Vacuum induction heating temperature closed-loop control system integrated with SCADA (supervisory control and data acquisition)

Abstract

The invention relates to the technical field of vacuum induction heating temperature control, and discloses a vacuum induction heating temperature closed-loop control system integrated with SCADA (supervisory control and data acquisition), which is characterized in that a functional material layer with preset Curie temperature is compounded on the surface of an induction coil, and the absolute value of phase difference is analyzed by collecting voltage and current signals of the coil in real time; according to the invention, through the synergistic effect of the electromagnetic impedance sudden change characteristic of the functional material layer and the phase difference detection mechanism, non-contact accurate control of the phase change critical temperature of the workpiece is realized; and meanwhile, due to the coupling application of the asymmetric micro-pulse waveform design and the dynamic adjustment strategy, the contradiction between thermodynamic response and electromagnetic interference in a vacuum environment is effectively balanced, and the control precision and stability of the system are remarkably improved.

Description

Technical Field

[0001] The present invention relates to a vacuum induction heating temperature closed-loop control system integrated with SCADA, belonging to the technical field of vacuum induction heating temperature control. Background Art

[0002] In the field of vacuum induction heating temperature control, the existing technology generally adopts a scheme combining multi-sensor feedback and dynamic regulation. Closed-loop control is achieved by arranging a temperature sensor array in the vacuum chamber and relying on high-frequency data acquisition. Although such methods can maintain basic temperature control accuracy under normal working conditions, their inherent limitations gradually emerge in the high-precision heat treatment process involving phase change critical temperatures.

[0003] Specifically, in a vacuum environment, sensors are vulnerable to electromagnetic interference and thermal radiation, making it difficult to balance the real-time performance and reliability of signal acquisition. Although redundant sensor configurations are intended to improve fault tolerance, they exacerbate signal conflicts and the complexity of compensation algorithms, resulting in system response delays and decreased stability. In addition, traditional dynamic regulation strategies regard temperature fluctuations as noise and forcefully suppress them, ignoring the non-linear self-organization characteristics of latent heat release during material phase changes and electromagnetic eddy current distribution in the vacuum heating process. Excessive intervention is likely to disrupt the internal thermal balance of the system and induce unpredictable hysteresis oscillation phenomena. For example, in the directional solidification process of superalloys, frequent power adjustments not only exacerbate the turbulence of the molten pool but also significantly increase the misalignment rate of temperature gradient control in the critical phase change region.

[0004] Based on this, the industry has tried to alleviate the above problems by optimizing sensor layouts or introducing advanced filtering algorithms. However, such improvements mainly focus on the signal processing level and do not address the essential contradiction between the temperature perception mechanism and the dynamic control logic in a vacuum environment. Therefore, how to construct a vacuum heating temperature closed-loop control mechanism based on in-situ electromagnetic property perception and adaptive power compensation to achieve high-precision steady-state control in the phase change critical region without relying on physical sensors has become the core technical problem to be solved in this field. Summary of the Invention

[0005] The present invention provides a vacuum induction heating temperature closed-loop control system integrated with SCADA, and its main purpose is to solve the problems of insufficient reliability of the traditional multi-sensor feedback mechanism in a vacuum environment, mismatch between the dynamic regulation strategy and the non-linear characteristics of material phase changes, resulting in a decrease in temperature control accuracy and damage to system stability.

[0006] To achieve the above object, a vacuum induction heating temperature closed-loop control system integrated with SCADA provided by the present invention includes: Construct an induction coil unit, on the surface of the conductor layer of which a functional material layer is compounded. The functional material layer has a preset Curie temperature, which matches the target temperature control region of the workpiece to be heated. And the functional material layer is regulated by a cold rolling deformation process so that the temperature range in which its electromagnetic impedance undergoes a significant mutation covers the phase change critical temperature range of the workpiece; A phase difference detection module that collects the voltage signal and current signal generated by the induction coil during operation in real time, and directly obtains the absolute value of the phase difference characterizing the electromagnetic characteristics of the induction coil based on the time difference between the voltage signal and the current signal , without the need for analog-to-digital conversion; A micro-pulse compensation unit. When the absolute value of the phase difference first exceeds a preset first threshold , it is determined that the temperature of the workpiece enters the phase change critical region, and the micro-pulse power compensation mode is immediately started to output micro-pulse power to the induction coil; In the micro-pulse power compensation mode, the amplitude of the micro-pulse and the change rate of the absolute value of the phase difference present a piecewise linear relationship, and the output interval of the micro-pulse is dynamically adjusted according to the real-time change of the absolute value of the phase difference until the absolute value of the phase difference falls back to a preset second threshold to achieve closed-loop control of the workpiece temperature.

[0007] In the micro-pulse power compensation mode, the amplitude of the micro-pulse and the change rate of the absolute value of the phase difference present a piecewise linear relationship, and the output interval of the micro-pulse is dynamically adjusted according to the real-time change of the absolute value of the phase difference until the absolute value of the phase difference falls back to a preset second threshold , thereby achieving closed-loop control of the workpiece temperature.

[0008] Preferably, the micro-pulse output in the micro-pulse power compensation mode is an asymmetric waveform, which is composed of alternating high-frequency narrow pulse width pulse trains and low-frequency wide pulse width pulse trains. The frequency of the high-frequency narrow pulse width pulse train is in the range of 8 kHz to 12 kHz, the pulse width is in the range of 8 μs to 12 μs, the frequency of the low-frequency wide pulse width pulse train is in the range of 0.8 kHz to 1.2 kHz, the pulse width is in the range of 80 μs to 120 μs, and satisfies the relationship , to maintain the energy density basically constant, thereby taking into account the heat compensation requirements of the workpiece while suppressing electromagnetic noise.

[0009] Preferably, the absolute value of the phase difference The time difference between the zero-crossing point of the voltage and the peak point of the current waveform is measured accurately through a phase-locked loop circuit and is obtained according to the formula where is the operating frequency of the induction coil, and the time resolution of the phase-locked loop circuit reaches the minimum time interval corresponding to 0.1°.

[0010] Preferably, when the SCADA system detects that the pressure fluctuation in the vacuum furnace chamber exceeds the preset threshold, the sampling frequency of the time difference is automatically increased from 1 kHz to 10 kHz, and the Kalman filter is enabled to predict and correct the sequence of continuous samples. The state equation and observation equation of the Kalman filter are as follows:

[0011]

[0012] where is the predicted value at time , is the change in vacuum degree at time , is the observed value at time , is the state transition matrix, is the control input matrix, is the observation matrix, and are the covariance matrices of the process noise and the observation noise respectively.

[0013] Preferably, the data acquisition module of the SCADA system is reconstructed into a time series database based on the absolute value of the phase difference , and a mapping relationship table between and the amplitude of the micro-pulse compensation power is established in advance. The mapping relationship table is optimized through off-line simulation combined with the thermophysical parameters of different workpiece materials. The material coefficient is introduced for different workpiece materials, and its calculation formula is: , where is the conductivity of the workpiece material, is the density of the workpiece material, and are the conductivity and density of the reference material, and is the empirical coefficient determined by multiple regression analysis of experimental data.

[0014] Preferably, during the process that the workpiece temperature enters and maintains in the phase transition critical region, the system automatically generates a thermal hysteresis compensation curve based on the data of the absolute value of the historical phase difference, and dynamically adjusts the output of the micro-pulse power according to the compensation amount, where is the proportionality factor related to the thermal diffusivity of the workpiece material.

[0015] Preferably, a periodically arranged micro-pit array is provided on the surface of the functional material layer. The diameter of the micro-pits is in the range of 50 μm to 100 μm, and the depth-to-diameter ratio is in the range of 1:1 to 1:2, which is used to form a turbulent effect on the surface of the functional material layer and enhance the heat dissipation efficiency of its surface.

[0016] Preferably, the system is integrated with a self-check module, which real-time monitors the standard deviation of the fluctuation of the absolute value of the phase difference within three consecutive working cycles. When is less than 0.5°, it automatically determines that the phase difference detection module has an abnormality, switches to the redundant detection channel, and records the signature containing the fault type and occurrence time into the event log of the SCADA system for fault diagnosis and maintenance.

[0017] Compared with the problems in the background art, the beneficial effects of the present invention are: 1. In the complex scenario of high-frequency electromagnetic interference and thermal radiation disturbance in a vacuum environment, through the synergistic effect of the Curie temperature characteristic of the functional material layer and the phase difference detection mechanism, the system can bypass the physical limitations of traditional temperature sensors and directly capture the essential relationship between the electromagnetic characteristics of the induction coil and the phase change state of the workpiece. When the workpiece temperature approaches the phase transition critical region, the electromagnetic impedance mutation characteristic of the functional material layer and the high-precision time difference detection of the phase-locked loop circuit form a two-way verification, triggering the precise intervention of the micro-pulse compensation mechanism, so as to achieve the autonomous balance control of the latent heat release process of the material phase change without the need for real-time temperature numerical feedback.

[0018] 2. Aiming at the industry problem of the mismatch between non-linear thermodynamic response and conventional power regulation during vacuum heating, the coupled application of the asymmetric micro-pulse waveform design and the dynamic adjustment strategy transforms the power compensation process into an adaptive matching process of thermal relaxation characteristics. The alternating output mode of high-frequency narrow pulse width pulses and low-frequency wide pulse width pulses, through the spectral feature recombination under the constraint of constant energy density, not only suppresses the electromagnetic harmonic resonance caused by traditional continuous power regulation, but also ensures the time-domain matching of the thermal inertia in the phase change region and the pulse energy input, forming a thermal-electric dynamic balance system with self-stabilizing characteristics. ​​​

[0019] 3. By reconstructing the data acquisition logic and processing paradigm of the SCADA system, the complex data stream based on traditional multi-sensor signal fusion is simplified into a one-dimensional analysis of phase difference time series characteristics. This mechanism utilizes the temperature-electromagnetic impedance conversion characteristics of the functional material layer to encode the thermodynamic state information into an electromagnetic phase signal that can be directly processed, thereby achieving the physical layer fusion of control parameters at the data acquisition source, significantly reducing the system's dependence on backend data processing algorithms, and remarkably enhancing the robustness and real-time response ability of the control system in a vacuum environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a data interaction timing diagram of the phase difference detection and self-check module of the integrated SCADA system of the present invention; Figure 2 It is a working flow chart of the induction coil unit and the phase difference detection module in a vacuum environment of the present invention; Figure 3 It is a control flow chart for dynamically adjusting the micro-pulse power based on the phase difference of the present invention.

[0021] The implementation, functional features, and advantages of the present invention will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0023] The embodiment of the present application provides a vacuum induction heating temperature closed-loop control system integrated with SCADA (Supervisory Control and Data Acquisition), including: Construct an induction coil unit, on the surface of the conductor layer of which a functional material layer is compounded. The functional material layer has a preset Curie temperature, which matches the target temperature control region of the workpiece to be heated. And the functional material layer is regulated by a cold rolling deformation process so that the temperature range where its electromagnetic impedance undergoes a significant mutation covers the phase change critical temperature range of the workpiece; A phase difference detection module that real-time collects the voltage signal and current signal generated by the induction coil during operation, and directly obtains the absolute value of the phase difference characterizing the electromagnetic characteristics of the induction coil based on the time difference between the voltage signal and the current signal , without the need for analog-to-digital conversion; A micro-pulse compensation unit. When the absolute value of the phase difference first exceeds a preset first threshold , it is determined that the temperature of the workpiece enters the phase change critical region, and immediately starts the micro-pulse power compensation mode to output micro-pulse power to the induction coil; In the micro-pulse power compensation mode, the amplitude of the micro-pulse With the change rate of the absolute value of the phase difference There is a piecewise linear relationship, and the output interval of the micro-pulse is dynamically adjusted according to the real-time change of the absolute value of the phase difference until the absolute value of the phase difference Falls back to a preset second threshold To achieve closed-loop control of the workpiece temperature.

[0024] In the micro-pulse power compensation mode, the amplitude of the micro-pulse With the change rate of the absolute value of the phase difference There is a piecewise linear relationship, and the output interval of the micro-pulse is dynamically adjusted according to the real-time change of the absolute value of the phase difference until the absolute value of the phase difference Falls back to a preset second threshold , thereby achieving closed-loop control of the workpiece temperature; among them, Greater than , Used to determine the starting point of the temperature entering the phase change critical zone, Is used to judge that the workpiece temperature has been stably controlled within the target range, thereby ending the compensation, and both belong to the extended implementation methods known to those of ordinary skill in the art; and, among them, Is the absolute value of the phase difference between voltage and current, with the unit of degree or radian; Is the operating frequency of the induction coil, with the unit of Hertz (Hz); Is the time difference between the voltage zero-crossing point and the current peak point, with the unit of second (s).

[0025] Preferably, the functional material layer is An alloy thin sheet, and by controlling its cold rolling deformation ε in the range of 10% to 18%, the Curie temperature of the functional material layer is accurately regulated to the central temperature value of the target temperature control region ±5°C, so that in the temperature range of 800°C to 1000°C, the slope of the electromagnetic impedance of the alloy thin sheet changing with temperature is greater than or equal to 5Ω / °C.

[0026] Preferably, the micro-pulse output in the micro-pulse power compensation mode is an asymmetric waveform, which is alternately composed of a high-frequency narrow pulse width pulse train and a low-frequency wide pulse width pulse train, where the frequency of the high-frequency narrow pulse width pulse train Is in the range of 8kHz to 12kHz, and the pulse width Is in the range of 8μs to 12μs, and the frequency of the low-frequency wide pulse width pulse train Is in the range of 0.8kHz to 1.2kHz, and the pulse width Is in the range of 80μs to 120μs, and satisfies the relational expression , to maintain the energy density basically constant, so as to take into account the heat compensation requirements of the workpiece while suppressing electromagnetic noise; specifically, in the micro-pulse power compensation mode, there is a piecewise linear relationship between the output power amplitude of the micro-pulse and the rate of change of the absolute value of the phase difference over time. Specifically, the system is divided into multiple intervals according to different rates of change of the phase difference. In each interval, the output power amplitude of the micro-pulse increases in a certain proportion as the rate of change of the phase difference increases, and this proportion can be set separately for different intervals. When the rate of change is small, the system uses a lower adjustment proportion; while when the rate of change is large, it switches to a higher adjustment proportion to improve the response ability. In this way, the system can automatically match an appropriate power output according to the temperature change trend to achieve a more refined and stable closed-loop control, which all belong to the extended implementation methods known to those of ordinary skill in the art.

[0027] Preferably, the absolute value of the phase difference The time difference between the voltage zero-crossing point and the peak point of the current waveform is accurately measured through a phase-locked loop circuit and obtained by calculation according to the formula where is the operating frequency of the induction coil, and the time resolution of the phase-locked loop circuit reaches the minimum time interval corresponding to 0.1°.

[0028] Preferably, when the SCADA system detects that the pressure fluctuation in the vacuum furnace cavity exceeds the preset threshold, it automatically increases the sampling frequency of the time difference from 1 kHz to 10 kHz and enables the Kalman filter to predict and correct the sequence of continuous samples. The state equation and observation equation of the Kalman filter are as follows:

[0029]

[0030] where is the predicted value of at time is the change in vacuum degree at time is the observed value of at time is the state transition matrix, is the control input matrix, is the observation matrix, and are the covariance matrices of the process noise and the observation noise respectively, represents the predicted state value of the system at the previous moment, which is used to update the state in combination with the current observed value.

[0031] Preferably, the data acquisition module of the SCADA system is reconstructed into a time series database based on the absolute value of the phase difference, and a mapping relationship table between the micro-pulse compensation power amplitude is established in advance, and the mapping relationship table is optimized through off-line simulation combined with the thermophysical parameters of different workpiece materials, and a material coefficient is introduced for different workpiece materials The calculation formula is as follows: where is the conductivity of the workpiece material, is the density of the workpiece material, and are the conductivity and density of the reference material, and are the empirical coefficients determined by multiple regression analysis of experimental data; and are the empirical coefficients, and their values are obtained by fitting analysis of experimental data through multiple regression methods, respectively reflecting the influence weights of the conductivity and density of the workpiece material on the material coefficient , and both belong to the extended implementation manners known to those of ordinary skill in the art. and is the empirical coefficient, and its value is obtained by fitting analysis of experimental data through multiple regression methods, respectively reflecting the influence weights of the conductivity and density of the workpiece material on the material coefficient , and both belong to the extended implementation manners known to those of ordinary skill in the art.

[0032] Preferably, during the process that the workpiece temperature enters and maintains in the phase change critical region, the system automatically generates a thermal hysteresis compensation curve based on the data of the historical absolute value of the phase difference , and dynamically adjusts the output of the micro-pulse power according to the compensation amount , where is a proportional factor related to the thermal diffusivity of the workpiece material, and is used to adjust the compensation amplitude to match the thermal inertia response characteristics of different materials.

[0033] Preferably, a periodically arranged micro-pit array is provided on the surface of the functional material layer, and the diameter of the micro-pit is in the range of 50 μm to 100 μm, and the depth-to-diameter ratio is in the range of 1:1 to 1:2, and is used to form a turbulent effect on the surface of the functional material layer to enhance the heat dissipation efficiency of its surface.

[0034] Preferably, the system is integrated with a self-checking module, and the self-checking module monitors the standard deviation of the fluctuation of the absolute value of the phase difference in three consecutive working cycles in real time , when When it is less than 0.5°, it is automatically determined that the phase difference detection module has an abnormality, and it switches to the redundant detection channel. At the same time, the signature code containing the fault type and occurrence time is recorded in the event log of the SCADA system for fault diagnosis and maintenance.

[0035] Preferably, the vacuum induction heating temperature closed-loop control system integrating SCADA of the present invention includes: an induction coil unit, on the surface of the conductor layer of which a functional material layer is compounded. The functional material layer has a preset Curie temperature, which matches the target temperature control region of the workpiece to be heated. And the functional material layer is regulated by a cold rolling deformation process so that the temperature range in which its electromagnetic impedance undergoes a significant mutation covers the phase change critical temperature range of the workpiece; a phase difference detection module, which collects the voltage signal and current signal generated by the induction coil during operation in real time, and based on the voltage signal and current signal, directly analyzes and obtains the absolute value of the phase difference characterizing the electromagnetic characteristics of the induction coil by comparing the time difference between the voltage zero-crossing point and the peak point of the current waveform ; a micro-pulse compensation unit, when the absolute value of the phase difference first exceeds a preset first threshold, starts the micro-pulse power compensation mode, and according to the change rate of, dynamically adjusts the amplitude and interval of the micro-pulse until falls back to a preset second threshold; an SCADA data reconstruction module, which is configured to receive and store the time series data of the absolute value of the phase difference and, based on the mapping relationship established in advance between and the micro-pulse compensation power, controls the output of the micro-pulse compensation unit, thereby realizing the closed-loop control of the workpiece temperature.

[0036] Embodiment 1: In practical applications, the control of the workpiece temperature is particularly important, especially in the phase change critical temperature region. In order to ensure high-precision control, the present invention adopts a control mechanism based on in-situ perception of electromagnetic characteristics; in a vacuum environment, a functional material layer is compounded on the surface of the conductor layer of the induction coil unit. The Curie temperature of this material layer matches the target temperature control region of the workpiece to be heated. The characteristic that the electromagnetic impedance of this material changes with temperature is used to detect whether the workpiece is approaching its phase change critical region, and then the compensation mechanism is started. Specifically, the induction coil collects the voltage signal and current signal in real time during operation, and directly analyzes and obtains the absolute value of the phase difference characterizing the electromagnetic characteristics of the induction coil by comparing the time difference between the voltage zero-crossing point and the peak point of the current waveform , when this value exceeds the preset threshold, it indicates that the temperature of the workpiece has entered the phase change critical region; at this time, the micro-pulse compensation unit starts to work, dynamically adjusts the output amplitude and interval of the micro-pulse power according to the change rate of the phase difference. The output waveform of the micro-pulse power adopts an asymmetric waveform alternating between high-frequency narrow pulse width pulses and low-frequency wide pulse width pulses, which can not only effectively suppress electromagnetic noise but also maintain the stability of heat compensation.

[0037] In addition, the SCADA data acquisition module in the system simplifies the processing of data flow by reconstructing it into a time-series database based on the absolute value of the phase difference. This module pre-establishes the mapping relationship between the phase difference and the micro-pulse power, and optimizes it according to the thermophysical parameters of different workpiece materials. For workpieces of different materials, the system adjusts according to the material coefficient (which is calculated from the conductivity and density of the material), thereby improving the adaptability and robustness of the system; during the whole process, when the SCADA system detects that the pressure fluctuation in the vacuum furnace cavity exceeds the preset threshold, the system will automatically adjust the sampling frequency and enable the Kalman filter to correct the sampled data to ensure the data accuracy and real-time performance during the control process. Through this control system, within the critical temperature region of phase change, the temperature control is accurately executed, thus avoiding the disadvantage that conventional sensors are vulnerable to electromagnetic interference and effectively reducing the hysteresis effect caused by power adjustment, ensuring the heating stability in the vacuum environment.

[0038] Example 2: In this example, the temperature state of the workpiece is indirectly sensed by real-time monitoring of the change in the electromagnetic characteristics of the induction coil. Among them, the core parameter characterizing this electromagnetic characteristic is the absolute value of the phase difference , which is calculated by the following formula: , In this formula, the absolute value of the phase difference , whose unit is usually radian (rad) or degree (°), is a key index directly reflecting the change in the comprehensive impedance of the induction coil-workpiece system. Its change trend is closely related to the changes in the electromagnetic characteristics such as magnetic permeability and resistivity of the workpiece material at a specific temperature, especially near the phase change point. The operating frequency of the induction coil, with the unit of hertz (Hz), is a stable parameter preset by the induction heating power supply or set according to the process requirements. Its value directly affects the depth and efficiency of induction heating; the time difference between the zero-crossing point of the voltage and the peak point of the current waveform, with the unit of second (s), is the original data accurately measured by real-time comparative analysis of the voltage signal and current signal of the induction coil through a phase-locked loop circuit. This time difference directly correlates the phase relationship between the voltage and the current. This formula combines the measurement results in the time domain with the known system operating frequency to convert it into a parameter that can more intuitively characterize the electromagnetic phase relationship of the system, providing basic data input for subsequent temperature state judgment and control decision-making.

[0039] Secondly, under specific working conditions, such as when the SCADA system detects that the pressure fluctuation in the vacuum furnace cavity exceeds the preset threshold, in order to improve the stability of data acquisition and the prediction accuracy, a Kalman filter is enabled to predict and correct the continuously sampled sequence. The Kalman filter includes a state equation and an observation equation, and their specific forms are as follows: State equation: , Observation equation: , In this Kalman filter model: , the predicted value at time represents the best estimate of the true time difference by the system at the -th sampling moment based on the state of the previous moment and the current input; The state transition matrix describes the inherent evolution law of the system state from the previous moment to the current moment . For example, in the absence of external interference and control input, how the value changes naturally over time; This matrix is usually determined in advance based on an understanding of the dynamic characteristics of the induction heating system or through system identification methods; is the predicted value at ( ) moment and is the recursive basis of the state equation; The control input matrix characterizes the influence degree of the external control quantity or measurable disturbance quantity on the system state; The change in vacuum degree at time k , usually in units of Pascal per second (Pa / s) or a similar pressure change rate unit, is input into the state equation as a measurable perturbation to compensate for the measurement drift that may be caused by changes in the vacuum environment; The covariance matrix of the process noise represents the uncertainty not modeled in the state transition process and the influence of the inherent random perturbation of the system itself on the evolution of the true value, and its value is usually set according to experience or statistical analysis of the system noise characteristics; The observed value at time is the original time difference data actually measured by the phase-locked loop circuit at the -th sampling moment; The observation matrix establishes the relationship between the system state quantity (i.e., the true ) and the observed value . In the present invention, since the observed value directly corresponds to the state quantity, is usually an identity matrix or an appropriate scaling factor; The covariance matrix of the observation noise represents the random error or noise introduced by the measurement process itself, such as sensor noise, signal transmission interference, etc. Its setting is also based on the understanding of the noise characteristics of the measurement system. Through the iterative operation of the above Kalman filter, the system can fuse the prediction information of the previous moment, the current control input (vacuum degree change), and the current actual observation value to generate a smoother and more accurate estimated value in real time, which is crucial for improving the robustness of the control system in a disturbed data acquisition environment, ensuring the reliability of subsequent judgment and control.

[0040] Furthermore, in order to enable the temperature closed-loop control system of the present invention to adapt to the heating requirements of workpieces made of different materials, a calculation method of a material coefficient is proposed above, and a mapping relationship table between the absolute value of the phase difference and the amplitude of the micro-pulse compensation power is established. This material coefficient is used to dynamically adjust this mapping relationship, and its calculation formula is as follows: , In this formula: The material coefficient is a dimensionless correction factor, which comprehensively reflects the differences in electromagnetic characteristics and thermophysical characteristics between the current workpiece to be heated and a certain reference material, and adjusts the control strategy accordingly. The conductivity of the workpiece material, with the unit of Siemens per meter (S / m), is a key physical parameter characterizing the conductivity of the workpiece material, and its value can be obtained by referring to relevant material manuals or through experimental measurements; the conductivity of the reference material, with the same unit of Siemens per meter (S / m), is a preset reference value corresponding to the conductivity of a standard material used or selected when establishing the basic mapping relationship; the density of the workpiece material, with the unit of kilograms per cubic meter (kg / m³), is another important physical parameter of the workpiece material, which can also be determined by referring to manuals or experimental measurements; the density of the reference material, with the same unit of kilograms per cubic meter (kg / m³), is the density value of the reference material corresponding to ; the empirical coefficients and determined by multiple regression analysis of experimental data are two dimensionless weight coefficients, which are obtained by conducting a large number of induction heating experiments on workpieces made of various materials and collecting their , as well as the known Data, and then obtained by fitting using the multiple regression analysis method in statistics. These two coefficients reflect the relative weights of the effects of conductivity and density on the heating characteristics; the material coefficient obtained through calculation , the SCADA system can preset and The basic mapping table is corrected so that the amplitude of the micro-pulse compensation power can more accurately match the current heating requirements of specific workpieces, thereby improving the generalization ability of the control system and the adaptability to different workpiece materials.

[0041] Finally, in order to cope with the possible thermal hysteresis phenomenon in the vacuum induction heating process and ensure the stable control of the workpiece temperature in the phase change critical region, the core is to calculate a thermal hysteresis compensation amount , and accordingly dynamically adjust the output of the micro-pulse power. The calculation formula for this compensation amount is: , In this formula: the thermal hysteresis compensation amount , its physical meaning can be understood as a dynamic correction signal used to adjust the power output, aiming to offset the system response delay caused by factors such as the thermal inertia of the material; the proportionality factor related to the thermal diffusivity of the workpiece material is a key parameter, and its numerical value directly affects the intensity of the compensation. The thermal diffusivity itself (usually represented by the symbol or , with the unit of square meters per second m² / s) is an inherent thermophysical property of the material, characterizing the rate of temperature homogenization inside the material. The determination of the proportionality factor usually requires calibration in combination with the thermal diffusivity of the specific workpiece material and experimental data. For example, through a series of heating experiments for specific materials, observe the temperature control hysteresis under different conditions, and establish a functional relationship with the material thermal diffusivity or directly determine a value applicable to this material; the absolute value of the phase difference has been defined in detail in the previous formula; refers to time. The expression represents the rate of change of the absolute value of the phase difference, that is how fast it changes with time, and its square emphasizes the amplitude effect of the rate of change; the entire integral term quantifies the cumulative effect of the square of the rate of change of the absolute value of the phase difference over time, reflecting the severity of the change in the system's electromagnetic characteristics over a period of time; the calculation result of this formula is used to dynamically adjust the output of the micro-pulse power (such as adjusting the amplitude or interval). The core logic is that when the change rate of the absolute value of the phase difference is large (i.e., the system state changes rapidly), the integral value of its square will increase accordingly. Through the proportionality factor regulation, a compensation signal is generated, which can be used to predictively adjust the heating power to overcome the thermal lag, so that the workpiece temperature can reach and maintain the target value more quickly and stably.

[0042] Example 3: In this embodiment, the electromagnetic characteristics of the workpiece are monitored in real time through the induction coil unit, and the heating power is adjusted according to these characteristics. The surface of the conductor layer of the induction coil unit is compounded with a functional material layer, and the Curie temperature of this functional material layer matches the target temperature control area of the workpiece. As the workpiece temperature approaches its phase change critical region, the electromagnetic impedance of the functional material changes abruptly, and the electromagnetic characteristics of the induction coil change. When the system starts, the induction coil begins to collect voltage and current signals, and by comparing the time difference between the voltage zero point and the peak point of the current waveform, the absolute value of the phase difference characterizing the electromagnetic characteristics of the induction coil is directly analyzed. This value is closely related to the temperature of the workpiece, so it becomes a key indicator for judging whether the workpiece enters the phase change critical region. When the absolute value of the phase difference exceeds the preset first threshold for the first time, the system determines that the temperature of the workpiece has entered the phase change critical region and starts the micro-pulse power compensation mode; after starting the micro-pulse compensation mode, the system will dynamically adjust the amplitude and output interval of the micro-pulse according to the change rate of the phase difference. There is a piecewise linear relationship between the micro-pulse power amplitude and the phase difference change rate, and the specific amplitude and interval are adjusted according to the real-time changing phase difference value. In this way, the system can accurately compensate for the temperature fluctuations caused by the release of latent heat of phase change.

[0043] The reconstructed data acquisition module of the SCADA system uses a time series database based on the absolute value of the phase difference, which simplifies the originally complex multi-sensor signal fusion process. In this system, the SCADA system pre-establishes and stores the absolute value of the phase difference and the mapping relationship table between the micro-pulse compensation power amplitude This table is calibrated and optimized based on offline simulation analysis and experimental data, and combined with the thermophysical parameters of different workpiece materials; further, for a specific workpiece material, the system calculates its material coefficient (its calculation formula is , where and are the conductivity and density of the workpiece material respectively, and are the corresponding parameters of the reference material, and (which is an empirical coefficient determined by multivariate regression analysis of experimental data), dynamically correct this preset mapping relation table to ensure that the amplitude of the micro-pulse compensation power for this material can be accurately output, so as to adapt to the heating requirements of specific workpieces; in the processing of workpieces of different materials, the system calculates the material coefficient according to the conductivity and density parameters of the material, and this coefficient reflects the difference in thermophysical properties between the workpiece material and the reference material, and optimizes the control strategy by adjusting the output amplitude of the micro-pulse compensation power. For example, for high-conductivity materials, the system, through real-time monitoring of the electromagnetic characteristics of the induction coil, accurately captures the electromagnetic impedance mutation signal. At this time, the SCADA system receives the real-time data from the phase difference detection module and starts the micro-pulse compensation mode according to the preset control logic, and outputs the accurately adjusted micro-pulse power to the induction coil. The system adjusts the power output according to the phase difference change rate to ensure that the workpiece temperature is maintained within the preset range. As the workpiece temperature changes, the system dynamically adjusts the power output to avoid interference of temperature fluctuations on the phase change process. All of these belong to the extended implementation methods known to those of ordinary skill in the art.

[0044] Example 4: The application scenario of this example is the temperature control process of the high-precision alloy directional solidification process in a vacuum environment. In this process, the workpiece temperature needs to be accurately controlled in the region close to its phase change critical temperature, which requires the system to be able to sense the temperature change of the workpiece in real time and make dynamic adjustments; however, the electromagnetic interference and thermal radiation in the vacuum environment pose great challenges to the accuracy of the temperature sensor. Therefore, a solution that does not rely on traditional temperature sensors but uses electromagnetic characteristics to achieve temperature sensing is needed.

[0045] In the practical application of this process, a functional material layer with a specific Curie temperature is first compounded on the surface of the conductor of the induction coil unit. This functional material layer is regulated through a cold rolling deformation process to ensure that its electromagnetic impedance undergoes a significant mutation near the critical temperature of the workpiece phase transformation. This mutated electromagnetic characteristic enables the induction coil to capture in real time the change in the phase difference caused by the change in electromagnetic characteristics when the temperature is close to the critical region of the workpiece phase transformation. By monitoring this phase difference, the system can accurately determine whether the workpiece is approaching the critical phase transformation region. In specific operations, the induction coil collects voltage signals and current signals during the working process in real time, and precisely measures the time difference between the zero-crossing point of the voltage and the peak point of the current waveform through a phase-locked loop circuit. Based on this time difference, the system can calculate the absolute value of the phase difference corresponding to the change in electromagnetic characteristics and use this value as a key parameter for temperature control. Specifically, when the absolute value of the phase difference first exceeds a preset threshold, the system determines that the workpiece temperature has approached its critical phase transformation region. At this time, the micro-pulse power compensation mode will be activated. Once the micro-pulse compensation mode is started, the system will dynamically adjust the amplitude and output interval of the micro-pulse according to the phase difference change rate. Specifically, the amplitude of the micro-pulse power has a piecewise linear relationship with the phase difference change rate and is adjusted according to the real-time changing phase difference. To better cope with electromagnetic noise in a vacuum environment, the system adopts an asymmetric waveform design, combining the alternating output of high-frequency narrow pulse-width pulses and low-frequency wide pulse-width pulses, so as to suppress electromagnetic interference while compensating for heat and maintaining the stability and accuracy of the system.

[0046] To ensure the stability and accuracy of the system under complex working conditions, the SCADA system reconstructs the data acquisition module in this embodiment and changes it to a time series database based on the absolute value of the phase difference. This time series database is not only used to store historical data of the phase difference, but also optimized according to the thermophysical parameters of the workpiece material. By establishing a mapping relationship between the phase difference and the amplitude of the micro-pulse power, the system can automatically adjust the control strategy during the processing of workpieces with different materials. For example, for materials with higher conductivity, the system increases the amplitude of the micro-pulse power and optimizes the output interval to improve the heating efficiency; for materials with lower conductivity, the system reduces the power output to avoid overheating. In the critical phase transformation region, the control of the workpiece temperature faces a large hysteresis effect, especially the thermal diffusion characteristics of the material have a greater impact on the temperature response. Therefore, in this embodiment, a thermal hysteresis compensation curve is generated based on the historical absolute value data of the phase difference, and the output of the micro-pulse power is adjusted according to this curve. Specifically, the thermal hysteresis compensation amount is calculated by integrating the square of the phase difference change rate and dynamically adjusts the compensation intensity in combination with the thermal diffusion coefficient of the workpiece. The introduction of this mechanism effectively avoids temperature fluctuations caused by the thermal inertia of the material and ensures the temperature stability in the critical phase transformation region, which all belong to the extended implementation methods known to those of ordinary skill in the art.

[0047] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. An integrated SCADA vacuum induction heating temperature closed-loop control system, characterized in that, Including: Constructing an induction coil unit, on the surface of the conductor layer of which a functional material layer is compounded. The functional material layer has a preset Curie temperature, which matches the target temperature control region of the workpiece to be heated. And the functional material layer is regulated by a cold rolling deformation process so that the temperature range in which its electromagnetic impedance undergoes a significant mutation covers the phase change critical temperature range of the workpiece; The phase difference detection module collects the voltage signal and current signal generated by the induction coil during operation in real time, and directly obtains the absolute value of the phase difference characterizing the electromagnetic characteristics of the induction coil based on the time difference between the voltage signal and the current signal, without the need for analog-to-digital conversion; , without the need for analog-to-digital conversion; The micro-pulse compensation unit, when the absolute value of the phase difference first exceeds a preset first threshold it is determined that the temperature of the workpiece enters the phase transition critical region, and immediately starts the micro-pulse power compensation mode, outputting micro-pulse power to the induction coil; In the micro-pulse power compensation mode, the amplitude of the micro-pulse and the change rate of the absolute value of the phase difference show a piecewise linear relationship. Moreover, the output interval of the micro-pulse is dynamically adjusted according to the real-time change of the absolute value of the phase difference until the absolute value of the phase difference falls back to a preset second threshold to achieve closed-loop control of the workpiece temperature.

2. An integrated SCADA vacuum induction heating temperature closed-loop control system according to claim 1, characterized in that The micro-pulses output under the micro-pulse power compensation mode are asymmetric waveforms, which are alternately composed of high-frequency narrow pulse-width pulse trains and low-frequency wide pulse-width pulse trains. The frequency of the high-frequency narrow pulse-width pulse trains is in the range of 8 kHz to 12 kHz, and the pulse width is in the range of 8 μs to 12 μs. The frequency of the low-frequency wide pulse-width pulse trains is in the range of 0.8 kHz to 1.2 kHz, and the pulse width is in the range of 80 μs to 120 μs, and satisfies the relational expression .

3. An integrated SCADA vacuum induction heating temperature closed-loop control system according to claim 2, characterized in that, Absolute value of phase difference The time difference between the zero-crossing point of voltage and the peak point of current waveform is accurately measured through a phase-locked loop circuit and obtained according to the formula where is the operating frequency of the induction coil 4. An integrated SCADA vacuum induction heating temperature closed-loop control system according to claim 3, characterized in that, When the SCADA system detects that the pressure fluctuation in the vacuum furnace chamber exceeds the preset threshold, it automatically sets the time difference sampling frequency from 1 kHz to 10 kHz and enables the Kalman filter to predict and correct the continuously sampled sequence. The state equation and observation equation of the Kalman filter are as follows: ， ， Among them, is the predicted value at time , is the change in vacuum degree at time is the observed value at time , is the state transition matrix, is the control input matrix, is the observation matrix, and are the covariance matrices of process noise and observation noise respectively.

5. An integrated SCADA vacuum induction heating temperature closed-loop control system according to claim 1, characterized in that, The data acquisition module of the SCADA system is reconstructed into a time series database based on the absolute value of the phase difference and a mapping relationship table between the micro-pulse compensation power amplitude is pre-established. The mapping relationship table is optimized through offline simulation combined with the thermophysical parameters of different workpiece materials, and a material coefficient is introduced for different workpiece materials. Its calculation formula is as follows: ， wherein, is the conductivity of the workpiece material, is the density of the workpiece material, and are the conductivity and density of the reference material, and are empirical coefficients determined by multiple regression analysis of experimental data.

6. An integrated SCADA vacuum induction heating temperature closed-loop control system according to claim 1, characterized in that, During the process that the workpiece temperature enters and maintains in the phase transition critical region, the system automatically generates a thermal hysteresis compensation curve based on the data of the absolute value of the historical phase difference, and dynamically adjusts the output of the micro-pulse power according to the compensation amount, where is a proportionality factor related to the thermal diffusivity of the workpiece material. ​​ 7. An integrated SCADA vacuum induction heating temperature closed-loop control system according to claim 1, characterized in that The surface of the functional material layer is provided with a periodically arranged micro-pit array, and the diameter of the micro-pits is in the range of 50 μm to 100 μm, and the depth-to-diameter ratio is in the range of 1:1 to 1:

2.

8. An integrated SCADA vacuum induction heating temperature closed-loop control system according to claim 7, characterized in that, The system is integrated with a self-check module that monitors in real time the absolute value of the phase difference within three consecutive working cycles for the standard deviation of fluctuations . When is less than 0.5°, it automatically determines that the phase difference detection module has an abnormality, switches to the redundant detection channel, and records the signature containing the fault type and occurrence time in the event log of the SCADA system.

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