A vacuum induction heating temperature closed-loop control system integrated with SCADA

Abstract

The present 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, comprising: compounding a functional material layer having a preset Curie temperature on the surface of an induction coil, analyzing the absolute value of the phase difference by real-time acquisition of the coil voltage and current signals, and activating a micropulse power compensation mode and dynamically adjusting the output parameters when the phase difference exceeds a threshold. The present invention achieves non-contact precise control of the critical temperature of the phase change of a workpiece through the synergistic effect of the electromagnetic impedance mutation characteristics of the functional material layer and the phase difference detection mechanism. At the same time, the coupled application of asymmetric micropulse waveform design and dynamic adjustment strategy effectively balances the contradiction between thermodynamic response and electromagnetic interference in a vacuum environment, significantly improving the control accuracy and stability of the system.

Description

Technical Field

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

[0002] In the field of vacuum induction heating temperature control, existing technologies generally adopt a solution that combines multi-sensor feedback with dynamic adjustment. By deploying a temperature sensor array in the vacuum chamber and relying on high-frequency data acquisition to achieve closed-loop control, this method can maintain basic temperature control accuracy under conventional working conditions. However, its inherent limitations gradually become apparent in high-precision heat treatment processes involving the critical temperature of phase change.

[0003] Specifically, sensors are susceptible to electromagnetic interference and thermal radiation in a vacuum environment, and it is difficult to balance the real-time and reliability of signal acquisition. Although the redundant configuration of sensors is intended to improve fault tolerance, it exacerbates the complexity of signal conflicts and compensation algorithms, resulting in system response delays and decreased stability. In addition, traditional dynamic adjustment strategies regard temperature fluctuations as noise and forcibly suppress them, ignoring the nonlinear self-organization characteristics of latent heat release of material phase change and electromagnetic eddy current distribution during vacuum heating. Excessive intervention can easily destroy the inherent thermal balance of the system and induce unpredictable hysteresis oscillation phenomena. For example, in the directional solidification process of high-temperature alloys, frequent power adjustments not only aggravate the turbulence of the molten pool, but also significantly increase the temperature gradient control inaccuracy rate in the key phase change zone.

[0004] Based on this, the industry has attempted to alleviate these issues by optimizing sensor layout or introducing advanced filtering algorithms. However, these improvements have mostly focused on signal processing and failed to address the fundamental contradiction between temperature sensing mechanisms and dynamic control logic in a vacuum environment. Therefore, how to construct a vacuum heating temperature closed-loop control mechanism based on in-situ electromagnetic characteristic sensing and adaptive power compensation, while avoiding reliance on physical sensors, to achieve high-precision steady-state control of the phase transition critical region, has become a core technical challenge 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, which mainly aims to solve the problems of insufficient reliability of traditional multi-sensor feedback mechanism in vacuum environment, mismatch between dynamic adjustment strategy and nonlinear characteristics of material phase change, resulting in reduced temperature control accuracy and impaired system stability.

[0006] To achieve the above object, the present invention provides a vacuum induction heating temperature closed-loop control system integrated with SCADA, comprising:

[0007] An induction coil unit is constructed, wherein the surface of the conductor layer of the induction coil unit is composited with a functional material layer. The functional material layer has a preset Curie temperature that matches the target temperature control range of the workpiece to be heated. The functional material layer is regulated through a cold rolling deformation process so that the temperature range where its electromagnetic impedance undergoes a significant mutation covers the critical phase change temperature range of the workpiece.

[0008] The phase difference detection module collects the voltage and current signals generated by the induction coil in real time during operation, and directly obtains the absolute value of the phase difference that characterizes the electromagnetic characteristics of the induction coil based on the time difference between the voltage and current signals. , no analog-to-digital conversion is required;

[0009] Micropulse compensation unit, when the absolute value of the phase difference Exceeds the preset first threshold for the first time When the temperature of the workpiece enters the critical phase change region, the micro-pulse power compensation mode is immediately activated to output micro-pulse power to the induction coil;

[0010] In the micropulse power compensation mode, the amplitude of the micropulse The rate of change of the absolute value of the phase difference There is a piecewise linear relationship between them, 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 is Falling back to the preset second threshold To achieve closed-loop control of the workpiece temperature.

[0011] In the micropulse power compensation mode, the amplitude of the micropulse The rate of change of the absolute value of the phase difference There is a piecewise linear relationship between them, 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 is Falling back to the preset second threshold , thereby achieving closed-loop control of the workpiece temperature.

[0012] Preferably, the micropulse output in the micropulse power compensation mode is an asymmetric waveform, which is composed of a high-frequency narrow pulse width pulse train and a low-frequency pulse width pulse train alternating. In the range of 8kHz to 12kHz, the pulse width The frequency of the low-width pulse train is in the range of 8μs to 12μs. In the range of 0.8kHz to 1.2kHz, the pulse width In the range of 80μs to 120μs, and satisfying the relationship , in order to maintain the energy density basically constant, thereby suppressing electromagnetic noise while taking into account the heat compensation needs of the workpiece.

[0013] Preferably, the absolute value of the phase difference The time difference between the voltage zero crossing point and the current waveform peak point is realized by the phase-locked loop circuit The precise measurement of Calculated, 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°.

[0014] Preferably, when the SCADA system detects that the pressure fluctuation in the vacuum furnace chamber exceeds a preset threshold, the time difference is automatically The sampling frequency is increased from 1kHz to 10kHz, and the Kalman filter is enabled for continuous sampling. The sequence is predicted and corrected, and the state equation and observation equation of the Kalman filter are as follows:

[0015]

[0016]

[0017] in, for Moment Predicted value, for The change in vacuum degree at time, for Moment Observed values, 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.

[0018] Preferably, the data acquisition module of the SCADA system is reconstructed based on the absolute value of the phase difference Time series database, and pre-established Compensation power amplitude with micro-pulse The mapping relationship table between them is optimized by offline simulation combined with the thermophysical parameters of different workpiece materials, in which material coefficients are introduced for different workpiece materials. , and its calculation formula is:

[0019] ,

[0020] in, is the electrical 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.

[0021] Preferably, when the workpiece temperature enters the critical phase change region and remains in this region, the system calculates the absolute value of the historical phase difference. The thermal hysteresis compensation curve is automatically generated according to the compensation amount. The output of micro-pulse power is dynamically adjusted, where is a proportionality factor related to the thermal diffusivity of the workpiece material.

[0022] Preferably, the surface of the functional material layer is provided with a periodically arranged array of micro-pits, the diameter of the micro-pits being In the range of 50μm to 100μm, the aspect 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.

[0023] Preferably, the system is integrated with a self-checking module, which monitors the absolute value of the phase difference within three consecutive working cycles in real time. The standard deviation of volatility ,when When the phase difference is less than 0.5°, the phase difference detection module is automatically determined to be abnormal and switches to the redundant detection channel. At the same time, the characteristic code containing the fault type and occurrence time is recorded in the event log of the SCADA system for fault diagnosis and maintenance.

[0024] Compared with the background technology problems, the beneficial effects of the present invention are:

[0025] 1. In the complex scenario of high-frequency electromagnetic interference and thermal radiation disturbance in a vacuum environment, the system can bypass the physical limitations of traditional temperature sensors through the synergistic effect of the Curie temperature characteristics of the functional material layer and the phase difference detection mechanism. It can 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 critical region of phase change, the electromagnetic impedance mutation characteristics of the functional material layer and the high-precision time difference detection of the phase-locked loop circuit form a two-way confirmation, triggering the precise intervention of the micro-pulse compensation mechanism, thereby achieving autonomous balance control of the material phase change latent heat release process without the need for real-time temperature numerical feedback.

[0026] 2. To address the industry challenge of the mismatch between nonlinear thermodynamic response and conventional power regulation during vacuum heating, the coupled application of asymmetric micro-pulse waveform design and 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-width pulses and low-frequency wide-width pulses, through the reorganization of spectral characteristics under the constraint of constant energy density, suppresses the electromagnetic harmonic resonance caused by traditional continuous power regulation, and ensures the time domain matching between the thermal inertia of the phase change zone and the pulse energy input, forming a thermo-electric dynamic balance system with self-stabilizing characteristics.

[0027] 3. By reconstructing the data acquisition logic and processing paradigm of the SCADA system, the traditional complex data stream based on multi-sensor signal fusion is simplified into a single-dimensional analysis of phase difference timing characteristics. This mechanism utilizes the temperature-electromagnetic impedance conversion characteristics of the functional material layer to encode thermodynamic state information into an electromagnetic phase signal that can be directly processed, thereby realizing the physical layer fusion of control parameters at the data acquisition source, greatly reducing the system's dependence on back-end data processing algorithms, and significantly improving the robustness and real-time response capabilities of the control system in a vacuum environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a timing diagram of data interaction between the phase difference detection and self-test modules of the integrated SCADA system of the present invention;

[0029] Figure 2 This is a working diagram of the induction coil unit and the phase difference detection module in a vacuum environment of the present invention;

[0030] Figure 3 This is a control flow chart for dynamically adjusting micro-pulse power based on phase difference in the present invention.

[0031] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0032] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0033] The present invention provides a vacuum induction heating temperature closed-loop control system integrated with a SCADA (Supervisory Control and Data Acquisition) system, comprising:

[0034] An induction coil unit is constructed, wherein the surface of the conductor layer of the induction coil unit is composited with a functional material layer. The functional material layer has a preset Curie temperature that matches the target temperature control range of the workpiece to be heated. The functional material layer is regulated through a cold rolling deformation process so that the temperature range where its electromagnetic impedance undergoes a significant mutation covers the critical phase change temperature range of the workpiece.

[0035] The phase difference detection module collects the voltage and current signals generated by the induction coil in real time during operation, and directly obtains the absolute value of the phase difference that characterizes the electromagnetic characteristics of the induction coil based on the time difference between the voltage and current signals. , no analog-to-digital conversion is required;

[0036] Micropulse compensation unit, when the absolute value of the phase difference Exceeds the preset first threshold for the first time When the temperature of the workpiece enters the critical phase change region, the micro-pulse power compensation mode is immediately activated to output micro-pulse power to the induction coil;

[0037] In the micropulse power compensation mode, the amplitude of the micropulse The rate of change of the absolute value of the phase difference There is a piecewise linear relationship between them, 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 is Falling back to the preset second threshold To achieve closed-loop control of the workpiece temperature.

[0038] In the micropulse power compensation mode, the amplitude of the micropulse The rate of change of the absolute value of the phase difference There is a piecewise linear relationship between them, 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 is Falling back to the preset second threshold , thereby realizing closed-loop control of the workpiece temperature; wherein, Greater than , Used to determine the starting point of the temperature entering the critical region of phase change, It is used to determine that the workpiece temperature has been stably controlled within the target range, thereby ending the compensation, which belongs to an extended implementation method known to those skilled in the art; and, wherein, is the absolute value of the phase difference between voltage and current, in degrees or radians; is the operating frequency of the induction coil, in Hertz (Hz); It is the time difference between the voltage zero crossing point and the current peak point, in seconds (s).

[0039] Preferably, the functional material layer is alloy sheet, and by controlling its cold rolling deformation ε within the range of 10% to 18%, the Curie temperature of the functional material layer is precisely controlled to the center temperature value of the target temperature control area within ±5°C, so that in the temperature range of 800°C to 1000°C, the slope of the electromagnetic impedance of the alloy sheet changing with temperature is greater than or equal to 5Ω / °C.

[0040] Preferably, the micropulse output in the micropulse power compensation mode is an asymmetric waveform, which is composed of a high-frequency narrow pulse width pulse train and a low-frequency pulse width pulse train alternating. In the range of 8kHz to 12kHz, the pulse width The frequency of the low-width pulse train is in the range of 8μs to 12μs. In the range of 0.8kHz to 1.2kHz, the pulse width In the range of 80μs to 120μs, and satisfying the relationship , to maintain a substantially constant energy density, thereby suppressing electromagnetic noise while also taking into account the workpiece's thermal compensation needs. Specifically, in the micropulse power compensation mode, there is a piecewise linear relationship between the output power amplitude of the micropulse and the speed at which the absolute value of the phase difference changes over time. Specifically, the system is divided into multiple intervals based on the phase difference change rate. Within each interval, the output power amplitude of the micropulse increases at a certain ratio as the phase difference change rate increases, and this ratio can be set separately for different intervals. When the change rate is low, the system uses a lower adjustment ratio; when the change rate is high, it switches to a higher adjustment ratio to improve responsiveness. In this way, the system can automatically match the appropriate power output according to the temperature change trend, achieving more precise and stable closed-loop control. These are all extended implementation methods known to those skilled in the art.

[0041] Preferably, the absolute value of the phase difference The time difference between the voltage zero crossing point and the current waveform peak point is realized by the phase-locked loop circuit The precise measurement of Calculated, 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°.

[0042] Preferably, when the SCADA system detects that the pressure fluctuation in the vacuum furnace chamber exceeds a preset threshold, the time difference is automatically The sampling frequency is increased from 1kHz to 10kHz, and the Kalman filter is enabled for continuous sampling. The sequence is predicted and corrected, and the state equation and observation equation of the Kalman filter are as follows:

[0043]

[0044]

[0045] in, for Moment Predicted value, for The change in vacuum degree at time, for Moment Observed values, 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, Represents the predicted state value of the system at the previous moment, which is used to update the state in combination with the current observation value.

[0046] Preferably, the data acquisition module of the SCADA system is reconstructed based on the absolute value of the phase difference Time series database, and pre-established Compensation power amplitude with micro-pulse The mapping relationship table between them is optimized by offline simulation combined with the thermophysical parameters of different workpiece materials, in which material coefficients are introduced for different workpiece materials. , and its calculation formula is:

[0047] ,

[0048] in, is the electrical 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; and is the empirical coefficient, and its value is obtained by fitting and analyzing the experimental data using the multiple regression method, which reflects the effect of the conductivity and density of the workpiece material on the material coefficient. The influence weights are all extended implementation methods known to those skilled in the art.

[0049] Preferably, when the workpiece temperature enters the critical phase change region and remains in this region, the system calculates the absolute value of the historical phase difference. The thermal hysteresis compensation curve is automatically generated according to the compensation amount. The output of micro-pulse power is dynamically adjusted, 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.

[0050] Preferably, the surface of the functional material layer is provided with a periodically arranged array of micro-pits, the diameter of the micro-pits being In the range of 50μm to 100μm, the aspect 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.

[0051] Preferably, the system is integrated with a self-checking module, which monitors the absolute value of the phase difference within three consecutive working cycles in real time. The standard deviation of volatility ,when When the phase difference is less than 0.5°, the phase difference detection module is automatically determined to be abnormal and switches to the redundant detection channel. At the same time, the characteristic code containing the fault type and occurrence time is recorded in the event log of the SCADA system for fault diagnosis and maintenance.

[0052] Preferably, the vacuum induction heating temperature closed-loop control system integrated with SCADA of the present invention comprises: an induction coil unit, a functional material layer is composited on the surface of its conductor layer, the functional material layer has a preset Curie temperature, the Curie temperature matches the target temperature control area 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 directly analyzes and obtains the absolute value of the phase difference that characterizes the electromagnetic characteristics of the induction coil by comparing the time difference between the voltage zero crossing point and the current waveform peak point based on the voltage signal and the current signal. ; Micropulse compensation unit, when the absolute value of the phase difference When the preset first threshold is exceeded for the first time, the micro-pulse power compensation mode is started and the power is adjusted according to the The amplitude and interval of the micro pulses are dynamically adjusted by the rate of change until Falling back to a preset second threshold; the SCADA data reconstruction module is configured to receive and store the absolute value of the phase difference Time series data, and based on pre-established The mapping relationship between the micropulse compensation power and the output of the micropulse compensation unit is controlled to achieve closed-loop control of the workpiece temperature.

[0053] Example 1: In practical applications, the control of workpiece temperature is particularly important, especially in the critical temperature region of phase change. In order to ensure high-precision control, the present invention adopts a control mechanism based on in-situ sensing of electromagnetic characteristics; in a vacuum environment, the surface of the conductor layer of the induction coil unit is composited with a functional material layer, and the Curie temperature of the material layer matches the target temperature control region of the workpiece to be heated. The characteristic of the electromagnetic impedance of the material changing with temperature is used to detect whether the workpiece is close to its critical region of phase change, and then start the compensation mechanism. Specifically, the induction coil collects voltage signals and current signals in real time during operation, and directly analyzes and obtains the absolute value of the phase difference that characterizes the electromagnetic characteristics of the induction coil by comparing the time difference between the voltage zero crossing point and the current waveform peak point. When this value exceeds the preset threshold, it indicates that the temperature of the workpiece has entered the critical zone of phase change; at this time, the micropulse compensation unit starts working and dynamically adjusts the output amplitude and interval of the micropulse power according to the rate of change of the phase difference. The output waveform of the micropulse power adopts an asymmetric waveform that alternates high-frequency narrow-width pulses with low-frequency wide-width pulses. This can effectively suppress electromagnetic noise and maintain the stability of thermal compensation.

[0054] In addition, the SCADA data acquisition module in the system simplifies the processing of data streams by reconstructing it into a time series database based on the absolute value of the phase difference. The 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 optimizes the phase difference according to the material coefficient. The system's adaptability and robustness are enhanced by adjusting the coefficient (calculated from the material's conductivity and density). Throughout the process, when the SCADA system detects pressure fluctuations within the vacuum furnace chamber exceeding a preset threshold, it automatically adjusts the sampling frequency and activates a Kalman filter to correct the sampled data, ensuring data accuracy and real-time performance during control. This control system ensures precise temperature control within the critical phase transition temperature range, avoiding the vulnerability of conventional sensors to electromagnetic interference and effectively reducing the hysteresis caused by power adjustments, ensuring heating stability in a vacuum environment.

[0055] Example 2: In this example, the temperature state of the workpiece is indirectly sensed by monitoring the changes in the electromagnetic characteristics of the induction coil in real time. The core parameter characterizing the electromagnetic characteristics is the absolute value of the phase difference. , calculated using the following formula:

[0056] ,

[0057] In this formula, the absolute value of the phase difference , whose unit is usually radian (rad) or degree (°), is a key indicator that directly reflects the change of the comprehensive impedance of the induction coil-workpiece system. Its change trend is closely related to the change of the electromagnetic properties of the workpiece material at a specific temperature, especially near the phase transition point, such as magnetic permeability and resistivity. The working frequency of the induction coil , in Hertz (Hz), is a stable parameter preset by the induction heating power supply or set according to process requirements. Its value directly affects the depth and efficiency of induction heating; the time difference between the voltage zero point and the current waveform peak point , in seconds (s), is the raw data obtained by accurately measuring the voltage and current signals of the induction coil through real-time comparative analysis of the phase-locked loop circuit. The time difference is directly related to the phase relationship between the voltage and current. This formula converts the measurement results in the time domain into With the known system operating frequency Combined with the above, it is converted into a parameter that can more intuitively represent the electromagnetic phase relationship of the system , providing basic data input for subsequent temperature status judgment and control decisions.

[0058] Secondly, under certain working conditions, for example, when the SCADA system detects that the pressure fluctuation in the vacuum furnace chamber exceeds the preset threshold, in order to improve the time difference The stability and prediction accuracy of data acquisition are improved by using Kalman filter to The Kalman filter contains the state equation and observation equation, which are as follows: State equation: , observation equation: , in this Kalman filter model: Moment Predicted value Representatives in the At a sampling moment, the system calculates the real time difference based on the state of the previous moment and the current input. The best estimate of the state transition matrix Describes the system state from the previous moment To the current moment For example, in the absence of external interference and control input, How the values ​​naturally change over time; this matrix is ​​usually predetermined based on an understanding of the dynamic characteristics of the induction heating system or through system identification methods; That is ( ) at the moment The predicted value is the recursive basis of the state equation; the control input matrix It represents the influence of external control quantity or measurable disturbance quantity on the system state; the change of vacuum degree at time k , the unit is usually Pascal per second (Pa / s) or similar pressure change rate unit, which is input into the state equation as a measurable disturbance to compensate for the possible changes caused by the vacuum environment. Measurement drift; covariance matrix of process noise It represents the uncertainty in the state transition process that is not modeled and the random disturbance inherent in the system itself. The impact of the evolution of the true value, whose value is usually set based on experience or statistical analysis of the system noise characteristics; Moment Observations The phase-locked loop circuit The original time difference actually measured at the sampling moment Data; observation matrix Established the system state quantity (that is, the real ) and the observed value In the present invention, since the observed value directly corresponds to the state quantity, Typically the 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 integrate the prediction information of the previous moment, the current control input (vacuum degree change) and the current actual observation value to generate a real-time response. Smoother and more accurate estimates are crucial for improving the robustness of control systems in disturbed data acquisition environments, ensuring that subsequent Reliability of judgment and control.

[0059] Furthermore, in order to make the temperature closed-loop control system of the present invention adapt to the heating requirements of workpieces of different materials, a material coefficient is proposed above. The calculation method of the phase difference absolute value was established Compensation power amplitude with micro-pulse The mapping relationship table between the material coefficient It is used to dynamically adjust the mapping relationship. The calculation formula is as follows:

[0060] ,

[0061] In this formula: Material coefficient It is a dimensionless correction factor that comprehensively reflects the difference in electromagnetic and thermophysical properties of the workpiece to be heated relative to a certain reference material, and adjusts the control strategy accordingly. , the unit is Siemens per meter (S / m), which is a key physical parameter that characterizes the electrical conductivity of the workpiece material. Its value can be obtained by referring to the relevant material manual or through experimental measurement; the conductivity of the reference material , the unit is also Siemens per meter (S / m), which 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 , in kilograms per cubic meter (kg / m³), is another important physical parameter of the workpiece material, which can also be determined by consulting a manual or experimental measurement; the density of the reference material , the unit is also kilograms per cubic meter (kg / m³), which is the same as Density value of the corresponding reference material; empirical coefficients determined by multiple regression analysis of experimental data and are two dimensionless weight coefficients, which are obtained by conducting a large number of induction heating experiments on workpieces of various materials and collecting their 、 and known The data is then fitted using the multiple regression analysis method in statistics. These two coefficients reflect the relative weights of the effects of conductivity and density on heating characteristics. The material coefficient obtained by calculation , the SCADA system can and The basic mapping table is modified so that the amplitude of the micropulse compensation power can more accurately match the heating requirements of the current specific workpiece, thereby improving the generalization ability of the control system and its adaptability to different workpiece materials.

[0062] Finally, in order to deal with the thermal hysteresis phenomenon that may occur during vacuum induction heating and ensure the stable control of the workpiece temperature in the critical region of phase change, the core is to calculate a thermal hysteresis compensation amount , and accordingly the output of the micro-pulse power is dynamically adjusted. The calculation formula of the compensation amount is:

[0063] ,

[0064] In this formula: Thermal hysteresis compensation amount Its physical meaning can be understood as a dynamic correction signal for adjusting power output, which is intended to offset the system response delay caused by factors such as material thermal inertia; the proportional factor related to the thermal diffusivity of the workpiece material It is a key parameter, and its value directly affects the strength of compensation. The thermal diffusion coefficient itself (usually expressed as or The unit is square meters per second (m² / s), which is the inherent thermophysical property of the material and characterizes the rate at which the temperature inside the material is homogenized. The proportionality factor The determination of the thermal diffusivity of the workpiece material usually requires calibration based on the thermal diffusivity of the workpiece material and experimental data. For example, a series of heating experiments on specific materials can be conducted to observe the thermal diffusivity of the workpiece material under different conditions. Temperature control hysteresis under certain conditions, and establish it through optimization algorithm or empirical formula The functional relationship between the thermal diffusivity of the material or directly determine a suitable value; absolute value of phase difference It has been defined in detail in the preceding formula; Refers to time. Expression represents the rate of change of the absolute value of the phase difference, that is, The square of the speed of change over time The amplitude effect of the rate of change is emphasized; the entire integral term It quantifies the cumulative effect of the square of the absolute value change rate of the phase difference over time, reflecting the severity of the change in the electromagnetic characteristics of the system over a period of time; the calculation result of this formula is It is used to dynamically adjust the output of micro-pulse power (for example, adjusting the amplitude or interval). Its core logic is that when the rate of change of the absolute value of the phase difference is large (that is, the system state changes rapidly), the integral value of its square will increase accordingly, and the proportional factor The compensation signal is generated by the regulation, which can be used to predictively adjust the heating power to overcome thermal lag, so that the workpiece temperature can reach and maintain the target value more quickly and smoothly.

[0065] Example 3: In this embodiment, the electromagnetic properties of the workpiece are monitored in real time by an induction coil unit, and the heating power is adjusted according to these properties. The surface of the conductor layer of the induction coil unit is composited with a functional material layer, and the Curie temperature of the functional material layer matches the target temperature control area of ​​the workpiece. As the temperature of the workpiece approaches its phase change critical zone, the electromagnetic impedance of the functional material suddenly changes, and the electromagnetic properties 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 current waveform peak point, it directly analyzes and obtains the absolute value of the phase difference that characterizes the electromagnetic characteristics of the induction coil. This value is closely related to the temperature of the workpiece, so it becomes a key indicator for judging whether the workpiece has entered the critical zone of phase change. 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 critical zone of phase change and starts the micropulse power compensation mode; after starting the micropulse compensation mode, the system will dynamically adjust the amplitude and output interval of the micropulse according to the rate of change of the phase difference. The micropulse power amplitude and the phase difference change rate show a piecewise linear relationship. 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.

[0066] The reconstructed data acquisition module of the SCADA system adopts a time series database based on the absolute value of 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 phase difference. Compensation power amplitude with micro-pulse The mapping relationship table between them is based on offline simulation analysis and experimental data, and is calibrated and optimized in combination with the thermophysical parameters of different workpiece materials; furthermore, the system calculates the material coefficient for a specific workpiece material. (The calculation formula is ,in and are the electrical conductivity and density of the workpiece material, and are the corresponding parameters of the reference material, and (The empirical coefficients are determined through multivariate regression analysis of experimental data) and this preset mapping relationship table is dynamically modified to ensure that the amplitude of the micropulse compensation power for the material can be accurately output, thereby adapting to the heating requirements of the specific workpiece. When processing workpieces of different materials, the system calculates the material coefficient based on the material's conductivity and density parameters. 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 micropulse compensation power. For example, for highly conductive materials, the system accurately captures the electromagnetic impedance mutation signal through real-time monitoring of the electromagnetic characteristics of the induction coil. At this time, the SCADA system receives real-time data from the phase difference detection module and activates the micropulse compensation mode according to the preset control logic, outputting precisely adjusted micropulse 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 temperature fluctuations interfering with the phase change process. These are all extended implementation methods known to ordinary technicians in this field.

[0067] Example 4: The application scenario of this example is the temperature control process of a high-precision alloy directional solidification process in a vacuum environment. In this process, the temperature of the workpiece needs to be precisely controlled in a region close to its critical temperature of phase change, which requires the system to be able to sense the temperature changes of the workpiece in real time and make dynamic adjustments; however, electromagnetic interference and thermal radiation in a vacuum environment pose a great challenge to the accuracy of the temperature sensor. Therefore, a solution that does not rely on traditional temperature sensors but uses electromagnetic properties to achieve temperature perception is needed.

[0068] In the practical application of this process, a functional material layer with a specific Curie temperature is first composited onto the conductor surface of the induction coil unit. This functional material layer is regulated through a cold rolling process to ensure that its electromagnetic impedance undergoes a significant mutation near the critical temperature of the workpiece phase transition. This mutation in electromagnetic properties enables the induction coil to capture the phase difference caused by the change in electromagnetic properties in real time when the temperature approaches the workpiece's critical phase transition zone. By monitoring this phase difference, the system can accurately determine whether the workpiece is approaching the critical phase transition zone. In specific operation, the induction coil collects voltage and current signals in real time during operation and uses a phase-locked loop circuit to accurately measure the time difference between the voltage zero crossing point and the current waveform peak point. Based on this time difference, the system can calculate the absolute value of the phase difference corresponding to the change in electromagnetic properties 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 is approaching its critical phase transition zone, at which point the micropulse power compensation mode is activated. Once the micropulse compensation mode is activated, the system will dynamically adjust the amplitude and output interval of the micropulse according to the phase difference change rate. Specifically, the amplitude of the micropulse power is piecewise linearly related to the phase difference change rate, and is adjusted according to the real-time changing phase difference. In order to better cope with electromagnetic noise in a vacuum environment, the system adopts an asymmetric waveform design, combining high-frequency narrow pulse width pulses with low-frequency pulse width pulses for alternating output, thereby compensating for heat while suppressing electromagnetic interference and maintaining the stability and accuracy of the system.

[0069] To ensure the stability and accuracy of the system under complex working conditions, the SCADA system in this embodiment reconstructs the data acquisition module and replaces it with 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 on the phase difference, but also optimizes it according to the thermophysical parameters of the workpiece material. By establishing a mapping relationship between the phase difference and the micropulse power amplitude, the system can automatically adjust the control strategy when processing workpieces of different materials. For example, for materials with higher conductivity, the system improves heating efficiency by increasing the micropulse power amplitude and optimizing the output interval; for materials with lower conductivity, the system reduces the power output to avoid overheating. In the critical region of phase change, the control of workpiece temperature faces a large hysteresis effect, especially the thermal diffusion characteristics of the material have a great influence on the temperature response. Therefore, this embodiment generates a thermal hysteresis compensation curve based on the historical phase difference absolute value data, and adjusts the output of the micropulse power according to the curve. Specifically, the thermal hysteresis compensation amount is calculated by integrating the square of the phase difference change rate, and the compensation intensity is dynamically adjusted 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 region of phase change. These are all extended implementation methods known to ordinary technicians in this field.

[0070] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A vacuum induction heating temperature closed-loop control system integrated with SCADA, characterized in that: include: An induction coil unit, wherein the surface of the conductor layer of the induction coil unit is composited with a functional material layer, the functional material layer having a preset Curie temperature that matches the target temperature control range 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 the electromagnetic impedance undergoes a sudden change covers the critical temperature range of the phase change of the workpiece; The phase difference detection module collects the voltage and current signals generated by the induction coil in real time during operation, and directly obtains the absolute value of the phase difference that characterizes the electromagnetic characteristics of the induction coil based on the time difference between the voltage and current signals. , no analog-to-digital conversion is required; Absolute value of phase difference The time difference between the voltage zero crossing point and the current waveform peak point is realized by the phase-locked loop circuit The precise measurement of Calculated, where is the operating frequency of the induction coil; Micropulse compensation unit, when the absolute value of the phase difference Exceeds the preset first threshold for the first time When the temperature of the workpiece enters the critical phase change region, the micro-pulse power compensation mode is immediately activated to output micro-pulse power to the induction coil; In the micropulse power compensation mode, the amplitude of the micropulse The rate of change of the absolute value of the phase difference There is a piecewise linear relationship between them, 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 is Falling back to the preset second threshold To achieve closed-loop control of workpiece temperature; The micro pulse output in the micro pulse power compensation mode is an asymmetric waveform, which is composed of a high frequency narrow pulse width pulse train and a low frequency wide pulse width pulse train alternating. In the range of 8kHz to 12kHz, the pulse width The frequency of the low-width pulse train is in the range of 8μs to 12μs. In the range of 0.8kHz to 1.2kHz, the pulse width In the range of 80μs to 120μs, and satisfying the relationship .

2. A vacuum induction heating temperature closed-loop control system integrated with SCADA according to claim 1, characterized in that: When the SCADA system detects that the pressure fluctuation in the vacuum furnace chamber exceeds the preset threshold, it will automatically The sampling frequency is increased from 1kHz to 10kHz, and the Kalman filter is enabled for continuous sampling. The sequence is predicted and corrected, and the state equation and observation equation of the Kalman filter are as follows: ， ， in, for Moment Predicted value, for The change in vacuum degree at time, for Moment Observed values, 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.

3. A vacuum induction heating temperature closed-loop control system integrated with SCADA according to claim 1, characterized in that: The data acquisition module of the SCADA system is reconstructed based on the absolute value of the phase difference Time series database, and pre-established Compensation power amplitude with micro-pulse The mapping relationship table between them is optimized by offline simulation combined with the thermophysical parameters of different workpiece materials, in which material coefficients are introduced for different workpiece materials. , and its calculation formula is: ， in, is the electrical 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.

4. A vacuum induction heating temperature closed-loop control system integrated with SCADA according to claim 1, characterized in that: When the workpiece temperature enters the critical phase change region and remains in this region, the system calculates the absolute value of the historical phase difference. The thermal hysteresis compensation curve is automatically generated according to the compensation amount. The output of micro-pulse power is dynamically adjusted, where is a proportionality factor related to the thermal diffusivity of the workpiece material.

5. A vacuum induction heating temperature closed-loop control system integrated with SCADA according to claim 1, characterized in that: The surface of the functional material layer is provided with a periodically arranged array of micro-pits, the diameter of which is In the range of 50 μm to 100 μm, the aspect ratio is in the range of 1:1 to 1:

2.

6. A vacuum induction heating temperature closed-loop control system integrated with SCADA according to claim 5, characterized in that: The system is integrated with a self-test module, which monitors the absolute value of the phase difference within three consecutive working cycles in real time. The standard deviation of fluctuation ,when When the error is less than 0.5°, the phase difference detection module is automatically determined to be abnormal and switches to the redundant detection channel. At the same time, the characteristic code containing the fault type and occurrence time is recorded in the event log of the SCADA system.

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