Flexible cable shape construction and tail end positioning method and system based on gradient distribution prediction

Abstract

The invention discloses a gradient distribution prediction-based flexible cable shape construction and tail end positioning method and system, and the method comprises the steps: obtaining attitude data of each installation position based on inertial measurement units installed on a cable in a distributed manner, and solving an attitude matrix of position nodes; defining a unit gradient vector and converting the unit gradient vector to a navigation coordinate system; establishing a cable gradient change model; the gradient change function of the cable is predicted through a cubic spline difference method, then the underwater flexible shape is restored according to the length integral of the cable, and all points and the tail end of the cable are positioned. According to the method, the requirements for the number of nodes and precision are not high, and verification results show that the relative positioning precision can be superior to 2%, and the relative positioning precision can reach 0.05% in a high-precision environment. Effective theoretical support is provided for precision optimization of the deep sea observation system based on the flexible cable, and a technical foundation is laid for deep sea positioning and exploration.

Description

Technical Field

[0001] The invention relates to the field of flexible connection measurement, and in particular to a method and system for shape construction and end positioning of a flexible cable. Background Art

[0002] The seabed observation network is a new platform for human beings to observe the ocean. It can realize all-weather, in-situ, long-term, continuous, real-time, high-resolution and high-precision observation of the ocean from the seabed to the sea surface, and plays an important supporting role in the development of marine science. Driven by new technologies such as modern sensors, underwater robots, submarine optical fiber cables, the Internet of Things, and big data, the seabed observation network presents a development trend of comprehensive three-dimensional observation, deep data mining, and comprehensive cross-integration of multiple observation plans.

[0003] At present, my country has initially formed the basic framework of the ocean observation network covering shore-based ocean observation systems, offshore ocean observation systems, and ocean and polar observations, providing important support for my country's marine disaster prevention and mitigation, scientific research and other fields. Among the many observation networks, buoys, submerged buoys, towing platforms, etc. are widely used. Among them, flexible cables, as an important component, are responsible for connecting, fixing, and guiding underwater equipment, and play an important role. Cables have the characteristics of long distance, small mass, high strength, low cost, portability and easy retraction, and are widely used in ocean sensor observation systems. One end of the cable is usually moored to a surface platform or a bottom anchor, and the other end is connected to sensors and other equipment. However, the soft and curved nature of the mooring cable itself combined with the action of ocean currents will cause problems such as dynamic changes in the shape of the cable and uncertainty in the position of the end sensor. This has a great impact on the perception accuracy of the underwater observation system.

[0004] The development of underwater navigation and positioning technology has been able to meet some underwater positioning needs by using methods such as acoustics, but the cost is high and the response speed is slow. For some short-distance and low-precision scenarios, the drift effect of underwater mooring cables is often technically ignored. These problems need to be solved urgently. Summary of the invention

[0005] Purpose of the invention: The purpose of the present invention is to propose a flexible cable shape construction and terminal positioning method and system based on gradient distribution prediction to solve the problem that underwater mooring cables are difficult to locate due to unknown shapes. The method is low-cost, simple to operate, and high-precision. It is not only suitable for underwater observation, but can also be promoted and applied to other flexible connection measurement fields.

[0006] Technical solution: In order to achieve the above invention objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, a method for constructing a flexible cable shape and locating an end portion based on gradient distribution prediction comprises the following steps:

[0008] Acquire attitude data of each installation position based on an inertial measurement unit distributedly installed on the cable, and solve the attitude matrix of the position node based on the attitude data;

[0009] The length direction of the cable from the starting end to the end is defined as the gradient direction, and λ is the unit gradient vector, that is, the coordinate change caused by the change of the unit length cable. According to the attitude matrix and the projection coordinate λ of the unit gradient vector λ in the carrier coordinate system b , get the projection coordinates of the unit gradient vector in the navigation coordinate system n represents the navigation coordinate system, b represents the carrier coordinate system;

[0010] According to the continuity characteristics of the cable, a continuous cable structure model of arbitrary shape is established, and the coordinates of any point on the cable are expressed as a continuous function of the cable length l: Among them, X(l), Y(l), and Z(l) are the x-coordinate, y-coordinate, and z-coordinate of the cable at any length l, respectively. is the gradient change function. According to the definition of λ, the relationship between the unit gradient vector and the gradient change function is established.

[0011] The gradient variation function of the cable is predicted by the cubic spline difference method, and then the underwater flexible shape is restored by integrating the cable length according to the cable structure model, and each point on the cable and the end are located.

[0012] In a second aspect, a flexible cable shape construction and end positioning system based on gradient distribution prediction includes:

[0013] A node attitude calculation module is used to obtain attitude data of each installation position based on the inertial measurement unit distributedly installed on the cable, and solve the attitude matrix of the position node based on the attitude data;

[0014] The gradient definition and conversion module is used to define the length direction of the cable from the starting end to the end as the gradient direction, λ is the unit gradient vector, that is, the coordinate change caused by the change of the unit length cable, according to the attitude matrix and the projection coordinate λ of the unit gradient vector λ in the carrier coordinate system b , get the projection coordinates of the unit gradient vector in the navigation coordinate system n represents the navigation coordinate system, b represents the carrier coordinate system;

[0015] The gradient change model building module is used to establish a continuous cable structure model of any shape according to the continuity characteristics of the cable, and express the coordinates of any point on the cable as a continuous function of the cable length l: Among them, X(l), Y(l), and Z(l) are the x-coordinate, y-coordinate, and z-coordinate of the cable at any length l, respectively. is the gradient change function. According to the definition of λ, the relationship between the unit gradient vector and the gradient change function is established.

[0016] The solution calculation module is used to predict the gradient change function of the cable through the cubic spline difference method, and then restore the underwater flexible shape by integrating the cable length according to the cable structure model, and locate each point on the cable and the end.

[0017] In a third aspect, a computer device comprises: one or more processors; a memory; and one or more programs, wherein the one or more programs are stored in the memory and are configured to be executed by the one or more processors, and when the programs are executed by the processors, the steps of the flexible cable shape construction and end positioning method based on gradient distribution prediction as described in the first aspect are implemented.

[0018] In a fourth aspect, a computer-readable storage medium having a computer program stored thereon, characterized in that when the computer program is executed by a processor, the steps of the flexible cable shape construction and end positioning method based on gradient distribution prediction as described in the first aspect are implemented.

[0019] Beneficial effects: Cables are widely used in marine fields such as buoys, moorings, and towing. The dynamic changes in the position of underwater sensors caused by this flexible structure bring difficulties to marine observation. The present invention proposes a shape construction and end positioning method based on gradient distribution prediction, which provides a low-cost solution to the problem of uncertain underwater position of this flexible cable. The method uses a certain number of sensor nodes distributedly installed on the wet-end cable to measure the posture of different positions of the cable, predict the gradient change function of the cable by the cubic spline difference method, and then restore the underwater flexible shape according to the integral of the cable length, and locate each point on the cable and the end. The method was verified by simulating the underwater structure of the cable. The results show that the method does not require high node number and accuracy, and the relative positioning accuracy can be better than 2%. The relative positioning accuracy can be as high as 0.05% in a high-precision environment. This provides effective theoretical support for the accuracy optimization of deep-sea observation systems based on flexible cables, and lays a technical foundation for deep-sea positioning and exploration. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the underwater cable connection structure and usage;

[0021] Figure 2 is a flow chart of the method of the present invention;

[0022] Figure 3 Simplified model for towed sonar cable;

[0023] Figure 4 This is a schematic diagram of node gradient analysis;

[0024] Figure 5 This is an example of simulation of a towed sonar cable structure;

[0025] Figure 6 Bottom and side views of the cable simulation structure;

[0026] Figure 7 is the cable gradient prediction result (n=21, attitude error is 0.1°);

[0027] Figure 8 is the estimated positioning error of the entire cable segment (n = 21, the attitude error is 0.1°);

[0028] Fig. 9 is the cable gradient prediction result (n=11, attitude error is 0.1°);

[0029] Fig.10 The estimated error for the cable's entire segment positioning is n = 11, and the attitude error is 0.1°);

[0030] Fig.11 Comparison of cable shape construction errors for different numbers of nodes;

[0031] Fig.12 is the cable gradient prediction result (n=21, attitude error is 0.5°&5°);

[0032] Fig.13 is the estimated positioning error of the entire cable segment (n=21, attitude error is 0.5°&5°);

[0033] Fig.14 Comparison of cable shape construction errors at different attitude accuracies. DETAILED DESCRIPTION

[0034] In order to have a clearer understanding of the features and advantages of the technical solution of the present invention, the composition and implementation of the specific solution are explained below in conjunction with the accompanying drawings.

[0035] The present invention is dedicated to solving the problem of random changes in the underwater shape of mooring cables. To this end, the following three underwater connection structures and usage methods of mooring cables are summarized, such as Figure 1 shown.

[0036] 1) Buoy suspension cable structure

[0037] Buoys play an important role in ocean monitoring and underwater communications. They are lightweight and easy to deploy, so they are widely used. Usually, the part of the buoy above the water surface is called the dry end, which is mainly composed of floats, communication equipment and satellite positioning equipment, and is responsible for the functions of buoy coordinate monitoring and data transmission and reception. The part of the buoy below the water surface is the wet end, which is equipped with different sensors to collect data, such as temperature, salinity, pressure, sonar and other equipment.

[0038] The Argo program, a global ocean observation experiment project, has deployed 3,000 buoys around the world, dedicated to measuring the temperature, salinity, and depth profiles of the ocean subsurface. In order to deeply measure the ocean parameters of different water layers, the wet end is very long and the maximum depth is up to 2km. Therefore, they are all made of flexible cable structures, and fixed sensors are spaced at a certain distance to collect the corresponding deep ocean parameters, so as to obtain the profile distribution of hydrological data. Strictly speaking, this profile is not a vertical line below the position of the dry end GNSS (Global Navigation Satellite System) because the bending deformation of the wet end makes the position of each underwater sensor node uncertain. Usually, the hydrological data and depth of these nodes are recorded one by one, and the horizontal coordinates are ignored. First, it is difficult to measure the real-time horizontal position underwater, and second, it is assumed that the local hydrological environment changes have little difference in the horizontal direction. However, for severe sea conditions, hydrological conditions at different locations may suddenly change, and the large offset of each node at the wet end may cause inaccurate profile data (the horizontal deviation of a 2km rope length can reach 1km). Therefore, fast and easy real-time horizontal positioning is very helpful for buoy detection.

[0039] Positioning sonar is also often deployed using buoy carriers. Sonar buoys are an important part of PNT (Positioning, Navigation, and Timing) and are the transit of cross-space information exchange between underwater and surface. At the same time, buoy sonars combined with underwater sonar anchor nodes form a three-dimensional spatial positioning network that can provide high-precision underwater positioning services. The transducer and hydrophone fixed at the end of the wet end cable receive the sonar information of the underwater target, and then calculate the positioning. Among them, the offset between the end and the dry end affects the positioning accuracy. In order to avoid interference and obtain a good acoustic environment, the end hydrophone needs to penetrate the remote acoustic channel water layer of the acoustic channel axis below 200m. Therefore, long-distance buoy sonars need to solve the problem of relative offset measurement at the end. Another passive detection buoy also has hydrophones deployed at intervals on the wet end cable to identify the signal arrival direction of the detection target. The underwater offset position of the hydrophone at each node can also improve the positioning accuracy.

[0040] 2) Subsea mooring structure

[0041] The deployment methods of submarine equipment are divided into bottom deployment and moored deployment. The bottom-deployed equipment is fixed on the seabed under the action of counterweights, such as seismic monitors and bottom mines. The bottom-deployed method has the advantage of stable kinematic state and fixed position coordinates. The moored equipment is connected by anchor chains, with the bottom end anchored on the seabed and the upper end suspended in the water. The advantage of moored deployment is that the equipment is far away from the seabed, creating a good environment for sending and receiving acoustic signals. Underwater transponders, semi-floating mines, etc. adopt this method, and large platforms will be moored and stabilized by multiple anchor chains. However, due to the surging of underwater ocean currents, the position and attitude of moored equipment vary greatly, and the coordinates of pre-deployed transponders in positioning arrays such as long baselines will be different from the actual position. This can often be ignored during long-distance positioning, but this error has a greater impact on positioning calculations during close-range detection. For pre-placed platforms such as semi-floating mines, the dynamically changing position and attitude have a greater interference with the initial alignment process before execution. Therefore, real-time monitoring of the position of underwater moored deployment equipment can better exert its effect.

[0042] 3) Surface platform towing structure

[0043] Many underwater detection equipment do not have a power source and need to be towed by a surface ship to move, such as towed sonar and side-scan sonar. This towed structure is similar to a buoy. The dry end is considered to be fixed or has known satellite positioning information, and the wet end is connected by a cable, which can reach hundreds of meters underwater. Towed sonar is used to passively detect the position of enemy submarines. Its linear structure forms a baseline array with a certain azimuth perception capability, but it is limited by its single structure and cannot eliminate the port and starboard ambiguity problem. Once the underwater structure of the towed sonar can be accurately sensed in real time, the detection and identification capabilities of the towed sonar will be greatly improved. The side-scan sonar depicts the terrain below after being released from the cable. Since the underwater shape of the cable is not a taut straight line, the position of the side-scan sonar will be greatly deviated based solely on the length of the cable. Therefore, the underwater shape structure of the cable needs to be constructed.

[0044] The above problems can be summarized as the real-time construction of the flexible shape of the cable underwater, and the reconstruction of its structure to achieve precise positioning of any node on the cable including the end. In order to solve the above problems, the present invention proposes a shape reconstruction and end positioning method based on gradient distribution prediction. The attitude information of the distributed nodes on the cable is used to predict the gradient change state of the cable, and then the spatial structure of the entire cable is calculated based on the prior integral of the cable length. The attitude information is calculated in real time by the MEMS (Micro-Electro-Mechanical Systems) sensors installed at the nodes. The spatial structure of the cable provides the relative position of each point. Considering that the starting end generally has accurate GNSS position information, adding the relative position on this basis can achieve real-time and precise positioning of the end. Figure 2 The overall flow chart of the program is shown.

[0045] The flexible cable shape construction and end positioning method proposed in the present invention is applicable to cable structures with a certain degree of bending freedom, and can construct the spatial bending structure of the cable in real time. According to the anchor position coordinates of the starting end of the cable, the three-dimensional coordinates of any position on the cable are determined, including the estimation of the end position of the cable. This method can be used in scenarios such as buoy wet end positioning, underwater mooring anchor chain positioning, and towed sonar positioning. In this embodiment, towed sonar positioning is used as an example for introduction. Other scenarios are also calculated and applied in the same way.

[0046] This method obtains the posture of each node by distributing a certain number of 9-axis IMU (Inertial Measurement Unit) measurement units on the cable, constructs a cable gradient change model through a series of posture data, and finally reconstructs the overall spatial form according to the known cable length, and calculates the terminal position. The node refers to the sensor and its position, and the sensor has the measurement function of the relevant information of the position. Therefore, there are concepts of sensor node, measurement node, and position node in this article. In the present invention, the sensor adopts IMU measurement unit, and low precision is sufficient, so MEMS inertial device is adopted.

[0047] The specific implementation process of the method is as follows.

[0048] Assume that in the spatial coordinate system oxyz, the simplified model of the towed sonar cable is as follows Figure 3 As shown in the figure, the cable is released from the starting end P0 (x0, y0, z0). Under the action of gravity, ocean currents and buoyancy, it is generally in the shape of a catenary, and there will be some bending and swinging changes in the local horizontal direction. The cable changes are continuous, excluding deformations with large curvature. The total length of the cable released by the towed sonar is L, and there are n measurement nodes α distributed evenly on the cable. i , (i=1,2,…,n), the first measurement node α1 is set at p0, and the terminal node α is set at the end of the cable n The node spacing is d, and the cable length from each node to the initial position is l i =(i-1)d. The nodes are evenly spaced so that they can be measured evenly and the length can be calculated easily. If the distance between each node and the initial position is l i If it is known, then equal spacing is not necessary.

[0049] The node measures the acceleration f at the location through the IMU bi , angular increment Δθ bi and the magnetic vector m bi , by f bi and m bi The static posture of the node can be calculated, and the node α i The static posture of the posture matrix Indicates that the relationship is as follows:

[0050]

[0051] The superscript n represents the navigation coordinate system, and b represents the carrier coordinate system. g refers to the earth's gravity, m refers to the geomagnetic magnetic vector at that location, and the superscript n represents the projection in the n system. The principle of double vector attitude determination can be used to solve the node α i The posture matrix

[0052] For dynamic scenes, the attitude matrix needs to combine the misalignment angle and the angle increment Δθ bi Perform iterative updates.

[0053]

[0054] where φ bi is the horizontal misalignment angle, Represents the posture matrix The third row vector of . Get the misalignment angle calculated value φ bi After that, combined with the gyro output Δθ bi , which can be used to calculate the attitude matrix To update and correct, the numerical recursive algorithm is as follows:

[0055]

[0056] is the node α before correction i The posture matrix, is the modified node α i The posture matrix, I is the identity matrix, ()× represents the antisymmetric matrix transformation of the vector in the brackets.

[0057] Next, we predict the gradient. Define the length of the cable from the start to the end as the gradient direction, and λ as the unit gradient vector. At the node, the projection coordinate of λ in the b system is λ b Can be calibrated in advance. Figure 4 For example, λ is along the y-axis direction of the IMU, then:

[0058]

[0059] θ x and θ z It is a small angle error. In the present invention, the gradient direction of the cable is defined along the y-axis. After the IMU device is installed, a small deviation angle occurs between the coordinate system defined by the device and the coordinate system defined by the cable at that position.

[0060] According to the posture measured by the node, we can get:

[0061]

[0062] is the node posture matrix, λ n is the projection of the unit gradient vector λ in the n-system.

[0063] Let α1 = (0, 0, 0), α i =(x i ,y i ,z i ), P(x, y, z) is any point on the cable. For any time and any shape of continuous cable structure, its model can be expressed by a continuous function as follows:

[0064]

[0065] X(l) refers to the x-coordinate at any length l of the cable, Y(l) refers to the y-coordinate at any length l of the cable, and Z(l) refers to the z-coordinate at any length l of the cable. The first and second derivatives of this function are continuous, which conforms to the continuity characteristics of underwater cables. From the above formula, we can see that the coordinates of any point on the cable can be calculated using the cable length l. We only need to master the differential function of the cable structure-length, that is, the gradient change function Because according to the definition of λ, the change in coordinates caused by the change in unit length of the cable is the gradient, it can be seen that, Combined with formula (5), node α i The relationship between the gradient at and the gradient change function is as follows:

[0066]

[0067] λ ni , bi Refers to node α i The projection of the gradient at in the n system and the b system.

[0068] Node α i The gradient at can be calculated based on the measured value λ bi It is calculated that the gradient change function of the entire cable can be constructed by cubic spline interpolation as follows:

[0069]

[0070] in, and are the projections of the cable gradient function on the three coordinate axes, respectively. l∈[l1,l2] represents the cable between l1 and l2, that is, the section between the first node and the second node. The rest are analogous. δ=(δ i1 , δ i2 , δ i3 , δ i4 )、μ=(μi1 , μ i2 , μ i3 , μ i4 ) and ν=(v i1 , ν i2 , ν i3 , ν i4 ) are the interpolation parameters of each spline.

[0071] For a point P(x,y,z) at any length l on the cable, its coordinates can be obtained as:

[0072]

[0073] In the above formula, ρ is the length integral symbol.

[0074] To verify the feasibility and performance of the theory, the following simulation verification is carried out: A towed sonar cable model is constructed.

[0075]

[0076] In the simulation, the cable is set to be a catenary in the vertical direction, with a catenary coefficient of b = 3. In the horizontal direction, it is a multi-frequency sine superposition curve, with an amplitude parameter a = 0.2 and a frequency parameter f = 0.5π. The cable length L = 7. The structure of the underwater towed sonar cable and its upward and side view effects are shown in the figure. Figure 5 and Figure 6 As shown in the figure, the circles are nodes, which are approximately evenly distributed (with an interval of about 0.2), and the number of nodes n = 21. Considering that the positioning error is proportional to the cable length, the length unit is not specifically limited in this simulation.

[0077] First, in order to verify the feasibility of the algorithm, it is assumed that the node measurement accuracy is high and the attitude measurement error of each node is 0.1°. The distance between the terminal sonar installation position and the starting point is l = 6.37.

[0078] The cable gradient fitting function curve based on MEMS nodes is as follows Figure 7 As shown, Figure 7 (a), (b), and (c) show the gradient fitting of the three axes xyz respectively. The cubic spline interpolation has a good restoration effect in all directions. The error after the cable is fully constructed is as follows Figure 8 As shown in the figure, the cable shape construction based on the node posture has a good positioning effect, with an error of less than 0.02, which is about 0.135% of the rope length. In this experiment, the positioning error at both ends of the cable increases rapidly in the x direction. This is because the horizontal fluctuation is large in the cable shape setting, the gradient of the cable in the x direction changes dramatically, and the cubic spline interpolation has a slightly poor fit at both ends.

[0079] The number of nodes also affects the positioning accuracy. The more sampling nodes there are, the more realistic the constructed function is. However, considering the cost, the number of nodes is limited, so it is necessary to evaluate the impact of the number of nodes on positioning accuracy. Based on the above experiment, the number of measurement nodes was reduced from 21 to 11. The gradient prediction results are as follows: Fig. 9 As shown, (a), (b), and (c) correspond to the gradient prediction of the xyz axis respectively. Figure 7 In comparison, reducing the number of nodes has a significant impact on the gradient prediction, especially in the x direction, which has a large change. The interpolated result has a large deviation from the actual result. This also affects the shape construction of the cable, such as Fig.10 As shown, the average error has increased by 6 times.

[0080] If the number of measurement nodes is increased to 41, it is found that the gradient prediction and positioning estimation errors have not been significantly improved. Fig.11 The cable shape construction error under different numbers of nodes is compared. This shows that excessive pursuit of the number of nodes not only does not increase the cost, but also slows down the effect improvement. As long as the gradient function prediction is accurate, a good construction accuracy can be obtained, which requires that the number of nodes is greater than the number of extreme values ​​of gradient change and is evenly distributed in its characteristic position, so that the gradient change can be restored with the least number of nodes. In this simulation, n = 21 is more economical and effective.

[0081] Finally, we compare the impact of node IMU accuracy on measurement. The IMU of the measurement node usually uses cheap and compact MEMS sensors, so the attitude accuracy is not very high. The attitude accuracy of 0.1° mentioned above is usually difficult to achieve with MEMS, especially in terms of heading based on magnetometers. Conservatively estimated, the horizontal attitude error is set to 0.5°, the heading error is 5°, and the number of nodes is n=21.

[0082] The gradient prediction results and positioning estimation errors are as follows: Fig.12 and Fig.13 As shown, Fig.12 (a), (b), and (c) are the gradient predictions for the three axes xyz respectively. It can be seen that as the sensor accuracy decreases, the prediction error of the gradient function also increases, which in turn causes the cable positioning estimation to be inaccurate. The average error is 0.025, and the percentage is 0.383%, which is an order of magnitude worse than the high-precision state simulation. In particular, the error in the x direction is larger than that in the other two directions, and the gradient distortion in this direction is also more serious. This is caused by the insufficient heading accuracy of the magnetometer, while the attitude accuracy measured by the accelerometer on which the other two directions depend is slightly higher, so the error is smaller.

[0083] Four sets of simulation test comparisons under different precision IMUs Fig.14As shown in the figure, the accuracy of cable shape construction improves with the improvement of IMU accuracy. Even under the condition of 1° horizontal attitude error and 10° heading error, the average accuracy can still be better than 1%. This means that 21 low-precision sensors deployed on a 1km underwater cable can achieve meter-level positioning.

[0084] The present invention aims at the problem of uncertain underwater shape of mooring cables in applications such as buoys and towed platforms, and proposes a shape reconstruction and terminal positioning method based on gradient distribution prediction. The method can predict the gradient change of the flexible structure through low-cost MEMS sensors distributed on the cable, and then complete the shape reconstruction of the cable. This enables the displacement of the underwater mooring cable to be calculated in real time, without the need for complex solutions and expensive equipment. It provides an effective error compensation means for the self-positioning of underwater detection and positioning equipment. Comparative tests show that the method is feasible and can prepare to construct the shape of the cable that can be bent freely underwater, and discusses the influence of the number of devices and the accuracy of the devices on the final shape construction and terminal positioning. The results show that a certain number of node sensors (not too many) can solve the construction of most underwater cable shapes, and low-precision sensors can also achieve prediction and construction. The cable positioning error of 1k is only 18m, which can meet the use requirements of most scenarios. The method can solve industrial fields such as buoy sonar wet end positioning, towed sonar structure reconstruction, and underwater self-positioning of semi-floating weapons, and can also provide non-line-of-sight measurement solutions for non-underwater environments such as space measurement.

[0085] Based on the same technical concept as the method embodiment, the present invention also provides a flexible cable shape construction and end positioning system based on gradient distribution prediction, comprising:

[0086] A node attitude calculation module is used to obtain attitude data of each installation position based on the inertial measurement unit distributedly installed on the cable, and solve the attitude matrix of the position node based on the attitude data;

[0087] The gradient definition and conversion module is used to define the length direction of the cable from the starting end to the end as the gradient direction, λ is the unit gradient vector, that is, the coordinate change caused by the change of the unit length cable, according to the attitude matrix and the projection coordinate λ of the unit gradient vector λ in the carrier coordinate system b , get the projection coordinates of the unit gradient vector in the navigation coordinate system n represents the navigation coordinate system, b represents the carrier coordinate system;

[0088] The gradient change model building module is used to establish a continuous cable structure model of any shape according to the continuity characteristics of the cable, and express the coordinates of any point on the cable as a continuous function of the cable length l: Among them, X(l), Y(l), and Z(l) are the x-coordinate, y-coordinate, and z-coordinate of the cable at any length l, respectively. is the gradient change function. According to the definition of λ, the relationship between the unit gradient vector and the gradient change function is established.

[0089] The solution calculation module is used to predict the gradient change function of the cable through the cubic spline difference method, and then restore the underwater flexible shape by integrating the cable length according to the cable structure model, and locate each point on the cable and the end.

[0090] It should be understood that the flexible cable shape construction and end positioning system based on gradient distribution prediction in the embodiment of the present invention can realize all the technical solutions in the above-mentioned method embodiment, and the functions of its various functional modules can be specifically implemented according to the methods in the above-mentioned method embodiments. The specific implementation process can refer to the relevant description in the above-mentioned embodiments, which will not be repeated here.

[0091] The present invention also provides a computer device, comprising: one or more processors; a memory; and one or more programs, wherein the one or more programs are stored in the memory and are configured to be executed by the one or more processors, and when the programs are executed by the processors, the steps of the flexible cable shape construction and end positioning method based on gradient distribution prediction as described above are implemented.

[0092] The present invention also provides a computer-readable storage medium having a computer program stored thereon, characterized in that when the computer program is executed by a processor, the steps of the flexible cable shape construction and end positioning method based on gradient distribution prediction as described above are implemented.

[0093] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, devices (systems), computer equipment or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0094] The present invention is described with reference to a flowchart of a method according to an embodiment of the present invention. It should be understood that each process in the flowchart and a combination of processes in the flowchart can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the process in the flowchart. Figure 1A device that specifies functions in a process or multiple processes.

[0095] These computer program instructions may also be stored in a computer readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture including an instruction device, which implements the process Figure 1 A function specified in a process or multiple processes.

[0096] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 The steps of a specified function in a process or multiple processes.

Claims

1. A method for constructing a flexible cable shape and locating its end based on gradient distribution prediction, characterized in that: The following steps are involved: Acquire attitude data of each installation position based on an inertial measurement unit distributedly installed on the cable, and solve the attitude matrix of the position node based on the attitude data; The length direction of the cable from the starting end to the end is defined as the gradient direction, and λ is the unit gradient vector, that is, the coordinate change caused by the change of the unit length cable. According to the attitude matrix and the projection coordinate λ of the unit gradient vector λ in the carrier coordinate system b , get the projection coordinates of the unit gradient vector in the navigation coordinate system n represents the navigation coordinate system, b represents the carrier coordinate system; According to the continuity characteristics of the cable, a continuous cable structure model of arbitrary shape is established, and the coordinates of any point on the cable are expressed as a continuous function of the cable length l: Among them, X(l), Y(l), and Z(l) are the x-coordinate, y-coordinate, and z-coordinate of the cable at any length l, respectively. is the gradient change function. According to the definition of λ, the relationship between the unit gradient vector and the gradient change function is established. The gradient variation function of the cable is predicted by the cubic spline difference method, and then the underwater flexible shape is restored by integrating the cable length according to the cable structure model, and each point on the cable and the end are located.

2. The method according to claim 1, characterized in that The method comprises: obtaining attitude data of each installation position based on an inertial measurement unit distributedly installed on the cable, and solving an attitude matrix of the position node based on the attitude data, including: Get the acceleration f of the inertial measurement unit installation location bi , angular increment Δθ bi and magnetic vector m bi , by f bi and m bi Calculate the static posture of the position node, node α i The posture matrix is ​​expressed as Then we have: Where g refers to the Earth's gravity, m refers to the geomagnetic magnetic vector at that location, and the superscript n of g and m refers to the projection in the n-system; Using the dual vector pose determination principle to solve the node α i Posture The node α is calculated according to the following formula i The horizontal misalignment angle φ in the b system bi : in Represents the posture matrix The third row vector of ; Get the calculated value of misalignment angle φ bi After that, combined with the gyro output Δλ bi , to calculate the attitude matrix Updates and corrections: in, Refers to the corrected attitude matrix, I is the identity matrix, ()× represents the antisymmetric matrix transformation of the vector in the brackets.

3. The method according to claim 1, characterized in that The unit gradient vector θ is calibrated into the projection coordinate θ in the carrier coordinate system b It is expressed as: Where θ x and θ z Represents the angular error between the coordinate systems on the x-axis and z-axis.

4. The method according to claim 1, characterized in that: The gradient variation function of the cable is predicted by the cubic spline difference method, including: in, and are the projections of the cable gradient change function on the three coordinate axes, δ=(δ i1 ,δ i2 ,δ i3 ,δ i4 )、μ=(μ i1 ,μ i2 ,μ i3 ,μ i4 ) and v=(v i1 ,v i2 ,v i3 ,v i4 ) are the interpolation parameters of each spline.

5. The method according to claim 4, characterized in that The underwater flexible shape is restored based on the integral of the cable length, including: For a point P(x,y,z) at any length l on the cable, its coordinates are: Where x0, y0, z0 are the coordinates of the starting end of the cable, and ρ is the length integral symbol.

6. The method according to claim 1, characterized in that The inertial measurement units installed in a distributed manner on the cable use accelerometers and gyroscopes composed of MEMS sensors.

7. The method according to claim 1, characterized in that The i-th position node α on the cable i The relationship between the unit gradient vector at and the gradient change function is as follows: λ ni , bi is node α i The projection of the unit gradient vector at in the n system and the b system.

8. A flexible cable shape construction and terminal positioning system based on gradient distribution prediction, characterized in that: include: A node attitude calculation module is used to obtain attitude data of each installation position based on the inertial measurement unit distributedly installed on the cable, and solve the attitude matrix of the position node based on the attitude data; The gradient definition and conversion module is used to define the length direction of the cable from the starting end to the end as the gradient direction, λ is the unit gradient vector, that is, the coordinate change caused by the change of the unit length cable, according to the attitude matrix and the projection coordinate λ of the unit gradient vector λ in the carrier coordinate system b , get the projection coordinates of the unit gradient vector in the navigation coordinate system n represents the navigation coordinate system, b represents the carrier coordinate system; The gradient change model building module is used to establish a continuous cable structure model of any shape according to the continuity characteristics of the cable, and express the coordinates of any point on the cable as a continuous function of the cable length l: Among them, X(l), Y(l), and Z(l) are the x-coordinate, y-coordinate, and z-coordinate of the cable at any length l, respectively. is the gradient change function. According to the definition of λ, the relationship between the unit gradient vector and the gradient change function is established. The solution calculation module is used to predict the gradient change function of the cable through the cubic spline difference method, and then restore the underwater flexible shape by integrating the cable length according to the cable structure model, and locate each point on the cable and the end.

9. A computer device, characterized in that: include: one or more processors; Memory; And one or more programs, wherein the one or more programs are stored in the memory and are configured to be executed by the one or more processors, and when the programs are executed by the processors, the steps of the flexible cable shape construction and end positioning method based on gradient distribution prediction are implemented as described in any one of claims 1-7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method for flexible cable shape construction and terminal positioning based on gradient distribution prediction are implemented as described in any one of claims 1 to 7.

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