Online resistance testing system for oxygen-free copper rod

Abstract

The invention relates to the technical field of copper rod production, in particular to an oxygen-free copper rod on-line resistance test system, which comprises a resistance detection unit used for sensing magnetic field intensity data generated by internal current of a copper rod and calculating the resistivity of a copper rod body according to the magnetic field intensity data; the multi-physical field data acquisition unit comprises a temperature field detection module and a stress field detection module which are used for respectively detecting copper rod temperature distribution data and copper rod mechanical stress data; the dynamic compensation unit is used for receiving the temperature distribution data and the mechanical stress data, dynamically compensating the influence of temperature and strain on the resistivity of the copper rod body through a preset multi-physical field coupling model, and taking the compensated body resistivity as an online resistance test result of the oxygen-free copper rod; the real resistance performance of the oxygen-free copper rod under the actual production condition can be measured more accurately, and the accuracy of the measurement result is improved.

Description

Technical Field

[0001] The invention relates to the technical field of copper rod production, in particular to an oxygen-free copper rod online resistance testing system. Background Art

[0002] As a high-purity conductive material (copper content ≥99.99%), oxygen-free copper rod's DC resistance is a key indicator of its electrical conductivity, directly impacting the energy transmission efficiency of downstream products such as wires and cables, and electronic devices. Traditional resistance testing methods primarily include the laboratory four-probe method and eddy current testing.

[0003] Among them, the four-probe method requires physical contact with the surface of the copper rod, which means that the speed must be reduced or the machine must be stopped during measurement, which seriously restricts production efficiency. At the same time, uneven contact pressure will cause surface scratches, affecting the quality of the finished product; and the eddy current detection method is limited by the skin effect and can only reflect the resistance characteristics of the copper rod surface. When the copper rod has internal grain boundary oxidation and micropore defects, the surface measurement value cannot represent the true bulk resistivity of the material, resulting in quality misjudgment. Summary of the Invention

[0004] The present invention provides an oxygen-free copper rod online resistance testing system that can more accurately measure the true resistance performance of an oxygen-free copper rod under actual production conditions and improve the accuracy of the measurement results, and can effectively solve the problems in the background technology.

[0005] In order to achieve the above object, the present invention provides an oxygen-free copper rod online resistance testing system, comprising:

[0006] The resistance detection unit is used to sense the magnetic field strength data generated by the current inside the copper rod and calculate the resistivity of the copper rod based on this data;

[0007] A multi-physics field data acquisition unit, including a temperature field detection module and a stress field detection module, is used to detect the temperature distribution data and mechanical stress data of the copper rod respectively;

[0008] A dynamic compensation unit is used to receive the temperature distribution data and the mechanical stress data, dynamically compensate for the influence of temperature and strain on the resistivity of the copper rod through a preset multi-physics field coupling model, and use the compensated body resistivity as the oxygen-free copper rod online resistance test result.

[0009] In combination with the first aspect, in a possible design, the resistance detection unit uses a plurality of superconducting magnetic sensors based on flux quantization effect arranged axially along the copper rod transmission path to sense the magnetic field intensity generated by the current inside the copper rod.

[0010] In combination with the first aspect, in a possible design, the superconducting magnetic sensor is a superconducting quantum interference device, which includes at least one Josephson junction and a superconducting loop.

[0011] In combination with the first aspect, in a possible design, an electromagnetic shielding cover is provided on the outside of the superconducting magnetic sensor, and an absorbing material layer is provided on the inner wall of the electromagnetic shielding cover to reduce interference of external magnetic fields and external electromagnetic waves on the measurement of the superconducting magnetic sensor.

[0012] In combination with the first aspect, in a possible design, a magnetic flux focuser is provided between the superconducting quantum interference device and the copper rod to enhance the magnetic field capturing capability of the superconducting quantum interference device.

[0013] In combination with the first aspect, in a possible design, the magnetic flux focuser is composed of a permalloy conical cavity, and the cone angle of the conical cavity satisfies:

[0014] tanθ=μ r (d / L);

[0015] Where θ represents the cone angle of the conical cavity; μ r is the relative magnetic permeability, d is the copper rod diameter, and L is the sensor spacing.

[0016] In combination with the first aspect, in a possible design, a calibration unit is also included, which is used to automatically push the standard resistance rod into the measurement area during the intermittent movement phase of the copper rod and perform zero-point calibration on the resistance detection unit and the multi-physics field data acquisition unit.

[0017] In combination with the first aspect, in a possible design, the stress field detection module uses a fiber Bragg grating sensor group, and the fiber Bragg grating sensor group is embedded in the copper rod transmission guide wheel for measuring the mechanical stress data of the copper rod in real time.

[0018] In combination with the first aspect, in a possible design, it further includes a wireless transmission unit, which uses the movement energy of the copper rod to generate electricity for data transmission, and sends the online resistance test result of the oxygen-free copper rod to an external terminal.

[0019] In combination with the first aspect, in a possible design, the wireless transmission unit includes a piezoelectric device and a wireless communication module. By arranging the piezoelectric device on both sides of the copper rod, radial vibration of the copper rod during transmission is used to generate electricity to power the wireless communication module.

[0020] The technical solution of the present invention can achieve the following technical effects:

[0021] This system uses a resistance detection unit to non-contactly sense the current and magnetic field within the copper rod, directly acquiring its bulk resistivity and avoiding contact damage and surface detection blind spots. Simultaneously, a multi-physics data acquisition unit monitors temperature distribution and mechanical stress in real time, while a dynamic compensation unit uses a multi-physics coupling model to correct for temperature / strain interference with resistivity. This combination enables the system to continuously detect copper rods without stopping or slowing down the production process, while also penetrating the surface and eliminating environmental variables. This allows for more precise measurement of the true resistivity of oxygen-free copper rods under actual production conditions, improving the accuracy of measurement results. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a structural block diagram of the oxygen-free copper rod online resistance testing system of the present invention. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0024] The present application is described below in conjunction with the accompanying drawings.

[0025] like Figure 1 As shown, the oxygen-free copper rod online resistance testing system of the present invention specifically includes the following modules:

[0026] The resistance detection unit is used to sense the magnetic field strength data generated by the current inside the copper rod and calculate the resistivity of the copper rod based on this data;

[0027] A multi-physics field data acquisition unit, including a temperature field detection module and a stress field detection module, is used to detect the temperature distribution data and mechanical stress data of the copper rod respectively;

[0028] The dynamic compensation unit is used to receive temperature distribution data and mechanical stress data, dynamically compensate for the influence of temperature and strain on the resistivity of the copper rod through a preset multi-physics field coupling model, and use the compensated body resistivity as the online resistance test result of the oxygen-free copper rod.

[0029] In this embodiment, the traditional four-probe method relies on physical contact, which requires speed reduction / stoppage during detection, and the contact stress may damage the surface of the copper rod. The eddy current method is limited by the skin effect and can only reflect the surface resistance characteristics. The present system uses a resistance detection unit to sense the current magnetic field inside the copper rod in a non-contact manner to directly obtain the bulk resistivity, avoiding contact damage and surface detection blind spots. At the same time, the multi-physics field data acquisition unit monitors the temperature distribution and mechanical stress in real time, and the dynamic compensation unit corrects the interference of temperature / strain on the resistivity through a multi-physics field coupling model. The combination of these three enables the system to not only perform continuous detection without stopping or slowing down the copper rod production process, but also penetrate the surface and eliminate environmental variables, and can more accurately measure the true resistance performance of the oxygen-free copper rod under actual production conditions, thereby improving the accuracy of the measurement results.

[0030] The resistivity of oxygen-free copper rods is dynamically affected by factors such as temperature and mechanical stress. For example, the temperature gradient and tensile stress in the drawing and cooling stages of the production process will lead to measurement deviations if traditional methods do not compensate for these variables. The system captures the copper rod state parameters in real time through the temperature field detection module and the stress field detection module. Combined with the multi-physics field coupling model of the dynamic compensation unit, the nonlinear relationship between temperature-resistivity and strain-resistivity is embedded in the algorithm. For example, when it is detected that the temperature of a certain section of the copper rod rises due to uneven cooling, the model automatically reduces the weight of the positive influence of temperature on resistivity. When the stress field detection module finds abnormal tensile stress, it corrects the interference of lattice distortion on the mobility of conductive electrons, so that the system can still output stable and reliable bulk resistivity data in complex production environments (such as temperature fluctuations and mechanical vibrations), solving the problem that a single detection unit cannot cope with multi-variable interference.

[0031] In some preferred embodiments, a superconducting magnetic sensor based on the flux quantization effect is used to sense the magnetic field strength generated by the current inside the copper rod; the superconducting magnetic sensor based on the flux quantization effect has ultra-high sensitivity and can non-contactly sense the magnetic field generated by the current inside the copper rod. Combined with the axial arrangement design, it can cover the magnetic field distribution detection along the entire length of the copper rod, solving the problems of contact damage and surface limitations of traditional methods.

[0032] Specifically, conductive fixtures are set at the input and output ends of the copper rod transmission path. The fixtures are made of low-resistance conductive materials, such as silver-plated copper alloy, and are in close contact with both ends of the copper rod. It is important to note that non-pressure contact is required to avoid surface damage. The conductive fixtures are connected to a high-precision constant current source through a wire. The constant current source provides a DC current, such as 10A to 100A, which is adjusted according to the cross-sectional area of the copper rod to ensure uniform current density. When the current flows inside the copper rod, a circular magnetic field is generated.

[0033] Directly above and below the copper rod transmission path, 2-4 groups of superconducting magnetic sensors are symmetrically arranged axially at intervals of 50-100 cm. Each sensor group contains a magnetic field sensing probe, with the probe axis perpendicular to the copper rod axis to ensure that the magnetic field distribution covers the entire cross-section of the copper rod. The superconducting magnetic sensors are fixed to the production line frame using insulating brackets. The brackets are height-adjustable to accommodate copper rods of different diameters and maintain a distance of 5-10 cm from the copper rod surface to avoid mechanical interference while meeting magnetic field penetration requirements.

[0034] According to Ampere's loop theorem, the magnetic field intensity H generated by the current I inside the copper rod satisfies ∮H·dl=I; the superconducting magnetic sensor collects the circumferential magnetic field component H of the copper rod in real time. φ , the total cross-sectional current is obtained by integration: I=2πrH φ , where r is the radius of the copper rod;

[0035] Combined with the length L and cross-sectional area S of the copper rod, using the resistance formula R = ρL / S and R = U / I, where U is the voltage across the copper rod, which can be obtained by a high-precision constant current source connected to the conductive fixture, the reverse calculation formula for the body resistivity is: ρ = RS / L = (US) / (2πrH φ L).

[0036] In this embodiment, there is no need to physically contact the surface of the copper rod, which avoids the contact pressure damage and shutdown and speed reduction problems of the four-probe method. Real-time online detection can be achieved when the copper rod moves at high speed, and the risk of surface scratches is completely eliminated, thereby ensuring the appearance quality of the finished product. Unlike the eddy current detection method, the resistivity is calculated by detecting the magnetic field generated by the internal current, which can more realistically reflect the overall conductive performance of the copper rod. Even if there are grain boundary oxidation, micropore defects, etc. inside the copper rod, they can be accurately detected, avoiding quality misjudgment. Multiple sensors are arranged along the axial direction to obtain magnetic field data from different sections of the copper rod. Spatial filtering algorithms (such as sliding average and Kalman filtering) are used to filter out accidental noise (such as short-term mechanical vibration and local electromagnetic interference), making the measurement results more stable. Furthermore, by comparing the detection data of different sensors, the specific location of the resistivity anomaly can be located, such as the local stress concentration section caused by drawing die wear, providing precise guidance for process optimization.

[0037] More specifically, the superconducting magnetic sensor is a superconducting quantum interference device, comprising at least one Josephson junction and a superconducting loop, specifically:

[0038] A Josephson junction consists of two layers of superconducting material with an extremely thin insulating layer sandwiched between them. When a superconducting current passes through the Josephson junction, quantum tunneling occurs, forming a Josephson current. The Josephson current is related to the superconducting phase difference on both sides of the junction and is modulated by an applied magnetic field. This property of the Josephson junction enables it to respond to even small changes in the magnetic field.

[0039] A superconducting loop is a closed circuit made of superconducting materials. When magnetic flux passes through this loop, according to the magnetic flux quantization effect, the magnetic flux can only be Φ0 = 2.068 × 10 -15 Integer multiples of Wb; the superconducting loop and Josephson junction in the superconducting quantum interference device cooperate with each other. When the external magnetic field changes, causing the magnetic flux passing through the loop to change, the superconducting current in the loop will change accordingly, thereby affecting the output of the Josephson junction;

[0040] In this practical application, a superconducting quantum interference device is placed close to a copper rod so that it can sense the magnetic field generated by the current inside the copper rod. When current flows through the copper rod, a circular magnetic field is generated, which acts on the superconducting loop of the superconducting quantum interference device. The magnetic flux in the superconducting loop changes, which in turn causes the output current of the Josephson junction to change. By detecting the change in the Josephson junction output current, the strength of the magnetic field generated by the current inside the copper rod can be indirectly measured.

[0041] In this embodiment, the superconducting quantum interference device uses the magnetic flux quantization effect and the Josephson effect to detect extremely weak magnetic field changes, and its magnetic field resolution can reach 10-1. 5 The device can accurately sense the weak magnetic field generated by the current inside the copper rod, improving the accuracy of resistance detection. The superconducting quantum interference device can operate within a wide frequency range and can adapt to the changes in the magnetic field generated by the current inside the copper rod under different working conditions. Whether it is a low-frequency steady-state current magnetic field or a high-frequency dynamic current magnetic field, the superconducting quantum interference device can accurately detect it, ensuring the comprehensiveness and accuracy of resistance detection. At the same time, due to the special structure and working principle of the Josephson junction and superconducting loop, the superconducting quantum interference device has an extremely low noise level. This allows it to effectively suppress interference from external noise when detecting weak magnetic fields, improve the signal-to-noise ratio of the signal, and further ensure the reliability of the measurement results.

[0042] In some embodiments of the present invention, the superconducting quantum interference device serves as the core sensor of the resistance detection unit, and its measurement accuracy is extremely susceptible to interference from external magnetic fields and electromagnetic waves. In the oxygen-free copper rod production environment, there are multiple interference sources: electrical equipment around the production line (such as welding machines and inverters) generates high-intensity low-frequency magnetic fields; high-frequency electromagnetic waves come from wireless communication equipment, motor drivers, etc. The above interference can cause noise and drift in the output signal of the superconducting quantum interference device, directly affecting the accuracy of the bulk resistivity calculation. Therefore, an electromagnetic shielding cover is provided on the outside of the superconducting magnetic sensor, and the inner wall of the electromagnetic shielding cover is provided with an absorbing material layer to reduce the interference of external magnetic fields and external electromagnetic waves on the superconducting magnetic sensor measurement.

[0043] Specifically, an electromagnetic shielding cover is made of high-permeability μ metal (such as Permalloy) with a thickness of 1 mm. μ metal has unique magnetic properties. In a low-frequency magnetic field environment, its magnetic permeability is very high, which can effectively guide and absorb external magnetic fields, preventing them from entering the shielding cover and interfering with the superconducting quantum interference device. The electromagnetic shielding cover is tightly installed on the outside of the superconducting magnetic sensor, ensuring that there is no gap between the shielding cover and the sensor to prevent external magnetic fields from entering through the gap. The shape of the shielding cover is designed to fit the shape of the sensor to maximize the coverage of the sensor and improve the shielding effect.

[0044] The inner layer is coated with graphene-based absorbing material or carbon-based nano-absorbing coating with a thickness of 0.1 to 1 mm. The high conductivity and broadband absorbing properties of graphene can effectively absorb high-frequency electromagnetic waves in the range of 100 MHz to 10 GHz, preventing them from reflecting inside the shielding cover to form standing wave interference; the bonding process uses high-temperature resistant adhesives to evenly stick the absorbing material to the inner wall of the shielding cover to ensure that there are no bubbles or gaps, forming a continuous electromagnetic wave absorption interface.

[0045] In this embodiment, by providing an electromagnetic shielding cover on the outside of the superconducting magnetic sensor and adding a layer of absorbing material on the inner wall, the anti-interference ability of the superconducting magnetic sensor measurement can be significantly improved. On the one hand, the external magnetic field is effectively shielded, ensuring that the magnetic field signal sensed by the superconducting magnetic sensor mainly comes from the internal current of the oxygen-free copper rod, thereby improving the purity of the magnetic field strength data. On the other hand, the absorbing material absorbs electromagnetic waves, reduces electromagnetic signal interference, makes the measurement data more stable and reliable, and helps to accurately calculate the resistivity of the copper rod body, thereby ensuring the measurement accuracy of the oxygen-free copper rod online resistance test system.

[0046] In some embodiments of the present invention, although the superconducting quantum interference device has extremely high magnetic field sensitivity, its effective capture area is limited. In actual detection, the circular magnetic field generated by the current inside the copper rod will rapidly decay with increasing distance, resulting in a weak magnetic field signal received by the superconducting quantum interference device far away from the copper rod. In particular, when the sensor spacing L is large, the attenuation of the magnetic field intensity causes the measurement error to exceed ±1%. In addition, the copper rod, as a cylindrical conductor, generates a circular magnetic field with complex directionality, requiring a special structure to directionally enhance and focus the magnetic field. The permalloy-based flux focuser, through its unique conical cavity design, can converge scattered magnetic flux lines to the sensitive area of the superconducting quantum interference device, thereby improving the magnetic field capture efficiency.

[0047] Specifically, the magnetic flux focuser is made of high-purity Permalloy processed into a conical cavity, and the relative magnetic permeability μ of the Permalloy is r =1000-10000, the cone angle θ of the conical cavity is calculated as follows: tanθ=μ r (d / L); where θ represents the cone angle of the conical cavity; μ ris the relative magnetic permeability, d is the copper rod diameter, and L is the sensor spacing. For example, when the copper rod diameter d = 8 mm and the sensor spacing L = 50 cm, θ ≈ 4.57°. The opening diameter of the large end of the conical cavity is 2-3 times the diameter of the copper rod, and the small end is tightly fitted with the plane of the superconducting quantum interference device induction coil to ensure that the magnetic flux lines have no leakage transition.

[0048] The flux focuser's Permalloy alloy undergoes vacuum heat treatment to eliminate internal stress, and the surface is nickel-plated to prevent oxidation. The inner wall of the cavity is mirror-polished to reduce hysteresis loss and improve magnetic conductivity. A three-point mechanical support structure is used, and laser positioning is used to ensure that the overlap between the conical cavity axis and the copper rod center axis is ≤0.05mm. It is equipped with a temperature compensation mechanism that automatically adjusts the cavity spacing when the operating temperature deviates from 77K to compensate for changes in geometric parameters caused by thermal expansion.

[0049] In this embodiment, the flux focuser's converging effect on the magnetic field enables the superconducting quantum interference device to capture a stronger effective magnetic field signal, thereby more accurately measuring the magnetic field strength generated by the current inside the oxygen-free copper rod, effectively avoiding measurement errors caused by weak magnetic field signals, and improving the measurement accuracy of the resistance testing system; by converging the target magnetic field, the impact of external interference magnetic fields on the measurement is reduced, and measurement fluctuations caused by environmental factors are reduced, so that the entire resistance testing system can maintain stable operation under different working conditions, thereby improving the reliability and stability of the system; based on the cone angle determined by formula calculation, the flux focuser can be customized according to oxygen-free copper rods of different diameters and sensor spacing, and can be flexibly adapted to copper rod specifications in various production scenarios, thereby enhancing the versatility and applicability of the resistance testing system.

[0050] Furthermore, during the online resistance test of the oxygen-free copper rod, the resistance detection unit and the multi-physics field data acquisition unit will drift due to the influence of various factors. For example, the superconducting loop of the superconducting quantum interference device is easily disturbed by the fluctuation of the environmental magnetic field, the temperature sensor may drift due to long-term high-temperature operation, and the fiber grating of the stress sensor may undergo slight deformation due to mechanical vibration. The above drift will cause the measurement reference to change, resulting in systematic errors in the resistivity calculation results. The traditional offline calibration method requires shutdown operation, which seriously affects production efficiency. Therefore, it is necessary to design an online calibration mechanism that can be automatically executed during the intermittent motion stage of the copper rod to ensure the long-term stability and accuracy of the measurement system.

[0051] Specifically, a pneumatic push rod device is used, and its movement is controlled by a solenoid valve. The push rod stroke is precisely set to the length of the standard resistance rod, and a positioning sensor is installed at the end of the push rod to ensure that the standard resistance rod accurately enters the measurement area. The push rod movement speed is synchronized with the intermittent movement cycle of the copper rod. When the production line stops, the push rod completes the pushing action of the standard resistance rod.

[0052] The standard resistance rod is made of high-purity manganese-copper alloy, with a resistance stability of ±0.05% / year, a nominal resistance of 10mΩ, and an accuracy of ±0.1%. The rod surface is gold-plated to reduce contact resistance; spring contacts are installed at both ends to ensure good electrical contact with the test electrode.

[0053] When in use, the production line stop signal triggers the calibration program, first disconnecting the copper rod measurement channel; the pneumatic push rod pushes the standard resistance rod into the measurement area, and triggers the contact detection sensor after it is in place; the superconducting quantum interference device and the multi-physics field sensor simultaneously collect the standard resistance rod data, and the system automatically calculates the deviation between the current measurement value and the nominal value; the gain coefficient of the superconducting quantum interference device and the zero point offset of the sensor are adjusted according to the deviation value to complete the calibration; after the calibration is completed, the push rod is retracted to restore the copper rod measurement state.

[0054] In this embodiment, by regularly using a standard resistance rod for zero-point calibration, the systematic errors of the resistance detection unit and the multi-physical field data acquisition unit can be effectively eliminated, the accuracy and reliability of the measurement can be improved, and the measurement results can more truly reflect the resistance performance and physical state of the oxygen-free copper rod; calibration is performed during the intermittent motion stage of the copper rod to avoid interruption of the production process, ensure the continuity of oxygen-free copper rod production, and improve production efficiency; regular calibration helps to promptly discover possible performance changes in the measuring unit, and make timely adjustments and maintenance, thereby enhancing the stability and reliability of the online resistance testing system and reducing product quality problems and production accidents caused by measurement errors.

[0055] In some embodiments of the present invention, the copper rod is subjected to various mechanical stresses such as stretching and bending, which affect the resistivity of the copper rod. If the mechanical stress on the copper rod cannot be accurately measured, the resistivity cannot be accurately corrected using the dynamic compensation unit, which in turn affects the accuracy of the oxygen-free copper rod resistance test results. Traditional stress measurement methods make it difficult to obtain copper rod stress data in real time and accurately on the production line. However, the fiber Bragg grating sensor group has the characteristics of high sensitivity, resistance to electromagnetic interference, and distributed measurement. Embedding it in the copper rod transmission guide wheel can capture the mechanical stress at the contact point between the copper rod and the guide wheel during transmission in real time.

[0056] Specifically, the appropriate fiber Bragg grating (FBG) sensor should be selected, with a reflection wavelength range that meets the measurement requirements and high sensitivity to detect small stress changes. The sensor group layout should be designed based on the size of the copper rod and the structure of the transmission guide wheel. Multiple fiber Bragg grating sensors are usually connected in parallel or series to improve measurement accuracy and reliability. The fiber Bragg grating sensor should be packaged using high-temperature and corrosion-resistant materials to ensure that the sensor can operate normally in harsh industrial environments.

[0057] A slot is cut at an appropriate location on the copper rod transmission guide wheel, and the fiber Bragg grating sensor group is embedded in the slot. The size and shape of the slot should be designed according to the size of the sensor to ensure that the sensor is firmly installed and does not affect the normal rotation of the guide wheel. The sensor is fixed in the slot using a special adhesive or fixing device to prevent displacement or loosening of the sensor during copper rod transmission. A protective layer is provided on the surface of the guide wheel to prevent direct contact between the copper rod and the sensor and prevent mechanical damage to the sensor.

[0058] The fiber Bragg grating sensor group is connected to the data acquisition system via optical fiber. The data acquisition system uses a high-speed, high-precision acquisition card that can collect the sensor's reflected wavelength signal in real time. The collected signal is demodulated and processed to convert the change in reflected wavelength into a stress change value. Demodulation can be performed using a wavelength demodulator or a dedicated chip based on the fiber Bragg grating demodulation principle. The demodulated stress data is transmitted to the dynamic compensation unit via wired or wireless communication to provide accurate stress data for the calculation of volume resistivity.

[0059] Through the above-mentioned settings, the mechanical stress data of the copper rod during the transmission process can be obtained in real time. The fiber Bragg grating sensor has high precision and can accurately measure the mechanical stress of the copper rod, thereby improving the measurement accuracy. Since the fiber Bragg grating sensor is resistant to electromagnetic interference, it can operate stably and reliably in the complex electromagnetic environment of oxygen-free copper rod production, ensuring the accuracy of the measurement results. Embedding the fiber Bragg grating sensor group in the guide wheel does not require the addition of additional complex devices and will not interfere with the normal transmission and production process of the copper rod. At the same time, it can also monitor the changes in the mechanical stress of the copper rod during the transmission process in real time, and promptly discover potential stress concentration problems, which helps to optimize the production process and improve product quality.

[0060] In some embodiments of the present invention, in order to achieve real-time remote monitoring and data analysis of test results, it is necessary to transmit the data to an external terminal in a timely manner. Traditional wired transmission methods have problems such as complex wiring, high cost, and susceptibility to environmental influences. Considering that wiring may be difficult at the copper rod production site and battery power supply has high maintenance costs, environmental pollution risks, and limited battery life, using the copper rod movement energy to generate electricity to provide power for the wireless transmission unit can avoid the above problems and ensure the stable operation of the wireless transmission unit.

[0061] Specifically, high-strength ceramic-based piezoelectric columns are symmetrically installed on both sides of the copper rod, with the spacing matching the copper rod diameter. The piezoelectric columns are fixed to the production line frame via elastic metal brackets, maintaining a 0.5-1mm gap with the copper rod surface. The radial vibration of the copper rod during transmission is used to generate electricity through the piezoelectric effect. Multilayer piezoelectric ceramic sheets are installed inside the piezoelectric columns to generate electricity through the piezoelectric effect. The piezoelectric columns are also covered with aluminum nitride ceramic heat sinks and equipped with an active air cooling system to ensure stable performance in an environment of 300°C.

[0062] When the copper rod is in the transmission process, radial vibration will occur, and the piezoelectric column will deform due to mechanical stress, thereby generating electrical energy; the piezoelectric column will collect and convert the generated electrical energy through the energy collection circuit to provide stable power for the wireless communication module; the wireless communication module receives the test data from the resistance detection unit and the multi-physics field data acquisition unit, converts it into a wireless signal and sends it to the external terminal; the external terminal can be a monitoring computer, server or mobile device, etc., which runs the corresponding data reception and analysis software to display and process the transmitted resistance test data in real time.

[0063] In this embodiment, the copper rod's kinetic energy is converted into electrical energy through a piezoelectric film, eliminating the need for external power supply or frequent battery replacement, reducing the system's maintenance costs and environmental impact, and improving the system's autonomy and reliability. The oxygen-free copper rod's online resistance test results can be sent to an external terminal in real time, facilitating remote monitoring and timely data analysis by operators, thereby improving the intelligence and informatization of the production process. The wireless transmission method is not restricted by wiring, making installation and adjustment more flexible and convenient, and is suitable for various complex industrial field environments.

[0064] In some embodiments of the present invention, the resistivity of oxygen-free copper rods is strongly correlated with temperature. Uneven temperature distribution of the copper rods during the production process can cause a resistivity deviation of more than ±1.5%. Traditional single-point thermocouples or low-resolution infrared thermometers cannot capture transient temperature gradients, resulting in failure of the dynamic compensation model. Therefore, it is necessary to achieve non-contact, full-surface, and high-temporal and spatial resolution real-time detection of the temperature field.

[0065] Specifically, a cooled medium-wave infrared detector with a frame rate of ≥1000Hz, a spatial resolution of 0.5mm, such as the FLIRA6751sc, and a noise equivalent temperature difference of ≤15mK is selected; a built-in dual blackbody radiation source with a temperature range of 50-500°C and an accuracy of ±0.1°C is used for real-time calibration of the thermal imager;

[0066] Three thermal imagers are arranged along the copper rod's transmission direction, covering the top surface of the copper rod at 0° and the side surface at ±45°, eliminating blind spots. The thermal imagers are installed in a water-cooled protective cover, 200 mm away from the copper rod surface, and image through a sapphire window.

[0067] The thermal imager outputs a 14-bit digital signal, and the surface temperature is inverted using Planck's radiation law. The formula is as follows:

[0068]

[0069] Among them, T surfaceis the surface temperature of the copper rod, which indicates the temperature corresponding to the thermal radiation characteristics of the measured object at a specific wavelength; λ is the wavelength of the electromagnetic wave used in the measurement; c1 and c2 are the first radiation constant and the second radiation constant, respectively, c1 = 1.191 × 10 16 W\cdotpμm4 / m2sr, c2=1.4388×10 4 μm\cdotpK,L measured is the measured radiation intensity;

[0070] A three-dimensional transient heat transfer model of the copper rod is established based on the heat conduction equation:

[0071]

[0072] Where ρ represents the density of the copper rod material; C p is the specific heat capacity at constant pressure, which represents the heat required to raise the unit mass of the copper rod by 1K under constant pressure; Indicates the rate of temperature change; represents the three-dimensional spatial differential operator, describing the spatial variation of the temperature field; k is the thermal conductivity of the copper rod; represents the temperature value of any point inside the copper rod; q gen Indicates the heat generation rate inside the copper rod, including frictional heat, plastic deformation heat, etc.; combined with the surface temperature boundary condition, the internal temperature field is inverted by the finite element method, with an iteration step of 1ms and a spatial resolution of 0.1mm;

[0073] It automatically switches to a blackbody radiation source every 10 minutes to calibrate the thermal imager response curve and eliminate ambient temperature drift. The data from the three thermal imagers are spatially aligned and weighted averaged based on the matching of copper rod edge feature points to eliminate single-view occlusion errors.

[0074] In this embodiment, the temperature field detection module utilizes a high-frame-rate infrared thermal imager, a multi-view fusion algorithm, and a transient heat transfer model to achieve non-contact, high-precision, and fully dynamic measurement of the surface and internal temperature fields of oxygen-free copper rods. Its multispectral anti-interference capabilities, online blackbody calibration, and three-dimensional temperature field inversion significantly reduce the overall error in resistivity detection.

[0075] As some embodiments of the present invention, in the actual production of oxygen-free copper rods, the resistivity of the copper rod body is not a fixed value, but will be affected by various physical factors such as temperature and strain; temperature changes will change the thermal motion state of copper atoms, thereby affecting the mobility of electrons and causing the resistivity to change; and strain will cause the internal crystal structure of the copper rod to be distorted, which will also hinder the conduction of electrons and cause a change in resistivity; if the influence of temperature and strain factors is not considered when measuring the resistivity of the copper rod body, the measurement result will not accurately reflect the true conductive performance of the copper rod, resulting in a misjudgment of the quality of the copper rod, affecting the power transmission efficiency and quality of subsequent downstream products such as wires and cables, electronic devices, etc.; therefore, it is necessary to dynamically compensate for the influence of temperature and strain; specifically, as follows:

[0076] Temperature effect: The temperature coefficient of resistivity of copper is α = 0.00393 / °C. For every 1°C increase in temperature, the resistivity increases by about 0.393%;

[0077] Strain effect: Mechanical stress causes lattice distortion, and the resistivity change is Δρ / ρ = β·σ (β = 0.0125 / GPa);

[0078] Cross-coupling: Temperature gradient induces local thermal expansion stress, and strain leads to local Joule heat accumulation. The nonlinear superposition effect of the two needs to be corrected simultaneously.

[0079] Specifically, a multi-physics coupling model is constructed based on the above-mentioned temperature effect, strain effect and cross-coupling, and the control equation is as follows:

[0080]

[0081] ρ corrected =ρ-Δρ.

[0082] Where Δρ represents the resistivity error under the multiple influences of temperature effect, strain effect and cross-coupling; ρ corrected represents the volume resistivity after compensation; ρ represents the original resistivity, which is calculated by the resistance detection unit;

[0083] α·ΔT is the temperature effect term, which corrects for resistivity deviations caused by pure temperature. α is the temperature coefficient, which represents the linear rate of change of resistivity for every 1°C increase in temperature. The resistivity increases with increasing temperature due to the increased probability of electron scattering caused by enhanced lattice vibration. For oxygen-free copper, α = 0.00393 / °C (20°C reference). ΔT is the temperature change, which is the difference between the current temperature of the copper rod and the reference temperature (usually 20°C). The surface temperature field is acquired in real time using an infrared thermal imager, and the internal temperature distribution is inverted.

[0084] β·σ is the stress effect term, which corrects the resistivity deviation caused by stress. β is the piezoresistance coefficient, which represents the rate of change of resistivity caused by unit stress. Mechanical stress causes lattice distortion, changes the electron migration path, and the resistivity increases with increasing stress. For oxygen-free copper, β = 0.0125 / GPa. σ is the mechanical stress, the tensile / compressive stress value of the copper rod, measured by the fiber Bragg grating sensor.

[0085] is the thermal-mechanical cross-coupling term, which corrects the nonlinear deviation caused by thermal-mechanical coupling; γ is the cross-coupling coefficient, which characterizes the intensity of the nonlinear effect of the combined action of temperature gradient and stress. The temperature gradient induces local thermal expansion stress, which is superimposed on the external mechanical stress and aggravates the lattice distortion. is the temperature gradient, the spatial rate of change of the temperature inside the copper rod, which is obtained by inverting the heat conduction equation.

[0086] In this embodiment, by clarifying parameters such as the temperature coefficient and the piezoresistive coefficient, the effects of temperature, strain, and their cross-coupling on resistivity are converted into a calculable mathematical model, ensuring that there is an accurate basis for the analysis of resistivity changes, avoiding subjective judgment, and improving measurement accuracy; based on the real-time collected temperature and stress data, the resistivity error is instantly calculated and corrected using the control equation, which can quickly respond to changes in physical conditions during the production process and ensure that the measurement results always fit the actual conductive properties of the copper rod; by comprehensively covering the temperature effect, strain effect, and the cross-coupling between the two, the limitations of single-factor correction are broken through, the resistivity characteristics of the copper rod under complex working conditions are truly restored, quality misjudgments are reduced, and the production process is optimized to ensure the power transmission efficiency and quality of downstream products, effectively reducing production costs and resource waste.

[0087] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. An oxygen-free copper rod online resistance testing system, characterized in that: include: The resistance detection unit is used to sense the magnetic field strength data generated by the current inside the copper rod and calculate the resistivity of the copper rod based on this data; A multi-physics field data acquisition unit, including a temperature field detection module and a stress field detection module, is used to detect the temperature distribution data and mechanical stress data of the copper rod respectively; A dynamic compensation unit is used to receive the temperature distribution data and the mechanical stress data, dynamically compensate for the influence of temperature and strain on the resistivity of the copper rod through a preset multi-physics field coupling model, and use the compensated body resistivity as the oxygen-free copper rod online resistance test result.

2. The oxygen-free copper rod online resistance testing system according to claim 1, characterized in that: The resistance detection unit uses a plurality of superconducting magnetic sensors based on magnetic flux quantization effect arranged axially along the copper rod transmission path to sense the magnetic field intensity generated by the current inside the copper rod.

3. The oxygen-free copper rod online resistance testing system according to claim 2, characterized in that: The superconducting magnetic sensor is a superconducting quantum interference device, which includes at least one Josephson junction and a superconducting loop.

4. The oxygen-free copper rod online resistance testing system according to claim 2, characterized in that: An electromagnetic shielding cover is provided outside the superconducting magnetic sensor, and an absorbing material layer is provided on the inner wall of the electromagnetic shielding cover to reduce interference of external magnetic fields and external electromagnetic waves on the measurement of the superconducting magnetic sensor.

5. The oxygen-free copper rod online resistance testing system according to claim 3, characterized in that: A magnetic flux focuser is provided between the superconducting quantum interference device and the copper rod, so as to enhance the magnetic field capturing capability of the superconducting quantum interference device.

6. The oxygen-free copper rod online resistance testing system according to claim 5, characterized in that: The magnetic flux focuser is composed of a permalloy conical cavity, and the cone angle of the conical cavity satisfies: tanθ=μ r ·(d / L); Where θ represents the cone angle of the conical cavity; μ r is the relative magnetic permeability, d is the copper rod diameter, and L is the sensor spacing.

7. The oxygen-free copper rod online resistance testing system according to any one of claims 1 to 6, characterized in that: It also includes a calibration unit, which is used to automatically push the standard resistance rod into the measurement area during the intermittent movement stage of the copper rod, and to perform zero point calibration on the resistance detection unit and the multi-physics field data acquisition unit.

8. The oxygen-free copper rod online resistance testing system according to any one of claims 1 to 6, characterized in that: The stress field detection module adopts a fiber optic Bragg grating sensor group, which is embedded in the copper rod transmission guide wheel and is used to measure the mechanical stress data of the copper rod in real time.

9. The oxygen-free copper rod online resistance testing system according to any one of claims 1 to 6, characterized in that: It also includes a wireless transmission unit that uses the copper rod movement energy to generate electricity for data transmission and sends the oxygen-free copper rod online resistance test result to an external terminal.

10. The oxygen-free copper rod online resistance testing system according to claim 9, characterized in that: The wireless transmission unit includes a piezoelectric device and a wireless communication module. By arranging the piezoelectric device on both sides of the copper rod, radial vibration of the copper rod during transmission is used to generate electricity to power the wireless communication module.

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