A black fish refrigeration control system and method based on a magneto-electric coupling field

Abstract

The application discloses a kind of black fish refrigeration preservation control system and method based on magnetoelectric coupling field, belong to aquatic product low temperature preservation technical field, system contains refrigeration cabin, magnetoelectric coupling generation unit, multi-parameter real-time detection unit, intelligent control unit and refrigeration cycle unit;The method first establishes black fish physical property parameter library, constructs ice crystal nucleation kinetics model and quality loss model with the introduction of magnetoelectric coupling correction term, to obtain the optimal freezing curve with the double target optimization of quality loss and energy consumption;Extended Kalman filter fusion sensing data is used, and the freezing state of black fish and ice crystal characteristic parameter are solved in real time;Through the cooperative regulation of rolling horizon model prediction control magnetic field, electric field and refrigeration power, multi-parameter is converted into low field intensity preservation mode after reaching standard.This application effectively shortens the maximum ice crystal generation zone through time, greatly reduces thawing juice loss, improves protein retention rate, solves the problem of traditional single field freezing control extensive, poor quality consistency.

Description

Technical Field

[0001] This invention relates to the field of low-temperature preservation technology for aquatic products, and in particular to a control system and method for freezing and preserving black carp based on a magnetoelectric coupling field. Background Technology

[0002] Snakehead fish is an important freshwater economic fish in my country, with tender flesh and high protein content. It is in high demand and has become a core ingredient in the popular ready-to-cook dish, pickled fish. Freezing is the mainstream method to ensure product quality stability during transportation, distribution, and end-consumer stages, and to extend the shelf life of snakehead fish. However, during traditional air freezing or plate freezing, snakehead fish spends a relatively long time in the maximum ice crystal formation zone (approximately -1℃ to -6℃), easily forming large needle-like ice crystals that pierce muscle cell membranes and muscle fiber structures. This leads to severe juice loss, protein denaturation, and deteriorated taste after thawing, seriously affecting product quality and economic value.

[0003] In recent years, emerging technologies such as magnetic field-assisted freezing and electrostatic field-assisted freezing have been gradually applied to the preservation of aquatic products. Magnetic fields can promote supercooling and refine ice crystals by altering the hydrogen bond network of water molecules; electric fields can enhance the nucleation rate through the polarization effect of water molecules. However, existing technologies generally suffer from the following drawbacks: (1) Most of them use magnetic or electric fields alone, without fully exploring the synergistic effect mechanism of magnetoelectric coupling, lacking quantitative coupling dynamics models, resulting in high energy consumption and limited quality improvement; (2) The control method is crude, mostly constant field strength switching control, and no exclusive optimal freezing curve is designed for the unique freezing phase transition law of blackfish, so it is impossible to achieve precise tracking control throughout the process; (3) It lacks the ability to provide real-time feedback and adaptive control of multiple parameters, making it difficult to cope with control deviations caused by individual differences and initial state fluctuations in blackfish, resulting in poor robustness.

[0004] Therefore, developing a precise freezing and preservation control system and optimization algorithm for snakehead fish based on magnetoelectric coupling field, quantifying the coupling effect, customizing the freezing curve, and realizing adaptive closed-loop control are technical problems that urgently need to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a control system and method for freezing and preserving black carp based on a magnetoelectric coupling field, which solves problems such as lack of a quantitative coupling dynamics model, low control accuracy of the freezing process, poor quality consistency, and poor robustness of open-loop or single-parameter closed-loop control.

[0006] To achieve the above objectives, the present invention provides a black carp freezing and preservation control system based on a magnetoelectric coupling field, including a freezing chamber, a magnetoelectric coupling generating unit, a multi-parameter real-time detection unit, an intelligent control unit, and a refrigeration cycle unit; The magnetoelectric coupling generating unit and the refrigeration cycle unit are both located inside the refrigeration chamber, and are used to apply a coordinated alternating magnetic field and a high-voltage electrostatic field and provide continuously adjustable cooling capacity during the freezing process of blackfish. The multi-parameter real-time detection unit is used to collect the center temperature, surface temperature, bioimpedance amplitude, and ultrasonic backscatter signal of the snakehead fish in real time. The intelligent control unit is electrically connected to the magneto-electric coupling generating unit, the multi-parameter real-time detection unit, and the refrigeration cycle unit, respectively. Based on the real-time detection data, it dynamically calculates the control quantities of magnetic induction intensity, electric field intensity, and refrigeration power, so that the center temperature of the blackfish tracks the preset optimal freezing target curve.

[0007] Preferably, the magnetoelectric coupling generating unit includes an alternating magnetic field generating module and a high-voltage electrostatic field generating module; an insulating electromagnetic shielding layer is provided between the alternating magnetic field generating module and the high-voltage electrostatic field generating module to eliminate electromagnetic interference between the high-voltage electrostatic field and the alternating magnetic field. The alternating magnetic field generating module uses a Helmholtz coil array arranged symmetrically in the upper and lower parts, with a magnetic induction intensity adjustment range of 0 to 600 mT and an operating frequency adjustment range of 0 to 50 Hz; the high-voltage electrostatic field generating module uses horizontal parallel plate insulated electrodes, with an electric field intensity adjustment range of 0 to 120 kV / m, the electrodes are located in the uniform intensity region at the center of the coil, and the fish-carrying net frame is set between the two electrodes.

[0008] Preferably, the multi-parameter real-time detection unit includes a fiber optic temperature sensing array, a four-electrode bioimpedance detection module, and an ultrasonic ice crystal monitoring module. The fiber optic temperature sensing array includes a measuring point at the center of the fish body and a measuring point on the surface of the fish body. The temperature measurement accuracy is not less than ±0.05℃. The measuring point adopts a needle-type invasive structure and is inserted into the thickest part of the back muscle of the blackfish. The four-electrode bioimpedance module operates in the frequency range of 1kHz to 1MHz and collects muscle impedance through equally spaced needle electrodes for calculating the ice crystal integral. The ultrasonic ice crystal monitoring module has a transmission frequency of 5-15MHz and uses a contact probe to fit the surface of the fish. The average particle size and distribution uniformity of the ice crystals are characterized by backscattered signals.

[0009] Preferably, the intelligent control unit includes a data preprocessing module, a frozen state estimation module, an optimal curve storage module, a model prediction control module, and a drive execution module; The optimal curve storage module contains a family of optimal freezing target curves and a corresponding model parameter library for black carp of different sizes and at different initial temperatures. The frozen state estimation module outputs ice crystal integral number, average particle size and phase transition rate based on the fusion of multi-source sensor data. The model predictive control module uses the minimum temperature tracking error, the minimum magnetoelectric energy consumption, and the smoothness of control increment as objective functions, and continuously optimizes the output of three control quantities.

[0010] This invention also provides a method for controlling the freezing and preservation of black carp based on a magnetoelectric coupling field, comprising the following steps: S1. Conduct physical property measurements and freezing experiments on blackfish of different sizes in advance to establish a standardized parameter database; S2. Construct a dynamic model of ice crystal nucleation and growth in blackfish under a magnetoelectric coupling field; S3. With the goal of minimizing the overall quality loss, plan the optimal freezing target curve for the blackfish; S4. The extended Kalman filter algorithm is used to fuse multi-source sensor data and estimate the freezing state and ice crystal characteristic parameters of the blackfish in real time. S5. Based on the rolling time-domain model predictive control algorithm, adaptive and coordinated regulation of magnetic field, electric field and cooling capacity; S6. Multi-parameter fusion determines the freezing endpoint and switches to low-temperature preservation mode.

[0011] Preferably, in step S1, the muscle moisture content of blackfish of different sizes is measured in advance. soluble solids mass fraction The actual freezing point temperature of black carp was calibrated using differential scanning calorimetry. The formula for calculating the freezing point is: ; In the formula, The freezing point at Celsius; , , A specific freezing point depression correction coefficient for blackfish was obtained through calibration experiments; at the same time, impedance model parameters and kinetic model parameters for each specification were calibrated to form a database for use during actual freezing.

[0012] Preferably, in S2, based on the classical homogeneous nucleation theory, three nucleation barrier correction terms—magnetic field, electric field, and magnetoelectric coupling—are introduced to establish a nucleation rate model for ice crystals under a coupled field: ; In the formula, This represents the homogeneous nucleation rate of ice crystals. It is the pre-nucleation factor; The critical Gibbs free energy for homogeneous nucleation; This is the correction term for the alternating magnetic field barrier. This is a correction term for the electrostatic field barrier. This is a correction term for the magnetoelectric coupling cooperative barrier. Boltzmann's constant; Thermodynamic temperature; in, , For ice-water interfacial tension, The difference in free energy per unit volume of liquid-solid phase transition; , The magnetic field effect coefficient of the snakehead muscle tissue was determined through calibration experiments. Magnetic flux density This is the magnetic field frequency correction factor. This refers to the effective volume of the fish's body. , The vacuum permittivity, Let be the relative permittivity of water. is the relative permittivity of ice. , Electric field strength; , The empirical coefficient of magnetoelectric coupling in blackfish tissue. The angle between the directions of the magnetic field and the electric field. This is a phase transition progress correction index; the coupling effect gradually weakens as the phase transition progresses. The integral of ice crystals is a core state parameter characterizing the progress of the freezing phase transition in the muscle tissue of snakehead fish.

[0013] Preferably, in S3, a dynamic model of quality loss during freezing of black carp is constructed based on the improved Arrhenius equation, with juice loss and protein denaturation as the core quality indicators. The expression for the quality loss rate is as follows: ; In the formula, This represents the relative quality retention rate, with an initial value of 1. Pre-exponential factors; The apparent activation energy for quality deterioration; It is the gas constant; , These are the quality retention factors under a single magnetic field and a single electric field, respectively, with values ​​ranging from (0, 1]. As the magnetoelectric coupling quality synergy factor, satisfying < This demonstrates the additional suppression effect of the coupled field on quality degradation; With the goal of minimizing overall quality loss and total energy consumption as the multi-objective optimization objectives, the optimal freezing target curve of the blackfish's center temperature over time was obtained.

[0014] Preferably, in step S4, the center temperature, surface temperature, bioimpedance, and ultrasonic echo signals of the snakehead fish are collected in real time. After filtering preprocessing, the extended Kalman filter algorithm is used to fuse the multi-source data to estimate the ice crystal integral number at the current moment. Average ice crystal size With phase transition rate ; Among them, the ice crystal integral number Impedance amplitude calculation based on characteristic frequency: ; In the formula, This represents the muscle impedance amplitude at the current characteristic frequency of 100kHz. The reference impedance amplitude is the value under the unfrozen condition at 0°C. , All are calibration coefficients specific to blackfish, meeting the requirements. = hour =0 boundary condition; Based on the ultrasonic backscattering method, combined with the calculated ice crystal integral number Multi-source fusion calculations were performed to obtain the average ice crystal size. The formula is as follows: ; In the formula, This is the particle size calibration constant, determined through experimental calibration using standard particle size samples. The ultrasonic scattering correction coefficient for snakehead muscle tissue was obtained by fitting the snakehead frozen calibration experiment. The integral backscattering coefficient, , The power spectral density of the backscattered signal. and These are the upper and lower limits of the effective working bandwidth of the ultrasonic probe, respectively. Based on the measured ice crystal integral number The phase transition rate was obtained from the time series using sliding window differencing and smoothing filtering. Observations: ; In the formula, The sampling interval is denoted as .

[0015] Preferably, in S5, a rolling time-domain model predictive control is adopted, and the objective function is optimized as follows: ; The constraints include: Magnetic induction intensity constraint: ; Electric field strength constraint: ; Cooling power constraints: ; Cooling rate constraint: ; In the formula, To predict the time domain, To control the time domain; The predicted core temperature of the fish. The optimal freezing target temperature; , , These are the control increments for magnetic induction intensity, electric field intensity, and cooling power, respectively. , , , All are weighting coefficients. For the current discrete control moment, Indexing for future time steps; , These represent the minimum and maximum limits of magnetic flux density, respectively. , These represent the minimum and maximum limits of the electric field strength, respectively. This is the rated maximum power of the refrigeration system. Temperature at the center of the fish's body The maximum allowable cooling rate at the center of the fish's body.

[0016] Therefore, the beneficial effects of the above-mentioned black carp freezing and preservation control system and method based on magnetoelectric coupling field in this invention are as follows: (1) The ice crystal nucleation rate formula of the present invention is derived by introducing the magnetoelectric coupling synergistic barrier correction term. The physical mechanism is self-consistent and the synergistic effect of magnetic field and electric field is quantified. Compared with single magnetic field or single electric field freezing, the nucleation rate and ice crystal refinement efficiency are greatly improved.

[0017] (2) This invention addresses the characteristics and quality deterioration patterns of snakehead muscle tissue, and solves the optimal freezing temperature trajectory with the goal of minimizing quality loss. It breaks through the limitations of traditional constant-rate cooling, reduces the loss rate of thawed juices from snakehead, and significantly improves the retention rate of myofibril protein.

[0018] (3) The present invention adopts a rolling time-domain model predictive control algorithm to achieve real-time coordinated optimization of magnetic field, electric field and cooling capacity. Combined with multi-source sensor fusion state estimation, the temperature tracking deviation is controlled within ±0.2℃. It can adapt to blackfish of different specifications and different initial states, thus improving the batch quality consistency.

[0019] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the composition structure of an embodiment of a black carp freezing and preservation control system based on a magnetoelectric coupling field according to the present invention. Figure 2 This is a step diagram of an embodiment of the method for controlling the freezing and preservation of black carp based on a magnetoelectric coupling field according to the present invention. Detailed Implementation

[0021] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0022] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0023] Example 1: like Figure 1 As shown, this embodiment provides a black carp freezing and preservation control system based on a magnetoelectric coupling field, including a freezing chamber, a magnetoelectric coupling generating unit, a multi-parameter real-time detection unit, an intelligent control unit, and a refrigeration cycle unit.

[0024] The refrigeration chamber is an insulated, sealed cavity with an insulated fish-supporting mesh frame inside. The magnetoelectric coupling generating unit and the refrigeration cycle unit are both located on the inner wall of the chamber and around the mesh frame, forming a spatially uniform magnetoelectric coupling field and temperature field. The refrigeration cycle unit employs a cascade refrigeration system with continuously adjustable cooling power, working in conjunction with a cooling fan and deflectors to achieve a rapid and uniform temperature response within the chamber.

[0025] The magneto-electric coupling unit comprises an alternating magnetic field generating module and a high-voltage electrostatic field generating module. An insulating electromagnetic shielding layer is installed between the two modules to eliminate electromagnetic interference between the high-voltage electrostatic field and the alternating magnetic field. The alternating magnetic field generating module employs a symmetrical Helmholtz coil array, capable of generating a uniform alternating magnetic field adjustable from 0 to 600 mT and from 0 to 50 Hz. The high-voltage electrostatic field generating module uses parallel insulating electrode plates horizontally arranged in the center region of the coils, capable of generating an adjustable electrostatic field from 0 to 120 kV / m. The magnetic field direction is set at a controllable angle to the electric field direction to achieve optimal coupling effect. An insulating electromagnetic shielding layer is installed between the coils and electrodes, and the two drive systems are independently filtered and opto-isolated to eliminate electromagnetic interference.

[0026] The multi-parameter real-time detection unit includes a fiber optic temperature sensor array, a four-electrode bioimpedance detection module, and an ultrasonic ice crystal monitoring module. The fiber optic temperature sensor has a central measuring point and a surface measuring point. The central measuring point is inserted into the thickest part of the back muscle of the snakehead fish using a needle, while the surface measuring point is attached to the lateral line of the fish. The four-electrode module uses equally spaced needle electrodes inserted into the muscle to reflect the proportion of ice crystal formation through changes in impedance spectrum. The ultrasonic module uses a contact probe attached to the surface of the fish to characterize the size and distribution of ice crystals through echo scattering characteristics.

[0027] The intelligent control unit is the core of the system, comprising a data preprocessing module, a frozen state estimation module, an optimal curve storage module, a model predictive control module, and a drive execution module. The optimal curve storage module has multiple built-in optimal frozen target curves and corresponding model parameter libraries for different sizes of black carp; the frozen state estimation module integrates multi-source data to output the current phase transition state and ice crystal parameters; the model predictive control module focuses on tracking the target curve and continuously optimizes the output control commands for magnetic field, electric field, and cooling power.

[0028] Based on the above system, such as Figure 2 As shown, the method for controlling the freezing and preservation of black carp based on a magnetoelectric coupling field in this embodiment specifically includes the following steps: S1. Conduct preliminary physical property measurements and freezing experiments on black carp of different sizes to establish a standardized parameter database: Basic physical property measurements and freezing experiments were conducted on small, medium and large snakehead fish in advance. The measured indicators included muscle water content, soluble solids mass fraction, muscle pH value and single tail mass. The actual freezing point temperature of each size of snakehead fish was calibrated by differential scanning calorimetry. The reference freezing curve and impedance reference value under no external field were obtained by no-load freezing experiment.

[0029] Freezing point temperature is calculated using a blackfish-specific correction formula: In the formula, This is the freezing point (negative value) at Celsius temperature. This refers to the water content (mass fraction) of muscle. This refers to the mass fraction of soluble solids. , , This is a correction factor for the freezing point depression specific to blackfish, expressed in °C, obtained through fitting a calibration experiment.

[0030] Simultaneously, the parameters of the ice crystal integral impedance model, ice crystal nucleation and growth kinetics parameters, and quality loss model parameters are calibrated to form a standardized parameter database. During actual freezing operations, only the snakehead fish size and initial temperature need to be input, and the system automatically calls up the corresponding parameters, eliminating the need for repeated calibration.

[0031] S2. Constructing a dynamic model of ice crystal nucleation and growth in blackfish under a magnetoelectric coupled field: Based on the classical homogeneous nucleation theory, an alternating magnetic field barrier correction term, an electrostatic field barrier correction term, and a magnetoelectric coupling synergistic correction term are introduced respectively. All three terms are negative and work together to reduce the critical nucleation barrier and increase the nucleation rate, thus establishing a model for the ice crystal nucleation rate under a coupled field: In the formula, This represents the homogeneous nucleation rate of ice crystals. It is the pre-nucleation factor; The critical Gibbs free energy for homogeneous nucleation (positive value); This is the alternating magnetic field barrier correction term (negative value); This is the electrostatic field barrier correction term (negative value); This is the magnetoelectric coupling cooperative barrier correction term (negative value); Boltzmann's constant; It is the thermodynamic temperature.

[0032] in, , For ice-water interfacial tension, The difference in free energy per unit volume between liquid and solid phase transitions.

[0033] This demonstrates the perturbation effect of the alternating magnetic field on the hydrogen bond network of water molecules, promoting nucleation. The magnetic field effect coefficient of the snakehead muscle tissue was determined through calibration experiments. Magnetic flux density This is the magnetic field frequency correction factor. This refers to the effective volume of the fish's body.

[0034] This demonstrates the promoting effect of water molecule polarization on nucleation. The vacuum permittivity, Let be the relative permittivity of water. is the relative permittivity of ice. , denoted as electric field strength.

[0035] This reflects the additional nucleation driving force generated by the combined action of the magnetic field and the electric field. Its absolute value is greater than the linear superposition value of the correction terms of a single magnetic field and a single electric field, thus achieving synergistic effect. The empirical coefficient of magnetoelectric coupling in blackfish tissue. The angle between the directions of the magnetic field and the electric field; The phase transition progress correction index gradually weakens as the phase transition progresses. The integral of ice crystals is a core state parameter characterizing the progress of the freezing phase transition in the muscle tissue of snakehead fish.

[0036] Simultaneously, an ice crystal growth rate model was established, taking into account the combined effects of diffusion control and interfacial dynamics, and combining magnetoelectric coupling to correct the water molecule diffusion coefficient, thereby quantifying the evolution of ice crystal size over time.

[0037] S3. With the goal of minimizing overall quality loss, plan the optimal freezing target curve for the blackfish: Using the loss rate of muscle juice and the denaturation rate of myofibrillar protein as the core quality indicators, a kinetic model of quality loss during the freezing process was constructed based on the improved Arrhenius equation: In the formula, This represents the relative quality retention rate, with an initial value of 1. Pre-exponential factors; The apparent activation energy for quality deterioration; It is the gas constant; , These are the quality retention factors under a single magnetic field and a single electric field, respectively, with values ​​ranging from (0, 1]. As the magnetoelectric coupling quality synergy factor, satisfying < This demonstrates the additional suppressive effect of the coupled field on quality degradation.

[0038] With the goal of minimizing overall quality loss and total energy consumption, and using the upper and lower limits of cooling rate, the range of magnetoelectric parameters, and equipment constraints as boundary conditions, the Gaussian pseudospectral method was employed to obtain the optimal trajectory of the blackfish's center temperature over time, i.e., the optimal freezing target curve. This curve is characterized by: moderately rapid cooling during the pre-cooling stage; rapid passage through the maximum ice crystal formation zone at a stable rate during the phase transition stage; and adjusted cooling rate during the cryogenic stage, achieving an optimal balance between ice crystal refinement, quality preservation, and energy consumption control.

[0039] S4. The extended Kalman filter algorithm is used to fuse multi-source sensor data and estimate the freezing state and ice crystal characteristic parameters of the blackfish in real time. Real-time acquisition of core temperature, surface temperature, bioimpedance, and ultrasonic echo signals from snakehead fish was performed. After filtering and preprocessing, the extended Kalman filter algorithm was used to fuse the multi-source data and estimate the ice crystal integral number at the current moment. Average ice crystal size With phase transition rate .

[0040] Among them, the ice crystal integral number Impedance amplitude calculation based on characteristic frequency: In the formula, This represents the muscle impedance amplitude at the current characteristic frequency of 100kHz. The reference impedance amplitude is the value under the unfrozen condition at 0°C. , All are calibration coefficients specific to blackfish, meeting the requirements. = hour =0 boundary condition.

[0041] Based on the ultrasonic backscattering method, combined with the calculated ice crystal integral number Multi-source fusion calculations were performed to obtain the average ice crystal size. The formula is as follows: In the formula, This is the particle size calibration constant, determined through experimental calibration using standard particle size samples. The ultrasonic scattering correction coefficient for snakehead muscle tissue was obtained by fitting the snakehead frozen calibration experiment. The integral backscattering coefficient, , The power spectral density of the backscattered signal. and These represent the upper and lower limits of the effective operating bandwidth of the ultrasonic probe.

[0042] Based on the measured ice crystal integral number The phase transition rate was obtained from the time series using sliding window differencing and smoothing filtering. Observations: In the formula, The sampling interval is denoted as .

[0043] The fusion estimation results are used as feedback state variables for the control algorithm to achieve observability and controllability of the whole phase transition process.

[0044] S5. Based on the rolling time-domain model predictive control algorithm, adaptively and collaboratively regulate the magnetic field, electric field, and cooling capacity: Employing a rolling time-domain model predictive control (MPC) architecture, with future... The optimization objectives are to minimize temperature tracking error, smooth control increment, and minimum total energy consumption. The solution is then used to determine the future... The optimal control sequence is determined step by step, with only the first step of the control input executed, and the next step being a rolling optimization based on the latest state.

[0045] The objective function to be optimized is: The constraints include: Magnetic induction intensity constraint: ; Electric field strength constraint: ; Cooling power constraints: ; Cooling rate constraint: .

[0046] In the formula, To predict the time domain, To control the time domain; The predicted core temperature of the fish. The optimal freezing target temperature; , , These are the control increments for magnetic induction intensity, electric field intensity, and cooling power, respectively. , , , All are weighting coefficients. For the current discrete control moment, Indexing for future time steps; , These represent the minimum and maximum limits of magnetic flux density, respectively. , These represent the minimum and maximum limits of the electric field strength, respectively. This is the rated maximum power of the refrigeration system. Temperature at the center of the fish's body The maximum allowable cooling rate at the center of the fish's body.

[0047] During the control process, the control strategy is automatically switched in stages based on the core temperature of the fish: ① Pre-cooling stage: The core temperature is higher than the freezing point It primarily focuses on cooling and temperature reduction, while applying weak magnetic and electric assistance to reduce supercooling fluctuations; ② Phase transition stage (maximum ice crystal formation zone): The central temperature is at In the range, a strong magnetoelectric synergistic mode is triggered, applying high magnetic induction intensity and high electric field intensity to maximize the promotion of nucleation and refinement of ice crystals, while matching the cooling power to maintain the set cooling rate. ③ Cryogenic stage: The core temperature is lower than Once the main body of ice crystal formation is complete, the magnetic field strength is gradually reduced, and the cooling and temperature reduction are the primary methods to decrease operating energy consumption.

[0048] S6. Multi-parameter fusion determines the freezing endpoint and switches to low-temperature preservation mode: The freezing process is considered complete when all three of the following conditions are met: ① Fish body core temperature ≤-18℃; ② The integral number of ice crystals in freezeable water ≥90; ③ Average ice crystal size ≤Preset particle size threshold.

[0049] Once the freezing is complete, the system automatically switches to low-temperature preservation mode, reducing the magnetic induction intensity to 15%–25% of the peak value and the electric field intensity to 5%–15% of the peak value. This maintains ice crystal stability with low energy consumption, inhibits ice crystal recrystallization during storage, and extends the storage period.

[0050] Experimental verification: Based on the above method, this embodiment focuses on the freezing and preservation control of a single fresh black carp weighing 750g. The specific implementation process is as follows: (1) Parameter call: This snakehead fish is of medium size (500-1000g). The system retrieves the medium size parameter library: muscle moisture content. =78.5, soluble solids =1.2; Freezing point correction factor =1.72℃, =0.48℃, =0.11℃, the freezing point is calculated. The maximum ice crystal formation zone is determined to be between -6.93℃ and -0.93℃, with an approximation temperature of approximately -0.93℃.

[0051] Impedance model parameters: =0.42, =1.36; Nucleation kinetic parameters: magnetic field effect coefficient of snakehead muscle tissue =8.2×10⁻¹² J / (T²·m³), empirical coefficient of magnetoelectric coupling in blackfish tissue =3.1×10⁻⁶ J·K / (T·V·m⁴), Phase transition progress correction index =0.65.

[0052] (2) Generation of the optimal curve: With minimizing juice loss as the core objective, the optimal freezing target curve is obtained by solving the problem: Pre-cooling stage (room temperature → -0.93℃): average cooling rate 1.5℃ / min, magnetic induction intensity 80mT, electric field strength 10kV / m; Phase transition stage (-0.93℃→-6.93℃): average cooling rate 0.8℃ / min, magnetic induction intensity 350mT, electric field strength 60kV / m, frequency 20Hz; Cryogenic stage (-6.93℃→-18℃): average cooling rate 1.2℃ / min, magnetic induction intensity gradually decreases to 100mT, electric field intensity decreases to 10kV / m.

[0053] (3) Closed-loop control operation: After the system starts up, the needle-type fiber optic temperature sensor collects the center temperature of the snakehead's back, with a sampling period of 2 seconds; the four-electrode module collects the impedance value at 100 kHz every 10 seconds; and the ultrasonic probe collects the backscatter signal every 30 seconds. The intelligent control unit performs model prediction optimization every 5 seconds, continuously adjusting the cooling power, magnetic induction intensity, and electric field intensity to ensure that the actual center temperature tracks the target curve, with the maximum tracking deviation controlled within ±0.2℃.

[0054] (4) Endpoint determination and preservation: When the core temperature dropped to -18.2℃, the ice crystal integral calculated by impedance method was 92.3%, and the average ice crystal size estimated by ultrasound was 28μm (below the threshold of 40μm), indicating that freezing was complete. The system was then switched to maintenance mode, with the magnetic field maintained at 80mT, the electric field maintained at 8kV / m, and the chamber temperature stabilized at -20℃.

[0055] As shown in Table 1, the juice loss rate of the black carp treated in this embodiment after thawing was 2.1%, which is 69% lower than the 6.8% of traditional air freezing; the myofibrillar protein retention rate was increased by 27%, energy consumption was reduced by 6%, and the preservation quality was significantly improved.

[0056] Table 1. Comparison of the effects of the traditional air freezing method and the method in this embodiment.

[0057] Therefore, this invention employs a black carp freezing and preservation control system and method based on a magnetoelectric coupling field, quantifying the magnetoelectric coupling synergistic nucleation mechanism, effectively refining ice crystals, reducing fish cell damage, and minimizing thawing juice loss. Relying on multi-sensor fusion and model predictive control, the temperature tracking deviation is ≤±0.2℃, adaptable to black carp of different sizes. The system dynamically adjusts the magnetoelectric field strength in stages, balancing preservation effect and energy consumption. During the storage stage, the low field strength inhibits ice crystal recrystallization, improving overall product quality and shelf life.

[0058] 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 preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A black carp freezing and preservation control system based on a magnetoelectric coupling field, characterized in that: It includes a cryogenic chamber, a magneto-electric coupling generating unit, a multi-parameter real-time detection unit, an intelligent control unit, and a refrigeration cycle unit; The magnetoelectric coupling generating unit and the refrigeration cycle unit are both located inside the refrigeration chamber, and are used to apply a coordinated alternating magnetic field and a high-voltage electrostatic field and provide continuously adjustable cooling capacity during the freezing process of blackfish. The multi-parameter real-time detection unit is used to collect the center temperature, surface temperature, bioimpedance amplitude, and ultrasonic backscatter signal of the snakehead fish in real time. The intelligent control unit is electrically connected to the magneto-electric coupling generating unit, the multi-parameter real-time detection unit, and the refrigeration cycle unit, respectively. Based on the real-time detection data, it dynamically calculates the control quantities of magnetic induction intensity, electric field intensity, and refrigeration power, so that the center temperature of the blackfish tracks the preset optimal freezing target curve.

2. The black carp freezing and preservation control system based on magnetoelectric coupling field according to claim 1, characterized in that: The magneto-electric coupling generating unit includes an alternating magnetic field generating module and a high-voltage electrostatic field generating module; an insulating electromagnetic shielding layer is provided between the alternating magnetic field generating module and the high-voltage electrostatic field generating module to eliminate electromagnetic interference between the high-voltage electrostatic field and the alternating magnetic field. The alternating magnetic field generating module uses a Helmholtz coil array arranged symmetrically in the upper and lower parts, with a magnetic induction intensity adjustment range of 0 to 600 mT and an operating frequency adjustment range of 0 to 50 Hz; the high-voltage electrostatic field generating module uses horizontal parallel plate insulated electrodes, with an electric field intensity adjustment range of 0 to 120 kV / m, the electrodes are located in the uniform intensity region at the center of the coil, and the fish-carrying net frame is set between the two electrodes.

3. The black carp freezing and preservation control system based on magnetoelectric coupling field according to claim 1, characterized in that: The multi-parameter real-time detection unit includes a fiber optic temperature sensing array, a four-electrode bioimpedance detection module, and an ultrasonic ice crystal monitoring module. The fiber optic temperature sensing array includes a measuring point at the center of the fish body and a measuring point on the surface of the fish body. The temperature measurement accuracy is not less than ±0.05℃. The measuring point adopts a needle-type invasive structure and is inserted into the thickest part of the back muscle of the blackfish. The four-electrode bioimpedance module operates in the frequency range of 1kHz to 1MHz and collects muscle impedance through equally spaced needle electrodes for calculating the ice crystal integral. The ultrasonic ice crystal monitoring module has a transmission frequency of 5-15MHz and uses a contact probe to fit the surface of the fish. The average particle size and distribution uniformity of the ice crystals are characterized by backscattered signals.

4. The black carp freezing and preservation control system based on magnetoelectric coupling field according to claim 1, characterized in that: The intelligent control unit includes a data preprocessing module, a frozen state estimation module, an optimal curve storage module, a model prediction control module, and a drive execution module. The optimal curve storage module contains a family of optimal freezing target curves and a corresponding model parameter library for black carp of different sizes and at different initial temperatures. The frozen state estimation module outputs ice crystal integral number, average particle size and phase transition rate based on the fusion of multi-source sensor data. The model predictive control module uses the minimum temperature tracking error, the minimum magnetoelectric energy consumption, and the smoothness of control increment as objective functions, and continuously optimizes the output of three control quantities.

5. A method for controlling the freezing and preservation of black carp based on a magnetoelectric coupling field, applied to the control system described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Conduct physical property measurements and freezing experiments on blackfish of different sizes in advance to establish a standardized parameter database; S2. Construct a dynamic model of ice crystal nucleation and growth in blackfish under a magnetoelectric coupling field; S3. With the goal of minimizing the overall quality loss, plan the optimal freezing target curve for the blackfish; S4. The extended Kalman filter algorithm is used to fuse multi-source sensor data and estimate the freezing state and ice crystal characteristic parameters of the blackfish in real time. S5. Based on the rolling time-domain model predictive control algorithm, adaptive and coordinated regulation of magnetic field, electric field and cooling capacity; S6. Multi-parameter fusion determines the freezing endpoint and switches to low-temperature preservation mode.

6. The method for controlling the freezing and preservation of black carp based on a magnetoelectric coupling field according to claim 5, characterized in that: In S1, the muscle moisture content of black carp of different sizes was measured in advance. soluble solids mass fraction The actual freezing point temperature of black carp was calibrated using differential scanning calorimetry. The formula for calculating the freezing point is: ； In the formula, The freezing point at Celsius; , , A specific freezing point depression correction coefficient for blackfish was obtained through calibration experiments; at the same time, impedance model parameters and kinetic model parameters for each specification were calibrated to form a database for use during actual freezing.

7. The method for controlling the freezing and preservation of black carp based on a magnetoelectric coupling field according to claim 6, characterized in that: In S2, based on the classical homogeneous nucleation theory, three nucleation barrier correction terms—magnetic field, electric field, and magnetoelectric coupling—are introduced to establish a model of ice crystal nucleation rate under a coupled field: ； In the formula, This represents the homogeneous nucleation rate of ice crystals. It is the pre-nucleation factor; The critical Gibbs free energy for homogeneous nucleation; This is the correction term for the alternating magnetic field barrier. This is a correction term for the electrostatic field barrier. This is a correction term for the magnetoelectric coupling cooperative barrier. Boltzmann's constant; Thermodynamic temperature; in, , For ice-water interfacial tension, The difference in free energy per unit volume of liquid-solid phase transition; , The magnetic field effect coefficient of the snakehead muscle tissue was determined through calibration experiments. It represents the magnetic flux density. This is the magnetic field frequency correction factor. This refers to the effective volume of the fish's body. , The vacuum permittivity, Let be the relative permittivity of water. Where is the relative permittivity of ice. , Electric field strength; , The empirical coefficient of magnetoelectric coupling in blackfish tissue. The angle between the directions of the magnetic field and the electric field. This is a phase transition progress correction index; the coupling effect gradually weakens as the phase transition progresses. The integral of ice crystals is a core state parameter characterizing the progress of the freezing phase transition in the muscle tissue of snakehead fish.

8. The method for controlling the freezing and preservation of black carp based on a magnetoelectric coupling field according to claim 7, characterized in that: In S3, a dynamic model of frozen quality loss in snakehead fish was constructed based on the improved Arrhenius equation, with juice loss and protein denaturation as the core quality indicators. The expression for the quality loss rate is as follows: ； In the formula, This represents the relative quality retention rate, with an initial value of 1. Pre-exponential factors; The apparent activation energy for quality deterioration; It is the gas constant; , These are the quality retention factors under a single magnetic field and a single electric field, respectively, with values ​​ranging from (0, 1]. As the magnetoelectric coupling quality synergy factor, satisfying < This demonstrates the additional suppression effect of the coupled field on quality degradation; With the goal of minimizing overall quality loss and total energy consumption as the multi-objective optimization objectives, the optimal freezing target curve of the blackfish's center temperature over time was obtained.

9. The method for controlling the freezing and preservation of black carp based on a magnetoelectric coupling field according to claim 8, characterized in that: In S4, the center temperature, surface temperature, bioimpedance, and ultrasonic echo signals of the snakehead fish are collected in real time. After filtering and preprocessing, the extended Kalman filter algorithm is used to fuse the multi-source data and estimate the ice crystal integral number at the current moment. Average ice crystal size With phase transition rate ; Among them, the ice crystal integral number Impedance amplitude calculation based on characteristic frequency: ； In the formula, This represents the muscle impedance amplitude at the current characteristic frequency of 100kHz. The reference impedance amplitude is the value under the unfrozen condition at 0°C. , All are calibration coefficients specific to blackfish, meeting the requirements. = hour =0 boundary condition; Based on the ultrasonic backscattering method, combined with the calculated ice crystal integral number Multi-source fusion calculations were performed to obtain the average ice crystal size. The formula is as follows: ； In the formula, This is the particle size calibration constant, determined through experimental calibration using standard particle size samples. The ultrasonic scattering correction coefficient for snakehead muscle tissue was obtained by fitting the snakehead frozen calibration experiment. The integral backscattering coefficient, , The power spectral density of the backscattered signal. and These are the upper and lower limits of the effective working bandwidth of the ultrasonic probe, respectively. Based on the measured ice crystal integral number The phase transition rate was obtained from the time series using sliding window differencing and smoothing filtering. Observations: ； In the formula, The sampling interval is denoted as .

10. The method for controlling the freezing and preservation of black carp based on a magnetoelectric coupling field according to claim 9, characterized in that: In S5, a rolling time-domain model predictive control is adopted, and the objective function is optimized as follows: ； The constraints include: Magnetic induction intensity constraint: ; Electric field strength constraint: ; Cooling power constraints: ; Cooling rate constraint: ; In the formula, To predict the time domain, To control the time domain; The predicted core temperature of the fish. The optimal freezing target temperature; , , These are the control increments for magnetic induction intensity, electric field intensity, and cooling power, respectively. , , , All are weighting coefficients. For the current discrete control moment, Indexing for future time steps; , These represent the minimum and maximum limits of magnetic flux density, respectively. , These represent the minimum and maximum limits of the electric field strength, respectively. This is the rated maximum power of the refrigeration system. Temperature at the center of the fish's body The maximum allowable cooling rate at the center of the fish's body.

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