Oxygen-free copper rod on-line resistance testing system

Abstract

The present application relates to copper rod production technical field, especially to a kind of oxygen-free copper rod on-line resistance test system, comprising: resistance detection unit, for inducting the magnetic field intensity data generated by copper rod internal current, and with this calculation obtains copper rod resistivity;Multi-physics field data acquisition unit, including temperature field detection module and stress field detection module for detecting copper rod temperature distribution data and copper rod mechanical stress data respectively;Dynamic compensation unit, for receiving temperature distribution data and mechanical stress data, through the influence of preset multi-physics field coupling model dynamic compensation temperature and strain on copper rod resistivity, and after compensation bulk resistivity is used as oxygen-free copper rod on-line resistance test result;It can more accurately measure the real resistance performance of oxygen-free copper rod under actual production conditions, improve the accuracy of measurement result.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of copper rod production, and in particular to an oxygen-free copper rod online resistance testing system. BACKGROUND

[0002] As a high-purity conductive material (copper content ≥ 99.99%), the DC resistance performance of oxygen-free copper rod is a core indicator for measuring the conductivity, which directly affects the power transmission efficiency of downstream products such as wire and cable, electronic devices, etc. The traditional resistance testing methods mainly include laboratory four-probe method, eddy current detection method, etc.

[0003] Among them, the four-probe method needs to physically contact the surface of the copper rod, which causes the measurement to have to slow down or stop, seriously restricting the production efficiency, and uneven contact pressure also causes surface scratches, affecting the quality of finished products; while the eddy current detection method is limited by the skin effect, and can only reflect the resistance characteristics of the surface layer of the copper rod. When there are internal grain boundary oxidation and micropore defects in the copper rod, the surface measurement value cannot represent the true bulk resistivity of the material, resulting in quality misjudgment. SUMMARY

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

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

[0006] A resistance detection unit for sensing the magnetic field strength data generated by the internal current of the copper rod and calculating the bulk resistivity of the copper rod therefrom;

[0007] A multi-physical field data acquisition unit including a temperature field detection module and a stress field detection module for detecting copper rod temperature distribution data and copper rod mechanical stress data, respectively;

[0008] A dynamic compensation unit for receiving the temperature distribution data and the mechanical stress data, dynamically compensating the influence of temperature and strain on the bulk resistivity of the copper rod through a pre-set multi-physical field coupling model, and taking the compensated bulk resistivity as the oxygen-free copper rod online resistance testing result.

[0009] In combination with the first aspect, in a possible design, the resistance detection unit adopts a plurality of superconducting magnetic sensors based on the magnetic flux quantization effect arranged axially along the transmission path of the copper rod for sensing the magnetic field strength generated by the internal current of the copper rod.

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

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

[0012] With reference to the first aspect, in a possible design, a magnetic flux concentrator is arranged 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.

[0013] With reference to the first aspect, in a possible design, the magnetic flux concentrator is composed of a permalloy conical cavity, and the conical angle of the conical cavity satisfies:

[0014] tan theta = mu r · (d / L) ;

[0015] Wherein, theta represents the conical angle of the conical cavity, mu r is the relative magnetic permeability, d is the diameter of the copper rod, and L is the sensor spacing.

[0016] With reference to the first aspect, in a possible design, further comprising a calibration unit, configured to automatically push a standard resistance rod into a measurement area during the intermittent motion stage of the copper rod, and perform zero-point calibration on the resistance detection unit and the multi-physical field data acquisition unit.

[0017] With reference to the first aspect, in a possible design, the stress field detection module adopts a fiber grating sensor group, and the fiber grating sensor group is embedded in a copper rod transmission guide wheel, so as to measure the mechanical stress data of the copper rod in real time.

[0018] With reference to the first aspect, in a possible design, further comprising a wireless transmission unit, which utilizes the energy generated by the motion of the copper rod to supply power for data transmission, and sends the online resistance test result of the oxygen-free copper rod to an external terminal.

[0019] With reference to the first aspect, in a possible design, the wireless transmission unit comprises a piezoelectric device and a wireless communication module, and the piezoelectric device is arranged on both sides of the copper rod, so as to generate electricity by using the radial vibration during the transmission of the copper rod, and supply power for the wireless communication module.

[0020] The technical scheme of the present application can achieve the following technical effects:

[0021] This system uses a non-contact resistance detection unit to sense the internal current and magnetic field of the copper rod, directly obtaining the volume 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 corrects for the interference of temperature / strain on resistivity through a multi-physics coupling model. The combination of these three components enables continuous testing during copper rod production without stopping or slowing down, while also penetrating the surface and eliminating environmental variables. This allows for more accurate measurement of the true resistivity performance of oxygen-free copper rods under actual production conditions, improving the accuracy of the measurement results. Attached Figure Description

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

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0024] This application will now be described with reference to 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 to calculate the resistivity of the copper rod body based on this data.

[0027] The multi-physics data acquisition unit includes a temperature field detection module and a stress field detection module, which are 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, and dynamically compensate for the influence of temperature and strain on the resistivity of the copper rod through a preset multi-physics coupling model, and uses the compensated volume 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 / stopping during testing, 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. This system uses a resistance detection unit to sense the internal current magnetic field of the copper rod in a non-contact manner, directly obtaining the volume resistivity, avoiding contact damage and surface detection blind spots; at the same time, the multi-physics 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 resistivity through a multi-physics coupling model; the combination of these three features enables the system to continuously test without stopping or slowing down during the copper rod production process, and can penetrate the surface and eliminate environmental variables, so as to more accurately measure the true resistance performance of oxygen-free copper rods under actual production conditions and improve 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, temperature gradients and tensile stress during the wire drawing and cooling processes in the production process can lead to measurement deviations if traditional methods do not compensate for these variables. The system captures the state parameters of the copper rod in real time through temperature field detection and stress field detection modules. Combined with the multi-physics coupling model of the dynamic compensation unit, the nonlinear relationship between temperature and resistivity and strain and resistivity is embedded in the algorithm. For example, when it is detected that the temperature of a section of the copper rod has increased due to uneven cooling, the model automatically reduces the positive influence weight of temperature on resistivity. When the stress field detection module detects abnormal tensile stress, it corrects the interference of lattice distortion on the mobility of conductive electrons. This allows the system to output stable and reliable volume resistivity data even in complex production environments (such as temperature fluctuations and mechanical vibrations), solving the problem of multi-variable interference that a single detection unit cannot handle.

[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 internal current of the copper rod. The superconducting magnetic sensor based on the flux quantization effect has ultra-high sensitivity and can sense the magnetic field generated by the internal current of the copper rod in a non-contact manner. Combined with the axial arrangement design, it can cover the detection of the magnetic field distribution along the entire length of the copper rod, solving the problems of contact damage and surface limitations of traditional methods.

[0032] Specifically, conductive clamps are installed at the input and output ends of the copper rod transmission path. The clamps 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 avoid pressure contact to prevent surface damage. The conductive clamps are connected to a high-precision constant current source via wires. The constant current source provides 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. The current flowing inside the copper rod will generate a ring magnetic field.

[0033] Two to four sets of superconducting magnetic sensors are symmetrically arranged axially at intervals of 50-100cm directly above and below the copper rod transmission path. Each set of sensors includes one magnetic field induction probe, with the probe axis perpendicular to the copper rod axis to ensure magnetic field distribution covering the entire cross-section of the copper rod. The superconducting magnetic sensors are fixed to the production line frame by an insulating bracket. The bracket height is adjustable to accommodate copper rods of different diameters and maintains a distance of 5-10cm from the surface of the copper rod to avoid mechanical interference while meeting the magnetic field penetration requirements.

[0034] According to Ampere's circuital law, the magnetic field strength 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 current across the cross section is calculated by integration as: I = 2πrH φ , where r is the radius of the copper rod;

[0035] Combining the length L and cross-sectional area S of the copper rod, and using the resistance formulas R = ρL / S and R = U / I, where U is the voltage across the copper rod, which can be obtained through a high-precision constant current source connected to a conductive clamp, the volume resistivity calculation formula is derived as: ρ = RS / L = (US) / (2πrH) φ L).

[0036] In this embodiment, no physical contact with the copper rod surface is required, avoiding the contact pressure damage and downtime issues associated with the four-probe method. Real-time online detection can be achieved even when the copper rod is moving at high speed, completely eliminating the risk of surface scratches and 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 more accurately reflects the overall conductivity of the copper rod. Even if there are defects such as grain boundary oxidation or micropores inside the copper rod, they can be accurately detected, avoiding misjudgments. Multiple sensors are arranged along the axial direction to acquire magnetic field data for different sections of the copper rod. Spatial filtering algorithms (such as moving average and Kalman filtering) are used to filter out accidental noise (such as brief mechanical vibrations and local electromagnetic interference), making the measurement results more stable. Furthermore, by comparing the detection data of different sensors, the specific location of resistivity anomalies can be located, such as local stress concentration areas caused by wire 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 sandwiching an extremely thin insulating layer. 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 when an external magnetic field is applied. This property of the Josephson junction allows it to respond to weak changes in magnetic field.

[0039] A superconducting loop is a closed loop made of superconducting material; when magnetic flux passes through this loop, according to the magnetic flux quantization effect, the magnetic flux can only take the value Φ0 = 2.068 × 10⁻⁶. -15 Integer multiples of Wb; the superconducting loop in the superconducting quantum interference device works in conjunction with the Josephson junction. When the external magnetic field changes and causes a change in the magnetic flux through the loop, the superconducting current in the loop will change accordingly, thus affecting the output of the Josephson junction.

[0040] In this practical application, the superconducting quantum interference device (SQU) is placed close to the 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 toroidal magnetic field is generated, which acts on the superconducting loop of the SQU. The magnetic flux in the superconducting loop changes, which in turn causes a change in the output current of the Josephson junction. By detecting the change in the output current of the Josephson junction, 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 utilizes the flux quantization effect and the Josephson effect to detect extremely weak magnetic field changes, achieving a magnetic field resolution of 10⁻¹. 5 On the order of terabytes (T), the superconducting quantum interference device (SQFID) can accurately sense the weak magnetic field generated by the current inside the copper rod, improving the accuracy of resistance detection. It can operate over a wide frequency range, adapting to changes in the magnetic field generated by the current inside the copper rod under different operating conditions. Whether it's a low-frequency steady-state current magnetic field or a high-frequency dynamic current magnetic field, the SQFID can accurately detect both, ensuring the comprehensiveness and accuracy of resistance detection. Furthermore, due to the special structure and working principle of the Josephson junction and superconducting loop, the SQFID exhibits extremely low noise levels. This effectively suppresses external noise interference when detecting weak magnetic fields, improving the signal-to-noise ratio and further ensuring the reliability of the measurement results.

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

[0043] Specifically, an electromagnetic shielding cover with a thickness of 1 mm is made of a high-permeability μ metal (such as permalloy). The μ metal has unique magnetic properties; in a low-frequency magnetic field environment, its permeability is very high, which can effectively guide and absorb external magnetic fields and prevent 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 to ensure that there are no gaps between the shielding cover and the sensor, preventing external magnetic fields from entering through gaps. The shape of the shielding cover is designed to fit the shape of the sensor to cover the sensor to the maximum extent 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 wide-band absorption characteristics of graphene can effectively absorb high-frequency electromagnetic waves in the range of 100 MHz to 10 GHz, avoiding reflection of these waves within the shielding cover and the formation of standing wave interference. The bonding process uses high-temperature resistant adhesive to evenly bond the absorbing material to the inner wall of the shielding cover, ensuring no air bubbles or gaps, and forming a continuous electromagnetic wave absorption interface.

[0045] In this embodiment, by setting an electromagnetic shield around the superconducting magnetic sensor and adding a wave-absorbing material layer to the inner wall, the anti-interference capability of the superconducting magnetic sensor measurement can be significantly improved. On the one hand, it effectively shields the external magnetic field, ensuring that the magnetic field signal sensed by the superconducting magnetic sensor mainly comes from the internal current of the oxygen-free copper rod, thus improving the purity of the magnetic field strength data. On the other hand, the absorption of electromagnetic waves by the wave-absorbing material reduces electromagnetic signal interference, making the measurement data more stable and reliable, which helps to accurately calculate the resistivity of the copper rod and ensure the measurement accuracy of the oxygen-free copper rod online resistance testing system.

[0046] In some embodiments of the present invention, although the superconducting quantum interference device (SQU) possesses extremely high magnetic field sensitivity, its effective trapping area is limited. In actual detection, the annular magnetic field generated by the current inside the copper rod decays rapidly with increasing distance, resulting in weak magnetic field signals received by the SQU away from the copper rod. In particular, when the sensor spacing L is large, the attenuation of the magnetic field strength causes the measurement error to exceed ±1%. Furthermore, as a cylindrical conductor, the copper rod generates a magnetic field with a annular distribution and 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 the dispersed magnetic flux lines to the sensitive area of ​​the SQU, thereby improving the magnetic field trapping efficiency.

[0047] Specifically, the flux focuser is made of high-purity permalloy and formed into a conical cavity. The relative permeability μ of the permalloy... r =1000-10000, the formula for calculating the cone angle θ of the conical cavity is: tanθ=μ r ·(d / L); where θ represents the cone angle of the conical cavity; μ rThe relative permeability is given by d, the diameter of the copper rod is given by L, and the sensor spacing is given by L. For example, when the diameter of the copper rod is d = 8 mm and the sensor spacing is L = 50 cm, θ ≈ 4.57°. The diameter of the large end opening of the conical cavity is 2-3 times the diameter of the copper rod, and the small end is in close contact with the plane of the superconducting quantum interference device induction coil to ensure a leak-free transition of the magnetic flux lines.

[0048] The permalloy of the flux focuser undergoes vacuum heat treatment to eliminate internal stress, and a nickel plating layer is applied to the surface 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 adopted, and laser positioning ensures that the overlap between the axis of the conical cavity and the central axis of the copper rod 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 focusing effect of the flux focusing device 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. This effectively avoids measurement errors caused by weak magnetic field signals and improves the measurement accuracy of the resistance testing system. By focusing the target magnetic field, the influence of external interference magnetic fields on the measurement is reduced, and measurement fluctuations caused by environmental factors are decreased, allowing the entire resistance testing system to maintain stable operation under different working conditions, thus improving the system's reliability and stability. Based on the cone angle determined by the formula calculation, the flux focusing device can be customized according to oxygen-free copper rods of different diameters and sensor spacing, flexibly adapting to copper rod specifications in various production scenarios, enhancing the versatility and applicability of the resistance testing system.

[0050] Furthermore, during the online resistance testing of oxygen-free copper rods, the resistance detection unit and the multiphysics data acquisition unit are subject to drift due to various factors. For example, the superconducting loop of the superconducting quantum interference device is susceptible to interference from environmental magnetic field fluctuations, 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. These drifts can cause changes in the measurement reference, resulting in systematic errors in the resistivity calculation results. Traditional offline calibration methods require downtime, which severely impacts production efficiency. Therefore, it is necessary to design an online calibration mechanism that can be automatically executed during the intermittent movement phase 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 the action 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, and 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 surface of the rod is gold-plated to reduce contact resistance. Spring contacts are installed at both ends to ensure good electrical contact with the test electrodes.

[0053] During use, the production line stop signal triggers the calibration program, first disconnecting the copper rod measurement channel; the pneumatic pusher pushes the standard resistance rod into the measurement area, triggering the contact detection sensor upon reaching its position; the superconducting quantum interference device and the multiphysics sensor simultaneously acquire data from the standard resistance rod, and the system automatically calculates the deviation between the current measured value and the nominal value; based on the deviation value, the gain coefficient of the superconducting quantum interference device and the zero-point offset of the sensor are adjusted to complete the calibration; after calibration, the pusher is retracted, restoring the copper rod measurement state.

[0054] In this embodiment, by periodically performing zero-point calibration using a standard resistance bar, systematic errors in the resistance detection unit and the multi-physics data acquisition unit can be effectively eliminated, improving the accuracy and reliability of the measurement. This allows the measurement results to more accurately reflect the resistance performance and physical state of the oxygen-free copper rod. Calibration is performed during the intermittent movement phase of the copper rod to avoid interrupting the production process, ensuring the continuity of oxygen-free copper rod production and improving production efficiency. Regular calibration helps to promptly detect potential performance changes in the measurement unit, allowing for 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 tension 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 by the dynamic compensation unit, thus affecting the accuracy of the resistance test results of the oxygen-free copper rod. Traditional stress measurement methods are difficult to obtain copper rod stress data in real time and accurately on the production line. However, fiber optic grating sensor groups have the characteristics of high sensitivity, anti-electromagnetic interference, and distributed measurement. Embedding them in the copper rod transmission guide wheel can capture the mechanical stress of the copper rod in contact with the guide wheel in real time during transmission.

[0056] Specifically, select a suitable fiber Bragg grating sensor whose reflection wavelength range meets the measurement requirements and has high sensitivity to detect minute stress changes; design the sensor group layout based on the size of the copper rod and the structure of the transmission guide wheel; typically, multiple fiber Bragg grating sensors are connected in parallel or in series to improve measurement accuracy and reliability; encapsulate the fiber Bragg grating sensor using high-temperature and corrosion-resistant materials to ensure normal operation in harsh industrial environments;

[0057] A slot is cut at an appropriate position on the copper rod transmission guide wheel, and the fiber optic grating sensor assembly 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 installed firmly and does not affect the normal rotation of the guide wheel. Special adhesives or fixing devices are used to fix the sensor in the slot to prevent the sensor from shifting or loosening during the copper rod transmission process. A protective layer is set on the surface of the guide wheel to avoid direct contact between the copper rod and the sensor and to prevent the sensor from being mechanically damaged.

[0058] The fiber Bragg grating sensor array is connected to the data acquisition system via optical fiber. The data acquisition system uses a high-speed, high-precision acquisition card to acquire the reflected wavelength signal of the sensor in real time. The acquired signal is demodulated 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 setup, the mechanical stress data of the copper rod during transmission can be acquired in real time. The fiber optic grating sensor has high precision and can accurately measure the mechanical stress on the copper rod, improving measurement accuracy. Because the fiber optic grating sensor is resistant to electromagnetic interference, it can work stably and reliably in the complex electromagnetic environment of oxygen-free copper rod production, ensuring the accuracy of measurement results. Embedding the fiber optic grating sensor group in the guide wheel eliminates the need for 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 mechanical stress of the copper rod during transmission in real time, promptly detect potential stress concentration problems, and help 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 suffer from 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 that battery power supply has problems such as high maintenance costs, environmental pollution risks, and limited battery life, using the kinetic energy of the copper rod to generate electricity to power 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 diameter of the copper rod. The piezoelectric columns are fixed to the production line frame by elastic metal brackets, maintaining a gap of 0.5-1mm with the surface of the copper rod. Electrical energy is generated through the piezoelectric effect by utilizing the radial vibration of the copper rod during transmission. Multiple layers of piezoelectric ceramic sheets are set inside the piezoelectric columns to generate electrical energy through the piezoelectric effect. The piezoelectric columns are wrapped with aluminum nitride ceramic heat sinks on the outside, and with the active air cooling system, the performance is stable at 300℃.

[0062] During transmission, the copper rod undergoes radial vibration, causing the piezoelectric column to deform under mechanical stress and generate electrical energy. The generated electrical energy is collected and converted by the energy harvesting circuit to provide stable power to the wireless communication module. The wireless communication module receives test data from the resistance detection unit and the multi-physics data acquisition unit, converts it into wireless signals, and sends it to an external terminal. The external terminal can be a monitoring computer, server, or mobile device, on which corresponding data receiving and analysis software runs to display and process the transmitted resistance test data in real time.

[0063] In this embodiment, the motion energy of the copper rod is converted into electrical energy through a piezoelectric film, eliminating the need for external power supply or frequent battery replacements. This reduces system maintenance costs and environmental impact, while improving system autonomy and reliability. The system can transmit online resistance test results of the oxygen-free copper rod to an external terminal in real time, facilitating remote monitoring and timely data analysis by operators, thus enhancing the intelligence and informatization of the production process. The wireless transmission method is not limited by wiring, making installation and adjustment more flexible and convenient, and suitable for various complex industrial 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 copper rods during production can lead to resistivity deviations of more than ±1.5%. Traditional single-point thermocouples or low-resolution infrared thermometers cannot capture transient temperature gradients, causing the dynamic compensation model to fail. Therefore, it is necessary to achieve real-time detection of temperature fields with non-contact, full-surface, and high spatiotemporal resolution.

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

[0066] Three thermal imagers are arranged along the transmission direction of the copper rod, covering the upper surface of the copper rod at 0° and the side surface at ±45° respectively, to eliminate blind spots in the field of view; the thermal imagers are installed inside a water-cooled protective cover, 200mm away from the surface of the copper rod, 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 law of radiation, as shown in the following formula:

[0068]

[0069] Among them, T surfaceλ represents the surface temperature of the copper rod, indicating the temperature corresponding to the thermal radiation characteristics of the measured object at a specific wavelength; λ represents the wavelength of the electromagnetic wave used in the measurement; c1 and c2 are the first and second radiation constants, respectively, with c1 = 1.191 × 10⁻⁶. 16 W\cdotpμm4 / m2sr, c2=1.4388×10 4 μm\cdotpK, L measured This refers to the measured radiation intensity.

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

[0071]

[0072] Where ρ represents the density of the copper rod material; C p Specific heat capacity at constant pressure represents the amount of heat required to raise the temperature of a unit mass of copper rod by 1 K under constant pressure; Indicates the rate of temperature change; Represents a 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 at any point inside the copper rod; q gen The internal heat generation rate of the copper rod is represented, including frictional heat generation and plastic deformation heat. Combined with the surface temperature boundary conditions, 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] The system automatically switches to a blackbody radiation source every 10 minutes to correct the thermal imager response curve and eliminate ambient temperature drift. It also performs spatial registration and weighted averaging of data from three thermal imagers based on copper rod edge feature point matching 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 field of an oxygen-free copper rod. Its multispectral anti-interference capabilities, online blackbody calibration, and three-dimensional temperature field inversion capabilities 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 is affected by various physical factors such as temperature and strain. Temperature changes alter the thermal motion state of copper atoms, thereby affecting electron mobility and causing a change in resistivity. Strain causes distortion of the internal crystal structure of the copper rod, which also hinders electron conduction and causes a change in resistivity. If the influence of temperature and strain is not considered when measuring the resistivity of the copper rod body, the measurement results will not accurately reflect the true conductivity of the copper rod, leading to misjudgment of the quality of the copper rod and affecting the power transmission efficiency and quality of downstream products such as wires, cables, and electronic devices. Therefore, dynamic compensation for the influence of temperature and strain is required; specifically, it is manifested as follows:

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

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

[0078] Cross-coupling: Temperature gradients induce 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, based on the aforementioned temperature effect, strain effect, and cross-coupling, a multiphysics coupling model is constructed, with the following governing equations:

[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 ρ represents the compensated volume resistivity; 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 deviation caused by pure temperature; α is the temperature coefficient, which characterizes the linear rate of change of resistivity for every 1℃ increase in temperature. Due to the increased probability of electron scattering caused by enhanced lattice vibration, the resistivity increases with increasing temperature. For oxygen-free copper, α = 0.00393 / ℃ (20℃ reference); ΔT is the temperature change, which is the difference between the current temperature of the copper rod and the reference temperature (usually taken as 20℃). The surface temperature field is acquired in real time by an infrared thermal imager to invert the internal temperature distribution.

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

[0085] γ is the thermo-mechanical cross-coupling term, which corrects the nonlinear deviation caused by thermo-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 with external mechanical stress, exacerbating lattice distortion. The temperature gradient represents the spatial rate of temperature change inside the copper rod, which is obtained by inversion from the heat conduction equation.

[0086] In this embodiment, by clearly defining parameters such as temperature coefficient and piezoresistive coefficient, the influence of temperature, strain, and their cross-coupling on resistivity is transformed into a calculable mathematical model, ensuring that the analysis of resistivity changes has a precise basis, avoiding subjective judgment, and improving measurement accuracy. Based on real-time acquired temperature and stress data, resistivity errors are calculated and corrected in real time using control equations, enabling rapid response to changes in physical conditions during production and ensuring that measurement results always closely match the true conductivity of the copper rod. By comprehensively covering temperature effects, strain effects, and their cross-coupling, the limitations of single-factor correction are overcome, accurately restoring the resistivity characteristics of the copper rod under complex working conditions, reducing quality misjudgments, helping to optimize production processes, ensuring the efficiency and quality of power transmission in downstream products, and effectively reducing production costs and resource waste.

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

Claims

1. An online resistance testing system for oxygen-free copper rods, 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 to calculate the resistivity of the copper rod body based on this data. The multi-physics data acquisition unit includes a temperature field detection module and a stress field detection module, which are used to detect the temperature distribution data and mechanical stress data of the copper rod, respectively. The dynamic compensation unit is used to receive the temperature distribution data and the mechanical stress data, dynamically compensate the influence of temperature and strain on the resistivity of the copper rod through a preset multi-physics coupling model, and use the compensated resistivity as the online resistance test result of the oxygen-free copper rod. The resistance detection unit employs several superconducting magnetic sensors based on the flux quantization effect, arranged axially along the transmission path of the copper rod, to sense the magnetic field strength generated by the current inside the copper rod; the superconducting magnetic sensor is a superconducting quantum interference device, containing at least one Josephson junction and a superconducting loop.

2. The oxygen-free copper rod online resistance testing system according to claim 1, characterized in that, The superconducting magnetic sensor is equipped with an electromagnetic shield, and the inner wall of the electromagnetic shield is provided with a wave-absorbing material layer to reduce the interference of external magnetic fields and external electromagnetic waves on the measurement of the superconducting magnetic sensor.

3. The oxygen-free copper rod online resistance testing system according to claim 1, characterized in that, A flux focuser is placed between the superconducting quantum interference device and the copper rod to enhance the magnetic field trapping capability of the superconducting quantum interference device.

4. The oxygen-free copper rod online resistance testing system according to claim 3, characterized in that, The flux focuser is composed of a permalloy conical cavity, and the cone angle of the conical cavity satisfies the following: tanθ=μ r ·(d / L); Where θ represents the cone angle of the conical cavity; μ r d is the relative permeability, d is the diameter of the copper rod, and L is the sensor spacing.

5. The online resistance testing system for oxygen-free copper rods according to any one of claims 1-4, characterized in that, It also includes a calibration unit, which automatically pushes the standard resistance rod into the measurement area during the intermittent movement of the copper rod, and performs zero-point calibration on the resistance detection unit and the multi-physics data acquisition unit.

6. The online resistance testing system for oxygen-free copper rods according to any one of claims 1-4, characterized in that, The stress field detection module uses a fiber optic grating sensor group, which is embedded in the copper rod transmission guide wheel to measure the mechanical stress data of the copper rod in real time.

7. The online resistance testing system for oxygen-free copper rods according to any one of claims 1-4, characterized in that, It also includes a wireless transmission unit that uses the energy from the movement of the copper rod to generate electricity for data transmission, and sends the online resistance test results of the oxygen-free copper rod to an external terminal.

8. The online resistance testing system for oxygen-free copper rods according to claim 7, characterized in that, The wireless transmission unit includes a piezoelectric device and a wireless communication module. By placing the piezoelectric device on both sides of the copper rod, the radial vibration of the copper rod during transmission generates electricity to power the wireless communication module.

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