An aerial refueling hose real-time stress measurement method based on an optical fiber force sensor

Abstract

The present application relates to a kind of aerial refueling hose real-time stress measurement method based on optical fiber force sensor, belong to aerial refueling technical control field.The method includes: considering the damping characteristic of refueling hose material itself, based on absolute node coordinate, the nonlinear dynamics model of aerial refueling hose unit is established;According to arbitrary Lagrange-Euler multi-body system modeling method, the combination model of hose cone sleeve system is established, and the stress monitoring position of hose is determined using numerical simulation analysis;Considering the flexible structure of hose and the motion state and stress condition of hose in whip process, while combining the measurement principle of optical fiber force sensor, the layout method of spiral winding multi-point measurement optical fiber force sensor is designed.The designed optical fiber force measurement feedback method can transmit hose stress change and bending deformation to refueling nacelle reel control system in real time, improve whip suppression efficiency, and strengthen the success rate and safety of aerial refueling.

Description

Technical Field

[0001] This invention relates to the field of aerial refueling hose force measurement technology, specifically to a real-time stress measurement method for aerial refueling hoses based on fiber optic force sensors. Background Technology

[0002] As the mainstream refueling method in my country, flexible aerial refueling has undergone extensive research in its key technologies and has been adopted by most refueling / receiving aircraft. During flexible refueling, when the relative speed difference between the receiving and tanker aircraft is too large, the refueling hose is in a slack state. Affected by the surrounding high-speed airflow and its own gravity, the hose experiences violent whipping, seriously threatening the safety of the refueling mission. Existing reel recovery devices utilize the tightening action of the reel mechanism within the refueling pod to adjust the hose length, reduce the hose's slack, and maintain constant hose tension, thus preventing whipping.

[0003] The refueling pod reel system uses force sensors to measure the tension of the hose at the pod outlet, compares it with the tension under stable towing conditions, and calculates the hose reeling speed to adjust the hose length and suppress whiplash. However, in the initial stage of actual refueling docking, the hose tip (near the cone) experiences a huge impact force the instant the refueling cone contacts the receiving plug. The tension at this point changes earliest, and the traditional sensor measurement layout results in a certain lag in the refueling hose reeling. Summary of the Invention

[0004] The technical problem to be solved by this invention is:

[0005] To address the issue of stress measurement lag under hose whiplash conditions, this invention provides a real-time stress measurement method for aerial refueling hoses based on fiber optic force sensors. This method can provide real-time feedback of hose bending deformation to the refueling pod reel control system. Furthermore, fiber optic measurement offers greater safety than electrical signal measurement in aerial refueling scenarios.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A method for real-time stress measurement of an aerial refueling hose based on a fiber optic force sensor, characterized in that the method includes:

[0008] A nonlinear dynamic model of the aerial refueling hose unit is established based on absolute node coordinates;

[0009] Based on the modeling method of arbitrary Lagrange-Euler multibody systems, the hose unit is directly assembled to establish a combined model of the hose conical sleeve system, and the stress monitoring location of the hose is determined by numerical simulation analysis.

[0010] Four fiber optic force sensors are arranged circumferentially around the stress monitoring location of the hose. The four force sensors are arranged around the same cross section of the hose at 90-degree intervals to form a four-quadrant sensor combination.

[0011] The strain of the refueling hose is measured using four fiber optic force sensors, and the bending angle and bending moment of the refueling hose are calculated.

[0012] A further technical solution of the present invention: the nonlinear dynamic model of the aerial refueling hose unit based on absolute node coordinates includes:

[0013] The refueling hose is divided into a continuous body composed of multiple node units. A central axis model is used, where the arc length from any point on the hose's central axis to the reference point is represented by the material coordinate s. The displacement vector r(s,t) of the hose unit nodes can be expressed as the product of the node element shape function matrix N(s) in the generalized coordinate system with time t and the node coordinate q. The expression is:

[0014] r(s,t)=N(s)q(t) (1)

[0015] The shape function matrix N(s) of the flexible tube node element can be expressed as:

[0016] N(s)=[N1(s)I,N2(s)I,N3(s)I,N4(s)I] (2)

[0017] In the formula, I is a third-order identity matrix, and N1, N2, N3, and N4 are matrix coefficients, expressed as:

[0018]

[0019] In the formula, η = s / l, where l is the length of the hose unit;

[0020] Node coordinates q The absolute coordinates and derivatives of the two nodes of the flexible tube element in the generalized coordinate system are as follows:

[0021]

[0022] In the formula, the subscript s denotes the derivative of r(s) with respect to s.

[0023] The dynamic model of the hose unit is calculated using the principle of virtual work, and the expression is as follows:

[0024]

[0025] In the formula, δW i The virtual work δW of the inertial force on the hose unit during refueling e Internal energy is a form of virtual skill, δW f M is an external force that creates virtual work. eLet Q be the generalized mass matrix of the hose unit. e Q is the generalized force corresponding to the axial and bending strains of the hose unit. f This refers to the generalized force corresponding to the external force on the flexible hose unit;

[0026]

[0027] In the formula, ρ1 is the linear density of the hose, and A is the cross-sectional area of ​​the hose;

[0028] Refueling hoses are made of a special type of rubber composite material and exhibit viscoelasticity. The generalized forces corresponding to the axial and bending strains of the hose unit are:

[0029]

[0030] In the formula, E is the elastic modulus of the hose, J is the moment of inertia of the hose cross section, c is the damping coefficient of the hose, ε is the axial strain, and κ is the bending rate of the hose.

[0031] The axial strain and tortuosity of the hose can be specifically expressed as follows:

[0032]

[0033]

[0034] In the formula, r s Let r(s) be the first derivative. ss Let r(s) represent the second derivative;

[0035] Generalized gravity Q of the flexible unit fg The expression is:

[0036]

[0037] Where G = [0, 0, g] T ;

[0038] The virtual work δW corresponding to other external forces F acting on the flexible unit of for:

[0039] δW of =δr T F=δq T N T (s)F=δq T Q of (11)

[0040] Therefore, the generalized force Q corresponding to other external forces in the flexible hose unit of for:

[0041] Q of =N T(s)F (12)

[0042] During the refueling process, the hose unit is affected by aerodynamic forces due to the external flow field. The aerodynamic forces on the hose include aerodynamic friction and aerodynamic pressure difference.

[0043] Aerodynamic friction F t The direction is parallel to the axis of the flexible micro-element, and the expression is:

[0044]

[0045] In the formula, d0 represents the outer diameter of the hose, and C t This indicates the coefficient of friction of the hose surface. Let i be the relative velocity of the hose element. k =r s / ||r s ||;

[0046] pneumatic pressure difference force F n The direction is perpendicular to the axis of the flexible micro-element, and the expression is:

[0047]

[0048] In the formula, C n This indicates the hose pressure differential coefficient.

[0049] A further technical solution of the present invention: Based on multibody dynamics theory, a combined model of the hose-cone sleeve system is established, and numerical simulation analysis is used to determine the stress monitoring location of the hose, including:

[0050] The refueling cone sleeve is connected to the end of the refueling hose. The relationship between the two can be regarded as a fixed constraint between a rigid body and a flexible cable. The element node expression of the hose end is:

[0051]

[0052] In the formula, Let λ be the Jacobian matrix of the constraint equations. t Q is a Lagrange multiplier. ft For the external force on the hose unit near the tapered sleeve end, C ekt The constraint equation between the refueling hose and the cone sleeve is:

[0053]

[0054] Where, r N The absolute coordinates of the hose end node, r t The generalized coordinates corresponding to the centroid of the cone sleeve are represented by , and e represents the distance between the end node of the hose and the centroid of the cone sleeve.

[0055] In addition to the forces acting on the hose unit itself, the hose unit near the tapered sleeve end also experiences the weight of the tapered sleeve and the aerodynamic load forces acting on it. Q ft It can be represented as:

[0056] Q ft =Q fg +Q oft =Q fg +Q dg +N T (s)(F t +F n +F d (17)

[0057] In the formula, F d The aerodynamic drag experienced by the refueling cone sleeve, Q dg The generalized force corresponding to the weight of the cone sleeve itself;

[0058]

[0059] In the formula, S d C represents the effective resistance area of ​​the tapered sleeve. d This indicates the aerodynamic drag coefficient of the tapered sleeve;

[0060] Q dg =N T (s)m d G (19)

[0061] In the formula, m d The mass of the tapered sleeve;

[0062] During the refueling docking process, the receiving aircraft impacts the hose cone sleeve, and the external force Q acting on the hose cone sleeve unit at this time... ftt It can be represented as:

[0063]

[0064] In the formula, F r The impact force of the oiler on the refueling cone sleeve is along the direction of the cone sleeve's center of mass.

[0065] A further technical solution of the present invention: Based on multibody dynamics theory, a combined model of the hose-cone sleeve system is established, and numerical simulation analysis is used to determine the stress monitoring location of the hose, which also includes:

[0066] Based on the combined model of the hose-cone system, a motion simulation system for the hose-cone system was built using MATLAB / Simulink to simulate the stress changes at various nodes of the hose-cone system under different flight speeds.

[0067] Based on the numerical simulation results, the real-time monitoring position of the fiber optic force sensor on the refueling hose is determined to be near the cone end.

[0068] A further technical solution of the present invention: the step of measuring the strain of the refueling hose using four fiber optic force sensors and calculating the bending angle and bending moment of the refueling hose includes:

[0069] Four fiber optic force sensors measured the hose strains as ε1, ε2, ε3, and ε4, respectively. The strain ε caused by the axial external force on the hose is... s Represented as:

[0070]

[0071] According to Hooke's Law, the stress in the hose caused by axial external force is:

[0072]

[0073] The refueling hose has a large length-to-diameter ratio, therefore, the bending of the hose can be considered as the bending of a slender beam. The normal stress on the outer wall of the hose is represented by the strain detected by four strain sensors, and the normal stress σ in the y direction is... y and the normal stress σ in the z-direction z Represented as:

[0074]

[0075] The bending angle and bending moment of the refueling hose are as follows:

[0076]

[0077]

[0078] In the formula, θ d For the bending angle of the refueling hose, M d This represents the bending moment at the cross-section of the hose.

[0079] A further technical solution of the present invention: The installation method of the four fiber optic force sensors is as follows: Four optical fibers are placed between the buried wire layer and the outer lining layer using an optical fiber protective sleeve, and wound into a spring-like structure, with the central axis of the spring-like optical fiber aligned with the central axis of the refueling hose; the fiber optic force sensors are attached to the periphery of the buried wire layer of the refueling hose at the ends of the four optical fibers in a four-quadrant sensor combination, and the signal is transmitted to the signal demodulation and processing module through the optical fiber to reflect the strain state of the hose, and the optical fiber signal demodulation and processing module is fixed inside the refueling pod.

[0080] A computer system is characterized by comprising: one or more processors, and a computer-readable storage medium for storing one or more programs, wherein when the one or more programs are executed by the one or more processors, the one or more processors cause the one or more processors to implement the method described above.

[0081] A computer-readable storage medium is characterized by storing computer-executable instructions, which, when executed, are used to implement the above-described method.

[0082] The beneficial effects of this invention are as follows:

[0083] This invention provides a real-time stress measurement method for aerial refueling hoses based on fiber optic force sensors. The designed fiber optic force sensor can detect changes in the bending shape of the hose in real time and feed back to the refueling pod reel control system.

[0084] Compared with existing technologies, it has the following advantages:

[0085] 1. This invention establishes a multibody dynamics model of the refueling hose conical sleeve system based on the absolute node coordinate method, which can reflect the continuous stress bending change of the hose. The calculation accuracy is further improved compared with the ball-and-stick model currently used. At the same time, the damping characteristics inside the refueling hose are considered. The simulation results of hose whip stress show that the stress change of the hose unit node at the refueling pod end has a certain lag compared with the refueling conical sleeve end, which provides a certain data basis and theoretical guidance for the selection of the monitoring position of the hose whip force sensor.

[0086] 2. This invention utilizes the principle that the diffraction wavelength and refractive index of optical fibers change when subjected to external force or bending. It designs an optical fiber force sensor to acquire changes in hose bending and stress. A four-quadrant sensor combination monitors hose morphological changes. The optical fiber is spirally embedded between the fuel hose's embedded layer and outer lining layer, improving the lifespan of the optical fiber force sensor. The four-quadrant optical fiber force sensor combination can rapidly feed back the hose's bending deformation and mechanical state to the whiplash suppression control system in real time, improving the success rate and safety of in-flight refueling. Traditional force sensors convert the force on the hose into a corresponding electrical signal, involving the installation and winding of circuitry on a fuel-filled hose, posing significant safety hazards. This invention, based on an optical fiber force sensor for hose stress monitoring, offers greater safety. Attached Figure Description

[0087] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0088] Figure 1 This is a flowchart of a method for real-time stress measurement of aerial refueling hoses based on fiber optic force sensors;

[0089] Figure 2 This is a schematic diagram of the refueling hose cone sleeve assembly established based on the absolute node coordinate method;

[0090] Figure 3 The diagram shows the whip-like motion curve of the hose under the action of a relative docking speed of 3 m / s between the receiver and the oiler.

[0091] Figure 4 The axial stress response curves of node 1 and node 21 of the hose unit are shown in the figure, taking into account the damping effect of the hose.

[0092] Figure 5 A schematic diagram of a four-quadrant combination of fiber optic force sensors;

[0093] Figure 6 This is a schematic diagram of the cross-section of an optical fiber;

[0094] Figure 7 A schematic cross-sectional view of an optical fiber spirally wound and embedded between the wire layer and the outer lining layer of a refueling hose.

[0095] Figure 8 A schematic diagram of the refueling pod, hoses, and cone sleeve system. Detailed Implementation

[0096] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0097] This invention discloses a real-time stress measurement method for aerial refueling hoses based on fiber optic force sensors, referring to... Figure 1 As shown, the design method specifically includes the following steps:

[0098] Step 1: Establish a nonlinear dynamic model of the aerial refueling hose unit based on absolute node coordinates.

[0099] The refueling hose is divided into a continuous body composed of multiple node units, as shown in the reference. Figure 2 As shown, a central axis model is adopted, with the material coordinate s representing the arc length from any point on the central axis of the hose to the reference point. The displacement vector r(s,t) of the hose element node changes with time t, which can be expressed as the product of the nodal element shape function matrix N(s) and the nodal coordinate q in the generalized coordinate system. The expression is as follows:

[0100] r(s,t)=N(s)q(t) (26)

[0101] The shape function matrix N(s) of the flexible tube node element can be expressed as:

[0102] N(s)=[N1(s)I,N2(s)I,N3(s)I,N4(s)I] (27)

[0103] In the formula, I is a third-order identity matrix, and N1, N2, N3, and N4 are matrix coefficients, expressed as:

[0104]

[0105] In the formula, η = s / l, where l is the length of the hose unit;

[0106] The node coordinates q represent the absolute coordinate positions and derivatives of the two nodes of the flexible tube element in the generalized coordinate system, specifically:

[0107]

[0108] In the formula, the subscript s denotes the derivative of r(s) with respect to s;

[0109] The dynamic model of the hose unit is calculated using the principle of virtual work, and the expression is as follows:

[0110]

[0111] In the formula, δW i The virtual work δW of the inertial force on the hose unit during refueling e Internal energy is a form of virtual skill, δW f M is an external force that creates virtual work. e Let Q be the generalized mass matrix of the hose unit. e Q is the generalized force corresponding to the axial and bending strains of the hose unit. f This refers to the generalized force corresponding to the external force on the flexible hose unit;

[0112]

[0113] In the formula, ρ1 is the linear density of the hose, and A is the cross-sectional area of ​​the hose;

[0114] Refueling hoses are made of a special type of rubber composite material and exhibit viscoelasticity. The generalized forces corresponding to the axial and bending strains of the hose unit are:

[0115]

[0116] In the formula, E is the elastic modulus of the hose, J is the moment of inertia of the hose cross section, c is the damping coefficient of the hose, ε is the axial strain, and κ is the bending rate of the hose.

[0117] The axial strain and tortuosity of the hose can be specifically expressed as follows:

[0118]

[0119]

[0120] In the formula, r s Let r(s) be the first derivative. ss Let r(s) represent the second derivative;

[0121] Generalized gravity Q of the flexible unit fg The expression is:

[0122]

[0123] Where G = [0, 0, g] T ;

[0124] The virtual work δW corresponding to other external forces F acting on the flexible unit of for:

[0125] δW of =δr T F=δq T N T (s)F=δq T Q of (36)

[0126] Therefore, the generalized force Q corresponding to other external forces in the flexible hose unit of for:

[0127] Q of =N T (s)F (37)

[0128] During the refueling process, the hose unit is affected by aerodynamic forces due to the external flow field. The aerodynamic forces on the hose include aerodynamic friction and aerodynamic pressure difference.

[0129] Aerodynamic friction F t The direction is parallel to the axis of the flexible micro-element, and the expression is:

[0130]

[0131] In the formula, d0 represents the outer diameter of the hose, and C t This indicates the coefficient of friction of the hose surface. Let i be the relative velocity of the hose element. k =r s / ||r s ||;

[0132] pneumatic pressure difference force F n The direction is perpendicular to the axis of the flexible micro-element, and the expression is:

[0133]

[0134] In the formula, C n This indicates the hose pressure differential coefficient.

[0135] Step 2: Based on the modeling method of arbitrary Lagrange-Euler multibody systems, the hose unit is directly assembled to establish the combined model of the hose conical sleeve system, and the stress monitoring position of the hose is determined by numerical simulation analysis.

[0136] The refueling cone sleeve is connected to the end of the refueling hose. The relationship between the two can be regarded as a fixed constraint between a rigid body and a flexible cable. The element node expression of the hose end is:

[0137]

[0138] In the formula, Let λ be the Jacobian matrix of the constraint equations. t Q is a Lagrange multiplier. ft For the external force on the hose unit near the tapered sleeve end, C ekt The constraint equation between the refueling hose and the cone sleeve is:

[0139]

[0140] Where, r N The absolute coordinates of the hose end node, r t The generalized coordinates corresponding to the centroid of the cone sleeve are represented by , and e represents the distance between the end node of the hose and the centroid of the cone sleeve.

[0141] In addition to the forces acting on the hose unit itself, the hose unit near the tapered sleeve end also experiences the weight of the tapered sleeve and the aerodynamic load forces acting on it. Q ft It can be represented as:

[0142] Q ft =Q fg +Q oft =Q fg +Q dg +N T (s)(F t +F n +F d (42)

[0143] In the formula, F d The aerodynamic drag experienced by the refueling cone sleeve, Q dg The generalized force corresponding to the weight of the cone sleeve itself;

[0144]

[0145] In the formula, S d C represents the effective resistance area of ​​the tapered sleeve. d This indicates the aerodynamic drag coefficient of the tapered sleeve;

[0146] Q dg =N T (s)md G (44)

[0147] In the formula, m d The mass of the tapered sleeve;

[0148] During the refueling docking process, the receiving aircraft impacts the hose cone sleeve, and the external force Q acting on the hose cone sleeve unit at this time... ftt It can be represented as:

[0149]

[0150] In the formula, F r The impact force of the receiving machine on the refueling cone sleeve is along the direction of the cone sleeve's center of mass;

[0151] Based on the multibody dynamics model of the hose-cone system, a motion simulation system for the hose-cone system was built using MATLAB / Simulink to simulate the stress changes at various nodes of the hose-cone system under different flight speeds.

[0152] Assuming the refueling hose is in a fully towed state and the hose length is 20m, considering the calculation accuracy and efficiency, it is divided into 20 hose units. The end closest to the refueling pod is the first node, and the end of the cone sleeve is the 21st node. Calculate the stress change of the hose unit nodes.

[0153] The relative docking speed of the receiver aircraft is set to 3 m / s to simulate the hose whipping phenomenon. The simulation results are referenced. Figure 3 As shown;

[0154] Simultaneously with the occurrence of the hose whiplash phenomenon, considering the hose damping characteristics, there is a 0.1s lag in tension change at node 1 compared to node 21. (Refer to...) Figure 4 As shown;

[0155] Based on the numerical simulation results, the real-time monitoring position of the fiber optic force sensor on the refueling hose is determined to be near the cone end. Considering that the connection structure of the cone is complex and the force sensor is difficult to install at the 21st node, the 20th node is selected as the monitoring position of the fiber optic force sensor.

[0156] Step 3: Based on the stress monitoring status of the characteristic points of the flexible hose bending deformation, and combined with the installation matching characteristics of the flexible hose and the fiber optic force sensor, design a fiber optic force sensor layout method for multi-point measurement by spiral winding.

[0157] When optical fibers are subjected to external force or bending, their diffraction wavelength and refractive index change. By utilizing the sensitivity of the center wavelength of a fiber Bragg grating (FBG) to axial strain, the changes in the bending and stress of the flexible tube can be obtained through the change of the center wavelength.

[0158] When the length and refractive index of the FBG gate region change, the center wavelength λ of its reflection spectrum changes accordingly. Based on the change in λ, the magnitude of the FBG strain can be calculated. Through signal demodulation and processing, the stress of the hose corresponding to the FBG strain can be obtained.

[0159] When using fiber optic force sensors to monitor changes in hose stress, it is important to consider that a single sensor can only measure a single stress parameter at a fixed location. The whip-like motion of the hose causes the hose to bend in an unpredictable direction, making it difficult to get feedback on the whip-like motion state of the hose by relying on a single-point force sensor.

[0160] Four force sensors are arranged at 90-degree intervals around the same cross-section of the hose to form a four-quadrant sensor combination, as referenced. Figure 5 As shown, the sensors arranged clockwise along the hose are sensor 1, sensor 2, sensor 3, and sensor 4.

[0161] Using the refueling hose cross-section as the reference plane, the direction from the center of the hose cross-section to sensor 1 is the positive y-axis direction, and the direction from the center of the hose cross-section to sensor 4 is the positive z-axis direction. The hose cross-section is divided into four quadrants.

[0162] Force sensors 1-4 measured the hose strains at the 20th node of the hose as ε1, ε2, ε3, and ε4, respectively. The strain ε is caused by the axial external force acting on the hose. s It can be represented as:

[0163]

[0164] According to Hooke's Law, the stress in the hose caused by axial external force is:

[0165]

[0166] The refueling hose has a large length-to-diameter ratio, therefore, the bending of the hose can be considered as the bending of a slender beam. The normal stress on the outer wall of the hose can be represented by the strain detected by four strain sensors, and the normal stress σ in the y direction is... y and the normal stress σ in the z-direction z It can be represented as:

[0167]

[0168] The bending angle and bending moment of the refueling hose are as follows:

[0169]

[0170]

[0171] In the formula, θ d For the bending angle of the refueling hose, M d The bending moment at the hose cross-section;

[0172] Refueling hoses are made of a type of rope-like composite rubber material, generally consisting of three layers: an inner lining layer, a wire embedding layer, and an outer lining layer, which have a certain degree of tensile and bending capacity.

[0173] Considering the flexibility of the hose itself, the structure, installation method, and fiber optic cable embedding method of the fiber optic force sensor must be matched with the hose itself so that the sensor can accurately and in real time convert the hose deformation information into a sensing signal without damaging the fiber optic structure or reducing the fiber optic lifespan.

[0174] Four optical fibers are placed between the buried layer and the outer sheath using an optical fiber protective sleeve. The cross-section of the optical fibers is referenced. Figure 6 As shown, the optical fiber is wound into a spring-like structure, with the central axis of the spring-shaped optical fiber aligned with the central axis of the refueling hose. (Refer to...) Figure 7 As shown;

[0175] The fiber optic force sensor, with its four fiber optic ends arranged in a four-quadrant sensor configuration, is attached to the outer perimeter of the refueling hose's wiring layer. The signal is transmitted via fiber optics to a signal demodulation and processing module, reflecting the hose's strain state. This module is fixed inside the refueling pod. Figure 8 As shown;

[0176] When the hose is stretched and bent, it will cause the spring-shaped optical fiber structure to change, which will also cause a certain stretch. At the same time, the optical fiber itself has a stretch rate of 0.6%. The optical fiber is spirally wound and buried in the hose to improve the life of the force sensor.

[0177] Based on the fiber optic stress measurement feedback of node 20, the bending deformation and mechanical state of the hose can be quickly fed back to the whiplash suppression control system in real time, which improves the success rate and safety of aerial refueling.

[0178] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the scope of the technology disclosed in the present invention, and such modifications or substitutions should all be covered within the scope of protection of the present invention.

Claims

1. A method for real-time stress measurement of an aerial refueling hose based on a fiber optic force sensor, characterized in that, The method includes: A nonlinear dynamic model of the aerial refueling hose unit is established based on absolute node coordinates; Based on the modeling method of arbitrary Lagrange-Euler multibody systems, the hose unit is directly assembled to establish a combined model of the hose conical sleeve system, and the stress monitoring location of the hose is determined by numerical simulation analysis. Four fiber optic force sensors are arranged circumferentially around the stress monitoring location of the hose. The four force sensors are arranged around the same cross section of the hose at 90-degree intervals to form a four-quadrant sensor combination. The strain of the refueling hose is measured using four fiber optic force sensors, and the bending angle and bending moment of the refueling hose are calculated.

2. The method for real-time stress measurement of an aerial refueling hose based on a fiber optic force sensor according to claim 1, characterized in that, The nonlinear dynamic model of the aerial refueling hose unit based on absolute node coordinates includes: The refueling hose is divided into a continuous body composed of multiple node units. A central axis model is used, where the arc length from any point on the hose's central axis to the reference point is represented by the material coordinate s. The displacement vector r(s,t) of the hose unit nodes can be expressed as the product of the node element shape function matrix N(s) in the generalized coordinate system with time t and the node coordinate q. The expression is: r(s,t)=N(s)q(t) (1) The shape function matrix N(s) of the flexible tube node element can be expressed as: N(s)=[N1(s)I,N2(s)I,N3(s)I,N4(s)I] (2) In the formula, I is a third-order identity matrix, and N1, N2, N3, and N4 are matrix coefficients, expressed as: In the formula, η = s / l, where l is the length of the hose unit; The node coordinates q represent the absolute coordinate positions and derivatives of the two nodes of the flexible tube element in the generalized coordinate system, specifically: In the formula, the subscript s denotes the derivative of r(s) with respect to s; The dynamic model of the hose unit is calculated using the principle of virtual work, and the expression is as follows: In the formula, δW i The virtual work δW of the inertial force on the hose unit during refueling e Internal energy is a form of virtual skill, δW f M is an external force that creates virtual work. e Let Q be the generalized mass matrix of the hose unit. e Q is the generalized force corresponding to the axial and bending strains of the hose unit. f This refers to the generalized force corresponding to the external force on the flexible hose unit; In the formula, ρ1 is the linear density of the hose, and A is the cross-sectional area of ​​the hose; Refueling hoses are made of a special type of rubber composite material and exhibit viscoelasticity. The generalized forces corresponding to the axial and bending strains of the hose unit are: In the formula, E is the elastic modulus of the hose, J is the moment of inertia of the hose cross section, c is the damping coefficient of the hose, ε is the axial strain, and κ is the bending rate of the hose. The axial strain and tortuosity of the hose can be specifically expressed as follows: In the formula, r s Let r(s) be the first derivative. ss Let r(s) represent the second derivative; Generalized gravity Q of the flexible unit fg The expression is: Where G = [0, 0, g] T ; The virtual work δW corresponding to other external forces F acting on the flexible unit of for: δW of =δr T F=δq T N T (s)F=δq T Q of (11) Therefore, the generalized force Q corresponding to other external forces in the flexible hose unit of for: Q of =N T (s)F (12) During the refueling process, the hose unit is affected by aerodynamic forces due to the external flow field. The aerodynamic forces on the hose include aerodynamic friction and aerodynamic pressure difference. Aerodynamic friction F t The direction is parallel to the axis of the flexible micro-element, and the expression is: In the formula, d0 represents the outer diameter of the hose, and C t This indicates the coefficient of friction of the hose surface. Let i be the relative velocity of the hose element. k =r s / ||r s ||; pneumatic pressure difference force F n The direction is perpendicular to the axis of the flexible micro-element, and the expression is: In the formula, C n This indicates the hose pressure differential coefficient.

3. The method for real-time stress measurement of an aerial refueling hose based on a fiber optic force sensor according to claim 2, characterized in that, Based on multibody dynamics theory, a combined model of the hose-cone sleeve system is established, and numerical simulation analysis is used to determine the stress monitoring locations of the hose, including: The refueling cone sleeve is connected to the end of the refueling hose. The relationship between the two can be regarded as a fixed constraint between a rigid body and a flexible cable. The element node expression of the hose end is: In the formula, Let λ be the Jacobian matrix of the constraint equations. t Q is a Lagrange multiplier. ft For the external force on the hose unit near the tapered sleeve end, C ekt The constraint equation between the refueling hose and the cone sleeve is: Where, r N The absolute coordinates of the hose end node, r t The generalized coordinates corresponding to the centroid of the cone sleeve are represented by , and e represents the distance between the end node of the hose and the centroid of the cone sleeve. In addition to the forces acting on the hose unit itself, the hose unit near the tapered sleeve end also experiences the weight of the tapered sleeve and the aerodynamic load forces acting on it. Q ft It can be represented as: Q ft =Q fg +Q oft =Q fg +Q dg +N T (s)(F t +F n +F d ) (17) In the formula, F d The aerodynamic drag experienced by the refueling cone sleeve, Q dg The generalized force corresponding to the weight of the cone sleeve itself; In the formula, S d C represents the effective resistance area of ​​the tapered sleeve. d This indicates the aerodynamic drag coefficient of the tapered sleeve; Q dg =N T (s)m d G (19) In the formula, m d The mass of the tapered sleeve; During the refueling docking process, the receiving aircraft impacts the hose cone sleeve, and the external force Q acting on the hose cone sleeve unit at this time... ftt It can be represented as: In the formula, F r The impact force of the oiler on the refueling cone sleeve is along the direction of the cone sleeve's center of mass.

4. The method for real-time stress measurement of an aerial refueling hose based on a fiber optic force sensor according to claim 3, characterized in that, The process of establishing a combined model of the hose-cone sleeve system based on multibody dynamics theory and determining the stress monitoring location of the hose using numerical simulation analysis also includes: Based on the combined model of the hose-cone system, a motion simulation system for the hose-cone system was built using MATLAB / Simulink to simulate the stress changes at various nodes of the hose-cone system under different flight speeds. Based on the numerical simulation results, the real-time monitoring position of the fiber optic force sensor on the refueling hose is determined to be near the cone end.

5. The real-time stress measurement method for aerial refueling hoses based on fiber optic force sensors as described in claim 4, characterized in that, The process of measuring the strain of the refueling hose using four fiber optic force sensors and calculating the bending angle and moment of the refueling hose includes: Four fiber optic force sensors measured the hose strains as ε1, ε2, ε3, and ε4, respectively. The strain ε caused by the axial external force on the hose is... s Represented as: According to Hooke's Law, the stress in the hose caused by axial external force is: The refueling hose has a large length-to-diameter ratio, therefore, the bending of the hose can be considered as the bending of a slender beam. The normal stress on the outer wall of the hose is represented by the strain detected by four strain sensors, and the normal stress σ in the y direction is... y and the normal stress σ in the z-direction z Represented as: The bending angle and bending moment of the refueling hose are as follows: In the formula, θ d For the bending angle of the refueling hose, M d This represents the bending moment at the cross-section of the hose.

6. The method for real-time stress measurement of an aerial refueling hose based on a fiber optic force sensor according to claim 5, characterized in that, The installation method of the four fiber optic force sensors is as follows: four optical fibers are placed between the buried wire layer and the outer liner layer using an optical fiber protective sleeve and wound into a spring-like structure. The central axis of the spring-like optical fiber is consistent with the central axis of the refueling hose. The fiber optic force sensors are attached to the periphery of the buried wire layer of the refueling hose at the ends of the four optical fibers in a four-quadrant sensor combination. The signal is transmitted to the signal demodulation and processing module through the optical fiber to reflect the strain state of the hose. The fiber optic signal demodulation and processing module is fixed in the refueling pod.

7. A computer system, characterized in that... include: One or more processors, a computer-readable storage medium for storing one or more programs, wherein, when the one or more programs are executed by the one or more processors, the one or more processors cause the one or more processors to implement the method of claim 1.

8. A computer-readable storage medium, characterized in that... The device stores computer-executable instructions, which, when executed, are used to implement the method of claim 1.

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