Underwater acoustic network assisted UUV formation positioning navigation method

Abstract

The invention relates to an underwater acoustic network assisted UUV formation positioning and navigation method, which comprises the following steps: (1) underwater acoustic network assisted UUV formation navigation and positioning overall design: in a navigation and positioning period, a navigator UUV emits a positioning ping signal, each follower UUV receives the ping signal and emits a positioning echo signal in a delayed manner, and each follower UUV receives the echo signal; the navigator UUV receives echo signals responded by all the follower UUVs through the ultra-short baseline array to carry out response distance measurement and ultra-short baseline direction finding, the GPS position of the navigator UUV output by inertial navigation equipment is integrated, geometric calculation is carried out to obtain the GPS position of each follower UUV, the navigator UUV broadcasts the GPS of the follower UUV through the underwater acoustic communication network node, and UUV formation navigation positioning is achieved. According to the invention, navigation and positioning of a plurality of follower UUVs can be realized, data transmission service among the UUVs can be provided, and the method has the advantages of low cost-effectiveness ratio, flexible use, high navigation efficiency, realization of positioning and navigation of a plurality of UUVs in a migratable area, and good practical value.

Description

Technical Field:

[0001] The present invention belongs to the technical field of underwater acoustic positioning, and particularly relates to an underwater acoustic network-assisted UUV formation positioning and navigation method. Background Art:

[0002] With the increasing maturity of UUV technology and underwater acoustic communication network technology, the use of UUV formations for underwater collaborative networking for marine resource surveys and environmental observations has been widely applied. Underwater UUV networks have advantages such as mobility, collaboration, and diversity, while also facing many challenges such as weak communication connectivity, limited navigation, positioning, and synchronization capabilities, and difficult formation control. Underwater navigation and positioning technology provides technical support for UUVs to perform tasks and is also a key technology for UUV formations to complete collaborative networking operations in a wide underwater area in a specific formation. Currently, underwater UUV positioning is usually achieved by forming a water surface constellation with surface buoys using a GPS-like principle, or by forming a long baseline positioning system with multiple fixed underwater transponders on the seabed. Since the positions of the buoys and transponders are fixed, only positioning services in a fixed area can be provided, and underwater UUV positioning in migratable areas cannot be achieved. This method of relying on multiple floating and underwater buoys for positioning is complex for the deployment and maintenance of the buoys at sea and has the disadvantage of high cost-effectiveness. When there are a large number of underwater UUVs, due to the narrow bandwidth of the underwater acoustic channel and the slow propagation speed of sound waves, in order to avoid interference between positioning signals, UUVs can often only be positioned and navigated one by one, which also has the disadvantage of low navigation and positioning efficiency. In addition, using inertial navigation technology as the main body and combining new auxiliary navigation technologies such as acoustic positioning to achieve multi-system fusion positioning of individual UUVs is also the main method of UUV positioning and navigation currently. This method has high positioning accuracy, but it is only for single UUV positioning, and the inertial navigation system is expensive. If each UUV in the formation is equipped with an inertial navigation system, the cost-effectiveness of this positioning and navigation mode is also relatively high. Summary of the Invention:

[0003] The technical problem to be solved by the present invention is to provide an underwater acoustic network-assisted UUV formation positioning and navigation method. This method uses the leader UUV with an inertial navigation device as the position reference, adopts the ultra-short baseline positioning principle, combines a channel multiple access method of random delay - dynamic adjustment of time slots according to the formation, and a compatibility design of signals and information frames for underwater acoustic navigation, positioning, and networking communication, to achieve navigation and positioning of multiple follower UUVs, and at the same time can also provide data transmission services between UUVs. Since only the leader UUV is equipped with an inertial navigation device, this method has the advantage of low cost-effectiveness, is flexible to use, has high navigation efficiency, and can achieve navigation and positioning of multiple UUVs in migratable areas, with good practical value.

[0004] The technical solution of the present invention is to provide an underwater acoustic network-assisted UUV formation positioning and navigation method, including the following steps,

[0005] (1) Overall Design of Underwater Acoustic Network-Assisted UUV Formation Navigation and Positioning

[0006] Within a navigation and positioning cycle, the leader UUV transmits a positioning ping signal. Each follower UUV receives the ping signal and then transmits a positioning echo signal with a delay. The leader UUV uses an ultra-short baseline array to receive the echo signals replied by each follower UUV for ranging by answering and direction finding with the ultra-short baseline. Combining with its own GPS position output by the inertial navigation equipment, geometric calculations are performed to obtain the GPS positions of each follower UUV. The leader UUV broadcasts the GPS positions of the follower UUVs through the underwater acoustic communication network nodes to achieve navigation and positioning of the UUV formation.

[0007] (2) Design of Signal and Communication Coding Information Frame Structure for Compatibility between Underwater Acoustic Navigation and Positioning and Networking Communication

[0008] The signal structure for compatibility between underwater acoustic navigation and positioning and networking communication includes time-of-arrival / direction-of-arrival signals and communication coding signals. The former is used for ranging and direction finding with the ultra-short baseline, and the latter is used to carry position messages and data messages. The communication coding information frame includes ping frames, echo frames, position broadcast frames, and other network type frames other than the above information frames. The ping or echo information frame structure includes frame type, frame length, source address, destination address, and data message. The position broadcast frame includes the position messages of each follower UUV. The frame type is used to identify whether the frame belongs to a ping frame, an echo frame, a position broadcast frame, or other network type frames. The frame length is used to indicate the byte length of the frame. The data message is used to carry information such as transmission delay information, UUV control instructions, UUV status information, UUV detection / reconnaissance information, etc. Through the design of the signal and information frame structure for compatibility between underwater acoustic navigation and positioning and networking communication, the present invention can be used for networking communication between UUVs while assisting UUV formation navigation and positioning.

[0009] (3) Multiple Access Channel Method of Random Delay of Follower UUV Echo Signals - Transmitting in Time Slots Dynamically Adjusted According to UUV Positions

[0010] During the network initialization phase, after the follower UUV receives the positioning ping signal transmitted by the leader UUV, it transmits the echo signal in a random delay manner to avoid, to a certain extent, the collision interference generated when the echo signal reaches the leader UUV. If the echo signal collides, the leader UUV determines which follower UUVs' echo signals are interfered by judging the source address of the echo frame, and broadcasts the positioning ping signal to those follower UUVs again. After that, the leader UUV will only receive the echo signals transmitted by those UUVs with random delays. This process is repeated until the leader UUV receives the conflict-free echo signals responded by all follower UUVs. During the network operation phase, each follower UUV uses the position information broadcast by the leader UUV in the previous navigation and positioning cycle to calculate the distances between other follower UUVs and the leader UUV, and controls the transmission delay of its own responded echo signal based on the calculated distances, so that the echo signals do not generate collision interference when reaching the leader UUV.

[0011] The present invention uses the leader UUV with an inertial navigation device as the position reference, adopts the ultra-short baseline positioning principle, combines the channel multiple access method of random delay - dynamic adjustment of time slots according to the formation for transmission, and the compatibility design of underwater acoustic navigation and positioning and networking communication compatibility signals and information frames to achieve the navigation and positioning of multiple follower UUVs, and can also provide data transmission services between UUVs.

[0012] Preferably, the source address of the ping frame and the position broadcast frame is the address of the leader UUV, and the destination address is the address of the follower UUV, while the echo frame is vice versa.

[0013] Preferably, the random transmission delay τ of the i-th follower UUV i = uniform(0, NT), where N is the number of follower UUVs transmitting the echo signal, T is the time length of the echo signal. During the network initialization phase, it is stipulated that the echo signals of each follower UUV can only carry network information data with an equal number of bytes, and at this time T is a fixed constant; assuming d1 < d2 < … < d N , the transmission delay of the i-th follower UUV is

[0014]

[0015] where, T j is the time length of the echo signal responded by the j-th follower UUV, d i is the distance between the i-th follower UUV and the leader UUV, Δ t is the delay margin reserved for considering the change of the UUV formation within the positioning cycle, and Δ t is generally set as a fixed small value.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] The present invention proposes an underwater acoustic network-assisted UUV formation positioning and navigation method. Based on the principle of ultra-short baseline positioning, this method adopts a channel multiple access method of random delay - dynamically adjusting time slots for transmission according to the UUV position, as well as a compatibility design of underwater acoustic navigation positioning and networking communication signals and information frames, to achieve the navigation and positioning of the leader-follower UUV formation, and at the same time can also provide data transmission services between UUVs. Compared with the positioning and navigation system that relies on fixed buoys and submersibles, it has the following advantages: ① Only the leader UUV needs to be equipped with an inertial navigation device and an ultra-short baseline array, eliminating the complex problems of deploying and maintaining buoys and submersibles at sea; ② It can simultaneously achieve the navigation and positioning of UUV formations in migratable areas and networking communication, and has high navigation and positioning efficiency. The UUV formation navigation and positioning method of the present invention has a low cost-effectiveness ratio, is flexible to use, and has good practical value. Description of the drawings:

[0018] Figure 1 Schematic diagram of the navigation and positioning of the leader-follower UUV formation;

[0019] Figure 2 Block diagram of the underwater positioning process of the UUV formation;

[0020] Figure 3 Timing diagram of the positioning signal transmission;

[0021] Figure 4 Compatibility signal structure of underwater acoustic navigation positioning and networking communication and communication coding information frame structure. Detailed implementation manners:

[0022] The following further describes the present invention in detail with reference to the drawings:

[0023] Figure 1 The schematic diagram of the leader-follower UUV formation network navigation and positioning of the present invention is given. The underwater cooperative operation of the UUV formation has obvious advantages in terms of efficiency compared with a single UUV platform. Currently, it often forms a leader-follower UUV formation networking operation mode with a single high-performance UUV leading multiple low-cost small UUVs. The leader UUV acts as the main node, mainly responsible for the formation control and task management functions of the UUV formation, and can also be used as the data fusion center of the UUV formation. The follower UUVs act as slave nodes and perform tasks such as seabed topography measurement, mine detection, and underwater target detection in a certain formation. The leader-follower UUV formation network belongs to a star-shaped master-slave network in a migratable area. The long baseline positioning system based on buoys and submersibles can only navigate and position UUVs within a certain fixed area range, and has disadvantages such as low positioning and navigation efficiency and complex deployment and maintenance of buoys and submersibles.

[0024] The present invention proposes a method for underwater acoustic network-assisted navigation and positioning of UUV formations. This method only requires the leader UUV to be equipped with an inertial navigation device and an ultra-short baseline array. Using the ultra-short baseline positioning principle, combined with a multiple access channel access method with random delay - dynamically adjusting time slots for transmission according to the UUV position, and the compatibility design of underwater acoustic positioning signals and networking communication signals, it realizes the navigation and positioning of multiple follower UUVs, and can also provide data transmission services between UUVs.

[0025] To facilitate the description of the content of the present invention, the following takes a UUV formation composed of 1 leader UUV and 3 follower UUVs as an example to introduce the underwater navigation and positioning method of the UUV formation proposed by the present invention.

[0026] Figure 2 The block diagram of the underwater positioning and navigation process of the UUV formation in this embodiment is given. Figure 3 The timing diagram of underwater positioning signal transmission is given. In one navigation and positioning cycle, first, the leader UUV broadcasts and transmits a positioning ping signal through the underwater acoustic communication network node. After the underwater acoustic communication network nodes of the 3 follower UUVs receive the ping signal, they respond with echo signals according to the timing shown in Figure 3 . Each echo signal transmitted by each follower UUV carries the transmission delay information τ i , i = 1, 2, 3. Then, the leader UUV uses the echo signals transmitted by each follower UUV received by the ultra-short baseline array to complete response ranging and ultra-short baseline direction finding. The leader UUV then uses the ranging and direction finding results combined with the GPS position of itself given by the inertial navigation device to calculate the GPS positions of each follower UUV through geometric calculation. Finally, the leader UUV broadcasts the GSP position information of each follower UUV through the underwater acoustic communication network node to realize the navigation and positioning of the UUV formation. Figure 2 In addition to the signals for time measurement and direction finding, the positioning ping signal and the positioning echo signal in also include communication coding signals for carrying network information data. Therefore, in the process of underwater acoustic network-assisted UUV formation positioning, it can also be used for network data transmission between the leader UUV and the follower UUVs. Figure 3 In, t0 is the moment when the leader UUV transmits the positioning ping signal, and t1, t2, and t3 are the moments when the echo signals responded by the follower UUV1, UUV2, and UUV3 reach the leader UUV respectively. According to the principle of response ranging, the distance calculation is

[0027]

[0028] In the formula, c is the speed of sound, T0 is the time length of the ping signal transmitted by the leader UUV, and d1, d2, and d3 are the distances between the leader UUV and the follower UUV1, UUV2, and UUV3 respectively.

[0029] Figure 4 The compatibility signal and communication coding information frame structure for underwater acoustic navigation positioning and networking communication is given. The compatibility signal structure includes a time-of-arrival / direction-finding signal and a communication coding signal. The former can adopt a pseudo-random sequence binary code signal. By performing copy correlation processing on the binary code signal, the position moment corresponding to the correlation peak is taken to measure the signal arrival time. By performing conjugate operation on the complex baseband signal of the binary code received by the ultra-short baseline elements and taking the phase of the conjugate result, and integrating the spatial positions of the elements and the electronic compass data, the direction measurement of each follower UUV is realized through geometric calculation. Then, using the response ranging result, the position calculation of the follower UUV is completed. The communication coding signal is used to carry position messages and data messages.

[0030] The communication coding information frame includes a ping frame, an echo frame, a position broadcast frame, and other network type frames other than the above information frames. The ping or echo information frame structure includes a frame type, a frame length, a source address, a destination address, and a data message. The position broadcast frame also includes the position messages of each follower UUV. The frame type is used to identify whether the frame belongs to a ping frame, an echo frame, a position broadcast frame, or other network type frames. The frame length is used to indicate the byte length of the frame. The communication network nodes of the UUV can deduce the time length of the frame through the frame length information for determining the transmission delay. The source address of the ping frame and the position broadcast frame is the address of the leader UUV, and the destination address is the address of the follower UUV. The echo frame is vice versa. The data message is used to carry transmission delay information, UUV control instructions, UUV status information, UUV detection / reconnaissance information, etc. It can be seen that the compatibility signal and communication coding information frame structure designed by the present invention for underwater acoustic navigation positioning and networking communication can be used for networking communication between UUVs while assisting UUV formation navigation positioning, and has good flexibility and practicability.

[0031] To avoid the influence of the conflict interference of the positioning echo signal accessing the channel on the ranging and direction-finding accuracy of the leader UUV and improve the efficiency of positioning and navigation, the present invention provides two solutions in different stages of the network:

[0032] ① In the network initialization stage, the position information of other UUVs is unknown to each UUV. At this time, after the follower UUV receives the positioning ping signal emitted by the leader UUV, it emits an echo signal in a random delay manner, so as to avoid the conflict interference generated when the echo signal reaches the leader UUV to a certain extent. If the echo signal conflicts, the leader UUV judges which follower UUVs' echo signals are interfered by the source address of the echo frame, and broadcasts the positioning ping signal to those follower UUVs again. After that, the leader UUV will only receive the echo signals emitted by those UUVs with random delays. Repeat this process until the leader UUV receives all the echo signals replied by the follower UUVs without conflict interference. The delay time is

[0033] τ i = uniform(0,NT) (2)

[0034] where uniform(a, b) represents a random number uniformly distributed between a and b, N is the number of follower UUVs with conflict interference echo signals in a certain round of ping-echo transmission process, and T is the time length of the echo signal. In the network initialization stage, it is stipulated that the echo signals of each follower UUV can only carry network information data with an equal number of bytes. At this time, T is a fixed constant;

[0035] ② In the network operation stage, each follower UUV uses the position information broadcast by the leader UUV in the previous positioning cycle to calculate the distances between other follower UUVs and the leader UUV, and uses the calculated distances to control the transmission delay of its own replied echo signal, so that the echo signal does not generate conflict interference when it reaches the leader UUV. Figure 3 T1, T2, and T3 in are the time lengths of the echo signals replied by follower UUV1, UUV2, and UUV3 respectively. In this stage, the number of bytes of the network information data carried by the echo signals of each follower UUV can be of unequal length. Without loss of generality, assume d1 < d2 < d3, then the delays of each follower UUV in emitting the echo signal are

[0036]

[0037] where T1, T2, and T3 can be obtained by listening to the frame information of the echo signal by the underwater acoustic communication network node, and Δ t is the delay margin reserved considering the change of the UUV formation within the positioning cycle. Since the underwater movement speed of the UUV is much smaller than the speed of sound, Δ tGenerally set as a fixed small quantity, the impact of this small quantity on the positioning and navigation efficiency is negligible. Solution 1 realizes conflict interference avoidance through the channel access method of random delay transmission. Solution 2 utilizes the UUV position information obtained in the previous positioning and navigation process to control their respective transmission time slots, thereby avoiding conflict interference. The former may require multiple rounds of ping-echo transmission processes, while the latter only requires one time. The positioning and navigation efficiency of the latter is significantly better than that of the former. However, the former only needs to be executed once during initialization. Generally speaking, it can be shown that the method of the present invention has high positioning and navigation efficiency.

[0038] In summary, the present invention proposes an underwater acoustic network-assisted UUV formation positioning and navigation method. Based on the ultra-short baseline positioning principle, this method adopts a channel multiple access method of random delay - dynamically adjusting the delay transmission according to the UUV position, as well as a compatibility design of signals and information frames for underwater acoustic navigation positioning and networking communication, to achieve the navigation and positioning of the leader-follower UUV formation. Compared with the traditional fixed-layout floating and submerged buoy long baseline positioning and navigation system, the present invention does not have the problems of complex construction and maintenance of floating and submerged buoys at sea. It only requires the leader UUV to be equipped with an inertial navigation device and an ultra-short baseline array, and can simultaneously achieve the navigation and positioning of the UUV formation in the migratable area and networking communication, and has high navigation and positioning efficiency. Thus, it can be seen that the UUV formation navigation and positioning method of the present invention has a low cost-effectiveness ratio, is flexible to use, and has good practical value.

[0039] The above is only an illustration of the preferred embodiments of the present invention and should not be construed as a limitation of the claims. Any equivalent process transformation using the specification of the present invention is included in the patent protection scope of the present invention.

Claims

1. An underwater acoustic network-assisted UUV formation positioning and navigation method, characterized in that: including the following steps, Overall design of underwater acoustic network-assisted UUV formation navigation and positioning. During a navigation and positioning cycle, the leader UUV transmits a positioning ping signal. Each follower UUV receives the ping signal and delays the transmission of a positioning echo signal. The leader UUV uses an ultra-short baseline array to receive the echo signals replied by each follower UUV for ranging by answering and direction finding with the ultra-short baseline. Combining its own GPS position, geometric calculations are performed to obtain the GPS positions of each follower UUV. The leader UUV broadcasts the GPS positions of the follower UUVs through underwater acoustic communication network nodes to achieve navigation and positioning of the UUV formation; Design of the signal and communication coding information frame structure for the compatibility of underwater acoustic navigation and positioning and networking communication. The underwater acoustic navigation and positioning and networking communication compatibility signal structure includes a time measurement / direction finding signal and a communication coding signal. The time measurement / direction finding signal is used for ranging and direction finding with the ultra-short baseline, and the communication coding signal is used to carry position messages and data messages; The communication coding information frame includes a ping frame, an echo frame, a position broadcast frame, and other network type frames other than the above information frames. The ping or echo frame structure includes a frame type, a frame length, a source address, a destination address, and a data message. The position broadcast frame includes the position messages of each follower UUV. The frame type is used to identify whether the information frame belongs to a ping frame, an echo frame, a position broadcast frame, or other network type frames; the frame length is used to indicate the byte length of the frame, and the data message is used to carry transmission delay information, UUV control instructions, UUV status information, and UUV detection / reconnaissance information; Multiple access channel method for the random delay of the follower UUV echo signal - transmitting in time slots dynamically adjusted according to the UUV position. In the network initialization stage, after receiving the positioning ping signal transmitted by the leader UUV, the follower UUVs transmit echo signals in a random delay manner. If the echo signals conflict, the leader UUV determines which follower UUVs' echo signals are interfered with by the source address of the echo frame, and broadcasts the positioning ping signal again to the follower UUVs whose echo signals are interfered with. Thereafter, the leader UUV only receives the echo signals randomly delayed and transmitted by the aforementioned UUVs, and repeats this process until the leader UUV receives the non-conflicting and non-interfered echo signals replied by all follower UUVs; In the network operation stage, the follower UUVs use the position information broadcast by the leader UUV in the previous positioning cycle to calculate the distances between other follower UUVs and the leader UUV, and use the calculated distances to control the transmission delay of their own replied echo signals so that the echo signals do not conflict or interfere when reaching the leader UUV.

2. The underwater acoustic network-assisted UUV formation positioning and navigation method according to claim 1, characterized in that: The source address of the ping frame and the position broadcast frame is the address of the leader UUV, and the destination address is the address of the follower UUVs, while the echo frame is the opposite.

3. The underwater acoustic network-assisted UUV formation positioning and navigation method according to claim 1, characterized in that: The random transmission delay τ of the i-th follower UUV i = uniform(0, NT), where N is the number of follower UUVs transmitting echo signals, and T is the time length of the echo signal. During the network initialization phase, it is stipulated that the echo signals of each follower UUV can only carry network information data with an equal number of bytes. At this time, T is a fixed constant. Assume d1 < d2 < … < d N , and the transmission delay of the i-th follower UUV is Among them, T j is the time length of the echo signal responded by the j-th follower UUV, d i is the distance between the i-th follower UUV and the leader UUV, Δ t is the delay margin reserved considering the change of the UUV formation within the positioning period, Δ t is set to a fixed value.

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