Three-dimensional curve reconstruction method and towed formation detection system based on shape perception

Abstract

The present invention provides a three-dimensional curve reconstruction method and a shape-aware drag array detection system. The method includes: arranging multiple sensing units circumferentially around the central axis of a test object, wherein each sensing unit bends as the test object bends, and for each sensing unit, the angle between the radial line corresponding to the sensing unit and the X-axis on each cross section is the same; for each sensing unit on the cross section of the test object, determining the distance from the sensing unit to the bending neutral plane based on the angle between the radial line corresponding to the sensing unit and the X-axis and the angle between the bending direction of the cross section and the X-axis; determining the total curvature vector of the test object based on the strain detected by each sensing unit and the determined distance; determining the torsion and curvature of the test object in the bending tangent direction based on the total curvature vector; determining the unit tangent vector of the test object in the bending tangent direction based on the torsion and curvature; and integrating the unit tangent vector to reconstruct the three-dimensional curve of the test object. The three-dimensional reconstruction method of the present invention is simple, efficient, and highly accurate.

Description

Technical Field

[0001] The present invention belongs to the field of curve reconstruction, and in particular relates to a three-dimensional curve reconstruction method and a drag formation detection system based on shape perception. Background Art

[0002] Marine resources are crucial to the sustainable development of national economies and military security, and as a result, countries are paying more attention to marine resource exploration than ever before. Underwater long-range target detection relies on the perception of underwater acoustic signals, and hydrophones, as key components, play a vital role in ocean exploration and target analysis.

[0003] In practical applications, it is generally assumed that the array remains horizontal during motion. However, during the towing process, the array may bend or shake due to fluid resistance or the array's own structure, affecting detection performance. Therefore, the array's posture cannot be simply considered a straight line. How to effectively measure the array's formation is the key to improving the detection performance and accuracy of towed arrays.

[0004] Currently available methods for measuring towed array formations mainly include acoustic estimation methods and non-acoustic spatial coordinate measurement methods. The acoustic method relies on an external auxiliary sound source and performs corresponding processing based on the signals received by the fiber optic hydrophone to calculate the formation; the non-acoustic method requires the use of other sensors to measure key coordinate parameters in the space or to perform mechanical analysis on the array to achieve the measurement purpose. The above methods require external equipment to assist in the measurement, and the incident direction of the sound source and the position information of the sensor in space must be known. They are suitable for applications where the array is fixed. However, the position of the towed array in actual work changes at any time, which brings certain difficulties to the above measurement methods and affects the accurate measurement of the formation.

[0005] In reality, there are many other 3D shape measurement methods available today. However, due to the random variations in the external environment acting on the towed array, these methods offer lower accuracy than the two aforementioned methods. Therefore, when the object under test is placed in a randomly changing external environment, current 3D shape measurement methods rely on external equipment and suffer from lower measurement accuracy. Summary of the Invention

[0006] The present invention provides a three-dimensional curve reconstruction method and a drag array detection system based on shape perception to solve the current problem that when the object to be measured is applied to a scene with randomly changing external environment, the three-dimensional shape measurement of the object to be measured requires the help of external equipment and the measurement accuracy is low.

[0007] According to a first aspect of an embodiment of the present invention, a three-dimensional curve reconstruction method is provided, comprising:

[0008] Step S100: Arrange multiple sensing units for detecting strain magnitude circumferentially around the central axis of the object to be measured. Each sensing unit is aligned with both ends of the object to be measured and bends as the object to be measured bends. An X-axis and a Y-axis are provided on the cross section of the object to be measured. The origin of the XY axis is on the central axis of the object to be measured. For each sensing unit, the angle α between the radial line corresponding to the sensing unit on each cross section and the X-axis is i The same, i is the number of the sensing unit and is an integer greater than 0; for the corresponding cross section of the object under test at point s, let the angle between the bending direction corresponding to the cross section and the X-axis be θ(s), the plane perpendicular to the bending direction and passing through the central axis of the object under test be the bending neutral plane, and s be the distance from one end of the object under test and can be an arbitrary value;

[0009] Step S200: for each sensor unit on the cross section, according to the angle α between the radial line corresponding to the sensor unit and the X axis i , the angle θ(s) between the bending direction and the X axis, and the distance d from the central axis of the sensing unit to the neutral plane of the bending i (s);

[0010] Step S300: According to the strain magnitude ε detected by each sensing unit at position s i (s), the distance d from the central axis of each sensor unit to the bending neutral plane i (s), determine the total curvature vector K(s) of the object under test at point s;

[0011] Step S400: Calculate the components K of the total curvature vector K(s) of the object under test on the X-axis and Y-axis at position s. x (s) and K y (s), determine the angle θ(s) between the bending direction and the X-axis, thereby determining the torsion τ(s) of the object to be measured; determine the curvature κ(s) of the object to be measured in the bending tangent direction according to the total curvature vector K(s) of the object to be measured at point s;

[0012] Step S500: Determine the unit tangent vector T(s) of the object under test in the direction of the curved tangent line based on the torsion τ(s) and curvature K(s) of the object under test; integrate the unit tangent vector T(s) of the object under test in the direction of the curved tangent line to reconstruct the three-dimensional curve r(s) of the central axis of the object under test.

[0013] In an optional implementation, in step S200, the distance d from the central axis of the sensing unit to the bending neutral plane is determined according to the following formula: i (s):d i (s)=L*cos[α i-θ(s)], where L represents the distance between the central axis of the object to be measured and the central axis of each sensing unit.

[0014] In another optional implementation, in step S300, the total curvature vector K(s) of the object to be tested at position s is determined according to the following formula:

[0015]

[0016] Where N represents the number of sensor units and is an integer greater than 1. and Represent the unit vectors of the X-axis and Y-axis respectively.

[0017] In another optional implementation, in step S400, the angle θ(s) between the bending direction and the X-axis is determined according to the following formula:

[0018]

[0019] According to the formula: τ(s) = θ′(s), determine the torsion τ(s) of the object to be measured, where θ′(s) is the derivative of θ(s);

[0020] According to the formula: Determine the curvature κ(s) of the object under test in the bending tangent direction.

[0021] In another optional implementation, in step S500, a Frenet-Serret framework is established according to the following formula to determine the unit tangent vector T(s) of the object under test in the direction of the curved tangent line:

[0022]

[0023] Wherein N(s) is the principal normal vector, which points to the corresponding bending direction on the cross section, B(s) is the secondary normal vector, which is perpendicular to the bending direction on the cross section and intersects the central axis, and the origin of the three-dimensional coordinate system composed of T(s), N(s) and B(s) is on the central axis of the object to be measured;

[0024] According to the following formula, the unit tangent vector T(s) of the object under test in the direction of the curved tangent is integrated to reconstruct the three-dimensional curve r(s) of the central axis of the object under test:

[0025]

[0026] In another optional implementation, the sensing units in step S100 are evenly distributed around the central axis of the object to be measured;

[0027] For each sensor unit, the angle α between the radial line corresponding to the sensor unit on each cross section and the positive direction of the X axis isi The same; the angle between the bending direction of the cross section and the positive direction of the X axis is θ(s);

[0028] The sensing unit is an optical fiber arranged in parallel with the object to be measured, and the method is used in the case where the object to be measured is affected by an external environment and the acting force varies randomly.

[0029] According to a second aspect of an embodiment of the present invention, a shape-perceiving-based towed array detection system is provided, comprising a towed array structure, a strain measurement device, and a processor, wherein the towed array structure comprises a towed array and a plurality of sensing units, wherein the plurality of sensing units are circumferentially arranged around a central axis of the towed array and fixedly connected to the towed array, wherein each sensing unit is connected to the strain measurement device, which is connected to the processor, and the processor uses the above-mentioned three-dimensional curve reconstruction method to reconstruct a three-dimensional curve of the towed array based on the strain magnitude at different positions on each sensing unit detected by the strain measurement device, thereby monitoring the shape of the towed array.

[0030] In an optional implementation, the towed array structure also includes an outer sheath and a support rope, and the towed array, each sensing unit and the support rope all run parallel across the outer sheath, the support rope is located between the towed array and the outer sheath, and the towed array and each sensing unit are spaced apart from the outer sheath.

[0031] In another optional implementation, the towed array is composed of a plurality of sensor element skeletons, and the sensor element skeletons are arranged at intervals along the central axis of the towed array; and the towed array is a hydrophone array.

[0032] In another optional implementation, the sensing unit is an optical fiber.

[0033] The beneficial effects of the present invention are:

[0034] 1. The present invention introduces an XY axis coordinate system, and for each sensor unit, the angle α between the radial line corresponding to the sensor unit on each cross section of the object to be measured and the X axis is i The angle θ(s) between the bending direction and the X-axis is fixed regardless of the cross section. The angle θ(s) between the bending direction and the X-axis is determined not by establishing a motion equation and the corresponding relationship between the strain detected by a single sensing unit and θ(s). Instead, the angle α between the radial line of the sensing unit and the X-axis is first determined. i , the angle θ(s) between the bending direction and the X axis, and the distance d from the central axis of the sensing unit to the neutral plane of the bending i (s), and then according to the strain size ε detected by each sensing unit at s i(s), the distance d from the central axis of each sensor unit to the bending neutral plane i (s), determine the total curvature vector K(s) of the object to be tested at s, and finally calculate the components K of the total curvature vector K(s) of the object to be tested on the X-axis and Y-axis according to the components K x (s) and K y (s), determine the angle θ(s) between the bending direction and the X axis, where the distance d i (s) is determined based on the geometric relationship, and its calculation results include θ(s). The calculation of the total curvature vector K(s) depends on the distance d i (s), so the total curvature vector K(s) also includes the unknown parameter θ(s). So far, θ(s) and component K x (s) and K y (s), θ(s) can be calculated. The θ(s) calculation method of the present invention is particularly suitable for situations where the external environment of the object to be measured changes randomly, ensuring the accuracy of the calculation of θ(s) in this situation. In addition, the present invention takes into account the strain detected by all sensing units when determining the total curvature vector K(s). Therefore, the accuracy of θ(s), torsion τ(s), and curvature κ(s) determined according to K(s) is higher. The three-dimensional curve of the object to be measured reconstructed based on torsion τ(s) and curvature κ(s) can more accurately reflect the shape of the object to be measured.

[0035] The present invention does not require the assistance of external sound sources or sensors when reconstructing three-dimensional curves, relying solely on sensing units and specific algorithms. This greatly simplifies the working mechanism of the object under test and its shape measurement structure, reducing the cost and complexity of the reconstruction system. Furthermore, the present invention's three-dimensional reconstruction method is simple and efficient. Furthermore, the present invention takes into account the situation where the object under test is affected by the external environment and the forces acting on it vary randomly. Even in this situation, the accuracy of the object's shape reconstruction result is higher.

[0036] 2. The present invention designs a calculation formula for the total curvature vector K(s). By increasing the number N, the calculation error of θ(s) caused by the differential influence of the external environment on the sensing unit can be reduced. While improving the calculation accuracy of θ(s), the accuracy of three-dimensional curve reconstruction can be improved.

[0037] 3. The shape-sensing towed array detection system of the present invention eliminates reliance on external equipment and does not require the assistance of external sound sources or sensors. It relies solely on optical fibers and specific algorithms, greatly simplifying the towed array shape monitoring structure and operating mechanism, reducing system cost and complexity. The present invention can accurately calculate the real-time underwater posture of the towed array, providing efficient and precise posture sensing capabilities. The present invention effectively solves the difficulties faced by traditional towed array posture measurement, is unaffected by changes in the towed array's position, and improves detection performance and measurement accuracy. Because the present invention can more accurately and efficiently measure the shape of the towed array, the measured shape can be used to correct the towed array's detection performance, compensating for the impact of changes in the optical cable shape on its detection performance.

[0038] 4. The present invention uses optical fiber as the sensing unit, which can further simplify the towed array shape monitoring structure, so that the towed array of the hydrophone, for example, can be developed towards full fiberization. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a flow chart of an embodiment of the three-dimensional curve reconstruction method of the present invention;

[0040] Figure 2 This is a schematic diagram of the principle of three-dimensional curve reconstruction of the present invention;

[0041] Figure 3 (a) to (c) are schematic diagrams for determining the distances from the central axes of the three sensing units to the neutral plane of the bending;

[0042] Figure 4 (a) to (c) are schematic diagrams of the three-dimensional curve reconstruction results of the present invention;

[0043] Figure 5 1 is a schematic structural diagram of an embodiment of a towed array detection system based on shape perception according to the present invention;

[0044] Figure 6 This is a front view of the structure of an embodiment of the towed array structure of the present invention;

[0045] Figure 7 yes Figure 6 side view. DETAILED DESCRIPTION

[0046] In order to enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention and to make the above-mentioned purposes, features and advantages of the embodiments of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0047] In the description of the present invention, unless otherwise specified and limited, it should be noted that the term "connection" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the internal connection between two elements. It can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meaning of the above terms can be understood according to the specific circumstances.

[0048] See also Figure 1 , is a flow chart of an embodiment of the three-dimensional curve reconstruction method of the present invention. Figure 2 As shown, the three-dimensional curve reconstruction method may include the following steps:

[0049] Step S100: Arrange multiple sensing units for detecting strain magnitude circumferentially around the central axis of the object to be measured. Each sensing unit is aligned with both ends of the object to be measured and bends as the object to be measured bends. An X-axis and a Y-axis are provided on the cross section of the object to be measured. The origin of the XY axis is on the central axis of the object to be measured. For each sensing unit, the angle α between the radial line corresponding to the sensing unit on each cross section and the X-axis is i The same, i is the number of the sensor unit and is an integer greater than 0; for the corresponding cross section of the object under test at point s, let the angle between the bending direction corresponding to the cross section and the X-axis be θ(s), the plane perpendicular to the bending direction and passing through the central axis of the object under test be the bending neutral plane, and s is the distance from one end of the object under test and can be an arbitrary value. The present invention can regard the object under test as a spatial curve, and the parametric equation of the airborne curve with an arc length of s can be r(s) = x(s)i + y(s)j + z(s)k.

[0050] In step S100, the sensing units are evenly distributed around the central axis of the object to be measured; for each sensing unit, the angle α between the radial line corresponding to the sensing unit on each cross section and the positive direction of the X axis (or the negative direction of the X axis) is i The same; the angle between the bending direction corresponding to the cross section and the positive direction of the X-axis (or the negative direction of the X-axis) is θ(s). The angle between the radial line corresponding to the sensing unit and the X-axis can be: the angle between the straight line intersecting the central axis of the sensing unit and the central axis of the object to be measured on the corresponding cross section of the object to be measured and the X-axis. The sensing unit can be an optical fiber (such as a distributed single-mode optical fiber) arranged parallel to the object to be measured and the number thereof can be three, the three optical fibers are uniformly arranged around the central axis of the object to be measured, and the angle between adjacent optical fibers is 120°. The method of the present invention is particularly suitable for situations where the object to be measured is affected by the external environment and the force varies randomly.

[0051] Step S200: for each sensor unit on the cross section, according to the angle α between the radial line corresponding to the sensor unit and the X axis i , the angle θ(s) between the bending direction and the X axis, and the distance d from the central axis of the sensing unit to the neutral plane of the bendingi (s).

[0052] Combine Figure 3 As shown in (a) to (c), for the first sensing unit, d1(s) = L*sin[α1-(90°-θ(s)] = L*cos[α1-θ(s)]; for the second sensing unit, d2(s) = L*sin[90°-(θ(s)-α2)] = L*cos[θ(s)-α2]; for the third sensing unit, d3(s) = L*sin[90°-(α3-θ(s))] = L*cos[α3-θ(s)]. It can be seen that the distance d from the central axis of the sensing unit to the bending neutral plane can be determined according to the following formula i (s):

[0053] d i (s)=L*cos[α i -θ(s)], where L represents the distance between the central axis of the object to be measured and the central axis of each sensing unit.

[0054] Step S300: According to the strain magnitude ε detected by each sensing unit at position s i (s), the distance d from the central axis of each sensor unit to the bending neutral plane i (s), determine the total curvature vector K(s) of the object under test at position s. In step S300, the total curvature vector K(s) of the object under test at position s can be determined according to the following formula:

[0055]

[0056] Where N represents the number of sensor units and is an integer greater than 1. and Represent the unit vectors of the X-axis and Y-axis respectively. For example, N=3.

[0057] Step S400: Calculate the components K of the total curvature vector K(s) of the object under test on the X-axis and Y-axis at position s. x (s) and K y (s), determine the angle θ(s) between the bending direction and the X-axis, thereby determining the torsion τ(s) of the object to be measured; and determine the curvature κ(s) of the object to be measured in the bending tangent direction based on the total curvature vector K(s) of the object to be measured at point s.

[0058] In step S400, the angle θ(s) between the bending direction and the X-axis may be determined according to the following formula: || is the modulo operator; the torsion τ(s) of the object to be measured can be determined according to the formula: τ(s) = θ′(s), where θ′(s) is the derivative of θ(s); the torsion τ(s) of the object to be measured can be determined according to the formula: Determine the curvature K(s) of the object to be measured in the direction of the bending tangent. When calculating the total curvature vector K(s), the present invention first calculates the stress ε measured by each sensing unit at s. i (s) and corresponding d i (s) is divided, and the result is then multiplied by cosα i , obtain the X-axis component of the sensor unit, and multiply the result by sinα i , obtain the Y-axis component of the sensing unit, the component K of the total curvature vector K(s) on the X-axis x (s) is the sum of the X-axis components of all sensor units, and the component K on the Y-axis y (s) is the sum of the Y-axis components of all sensing units, and It can be seen that the present invention designs the calculation formula of the total curvature vector K(s). By increasing the number N, the calculation error of θ(s) caused by the differential influence of the external environment on the sensing unit can be reduced. On the premise of improving the calculation accuracy of θ(s), the accuracy of three-dimensional curve reconstruction can be improved.

[0059] Step S500: Determine the unit tangent vector T(s) of the object under test in the direction of the curved tangent line based on the torsion τ(s) and curvature κ(s) of the object under test; integrate the unit tangent vector T(s) of the object under test in the direction of the curved tangent line to reconstruct the three-dimensional curve r(s) of the central axis of the object under test.

[0060] In step S500, a Frenet-Serret framework may be established according to the following formula to determine the unit tangent vector T(s) of the object under test in the direction of the curved tangent line:

[0061]

[0062] Where N(s) is the principal normal vector, which points to the corresponding bending direction on the cross section; B(s) is the binormal vector, which is perpendicular to the bending direction on the cross section and intersects the central axis; the origin of the three-dimensional coordinate system composed of T(s), N(s) and B(s) is on the central axis of the object to be measured, and the three are orthogonal to each other and form a right-handed coordinate system; the rate of change of the unit tangent vector T(s) is the curvature K(s), and the rotation rate of the binormal vector B(s) is the torsion τ(s).

[0063] In step S500, the unit tangent vector T(s) of the object under test in the direction of the curved tangent line may be integrated according to the following formula to reconstruct the three-dimensional curve r(s) of the central axis of the object under test:

[0064]

[0065] According to the definition of calculus, when a variable is infinitely small, the derivative f′(x) of the function f(x) can be expressed as:

[0066]

[0067] Therefore, according to the above definition, the Frenet-Serret equation can be transformed into:

[0068]

[0069] Substituting the initial conditions T(0)=(1,0,0), N(0)=(0,1,0), B(0)=(0,0,1), r(0)=(0,0,0), κ(0)=(0), and τ(0)=(0) when s=0, we can obtain the unit tangent vector T, principal normal vector N, binormal vector B and coordinate position information of the space curve at each position. Finally, we only need to integrate T(s) to restore the three-dimensional shape of the space curve.

[0070] Existing three-dimensional reconstruction methods also involve first determining the torsion τ(s) and curvature K(s) of the object to be measured, then determining the unit tangent vector T(s) of the object to be measured in the direction of the bending tangent based on the torsion τ(s) and curvature K(s); integrating the unit tangent vector T(s) of the object to be measured in the direction of the bending tangent to reconstruct the three-dimensional curve of the object to be measured. However, this method is only applicable when the external environment of the object to be measured is fixed and the external environmental influences on each sensing unit are the same. Specifically, in this case, taking three sensing units as an example, the motion equation is established, and the strain detected by each sensing unit can be expressed as:

[0071]

[0072] in L represents the distance between the central axis of the object to be measured and the central axis of each sensor unit, ρ represents the curvature radius of the object to be measured when it is bent, Δε max is the maximum strain when the distance between the central axis of the sensing unit and the neutral plane of the bending is L, and α1, α2 and α3 are the angles between the radial lines corresponding to the three sensing units and the positive direction of the X axis. As can be seen from the above formula, the magnitude of each strain is determined by Δε max , corresponding to the angle α i The angle θ is determined by the three parameters θ and θ. Since the values ​​of these three parameters are fixed, when each sensing unit is affected by the object to be measured and other external environments, the above formula is obviously not valid, and the angle θ cannot be directly determined by the above formula.

[0073] As can be seen from the above embodiments, the present invention introduces an XY axis coordinate system, and for each sensing unit, the angle α between the radial line corresponding to the sensing unit on each cross section of the object to be measured and the X axis isi The angle θ(s) between the bending direction and the X-axis is fixed regardless of the cross section. The angle θ(s) between the bending direction and the X-axis is determined not by establishing a motion equation and the corresponding relationship between the strain detected by a single sensing unit and θ(s). Instead, the angle α between the radial line of the sensing unit and the X-axis is first determined. i , the angle θ(s) between the bending direction and the X axis, and the distance d from the central axis of the sensing unit to the neutral plane of the bending i (s), and then according to the strain size ε detected by each sensing unit at s i (s), the distance d from the central axis of each sensor unit to the bending neutral plane i (s), determine the total curvature vector K(s) of the object to be tested at s, and finally calculate the components K of the total curvature vector K(s) of the object to be tested on the X-axis and Y-axis according to the components K x (s) and K y (s), determine the angle θ(s) between the bending direction and the X axis, where the distance d i (s) is determined based on the geometric relationship, and its calculation results include θ(s). The calculation of the total curvature vector K(s) depends on the distance d i (s), so the total curvature vector K(s) also includes the unknown parameter θ(s). So far, θ(s) and component K x (s) and K y (s), θ(s) can be calculated. The θ(s) calculation method of the present invention is particularly suitable for situations where the external environment of the object to be measured changes randomly, and ensures the calculation accuracy of θ(s) in this situation. In addition, the present invention takes into account the strain detected by all sensing units when determining the total curvature vector K(s). Therefore, the accuracy of θ(s), torsion τ(s) and curvature κ(s) determined according to K(s) is higher, and the three-dimensional curve of the object to be measured reconstructed according to the torsion τ(s) and the curvature K(s) can more accurately reflect the shape of the object to be measured.

[0074] The present invention does not require the assistance of external sound sources or sensors when reconstructing three-dimensional curves. It only relies on sensing units and specific algorithms, which greatly simplifies the working mechanism of the object to be measured and its shape measurement structure, reduces the cost and complexity of the reconstruction system, and the three-dimensional reconstruction method of the present invention is simple and efficient. In addition, the present invention takes into account the situation where the object to be measured is affected by the external environment and the force changes randomly. Even in this case, the accuracy of the shape reconstruction result of the object to be measured is higher. The result of three-dimensional curve reconstruction is as follows: Figure 4 As shown, Figure 4 (a) shows the original data (i.e., wavelength drift of three optical fibers), Figure 4In (b) and (c), the solid line represents the three-dimensional shape of the object when it is bent, while the dotted line represents the shape of the object when it is horizontal. It can be seen from the figure that the reconstruction result is consistent with the actual shape.

[0075] See also Figure 5 , is a schematic diagram of an embodiment of a towed array detection system based on shape perception of the present invention. The towed array detection system based on shape perception may include a towed array structure, a strain measurement device and a processor, combined with Figure 6 and 7 As shown, the towed array structure may include a towed array 1 and a plurality of sensing units 2, wherein the plurality of sensing units 2 are circumferentially arranged around the central axis of the towed array 1 and are fixedly connected to the towed array 1, and each sensing unit 2 is connected to the strain measuring device, and the strain measuring device is connected to the processor. The processor reconstructs a three-dimensional curve of the towed array using the above-mentioned three-dimensional curve reconstruction method according to the strain magnitude at different positions on each sensing unit 2 detected by the strain measuring device, thereby monitoring the morphology of the towed array.

[0076] The towed array structure may further include an outer sheath 3 and a support rope 4. The towed array 1, each sensor unit 2, and the support rope 4 are all arranged parallel and transversely within the outer sheath 3. The support rope 4 is located between the towed array 1 and the outer sheath 3, and the towed array 1 and each sensor unit 2 are spaced apart from the outer sheath 3. The towed array 1 may be composed of a plurality of sensor element skeletons, each of which is spaced apart along the central axis of the towed array 1; the towed array 1 may be a hydrophone array. The sensor units 2 may be single-mode optical fibers with bending resistance, the sensor element skeletons may have tensile strength in the axial direction, and the axial length of each sensor element skeleton may be 82 mm. The support rope may be a Kevlar fiber rope, and the outer sheath may be a PU sheath made of polyurethane. Each sensing element skeleton is secured to its corresponding segment of the sensing unit at both ends along its axis using resin glue 5. To prevent the sensing units from breaking due to excessive tension, some redundancy can exist between adjacent sensing element skeletons. Furthermore, the towed array is normally flexible, with its natural length being shorter than when towing is obstructed. To ensure that the sensing units remain straight during towing, they can exhibit a slight wavy curve in their natural state. The sensing units can be optical fibers. Using optical fibers as sensing units in the present invention further simplifies the towed array shape monitoring structure, enabling the development of fully fiberized towed arrays, such as hydrophones.

[0077] As can be seen from the above embodiments, the shape-sensing towed array detection system of the present invention eliminates the dependence on external equipment, does not require the assistance of external sound sources or sensors, and only relies on optical fibers and specific algorithms, which greatly simplifies the towed array shape monitoring structure and working mechanism, and reduces system cost and complexity; the present invention can accurately calculate the real-time posture of the towed array underwater, and provides efficient and accurate posture perception capabilities; the present invention effectively solves the difficulties faced by traditional towed array posture measurement, is not affected by changes in the position of the towed array, and improves detection performance and measurement accuracy; because the present invention can measure the shape of the towed array more accurately and efficiently, the measured shape is used to correct the detection performance of the towed array, which can compensate for the influence of the shape change of the optical cable on its detection performance.

[0078] Other embodiments of the present invention will readily occur to those skilled in the art after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims.

[0079] It will be appreciated that the present invention is not limited to the precise construction that has been described above and shown in the accompanying drawings, and that various modifications and variations can be made without departing from its scope, which is governed solely by the appended claims.

Claims

1. A three-dimensional curve reconstruction method, characterized in that: include: Step S100: Arrange multiple sensing units for detecting strain magnitude circumferentially around the central axis of the object to be measured. Each sensing unit is aligned with both ends of the object to be measured and bends as the object to be measured bends. An X-axis and a Y-axis are provided on the cross section of the object to be measured. The origin of the XY axis is on the central axis of the object to be measured. For each sensing unit, the angle α between the radial line corresponding to the sensing unit on each cross section and the X-axis is i The same, i is the number of the sensing unit and is an integer greater than 0; for the corresponding cross section of the object under test at point s, let the angle between the bending direction corresponding to the cross section and the X-axis be θ(s), the plane perpendicular to the bending direction and passing through the central axis of the object under test be the bending neutral plane, and s be the distance from one end of the object under test and can be an arbitrary value; Step S200: for each sensor unit on the cross section, according to the angle α between the radial line corresponding to the sensor unit and the X axis i , the angle θ(s) between the bending direction and the X axis, and the distance d from the central axis of the sensing unit to the neutral plane of the bending i (s); Step S300: According to the strain magnitude ε detected by each sensing unit at position s i (s), the distance d from the central axis of each sensor unit to the bending neutral plane i (s), determine the total curvature vector K(s) of the object under test at point s; Step S400: Calculate the components K of the total curvature vector K(s) of the object under test on the X-axis and Y-axis at position s. x (s) and K y (s), determine the angle θ(s) between the bending direction and the X-axis, thereby determining the torsion τ(s) of the object to be measured; determine the curvature κ(s) of the object to be measured in the bending tangent direction according to the total curvature vector K(s) of the object to be measured at point s; Step S500: Determine the unit tangent vector T(s) of the object under test in the direction of the curved tangent line based on the torsion τ(s) and curvature κ(s) of the object under test; integrate the unit tangent vector T(s) of the object under test in the direction of the curved tangent line to reconstruct the three-dimensional curve r(s) of the central axis of the object under test.

2. The three-dimensional curve reconstruction method according to claim 1, characterized in that: In step S200, the distance d from the central axis of the sensor unit to the bending neutral plane is determined according to the following formula: i (s):d i (s)=L*cos[α i -θ(s)], where L represents the distance between the central axis of the object to be measured and the central axis of each sensing unit.

3. The three-dimensional curve reconstruction method according to claim 1, characterized in that: In step S300, the total curvature vector K(s) of the object under test at position s is determined according to the following formula: Where N represents the number of sensor units and is an integer greater than 1. and Represent the unit vectors of the X-axis and Y-axis respectively.

4. The three-dimensional curve reconstruction method according to claim 3, characterized in that: In step S400, the angle θ(s) between the bending direction and the X-axis is determined according to the following formula: According to the formula: τ(s) = θ′(s), determine the torsion τ(s) of the object to be measured, where θ′(s) is the derivative of θ(s); According to the formula: Determine the curvature κ(s) of the object under test in the bending tangent direction.

5. The three-dimensional curve reconstruction method according to claim 4, characterized in that: In step S500, a Frenet-Serret framework is established according to the following formula to determine the unit tangent vector T(s) of the object under test in the direction of the curved tangent line: Wherein N(s) is the principal normal vector, which points to the corresponding bending direction on the cross section, B(s) is the secondary normal vector, which is perpendicular to the bending direction on the cross section and intersects the central axis, and the origin of the three-dimensional coordinate system composed of T(s), N(s) and B(s) is on the central axis of the object to be measured; According to the following formula, the unit tangent vector T(s) of the object under test in the direction of the bending tangent is integrated to reconstruct the three-dimensional curve r(S) of the central axis of the object under test:

6. The three-dimensional curve reconstruction method according to claim 1, characterized in that: In step S100, the sensing units are evenly distributed around the central axis of the object to be measured; For each sensor unit, the angle α between the radial line corresponding to the sensor unit on each cross section and the positive direction of the X axis is i The same; the angle between the bending direction of the cross section and the positive direction of the X axis is θ(S); The sensing unit is an optical fiber arranged in parallel with the object to be measured, and the method is used in the case where the object to be measured is affected by an external environment and the acting force varies randomly.

7. A towed formation detection system based on shape perception, characterized in that: The invention comprises a towed array structure, a strain measuring device and a processor, wherein the towed array structure comprises a towed array and a plurality of sensing units, wherein the plurality of sensing units are circumferentially arranged around the central axis of the towed array and fixedly connected to the towed array, and each sensing unit is connected to the strain measuring device, which is connected to the processor. The processor reconstructs a three-dimensional curve of the towed array using the three-dimensional curve reconstruction method according to any one of claims 1 to 6 based on the strain magnitude at different positions on each sensing unit detected by the strain measuring device, thereby monitoring the morphology of the towed array.

8. The shape-aware towed array detection system according to claim 7, characterized in that: The towed array structure also includes an outer sheath and a support rope. The towed array, each sensor unit and the support rope are all parallel and cross the outer sheath. The support rope is located between the towed array and the outer sheath, and the towed array and each sensor unit are spaced apart from the outer sheath.

9. The shape-aware towed array detection system according to claim 7 or 8, characterized in that: The towed array is composed of a plurality of sensor element skeletons, and each sensor element skeleton is arranged at intervals along the central axis direction of the towed array; the towed array is a hydrophone array.

10. The shape-aware towed array detection system according to claim 9, characterized in that: The sensing unit is an optical fiber.

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