A self-induced magnetic flux leakage based cable force monitoring system and method

Abstract

The application discloses a kind of based on spontaneous magnetic flux leakage cable force monitoring system and method, through monitoring device acquisition cable under tensile stress state is subjected to external magnetic field excitation when producing spontaneous magnetic flux leakage after magnetic field intensity signal, through signal acquisition device transmission to post-processing device, utilize cable force state monitoring model conversion cable at monitoring position tensile stress, further obtain the monitoring value of cable force, its monitoring calculation process is fast and efficient, and can better guarantee the accuracy of cable force monitoring result, therefore can be in service cable under different load stress working condition all have higher cable force monitoring precision and efficiency, and monitoring method is very low to monitoring operation requirement, operation is very simple, and cable force monitoring system can be monitored by moving the monitoring device of the monitoring device on the cable to be monitored cable at different monitoring positions Real-time cable force monitoring, it is very suitable for higher precision, real-time and low-cost monitoring to in service cable structure.

Description

Technical Field

[0001] This invention relates to the field of civil engineering structure monitoring, and in particular to a cable tension monitoring system and method based on spontaneous leakage magnetic flux. Background Technology

[0002] In the field of civil engineering, cables are widely used. Due to the long-term coupling effect of environment and load, cable structures are highly susceptible to localized corrosion, fatigue, and damage, which not only shortens their service life but also directly affects the distribution of internal forces and the structural alignment, endangering the safety of the entire structure and causing major safety accidents and economic losses. Therefore, real-time monitoring of cable forces is crucial to ensure the safety of in-service cable structures.

[0003] With the development of cable tension monitoring technology, monitoring techniques include jack tensioning, vibration frequency method, pressure sensor method, and magnetic flux method. However, most monitoring methods suffer from low measurement accuracy, inconvenient instrument use, and cumbersome data processing. Currently, the most commonly used monitoring methods are vibration frequency method and magnetic flux method.

[0004] The vibration frequency method is an "indirect" testing method. It first requires measuring the cable's natural frequency, then calculating the cable force based on the specific relationship between the cable force and its vibration frequency. Early cable force calculation theories were mainly based on string theory, treating the cable as a taut string to derive the relationship between cable force and frequency, known as classical string theory. However, due to neglecting cable stiffness, sag, and simplifying boundary conditions, significant errors occur in cable force calculations, especially for short cables where stiffness and boundary conditions have a greater impact. Many scholars both domestically and internationally have conducted extensive research and provided empirical calculation formulas. However, these formulas vary in expression, and when applied to in-service cable structures, the complex environment in which in-service cables operate, including external vibrations from wind and cable connection components, negatively impacts the accuracy and efficiency of cable force monitoring using the vibration frequency method, hindering its widespread application in practical engineering.

[0005] The magnetic flux monitoring method involves placing the cable inside an electromagnetic coil. A current is passed through the coil to excite it, generating a magnetic force that creates a longitudinal magnetic field in the cable. When the cable tension changes, the magnetic flux through this magnetic field changes, causing a change in the output voltage. By measuring this output voltage, the change in cable tension can be determined. The electromagnetic coil typically consists of a measuring coil and an excitation coil, primarily used to magnetize the cable and sense and measure changes in its magnetic field. Compared to other methods such as the vibration frequency method, the magnetic flux monitoring method offers advantages such as high output power, strong signal, long service life, strong overload protection, good dynamic response, and minimal impact from wind loads, vibration, cable sheaths, and PE sheaths. It is suitable not only for static monitoring but also for dynamic cable tension monitoring and allows for long-term, real-time sampling, demonstrating promising future prospects. However, most research institutions at home and abroad have conducted online monitoring of cable stress from an experimental perspective. The tensile tests they have conducted are all based on low load stress conditions, which is inconsistent with the actual situation of cables being under high load stress conditions in practical applications. Applying the magnetic flux monitoring method currently being studied to the cable stress monitoring of in-service cables with large load stress is prone to large monitoring errors. Therefore, further research is needed.

[0006] In summary, while there has been considerable research on cable tension monitoring methods, these methods still have certain disadvantages or limitations in terms of accuracy and efficiency, or are not suitable for all working conditions. Summary of the Invention

[0007] In view of the shortcomings of existing technologies, the actual problem that this invention needs to solve is: how to provide a cable force monitoring system and method that can have high accuracy and efficiency in monitoring the cable force of in-service cables under different load stress conditions, so as to achieve accurate, real-time and low-cost monitoring of cable force.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0009] A cable tension monitoring system based on spontaneous leakage magnetic flux includes a monitoring device, a signal acquisition device, and a post-processing device;

[0010] The monitoring device is installed at a monitoring position on the cable to collect the magnetic field strength signal generated by spontaneous leakage magnetic field when the monitoring position of the cable is subjected to external magnetic field excitation under tensile stress.

[0011] The signal acquisition device is used to transmit the acquired magnetic field strength signal to the post-processing device;

[0012] The post-processing device is pre-set with a cable stress state monitoring model. The cable stress state monitoring model records the relationship between the magnetic field strength and the tensile stress magnitude after the cable is subjected to external magnetic field excitation under different tensile stress states and generates spontaneous leakage magnetic field. The post-processing device calculates the tensile stress of the cable at the monitoring position based on the magnetic field strength signal collected by the monitoring device and the cable stress state monitoring model, thereby obtaining the monitoring value of the cable stress.

[0013] In the above-mentioned cable tension monitoring system based on spontaneous leakage magnetic field, as a preferred embodiment, the monitoring device includes a monitoring cover mechanism, a support walking mechanism, and a displacement controller;

[0014] The monitoring cover mechanism is used to be fitted on the outer periphery of the cable monitoring position. It includes a magnetic shielding shell that is cylindrical in shape and a sleeve fitted and installed inside the magnetic shielding shell. A magnetic sensor for detecting magnetic field strength is fixedly installed on the inner wall of the sleeve. The magnetic sensor is also equipped with a signal transmitting device for transmitting the detected magnetic field strength signal to the outside.

[0015] The supporting walking mechanism is used to support the monitoring cover mechanism on the outer periphery of the cable and drive it to move on the cable; the supporting walking mechanism includes a rigid support that is fixedly installed at both ends of the monitoring cover mechanism in an integral ring shape, and a cable climbing wheel set is arranged on the inner ring surface of the rigid support, which can support the cable outer surface and drive the monitoring cover mechanism to move along the cable surface. The cable climbing wheel set is driven by a wheel set drive motor installed on the rigid support.

[0016] The displacement controller is electrically connected to the wheel drive motor mounted on the rigid support in the supporting walking mechanism. The displacement controller is equipped with a motor drive control circuit for driving and controlling the wheel drive motor.

[0017] In the above-mentioned cable tension monitoring system based on spontaneous leakage magnetic field, as a preferred embodiment, the signal transmitting device in the monitoring cover mechanism is a Bluetooth wireless transmitting module, which is used to transmit the magnetic field strength signal to the outside via Bluetooth communication.

[0018] In the above-mentioned cable tension monitoring system based on spontaneous leakage magnetic field, as a preferred embodiment, the signal acquisition device is a Bluetooth wireless transmission module, which is used to establish a Bluetooth communication connection with the signal transmitting device in the monitoring cover mechanism, receive the magnetic field strength signal collected by the monitoring device, and transmit it to the post-processing device.

[0019] In the above-mentioned cable force monitoring system based on spontaneous leakage magnetic field, as a preferred embodiment, the cable climbing wheel assembly in the support walking mechanism is mounted on the annular inner surface of the rigid support via an elastic rod. The elastic force of the elastic rod is radially along the annular inner surface of the rigid support, so that the cable climbing wheel assembly can contact the outer surface of the cable and provide support force under the action of the elastic force of the elastic rod.

[0020] In the above-mentioned cable tension monitoring system based on spontaneous leakage magnetic field, as a preferred embodiment, multiple sets of cable climbing wheels are arranged on the annular inner surface of the rigid support, and are evenly distributed along the circumference of the annular inner surface of the rigid support.

[0021] In the above-mentioned cable tension monitoring system based on spontaneous leakage magnetic field, as a preferred embodiment, the magnetic shielding shell of the monitoring cover mechanism is made of industrial pure iron or permalloy, and the sleeve is made of plastic, resin, glass or rubber.

[0022] In the above-mentioned cable tension monitoring system based on spontaneous leakage magnetic field, as a preferred embodiment, the post-processing device is a computer terminal that has been pre-set to store a cable tension state monitoring model, and its data acquisition end is communicatively connected to the data output end of the signal acquisition device.

[0023] In the above-mentioned cable tension monitoring system based on spontaneous leakage magnetic field, as a preferred embodiment, the expression of the cable tension state monitoring model is as follows:

[0024] σ = f(H - H0);

[0025] Wherein, σ is the tensile stress of the cable, H represents the magnetic field strength collected by the monitoring device after the cable generates spontaneous leakage magnetic field when it is under tensile stress σ and is excited by an external magnetic field, H0 represents the magnetic field strength collected by the monitoring device when the cable is under no-load and is excited by an external magnetic field, and f(H-H0) represents the correspondence between the magnetic field strength difference (H-H0) and the tensile stress σ of the cable.

[0026] A cable tension monitoring method based on spontaneous leakage magnetic flux, implemented using the aforementioned cable tension monitoring system, includes the following steps:

[0027] S1: Using a cable sample with the same material and radial dimensions as the cable to be monitored, apply external magnetic excitation to the cable sample according to the selected method;

[0028] S2: Using the cable force monitoring system, the monitoring device is fitted on the outer periphery of the cable sample to collect the magnetic field strength H0 of the cable sample under no-load conditions when it is subjected to external magnetic field excitation.

[0029] S3: Maintain external magnetic excitation on the cable sample and apply different external forces to the cable sample so that the cable sample is in different tensile stress states. Use a stress monitoring device to measure the tensile stress σ value of the cable sample under each different tensile stress state, and use the monitoring device of the cable force monitoring system to collect the magnetic field intensity H after the cable sample is subjected to external magnetic field excitation under each different tensile stress state and generates spontaneous leakage magnetic field.

[0030] S4: Statistically analyze the tensile stress σ and the corresponding magnetic field strength difference (H-H0) of the cable sample under various tensile stress states. Through data fitting, obtain the correspondence between the magnetic field strength σ=f(H-H0) after spontaneous leakage magnetic field is generated when the cable under different tensile stress states is subjected to external magnetic field excitation. This relationship is stored in the post-processing device of the cable force monitoring system as a cable force state monitoring model.

[0031] S5: Apply external magnetic excitation to the cable to be monitored using the same selected method, and use the cable force monitoring system to attach its monitoring device to the outer periphery of the monitoring position of the cable to be monitored. Collect the magnetic field strength H at the monitoring position of the cable under tensile stress and subjected to external magnetic field excitation, after spontaneous leakage magnetic field is generated. i The post-processing device uses the cable stress state monitoring model to calculate the tensile stress σ of the cable under monitoring at the monitoring location. i =f(H i -H0); For multiple different monitoring positions of the cable to be monitored, the monitoring device of the cable force monitoring system is moved to the monitoring position on the cable to be monitored, and the tensile stress of the cable to be monitored at each different monitoring position is monitored, thus completing the monitoring of the cable force of the cable to be monitored.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The cable force monitoring system of the present invention collects the magnetic field strength signal after the cable generates spontaneous leakage magnetic field when it is subjected to external magnetic field excitation under tensile stress. The signal is transmitted to the post-processing device through the signal acquisition device. The tensile stress of the cable at the monitoring position is calculated using the cable force state monitoring model, and then the monitoring value of the cable force is obtained. It uses the spontaneous leakage magnetic field monitoring principle when the cable is subjected to external magnetic field excitation. It can be applied under different load stresses on the cable. Even when the cable is in service, it can be directly applied without adjusting or disassembling the cable. The monitoring and calculation process is fast and efficient, and can ensure the accuracy of the cable force monitoring results. Therefore, it can have high accuracy and efficiency in monitoring the cable force of in-service cables under different load stress conditions, thereby effectively realizing accurate, real-time and low-cost monitoring of cable force.

[0034] 2. The cable force monitoring method of the present invention has very low requirements for monitoring operation, is very simple to operate, and can perform real-time cable force monitoring at different monitoring positions on the cable to be monitored by moving the monitoring device of the cable force monitoring system. It is very suitable for high-precision cable force monitoring of in-service cable structures. Attached Figure Description

[0035] To make the objectives, technical solutions, and advantages of the invention clearer, the invention will now be described in further detail with reference to the accompanying drawings, wherein:

[0036] Figure 1 This is a schematic diagram of the cable tension monitoring system based on spontaneous leakage magnetic field of the present invention;

[0037] Figure 2 This is a schematic diagram illustrating the working state of the cable tension monitoring method implemented using the cable tension monitoring system based on spontaneous leakage magnetic field of the present invention;

[0038] Figure 3 This is a flowchart of the cable tension monitoring method based on spontaneous leakage magnetic field of the present invention.

[0039] Explanation of reference numerals in the attached drawings: 1. Displacement controller; 2. Rigid support; 2-1. Climbing cable wheel assembly; 3. Magnetic shielding shell; 4. Sleeve; 5. Magnetic sensor; 6. Bluetooth wireless transmission module; 7. PC terminal; 8. Monitoring device; 9. Signal acquisition device; 10. Post-processing device. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but only to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0041] The present invention will now be described in further detail with reference to the accompanying drawings.

[0042] This invention provides a cable tension monitoring system based on spontaneous leakage magnetic field, such as... Figure 1 As shown, the device includes a monitoring device 8, a signal acquisition device 9, and a post-processing device 10. The monitoring device 8 is installed at a monitoring position on the cable to acquire the magnetic field strength signal generated by spontaneous leakage magnetic field when the cable is subjected to external magnetic field excitation under tensile stress. The signal acquisition device 9 transmits the acquired magnetic field strength signal to the post-processing device 10. The post-processing device 10 has a cable force state monitoring model pre-set and stored. This cable force state monitoring model records the correspondence between the magnetic field strength generated by spontaneous leakage magnetic field when the cable is subjected to external magnetic field excitation under different tensile stress states and the magnitude of tensile stress. Based on the magnetic field strength signal acquired by the monitoring device 8, the post-processing device 10 uses the cable force state monitoring model to calculate the tensile stress of the cable at the monitoring position, thereby obtaining the monitored value of the cable force.

[0043] This invention relates to a cable force monitoring system based on spontaneous leakage magnetic flux. The monitoring principle utilizes a force-magnetic coupling constitutive relationship to achieve cable force monitoring. The specific monitoring theory is as follows:

[0044] When an external magnetic excitation is applied, the ferromagnetic material of the cable spontaneously magnetizes and generates a self-induced magnetic field H. B At the same time, the cables are also affected by the Earth's magnetic field H. E The effect is that, in the unloaded state where no external force is applied to the cable, it is only affected by the Earth's magnetic field H. E and its own magnetic field H B Due to the influence of this, the magnetic signal H0 detected at this time is:

[0045] H0 = H E +H B (1)

[0046] Based on this, if the cable is subjected to an externally applied tensile force, causing it to be under tensile stress, the tensioned cable will undergo magnetostriction and magnetic domain reorientation to resist the increase in stress energy. Irreversible reorientation will occur, the magnetic domains will realign, the permeability will increase, and magnetic poles will form. This will cause some localized magnetic fields inside the cable material to spontaneously leak to the surface, forming small demagnetizing H-type structures on the cable surface. L Simultaneously, the greater the stress energy, the greater the stretching effect and the greater the degree of directional movement of magnetic domains within the cable to resist the increase in stress energy; that is, the magnetic signal H monitored at this time is:

[0047] H = H E +H B +H L (2)

[0048] In the formula: H L The demagnetizing field formed on the cable surface due to spontaneous leakage magnetic field after tensile stress is applied;

[0049] The final change in the leakage magnetic field of the cable caused by the applied tensile stress is:

[0050] H L =H-H0 (3)

[0051] The above principles can be summarized as follows: the stress non-destructive monitoring technology based on the spontaneous leakage magnetic field effect of metals is essentially a non-destructive monitoring method for studying the characteristics of leakage magnetic field signals on the surface of ferromagnetic materials under the coupling effect of weak magnetic field and stress field environment; through the established mechanical-magnetic coupling constitutive relationship, that is, the constitutive relationship between the internal magnetization of the material and the stress field under the external magnetic field, the stress magnetization behavior is quantitatively studied.

[0052] Based on the above-mentioned principles, if an external magnetic excitation is applied to the cable, and different external forces are applied to the cable sample to place it in different tensile stress states, the tensile stress σ of the cable under each different tensile stress state is measured. The magnetic field strength H of the cable sample under each different tensile stress σ state after spontaneous leakage magnetic field excitation is collected. Based on the magnetic field strength H0 of the cable under no-load conditions when subjected to external magnetic field excitation, the tensile stress σ and the corresponding magnetic field strength difference (H-H0) of the cable under each tensile stress state are statistically analyzed. Through data fitting, the relationship between the magnetic field strength after spontaneous leakage magnetic field excitation under different tensile stress states and the magnitude of the tensile stress σ = f(H-H0) can be obtained, which can be used as the cable force state. The cable force monitoring system based on spontaneous leakage magnetic flux provided by this invention can be used to calculate the tensile stress of the cable using the cable force state monitoring model, thereby implementing cable force monitoring. Furthermore, since the above technical principles hold true under different load stresses on the cable, and even when the cable is in service, it can be directly applied without adjusting or disassembling the cable, the monitoring and calculation process is fast and efficient. The cable force state monitoring model σ=f(H-H0) determined by data fitting can also ensure the accuracy of the cable force monitoring results. Therefore, the cable force monitoring system of this invention can achieve high accuracy and efficiency in monitoring the cable force under different load stress conditions for in-service cables, thus effectively realizing accurate, real-time, and low-cost monitoring of cable force.

[0053] In practical applications, there are various ways to apply external magnetic excitation to the cable. For example, a magnetic excitation winding can be wound around the cable, or permanent magnets can be arranged on the cable. The purpose is to make the cable generate magnetism under the action of magnetic excitation.

[0054] In practical applications, this invention is used in cable tension monitoring systems based on spontaneous leakage magnetic flux, such as... Figure 1As shown, the monitoring device 8 can be designed to include a monitoring cover mechanism, a support and walking mechanism, and a displacement controller 1. The monitoring cover mechanism is used to be fitted onto the outer periphery of the cable monitoring position. It includes a cylindrical magnetic shielding shell 3 and a sleeve 4 fitted inside the magnetic shielding shell 3. A magnetic sensor 5 for detecting magnetic field strength is fixedly installed on the inner wall of the sleeve 4. The magnetic sensor 5 is also equipped with a signal transmitting device for transmitting the detected magnetic field strength signal. The support and walking mechanism supports the monitoring cover mechanism on the outer periphery of the cable and drives it to move along the cable. The support and walking mechanism includes a rigid support 2 fixedly installed at both ends of the monitoring cover mechanism, forming an annular shape. A cable-climbing wheel set 2-1 is arranged on the annular inner surface of the rigid support 2, capable of supporting the outer surface of the cable and driving the monitoring cover mechanism to move along the cable surface. The cable-climbing wheel set 2-1 is driven by a wheel drive motor mounted on the rigid support 2. Figure 1 (Not shown in the image); The displacement controller 1 is electrically connected to the wheel drive motor mounted on the rigid support 2 in the support walking mechanism. The displacement controller 1 is equipped with a motor drive control circuit, which is used to drive and control the wheel drive motor, thereby controlling the climbing cable walking wheel group 2-1 to perform actions, so that the support walking mechanism drives the monitoring cover mechanism to move on the cable, and monitors different monitoring positions.

[0055] In this way, when monitoring the cable, the monitoring device 8 is set outside the cable, and the magnetic shielding shell 3 is used to form a magnetic vacuum area in the area where the magnetic shielding shell 3 is located, thereby reducing the influence of the external magnetic field on the magnetic sensor 5 inside the sleeve 4 to monitor the magnetic signal of the cable itself; the magnetic sensor 5 monitors and collects the magnetic field strength signal and then outputs it to the signal transmitting device, which transmits the collected magnetic field strength signal to the outside. The signal acquisition device receives the signal and transmits it to the post-processing device 10 for conversion and processing to obtain the monitoring value of the cable force.

[0056] In practice, the rigid support 2, the magnetic shielding shell 3, and the sleeve 4 should preferably adopt an openable and closable structural design to make it easier to install them onto the outer surface of the cable.

[0057] The rigid support 2 in the supporting walking mechanism needs to be made of a rigid material, such as alloy material, rigid plastic, rigid chemical composite material, etc., to provide structural support.

[0058] The magnetic shielding shell 3 is preferably made of a material with a large maximum magnetic permeability and saturation magnetic flux density, such as industrial pure iron or permalloy, and such materials or structural forms are all within the protection scope of this invention.

[0059] The sleeve 4 is preferably made of a non-metallic material with a relative magnetic permeability of approximately 1, such as plastic, resin, glass, rubber, etc., all of which are within the protection scope of this invention.

[0060] In the supporting walking mechanism, it is best to design and arrange multiple sets of climbing cable walking wheel sets 2-1 on the inner annular surface of the rigid support 2. These multiple sets of climbing cable walking wheel sets 2-1 are preferably evenly distributed circumferentially along the inner annular surface of the rigid support 2. This provides evenly distributed circumferential support force and crawling movement power on the outer surface of the cable, which is more conducive to the smooth movement of the entire monitoring mechanism 8 on the outer surface of the cable. The climbing cable walking wheel sets 2-1 preferably adopt a tracked wheel structure, which can provide better adhesion to the outer surface of the cable. Meanwhile, as a preferred improvement, the climbing wheel assembly 2-1 in the supporting walking mechanism can be designed to be mounted on the inner annular surface of the rigid support 2 via an elastic rod. The elastic force of the elastic rod is radial along the inner annular surface of the rigid support 2, allowing the climbing wheel assembly 2-1 to contact the outer surface of the cable under the action of the elastic rod and provide support force. In this way, by setting the elastic rod, the climbing wheel assembly 2-1 has a large contact support force with the cable under the action of the elastic rod, further ensuring reliable contact and sufficient driving force between the climbing wheel assembly 2-1 and the cable during movement. This allows the entire monitoring mechanism 8 to move more smoothly on the outer surface of the cable and has a certain buffer support capacity to resist the undulations of the outer surface of the cable.

[0061] In the monitoring housing mechanism, the signal transmitting device of the magnetic sensor 5 preferably adopts a Bluetooth wireless transmitting module to transmit the magnetic field strength signal externally via Bluetooth communication. Using wireless transmission avoids the limitations caused by wired connections in wired communication, and Bluetooth communication is less susceptible to magnetic interference. Therefore, using a Bluetooth wireless transmitting module for Bluetooth wireless communication can minimize the adverse effects of magnetic field signals on wireless data communication transmission.

[0062] Correspondingly, if the signal transmitting device of the magnetic sensor 5 preferably adopts a Bluetooth wireless transmitting module, the signal acquisition device 9 should also preferably adopt a Bluetooth wireless transmission module to establish a Bluetooth communication connection with the signal transmitting device in the monitoring cover mechanism, receive the magnetic field strength signal collected by the monitoring device 8, and transmit it to the post-processing device 10.

[0063] The subsequent processing device can be a PC terminal (computer terminal) in specific implementation. The fitted cable force state monitoring model is pre-set and stored on the PC terminal. The data acquisition end of the PC terminal (such as the data acquisition card port) is connected to the data output end of the signal acquisition device to receive the data transmitted by the signal acquisition device.

[0064] A schematic diagram illustrating the working state of the cable tension monitoring method implemented using the self-generated leakage magnetic field-based cable tension monitoring system of this invention is shown below. Figure 2As shown, by moving the monitoring device of the cable tension monitoring system of the present invention between different monitoring positions on the outer surface of the cable (the cable PE sheath), the tensile stress at different monitoring positions of the cable can be monitored separately; the flow of the cable tension monitoring method is as follows: Figure 3 As shown, it includes the following steps:

[0065] S1: Using a cable sample with the same material and cross-sectional radial dimensions (diameter or side length) as the cable to be monitored, apply external magnetic excitation to the cable sample in a selected manner (e.g., by winding a magnetic excitation winding on the cable or arranging permanent magnets on the cable, so that the cable interior generates magnetism under the action of magnetic excitation).

[0066] S2: Using the cable force monitoring system of the present invention, the monitoring device is sleeved on the outer periphery of the cable sample to collect the magnetic field strength H0 when the cable sample is subjected to external magnetic field excitation in an unloaded state without external force applied.

[0067] S3: Maintain external magnetic excitation on the cable sample and apply different external forces to the cable sample so that the cable sample is in different tensile stress states. Use a stress monitoring device to measure the tensile stress σ value of the cable sample in each different tensile stress state, and use the monitoring device of the cable force monitoring system of the present invention to collect the magnetic field intensity H after the cable sample is subjected to external magnetic field excitation in each different tensile stress state and generates spontaneous leakage magnetic field.

[0068] S4: Statistically analyze the tensile stress σ and the corresponding magnetic field strength difference (H-H0) of the cable sample under various tensile stress states. Through data fitting, obtain the correspondence between the magnetic field strength and the tensile stress magnitude σ=f(H-H0) after spontaneous leakage magnetic field is generated when the cable under different tensile stress states is subjected to external magnetic field excitation. Store this as a cable force state monitoring model in the post-processing device of the cable force monitoring system of the present invention.

[0069] S5: Apply external magnetic excitation to the cable to be monitored in the same selected manner, and use the cable force monitoring system of the present invention to cover the monitoring device on the outer periphery of the monitoring position of the cable to be monitored, and collect the magnetic field strength H at the monitoring position of the cable to be monitored after spontaneous leakage magnetic field is generated when the cable is under tensile stress and subjected to external magnetic field excitation. i The post-processing device uses the cable stress state monitoring model to calculate the tensile stress σ of the cable under monitoring at the monitoring location. i =f(H i-H0); For multiple different monitoring positions of the cable to be monitored, by moving the monitoring device of the cable force monitoring system of the present invention to the monitoring position on the cable to be monitored, the tensile stress of the cable to be monitored at each different monitoring position is monitored, and the cable force of the cable to be monitored is completed.

[0070] As can be seen from the above cable force monitoring method, steps S1 to S4 are preparatory steps before implementing cable force monitoring for the cable to be monitored, with the aim of obtaining the cable force state monitoring model σ=f(H-H0). After that, the monitoring operation requirements of step S5, the cable force monitoring step of the cable to be monitored, are very low, the operation is very simple, and the cable force can be monitored in real time at different monitoring positions on the cable to be monitored by moving the monitoring device of the cable force monitoring system. It is very suitable for high-precision cable force monitoring of in-service cable structures.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A cable tension monitoring system based on spontaneous leakage magnetic flux, characterized in that, Includes monitoring devices, signal acquisition devices, and post-processing devices; The monitoring device is installed at a monitoring position on the cable to collect the magnetic field strength signal generated by spontaneous leakage magnetic field when the monitoring position of the cable is subjected to external magnetic field excitation under tensile stress. The signal acquisition device is used to transmit the acquired magnetic field strength signal to the post-processing device; The post-processing device is pre-set with a cable stress state monitoring model. The cable stress state monitoring model records the relationship between the magnetic field strength and the tensile stress magnitude after the cable is subjected to external magnetic field excitation under different tensile stress states and generates spontaneous leakage magnetic field. The post-processing device calculates the tensile stress of the cable at the monitoring position based on the magnetic field strength signal collected by the monitoring device and the cable stress state monitoring model, thereby obtaining the monitoring value of the cable stress. The monitoring device includes a monitoring cover mechanism, a support and walking mechanism, and a displacement controller. The monitoring cover mechanism is fitted onto the outer periphery of the cable monitoring position and includes a cylindrical magnetic shielding shell and a sleeve fitted inside the magnetic shielding shell. A magnetic sensor for detecting magnetic field strength is fixedly installed on the inner wall of the sleeve, and the magnetic sensor is also equipped with a signal transmitting device for transmitting the detected magnetic field strength signal. The support and walking mechanism supports the monitoring cover mechanism on the outer periphery of the cable and drives it to move on the cable. The support and walking mechanism includes a rigid, annular support fixedly installed at both ends of the monitoring cover mechanism. A cable-climbing wheel set is arranged on the annular inner surface of the rigid support, which can support the outer surface of the cable and drive the monitoring cover mechanism to move along the cable surface. The cable-climbing wheel set is driven by a wheel set drive motor mounted on the rigid support. The displacement controller is electrically connected to the wheel set drive motor mounted on the rigid support in the support and walking mechanism. The displacement controller is equipped with a motor drive control circuit for driving and controlling the wheel set drive motor. The cable-climbing wheel assembly in the supporting walking mechanism is mounted on the inner annular surface of the rigid support via an elastic rod. The elastic force of the elastic rod is radially along the inner annular surface of the rigid support, allowing the cable-climbing wheel assembly to contact the outer surface of the cable and provide support under the action of the elastic force of the elastic rod. Multiple sets of cable-climbing wheel assemblies are arranged on the inner annular surface of the rigid support and are evenly distributed circumferentially along the inner annular surface of the rigid support. The expression for the cable stress state monitoring model is: ； in, This indicates the tensile stress in the cable. This indicates that the cable is under tensile stress. The magnetic field strength collected by the monitoring device after spontaneous leakage magnetic field is generated when the magnetic field is excited by an external magnetic field in a certain state. This indicates the magnetic field strength collected by the monitoring device when the cable is subjected to an external magnetic field excitation under no-load conditions. Indicates the difference in magnetic field strength With the tensile stress of the cable The correspondence between them.

2. The cable tension monitoring system based on spontaneous leakage magnetic field according to claim 1, characterized in that, The signal transmitting device in the monitoring cover mechanism is a Bluetooth wireless transmitting module, which is used to transmit the magnetic field strength signal to the outside via Bluetooth communication.

3. The cable tension monitoring system based on spontaneous leakage magnetic field according to claim 2, characterized in that, The signal acquisition device is a Bluetooth wireless transmission module, used to establish a Bluetooth communication connection with the signal transmitting device in the monitoring cover mechanism, receive the magnetic field strength signal collected by the monitoring device, and transmit it to the post-processing device.

4. The cable tension monitoring system based on spontaneous leakage magnetic field according to claim 1, characterized in that, In the monitoring cover mechanism, the magnetic shielding shell is made of industrial pure iron or permalloy, and the sleeve is made of plastic, resin, glass or rubber.

5. The cable tension monitoring system based on spontaneous leakage magnetic field according to claim 1, characterized in that, The post-processing device is a computer terminal that has been pre-set to store a cable force state monitoring model, and its data acquisition end is connected to the data output end of the signal acquisition device.

6. A method for monitoring cable tension based on spontaneous leakage magnetic flux, characterized in that, The implementation using the cable tension monitoring system as described in claim 1 includes the following steps: S1: Using a cable sample with the same material and radial dimensions as the cable to be monitored, apply external magnetic excitation to the cable sample according to the selected method; S2: Using the aforementioned cable force monitoring system, the monitoring device is fitted onto the outer periphery of the cable sample to collect the magnetic field strength of the cable sample under unloaded conditions when it is subjected to external magnetic field excitation. ; S3: Maintain external magnetic excitation on the cable sample and apply different external forces to subject the cable sample to different tensile stress states. Use a stress monitoring device to measure the tensile stress of the cable sample under each different tensile stress state. The value of the magnetic field strength was collected by the monitoring device of the cable force monitoring system when the cable sample was subjected to external magnetic field excitation under different tensile stress states, and the magnetic field strength after spontaneous leakage magnetic field was generated was collected. ; S4: Statistical analysis of tensile stress in cable samples under various tensile stress states. and the corresponding magnetic field strength difference By fitting data, the relationship between the magnetic field strength and the magnitude of the tensile stress was obtained when the monitored cable was subjected to an external magnetic field excitation under different tensile stress states and generated spontaneous leakage magnetic field. The cable tension monitoring system's post-processing device stores the cable tension status monitoring model as a cable tension state monitoring model. S5: Apply external magnetic excitation to the cable to be monitored using the same selected method, and use the cable force monitoring system to attach its monitoring device to the outer periphery of the monitoring position of the cable to be monitored. Collect the magnetic field strength at the monitoring position of the cable under tensile stress and subjected to external magnetic field excitation, after spontaneous leakage magnetic field is generated. The post-processing device uses the cable stress monitoring model to calculate the tensile stress of the cable under monitoring at the monitoring location. For multiple different monitoring positions of the cable to be monitored, the monitoring device of the cable force monitoring system is moved to the monitoring position on the cable to be monitored, and the tensile stress of the cable to be monitored at each different monitoring position is monitored, thus completing the monitoring of the cable force of the cable to be monitored.

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