonomous navigation units 9 for measuring the position change of the slave nodes. The master node underwater vehicle 01 and the slave node underwater vehicles 02 are distinguished according to the accuracy of the autonomous navigation units equipped thereon, and the underwater vehicle with high-precision autonomous navigation unit is the master node underwater vehicle 01.

[0075] The master node positioning device 1 is arranged on the master node underwater vehicle 01, as shown, comprising a time reference unit 2 and a master node underwater wireless optical communication unit 3. The first output end of the time reference unit 2 is connected with the first input end of the master node underwater wireless optical communication unit 3, and the second output end is connected with the control end of the master node autonomous navigation unit 4, for measuring the time of local receiving and transmitting data, and generating the control clock of the master node autonomous navigation unit 4. The second input end of the master node underwater wireless optical communication unit 3 is connected with the output end of the master node autonomous navigation unit 4, and the output end is connected with the input end of the time reference unit 2. Figure 2

[0076] In this embodiment, the master node positioning device 1 further comprises a master node power supply unit, a master node watertight packaging shell and a master node network data interaction cable. The input end of the master node power supply unit is connected with the output end of the master node external power unit, and the output end is connected with the power supply end of the time reference unit 2 and the master node underwater wireless optical communication unit 3 respectively, and the master node power supply unit is used for realizing the conversion of the electric level signal. The time reference unit 2, the master node underwater wireless optical communication unit 3 and the master node power supply unit are all located inside the master node watertight packaging shell, and the master node watertight packaging shell is provided with a master node interaction port. One end of the master node network data interaction cable is connected with the second output end of the time reference unit 2, the second input end of the master node underwater wireless optical communication unit 3 and the input end of the master node power supply unit through the master node interaction port respectively, and the other end is connected with the control end and the output end of the master node autonomous navigation unit 4 and the output end of the master node external power unit respectively. The connection between the master node data interaction port and the master node network data interaction cable adopts a watertight plug connector. The master node watertight packaging shell, the master node network data interaction cable and the watertight plug connector are used for waterproofing of underwater work and transmission of network signal and power supply data. As shown, the master node watertight packaging shell is a cuboid structure, with an outer dimension of 250mm×210mm×120mm, and adopts a double-eye light window structure with two communication windows, which are respectively used for receiving and transmitting light signals, and the double-eye light window structure is perpendicular to the navigation direction of the master node underwater vehicle 01, so as to realize the "communication in motion, measurement in motion and calibration in motion" between the master node underwater vehicle 01 and the slave node underwater vehicle 02. Figure 3 Figure 4

[0077] 4 slave node positioning devices 5 are arranged on 4 slave node underwater vehicles 02 respectively, as shown. Figure 5 ​​​As shown, the master node positioning device 1 comprises a clock synchronization and taming unit 6, a slave node underwater wireless optical communication unit 7 and a ranging and positioning unit 8. The first output end of the clock synchronization and taming unit 6 is connected with the input end of the slave node underwater wireless optical communication unit 7 and the first input end of the ranging and positioning unit 8 respectively, the second output end is connected with the control end of the slave node autonomous navigation unit 9, for obtaining the time clock difference of the master node positioning device 1 and the slave node positioning device 5 and performing cooperative timing and taming, and generating the control clock of the slave node autonomous navigation unit 9, wherein the frequency and period of the crystal oscillator in the clock synchronization and taming unit 6 are mainly tamed. The first output end of the slave node underwater wireless optical communication unit 7 is connected with the input end of the clock synchronization and taming unit 6, and the second output end is connected with the second input end of the ranging and positioning unit 8. The third input end of the ranging and positioning unit 8 is connected with the output end of the slave node autonomous navigation unit 9, and the output end is connected with the input end of the slave node autonomous navigation unit 9. The ranging and positioning unit 8 is used for calculating the real-time position of the slave node underwater vehicle 02, and completing the cooperative positioning of the underwater vehicle. The ranging and positioning unit 8 can realize the "on-the-move measurement" of the distance between the master node unmanned vehicle 01 and the slave node unmanned vehicle 02, and realize the calibration of the slave node autonomous navigation unit 9 based on the real-time position of the slave node underwater vehicle 02.

[0078] In the embodiment, the slave node positioning device 5 further comprises a slave node power supply unit, a slave node watertight packaging shell and a slave node network data interaction cable. The input end of the slave node power supply unit is connected with the output end of the slave node external power unit, and the output end is connected with the power supply end of the clock synchronization and taming unit 6, the slave node underwater wireless optical communication unit 7 and the ranging and positioning unit 8 respectively, and the slave node power supply unit is used to realize the conversion of the electric level signal. The clock synchronization and taming unit 6, the slave node underwater wireless optical communication unit 7, the ranging and positioning unit 8 and the slave node power supply unit are all located inside the slave node watertight packaging shell, and the slave node watertight packaging shell is provided with a slave node interaction port. One end of the slave node network data interaction cable is connected with the second output end of the clock synchronization and taming unit 6, the third input end and output end of the ranging and positioning unit 8 and the input end of the slave node power supply unit through the slave node interaction port respectively, and the other end is connected with the control end, input end and output end of the slave node autonomous navigation unit 9 and the output end of the slave node external power unit respectively. The connection between the slave node data interaction port and the slave node network data interaction cable adopts a watertight plug connector. The slave node watertight packaging shell adopts a two-eye optical window structure including two communication windows, and the two-eye optical window structure is perpendicular to the navigation direction of the slave node unmanned vehicle 02, and the two communication windows are used for receiving and transmitting optical signals respectively. The slave node watertight packaging shell, the slave node network data interaction cable and the watertight plug connector are used for waterproofing for underwater work and transmission of network signals and power supply data. The structure of the slave node watertight packaging shell, the installation position and manner of the slave node positioning device 5 and the slave node autonomous navigation unit 9 are the same as those of the main node watertight packaging shell, the main node positioning device 1 and the main node autonomous navigation unit 4.

[0079] The main node underwater wireless optical communication unit 3 and the slave node underwater wireless optical communication unit 7 both adopt a large-area photodetector and an array LED for data transmission and reception. The array LED has a large divergence angle, and the large-area photodetector has high sensitivity, which can reduce the influence of ocean current on platform fluctuation, quickly and easily establish a communication link, and maintain and transmit data for a long time.

[0080] The main node autonomous navigation unit 4 and the slave node autonomous navigation unit 9 are both composed of an inertial measurement device, a Doppler log and a depth gauge, which can simplify the underwater positioning process to a certain extent and reduce the number of ranging. The main node autonomous navigation unit 4 is equipped with high-precision devices, the inertial measurement device is iXblue Phins C3, and the Doppler log is Nortek DVL500; the slave node autonomous navigation unit 9 is equipped with low-precision devices, the inertial measurement device is Apogee-D, and the Doppler log is Nortek DVL100.

[0081] The time reference unit 2 comprises a time reference crystal oscillator and a time measurement chip connected in sequence, the time reference crystal oscillator adopts an ultra-high performance temperature compensation crystal oscillator SiTime SiT5357, and the crystal oscillator in the clock synchronization and taming unit 6 adopts an inexpensive and low-precision EPSON FA-128. Since the transmission speed of the optical signal in water reaches 2.56*10 8 m / s, therefore the time measurement chip selects a TDC high-precision time measurement chip produced by the ACAM company in Germany, the time measurement precision of which can reach the order of picoseconds, and the high-precision measurement of the local ranging transmission and reception time is completed by using the same, and finally the underwater ranging precision can reach the order of centimeters.

[0082] The embodiment also provides a cooperative positioning method of underwater cluster vehicles based on wireless optical communication, which adopts the above-mentioned cooperative positioning system of underwater cluster vehicles based on wireless optical communication, and comprises the following steps.

[0083] Step 1, the master node underwater wireless optical communication units 3 and 4 of the master node positioning device 1 and the slave node underwater wireless optical communication units 7 of the four slave node positioning devices 5 are used to respectively establish wireless optical communication links between the master node underwater vehicle 01 and the four slave node underwater vehicles 02. Among them, the PTP (IEEE 1588) communication protocol is adopted between the master node positioning device 1 and the slave node positioning device 5.

[0084] Step 2, the time reference unit 2 of the master node positioning device 1 and the clock synchronization and taming unit 6 of the four slave node positioning devices 5 are used to respectively generate data packet messages including the master node local transmission and reception time and the slave node local transmission and reception time, and the master node underwater wireless optical communication unit 3 and the slave node underwater wireless optical communication unit 7 are used to transmit and receive the data packet messages through the wireless optical communication link, so that the slave node underwater wireless optical communication unit 7 of the four slave node positioning devices 5 respectively obtains the master node local transmission and reception time and the slave node local transmission and reception time of the slave node positioning device 5, and sends them to the corresponding clock synchronization and taming unit 6. Specifically,

[0085] Step 2.1, the time reference unit 2 of the master node positioning device 1 generates a reference clock signal, and measures the master node local transmission time according to the reference clock signal, and then sends the master node local transmission time as a data packet message I to the master node underwater wireless optical communication unit 3, and the master node underwater wireless optical communication unit 3 modulates the optical signal according to the data packet message I and sends it to the four slave node positioning devices 5 through the wireless optical communication link.

[0086] Step 2.2, the slave node underwater wireless optical communication unit 7 of the four slave node positioning devices 5 respectively receives and demodulates the data packet message I, and then sends the demodulated data packet message I to the clock synchronization and taming unit 6; at the same time, the clock synchronization and taming unit 6 measures the slave node local reception time;

[0087] Step 2.3, the clock synchronization and taming unit 6 of the 4 slave node positioning devices 5 generates a clock signal and measures the slave node local sending time according to the clock signal, and then sends the slave node local sending time and the slave node local receiving time as data packet message II to the slave node underwater wireless optical communication unit 7. The slave node underwater wireless optical communication unit 7 modulates the optical signal according to the data packet message II and sends it to the master node positioning device 1 through the wireless optical communication link respectively;

[0088] Step 2.4, the master node underwater wireless optical communication unit 3 of the master node positioning device 1 receives and demodulates the data packet message II sent by the 4 slave node positioning devices 5 respectively, and then sends the demodulated data packet message II to the time reference unit 2. At the same time, the time reference unit 2 records the master node local receiving time and sends it as data packet message III to the master node underwater wireless optical communication unit 3. The master node underwater wireless optical communication unit 3 modulates the optical signal according to the data packet message III and sends it to the 4 slave node positioning devices 5 through the wireless optical communication link respectively;

[0089] Step 2.5, the slave node underwater wireless optical communication unit 7 of the 4 slave node positioning devices 5 receives and demodulates the data packet message III respectively, and then sends the demodulated data packet message III to the clock synchronization and taming unit 6.

[0090] Step 3, the clock synchronization and taming unit 6 of the 4 slave node positioning devices 5 respectively obtains the time clock difference between the master node positioning device 1 and the 4 slave node positioning devices 5 according to the master node local sending and receiving time and the slave node local sending and receiving time of the slave node positioning device 5, and performs cooperative time service and taming according to the time clock difference. Specifically:

[0091] Step 3.1, the clock synchronization and taming unit 6 of the 4 slave node positioning devices 5 respectively obtains the time clock difference between the master node positioning device 1 and the 4 slave node positioning devices 5 according to the master node local sending and receiving time and the slave node local sending and receiving time of the slave node positioning device 5 through the following formula respectively:

[0092]

[0093] Wherein, is the time clock difference between the master node positioning device 1 and the nth slave node positioning device 5, n is an integer, and 1≤n≤4; is the master node local sending time, is the nth slave node local receiving time of the slave node positioning device 5, is the slave node local sending time of the nth slave node positioning device 5, is the master node local receiving time;

[0094] Step 3.2, the clock synchronization and taming unit 6 of the four slave node positioning devices 5 respectively time the crystal oscillator in them according to the time clock difference between the master node positioning device 1 and the slave node positioning device 5, and complete the cooperative time.

[0095] Step 3.3, the clock synchronization and taming unit 6 of the four slave node positioning devices 5 respectively remove the outliers in the time clock difference between the master node positioning device 1 and the slave node positioning device 5 by using filtering and control algorithm, then calculate the frequency deviation between the master node positioning device 1 and the slave node positioning device 5, and convert it into an analog quantity and then perform high-frequency filtering to obtain the control voltage.

[0096] Step 3.4, the clock synchronization and taming unit 6 of the four slave node positioning devices 5 respectively adjust the output frequency of the crystal oscillator in them by using the control voltage, and complete the taming.

[0097] Step 4, start ranging, according to the method of step 2, the slave node underwater wireless optical communication unit 7 of the four slave node positioning devices 5 respectively obtains the master node local transmission time and the slave node local transmission time of the slave node positioning device 5 at the ranging time, and sends them to the ranging and positioning unit 8.

[0098] At the same time, the time reference unit 2 of the master node positioning device 1 generates the control clock of the master node autonomous navigation unit 4 and sends it to the master node autonomous navigation unit 4, the master node autonomous navigation unit 4 measures the real-time position of the master node, and then uses the master node underwater wireless optical communication unit 3 to transmit it to the slave node underwater wireless optical communication unit 7 of the four slave node positioning devices 5 through the wireless optical communication link, and the slave node underwater wireless optical communication unit 7 receives and sends the real-time position of the master node to the ranging and positioning unit 8.

[0099] The clock synchronization and taming unit 6 of the four slave node positioning devices 5 respectively generates the control clock of the slave node autonomous navigation unit 9, and sends it to the corresponding slave node autonomous navigation unit 9, and the slave node autonomous navigation unit 9 measures the slave node position and sends it to the ranging and positioning unit 8.

[0100] Step 5, repeat step 4 according to the preset ranging time interval, until three ranging is completed. In this embodiment, the preset ranging time interval is 10s.

[0101] Step 6, the ranging and positioning unit 8 of the four slave node positioning devices 5 calculates the time delay of the master node positioning device 1 and the four slave node positioning devices 5 in the three ranging respectively according to the master node local sending time and the slave node local sending time of the slave node positioning device 5 obtained in each ranging, and then calculates the real-time position distance of the master node underwater vehicle 01 and the four slave node underwater vehicles 02 in the three ranging respectively. The time delay of the master node positioning device 1 and the four slave node positioning devices 5 in the three ranging is calculated by the following formula respectively:

[0102]

[0103] Wherein, is the time delay of the master node positioning device 1 and the nth slave node positioning device 5 in the ith ranging, i is the number of ranging, i = 1, 2, 3; is the master node local sending time in the ith ranging, is the slave node local receiving time of the nth slave node positioning device 5 in the ith ranging, is the slave node local sending time of the nth slave node positioning device 5 in the ith ranging, is the master node local receiving time in the ith ranging.

[0104] The real-time position distance of the master node underwater vehicle 01 and the four slave node underwater vehicles 02 in the three ranging is calculated by the following formula respectively:

[0105]

[0106] Wherein, is the real-time position distance of the master node positioning device 1 and the nth slave node positioning device 5 in the ith ranging, is the transmission speed of light signal in water.

[0107] Step 7, the ranging and positioning unit 8 of the four slave node positioning devices 5 calculates the change amount of the slave node position of the corresponding slave node underwater vehicle 02 in the adjacent two ranging respectively, obtains two slave node position change amounts, and then according to the three master node real-time positions, the two slave node position change amounts, and the real-time position distance of the master node underwater vehicle 01 and the slave node underwater vehicle 02, the real-time positions of the four slave node underwater vehicles 02 are calculated respectively, and sent to the slave node autonomous navigation unit 9 for position coordinate correction, and the cooperative positioning of the underwater vehicle is completed. The real-time positions of the four slave node underwater vehicles 02 are calculated by the following formula respectively:

[0108]

[0109] Wherein, , Xi, Yi, Zi are the X, Y, Z axis coordinates of the real-time position of the nth slave underwater vehicle 02 respectively, Xi, Yi, Zi are the X, Y, Z axis coordinates of the real-time position of the master node respectively, Xi, Yi, Zi are the X, Y, Z axis change amount between the slave node positions of the nth slave underwater vehicle 02 obtained by the first and second ranging respectively, Xi, Yi, Zi are the X, Y, Z axis change amount between the slave node positions of the nth slave underwater vehicle 02 obtained by the second and third ranging respectively.

[0110] As shown in Figure 6 , it is the principle diagram of completing ranging and positioning of steps 4-7. In the process of completing the cooperative positioning of the slave underwater vehicle 02 by the master underwater vehicle 01, the accuracy of the master node autonomous navigation unit 4 is high, so the real-time position of the master node measured is extremely accurate. Although the accuracy of the slave node autonomous navigation unit 9 is lower, the cumulative error of the position change amount in a short time is extremely small and can be ignored, so the slave node position change amount is also considered accurate. Based on the above steps, the master underwater vehicle 01 completes the high-precision cooperative positioning of the slave underwater vehicle 02, and the slave node autonomous navigation unit 9 continuously adjusts according to the obtained slave node real-time position information, and finally establishes a stable relative position relationship.

[0111] Example two

[0112] The difference between this embodiment and example one is that, as shown in Figure 7 , the master node positioning device 1 further comprises a master node acoustic communication unit, and the slave node positioning device 5 further comprises a slave node acoustic communication unit. The first input end of the master node acoustic communication unit is connected with the output end of the time reference unit 2, the second input end is connected with the output end of the master node autonomous navigation unit 4, and the output end is connected with the data input end of the time reference unit 2. The input end of the slave node acoustic communication unit is connected with the output end of the clock synchronization and taming unit 6, the first output end is connected with the input end of the clock synchronization and taming unit 6, and the second output end is connected with the second input end of the ranging and positioning unit 8. The master node acoustic communication unit, the slave node acoustic communication unit, the master node underwater wireless optical communication unit 3 and the slave node underwater wireless optical communication unit 7 adopt acoustic-optical cooperative mode, utilize acoustic signals to realize “long-distance, loose-coupling cooperation” of underwater vehicles, utilize optical signals to realize “short-distance, tight-coupling cooperation” of underwater vehicles, so as to realize high-precision time synchronization positioning of underwater vehicles in acoustic-optical cooperative mode.​​​​​​​

Claims

1. An underwater swarm vehicle cooperative positioning system based on wireless optical communication, the underwater swarm vehicle comprising one master node underwater vehicle (01) and N slave node underwater vehicles (02), wherein, N is an integer, and N≥2; the master node underwater vehicle (01) is provided with a master node autonomous navigation unit (4) for measuring the real-time position of the master node; N slave node underwater vehicles (02) are respectively provided with a slave node autonomous navigation unit (9) for measuring the position change of the slave node; characterized by comprising a master node positioning device (1) arranged on the master node underwater vehicle (01) and N slave node positioning devices (5) respectively arranged on the N slave node underwater vehicles (02); The master node positioning device (1) comprises a time reference unit (2) and a master node underwater wireless optical communication unit (3), the first output end of the time reference unit (2) is connected with the first input end of the master node underwater wireless optical communication unit (3), the second output end is connected with the control end of the master node autonomous navigation unit (4), for measuring the time of local receiving and sending data, and generating the control clock of the master node autonomous navigation unit (4); the second input end of the master node underwater wireless optical communication unit (3) is connected with the output end of the master node autonomous navigation unit (4), and the output end is connected with the input end of the time reference unit (2); The slave node positioning device (5) comprises a clock synchronization and domestication unit (6), a slave node underwater wireless optical communication unit (7) and a ranging and positioning unit (8); The first output end of the clock synchronization and domestication unit (6) is respectively connected with the input end of the slave node underwater wireless optical communication unit (7) and the first input end of the ranging and positioning unit (8), and the second output end is connected with the control end of the slave node autonomous navigation unit (9), for obtaining the time clock difference of the master node positioning device (1) and the slave node positioning device (5) and performing collaborative time service and domestication, and generating the control clock of the slave node autonomous navigation unit (9); The first output end of the slave node underwater wireless optical communication unit (7) is connected with the input end of the clock synchronization and domestication unit (6), and the second output end is connected with the second input end of the ranging and positioning unit (8); the third input end of the ranging and positioning unit (8) is connected with the output end of the slave node autonomous navigation unit (9), and the output end is connected with the input end of the slave node autonomous navigation unit (9), and the ranging and positioning unit (8) is used for calculating the real-time position of the slave node underwater vehicle (02) and completing the collaborative positioning of the underwater vehicle.

2. The wireless optical communication based underwater swarm vehicle cooperative positioning system according to claim 1, wherein: The master node positioning device (1) further comprises a master node power supply unit, the input end of the master node power supply unit is connected with the output end of the master node external power unit, and the output end is respectively connected with the power supply ends of the time reference unit (2) and the master node underwater wireless optical communication unit (3); The slave node positioning device (5) further comprises a slave node power supply unit; the input end of the slave node power supply unit is connected with the output end of the slave node external power unit, and the output end is respectively connected with the power supply ends of the clock synchronization and domestication unit (6), the slave node underwater wireless optical communication unit (7) and the ranging and positioning unit (8).

3. The wireless optical communication based underwater swarm vehicle cooperative positioning system of claim 2, wherein: The master node positioning device (1) further comprises a master node water-tight packaging shell and a master node network data interaction cable; The time reference unit (2), the main node underwater wireless optical communication unit (3) and the main node power supply unit are located in the main node watertight packaging shell, a main node interaction port is arranged on the main node watertight packaging shell, one end of the main node network data interaction cable is connected with the second output end of the time reference unit (2), the second input end of the main node underwater wireless optical communication unit (3) and the input end of the main node power supply unit through the main node interaction port, and the other end is connected with the control end and the output end of the main node autonomous navigation unit (4) and the output end of the main node external power unit respectively; The slave node positioning device (5) further comprises a slave node watertight packaging shell and a slave node network data interaction cable; The clock synchronization and domestication unit (6), the slave node underwater wireless optical communication unit (7), the ranging and positioning unit (8) and the slave node power supply unit are located in the slave node watertight packaging shell, a slave node interaction port is arranged on the slave node watertight packaging shell, one end of the slave node network data interaction cable is connected with the second output end of the clock synchronization and domestication unit (6), the third input end and the output end of the ranging and positioning unit (8) and the input end of the slave node power supply unit through the slave node interaction port, and the other end is connected with the control end, the input end and the output end of the slave node autonomous navigation unit (9) and the output end of the slave node external power unit respectively; The connection between the main node interaction port and the main node network data interaction cable and the connection between the slave node interaction port and the slave node network data interaction cable are both water-tight plug connectors.

4. The wireless optical communication based underwater swarm vehicle cooperative positioning system of claim 3, wherein: The main node watertight packaging shell and the slave node watertight packaging shell both adopt a two-eye optical window structure comprising two communication windows, and the two-eye optical window structure is perpendicular to the sailing direction, and the two communication windows are respectively used for receiving and transmitting optical signals; The main node underwater wireless optical communication unit (3) and the slave node underwater wireless optical communication unit (7) both adopt a large-area photoelectric detector and an array LED for data transmission and reception.

5. The underwater swarm of vehicles cooperative positioning system based on wireless optical communication according to any one of claims 1-4, characterized in that: The main node positioning device (1) further comprises a main node acoustic communication unit, the first input end of the main node acoustic communication unit is connected with the first output end of the time reference unit (2), the second input end is connected with the output end of the main node autonomous navigation unit (4), and the output end is connected with the input end of the time reference unit (2); The slave node positioning device (5) further comprises a slave node acoustic communication unit, the input end of the slave node acoustic communication unit is connected with the first output end of the clock synchronization and domestication unit (6), the first output end is connected with the input end of the clock synchronization and domestication unit (6), and the second output end is connected with the second input end of the ranging and positioning unit (8).

6. A method for cooperative positioning of underwater swarm vehicles based on wireless optical communication, using the system for cooperative positioning of underwater swarm vehicles based on wireless optical communication according to any one of claims 1-5, characterized in that, The method comprises the following steps: Step 1, the main node underwater wireless optical communication unit (3) of the main node positioning device (1) and the slave node underwater wireless optical communication unit (7) of the N slave node positioning devices (5) are used to establish wireless optical communication links between the main node underwater vehicle (01) and the N slave node underwater vehicles (02) respectively. Step 2, the time reference unit (2) of the master node positioning device (1), the clock synchronization and taming unit (6) of the N slave node positioning devices (5) respectively generate data packet messages including the master node local transmission and reception time and the slave node local transmission and reception time, and the master node underwater wireless optical communication unit (3) and the slave node underwater wireless optical communication unit (7) of the N slave node positioning devices (5) transmit and receive data packet messages through the wireless optical communication link, so that the slave node underwater wireless optical communication unit (7) of the N slave node positioning devices (5) respectively obtains the master node local transmission and reception time and the slave node local transmission and reception time of the slave node positioning device (5), and sends them to the corresponding clock synchronization and taming unit (6); Step 3, the clock synchronization and taming unit (6) of the N slave node positioning devices (5) respectively obtains the time clock difference between the master node positioning device (1) and the N slave node positioning devices (5) according to the master node local transmission and reception time and the slave node local transmission and reception time of the slave node positioning device (5), and performs cooperative time service and taming according to the time clock difference; Step 4, start ranging, according to the method of step 2, the slave node underwater wireless optical communication unit (7) of the N slave node positioning devices (5) respectively obtains the master node local transmission and reception time and the slave node local transmission and reception time of the slave node positioning device (5) at the ranging time, and sends them to the corresponding ranging and positioning unit (8); At the same time, the time reference unit (2) of the master node positioning device (1) generates a control clock for the master node autonomous navigation unit (4) and sends it to the master node autonomous navigation unit (4), the master node autonomous navigation unit (4) measures the real-time position of the master node, and then uses the master node underwater wireless optical communication unit (3) to transmit it to the slave node underwater wireless optical communication unit (7) of the N slave node positioning devices (5) through the wireless optical communication link, and the slave node underwater wireless optical communication unit (7) receives and sends the real-time position of the master node to the ranging and positioning unit (8); The clock synchronization and taming unit (6) of the N slave node positioning devices (5) respectively generates a control clock for each slave node autonomous navigation unit (9), and sends it to the corresponding slave node autonomous navigation unit (9), and the slave node autonomous navigation unit (9) measures the slave node position and sends it to the ranging and positioning unit (8); Step 5, according to the preset ranging time interval, repeat step 4 until I times of ranging are completed, where I is an integer and I≥3; Step 6, the ranging and positioning unit (8) of the N slave node positioning devices (5) respectively calculates the time delay of the master node positioning device (1) and the N slave node positioning devices (5) during I times of ranging according to the master node local transmission and reception time and the slave node local transmission and reception time of the slave node positioning device (5) obtained during each ranging, and then calculates the real-time position distance of the master node underwater vehicle (01) and the N slave node underwater vehicles (02) during I times of ranging according to the time delay. Step 7, the ranging and positioning unit (8) of the N slave node positioning device (5) respectively calculates the change amount between the positions of the corresponding slave node underwater vehicle (02) at the adjacent two times of ranging, obtains I-1 slave node position change amounts, and then respectively solves the real-time positions of the N slave node underwater vehicles (02) according to the I master node real-time positions, the I-1 slave node position change amounts, and the real-time position distances between the master node underwater vehicle (01) and the slave node underwater vehicle (02), and sends them to the slave node autonomous navigation unit (9) for position coordinate correction, thereby completing the cooperative positioning of the underwater vehicles.

7. The method of claim 6, wherein, In step 6, the time delays of the master node positioning device (1) and the N slave node positioning devices (5) at the I times of ranging are respectively calculated by the following formula: ； wherein, is the time delay of the master node positioning device (1) and the nth slave node positioning device (5) at the ith ranging, n, i are integers, and 1≤n≤N, ; is the master node local sending time at the ith ranging, is the slave node local receiving time of the nth slave node positioning device (5) at the ith ranging, is the slave node local sending time of the nth slave node positioning device (5) at the ith ranging, is the master node local receiving time at the ith ranging; In step 6, the real-time position distances between the master node underwater vehicle (01) and the N slave node underwater vehicles (02) at the I times of ranging are respectively calculated by the following formula: ； wherein, is the real-time distance between the master positioning device (1) and the n-th slave positioning device (5) at the i-th ranging, is the transmission speed of the optical signal in water.

8. The method of claim 7, wherein: In step 7, the real-time positions of the N slave node underwater vehicles (02) are respectively solved by the following formula: ； wherein, , , are the X, Y, Z axis coordinates of the real-time position of the nth slave underwater vehicle (02) respectively, , , are the X, Y, Z axis coordinates of the real-time position of the master node at the ith ranging respectively, , , are the X, Y, Z axis changes between the slave node positions of the nth slave underwater vehicle (02) obtained by the first and second ranging respectively, , , are the X, Y, Z axis changes between the slave node positions of the nth slave underwater vehicle (02) obtained by the second and third ranging respectively, , , are the X, Y, Z axis changes between the slave node positions of the nth slave underwater vehicle (02) obtained by the I-1th and Ith ranging respectively.

9. The method of claim 6-8, wherein, Step 2 is specifically: Step 2.1, the time reference unit (2) of the master node positioning device (1) generates a reference clock signal, measures the master node local sending time according to the reference clock signal, and then sends the master node local sending time as data packet message I to the master node underwater wireless optical communication unit (3). The master node underwater wireless optical communication unit (3) modulates the optical signal according to the data packet message I, and sends it to the N slave node positioning devices (5) through the wireless optical communication link. Step 2.2, the slave node underwater wireless optical communication unit (7) of the N slave node positioning devices (5) respectively receives and demodulates the data packet message I, and then sends the demodulated data packet message I to the clock synchronization and domestication unit (6). At the same time, the clock synchronization and domestication unit (6) measures the slave node local receiving time; Step 2.3, the clock synchronization and domestication unit (6) of the N slave node positioning devices (5) generates a clock signal, measures the slave node local sending time according to the clock signal, and then sends the slave node local sending time and the slave node local receiving time as data packet message II to the slave node underwater wireless optical communication unit (7). The slave node underwater wireless optical communication unit (7) modulates the optical signal according to the data packet message II, and sends it to the master node positioning device (1) through the wireless optical communication link. Step 2.4, the master node underwater wireless optical communication unit (3) of the master node positioning device (1) respectively receives and demodulates the data packet message II sent by the N slave node positioning devices (5), and then sends the demodulated data packet message II to the time reference unit (2). At the same time, the time reference unit (2) measures the master node local receiving time and sends it as data packet message III to the master node underwater wireless optical communication unit (3). The master node underwater wireless optical communication unit (3) modulates the optical signal according to the data packet message III, and sends it to the N slave node positioning devices (5) through the wireless optical communication link. Step 2.5, the slave node underwater wireless optical communication unit (7) of the slave node positioning device (5) receives and demodulates the data packet message III respectively, and then sends the demodulated data packet message III to the clock synchronization and taming unit (6).

10. The method of claim 9, wherein, Step 3 is specifically: Step 3.1, the clock synchronization and taming unit (6) of the slave node positioning device (5) respectively obtains the time clock difference of the master node positioning device (1) and the N slave node positioning devices (5) according to the master node local receiving and transmitting time, the slave node local receiving and transmitting time of the slave node positioning device (5) through the following formula: ； wherein, a time clock difference for the master node positioning device (1) and the n-th slave node positioning device (5), a master node local transmission time instant, a slave node local reception time instant for the n-th slave node positioning device (5), a slave node local transmission time instant for the n-th slave node positioning device (5), a master node local reception time instant; Step 3.2, the clock synchronization and taming unit (6) of the N slave node positioning devices (5) respectively time the crystal oscillator in it according to the time clock difference of the master node positioning device (1) and the slave node positioning device (5), and completes the cooperative timing; Step 3.3, the clock synchronization and taming unit (6) of the N slave node positioning devices (5) respectively removes the wild value in the time clock difference of the master node positioning device (1) and the slave node positioning device (5) by using filtering and control algorithm, then calculates the frequency deviation of the master node positioning device (1) and the slave node positioning device (5), and converts it into an analog quantity and then performs high-frequency filtering to obtain a control voltage; Step 3.4, the clock synchronization and taming unit (6) of the N slave node positioning devices (5) respectively adjusts the output frequency of the crystal oscillator in it by using the control voltage, and completes the taming.

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