Underwater distance measurement positioning method

Abstract

The invention discloses an underwater ranging and positioning method. The method comprises the following steps: calibrating an acoustic sensor and an optical sensor; installing the calibrated acoustic sensor and the calibrated optical sensor at different parts of a carrier; judging the water quality condition according to the water quality judgment index, and dynamically adjusting the use weights of the optical sensor and the acoustic sensor according to the water quality judgment result; performing weighted fusion calculation on the adjusted weight and the target ranging data, optimizing a weighted fusion calculation result, and performing weighted fusion calculation again according to an optimization result to obtain a final ranging distance; carriers are arranged in different directions of a target, the carriers in all directions are subjected to weighted fusion through a fusion algorithm to calculate the final distance measurement distance from each carrier to the target, and the underwater position of the target is calculated in combination with a positioning algorithm, so that the method has the advantages of high distance measurement positioning precision and high reliability under different water quality conditions; the problem that in the prior art, the requirement for high-precision and high-reliability distance measurement positioning in a complex underwater environment is difficult to meet is effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of underwater target positioning, and in particular to an underwater ranging and positioning method. Background Art

[0002] Accurate ranging and positioning are crucial in many fields, including underwater operations, ocean exploration, and underwater robot navigation. However, the underwater environment is complex and changeable, and water quality conditions have a significant impact on ranging technology. In areas with clear water, optical ranging has high accuracy and resolution, but when the water is turbid, the propagation of light is severely disturbed and the ranging performance is greatly reduced. In contrast, acoustic ranging is less affected by water turbidity and can operate in relatively poor water quality, but there is a certain gap in accuracy and resolution compared to optical ranging. Traditional single ranging methods are difficult to meet the needs of high-precision and high-reliability ranging and positioning in complex underwater environments. Therefore, it is of great practical significance to develop an efficient underwater ranging and positioning method that can adapt to different water quality conditions.

[0003] The solution proposed by the present invention is to install calibrated acoustic sensors and optical sensors on different parts of the carrier, use the water quality judgment unit in the optical sensor to judge the water quality according to the water transparency threshold, dynamically adjust the usage weights of the acoustic sensor and the optical sensor according to the water quality judgment result, use the acoustic sensor and the optical sensor to simultaneously collect the ranging data of the target, and use a fusion algorithm to perform weighted fusion calculation on the adjusted weights and the ranging data, optimize the weighted fusion calculation result, and perform weighted fusion calculation again based on the optimization result to obtain the final ranging result, arrange carriers for different orientations of the target, perform weighted fusion calculation on the carriers in each orientation through the fusion algorithm to obtain the final ranging distance from each carrier to the target, and calculate the target's underwater position in combination with the positioning algorithm. The present invention has the advantages of high ranging and positioning accuracy and high reliability under different water quality conditions. Summary of the Invention

[0004] In order to solve the above-mentioned technical problems, the present invention provides an underwater ranging and positioning method.

[0005] The technical solution of the present invention is achieved as follows: an underwater ranging and positioning method, comprising:

[0006] S1. Calibrate the acoustic and optical sensors to be installed;

[0007] S2. Install the acoustic sensor and optical sensor calibrated in step S1 at different locations of the underwater operation vehicle;

[0008] S3. Determine the water quality according to the preset water quality judgment index, and dynamically adjust the weights of the optical sensor and the acoustic sensor according to the water quality judgment result;

[0009] S4. Using an acoustic sensor and an optical sensor to simultaneously collect ranging data of the target, and using a fusion algorithm to perform a weighted fusion calculation on the weights adjusted in step S3 and the ranging data, and optimizing the weighted fusion calculation result, and performing a weighted fusion calculation again based on the optimization result to obtain a final ranging distance;

[0010] S5. Arrange carriers at different orientations of the target, perform weighted fusion calculation on the carriers in each orientation using the fusion algorithm described in step S4, obtain the final ranging distance from each carrier to the target, and calculate the underwater position of the target in combination with the positioning algorithm.

[0011] Preferably, in step S1, calibrating the acoustic sensor and optical sensor to be installed is specifically performed as follows:

[0012] For acoustic sensors, the sensor to be calibrated is compared with a standard sensor of known accuracy. Under the same conditions, the same physical quantity, including frequency and sensitivity, is measured. The output difference between the two is compared, and the sensor to be calibrated is adjusted, such as the internal gain or offset, until the two are consistent.

[0013] For optical sensors, there are two types of calibration: emission intensity calibration and receiving accuracy calibration. The emission intensity calibration uses an optical power meter to measure the optical power emitted by the optical sensor. Standard optical attenuation sheets with different transmittances are prepared to simulate different measurement environments. The standard emission optical power is set according to the requirements of the underwater operating environment. The emission intensity deviation is calculated and the emission intensity of the optical sensor is changed by adjusting the current of the driving power supply. Attenuation sheets with different transmittances are inserted into the optical path in sequence to simulate different water quality environments. The emission optical power is measured and adjusted until the emission optical power meets the requirements under various simulated environments.

[0014] The receiving accuracy calibration is to fix the optical sensor on a measuring frame in a darkroom environment and place a standard reflector. The optical sensor transmits a light signal, which is received after being reflected by the standard reflector. The characteristic parameters of the received light signal are recorded, and the characteristic parameters include pulse width and light intensity. According to the parameters of the standard reflector and the optical path distance, the deviation between the theoretical characteristic parameters and the actual characteristic parameters is calculated. The bias voltage of the photodetector is adjusted according to the deviation between the theoretical characteristic parameters and the actual characteristic parameters. The light signal is transmitted and received again, and the theoretical characteristic parameters are compared and analyzed with the actual measurement parameters. The adjustment steps are repeated until the receiving accuracy meets the requirements.

[0015] Preferably, in step S2, the acoustic sensor and the optical sensor calibrated in step S1 are installed at different locations of the underwater operation vehicle, respectively:

[0016] The calibrated acoustic sensor and optical sensor are respectively installed on different parts of the underwater operation carrier, the acoustic sensor is installed on both sides or the bottom of the carrier, and the optical sensor is installed on the front of the carrier, wherein the underwater operation carrier includes an underwater robot or a submersible.

[0017] Preferably, in step S3, the water quality is judged according to a preset water quality judgment index, and the weights used by the optical sensor and the acoustic sensor are dynamically adjusted according to the water quality judgment result. Specifically,

[0018] A water quality determination unit is provided in the optical sensor, and an indicator range threshold is preset in the water quality determination unit. The water quality determination unit collects an indicator of the current water quality, wherein the indicator is the current water quality transparency. When the indicator collected by the water quality determination unit is within the indicator range threshold, the current water quality is classified according to the indicator range threshold result. The weights used by the optical sensor and the acoustic sensor are adjusted respectively according to the classified water quality results;

[0019] Preferably, in step S3, the preset indicator range threshold is specifically:

[0020] When the water transparency is greater than 4 meters and equal to 4 meters, it means that the current water quality is clear;

[0021] When the water transparency is greater than 2 meters and equal to 2 meters, and less than 4 meters, it means that the current water quality is slightly turbid;

[0022] When the water transparency is less than 2 meters, it means that the current water quality is deeply turbid;

[0023] Preferably, in step S3, the weight adjustment is specifically:

[0024] When the current water quality is clear, the optical sensor weight is adjusted to 0.7 and the acoustic sensor weight is adjusted to 0.3;

[0025] When the current water quality is slightly turbid, the optical sensor weight and acoustic sensor weight are adjusted to 0.5 respectively;

[0026] When the current water quality is deeply turbid, the optical sensor weight is adjusted to 0.3 and the acoustic sensor weight is adjusted to 0.7.

[0027] Preferably, in step S4, the ranging data of the target are collected simultaneously using an acoustic sensor and an optical sensor, and a fusion algorithm is used to perform a weighted fusion calculation on the weight adjusted in step S3 and the ranging data, and the weighted fusion calculation result is optimized, and a weighted fusion calculation is performed again based on the optimization result to obtain the final ranging distance:

[0028] The carrier transmits a sound wave signal of a specific frequency through the transducer in the acoustic sensor. After receiving the target's reflected echo, the target distance is calculated based on the time difference of the sound wave propagation to obtain the acoustic ranging data. The optical sensor transmits a light signal through the laser transmitter, and the optical receiver receives the reflected light signal. The target distance is calculated based on the round-trip time of the light signal to obtain the optical ranging data, which is calculated as:

[0029] Acoustic ranging data:

[0030]

[0031] Among them, d s The target distance between the carrier and the target measured by the acoustic sensor, v s is the propagation speed of sound waves in water, t1 is the time when the acoustic sensor transmits the sound wave, and t2 is the time when the acoustic sensor receives the target reflected sound wave;

[0032] Optical ranging data:

[0033]

[0034] Among them, d l The target distance between the carrier and the target measured by the optical sensor, v l is the propagation speed of sound waves in water, t3 is the time when the optical sensor emits the light pulse, and t4 is the time when the optical sensor receives the target reflected light pulse;

[0035] After acquiring the acoustic ranging data and the optical ranging data multiple times, performing outlier processing on the acoustic ranging data and the optical ranging data, wherein the outlier processing comprises preprocessing the acoustic ranging data and the optical ranging data using a Z-score function and processing the outliers, wherein the processing method includes deleting or replacing the outliers;

[0036] After outlier processing, the acoustic ranging dataset A and the optical ranging dataset B are output, where A={a1,a2,…,a n}, where B={b1,b2,…,b n};

[0037] Calculating average values for the acoustic ranging data set A and the optical ranging data set B, respectively, to obtain average acoustic ranging data and average optical ranging data; adjusting weights used by the optical sensor and the acoustic sensor according to the water quality result classified in step S2; performing a weighted fusion calculation on the adjusted weights and the average acoustic ranging data and the average optical ranging data using a weighted summation method; optimizing the weight distribution of the fused ranging results using a least squares method during the weighted fusion calculation; and performing a weighted fusion calculation on the optimized weights used by the optical sensor and the acoustic sensor again with the average acoustic ranging data and the average optical ranging data to obtain a final ranging distance;

[0038] Preferably, in step S4, the weighted fusion calculation is specifically:

[0039] d'=d s ×ω s +d l ×ω l

[0040] Where d' is the target distance between the carrier and the target, d s is the average acoustic ranging data, d l is the average optical distance measurement data, ω s is the acoustic sensor weight, ω l is the optical sensor weight;

[0041] Preferably, in step S4, the least squares optimization is specifically:

[0042] The objective functions are constructed for the acoustic sensor weights and the optical sensor weights in the weighted fusion calculation respectively. The objective functions are specifically:

[0043]

[0044] Where n is the number of sensor measurements, d i is the actual distance between the carrier and the target in the i-th measurement, d si is the acoustic ranging data in the i-th measurement, d li is the optical distance measurement data in the i-th measurement, ω s is the acoustic sensor weight, ω l is the optical sensor weight.

[0045] Preferably, in step S5, carriers are arranged at different orientations of the target, and weighted fusion calculation is performed on the carriers in each orientation using the fusion algorithm in step S4 to obtain the final ranging distance from each carrier to the target, and the underwater position of the target is calculated in combination with the positioning algorithm as follows:

[0046] Arrange multiple carriers equipped with optical sensors and acoustic sensors at different positions of the target, calculate the final distance between each carrier and the target using the fusion algorithm described in step S4, establish a three-dimensional coordinate system with one of the carriers as the origin, and use a triangulation algorithm to obtain the underwater position of the target by combining the carrier's own coordinates and the final distance between each carrier and the target;

[0047] Preferably, in step S5, the triangulation positioning algorithm is specifically:

[0048] Assume that there are n known vectors P in three-dimensional space i (x i ,y i ,z i ), i=1, 2, ..., n, the known distance measurement point P i The final distance to the target point T(x,y,z) is d i , calculate the position of the target point according to the distance formula between two points in space, which is:

[0049]

[0050] Among them, x, y, and z are the coordinates of the target point, x i 、y i 、z i is the coordinate corresponding to the carrier, d i is the distance between the carrier and the target point.

[0051] The present invention installs a calibrated acoustic sensor and an optical sensor on different parts of a carrier, uses a water quality judgment unit in the optical sensor to judge water quality according to a water transparency threshold, dynamically adjusts the use weights of the acoustic sensor and the optical sensor according to the water quality judgment result, uses the acoustic sensor and the optical sensor to simultaneously collect ranging data of the target, uses a fusion algorithm to perform weighted fusion calculation on the adjusted weight and the ranging data, optimizes the weighted fusion calculation result, and performs weighted fusion calculation again according to the optimization result to obtain a final ranging result, arranges carriers at different orientations of the target, performs weighted fusion calculation on the carriers in each orientation by the fusion algorithm, obtains the final ranging distance from each carrier to the target, and calculates the underwater position of the target in combination with a positioning algorithm. The present invention has the advantages of high ranging and positioning accuracy and high reliability under different water quality conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 1 is a structural block diagram of an underwater ranging and positioning method according to an embodiment of the present invention;

[0053] Figure 2 The figure is a flowchart of the steps of an underwater ranging and positioning method in an embodiment of the present invention. DETAILED DESCRIPTION

[0054] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are merely used to explain the present invention and are not intended to limit the present invention.

[0055] The preferred implementation methods of the present invention are described below with reference to the accompanying drawings. Those skilled in the art should understand that these implementation methods are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0056] See also Figure 1-Figure 2 As shown, an underwater ranging and positioning method according to an embodiment of the present invention includes:

[0057] S1. Calibrate the acoustic and optical sensors to be installed;

[0058] S2. Install the acoustic sensor and optical sensor calibrated in step S1 at different locations of the underwater operation vehicle;

[0059] S3. Determine the water quality according to the preset water quality judgment index, and dynamically adjust the weights of the optical sensor and the acoustic sensor according to the water quality judgment result;

[0060] S4. Using an acoustic sensor and an optical sensor to simultaneously collect ranging data of the target, and using a fusion algorithm to perform a weighted fusion calculation on the weights adjusted in step S3 and the ranging data, and optimizing the weighted fusion calculation result, and performing a weighted fusion calculation again based on the optimization result to obtain a final ranging distance;

[0061] S5. Arrange carriers at different orientations of the target, perform weighted fusion calculation on the carriers in each orientation using the fusion algorithm described in step S4, obtain the final ranging distance from each carrier to the target, and calculate the underwater position of the target in combination with the positioning algorithm.

[0062] like Figure 2 As shown, in step S1 , the acoustic sensor and the optical sensor to be installed are calibrated.

[0063] Specifically, in this embodiment, for an acoustic sensor, the acoustic sensor to be calibrated and a standard acoustic sensor are simultaneously measured for acoustic signals of the same frequency, and the output difference between the two is compared. If the frequency value output by the sensor to be calibrated deviates from the standard value, the internal gain of the sensor to be calibrated is adjusted to make the output frequency consistent with the standard value.

[0064] For optical sensors, it is divided into emission intensity calibration and receiving accuracy calibration. For emission intensity calibration, an optical power meter with an accuracy of ±0.01dBm is used to measure the optical power emitted by the optical sensor, and standard optical attenuation sheets with transmittances of 20%, 50%, and 80% are prepared to simulate the light attenuation in different water quality environments. According to the common environment of underwater operations, the standard emission optical power is set, and the optical power meter is placed at the transmitting end of the optical sensor to measure the initial emission optical power. By adjusting the driving power supply current, the emission optical power is gradually increased, and attenuation sheets with different transmittances are inserted into the optical path in sequence. When the 20% transmittance attenuation sheet is inserted, if the measured optical power does not meet the requirements that should be maintained in the simulated environment, continue to fine-tune the driving power supply current until the optical power reaches the required range. Repeat the operation for the 50% and 80% transmittance attenuation sheets to ensure that the emission optical power is stable and meets the standards in various simulated environments.

[0065] For receiving accuracy calibration, in a darkroom environment, the optical sensor is fixed on a high-precision measuring frame to ensure the stable position of the sensor. A standard reflector with a reflectivity of 90% is placed, and the distance between the reflector and the sensor is precisely 50 cm. The optical sensor transmits a light signal, which is received after being reflected by the standard reflector. The pulse width and light intensity characteristic parameters of the received light signal are recorded. According to the parameters of the standard reflector and the optical path distance, the theoretical pulse width and theoretical light intensity characteristic parameters are calculated. If there is a deviation between the actual measured pulse width and the light intensity characteristic parameters, the bias voltage of the photodetector is adjusted to change the response characteristics of the light signal. After adjustment, the light signal is transmitted and received again, and the theoretical and actual characteristic parameters are compared and analyzed. The adjustment is repeated until the pulse width and light intensity characteristic parameters meet the receiving accuracy requirements.

[0066] like Figure 2 As shown, in step S2, the acoustic sensor and optical sensor calibrated in step S1 are respectively installed on different parts of the underwater operation vehicle.

[0067] Specifically, in this embodiment, the calibrated acoustic sensor and optical sensor are respectively installed on different parts of the underwater working carrier. The acoustic sensor is installed on both sides or the bottom of the carrier. Such a layout is conducive to receiving sound wave signals in all directions and reducing signal obstruction; the optical sensor is installed at the front of the carrier to facilitate it to capture the target's optical signal in the forward direction of the carrier, wherein the underwater working carrier includes an underwater robot or a submersible.

[0068] like Figure 2 As shown, in step S3, the water quality condition is judged according to the preset water quality judgment index, and the weights used by the optical sensor and the acoustic sensor are dynamically adjusted according to the water quality judgment result.

[0069] Specifically, in this embodiment, a water quality determination unit is provided in the optical sensor, and an indicator range threshold is preset in the water quality determination unit. The water quality determination unit collects an indicator of the current water quality, wherein the indicator is the current water transparency. When the indicator collected by the water quality determination unit is within the indicator range threshold, the current water quality is classified according to the indicator range threshold result. Based on the classified water quality results, the weights used by the optical sensor and the acoustic sensor are adjusted respectively.

[0070] During the underwater operation of the carrier, the water quality judgment unit collects the transparency index of the current water quality at a frequency of once per minute. At a certain moment, the water transparency measured by the water quality judgment unit is 2.5 meters. According to the above measurement results, 2.5 meters is within the range of greater than 2 meters and equal to 2 meters, and less than 4 meters, so the water quality is classified as slightly turbid. Based on this water quality classification result, the carrier will automatically adjust the usage weights of the optical sensor and the acoustic sensor. When the water quality is slightly turbid, the optical sensor weight and the acoustic sensor weight are adjusted to respectively. 0.5. In the subsequent ranging data collection, the optical sensor and the acoustic sensor participate in the data fusion calculation with the same weight to balance the measurement performance of the two in slightly turbid water. As time goes by, when the water clarity measured by the water quality judgment unit is 1.5 meters, the water quality is in the range of less than 2 meters and is classified as deeply turbid. The optical sensor weight is adjusted to 0.3 and the acoustic sensor weight is adjusted to 0.7. This dynamic adjustment method makes the role of the two sensors in data fusion more balanced, thereby improving the accuracy of overall ranging and positioning.

[0071] like Figure 2 As shown, in step S4, the acoustic sensor and the optical sensor are used to simultaneously collect the ranging data of the target, and a fusion algorithm is used to perform a weighted fusion calculation on the weight adjusted in step S3 and the ranging data, and the weighted fusion calculation result is optimized, and a weighted fusion calculation is performed again based on the optimization result to obtain the final ranging result.

[0072] Specifically, in this embodiment, the acoustic sensor transducer of the carrier transmits a sound wave signal with a frequency of 30kHz. At a certain moment, the sensor transmits the sound wave, which is recorded as time t1=0s. After a period of time, the sound wave encounters the target and is reflected back. The acoustic sensor receives the reflected sound wave, which is recorded as t2=0.2s. The propagation speed of the sound wave underwater is v s =1500m / s, and the acoustic ranging target distance is calculated according to the acoustic ranging formula:

[0073]

[0074] The optical sensor laser transmitter of the carrier transmits a light signal at t3 = 0s. The light signal is reflected by the target and received by the light receiver at t4 = 0.0000012s. The propagation speed of light in water is approximately three-quarters of the propagation speed in vacuum, that is, v l =2.25×10 8 , according to the optical ranging formula, the optical ranging target distance is calculated as:

[0075]

[0076] After three measurements and calculations, the acoustic ranging data are d s1 =150m,d s2 =152m,d s3 =148m, the optical distance measurement data are d l1 =135m,d l2 =133m,d l3 =137m, use the Z-score function to pre-process the acoustic ranging data and the optical ranging data, define |Z|>3 as an abnormal value, and the normal range of Z value is (-3, 3). When the output Z value is not in the normal range, it is an abnormal value, and the abnormal value is processed, including deleting or replacing the abnormal value;

[0077] The average values of the three pre-processed acoustic ranging data and optical ranging data are calculated as follows:

[0078] Average acoustic ranging data:

[0079]

[0080] Average optical distance measurement data:

[0081]

[0082] Assuming that the water quality judgment unit determines that the current water quality is deeply turbid, the optical sensor weight is adjusted to 0.3, and the acoustic sensor weight is adjusted to 0.7. The target distance between the carrier and the target is calculated based on the weighted fusion:

[0083] d'=150×0.7+135×0.3=145.5m

[0084] In order to reduce the possible interference between optical ranging data and acoustic ranging data due to the complexity and uncertainty of the underwater environment, which may lead to errors, the least squares method is used to optimize the weighted fusion calculation in the weighted fusion calculation process, and the objective functions of the acoustic sensor weight and the optical sensor weight in the weighted fusion calculation are constructed respectively, which are constructed as follows:

[0085]

[0086] The acoustic ranging data after three preprocessings are weighted and fused with the optical ranging data. The weight of the optical sensor is adjusted by 0.3 and the weight of the acoustic sensor is adjusted by 0.7. The data is substituted into the function. By taking the derivative of the objective function and setting the derivative to 0, the optimal weight of the optimized acoustic sensor is 0.699 and the optimal weight of the optical sensor is 0.301. The final ranging distance is output as:

[0087] d'=150×0.699+135×0.301=145.485m

[0088] The weighted fusion calculation is optimized through the least squares method to reduce the error and further improve the accuracy of ranging.

[0089] like Figure 2 As shown, in step S5, carriers are arranged at different orientations of the target, and weighted fusion calculation is performed on the carriers in each orientation through the fusion algorithm described in step S4 to obtain the final ranging distance from each carrier to the target, and the position of the target underwater is calculated in combination with the positioning algorithm.

[0090] Specifically, in this embodiment, three carriers P1, P2, and P3 equipped with optical and acoustic sensors are arranged in front of, above, and behind the target, respectively. The three carriers are arranged in an equilateral triangle with the target point as the center. A coordinate system is established with the front carrier P1 as the origin. The forward direction of the front carrier is the positive direction of the X axis, the direction perpendicular to the X axis and pointing to the right is the positive direction of the Y axis, and the direction perpendicular to the carrier plane and pointing upward is the positive direction of the Z axis. The coordinate system constructed in this way can provide a reference for describing the position of one carrier relative to the other carriers.

[0091] The final distances between the three carriers and the target point are calculated using a weighted fusion algorithm to obtain d1, d2, and d3. The coordinates of the remaining two carriers are determined using trigonometric functions. The position of the target point is calculated using the distance formula between two points in space, which is:

[0092]

[0093] Solve the equations to obtain the coordinate value of the target point T, thereby realizing the positioning of the target point.

[0094] Thus far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present invention.

[0095] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. An underwater ranging and positioning method, characterized in that: The following steps are involved: S1. Calibrate the acoustic and optical sensors to be installed; S2. Install the acoustic sensor and optical sensor calibrated in step S1 at different locations of the underwater operation vehicle; S3. Determine the water quality according to the preset water quality judgment index, and dynamically adjust the weights of the optical sensor and the acoustic sensor according to the water quality judgment result; S4. Using an acoustic sensor and an optical sensor to simultaneously collect ranging data of the target, and using a fusion algorithm to perform a weighted fusion calculation on the weights adjusted in step S3 and the ranging data, and optimizing the weighted fusion calculation result, and performing a weighted fusion calculation again based on the optimization result to obtain a final ranging distance; S5. Arrange carriers at different orientations of the target, perform weighted fusion calculation on the carriers in each orientation using the fusion algorithm described in step S4, obtain the final ranging distance from each carrier to the target, and calculate the underwater position of the target in combination with the positioning algorithm.

2. The underwater ranging and positioning method according to claim 1, wherein: The acoustic sensor is calibrated as: The acoustic sensor to be calibrated is compared with a standard sensor of known accuracy. Under the same conditions, the same physical quantity, including frequency and sensitivity, is measured. The output difference between the two is compared, and the calibrated sensor is adjusted to adjust the internal gain or offset until the two are consistent.

3. The underwater ranging and positioning method according to claim 1, wherein: The optical sensor is calibrated as: For optical sensors, there are two types of calibration: emission intensity calibration and receiving accuracy calibration. The emission intensity calibration uses an optical power meter to measure the optical power emitted by the optical sensor. Standard optical attenuation sheets with different transmittances are prepared to simulate different measurement environments. The standard emission optical power is set according to the requirements of the underwater operating environment. The emission intensity deviation is calculated and the emission intensity of the optical sensor is changed by adjusting the current of the driving power supply. Attenuation sheets with different transmittances are inserted into the optical path in sequence to simulate different water quality environments. The emission optical power is measured and adjusted until the emission optical power meets the requirements under various simulated environments. The receiving accuracy calibration is to fix the optical sensor on a measuring frame in a darkroom environment and place a standard reflector. The optical sensor transmits a light signal, which is received after being reflected by the standard reflector. The characteristic parameters of the received light signal are recorded, and the characteristic parameters include pulse width and light intensity. According to the parameters of the standard reflector and the optical path distance, the deviation between the theoretical characteristic parameters and the actual characteristic parameters is calculated. The bias voltage of the photodetector is adjusted according to the deviation between the theoretical characteristic parameters and the actual characteristic parameters. The light signal is transmitted and received again, and the theoretical characteristic parameters are compared and analyzed with the actual measurement parameters. The adjustment steps are repeated until the receiving accuracy meets the requirements.

4. The underwater ranging and positioning method according to claim 1, wherein: The acoustic sensors are installed on both sides or the bottom of the carrier, and the optical sensor is installed on the front of the carrier.

5. The underwater ranging and positioning method according to claim 1, wherein: The water quality is judged according to the preset water quality judgment index, and the weights used by the optical sensor and the acoustic sensor are dynamically adjusted according to the water quality judgment result: A water quality judgment unit is set in the optical sensor, and an indicator range threshold is preset in the water quality judgment unit. The water quality judgment unit collects indicators of the current water quality, and the indicator is the current water quality transparency. When the indicator collected by the water quality judgment unit is within the indicator range threshold, the current water quality is classified according to the indicator range threshold result. According to the classified water quality results, the weights used by the optical sensor and the acoustic sensor are adjusted respectively.

6. The underwater ranging and positioning method according to claim 5, characterized in that: The preset indicator range threshold is: When the water transparency is greater than 4 meters and equal to 4 meters, it means that the current water quality is clear; When the water transparency is greater than 2 meters and equal to 2 meters, and less than 4 meters, it means that the current water quality is slightly turbid; When the water transparency is less than 2 meters, it means that the water is deeply turbid.

7. The underwater ranging and positioning method according to claim 5, characterized in that: The weight adjustment is: When the current water quality is clear, the optical sensor weight is adjusted to 0.7 and the acoustic sensor weight is adjusted to 0.3; When the current water quality is slightly turbid, the optical sensor weight and acoustic sensor weight are adjusted to 0.5 respectively; When the current water quality is deeply turbid, the optical sensor weight is adjusted to 0.3 and the acoustic sensor weight is adjusted to 0.

7.

8. The underwater ranging and positioning method according to claim 1, wherein: The weighted fusion calculation is: d'=d s ×ω s +d l ×ω l Where d' is the target distance between the carrier and the target, d s is the average acoustic ranging data, d l is the average optical distance measurement data, ω s is the acoustic sensor weight, ω l is the optical sensor weight.

9. The underwater ranging and positioning method according to claim 1, wherein: The minimum multiplication optimization is: The objective functions are constructed for the acoustic sensor weights and the optical sensor weights in the weighted fusion calculation respectively. The objective functions are: Where n is the number of sensor measurements, d i is the actual distance between the carrier and the target in the i-th measurement, d si is the acoustic ranging data in the i-th measurement, d li is the optical distance measurement data in the i-th measurement, ω s is the acoustic sensor weight, ω l is the optical sensor weight.

10. The underwater ranging and positioning method according to claim 1, wherein: The triangulation positioning algorithm is: Assume that there are n known vectors P in three-dimensional space i (x i ,y i ,z i ), i=1, 2, ..., n, the known distance measurement point P i The final distance to the target point T(x,y,z) is d i , calculate the position of the target point according to the distance formula between two points in space, which is: Among them, x, y, and z are the coordinates of the target point, x i 、y i 、z i is the coordinate corresponding to the carrier, d i is the distance between the carrier and the target point.

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