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

Abstract

The invention provides a three-dimensional curve reconstruction method and a towed formation detection system based on shape perception, and the method comprises the steps: a plurality of sensing units are circumferentially arranged around the central axis of a to-be-detected object, each sensing unit is bent along with the bending of the to-be-detected object, and for each sensing unit, the shape of the to-be-detected object is calculated; the included angles between the radial lines corresponding to the sensing units on each cross section and the X axis are the same; for each sensing unit on the cross section of the to-be-measured object, determining the distance from the sensing unit to the bending neutral surface according to the included angle between the corresponding radial line of the sensing unit and the X axis and the included angle between the bending direction of the cross section and the X axis; determining a total curvature vector of the object to be detected according to the strain detected by each sensing unit and the determined distance; according to the total curvature vector, the torsion rate of the object to be measured and the curvature in the bending tangent direction are determined; determining a unit tangent vector of the to-be-measured object in the bending tangent direction according to the torsion rate and the curvature; and carrying out integration on the unit tangent vector, and reconstructing a three-dimensional curve of the object to be measured. The three-dimensional reconstruction method is simple, efficient and high in accuracy.

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 towing formation detection system based on shape perception. Background Art

[0002] Marine resources are crucial to the sustainable development of national economy, military security, etc., and countries are paying more attention to the exploration of marine resources than ever before. Underwater long-range target detection depends on the perception of underwater sound signals, among which hydrophones, as key components, play an important role in ocean exploration and target analysis.

[0003] In practical applications, it is usually assumed that the array remains horizontal during movement. However, during the towing process, the array may bend or shake due to the influence of fluid resistance or the structure of the array itself, which affects the detection performance. Therefore, the attitude of the array cannot be simply considered as a straight line, and how to effectively measure the array formation will become the key to improving the detection performance of the towed array and improving the detection accuracy and other important indicators.

[0004] The existing towed array formation measurement methods 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 signal received by the fiber optic hydrophone to calculate the formation; while the non-acoustic method requires the use of other sensors to measure the key coordinate parameters in the space or perform mechanical analysis on the array to achieve the purpose of measurement. The above methods all 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, but 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 fact, there are many other methods for measuring three-dimensional shape at present, but because the external environment acting on the towed array changes randomly, compared with the above two measurement methods, the accuracy of other methods for measuring the three-dimensional shape of the towed array will be lower. It can be seen that when the object to be measured is applied to a scene with a randomly changing external environment, the current three-dimensional shape measurement method requires dependence on external equipment and the measurement accuracy is also low. 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, so as to solve the problem that when the object to be tested is currently applied to a scene where the external environment changes randomly, the three-dimensional shape measurement of the object to be tested needs to rely on 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: multiple sensing units for detecting strain magnitude are arranged 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 arranged 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, and for each sensing unit, an angle α between a 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 to be measured at 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 to be measured be the bending neutral plane, and s is the distance from one end of the object to be measured and is 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 sensor 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 to be tested at position s;

[0011] Step S400: Calculate the components K of the total curvature vector K(s) of the object to be tested 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 tested; determine the curvature κ(s) of the object to be tested in the bending tangent direction according to the total curvature vector K(s) of the object to be tested at position s;

[0012] Step S500, determining the unit tangent vector T(s) of the object under test in the direction of the bending tangent according to the torsion τ(s) and the curvature K(s) of the object under test; integrating the unit tangent vector T(s) of the object under test in the direction of the bending tangent 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 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 sensor 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 to be tested in the direction of the bending tangent line.

[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 to be tested 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 to be tested in the direction of the bending tangent is integrated to reconstruct the three-dimensional curve r(s) of the central axis of the object to be tested:

[0025]

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

[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 corresponding to 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 changes randomly.

[0029] According to a second aspect of an embodiment of the present invention, there is provided a shape-sensing based towed array detection system, 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 sensor units, wherein the plurality of sensor units are circumferentially arranged around a central axis of the towed array at the periphery of the towed array and are fixedly connected to the towed array, wherein each of the sensor units is connected to the strain measurement device, and the strain measurement device is connected to the processor, and the processor reconstructs a three-dimensional curve of the towed array using the three-dimensional curve reconstruction method according to the strain magnitude at different positions on each of the sensor units 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 sensor unit and the support rope all run parallel to and across 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.

[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 direction 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 That is, no matter which cross section, the angle between the radial line of the corresponding sensing unit and the X-axis is fixed. When determining the angle θ(s) between the bending direction and the X-axis, it is not obtained by establishing a motion equation based on the corresponding relationship between the strain detected by a single sensing unit and θ(s), but firstly based on the angle α between the radial line corresponding to the sensing 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 sensor unit to the neutral plane of the bending i (s), and then according to the strain magnitude 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 the case where the external environment of the object to be measured changes randomly, and ensures the calculation accuracy of θ(s) in this case. In addition, the present invention takes into account the strain magnitude 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 by the present invention 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 κ(s) can more accurately reflect the shape of the object to be measured.

[0035] The present invention does not require the assistance of an external sound source or sensor when reconstructing a three-dimensional curve, but only relies on a sensing unit and a specific algorithm, 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; and the present invention takes into account the situation that 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;

[0036] 2. The present invention designs a calculation formula for the total curvature vector K(s). By increasing the number of N, the calculation error of θ(s) caused by the difference in the external environment on the sensor 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.

[0037] 3. The shape-sensing towed array detection system of the present invention eliminates the reliance 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 sensing 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;

[0038] 4. The present invention uses optical fiber as a sensing unit, which can further simplify the towed array shape monitoring structure, so that the towed array of a 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 It is a schematic diagram of the three-dimensional curve reconstruction principle 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 bending neutral plane;

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

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

[0044] Figure 6 It 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 of. 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 understandable, the technical solutions in the embodiments of the present invention are further described in detail below in conjunction with 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 meanings of the above terms can be understood according to 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: multiple sensing units for detecting strain magnitude are arranged 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 arranged 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, and for each sensing unit, an angle α between a 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 to be tested at 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 to be tested is the bending neutral plane, s is the distance from one end of the object to be tested and is an arbitrary value. The present invention can regard the object to be tested as a space 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 tested; 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 of the sensing unit can be three, and 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 sensor unit to the neutral plane of the bendingi (s).

[0052] Combination Figure 3 As shown in (a) to (c), for the first sensor unit, d1(s) = L*sin[α1-(90°-θ(s)] = L*cos[α1-θ(s)]; for the second sensor unit, d2(s) = L*sin[90°-(θ(s)-α2)] = L*cos[θ(s)-α2]; for the third sensor 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 sensor 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 sensor 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 neutral plane of the bending i (s), determine the total curvature vector K(s) of the object to be tested at position s. In step S300, the total curvature vector K(s) of the object to be tested at position s may 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 the Y-axis respectively. For example, N=3.

[0057] Step S400: Calculate the components K of the total curvature vector K(s) of the object to be tested 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 tested; and determine the curvature κ(s) of the object to be tested in the bending tangent direction according to the total curvature vector K(s) of the object to be tested at 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 a modulus operator; the torsion τ(s) of the object to be measured can be determined according to the formula: τ(s) = θ′(s), 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) and then multiply the result 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 sensor 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 sensor units, and It can be seen that the present invention designs the calculation formula for the total curvature vector K(s). By increasing the number of N, the calculation error of θ(s) caused by the differential influence of the external environment on the sensor 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, determining the unit tangent vector T(s) of the object under test in the direction of the bending tangent according to the torsion τ(s) and the curvature κ(s) of the object under test; integrating the unit tangent vector T(s) of the object under test in the direction of the bending tangent 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 to be tested in the direction of the curved tangent line:

[0061]

[0062] Wherein 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 with 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 to be tested 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 to be tested:

[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), 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] The existing three-dimensional reconstruction also has a method of first determining the torsion τ(s) and curvature K(s) of the object to be measured, and then determining the unit tangent vector T(s) of the object to be measured in the direction of the bending tangent according to 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, but this is only applicable to the case where the external environment of the object to be measured is fixed and the external environment influence on each sensor unit is the same. Specifically, in this case, taking three sensor units as an example, the motion equation is established, and the strain detected by each sensor 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 sensor 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 sensor units and the positive direction of the X axis. It can be seen from the above formula that 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 sensor unit is affected by other external environments in addition to the object to be measured, 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 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 isi That is, no matter which cross section, the angle between the radial line of the corresponding sensing unit and the X-axis is fixed. When determining the angle θ(s) between the bending direction and the X-axis, it is not obtained by establishing a motion equation based on the corresponding relationship between the strain detected by a single sensing unit and θ(s), but firstly based on the angle α between the radial line corresponding to the sensing 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 sensor unit to the neutral plane of the bending i (s), and then according to the strain magnitude 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 the case where the external environment of the object to be measured changes randomly, and ensures the calculation accuracy of θ(s) in this case. In addition, the present invention takes into account the strain detected by all sensor units when determining the total curvature vector K(s). Therefore, the accuracy of θ(s), torsion τ(s) and curvature κ(s) determined by the present invention 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, but 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; and the present invention takes into account the situation that 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 under test when it is bent, while the dotted line represents the shape of the object under test when it is in a horizontal state. 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 at the periphery of the towed array 1 and are fixedly connected to the towed array 1, each sensing unit 2 is connected to the strain measuring device, and the strain measuring device is connected to the processor. The processor reconstructs the three-dimensional curve of the towed array by using the 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 also include an outer sheath 3 and a support rope 4. The towed array 1, each sensor unit 2 and the support rope 4 are parallel and cross 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 unit 2 may be a single-mode optical fiber with anti-bending properties, the sensor element skeleton may have anti-tensile properties in the axial direction, 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. For each sensing unit skeleton, the two ends of the axial direction are fixed to the corresponding sections of the sensing unit by resin glue 5. In order to prevent the sensing unit from breaking due to excessive tension, the sensing units between two adjacent sensing unit skeletons can be partially redundant; in addition, the towed array is in a flexible state under normal conditions, and its natural length is shorter than the length when the towing is blocked; in order to ensure that the sensing unit remains straight during the towing process, the sensing unit can be slightly wavy in the natural state. The sensing unit can be an optical fiber. The present invention uses an optical fiber as a sensing unit, which can further simplify the towed array shape monitoring structure, so that the towed array of a hydrophone, for example, can be developed towards full fiberization.

[0077] It can be seen from the above embodiments that the towed array detection system based on shape perception 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, and use the measured shape to correct the detection performance of the towed array, it can compensate for the influence of the shape change of the optical cable on its detection performance.

[0078] Those skilled in the art will readily appreciate other embodiments of the present invention 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 present invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. The specification and examples are to be considered exemplary only, and the true scope and spirit of the present invention are indicated by the following claims.

[0079] It will be appreciated that the invention is not limited to the precise construction that has been described above and shown in the drawings and that various modifications and changes may be made without departing from its scope. The scope of the invention is governed solely by the appended claims.

Claims

1. A three-dimensional curve reconstruction method, characterized in that: include: Step S100: multiple sensing units for detecting strain magnitude are arranged 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 arranged 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, and for each sensing unit, an angle α between a 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 to be measured at 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 to be measured be the bending neutral plane, and s is the distance from one end of the object to be measured and is 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 sensor 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 to be tested at position s; Step S400: Calculate the components K of the total curvature vector K(s) of the object to be tested 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 tested; determine the curvature κ(s) of the object to be tested in the bending tangent direction according to the total curvature vector K(s) of the object to be tested at position s; Step S500, determining the unit tangent vector T(s) of the object under test in the direction of the bending tangent according to the torsion τ(s) and the curvature κ(s) of the object under test; integrating the unit tangent vector T(s) of the object under test in the direction of the bending tangent 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 sensor 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 to be tested 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 to be tested in the direction of the bending tangent line.

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 to be tested 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 to be tested in the direction of the bending tangent is integrated to reconstruct the three-dimensional curve r(S) of the central axis of the object to be tested:

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 detected; 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 corresponding to 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 changes 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 at the periphery of the towed array and are fixedly connected to the towed array, each sensing unit is connected to the strain measuring device, and the strain measuring device is connected to the processor, and the processor reconstructs a three-dimensional curve of the towed array by using the three-dimensional curve reconstruction method described in any one of claims 1 to 6 according to 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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