Segmented baking temperature control method and apparatus for copper-clad aluminum wire

Abstract

The application is suitable for the technical field of enameled wire production and manufacturing, and particularly relates to a sectional baking temperature control method and device for copper-coated aluminum enameled wire, which comprises the following steps: dividing a baking furnace into M temperature control units along the direction of wire movement, setting a first sensor for measuring the temperature of furnace gas and a second sensor for measuring the surface temperature of the wire in a non-contact manner in each unit, and prestoring the target surface temperature of each unit; in each control cycle, calculating the bimetallic thermal misalignment index of each unit according to the furnace gas temperature, the surface temperature of the wire and the target surface temperature of each unit; comparing the maximum value of the index with a first threshold value and a second threshold value, selecting a temperature control strategy from a multi-level strategy pool according to a hysteresis switching rule and generating a heater control signal, and the control signal is smoothly transitioned when the strategy is switched. The application solves the problem of uneven curing of the whole wire coating caused by the dynamic degradation of the thermal conduction of the bimetallic interface of the copper-coated aluminum wire.

Description

Technical Field

[0001] This application belongs to the field of enameled wire manufacturing technology, and particularly relates to a method and apparatus for segmented baking temperature control of copper-clad aluminum enameled wire. Background Technology

[0002] Copper-clad aluminum enameled wire is a bimetallic composite conductor with an aluminum core and a copper cladding layer. It is manufactured by coating the surface with insulating varnish and then baking and curing it in a segmented baking oven. The segmented baking oven is divided into multiple independent temperature-controlled zones along the direction of the conductor's travel, each zone having a different target process temperature: the heating zone has a lower target temperature to ensure smooth solvent vaporization, while the curing zone has a higher target temperature to ensure sufficient resin cross-linking. This coating-baking cycle typically needs to be repeated multiple times to gradually accumulate the insulation layer thickness.

[0003] The current industry standard is to set fixed temperature values ​​for each temperature control zone, with each zone using an independent PID controller to maintain stable furnace gas temperature. However, the thermal expansion coefficient of the aluminum core in copper-clad aluminum conductors is approximately 1.36 times that of the copper cladding. During heating, the aluminum core expands significantly faster than the copper cladding, generating radial tensile stress at the aluminum-copper interface and forming a micron-level transient gap. This gap is equivalent to introducing additional thermal resistance at the copper-aluminum interface, hindering heat conduction from the copper cladding to the aluminum core. This results in a significant lag in the aluminum core temperature response compared to the surface, a phenomenon known as "bimetallic interface thermal conduction dynamic degradation." This degradation effect, coupled with the inherent non-uniformity of furnace temperature, causes inconsistent deviations between the actual conductor surface temperature and the target process temperature in each temperature control zone. Existing fixed-temperature PID control methods cannot detect or respond to these dynamic changes in internal heat conduction, ultimately leading to uneven curing of the coating throughout the conductor, and a significant decrease in insulation reliability and mechanical flexibility. Summary of the Invention

[0004] This application provides a segmented baking temperature control method and apparatus for copper-clad aluminum enameled wire, which can solve the problem that the prior art cannot detect and deal with the "dynamic degradation of thermal conduction at the bimetallic interface" effect, resulting in uneven curing of the enamel film throughout the wire, and a significant decrease in insulation reliability and mechanical flexibility.

[0005] In a first aspect, embodiments of this application provide a segmented baking temperature control method for copper-clad aluminum enameled wire, wherein the segmented baking furnace is divided into M spatially discrete temperature control units along the travel direction of the copper-clad aluminum wire, where M is greater than or equal to 3. Each temperature control unit is respectively equipped with a first temperature sensor and a second temperature sensor. The first temperature sensor is used to measure the furnace gas temperature within the temperature control unit, and the second temperature sensor is used to measure the surface temperature of the copper-clad aluminum wire at the outlet side of the temperature control unit in a non-contact manner. The method includes: Pre-store the target surface temperature of each temperature control unit; Within each control cycle, based on the furnace gas temperature, the surface temperature of the copper-clad aluminum conductor, and their respective target surface temperatures of each temperature control unit, the bimetallic thermal runaway index of each temperature control unit in the current control cycle is calculated; wherein, the bimetallic thermal runaway index is used to reflect the degree to which the surface temperature of the copper-clad aluminum conductor in each temperature control unit deviates from its respective target surface temperature, as well as the comprehensive thermal response nonuniformity of the degree of dynamic degradation of thermal conduction at the copper-aluminum bimetallic interface. The maximum value of the bimetallic thermal runaway scheduling index of each temperature control unit is compared with a preset first threshold and a second threshold. Based on the comparison result, a temperature control strategy for the current control cycle is selected from a multi-level temperature control strategy pool containing at least three different temperature control strategies according to a preset hysteresis switching rule. Wherein, the first threshold is less than the second threshold, and each temperature control strategy generates a control signal for the heating element configured in the temperature control unit through at least one feedback controller. Based on the selected temperature control strategy, heater control signals are generated for each temperature control unit to adjust the output power of the heating element in each temperature control unit; wherein, when the temperature control strategy is switched, the heater control signal smoothly transitions from the control signal value corresponding to the strategy before the switch to the control signal value corresponding to the strategy after the switch at a preset gradual rate.

[0006] The technical solutions described in this application embodiment have at least the following technical effects: In the segmented baking temperature control method for copper-clad aluminum enameled wire provided in this application, firstly, the target surface temperature of each temperature control unit is pre-stored. This step involves pre-storing the target surface temperature of each unit within each temperature control unit. Secondly, within each control cycle, based on the furnace gas temperature, the surface temperature of the copper-clad aluminum wire, and their respective target surface temperatures of each temperature control unit, the bimetallic thermal runaway index of each temperature control unit in the current control cycle is calculated. The bimetallic thermal runaway index obtained in this step reflects the degree to which the surface temperature of the copper-clad aluminum wire deviates from its respective target surface temperature within each temperature control unit, as well as the comprehensive thermal response nonuniformity of the degree of dynamic degradation of thermal conduction at the copper-aluminum bimetallic interface. It can quantitatively characterize the degree of thermal response nonuniformity of the copper-clad aluminum wire bimetallic structure under the current operating conditions. Furthermore, because this index uses the target surface temperature of each unit as the normalization benchmark rather than the overall line temperature uniformity benchmark, the inherent process temperature difference between different temperature control units will not be misjudged as abnormal. Then, the maximum value of the bimetallic thermal runaway scheduling index of each temperature control unit is compared with the preset first threshold and second threshold. According to the comparison result, the temperature control strategy for the current control cycle is selected from a multi-level temperature control strategy pool containing at least three different temperature control strategies according to the preset hysteresis switching rule. In this step, the corresponding temperature control response level is automatically matched according to the level of the thermal runaway scheduling index: when the index is low, global unified PID control is executed; when only some units have slight deviations, local compensation is superimposed; when there are serious deviations across the entire line, independent PID of each unit is activated and a coating feedforward compensation is introduced. The hysteresis switching rule sets a hysteresis width at the strategy switching boundary, so that small fluctuations of the maximum value around the threshold will not cause frequent strategy switching, effectively avoiding oscillation of the control system. Finally, based on the selected temperature control strategy, heater control signals are generated for each temperature control unit to adjust the output power of the heating elements within each temperature control unit. In this step, the heater control signals are generated according to the selected strategy, and when the temperature control strategy switches, the heater control signals achieve a smooth transition with a preset gradual change rate. This avoids the drastic disturbances in the furnace gas temperature within each temperature control unit caused by the step-like abrupt change in the control signal during strategy switching in traditional control methods, ensuring the continuous stability of the baking process during switching. In this method, a complete closed loop of dual temperature sensing, quantization, hierarchical strategy, and hysteresis-based smooth output is used. During most of the steady-state time, only a low-computational-overhead strategy needs to be run, while the response level is automatically upgraded under abnormal conditions. This approach balances control accuracy, response speed, and system stability, effectively solving the technical problem of uneven coating curing caused by the dynamic degradation of thermal conduction at the bimetallic interface during the segmented baking process of copper-clad aluminum enameled wire.

[0007] Secondly, embodiments of this application provide a programmable logic controller for segmented baking temperature of copper-clad aluminum enameled wire. The controller is applied to a segmented baking oven, and the segmented baking oven is divided into M spatially discrete temperature control units along the direction of travel of the copper-clad aluminum wire, where M is greater than or equal to 3. Each temperature control unit is equipped with a first temperature sensor and a second temperature sensor. The first temperature sensor is used to measure the furnace gas temperature within its respective temperature control unit, and the second temperature sensor is used to measure the surface temperature of the copper-clad aluminum wire at the outlet side of its respective temperature control unit in a non-contact manner. The controller includes: The pre-storage unit is used to pre-store the target surface temperature of each temperature control unit. The thermal runaway scheduling calculation unit is used to calculate the bimetallic thermal runaway scheduling index of each temperature control unit in each control cycle, based on the furnace gas temperature, the surface temperature of the copper-clad aluminum conductor, and their respective target surface temperatures. The bimetallic thermal runaway scheduling index is used to reflect the degree to which the surface temperature of the copper-clad aluminum conductor in each temperature control unit deviates from its respective target surface temperature, as well as the comprehensive thermal response nonuniformity of the degree of dynamic degradation of thermal conduction at the copper-aluminum bimetallic interface. The temperature control strategy selection unit is used to compare the maximum value of the bimetallic thermal runaway scheduling index of each temperature control unit with a preset first threshold and a second threshold. According to the comparison result, it selects the temperature control strategy to execute the current control cycle from a multi-level temperature control strategy pool containing at least three different temperature control strategies according to a preset hysteresis switching rule. The first threshold is less than the second threshold, and each temperature control strategy generates a control signal for the heating element configured by the temperature control unit through at least one feedback controller. The temperature control unit is used to generate heater control signals for each temperature control unit according to the selected temperature control strategy, so as to adjust the output power of the heating element in each temperature control unit; wherein, when the temperature control strategy is switched, the heater control signal smoothly transitions from the control signal value corresponding to the strategy before the switch to the control signal value corresponding to the strategy after the switch at a preset gradual rate.

[0008] Thirdly, embodiments of this application provide a segmented baking temperature control device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that the processor executes the computer program to implement the method described in any of the first aspects above.

[0009] Fourthly, embodiments of this application provide a computer-readable storage medium storing a computer program that, when executed by a processor, implements the method described in any of the first aspects above.

[0010] Fifthly, embodiments of this application provide a computer program product that, when running on a segmented baking temperature control device, causes the segmented baking temperature control device to execute the segmented baking temperature control method for copper-clad aluminum enameled wire described in any of the first aspects above.

[0011] It is understood that the beneficial effects of the second to fifth aspects mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a schematic diagram of the structure of a segmented baking oven provided in one embodiment of this application; Figure 2 This is a schematic flowchart of a segmented baking temperature control method for copper-clad aluminum enameled wire provided in an embodiment of this application; Figure 3 This is a schematic diagram of the segmented baking temperature programmable logic controller for copper-clad aluminum enameled wire provided in the embodiments of this application; Figure 4 This is a schematic diagram of the segmented baking temperature control device provided in the embodiments of this application. Detailed Implementation

[0014] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0015] In related technologies, the current industry standard is to set fixed temperature values ​​for each temperature control zone, with each zone using an independent PID controller to maintain stable furnace gas temperature. However, the thermal expansion coefficient of the aluminum core in copper-clad aluminum conductors is approximately 1.36 times that of the copper cladding. During heating, the aluminum core expands significantly faster than the copper cladding, generating radial tensile stress at the aluminum-copper interface and forming a micron-level transient gap. This gap is equivalent to introducing additional thermal resistance at the copper-aluminum interface, hindering heat conduction from the copper cladding to the aluminum core. This results in a significant lag in the aluminum core temperature response compared to the surface, a phenomenon known as "bimetallic interface thermal conduction dynamic degradation." This degradation effect, coupled with the inherent non-uniformity of the furnace's spatial temperature, causes inconsistent deviations between the actual conductor surface temperature and the target process temperature in each temperature control zone. Existing fixed-temperature PID control methods cannot detect or respond to these dynamic changes in internal heat conduction within the conductor, ultimately leading to uneven curing of the coating film, significantly reduced insulation reliability, and decreased mechanical flexibility.

[0016] To address the aforementioned issues, this application provides a segmented baking temperature control method for copper-clad aluminum enameled wire. First, the target surface temperature of each temperature control unit is pre-stored. This step involves pre-storing the target surface temperature of each unit within each temperature control unit. Second, within each control cycle, based on the furnace gas temperature, the surface temperature of the copper-clad aluminum wire, and their respective target surface temperatures of each temperature control unit, a bimetallic thermal runaway index for each temperature control unit in the current control cycle is calculated. This bimetallic thermal runaway index reflects the degree to which the surface temperature of the copper-clad aluminum wire deviates from its target surface temperature within each temperature control unit, as well as the comprehensive thermal response nonuniformity of the dynamic degradation of thermal conduction at the copper-aluminum bimetallic interface. It can quantitatively characterize the degree of thermal response nonuniformity of the copper-clad aluminum wire bimetallic structure under current operating conditions. Furthermore, because this index uses the target surface temperature of each unit as the normalization benchmark rather than the overall line temperature uniformity benchmark, the inherent process temperature difference between different temperature control units will not be misjudged as abnormal. Then, the maximum value of the bimetallic thermal runaway scheduling index of each temperature control unit is compared with the preset first threshold and second threshold. According to the comparison result, the temperature control strategy for the current control cycle is selected from a multi-level temperature control strategy pool containing at least three different temperature control strategies according to the preset hysteresis switching rule. In this step, the corresponding temperature control response level is automatically matched according to the level of the thermal runaway scheduling index: when the index is low, global unified PID control is executed; when only some units have slight deviations, local compensation is superimposed; when there are serious deviations across the entire line, independent PID of each unit is activated and a coating feedforward compensation is introduced. The hysteresis switching rule sets a hysteresis width at the strategy switching boundary, so that small fluctuations of the maximum value around the threshold will not cause frequent strategy switching, effectively avoiding oscillation of the control system. Finally, based on the selected temperature control strategy, heater control signals are generated for each temperature control unit to adjust the output power of the heating elements within each temperature control unit. In this step, the heater control signals are generated according to the selected strategy, and when the temperature control strategy switches, the heater control signals achieve a smooth transition with a preset gradual change rate. This avoids the drastic disturbances in the furnace gas temperature within each temperature control unit caused by the step-like abrupt change in the control signal during strategy switching in traditional control methods, ensuring the continuous stability of the baking process during switching. In this method, a complete closed loop of dual temperature sensing, quantization, hierarchical strategy, and hysteresis-based smooth output is used. During most of the steady-state time, only a low-computational-overhead strategy needs to be run, while the response level is automatically upgraded under abnormal conditions. This approach balances control accuracy, response speed, and system stability, effectively solving the technical problem of uneven coating curing caused by the dynamic degradation of thermal conduction at the bimetallic interface during the segmented baking process of copper-clad aluminum enameled wire.

[0017] The segmented baking temperature control method for copper-clad aluminum enameled wire provided in this application embodiment can be applied to segmented baking ovens, specifically to segmented baking temperature control equipment. In this case, the segmented baking temperature control equipment is the executing entity of the segmented baking temperature control method for copper-clad aluminum enameled wire provided in this application embodiment. This application embodiment does not impose any restrictions on the specific type of segmented baking temperature control equipment.

[0018] The segmented baking oven may include a segmented baking oven body and a programmable logic controller (PLC). The segmented baking oven body includes M temperature control units (M ≥ 3), and each temperature control unit is set with a different target surface temperature depending on the baking stage. Each temperature control unit includes: a first temperature sensor (which may be a type K thermocouple), vertically positioned at the center of the top of the oven chamber, 5 to 10 cm from the wire path, for measuring the oven chamber gas temperature; a second temperature sensor (which may be an infrared temperature probe), operating in the 8 to 14 micrometer wavelength band, installed above the unit outlet side with its optical axis vertically aligned with the wire surface, for measuring the surface temperature of the copper-clad aluminum wire; and an electric heating element, regulated by the PLC via a solid-state relay using PWM. Heat insulation baffles are provided between each unit to reduce thermal crosstalk. The PLC communicates with all temperature control units to execute the segmented baking temperature control method for copper-clad aluminum enameled wire described in this application. The structure of the segmented baking oven is as follows: Figure 1 As shown.

[0019] For example, a programmable logic controller can be either a programmable logic controller or a stand-alone industrial control computer.

[0020] To better understand the segmented baking temperature control method for copper-clad aluminum enameled wire provided in this application embodiment, the specific implementation process of the segmented baking temperature control method for copper-clad aluminum enameled wire provided in this application embodiment will be described by way of example below.

[0021] Figure 2 This illustration shows a schematic flowchart of a segmented baking temperature control method for copper-clad aluminum enameled wire provided in an embodiment of this application. The segmented baking temperature control method for copper-clad aluminum enameled wire includes: S100, pre-stores the target surface temperature of each temperature control unit.

[0022] It is understood that the target surface temperature refers to the expected surface temperature of the enameled wire in each temperature control unit. The target surface temperature of each temperature control unit can be stored in the programmable logic controller or in the independent memory of each temperature control unit.

[0023] For example, for a baking oven with 6 temperature control units, the target surface temperature of each unit can be 160°C, 240°C, 315°C, 385°C, 400°C and 130°C respectively. The first 5 units (units 1 to 5) are the heating section, transition section and curing section participating in the coating curing process, each with its own target surface temperature value for the conductor required by the process. Unit 6 is the cooling section with a lower target temperature, used for cooling the conductor before it leaves the baking oven.

[0024] Optionally, the target surface temperature of each temperature control unit can be determined by looking up the information from a preset process formula table based on the specifications of the copper-clad aluminum conductor (such as the copper layer ratio and the diameter of the bare wire), the type of insulating varnish (such as polyester varnish, polyurethane varnish, etc.), and the current coating pass index.

[0025] S200, within each control cycle, calculates the bimetallic thermal runaway index for each temperature control unit based on the furnace gas temperature, copper-clad aluminum conductor surface temperature, and their respective target surface temperatures. The bimetallic thermal runaway index reflects the degree to which the surface temperature of the copper-clad aluminum conductor deviates from its target surface temperature within each temperature control unit, as well as the overall thermal response nonuniformity reflecting the degree of dynamic degradation of thermal conduction at the copper-aluminum bimetallic interface.

[0026] It is understandable that the Bimetallic Thermal Displacement Metric (DBM) index is a comprehensive quantitative indicator used to measure the degree to which the thermal response of copper-clad aluminum conductors in each temperature control unit deviates from its intended process state under current operating conditions. The core design principle of the DBM index is to avoid using the deviation of the actual temperature of each unit from the overall line average temperature to measure thermal non-uniformity. This is because different units have different target temperatures due to process requirements (e.g., the first unit targets 160℃ while the fifth unit targets 400℃). Using the overall line average temperature as a benchmark would misjudge normal process temperature differences as abnormal. This step uses the target surface temperature of each unit as a normalization benchmark, ensuring that under normal operating conditions, as long as each unit reaches its target value, its DBM index approaches zero or a minimum value. Only when the actual temperature of a certain unit significantly deviates from its own target value will the index increase.

[0027] For example, the DBM index is calculated once in each control cycle. The duration of the control cycle is usually set to 0.5 to 2 seconds, preferably 1 second, which is short enough compared to the thermal time constant of the oven (30 to 300 seconds). This ensures the real-time responsiveness of the thermal process and provides sufficient computational margin for DBM calculation, strategy switching determination, and feedforward model calculation within the PLC.

[0028] In one possible implementation, in S200, based on the furnace gas temperature, the surface temperature of the copper-clad aluminum conductor, and their respective target surface temperatures of each temperature control unit, the bimetallic thermal runaway scheduling index for each temperature control unit in the current control cycle is calculated, including: S210, for each temperature control unit, calculate the surface temperature deviation of the copper-clad aluminum conductor relative to the target surface temperature, and use the ratio of the absolute value of the surface temperature deviation to the target surface temperature to form the surface temperature deviation component of the unit.

[0029] The surface temperature deviation refers to the difference between the actual surface temperature of the copper-clad aluminum conductor measured at the outlet side of each temperature control unit and the target surface temperature stored in that unit. A positive value indicates that the conductor surface is overheated (exceeding the target temperature), while a negative value indicates that the conductor surface is underheated (below the target temperature). The deviation is normalized by dividing the absolute value of the surface temperature deviation by the unit's own target surface temperature. For example, a unit with a target temperature of 160℃ deviating by 5℃ is approximately 3.1% more than a unit with a target temperature of 400℃ deviating by 5℃. The normalized deviation component fairly reflects the relative degree to which each unit deviates from its respective process state, making units with different target temperatures comparable.

[0030] S220, calculate the gas-solid temperature difference between the furnace gas temperature and the surface temperature of the copper-clad aluminum conductor in each temperature control unit, and the average gas-solid temperature difference of all temperature control units. The gas temperature difference deviation component of the unit is formed by the ratio of the absolute value of the gas-solid temperature difference deviation of each unit from the average gas-solid temperature difference to the furnace gas temperature of that unit.

[0031] As can be understood, the gas-solid temperature difference (GST) refers to the difference between the furnace gas temperature and the conductor surface temperature, reflecting the driving force for heat transfer from the hot gas in the furnace to the conductor surface. Under normal operating conditions, the GST of each unit should remain at a roughly stable level. However, under abnormal operating conditions, such as when copper-aluminum interface degradation causes heat to accumulate on the copper cladding surface and cannot be effectively conducted to the aluminum core, the surface temperature rises abnormally, and the GST decreases abnormally. In this case, the GST of that unit will deviate significantly from the average GST of the entire line. Using the magnitude of the deviation from the average as the gas temperature difference deviation component can capture localized, hidden thermal response anomalies such as copper-aluminum interface degradation.

[0032] S230: Based on the difference in conductor surface temperature between the current control cycle and the previous control cycle, and the duration of the control cycle, calculate the surface heating rate of the copper-clad aluminum conductor in each temperature control unit of the current control cycle; calculate the bimetallic interface degradation factor based on the heating rate. The degradation factor increases with the heating rate during the conductor heating phase and takes a value of one during the conductor constant temperature or cooling phase; multiply the degradation factor by the surface temperature deviation component as the corrected surface temperature deviation component.

[0033] It is understandable that the surface heating rate of copper-clad aluminum conductors is calculated using the rate of change of conductor surface temperature rather than the rate of change of furnace gas temperature. This is because the temperature change of the furnace gas can be affected by factors such as heating power adjustment and airflow disturbances, and cannot accurately reflect the thermal response state of the conductor itself. Furthermore, the conductor's own heating rate directly determines the transient expansion difference between the metals on both sides of the copper-aluminum interface, and the coefficient of thermal expansion of the aluminum core is approximately... The coefficient of thermal expansion of the copper cladding is approximately The aluminum core is approximately 1.4 times larger than the copper cladding. The faster the conductor heats up, the greater the instantaneous expansion of the aluminum core relative to the copper cladding, resulting in greater radial tensile stress at the interface. This leads to more severe micron-level transient gaps and more drastic degradation of interfacial thermal conductivity. When the conductor is at a constant or decreasing temperature, the expansion of the aluminum core and copper cladding tends to be synchronized, or the aluminum core gradually contracts and recovers. No additional transient gaps are generated at the interface, therefore the degradation factor is set to one, indicating that no degradation correction is applied. For example, the heating rate is calculated by dividing the difference between the conductor surface temperature measured in the current control cycle and the conductor surface temperature recorded in the previous control cycle by the control cycle duration (e.g., 1 second). For instance, if the conductor surface temperature in the current cycle is 252°C, and in the previous cycle it was 237°C, and the control cycle is 1 second, then the heating rate is (252-237) / 1 = 15°C / s. The degradation factor is calculated as follows: Degradation factor = 1 + Material degradation sensitivity coefficient × Heating rate ÷ Reference heating rate. The reference heating rate can be taken as 10°C / s, and the material degradation sensitivity coefficient can be taken as 0.40. Taking the above 15°C / s as an example, the degradation factor = 1 + 0.40 × 15 / 10 = 1.6. A degradation factor greater than one means that the same surface temperature deviation will be amplified by 1.6 times when the conductor is rapidly heated.

[0034] S240: The corrected surface temperature deviation component and gas temperature difference deviation component are weighted and fused using a preset bimetallic sensitivity coefficient to obtain the bimetallic thermal runaway index of the unit. The maximum value of the bimetallic thermal runaway index is selected only from the bimetallic thermal runaway indexes corresponding to the temperature control units involved in the coating curing process, excluding the temperature control units corresponding to the cooling section at the end of the baking oven used for wire cooling and not involved in the coating cross-linking and curing reaction. When there is no independent cooling section at the end of the baking oven, the maximum value is selected from the bimetallic thermal runaway indexes of all temperature control units.

[0035] It is understandable that the bimetallic sensitivity coefficient α determines the weights of the corrected surface temperature deviation component and the gas temperature difference deviation component in the DBM index. The value of α typically ranges from 0.3 to 0.7. A larger α indicates a greater weight for the surface temperature deviation component, meaning the index is more sensitive to deviations in conductor surface temperature from the target value; a smaller α indicates a greater weight for the gas temperature difference deviation component, meaning the index is more sensitive to implicit thermal response anomalies reflected by changes in gas-solid temperature difference. The specific value of α should be set according to the specifications of the copper-clad aluminum conductor, especially the ratio of the copper cladding thickness to the aluminum core diameter.

[0036] For example, the DBM index is fused using a weighted summation: DBM = α × corrected surface temperature deviation component + (1-α) × gas temperature difference deviation component. The reason for using weighted fusion instead of simple addition is that the surface temperature deviation component and the gas temperature difference deviation component reflect different aspects of the same thermal response nonuniformity phenomenon, and there is a certain complementary relationship between them. The surface temperature deviation component is a direct external manifestation, while the gas temperature difference deviation component is an indirect internal symptom. Weighted fusion allows the DBM index to possess both sensitivity and robustness. Taking α=0.6 as an example, if the corrected surface temperature deviation component of a certain unit is 0.048 and the gas temperature difference deviation component is 0.0146, then DBM = 0.6 × 0.048 + 0.4 × 0.0146 = 0.0346.

[0037] Optionally, in calculating the maximum value of the DBM index, only the maximum value is selected from the temperature control units involved in the paint film curing process, excluding the cooling section at the end of the baking oven. The paint film curing process only involves the heating section, the transition section, and the curing section. The function of the end cooling section is to cool down the cured wires before they leave the oven. Its temperature is naturally lower than the process target temperature and it does not participate in the paint film crosslinking reaction.

[0038] Optionally, in S240, the bimetallic sensitivity coefficient is set based on the ratio of the thickness of the copper cladding layer to the diameter of the aluminum core in the copper-clad aluminum conductor, satisfying the relationship that the larger the proportion of the copper cladding layer thickness, the smaller the bimetallic sensitivity coefficient; the material degradation sensitivity coefficient in the degradation factor is set based on the absolute value of the difference between the thermal expansion coefficient of the aluminum core and the thermal expansion coefficient of the copper cladding layer in the copper-clad aluminum conductor, satisfying the relationship that the larger the absolute value, the larger the material degradation sensitivity coefficient.

[0039] The setting rule for the bimetallic sensitivity coefficient α is understandable based on the following physical mechanism: the greater the thickness of the copper cladding in the copper-clad aluminum conductor (i.e., the larger the proportion of copper), the stronger the mechanical constraint of the copper cladding on the thermal expansion of the aluminum core. The weaker the influence of copper-aluminum interface degradation on the conductor surface temperature signal measured by external infrared thermography, the less likely α should be reduced to decrease the weight of the surface temperature deviation component and correspondingly increase the weight of the gas temperature difference deviation component, thus enhancing the DBM index's ability to detect latent thermal response anomalies. Conversely, the thinner the copper cladding, the stronger the interference of interface degradation on external signals. The DBM index should rely more on the direct information of surface temperature; therefore, α should be taken as a larger value.

[0040] It is understandable that the calibration rule for the material degradation sensitivity coefficient γ is based on the following physical mechanism: the larger the absolute value of the difference between the thermal expansion coefficients of the aluminum core and the copper cladding, the more significant the difference in the expansion rates of the two metals during the heating process. This results in a larger transient gap at the copper-aluminum interface under the same heating rate, and a more severe interface degradation effect. Therefore, γ should be taken as a larger value to fully amplify the correction effect of the degradation factor on the DBM index. The calibration of γ can be accomplished through comparative experiments using thermal imaging of copper-clad aluminum conductors with different copper layer ratios and aluminum core diameters: measuring the response curves of the conductor surface temperature to the furnace gas temperature at different heating rates, and determining the value of γ by comparing the differences between the annealed state (without interface degradation) and the actual operating state.

[0041] S300: The maximum value of the bimetallic thermal runaway scheduling index of each temperature control unit is compared with a preset first threshold and a second threshold. Based on the comparison result, a temperature control strategy for the current control cycle is selected from a multi-level temperature control strategy pool containing at least three different temperature control strategies according to a preset hysteresis switching rule. Wherein, the first threshold is less than the second threshold, and each temperature control strategy generates a control signal for the heating element configured in the temperature control unit through at least one feedback controller.

[0042] The design philosophy of the multi-level temperature control strategy pool is to automatically match the corresponding temperature control response level based on the DBM_max level. When DBM_max is small (DBM_max is less than the first threshold ε1), it indicates that all units in the entire line are close to their respective process target states, and only normal global unified control needs to be maintained. When DBM_max is medium (DBM_max is greater than the first threshold ε1 and less than the second threshold ε2), it indicates that there is a slight deviation in a local area, and additional compensation can be applied to the problematic unit without upgrading the control level across the entire line. When DBM_max is large (DBM_max is greater than the second threshold ε2), it indicates that there is a serious deviation in the overall thermal response, and independent control and feedforward compensation for each unit need to be activated. This hierarchical response architecture allows the system to operate with minimal computational and control overhead for most of the normal operating time, upgrading the response level only when necessary, thus balancing control accuracy and operating efficiency.

[0043] In one possible implementation, the multi-level temperature control strategy pool in S300 includes a first strategy, a second strategy, and a third strategy: First strategy: The first strategy is executed when the maximum value of the bimetallic thermal runaway index is less than the first threshold. A unified global feedback controller generates the same heater control signal for each temperature control unit. It is suitable for steady-state conditions where the thermal response of the entire line tends to be consistent and the surface temperature of each unit has approached its respective target surface temperature.

[0044] Understandably, the first strategy is the basic control mode with the lowest computational overhead and the most stable system behavior among the three-level strategy pool. When DBM_max is less than the first threshold, it indicates that all temperature control units across the entire line are in good process condition, meaning that the deviation between the actual surface temperature of each unit and its respective target surface temperature is within an acceptable range, and the copper-aluminum interface degradation effect has not caused significant disturbance to the overall thermal response. At this time, only a unified global PID controller needs to output the same heater control signal to all units to meet the control requirements, without the need for differentiated control of each unit. The first strategy is executed for the vast majority of normal operating times and is the system's default steady-state control mode.

[0045] For example, the typical value of the first threshold ε1 is 0.03. When DBM_max < 0.03, it indicates that the relative deviation of the DBM index of each unit is within 3%, and the process condition is excellent.

[0046] Second strategy: The second strategy is executed when the maximum value of the bimetallic thermal runaway index is greater than or equal to the first threshold and less than the second threshold. Based on the output signal of the global feedback controller, for temperature control units whose bimetallic thermal runaway index exceeds the first threshold, a compensation increment proportional to the deviation of the surface temperature of the unit is superimposed to the heater control signal of the corresponding unit. The output of the global feedback controller remains unchanged for the remaining temperature control units. This strategy is suitable for operating conditions where only some units show slight thermal response deviation.

[0047] The second strategy is understandable; it's a targeted compensation mode for minor deviations in thermal response occurring locally. When DBM_max falls between the first and second thresholds, it indicates that only some units across the entire line have deviated, such as a thinner incoming copper layer causing reduced heat capacity in some unit conductors and excessively rapid temperature rise. Therefore, for temperature control units where DBM exceeds the first threshold, an additional compensation increment proportional to the surface temperature deviation is added, with larger compensation amounts for greater deviations. Other units that do not exceed the threshold maintain their global PID output unchanged.

[0048] For example, a typical value for the second threshold ε2 is 0.08. When 0.03 ≤ DBM_max < 0.08, the second strategy is executed. A typical value for the compensation gain coefficient is 2.5. For example, if the DBM of unit 2 is 0.0626 (exceeding ε1 = 0.03) and the surface temperature deviation is +12℃ (higher than the target value), then the compensation increment is 2.5 × (+12) = +30, which is added to the heater control signal of that unit. After about 3 to 5 control cycles, the surface temperature of the unit returns to near the target value, DBM_max falls back below ε1, and the system switches back to the first strategy. The direction of the compensation increment needs to be determined according to the actual control logic and physical effects: if the surface temperature is higher than the target value, a positive compensation increment means increasing the heater control signal to increase the heating power to compensate for insufficient heat; if the surface temperature is lower than the target value, a negative compensation increment means reducing the heating power of the unit to avoid overheating or overcompensation.

[0049] The third strategy is executed when the maximum value of the bimetallic thermal runaway index is greater than or equal to the second threshold. It activates the independent feedback controller of each temperature control unit and introduces a feedforward temperature compensation amount into the temperature setpoint of each independent feedback controller. The feedforward temperature compensation amount is calculated based on the coating state and routing speed of the copper-clad aluminum conductor and is suitable for the condition where the thermal response of the entire line deviates significantly.

[0050] Understandably, the third strategy represents the strongest response mode when a significant deviation in thermal response occurs across the entire production line. When DBM_max ≥ ε2, the process state of each unit across the entire line has deviated significantly and extensively. For example, a sudden and substantial increase in the fabrication speed may lead to insufficient residence time of the conductors in each unit, or a significant change in the incoming material specifications may alter the thermal response characteristics of the entire line. At this point, relying solely on global PID control with local compensation is insufficient to effectively correct the deviation across the entire line. It is necessary to activate the independent PID controllers of each temperature control unit to perform customized control for each unit. Simultaneously, a feedforward temperature compensation is introduced into the temperature setpoint of each independent PID controller. This compensation is pre-calculated based on the real-time measurement of the wet film thickness and fabrication speed at the coating station, allowing the control loop to make predictive temperature adjustments before the actual baking deviation occurs, resulting in a response speed superior to traditional pure feedback control.

[0051] For example, the temperature setpoint of each unit's independent PID controller is: Temperature setpoint = Target surface temperature of the unit + Feedforward temperature compensation. Taking a sudden increase in routing speed from 100m / min to 140m / min as an example, the surface temperature of the conductors in each unit drops by about 20 to 30°C, and DBM_max may exceed 0.08, triggering the third strategy. The feedforward compensation is calculated based on the deviation between the real-time routing speed and the rated routing speed, as well as the deviation between the real-time wet film thickness and the rated wet film thickness. For example, if the feedforward temperature compensation of a certain unit is 23°C, then the temperature setpoint of the independent PID controller of that unit = T_set[i] + 23°C. After about 40 to 50 seconds, the temperature of the entire line returns to normal, DBM_max falls below ε2, and the system gradually recovers to the second strategy.

[0052] In one possible implementation, the hysteresis handover rules in S300 include: S310, when the current execution strategy is the first strategy, when the maximum value of the bimetallic thermal runaway index is detected to reach or exceed the first threshold, switch from the first strategy to the second strategy.

[0053] It is understandable that when DBM_max is detected to reach or exceed the first threshold, it means that the entire process state has degraded from steady state to at least a local anomaly. Therefore, the system switches from the first strategy to the second strategy, applying local compensation to the cells with excessive DBM. This gradual response strategy can avoid over-control and system oscillation caused by direct response.

[0054] S320, when the current execution strategy is the second strategy, when the maximum value of the bimetallic thermal runaway index is detected to drop below the value obtained by subtracting the preset hysteresis width from the first threshold, switch from the second strategy back to the first strategy; when the maximum value of the bimetallic thermal runaway index is detected to reach or exceed the second threshold, switch from the second strategy to the third strategy.

[0055] Understandably, when the current execution strategy is the second strategy, the system faces two possible switching directions: First, an upward switch occurs when DBM_max further deteriorates, reaching or exceeding the second threshold ε2, indicating that a local anomaly has developed into a severe anomaly across the entire line. In this case, the system switches from the second strategy to the third strategy, initiating independent PID control and feedforward compensation across the entire line. Second, a downward recovery occurs when DBM_max continuously improves, dropping below ε1 minus the hysteresis width Δh, indicating that the anomaly has been eliminated and the entire process has returned to a steady-state level. In this case, the system switches back from the second strategy to the first strategy, restoring globally unified PID control and reducing system computational overhead. The recovery condition requires DBM_max to drop to ε1-Δh rather than ε1, avoiding repeated strategy switching when DBM_max fluctuates slightly around the threshold.

[0056] For example, a typical value for the hysteresis width Δh is 0.01. When ε1=0.03 and Δh=0.01, the threshold for switching back to the first strategy from the second strategy is ε1-Δh=0.02, meaning that DBM_max needs to drop below 0.02 to revert to the first strategy, while the threshold for triggering a switch from the first strategy to the second strategy is 0.03. The 0.01 difference between these two thresholds is the hysteresis interval.

[0057] S330, when the current execution strategy is the third strategy, if the maximum value of the bimetallic thermal runaway index is detected to drop below the value obtained by subtracting the preset hysteresis width from the second threshold, switch back to the second strategy from the third strategy. The preset hysteresis width is greater than zero and less than half the difference between the second threshold and the first threshold.

[0058] It's understandable that, under the current execution strategy of strategy three, when DBM_max drops below ε2-Δh, it indicates that the severe anomaly across the entire line has been brought under control and the process state is gradually returning to normal. However, it's not advisable to directly revert to strategy one at this point. Instead, it's better to revert to strategy two first, maintaining a certain level of control. Once the process state is further confirmed to be stable, the process can then naturally revert from strategy two back to strategy one. This step-by-step revert design ensures that the recovery from severe anomaly to normal steady state is gradual and controllable, avoiding system instability that might be caused by sudden and significant jumps in control levels.

[0059] S400 generates heater control signals for each temperature control unit according to the selected temperature control strategy, so as to adjust the output power of the heating element in each temperature control unit. When the temperature control strategy is switched, the heater control signal smoothly transitions from the control signal value corresponding to the previous strategy to the control signal value corresponding to the new strategy at a preset gradual rate.

[0060] It is understandable that, based on the heater control signal generated by the selected temperature control strategy, the output power of the electric heating element in each temperature control unit is adjusted by pulse width modulation via a solid-state relay. During a continuous control cycle where the strategy does not switch, the PID controller within each strategy runs continuously, and the control signal changes smoothly. When the temperature control strategy switches, there may be a numerical step in the control signal before and after the switch, for example, a sudden change from the output value of the global PID to the output value of an independent PID with feedforward compensation. If directly applied to the heating element, the furnace gas temperature will experience severe disturbances due to the power jump, affecting the continuity of the baking process and the stability of the paint film curing quality. Therefore, the core design in this step is to introduce a gradual and smooth transition mechanism for the control signal when the strategy switches.

[0061] In one possible implementation, in S400, the heater control signal smoothly transitions from the control signal value corresponding to the pre-switching strategy to the control signal value corresponding to the post-switching strategy at a preset gradual rate, including: S410, within a preset number of control cycles after the temperature control strategy is switched, gradually and linearly transitions the heater control signal from the actual control signal value of the previous control cycle to the target control signal value calculated by the strategy after the switch along a preset linear rate of change, so as to avoid the oscillation of furnace gas temperature in each temperature control unit caused by the step change of the control signal.

[0062] It can be understood that the smooth transition of the heater control signal during strategy switching refers to the process of not directly applying the target control signal calculated by the new strategy to the heating element within a certain number of control cycles (i.e., a preset transition period) after the strategy switch occurs. Instead, the control signal gradually transitions from the actual value of the last control cycle before the switch to the target value calculated by the new strategy along a preset linear trajectory. The physical meaning of this approach is that both the electric heating element and the furnace gas have thermal inertia. A step-change control signal will induce temperature overshoot and oscillation; while a gradually transitioning signal matches the inertial characteristics of the thermal system, allowing the temperature to smoothly transition from one operating condition to another.

[0063] For example, the preset number of transition cycles can be 1 to 3 control cycles (i.e., 1 to 3 seconds), corresponding to a temperature change rate of approximately 5 to 15°C / s. For instance, if the equivalent temperature difference between the control signals before and after the switch is 10°C, and the transition cycle is set to 2 seconds, then the control signal corresponds to an equivalent change of 5°C within each control cycle, i.e., a gradual change rate of approximately 5°C / s. In each control cycle of the transition period, the actual output control signal value for the current control cycle is calculated using linear interpolation based on the number of steps already completed and the remaining steps.

[0064] Optionally, a laser diameter gauge and a speed encoder are installed before the entrance of the baking oven and at the exit of the coating station. The laser diameter gauge is used to measure the outer diameter of the copper-clad aluminum conductor after it has been coated with insulating varnish in real time, and calculates the real-time wet film thickness based on the known diameter of the bare copper-clad aluminum conductor. The speed encoder is used to measure the real-time routing speed of the copper-clad aluminum conductor. The feedforward temperature compensation includes a basic thermal compensation component and a bimetallic interface degradation thermal compensation component. Basic thermal compensation component: The basic thermal compensation component is determined jointly based on the deviation of the real-time trace speed from the rated trace speed and the deviation of the real-time wet film thickness from the rated wet film thickness. Specifically, the basic thermal compensation component is used to compensate for the imbalance between heat supply and demand caused by changes in the residence time of the conductor in each temperature control unit and changes in the heat capacity of the wet coating film.

[0065] It is understandable that the basic thermal compensation component is used to compensate for the imbalance between heat supply and demand caused by deviations in conductor routing speed and wet film thickness from the rated values. Deviations in routing speed from the rated value can be categorized into two scenarios: when the routing speed is higher than the rated value, the residence time of the conductor in each temperature control unit is shortened, and the heat that needs to be transferred to the conductor per unit time increases, thus requiring increased heating power to provide more heat; when the routing speed is lower than the rated value, the residence time of the conductor is prolonged, requiring a reduction in heating power to avoid overheating. The effect of deviations in wet film thickness from the rated value is similar: the greater the wet film thickness, the thicker the wet insulating varnish layer coated on the conductor surface, and the greater the additional heat required for solvent vaporization and resin crosslinking, thus requiring a higher temperature to provide more heat.

[0066] The bimetallic interface degradation thermal compensation component is proportional to the degradation factor and the portion of the heating rate exceeding the preset lower limit threshold, and decreases exponentially as the index of the temperature control unit along the conductor travel direction increases. This component compensates for the heat supply-demand imbalance caused by the intense degradation effect of the bimetallic interface in the initial heating unit and its gradual disappearance in the subsequent curing unit.

[0067] It is understandable that the bimetallic interface degradation heat compensation component is used to compensate for the heat supply and demand imbalance caused by the uneven distribution of the copper-aluminum interface degradation effect in the front and rear sections. The design of the bimetallic interface degradation heat compensation component is based on the following physical laws: the bimetallic interface degradation effect is most severe in the heating unit of the front section of the baking furnace (because the heating rate of the conductor is high and the expansion rate of aluminum and copper is significantly different), and the transient gap effect is prominent; as the conductor temperature rises and gradually approaches the furnace gas temperature in the rear curing unit, the heating rate decreases, the expansion rate of aluminum and copper tends to be consistent, and the interface degradation effect gradually weakens or even disappears. Therefore, the degradation heat compensation component should be proportional to the degradation factor (the more severe the degradation, the greater the compensation), proportional to the portion of the heating rate exceeding the lower limit threshold of the heating rate (degradation compensation is only activated when the heating rate exceeds a certain level), and decrease exponentially with the increase of the index (i.e., unit number) of the temperature control unit (matching the spatial distribution law of the degradation effect gradually weakening along the direction of conductor travel).

[0068] For example, a typical value for the lower limit threshold of the heating rate is 5°C / s. When the heating rate of the conductor surface does not exceed 5°C / s, no degradation heat compensation occurs (because the heating rate is low at this point, the expansion difference on both sides of the copper-aluminum interface is still within the reversible range of the material's elastic deformation, and no significant transient gap will occur). A typical value for the attenuation constant is 2.0, meaning that the degradation compensation decreases to about 37% of its original value after passing through two temperature control units. For example, the degradation heat compensation component of unit 1 is the largest, the degradation heat compensation component of unit 3 is about 37% of that of unit 1, and the degradation heat compensation component of unit 5 has decreased to about 14% of that of unit 1.

[0069] Optionally, the copper-clad aluminum enameled wire undergoes multiple coating and baking cycles, with the pass index increasing from the first pass to the Kth pass. Under different passes, the target surface temperature of each temperature control unit increases sequentially with the pass index by a preset temperature rise increment per pass, in order to compensate for the effect of the increase in the total heat capacity of the conductor on the heat conduction rate caused by the gradual accumulation of the cured insulating varnish layer in each pass, so that the actual curing degree of the varnish film in each pass remains consistent.

[0070] It is understandable that the complete manufacturing process of copper-clad aluminum enameled wire typically requires K coating-baking cycles, where K is usually 6 to 12. Each cycle completes the coating and baking of the insulating varnish, accumulating the insulation layer thickness layer by layer. As the cycle index increases, the cured insulating varnish film gradually thickens, and the total heat capacity of the conductor increases accordingly. This means that the temperature rise of the conductor in subsequent cycles will be less than that in previous cycles for the same amount of heat input. To compensate for this effect, the target surface temperature of each temperature control unit is synchronously increased by a preset temperature rise increment per cycle according to the predetermined temperature curve ratio of each unit, ensuring that the actual curing degree of the varnish film remains consistent across all cycles.

[0071] For example, the typical temperature rise increment per pass is 8 to 15°C, depending on the paint type and wire specifications. Taking a baking oven with 6 temperature control units as an example: the reference temperature for the first pass of Unit 1 is 160°C, and the reference temperature for the first pass of Unit 5 is 400°C. If the temperature rise increment per pass is 10°C, in the 8th pass, the target temperature of Unit 1 will increase proportionally to 160 + 10 × 7 = 230°C, and the target temperature of Unit 5 will increase proportionally to 400 + 10 × 7 = 470°C. The specific target temperature for each unit in the kth pass can be obtained by referring to the reference temperature of the first pass from the process formula table, and then each unit will increase its temperature rise by (k-1) × ΔT_pass.

[0072] Optionally, the bimetallic sensitivity coefficient α also decreases with increasing pass index. The physical basis for this decrease is that as the coating layer thickens with each pass, the proportion of components originating from copper-aluminum interface degradation in the conductor surface temperature signal measured by the external infrared thermometer decreases—because the thermal resistance of the coating layer shields the copper-aluminum interface from surface temperature disturbances. Therefore, the weight α of the surface temperature deviation component related to interface degradation in the DBM index should decrease with each pass, with a typical decrease of 0.05 per pass. For example, α = 0.6 for the first pass, and α = 0.6 - 0.05 × 7 = 0.25 for the eighth pass.

[0073] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0074] Corresponding to the segmented baking temperature control method for copper-clad aluminum enameled wire described in the above embodiments, this application also provides a programmable logic controller for segmented baking temperature of copper-clad aluminum enameled wire. Each unit of this device can implement each step of the segmented baking temperature control method for copper-clad aluminum enameled wire. Figure 3 The diagram shows a structural block diagram of a segmented baking temperature programmable logic controller for copper-clad aluminum enameled wire provided in an embodiment of this application. For ease of explanation, only the parts related to the embodiment of this application are shown.

[0075] Reference Figure 3 This device is applied to a segmented baking oven, wherein the segmented baking oven is divided into M spatially discrete temperature control units along the travel direction of the copper-clad aluminum conductor, where M is greater than or equal to 3. Each temperature control unit is equipped with a first temperature sensor and a second temperature sensor. The first temperature sensor is used to measure the furnace gas temperature within its respective temperature control unit, and the second temperature sensor is used to measure the surface temperature of the copper-clad aluminum conductor at the outlet side of its respective temperature control unit in a non-contact manner. The controller includes: The pre-storage unit is used to pre-store the target surface temperature of each temperature control unit. The thermal runaway scheduling calculation unit is used to calculate the bimetallic thermal runaway scheduling index of each temperature control unit in each control cycle, based on the furnace gas temperature, the surface temperature of the copper-clad aluminum conductor, and their respective target surface temperatures. The bimetallic thermal runaway scheduling index is used to reflect the degree to which the surface temperature of the copper-clad aluminum conductor in each temperature control unit deviates from its respective target surface temperature, as well as the comprehensive thermal response nonuniformity of the degree of dynamic degradation of thermal conduction at the copper-aluminum bimetallic interface. The temperature control strategy selection unit is used to compare the maximum value of the bimetallic thermal runaway scheduling index of each temperature control unit with a preset first threshold and a second threshold. According to the comparison result, it selects the temperature control strategy to execute the current control cycle from a multi-level temperature control strategy pool containing at least three different temperature control strategies according to a preset hysteresis switching rule. The first threshold is less than the second threshold, and each temperature control strategy generates a control signal for the heating element configured by the temperature control unit through at least one feedback controller. The temperature control unit is used to generate heater control signals for each temperature control unit according to the selected temperature control strategy, so as to adjust the output power of the heating element in each temperature control unit; wherein, when the temperature control strategy is switched, the heater control signal smoothly transitions from the control signal value corresponding to the strategy before the switch to the control signal value corresponding to the strategy after the switch at a preset gradual rate.

[0076] It should be noted that the information interaction and execution process between the above-mentioned units are based on the same concept as the method embodiments of this application. For details on their specific functions and technical effects, please refer to the method embodiments section, which will not be repeated here.

[0077] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units is merely an example. In practical applications, the above functions can be assigned to different functional units as needed, that is, the internal structure of the controller can be divided into different functional units to complete all or part of the functions described above. The functional units in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0078] This application also provides a segmented baking temperature control device. Figure 4This is a schematic diagram of a segmented baking temperature control device provided in an embodiment of this application. Figure 4 As shown, the programmable logic controller 4 of the segmented baking temperature control device in this embodiment includes: at least one processor 40 ( Figure 4 Only one is shown in the image), at least one memory 41 ( Figure 4 (Only one is shown in the image) and a computer program 42 stored in the at least one memory 41 and executable on the at least one processor 40. When the processor 40 executes the computer program 42, it causes the programmable logic controller 4 of the segmented baking temperature control device to implement the steps in any of the above embodiments of the segmented baking temperature control method for copper-clad aluminum enameled wire, or causes the programmable logic controller 4 of the segmented baking temperature control device to implement the functions of each unit in the above embodiments of the device.

[0079] For example, the computer program 42 may be divided into one or more units, which are stored in the memory 41 and executed by the processor 40 to complete this application. The one or more units may be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of the computer program 42 in the programmable logic controller 4 of the segmented baking temperature control device.

[0080] The programmable logic controller 4 of the segmented baking temperature control device can be a microcontroller, microprocessor, mobile phone, tablet computer, wearable device, vehicle device, laptop computer, ultra-mobile personal computer (UMPC), netbook, personal digital assistant (PDA), desktop computer, smart screen, smart TV, or handheld device with wireless communication capabilities. The programmable logic controller 4 of the segmented baking temperature control device may include, but is not limited to, a processor 40 and a memory 41. Those skilled in the art will understand that... Figure 4 This is merely an example of the programmable logic controller 4 for a segmented baking temperature control device and does not constitute a limitation on the programmable logic controller 4 for a segmented baking temperature control device. It may include more or fewer components than shown, or combine certain components, or different components, such as input / output devices, network access devices, buses, etc.

[0081] The processor 40 can be a Central Processing Unit (CPU), but it can also be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor.

[0082] In some embodiments, the memory 41 may be an internal storage unit of the programmable logic controller 4 (PLC) of the segmented baking temperature control device, such as a hard disk or memory of the PLC 4. In other embodiments, the memory 41 may be an external storage device of the PLC 4, such as a pluggable hard disk, smart media card (SMC), secure digital card (SD), flash card, etc., mounted on the PLC 4. Furthermore, the memory 41 may include both internal storage units and external storage devices of the PLC 4. The memory 41 is used to store operating systems, applications, bootloaders, data, and other programs, such as the program code of computer programs. The memory 41 can also be used to temporarily store data that has been output or will be output.

[0083] This application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps in any of the above method embodiments.

[0084] This application provides a computer program product that, when run on a segmented baking temperature control device, enables the segmented baking temperature control device to perform the steps described in any of the above method embodiments.

[0085] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments of this application can be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include at least: any entity or device capable of carrying computer program code to a segmented baking temperature control device, a recording medium, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, such as a USB flash drive, a portable hard drive, a magnetic disk, or an optical disk.

[0086] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0087] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0088] In the embodiments provided in this application, it should be understood that the disclosed segmented baking temperature control method, programmable logic controller, and segmented baking temperature control device for copper-clad aluminum enameled wire can be implemented in other ways. For example, the embodiments of the segmented baking temperature control method, programmable logic controller, and segmented baking temperature control device for copper-clad aluminum enameled wire described above are merely illustrative. For instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices, or units, and may be electrical, mechanical, or other forms.

[0089] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0090] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for segmented baking temperature control of copper-clad aluminum enameled wire, characterized in that, The method is applied to a segmented baking oven, wherein the segmented baking oven is divided into M spatially discrete temperature control units along the travel direction of the copper-clad aluminum conductor, where M is greater than or equal to 3. Each temperature control unit is equipped with a first temperature sensor and a second temperature sensor. The first temperature sensor is used to measure the furnace gas temperature within its respective temperature control unit, and the second temperature sensor is used to measure the surface temperature of the copper-clad aluminum conductor at the outlet side of its respective temperature control unit in a non-contact manner. The method includes: Pre-store the target surface temperature of each temperature control unit; Within each control cycle, based on the furnace gas temperature, the surface temperature of the copper-clad aluminum conductor, and their respective target surface temperatures of each temperature control unit, the bimetallic thermal runaway index of each temperature control unit in the current control cycle is calculated; wherein, the bimetallic thermal runaway index is used to reflect the degree to which the surface temperature of the copper-clad aluminum conductor in each temperature control unit deviates from its respective target surface temperature, as well as the comprehensive thermal response nonuniformity of the degree of dynamic degradation of thermal conduction at the copper-aluminum bimetallic interface. The maximum value of the bimetallic thermal runaway scheduling index of each temperature control unit is compared with a preset first threshold and a second threshold. Based on the comparison result, a temperature control strategy for the current control cycle is selected from a multi-level temperature control strategy pool containing at least three different temperature control strategies according to a preset hysteresis switching rule. Wherein, the first threshold is less than the second threshold, and each temperature control strategy generates a control signal for the heating element configured in the temperature control unit through at least one feedback controller. Based on the selected temperature control strategy, heater control signals are generated for each temperature control unit to adjust the output power of the heating element in each temperature control unit; wherein, when the temperature control strategy is switched, the heater control signal smoothly transitions from the control signal value corresponding to the strategy before the switch to the control signal value corresponding to the strategy after the switch at a preset gradual rate.

2. The segmented baking temperature control method for copper-clad aluminum enameled wire as described in claim 1, characterized in that, The calculation of the bimetallic thermal runaway scheduling index for each temperature control unit in the current control cycle, based on the furnace gas temperature, the surface temperature of the copper-clad aluminum conductor, and their respective target surface temperatures, includes: For each temperature control unit, the surface temperature deviation of the copper-clad aluminum conductor relative to the target surface temperature is calculated, and the surface temperature deviation component of the unit is formed by the ratio of the absolute value of the surface temperature deviation to the target surface temperature. Calculate the gas-solid temperature difference between the furnace gas temperature and the surface temperature of the copper-clad aluminum conductor in each temperature control unit, and the average gas-solid temperature difference of all temperature control units. The gas temperature difference deviation component of the unit is formed by the ratio of the absolute value of the gas-solid temperature difference deviation of each unit from the average gas-solid temperature difference to the furnace gas temperature of the unit. Based on the difference in conductor surface temperature between the current control cycle and the previous control cycle, and the duration of the control cycle, calculate the surface heating rate of the copper-clad aluminum conductor in each temperature control unit of the current control cycle; calculate the bimetallic interface degradation factor based on the heating rate, wherein the degradation factor increases with the heating rate during the conductor heating phase and takes a value of one during the conductor isothermal or cooling phase; and use the product of the degradation factor and the surface temperature deviation component as the corrected surface temperature deviation component. The corrected surface temperature deviation component and the gas temperature difference deviation component are weighted and fused using a preset bimetallic sensitivity coefficient to obtain the bimetallic thermal runaway index of the unit. The maximum value of the bimetallic thermal runaway index is selected only from the bimetallic thermal runaway indexes corresponding to the temperature control units participating in the coating curing process, excluding the temperature control units corresponding to the cooling section at the end of the baking oven used for wire cooling and not participating in the coating crosslinking and curing reaction. When the end of the baking oven does not have an independent cooling section, the maximum value is selected from the bimetallic thermal runaway indexes of all temperature control units.

3. The segmented baking temperature control method for copper-clad aluminum enameled wire as described in claim 2, characterized in that, The bimetallic sensitivity coefficient is set based on the ratio of the thickness of the copper cladding layer to the diameter of the aluminum core in the copper-clad aluminum conductor, satisfying the relationship that the larger the proportion of the copper cladding layer thickness, the smaller the bimetallic sensitivity coefficient; the material degradation sensitivity coefficient in the degradation factor is set based on the absolute value of the difference between the thermal expansion coefficient of the aluminum core and the thermal expansion coefficient of the copper cladding layer in the copper-clad aluminum conductor, satisfying the relationship that the larger the absolute value, the larger the material degradation sensitivity coefficient.

4. The segmented baking temperature control method for copper-clad aluminum enameled wire as described in claim 1, characterized in that, The multi-level temperature control strategy pool includes a first strategy, a second strategy, and a third strategy: The first strategy is executed when the maximum value of the bimetallic thermal runaway index is less than the first threshold. A unified global feedback controller generates the same heater control signal for each temperature control unit. This strategy is suitable for steady-state conditions where the thermal response of the entire line tends to be consistent and the surface temperature of each unit has approached its respective target surface temperature. The second strategy is executed when the maximum value of the bimetallic thermal runaway index is greater than or equal to the first threshold and less than the second threshold. Based on the output signal of the global feedback controller, for the temperature control unit whose bimetallic thermal runaway index exceeds the first threshold, a compensation increment proportional to the deviation of the unit's surface temperature is superimposed on the heater control signal corresponding to the unit. The output of the global feedback controller remains unchanged for the remaining temperature control units. This strategy is suitable for operating conditions where only some units exhibit slight thermal response deviation. The third strategy is executed when the maximum value of the bimetallic thermal runaway index is greater than or equal to the second threshold. It activates the independent feedback controller of each temperature control unit and introduces a feedforward temperature compensation amount into the temperature setpoint of each independent feedback controller. The feedforward temperature compensation amount is calculated based on the coating state and routing speed of the copper-clad aluminum conductor and is applicable to the condition where the thermal response of the entire line deviates significantly.

5. The segmented baking temperature control method for copper-clad aluminum enameled wire as described in claim 4, characterized in that, The hysteresis switching rules include: When the current execution strategy is the first strategy, when the maximum value of the bimetallic thermal runaway index is detected to reach or exceed the first threshold, the strategy is switched from the first strategy to the second strategy. When the current execution strategy is the second strategy, when the maximum value of the bimetallic thermal runaway index is detected to drop below the value obtained by subtracting the preset hysteresis width from the first threshold, the strategy is switched back to the first strategy; when the maximum value of the bimetallic thermal runaway index is detected to reach or exceed the second threshold, the strategy is switched to the third strategy. When the current execution strategy is the third strategy, when the maximum value of the bimetallic thermal runaway index is detected to drop below the value obtained by subtracting the preset hysteresis width from the second threshold, the strategy is switched back to the second strategy; wherein the preset hysteresis width is greater than zero and less than half of the difference between the second threshold and the first threshold.

6. The segmented baking temperature control method for copper-clad aluminum enameled wire as described in claim 4, characterized in that, The heater control signal smoothly transitions from the control signal value corresponding to the pre-switching strategy to the control signal value corresponding to the post-switching strategy at a preset gradual rate, including: Within a preset number of control cycles after the temperature control strategy is switched, the heater control signal is gradually and linearly transitioned from the actual control signal value of the previous control cycle to the target control signal value calculated by the strategy after the switch, along a preset linear rate of change, in order to avoid the oscillation of furnace gas temperature in each temperature control unit caused by the step change of the control signal.

7. The segmented baking temperature control method for copper-clad aluminum enameled wire as described in claim 4, characterized in that, A laser diameter gauge and a speed encoder are installed before the entrance of the baking oven and at the exit of the coating station. The laser diameter gauge is used to measure the outer diameter of the copper-clad aluminum conductor after it has been coated with insulating varnish in real time, and calculates the real-time wet film thickness based on the known diameter of the bare copper-clad aluminum conductor. The speed encoder is used to measure the real-time routing speed of the copper-clad aluminum conductor. The feedforward temperature compensation includes a basic thermal compensation component and a bimetallic interface degradation thermal compensation component. The basic thermal compensation component is determined jointly based on the deviation of the real-time wiring speed from the rated wiring speed and the deviation of the real-time wet film thickness from the rated wet film thickness; wherein, the basic thermal compensation component is used to compensate for the imbalance of heat supply and demand caused by the change in the residence time of the conductor in each temperature control unit and the change in the heat capacity of the wet coating film. The bimetallic interface degradation thermal compensation component is proportional to the degradation factor and the portion of the heating rate exceeding the preset lower limit threshold, and decreases exponentially as the index of the temperature control unit along the direction of wire travel increases; wherein, the bimetallic interface degradation thermal compensation component is used to compensate for the heat supply and demand imbalance caused by the bimetallic interface degradation effect being severe in the first heating unit and gradually disappearing in the second curing unit.

8. The segmented baking temperature control method for copper-clad aluminum enameled wire as described in claim 1, characterized in that, The copper-clad aluminum enameled wire undergoes multiple coating and baking cycles, with the cycle index increasing from the first cycle to the Kth cycle. Under different cycles, the target surface temperature of each temperature control unit increases sequentially with the cycle index by a preset temperature rise increment per cycle. This compensates for the impact of the increased total heat capacity of the conductor on the heat conduction rate caused by the gradual accumulation of the cured insulating varnish layer in each cycle, ensuring that the actual curing degree of the varnish film remains consistent across each cycle.

9. A segmented baking temperature programmable logic controller for copper-clad aluminum enameled wire, characterized in that, The controller is applied to a segmented baking oven, and the segmented baking oven is divided into M spatially discrete temperature control units along the travel direction of the copper-clad aluminum conductor, where M is greater than or equal to 3. Each temperature control unit is equipped with a first temperature sensor and a second temperature sensor. The first temperature sensor is used to measure the furnace gas temperature within its respective temperature control unit, and the second temperature sensor is used to measure the surface temperature of the copper-clad aluminum conductor at the outlet side of its respective temperature control unit in a non-contact manner. The controller includes: The pre-storage unit is used to pre-store the target surface temperature of each temperature control unit. The thermal runaway scheduling calculation unit is used to calculate the bimetallic thermal runaway scheduling index of each temperature control unit in each control cycle, based on the furnace gas temperature, the surface temperature of the copper-clad aluminum conductor, and their respective target surface temperatures. The bimetallic thermal runaway scheduling index is used to reflect the degree to which the surface temperature of the copper-clad aluminum conductor in each temperature control unit deviates from its respective target surface temperature, as well as the comprehensive thermal response nonuniformity of the degree of dynamic degradation of thermal conduction at the copper-aluminum bimetallic interface. The temperature control strategy selection unit is used to compare the maximum value of the bimetallic thermal runaway scheduling index of each temperature control unit with a preset first threshold and a second threshold. According to the comparison result, it selects the temperature control strategy to execute the current control cycle from a multi-level temperature control strategy pool containing at least three different temperature control strategies according to a preset hysteresis switching rule. The first threshold is less than the second threshold, and each temperature control strategy generates a control signal for the heating element configured by the temperature control unit through at least one feedback controller. The temperature control unit is used to generate heater control signals for each temperature control unit according to the selected temperature control strategy, so as to adjust the output power of the heating element in each temperature control unit; wherein, when the temperature control strategy is switched, the heater control signal smoothly transitions from the control signal value corresponding to the strategy before the switch to the control signal value corresponding to the strategy after the switch at a preset gradual rate.

10. A segmented baking temperature control device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the method as described in any one of claims 1 to 8.

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