An underwater navigation positioning method and system based on supercontinuum laser intensity correlation

Abstract

The application discloses an underwater navigation positioning method and system based on supercontinuum laser intensity correlation. The system comprises a master control system, a transmitting end underwater base station and a receiving end underwater load. The method is as follows: firstly, the master control system generates supercontinuum laser signals with pseudo-random code information, the signals are separated into optical signals of different wavelength channels by a light splitting module, and are respectively sent to the underwater base stations corresponding to the wavelength channels and are transmitted; then the underwater load receives optical signals from multiple base stations, identifies the signal source base station according to the wavelength identifier, and performs correlation operation with a locally copied pseudo-random code sequence to determine the signal arrival time TOA and calculate the pseudo-range; finally, the three-dimensional coordinates of the underwater load and the local clock error result are solved by combining the pseudo-range, the absolute position and the transmission delay of the underwater load and at least four base stations. The application realizes high-precision and strong robustness absolute positioning in the underwater environment, and enhances the reliability of long-time positioning and navigation of underwater robots.

Description

Technical Field

[0001] This invention relates to the field of underwater navigation and positioning technology, and in particular to an underwater navigation and positioning method and system based on supercontinuous laser intensity correlation. Background Technology

[0002] As core equipment in deep-sea technology, underwater robots play an irreplaceable role in marine resource exploration, marine environmental monitoring, and marine security. Underwater positioning and navigation, as a prerequisite for underwater robots to determine their own location and reach their target points, is a crucial component of underwater robots.

[0003] Traditional underwater robot navigation and positioning technologies primarily rely on a combination of acoustic positioning systems and inertial navigation systems. Global position information is acquired through acoustic positioning devices such as long baselines and ultra-short baselines, and local high-frequency navigation is achieved by combining these with inertial measurement units (IMUs). In practical applications, acoustic positioning systems suffer from excessive noise and low resolution, resulting in positioning accuracy that fails to meet the demands of underwater navigation. Inertial navigation systems, on the other hand, suffer from cumulative error, with positioning errors increasing exponentially over time, severely limiting the long-term autonomous operation capabilities of underwater robots. Current research has introduced auxiliary navigation methods such as visual odometry to enhance positioning reliability; however, the effectiveness of visual odometry is severely limited by the significant degradation of underwater image quality and interference from dynamic objects such as fish.

[0004] In underwater positioning scenarios involving multiple complex environmental factors, the aforementioned navigation and positioning technologies each have significant limitations. Achieving high accuracy, zero cumulative error, and strong interference resistance simultaneously through a single technology is difficult. However, supercontinuum laser intensity correlation (SLR) offers a novel technological approach for underwater positioning. Supercontinuum lasers can simultaneously cut multiple wavelength channels for information transmission, while intensity correlation methods can calculate distances based on light propagation time and possess excellent anti-interference capabilities. Therefore, to meet the demands for high-precision, error-free, and interference-resistant underwater positioning, further research is needed to develop positioning technologies based on supercontinuum laser intensity correlation to further improve the accuracy and robustness of underwater positioning and navigation. Summary of the Invention

[0005] The purpose of this invention is to provide an underwater navigation and positioning method and system based on supercontinuous laser intensity correlation, which has high positioning accuracy, strong robustness, and high reliability.

[0006] The technical solution to achieve the purpose of this invention is: an underwater navigation and positioning method based on supercontinuum laser intensity correlation, comprising the following steps:

[0007] Step 1: The underwater base station achieves time synchronization through a high-precision chip atomic clock. The main control system generates a pseudo-random code sequence and performs on-off keying modulation on the output of the supercontinuum laser source at the whole second to form a supercontinuum laser signal with pseudo-random code information.

[0008] Step 2: The modulated supercontinuum laser is separated into optical signals of different wavelength channels by a beam splitter module, and then sent to the underwater base station corresponding to the wavelength channel for transmission.

[0009] Step 3: The detector carried by the underwater vehicle receives optical signals from multiple underwater base stations and identifies the source base station of the signal based on the wavelength identifier;

[0010] Step 4: The underwater receiver performs photoelectric conversion on the received optical signal, performs correlation operation with the locally copied pseudo-random code sequence, uses the peak value of the correlation function to determine the signal arrival time TOA and calculates the pseudorange;

[0011] Step 5: Combining the pseudorange, absolute position, and transmission delay of the underwater vehicle with at least four underwater base stations, calculate the three-dimensional coordinates of the underwater vehicle and the local clock error results using a geometric positioning algorithm.

[0012] An underwater navigation and positioning system based on supercontinuum laser intensity correlation, the system being used to implement the underwater navigation and positioning method based on supercontinuum laser intensity correlation, includes a main control system, an underwater base station at the transmitting end, and an underwater receiver at the receiving end;

[0013] The main control system generates a pseudo-random code sequence and performs on-off keying modulation on the output of the supercontinuous laser source at whole-second intervals to form a supercontinuous laser signal with pseudo-random code information. The modulated supercontinuous laser is then separated into optical signals of different wavelength channels by a beam splitter and sent to the underwater base station that corresponds to the unique wavelength channel.

[0014] The transmitting underwater base station receives signals sent by the main control system, and each underwater base station transmits a modulated optical signal with its unique corresponding wavelength channel;

[0015] The receiving underwater vehicle identifies the source of the signal by the underwater base station through wavelength identification. It performs correlation operations on the received signals of each wavelength channel with the local pseudo-random code to determine the signal arrival time and calculate the pseudorange. Finally, combined with the location of the underwater base station, it uses a geometric positioning algorithm to calculate the three-dimensional coordinates and local clock error of the underwater vehicle.

[0016] A mobile terminal includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements the underwater navigation and positioning method based on supercontinuum laser intensity correlation.

[0017] A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps in the underwater navigation and positioning method based on supercontinuous laser intensity correlation.

[0018] A computer device includes a memory and a processor, the memory and the processor being communicatively connected to each other, the memory storing computer instructions, and the processor executing the computer instructions to perform the underwater navigation and positioning method based on supercontinuum laser intensity correlation.

[0019] A computer program product includes computer instructions for causing a computer to execute the underwater navigation and positioning method based on supercontinuum laser intensity correlation.

[0020] Compared with the prior art, the present invention has the following significant advantages: (1) It effectively utilizes the advantages of the pseudo-random code with good autocorrelation characteristics, calculates the pseudorange based on the signal arrival time and the signal full second synchronous transmission mechanism, and realizes high-precision and robust absolute positioning in the underwater environment through pseudorange positioning and timing equations; (2) It realizes multi-wavelength channel parallel modulation of supercontinuous laser and high-precision absolute position calculation in the underwater environment, which enhances the reliability of underwater robot positioning and navigation for a long time and improves the underwater robot's long-term autonomous working capability. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of an underwater navigation and positioning system based on supercontinuous laser intensity correlation according to the present invention.

[0022] Figure 2 This is a schematic diagram of the process of receiving and processing modulated optical signals in this invention.

[0023] Figure 3 This is a schematic diagram illustrating the principle of pseudorange measurement from the base station to the underwater vehicle in this invention.

[0024] Figure 4 This is a schematic diagram illustrating the principle of calculating the three-dimensional coordinates and local clock error of the underwater object in this invention. Detailed Implementation

[0025] This invention provides an underwater navigation and positioning method based on supercontinuum laser intensity correlation, characterized by comprising the following steps:

[0026] Step 1: The underwater base station achieves time synchronization through a high-precision chip atomic clock. The main control system generates a pseudo-random code sequence and performs on-off keying modulation on the output of the supercontinuum laser source at the whole second to form a supercontinuum laser signal with pseudo-random code information.

[0027] Step 2: The modulated supercontinuum laser is separated into optical signals of different wavelength channels by a beam splitter module, and then sent to the underwater base station corresponding to the wavelength channel for transmission.

[0028] Step 3: The detector carried by the underwater vehicle receives optical signals from multiple underwater base stations and identifies the source base station of the signal based on the wavelength identifier;

[0029] Step 4: The underwater receiver performs photoelectric conversion on the received optical signal, performs correlation operation with the locally copied pseudo-random code sequence, uses the peak value of the correlation function to determine the signal arrival time TOA and calculates the pseudorange;

[0030] Step 5: Combining the pseudorange, absolute position, and transmission delay of the underwater vehicle with at least four underwater base stations, calculate the three-dimensional coordinates of the underwater vehicle and the local clock error results using a geometric positioning algorithm.

[0031] As a specific example, the underwater base station described in step 1 achieves time synchronization through a high-precision chip atomic clock. The main control system generates a pseudo-random code sequence and performs on-off keying modulation on the output of the supercontinuum laser source at integer second intervals to form a supercontinuum laser signal with pseudo-random code information, as detailed below:

[0032] Step 1.1: The underwater base station synchronizes with UTC time using a high-precision chip atomic clock;

[0033] Step 1.2: Using Gold code as the pseudo-random code for modulation, the main control system generates a Gold sequence of a preset number of levels: first, an m-sequence is generated through a binary linear feedback shift register, and then... It consists of a series of registers, a shift pulse generator, and a modulo-2 adder. The value of the register... Based on the line connection relationship, it is represented as follows:

[0034]

[0035] In the formula, A value of 0 or 1 indicates the status of the feedback connection line. Indicate participation and feedback. The feedback is disconnected, thus the characteristic polynomial corresponding to the sequence is:

[0036]

[0037] When the characteristic polynomial is a primitive polynomial, it generates an m-sequence. Two m-sequences are generated when the characteristic polynomial is of the same order but different. and If the cross-correlation function values ​​are bounded and satisfy the following formula, then an optimal pair of m sequences is formed:

[0038]

[0039] In the formula, Let be the period length of the m-sequence. Let m be the series of the m-sequence. The length of the sequence translation;

[0040] Then, a pair of m-sequences with the same period and rate are selected and output as translational equivalent sequences. After modulo-2 addition, the output is a Gold sequence, which is transmitted through communication between the underwater base station and the underwater body.

[0041] Finally, the main control system performs on-off keying (OOK) modulation on the optical signal output of the supercontinuum laser source according to the generated Gold code sequence, starting from the whole second, for a duration of one code cycle. The main control system uses the on and off states of the supercontinuum laser source to represent binary data "1" and "0" respectively. When a bit "1" needs to be transmitted, the supercontinuum laser source emits an optical pulse; when a bit "0" needs to be transmitted, the supercontinuum laser source is turned off and does not emit an optical pulse.

[0042] As a specific example, step 2 involves separating the modulated supercontinuum laser into optical signals of different wavelength channels using a beam splitter module, and then sending each signal to an underwater base station corresponding to its unique wavelength channel for transmission, as detailed below:

[0043] The modulated supercontinuum laser is processed by spectral filtering technology to cut the spectrum of the supercontinuum laser signal and separate optical signals of multiple wavelength channels. Each underwater base station is assigned a unique wavelength channel to identify the base station. This mapping relationship will be transmitted through communication between the underwater base station and the underwater vehicle. Each underwater base station only emits an OOK modulated optical signal with a unique center wavelength.

[0044] As a specific example, in step 4, the underwater receiver performs photoelectric conversion on the received optical signal, performs correlation operations with the locally copied pseudo-random code sequence, uses the peak value of the correlation function to determine the signal arrival time TOA, and calculates the pseudorange, as follows:

[0045] Step 4.1: Calculate the signal arrival time:

[0046] The underwater device performs photoelectric conversion on the received optical signal to obtain a binary signal sequence carrying a pseudo-random code. By using pre-known pseudo-random code information, the pseudo-random code sequence is replicated using a local clock. The received signal is correlated with a locally copied pseudo-random code sequence, and the sequence lag time is selected as the code width of the pseudo-random code. If the value is a multiple of , then the normalized correlation function can be expressed in the following discrete form:

[0047]

[0048] In the formula, The number of chips in one pseudo-random code period. It is a local pseudo-random code sequence Shift to the right in time The sequence obtained after counting chips;

[0049] When the correlation function reaches its maximum peak value, the local pseudo-random code and the pseudo-random code carried in the received signal are aligned in time phase with an error time of no more than 1 code width. At this time, the local clock time corresponding to the peak value of the correlation function is read out to obtain the signal arrival time TOA.

[0050] Step 4.2: Calculate the pseudorange between the underwater vehicle and the underwater base station:

[0051] The main control system at UTC time The supercontinuum laser signal is modulated at integer intervals and transmitted to the underwater base station for transmission. The transmitted signal travels through the underwater base station in time. The received time is obtained by the photodetector of the underwater device. The received time is derived from relevant calculations. The time generated by the underwater device's clock is not synchronized with UTC time, and there is a transmission delay between the completion of the supercontinuum laser source modulation and the signal transmission. The amount by which the underwater receiver clock leads the UTC time during signal reception is recorded, i.e., the underwater receiver clock difference is... The actual geometric distance is The speed of light in water is The speed at which optical signals are transmitted to the underwater base station is Then the pseudo-distance Represented as:

[0052]

[0053] As a specific example, step 5 involves combining the pseudorange, absolute position, and transmission delay of the underwater vehicle with at least four underwater base stations, and using a geometric positioning algorithm to calculate the three-dimensional coordinates of the underwater vehicle and the local clock error results, as detailed below:

[0054] Step 5.1: Based on the absolute positions, pseudorange information, and transmission delays of at least four underwater base stations, calculate the three-dimensional coordinates and local clock bias of the underwater vehicle. The absolute positions and transmission delays of the underwater base stations are pre-transmitted through communication between the underwater base stations. Record the underwater base station... The position coordinates are The transmission delay is The pseudo distance to the water-based body is The unknown underwater body coordinates are The clock difference is The speed of light in water is The speed at which light is transmitted to the underwater base station is Then the following system of four nonlinear equations can be listed:

[0055]

[0056] Step 5.2: Solve the equations using Newton's iterative method to obtain the underwater body coordinates and clock difference, and calibrate the local clock, as follows:

[0057] First, prepare the initial estimated values ​​of the current position coordinates of the underwater vehicle. Compared with the initial estimate of clock difference For initial positioning, clock bias The initial estimate of the current position coordinates is set to 0, and the initial value is set to the known underwater launch point or 0; in the k-th Newton iteration, the nonlinear equation is... The linearized matrix equation is as follows:

[0058]

[0059] In the formula,

[0060]

[0061]

[0062] The solution obtained using the least squares method is:

[0063]

[0064] Update water download body coordinates and clock difference have to:

[0065]

[0066]

[0067] If the Newton iteration has converged to the required accuracy, the Newton iteration method terminates the loop calculation and uses the updated value calculated in this iteration as the current position of the underwater vehicle, while calibrating the local clock with the calculated clock difference; otherwise, the next Newton iteration calculation continues.

[0068] The present invention also provides an underwater navigation and positioning system based on supercontinuum laser intensity correlation. The system is used to implement the underwater navigation and positioning method based on supercontinuum laser intensity correlation, and includes a main control system, an underwater base station at the transmitting end, and an underwater receiver.

[0069] The main control system generates a pseudo-random code sequence and performs on-off keying modulation on the output of the supercontinuous laser source at whole-second intervals to form a supercontinuous laser signal with pseudo-random code information. The modulated supercontinuous laser is then separated into optical signals of different wavelength channels by a beam splitter and sent to the underwater base station that corresponds to the unique wavelength channel.

[0070] The transmitting underwater base station receives signals sent by the main control system, and each underwater base station transmits a modulated optical signal with its unique corresponding wavelength channel;

[0071] The receiving underwater vehicle identifies the source of the signal by the underwater base station through wavelength identification. It performs correlation operations on the received signals of each wavelength channel with the local pseudo-random code to determine the signal arrival time and calculate the pseudorange. Finally, combined with the location of the underwater base station, it uses a geometric positioning algorithm to calculate the three-dimensional coordinates and local clock error of the underwater vehicle.

[0072] The present invention also provides a mobile terminal, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the underwater navigation and positioning method based on supercontinuous laser intensity correlation.

[0073] The present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps in the underwater navigation and positioning method based on supercontinuous laser intensity correlation.

[0074] The present invention also provides a computer device, comprising: a memory and a processor, wherein the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the computer instructions to perform the underwater navigation and positioning method based on supercontinuous laser intensity correlation.

[0075] The present invention also provides a computer program product, including computer instructions for causing a computer to execute the underwater navigation and positioning method based on supercontinuous laser intensity correlation.

[0076] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0077] Example

[0078] like Figure 1 As shown, the present invention discloses an underwater navigation and positioning system based on supercontinuum laser intensity correlation, comprising a main control system, an underwater base station at the transmitting end, and an underwater receiver.

[0079] The main control system generates a pseudo-random code sequence and performs on-off keying modulation on the output of the supercontinuous laser source at whole-second intervals to form a supercontinuous laser signal with pseudo-random code information. The modulated supercontinuous laser is then separated into optical signals of different wavelength channels by a beam splitter and sent to the underwater base station that corresponds to the unique wavelength channel.

[0080] The transmitting underwater base station receives signals sent by the main control system, and each underwater base station transmits a modulated optical signal with its unique corresponding wavelength channel;

[0081] The receiving underwater vehicle identifies the source of the signal by the underwater base station through wavelength identification. It performs correlation operations on the received signals of each wavelength channel with the local pseudo-random code to determine the signal arrival time and calculate the pseudorange. Finally, combined with the location of the underwater base station, it uses a geometric positioning algorithm to calculate the three-dimensional coordinates and local clock error of the underwater vehicle.

[0082] like Figure 1 As shown, an underwater navigation and positioning method based on supercontinuum laser intensity correlation includes the following steps:

[0083] Step 1: The underwater base station achieves time synchronization through a high-precision atomic clock. The main control system generates a pseudo-random code sequence and performs on-off keying modulation on the output of the supercontinuum laser source at integer second intervals to form a supercontinuum laser signal with pseudo-random code information, as detailed below:

[0084] Step 1.1: The underwater base station achieves synchronization with UTC time through a high-precision chip atomic clock. In order to ensure that the optical signal is modulated at the whole second of UTC time, the main control system and the underwater base station use a high-precision chip atomic clock to achieve picosecond-level time synchronization with UTC time.

[0085] Step 1.2: Gold codes with good autocorrelation and cross-correlation properties are used as pseudo-random codes for modulation. A Gold sequence of a preset number of levels is generated by the main control system: first, an m-sequence is generated through a binary linear feedback shift register, and then... It consists of a series of registers, a shift pulse generator, and a modulo-2 adder. The value of the register... Based on the line connection relationship, it can be represented as:

[0086]

[0087] In the formula, A value of 0 or 1 indicates the status of the feedback connection line. Indicate participation and feedback. The feedback is disconnected, thus the characteristic polynomial corresponding to the sequence is:

[0088]

[0089] When the characteristic polynomial is a primitive polynomial, it can generate m-sequences. Two m-sequences can be generated by primitive polynomials of the same order but different from each other. and If the cross-correlation function values ​​are bounded and satisfy the following formula, then an optimal pair of m sequences is formed:

[0090]

[0091] In the formula, Let be the period length of the m-sequence. Let m be the series of the m-sequence. The length of the sequence translation;

[0092] Then, a pair of m-sequences with the same period and rate are selected to output the equivalent translation sequence, which is then output as a Gold sequence after modulo 2 addition. This sequence is transmitted through communication between the base station and the underwater vehicle. The sequence with a longer period has better autocorrelation and cross-correlation characteristics, but it also increases the computational overhead when performing correlation operations. The appropriate Gold sequence of the appropriate level is selected according to the equipment performance.

[0093] Finally, the main control system performs on-off keying (OOK) modulation on the optical signal output of the supercontinuum laser source according to the generated Gold code sequence, starting from the whole second, for a duration of one code cycle. The main control system uses the on and off states of the supercontinuum laser source to represent binary data "1" and "0" respectively. When a bit "1" needs to be transmitted, the supercontinuum laser source emits an optical pulse; when a bit "0" needs to be transmitted, the supercontinuum laser source is turned off and does not emit an optical pulse.

[0094] Step 2: The modulated supercontinuum laser is separated into optical signals of different wavelength channels by a beam splitter module, and then sent to the underwater base station corresponding to each wavelength channel for transmission, as follows:

[0095] The modulated supercontinuum laser is processed by spectral filtering technology to cut the spectrum of the supercontinuum laser signal and separate optical signals of multiple wavelength channels. Each base station is assigned a unique wavelength channel to identify the base station. This mapping relationship will be transmitted through communication between the base station and the underwater vehicle. Each base station only emits an OOK modulated optical signal with a unique center wavelength.

[0096] Step 3: The photodetector carried by the underwater vehicle has high sensitivity and can receive optical signals from multiple base stations in separate wavelength channels. The underwater vehicle identifies the source base station of the signal according to the pre-obtained wavelength-base station correspondence and processes the signal in parallel according to different wavelength channels.

[0097] Step 4: The underwater receiver performs photoelectric conversion on the received optical signal, performs correlation calculation with the locally copied pseudo-random code sequence, uses the peak value of the correlation function to determine the signal arrival time TOA, and calculates the pseudorange. Figure 2As shown, the details are as follows:

[0098] Step 4.1: Calculate the signal arrival time:

[0099] The photodetector on the underwater vehicle performs photoelectric conversion on the received optical signal to obtain a binary signal sequence carrying a pseudo-random code. Using pre-known pseudo-random code information, a pseudo-random code sequence is copied using a local clock. The received signal is correlated with a locally copied pseudo-random code sequence, where the normalized correlation function is used. It can be defined as:

[0100]

[0101] In the formula, The number of chips in one pseudo-random code period. The duration of a single code chip, i.e., the code width. Let be the sequence lag time. To reduce computational load, select . The codewidth of the pseudo-random code If the value is a multiple of , then the normalized correlation function can be expressed in the following discrete form:

[0102]

[0103] In the formula, It is a local pseudo-random code sequence Shift to the right in time (lagging) The sequence obtained after counting chips;

[0104] Related functions It can check locally copied pseudo-random code sequences With the received signal sequence The similarity between them is determined when the correlation function reaches its maximum peak value. The local pseudo-random code and the pseudo-random code carried in the received signal are aligned in time phase with an error time of no more than 1 code width. At this time, the local clock time corresponding to the peak value of the correlation function is read out to obtain the signal arrival time TOA.

[0105] Step 4.2: Calculate the pseudorange between the underwater vehicle and the base station:

[0106] like Figure 3 As shown, the main control system is in UTC time Modulating supercontinuum laser signals at integer second intervals and transmitting them to the base station The signal was launched, and its transmission time was within the underwater range. The receiving time is obtained by the optical detector of the underwater device, and this receiving time is derived from related calculations. The time generated by the underwater device's clock is usually not synchronized with UTC time. The amount by which the underwater device's clock leads UTC time during signal reception is recorded, i.e., the underwater device clock difference. The corresponding actual UTC time is Then we have:

[0107]

[0108] The speed of light in water is The pseudo-distance from the water body to the base station for:

[0109]

[0110] The actual propagation time required for an optical signal to travel from a supercontinuum laser source to an underwater object is ,Right now:

[0111]

[0112] Considering the transmission delay between the completion of supercontinuum laser source modulation and signal transmission Let the actual geometric distance be . The speed at which the optical signal is transmitted to the base station is Combining the underwater download time with the clock difference of the base station, the pseudorange It can be represented as:

[0113]

[0114] Step 5: Combining the pseudorange, absolute position, and transmission delay of the underwater vehicle with at least four base stations, calculate the three-dimensional coordinates of the underwater vehicle and the local clock error results using a geometric positioning algorithm, such as... Figure 4 As shown, the details are as follows:

[0115] Step 5.1: Based on the absolute positions, pseudorange information, and transmission delays of at least four base stations, calculate the three-dimensional coordinates and local clock difference of the underwater body. The absolute positions and transmission delays of the base stations are pre-transmitted through communication between the base stations and the underwater base stations. Record the base station... The position coordinates are Its transmission delay is The pseudo distance to the water-based body is The unknown underwater body coordinates are The clock difference is The speed of light in water is The speed at which light is transmitted to the base station is Then the following system of four nonlinear equations can be listed:

[0116]

[0117] Step 5.2: Solve the equations using Newton's iterative method to obtain the underwater body coordinates and clock difference, and calibrate the local clock, as follows:

[0118] First, prepare the initial estimated values ​​of the current position coordinates of the underwater vehicle. Compared with the initial estimate of clock difference For initial positioning, clock bias The initial estimate of the current position coordinates can be set to 0, or it can be set to the known starting point of the underwater vehicle deployment or 0; in the k-th Newton iteration, the nonlinear equation is... The linearized matrix equation is as follows:

[0119]

[0120] In the formula,

[0121]

[0122]

[0123] The solution obtained using the least squares method is:

[0124]

[0125] Update water download body coordinates and clock difference have to:

[0126]

[0127]

[0128] If Newton's iteration has converged to the required accuracy, the loop calculation can be terminated, and the updated value calculated in the current iteration can be used as the current position of the underwater vehicle. At the same time, the local clock can be calibrated with the calculated clock difference; otherwise, the next Newton iteration calculation can be performed.

[0129] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An underwater navigation and positioning method based on supercontinuum laser intensity correlation, characterized in that, Includes the following steps: Step 1: The underwater base station achieves time synchronization through a high-precision atomic clock. The main control system generates a pseudo-random code sequence and performs on-off keying modulation on the output of the supercontinuum laser source at integer second intervals to form a supercontinuum laser signal with pseudo-random code information, as detailed below: Step 1.1: The underwater base station synchronizes with UTC time using a high-precision chip atomic clock; Step 1.2: Using Gold code as the pseudo-random code for modulation, the main control system generates a Gold sequence of a preset number of levels: first, an m-sequence is generated through a binary linear feedback shift register, and then... It consists of a series of registers, a shift pulse generator, and a modulo-2 adder. The value of the register... Based on the line connection relationship, it is represented as follows: ； In the formula, A value of 0 or 1 indicates the status of the feedback connection line. Indicate participation and feedback. The feedback is disconnected, thus the characteristic polynomial corresponding to the sequence is: ； When the characteristic polynomial is a primitive polynomial, it generates an m-sequence. Two m-sequences are generated when the characteristic polynomial is of the same order but different. and If the cross-correlation function values ​​are bounded and satisfy the following formula, then an optimal pair of m sequences is formed: ； In the formula, Let be the period length of the m-sequence. Let m be the series of the m-sequence. The length of the sequence translation; Then, a pair of m-sequences with the same period and rate are selected and output as equivalent translation sequences. After modulo-2 addition, the output is a Gold sequence, which is transmitted through communication between the underwater base station and the underwater body. Finally, the main control system performs on-off keying (OOK) modulation on the optical signal output of the supercontinuum laser source according to the generated Gold code sequence, starting from the whole second, for a duration of one code cycle. The main control system uses the supercontinuum laser source to represent binary data "1" and "0" respectively by turning it on and off. When a bit "1" needs to be transmitted, the supercontinuum laser source emits a light pulse; when a bit "0" needs to be transmitted, the supercontinuum laser source is turned off and does not emit a light pulse. Step 2: The modulated supercontinuum laser is separated into optical signals of different wavelength channels by a beam splitter module, and then sent to the underwater base station corresponding to the wavelength channel for transmission. Step 3: The detector carried by the underwater vehicle receives optical signals from multiple underwater base stations and identifies the source base station of the signal based on the wavelength identifier; Step 4: The underwater receiver performs photoelectric conversion on the received optical signal, performs correlation operation with the locally copied pseudo-random code sequence, uses the peak value of the correlation function to determine the signal arrival time TOA and calculates the pseudorange; Step 5: Combining the pseudorange, absolute position, and transmission delay of the underwater vehicle with at least four underwater base stations, calculate the three-dimensional coordinates of the underwater vehicle and the local clock error results using a geometric positioning algorithm.

2. The underwater navigation and positioning method based on supercontinuum laser intensity correlation according to claim 1, characterized in that, Step 2 involves separating the modulated supercontinuum laser into optical signals of different wavelength channels using a beam splitter module, and then sending each signal to the underwater base station corresponding to its unique wavelength channel for transmission. The specific steps are as follows: The modulated supercontinuum laser is processed by spectral filtering technology to cut the spectrum of the supercontinuum laser signal and separate optical signals of multiple wavelength channels. Each underwater base station is assigned a unique wavelength channel to identify the base station. This mapping relationship will be transmitted through communication between the underwater base station and the underwater vehicle. Each underwater base station only emits an OOK modulated optical signal with a unique center wavelength.

3. The underwater navigation and positioning method based on supercontinuum laser intensity correlation according to claim 1, characterized in that, In step 4, the underwater receiver performs photoelectric conversion on the received optical signal, performs correlation calculation with the locally copied pseudo-random code sequence, uses the peak value of the correlation function to determine the signal arrival time TOA, and calculates the pseudorange, as detailed below: Step 4.1: Calculate the signal arrival time: The underwater device performs photoelectric conversion on the received optical signal to obtain a binary signal sequence carrying a pseudo-random code. By using pre-known pseudo-random code information, the pseudo-random code sequence is replicated using a local clock. The received signal is correlated with a locally copied pseudo-random code sequence, and the sequence lag time is selected as the code width of the pseudo-random code. If the value is a multiple of , then the normalized correlation function can be expressed in the following discrete form: ； In the formula, The number of chips in one pseudo-random code period. It is a local pseudo-random code sequence Shift to the right in time The sequence obtained after counting chips; When the correlation function reaches its maximum peak value, the local pseudo-random code and the pseudo-random code carried in the received signal are aligned in time phase with an error time of no more than 1 code width. At this time, the local clock time corresponding to the peak value of the correlation function is read out to obtain the signal arrival time TOA. Step 4.2: Calculate the pseudorange between the underwater vehicle and the underwater base station: The main control system at UTC time The supercontinuum laser signal is modulated at integer intervals and transmitted to the underwater base station for transmission. The transmitted signal travels through the underwater base station in time. The received time is obtained by the photodetector of the underwater device. The received time is derived from relevant calculations. The time generated by the underwater device's clock is not synchronized with UTC time, and there is a transmission delay between the completion of the supercontinuum laser source modulation and the signal transmission. The amount by which the underwater receiver clock leads the UTC time during signal reception is recorded, i.e., the underwater receiver clock difference is... The actual geometric distance is The speed of light in water is The speed at which optical signals are transmitted to the underwater base station is Then pseudo-distance Represented as: 。 4. The underwater navigation and positioning method based on supercontinuum laser intensity correlation according to claim 3, characterized in that, Step 5 involves combining the pseudorange, absolute position, and transmission delay of the underwater vehicle with at least four underwater base stations, and then using a geometric positioning algorithm to calculate the three-dimensional coordinates of the underwater vehicle and the local clock error results, as detailed below: Step 5.1: Based on the absolute positions, pseudorange information, and transmission delays of at least four underwater base stations, calculate the three-dimensional coordinates and local clock bias of the underwater vehicle. The absolute positions and transmission delays of the underwater base stations are pre-transmitted through communication between the underwater base stations. Record the underwater base station... The position coordinates are The transmission delay is The pseudo distance to the water-based body is The unknown underwater body coordinates are The clock difference is The speed of light in water is The speed at which light is transmitted to the underwater base station is Then the following system of four nonlinear equations can be listed: ； Step 5.2: Solve the equations using Newton's iterative method to obtain the underwater body coordinates and clock difference, and calibrate the local clock, as follows: First, prepare the initial estimated values ​​of the current position coordinates of the underwater vehicle. Compared with the initial estimate of clock difference ; For initial positioning, clock difference The initial estimate of the current position coordinates is set to 0, and the known starting point for the underwater vehicle deployment is 0; in the k-th Newton iteration, the nonlinear equation is... The linearized matrix equation is as follows: ； In the formula, ； ； The solution obtained using the least squares method is: ； Update water download body coordinates and clock difference have to: ； ； If the Newton iteration has converged to the required accuracy, the Newton iteration method terminates the loop calculation and uses the updated value calculated in this iteration as the current position of the underwater vehicle, while calibrating the local clock with the calculated clock difference; otherwise, the next Newton iteration calculation continues.

5. An underwater navigation and positioning system based on supercontinuum laser intensity correlation, characterized in that, The system is used to implement the underwater navigation and positioning method based on supercontinuous laser intensity correlation as described in any one of claims 1 to 4, and includes a main control system, an underwater base station at the transmitting end, and an underwater receiver. The main control system generates a pseudo-random code sequence and performs on-off keying modulation on the output of the supercontinuous laser source at whole-second intervals to form a supercontinuous laser signal with pseudo-random code information. The modulated supercontinuous laser is then separated into optical signals of different wavelength channels by a beam splitter and sent to the underwater base station that corresponds to the unique wavelength channel. The transmitting underwater base station receives signals sent by the main control system, and each underwater base station transmits a modulated optical signal with its unique corresponding wavelength channel; The receiving underwater vehicle identifies the source of the signal by the underwater base station through wavelength identification. It performs correlation operations on the received signals of each wavelength channel with the local pseudo-random code to determine the signal arrival time and calculate the pseudorange. Finally, combined with the location of the underwater base station, it uses a geometric positioning algorithm to calculate the three-dimensional coordinates and local clock error of the underwater vehicle.

6. A mobile terminal, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the underwater navigation and positioning method based on supercontinuous laser intensity correlation as described in any one of claims 1 to 4.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the steps in the underwater navigation and positioning method based on supercontinuous laser intensity correlation as described in any one of claims 1 to 4.

8. A computer device, characterized in that, include: The system includes a memory and a processor, which are interconnected. The memory stores computer instructions, and the processor executes the computer instructions to perform the underwater navigation and positioning method based on supercontinuous laser intensity correlation as described in any one of claims 1 to 4.

9. A computer program product, characterized in that, Includes computer instructions, which are used to cause a computer to execute the underwater navigation and positioning method based on supercontinuous laser intensity correlation as described in any one of claims 1 to 4.

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