Trace enhancer spraying film closed-loop control method based on multi-source feedback

Abstract

The present application belongs to the technical field of multivariable control, and particularly relates to a trace synergist spraying film forming closed loop control method based on multi-source feedback, comprising: acquiring the initial temperature and micro-environment parameters of a substrate before entering a spraying area in real time; constructing a micro-environment evaporation potential energy index according to the environmental parameters; constructing an interface phase change coupling impedance in combination with the thermal response parameters of the substrate; calculating impedance deviation, and determining the atomizing air pressure correction amount and the medicine liquid preheating temperature correction amount respectively based on the deviation and the micro-environment evaporation potential energy index; and superimposing the correction amounts to the basic set value to drive the air path and the medicine liquid preheating control unit. The environment self-adaptive double variable compensation mechanism established by the present application can quantify the liquid film micro-wetting state, dynamically adjust the kinetic energy and internal energy of the liquid drops, effectively inhibit flashing and sagging, and improve the effective adhesion rate of the synergist.

Description

Technical Field

[0001] This invention relates to the field of multivariable control technology. More specifically, this invention relates to a closed-loop control method for trace synergist spraying film formation based on multi-source feedback. Background Technology

[0002] To improve the agronomic utilization rate of fertilizers, it is usually necessary to uniformly coat the surface of compound fertilizer granules with highly active trace synergists such as polyglutamic acid and amino acids. This process is a typical microfilm construction process, and its core difficulty lies in the extremely low amount of synergist used, typically only 0.5% to 1% of the fertilizer mass. In actual industrial production, fertilizer granules that have just finished the granulation process usually carry unstable residual heat, while the spraying chamber is filled with acidic mist and dust. At the same time, the microenvironment parameters fluctuate drastically with seasonal changes and the operation of the workshop ventilation system, posing challenges to the quality control of trace liquid film formation.

[0003] Currently, the mainstream spraying control technology in the industry mainly relies on mass flow meters for open-loop control or single-loop closed-loop control based on pipeline pressure. Although this traditional control method can accurately ensure that the synergist is sprayed from the nozzle at a predetermined dosage, it has a significant physical blind spot. That is, it can only control the spray volume but cannot sense the actual film-forming state of the synergist at the moment of contact with the matrix. Due to the lack of a feedback mechanism for the microscopic physical processes of the spraying interface, the system cannot determine whether the droplets form a uniform film when they reach the particle surface or whether they are lost due to phase change caused by environmental interference. As a result, it is difficult to guarantee the effective adhesion rate and coating uniformity of the final product.

[0004] Specifically, when the evaporation potential energy of the spraying environment is too high or the residual heat of the matrix is ​​strong, micron-sized atomized droplets are prone to flash evaporation when they come into contact with high-temperature particles. The solvent vaporizes instantly within milliseconds, causing the solute to precipitate in powder form and failing to form a continuous coating film. Conversely, when the particle temperature is low or the droplet kinetic energy is insufficient, the droplets are prone to producing a Leidenfrost-like phenomenon, rolling on the particle surface in a spherical shape and falling off, causing serious sagging and material waste.

[0005] Therefore, there is an urgent need for a closed-loop control method for trace synergist spraying film formation based on multi-source feedback. Summary of the Invention

[0006] To address the technical problem of existing technologies failing to detect film-forming states under complex environments, leading to flash evaporation or sagging of synergists and low adhesion rates, this invention provides a closed-loop control method for trace synergist spraying film formation based on multi-source feedback, comprising:

[0007] The system acquires in real-time the initial temperature of the substrate before entering the spraying zone, the transient response temperature after spraying, the relative humidity of the spraying environment, the atomized airflow velocity, and the instantaneous mass flow rate of the fertilizer particles. Based on the initial temperature, relative humidity, and atomized airflow velocity, a microenvironmental evaporation potential energy index characterizing the driving capacity of environmental evaporation is constructed. Based on the microenvironmental evaporation potential energy index, instantaneous mass flow rate, initial temperature, and transient response temperature, an interfacial phase change coupling impedance characterizing the wetting and spreading state of the liquid film on the substrate surface is constructed. The impedance deviation between the interfacial phase change coupling impedance and the standard impedance value under standard film-forming conditions is calculated. Based on the impedance deviation and the microenvironmental evaporation potential energy index, the atomized air pressure correction and the liquid preheating temperature correction are determined respectively. The atomized air pressure correction is superimposed on the basic set pressure to drive the air path adjustment unit, and the liquid preheating temperature correction is superimposed on the basic set temperature to drive the liquid preheating control unit.

[0008] This invention constructs a microenvironment evaporation potential energy index and an interface phase change coupling impedance in real time, deeply coupling the external environment's ability to extract moisture from the liquid film with the actual thermal response energy flow on the matrix surface. This quantifies the microscopic wetting and spreading state of micron-sized droplets upon contact with the matrix, overcoming the physical blind spot of traditional flow or pressure control that cannot perceive the actual film quality. Furthermore, this invention utilizes impedance deviation combined with the microenvironment evaporation potential energy index to establish an environmentally adaptive bivariate collaborative compensation mechanism. By dynamically adjusting the atomizing air pressure and the preheating temperature of the drug solution, it achieves a physical balance between droplet impact kinetic energy and fluid internal energy. This allows the system to actively suppress powder precipitation caused by solvent flash evaporation and spherical dripping caused by insufficient kinetic energy when facing high evaporation potential energy or matrix residual heat fluctuations. This ensures that trace amounts of synergist remain within the optimal phase change film range under complex conditions, improving coating uniformity and effective adhesion.

[0009] Preferably, the microenvironment evaporation potential energy index satisfies the expression: In the formula, This represents the evaporative potential energy index of the microenvironment; Indicates the initial temperature of the matrix; Indicates the initial temperature of the substrate before it enters the spraying area. The solvent saturated vapor pressure at the specified value; Indicates standard atmospheric pressure; Indicates the velocity of the atomized airflow; It is the boundary layer thinning factor, which characterizes the destructive effect of high-speed atomized airflow on the surface gas film; This indicates relative humidity.

[0010] This invention constructs a microenvironment evaporation potential energy index, which comprehensively considers the solvent saturated vapor pressure determined by the initial temperature of the matrix, the boundary layer disruption effect caused by the atomized gas flow velocity, and the vapor pressure deficit caused by the relative humidity of the environment. It quantifies the complex and ever-changing environmental thermodynamic interference factors into a single evaluation index. This index can characterize the ultimate ability of the environment to plunder water from the droplet surface under the current operating conditions, thereby providing an accurate feedforward signal for the subsequent control system. It can effectively predict and avoid flash evaporation of the drug solution caused by excessive environmental evaporation driving force or incomplete film drying caused by insufficient driving force, thus improving the system's adaptability to extreme environments.

[0011] Preferably, the method for obtaining the boundary layer thinning factor is as follows: under a standard laboratory environment, the morphological evolution of a standard droplet in a continuously changing horizontal airflow is recorded, the oscillation frequency spectrum of the droplet surface is extracted, the characteristic frequency at which the droplet undergoes its first microscopic breakage or atomization plume separation is defined as the stability threshold, the corresponding critical airflow velocity is recorded, and the boundary layer thinning factor is set as the product of the reciprocal of the critical airflow velocity and the shape correction coefficient.

[0012] Preferably, the method for obtaining the shape correction coefficient is as follows: select several droplet samples with a clear field of view, extract the major axis and minor axis of each droplet sample, take the average ratio of the major and minor axes of all droplet samples as the average deformation rate, and obtain the shape correction coefficient based on the average deformation rate. ,in Indicates the shape correction factor. This represents the average deformation rate.

[0013] Preferably, the interface phase change coupling impedance satisfies the expression: In the formula, Indicates the interface phase transition coupling impedance; This represents the evaporative potential energy index of the microenvironment; This indicates the instantaneous mass flow rate of fertilizer granules; This indicates the specific heat capacity of the current fertilizer variety; This indicates the initial temperature of the substrate before it enters the spraying area; Indicates the transient response temperature after substrate spraying; This represents the standard heat exchange power reference value under reference operating conditions; Represents an exponential function with the natural constant as its base; Indicates the activation energy of viscous flow; Represents the gas constant; This is a bias constant used to prevent the denominator from being zero.

[0014] This invention utilizes the ratio of the evaporation potential energy of the microenvironment to the actual thermal response energy flow of the matrix, and introduces viscous flow activation energy to correct the temperature sensitivity of fluid viscosity. This eliminates the nonlinear interference of material flow fluctuations and matrix temperature changes on heat exchange calculations, enabling the calculated interfacial phase change coupling impedance to objectively reflect the wetting and spreading state of the synergist liquid film at the micro-interface. This allows the control system to still keenly detect the critical state of flash evaporation or sagging even when the production load fluctuates significantly or the thermal properties of the matrix change, thus achieving an essential perception of film formation quality.

[0015] Preferably, the method for obtaining the viscous flow activation energy is as follows: the viscosity of the synergist at different temperatures is measured by a rotational rheometer, an Arrhenius curve is plotted, and the slope of the Arrhenius curve is taken as the viscous flow activation energy.

[0016] Preferably, the atomizing air pressure correction amount satisfies the expression: In the formula, Indicates the correction amount for atomized air pressure; Indicates the pressure response gain coefficient; Represents a symbolic function; Indicates the interface phase transition coupling impedance; This represents the standard impedance value under standard film-forming conditions. This represents the natural logarithm function.

[0017] This invention employs nonlinear adjustment logic incorporating a natural logarithmic function to calculate the atomized air pressure correction. This strategy fully adapts to the exponential energy conversion law between air pressure work and droplet fragmentation size in aerodynamics. When the impedance deviation is small, the logarithmic logic is approximately linear, ensuring the system's high sensitivity response. However, when the impedance deviation is large, the logarithmic logic can automatically and smoothly adjust the gain, forming soft saturation control characteristics. This effectively prevents excessive pressure adjustment commands caused by linear error amplification, thereby avoiding overshoot oscillations and flow field disturbances in the air path system and ensuring the supply of kinetic energy for droplet fragmentation.

[0018] Preferably, the correction amount for the preheating temperature of the medicinal solution satisfies the expression: In the formula, This indicates the correction amount for the preheating temperature of the medicine solution; Indicates the temperature response gain coefficient; It is a function with maximum value. This represents the current microenvironment evaporation potential energy index. This represents the standard microenvironment evaporative potential energy index under reference operating conditions; Indicates the interface phase transition coupling impedance; This represents the standard impedance value under standard film-forming conditions.

[0019] This invention introduces an environmental adaptive gain weighting mechanism when calculating the correction amount for the preheating temperature of the drug solution. By using the ratio of the microenvironmental evaporation potential energy index to the standard microenvironmental evaporation potential energy index under reference conditions as the adjustment coefficient, the temperature control loop can automatically adjust the compensation intensity according to the dryness or humidity of the current weather. When the environmental evaporation driving force is too strong, the system will automatically increase the adjustment range of the drug solution cooling to counteract the risk of flash evaporation by rapidly reducing the internal energy of the fluid. When the environment is mild, the system maintains the basic adjustment gain to prevent the drug solution viscosity from increasing sharply due to over-adjustment. This improves the robustness of the system against complex environmental thermal disturbances and ensures the effective adhesion of trace synergists.

[0020] Preferably, the method for obtaining the basic set pressure is as follows: under standard atmospheric pressure and room temperature of 25 degrees Celsius, the atomization field is monitored using a laser particle size analyzer, and the spraying pressure is adjusted until the Sotter average particle size of the droplets matches the average micropore size on the surface of the fertilizer particles. The pressure value at this time is recorded as the basic set pressure. The method for obtaining the basic set temperature is as follows: the viscosity-temperature characteristic curve of the synergist is measured, and the rheological inflection point temperature at which the fluid viscosity changes gradually with temperature is selected as the basic set temperature.

[0021] Preferably, it further includes: in response to the final pressure control command of the air path regulating unit exceeding the safety threshold, or the instantaneous mass flow rate of the fertilizer granules dropping to zero, forcibly resetting the atomizing air pressure correction amount and the liquid preheating temperature correction amount to zero and triggering an alarm.

[0022] The beneficial effects of this invention are as follows: By constructing the microenvironmental evaporation potential energy index and the interface phase change coupling impedance in real time, this invention deeply couples the external environment's ability to extract moisture from the liquid film with the actual thermal response energy flow on the matrix surface, thereby quantifying the microscopic wetting and spreading state of micron-sized droplets at the moment of contact with the matrix, breaking through the physical blind spot of traditional flow or pressure control that cannot perceive the actual film quality; This invention utilizes the impedance deviation combined with the microenvironmental evaporation potential energy index to establish an environmentally adaptive bivariate collaborative compensation mechanism. By dynamically adjusting the atomizing air pressure and the preheating temperature of the liquid, it achieves the ratio of droplet impact kinetic energy to fluid internal energy at the physical level. This allows the system to actively suppress powder precipitation caused by solvent flash evaporation and spherical dripping caused by insufficient kinetic energy when facing high evaporation potential energy or matrix residual heat fluctuations, ensuring that trace synergists are always maintained in the optimal phase change film range under complex working conditions, improving the uniformity of coating and effective adhesion rate. Attached Figure Description

[0023] Figure 1 This is a flowchart illustrating the closed-loop control method for trace synergist spraying film formation based on multi-source feedback in this invention.

[0024] Figure 2This is a schematic diagram showing the initial temperature of the substrate before it enters the spraying zone and the instantaneous mass flow rate changes of the fertilizer particles.

[0025] Figure 3 This is a schematic diagram showing the change of the microenvironment evaporation potential energy index over time.

[0026] Figure 4 This diagram illustrates the changes in the correction amounts for atomizing air pressure and liquid preheating temperature.

[0027] Figure 5 This is a schematic diagram comparing the interface phase change coupling impedance in the open-loop state of the prior art and the closed-loop control state of the present invention in an embodiment of the present invention. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0030] This invention discloses a closed-loop control method for trace synergist spraying film formation based on multi-source feedback, referring to... Figure 1 This includes steps S1 to S5:

[0031] S1. Real-time acquisition of the initial temperature of the substrate before entering the spraying area, the transient response temperature after spraying, the relative humidity of the spraying environment, the atomized airflow velocity, and the instantaneous mass flow rate of fertilizer particles.

[0032] Specifically, high-frequency infrared fiber optic temperature probes with air purging protective sleeves are deployed at the material inlet and outlet of the spraying chamber to collect the initial temperature of the matrix before it enters the spraying area and the transient response temperature after spraying; relative humidity and atomized airflow velocity are collected using a micro-environment sensor group deployed inside the spraying chamber; the instantaneous mass flow rate of fertilizer granules is obtained in real time through an electronic belt scale on the production line; and the specific heat capacity of the current fertilizer variety is retrieved from a pre-set material property database.

[0033] For example, Figure 2 This is a schematic diagram showing the initial temperature of the substrate before it enters the spraying zone and the instantaneous mass flow rate changes of the fertilizer particles.

[0034] S2. Based on the initial temperature, relative humidity, and atomized airflow velocity, construct a microenvironment evaporation potential energy index that characterizes the driving force of environmental evaporation.

[0035] It should be noted that environmental fluctuations can cause drastic changes in the evaporation rate of water on the liquid film surface. If this is not quantitatively monitored, it will directly lead to uncontrollable film quality. Therefore, in order to quantitatively assess the risk of drying out of the liquid film, this invention uses the microenvironment evaporation potential energy index to characterize the ultimate potential energy of the environment to plunder water from the liquid film surface and remove latent heat, which is the theoretical maximum evaporation driving capacity under the current environment.

[0036] Specifically, the microenvironment evaporation potential energy index satisfies the expression:

[0037]

[0038] In the formula, This represents the evaporation potential energy index of the microenvironment. The larger the value, the stronger the tendency of the environment to cause droplet flash evaporation or rapid drying. Indicates the initial temperature of the matrix; Indicates the initial temperature of the substrate before it enters the spraying area. The saturated vapor pressure of the solvent at that point is calculated using the Magnus empirical formula. Indicates standard atmospheric pressure, used to measure the initial temperature of the substrate before it enters the spraying zone. Solvent saturated vapor pressure Perform normalization processing; Indicates the velocity of the atomized airflow; It is the boundary layer thinning factor, which characterizes the destructive effect of high-speed atomized airflow on the surface gas film; Indicates relative humidity; This reflects the accelerating effect of airflow on the mass transfer process. The faster the airflow speed, the thinner the boundary layer, the faster the evaporation, and the greater the microenvironment evaporation potential energy index. This reflects the vapor pressure deficit; the drier the environment, the greater the deficit, the stronger the evaporation driving force, and the greater the microenvironment evaporation potential energy index; solvent saturated vapor pressure This directly limits the physical upper limit of the evaporation driving potential. According to the Magnus empirical formula, when When the pressure increases, the saturated vapor pressure of the solvent... It grows exponentially, which in turn leads to the microenvironment evaporation potential energy index A significant increase indicates that the liquid film faces an extremely high risk of flash evaporation upon contact with the high-temperature substrate, while a decrease indicates a risk of sagging.

[0039] In the formula, the boundary layer thinning factor The acquisition method is as follows: Under a standard laboratory environment, a high-speed camera is used to record the morphological evolution of standard droplets in a continuously changing horizontal airflow at a frame rate of no less than 5000 frames per second. The oscillation frequency spectrum of the droplet surface is extracted. The characteristic frequency at which the droplet undergoes its first microscopic breakup or atomization plume separation is defined as the stability threshold, and the corresponding critical airflow velocity is recorded. and will Set as The product of the reciprocal of the shape correction factor and the shape correction factor can be used in other embodiments. Alternatively, the implementer can directly set the stability threshold by consulting a fluid dynamics manual based on the surface tension characteristics of the synergist. The shape correction factor is a dimensionless parameter used to correct for changes in mass transfer rate caused by non-spherical distortion (such as ellipsoidal or dumbbell-shaped) of droplets under high-speed airflow shear. The reason for introducing the shape correction factor is that droplets are not ideal spheres during actual spraying. Airflow shear can cause droplet stretching or interfacial oscillation, significantly increasing the specific surface area of ​​gas-liquid contact and disrupting the surface saturated gas film, thus making the actual evaporation rate higher than the theoretically calculated value. The specific method for obtaining this shape correction factor is as follows: using the droplet morphology evolution images recorded by the high-speed camera in the above steps, select several droplet samples with clear fields of view, extract the major and minor axes of each droplet sample, and take the average of the ratios of the major and minor axes of all droplet samples as the average deformation rate. Combined with the fluid rheological properties of the synergist, this is determined using an empirical formula. Obtain the shape correction factor, where Indicates the shape correction factor. The average deformation rate is represented by this empirical formula, which is an equivalent mass transfer area correction model derived from Thomsen's approximation of the ellipsoidal surface area. The exponent 1.6 is a characteristic constant in fluid mechanics used to characterize the surface area change of non-spherical particles, derived from the engineering value of Thomsen's constant 1.6075. This empirical formula expresses the average deformation rate... The surface area increment ratio is mapped to a three-dimensional space, thereby quantifying the evaporation interface expansion effect caused by droplet morphology distortion.

[0040] For example, Figure 3 This is a schematic diagram showing the change of the microenvironment evaporation potential energy index over time.

[0041] S3. Based on the microenvironment evaporation potential energy index, instantaneous mass flow rate, initial temperature, and transient response temperature, construct the interfacial phase transition coupling impedance to characterize the wetting and spreading state of the liquid film on the matrix surface.

[0042] It should be noted that the microenvironment evaporation potential energy index represents the driving force of the environment and does not reflect the actual spreading of the droplets on the substrate surface. If the microenvironment evaporation potential energy index is large, but the temperature drop of the substrate surface is small, it indicates that the droplets may have rolled off in a spherical shape or vaporized instantaneously without effective sensible heat exchange, which means that the wettability is extremely poor. Therefore, this invention introduces the interfacial phase change coupling impedance and uses the ratio of the microenvironment evaporation potential energy index to the actual thermal response energy flow of the substrate to quantify the wetting and spreading state of the liquid film at the micro-interface.

[0043] Specifically, the interface phase change coupling impedance satisfies the following expression:

[0044]

[0045] In the formula, Indicates the interface phase transition coupling impedance; This represents the evaporative potential energy index of the microenvironment; This indicates the instantaneous mass flow rate of fertilizer granules; This indicates the specific heat capacity of the current fertilizer variety; This indicates the initial temperature of the substrate before it enters the spraying area; Indicates the transient response temperature after substrate spraying; This represents the standard heat exchange power reference value under reference operating conditions, used to measure the energy flow in the denominator. Normalization is performed to reduce the interfacial phase transition coupling impedance. To become a dimensionless indicator It is calculated based on the product of the mass flow rate and the standard temperature drop under the system's rated operating conditions; Represents an exponential function with the natural constant as its base; The bias constant used to prevent the denominator from being zero is a very small positive real number. In this embodiment, it is... Set as In other embodiments, implementers may set the appropriate parameters according to the actual implementation situation. ; The activation energy of viscous flow is represented by the following method: measuring the viscosity of the synergist at different temperatures using a rotational rheometer, plotting an Arrhenius curve, and taking the slope of the Arrhenius curve as the activation energy of viscous flow. , The value ranges from 15 kJ / mol to 25 kJ / mol; This represents the gas constant.

[0046] In the formula, This reflects the actual heat energy flow absorbed by the normalized matrix. The smaller this value, the higher the microenvironment evaporation potential index. When the value is larger, the interface phase change coupling impedance is higher. The value increases significantly, indicating that the actual heat exchange is weak under strong evaporation and the droplets do not spread effectively. Used to correct the effect of the initial temperature of the matrix before it enters the spraying zone on the viscosity of the synergist itself. The higher the viscosity, the lower the theoretical viscosity of the fluid. The smaller the value, the better it offsets the interference of the increased spreading caused by the decrease in viscosity on the impedance calculation, thus reducing the interfacial phase change coupling impedance. It purely reflects the wetting state of the interface.

[0047] It should be noted that the standard temperature drop refers to the empirical temperature difference generated before and after the substrate passes through the spraying area under ideal conditions where the system is in rated operating conditions and the film quality is optimal. The method for obtaining it is as follows: several historical production batches that have reached the optimal standard in terms of film uniformity and stability are screened out through offline detection, and the arithmetic mean of the measured difference between the substrate inlet temperature and outlet temperature during the stable operation of these batches is extracted and finally calibrated as the standard temperature drop.

[0048] S4. Calculate the impedance deviation between the interface phase change coupling impedance and the standard impedance value under the standard film-forming state, and determine the atomizing air pressure correction amount and the drug liquid preheating temperature correction amount based on the impedance deviation amount and the microenvironment evaporation potential energy index, respectively.

[0049] It should be noted that in order to maintain the interfacial phase change coupling impedance within the ideal film-forming range, it is necessary to simultaneously adjust the mechanical dispersing force and the fluid internal energy. Adjusting a single variable is difficult to suppress flashing and agglomeration at the same time. Increasing the pressure can increase the spreading kinetic energy, but it may also exacerbate the evaporation of fine droplets. Decreasing the temperature can resist flashing, but it may lead to excessive viscosity and agglomeration. Therefore, this invention constructs a dual-variable compensation control strategy, which uses the deviation of thermodynamic impedance to simultaneously and inversely adjust the atomization pressure and the drug temperature.

[0050] Specifically, the atomized air pressure correction satisfies the expression:

[0051]

[0052] The correction amount for the preheating temperature of the liquid medicine satisfies the expression:

[0053]

[0054] In the formula, Indicates the correction amount for atomized air pressure; This represents the pressure response gain coefficient, and its unit is kilopascal. Represents a symbolic function; Indicates the interface phase transition coupling impedance; This represents the standard impedance value under standard film-forming conditions. This value was determined through offline calibration experiments, taking the interface phase transition coupling impedance from the historically best production batch. The median of the values; Represent the natural logarithm function; This represents the absolute value of the impedance deviation. The term embodies logarithmic nonlinear control logic. When the absolute value of the impedance deviation is small, the term changes approximately linearly, and the system responds quickly to small fluctuations. When the absolute value of the impedance deviation is large, the growth rate of the term slows down to prevent the pressure regulation from increasing dramatically due to the excessive absolute value of the impedance deviation, which would disrupt the stability of the flow field. This is to match the energy dissipation characteristics of droplet breakup at the physical level. This indicates the correction amount for the preheating temperature of the medicine solution; This represents the temperature response gain coefficient, and its unit is degrees Celsius. Indicates the environment adaptive gain weight. It is a function with maximum value. This represents the current microenvironment evaporation potential energy index. The standard microenvironment evaporation potential energy index under reference operating conditions is obtained as follows: Through offline data analysis, several historical production batches that achieved optimal film uniformity and effective adhesion rate were selected. The baseline evaporation potential energy index corresponding to each optimal production batch was calculated. The arithmetic mean of the baseline evaporation potential energy indices corresponding to all optimal production batches was defined as the standard microenvironment evaporation potential energy index under reference operating conditions. When the interface phase transition coupling impedance Greater than the standard impedance value under standard film formation conditions hour, The function outputs a positive value. To achieve a positive value, the system increases the atomization pressure, giving the droplets higher impact kinetic energy to force them to spread out. If the value is negative, the system lowers the temperature of the liquid drug, reduces the internal energy of the droplets to prevent flash evaporation, and This ensures that even in low evaporation potential environments, the temperature regulation gain will not be too low, ensuring that the system has basic regulation capabilities.

[0055] It should be noted that the pressure response gain coefficient The acquisition process is as follows: During the offline calibration phase of the system, the preheating temperature of the drug solution is kept constant, a step pressure signal is applied to the proportional valve of the gas circuit, and the interface phase change coupling impedance is recorded. The time-domain response curve is obtained, and the lag time and rise time of the impedance response are extracted. Based on the Ziegler-Nichols tuning rule, the critical gain of the system is calculated. Considering the mechanical inertia of the gas path adjustment and the delay characteristics of the flow field establishment, the critical gain is multiplied by a preset damping coefficient to determine the critical gain. In this embodiment, the damping coefficient is set to 0.8, which aims to force the control loop to operate in the critical damping region, thereby eliminating overshoot oscillations caused by physical hysteresis of the gas path while retaining the ability to quickly track sudden thermal disturbances.

[0056] Temperature response gain coefficient The acquisition process is as follows: Under constant standard atomization pressure, a series of drug solution preheating temperatures are set. After the heating system reaches thermal equilibrium, the interfacial phase change coupling impedance value corresponding to each temperature point is recorded. A curve of the interfacial phase change coupling impedance value changing with the drug solution temperature is constructed. The linear working region of the curve is fitted using the least squares method, and the absolute value of the slope of the fitted straight line is extracted as the temperature response gain coefficient. .

[0057] For example, Figure 4 The diagram shows the changes in atomizing air pressure correction and liquid preheating temperature correction. It can be seen that the atomizing air pressure correction curve and the liquid preheating temperature correction curve exhibit an inverse linkage characteristic. When one curve is adjusted upward, the other curve is adjusted downward, and the adjustment range shows differentiated gain characteristics with the change of environmental potential energy, which verifies the multi-dimensional collaborative compensation logic of the system under different impedance deviations.

[0058] S5. The atomizing air pressure correction amount is added to the basic set pressure to drive the air path adjustment unit, and the liquid preheating temperature correction amount is added to the basic set temperature to drive the liquid preheating control unit.

[0059] Specifically, the atomized air pressure correction amount The pressure is superimposed on the baseline setting pressure to generate a final pressure control command, which is sent to the electro-proportional valve in the air circuit to adjust the atomizing air pressure; the preheating temperature correction amount of the drug solution is also adjusted. The temperature is superimposed on the baseline set temperature to generate a final temperature command, which is sent to the online induction heater in the liquid circuit to adjust the liquid temperature. Simultaneously, the system performs a safety interlock check; if the final pressure control command exceeds the safety threshold or the instantaneous mass flow rate of the fertilizer granules... If the pressure drops to zero, the atomizing air pressure correction will be forcibly reset. Correction amount for preheating temperature of the medicine solution The value is zero and an alarm is triggered.

[0060] It should be further explained that the baseline setting pressure and baseline setting temperature are the reference operating points of the system under standard steady-state conditions. The baseline setting pressure is obtained by monitoring the atomization field using a laser particle size analyzer under standard atmospheric pressure and a room temperature of 25 degrees Celsius, adjusting the spraying pressure until the Sotter average particle size of the droplets matches the average micropore size of the fertilizer granules, and recording the pressure value at this point as the baseline setting pressure. The baseline setting temperature is obtained by measuring the viscosity-temperature characteristic curve of the synergist, selecting the rheological inflection point temperature at which the fluid viscosity begins to level off with temperature and no longer decreases significantly as the baseline setting temperature, to ensure optimal basic fluidity with minimal energy consumption. The safety threshold is obtained by obtaining the design pressure resistance limit of the gas pipeline and the upper limit of the linear adjustment range of the electro-proportional valve, and taking 85% to 90% of the smaller of the two as the safety threshold for pressure. This ensures the physical safety of the equipment while preventing control commands from entering the nonlinear saturation region of the actuator, which could lead to control failure. In this embodiment, 90% of the smaller of the design pressure resistance limit of the gas pipeline and the upper limit of the linear adjustment range of the electro-proportional valve is used.

[0061] For example, Figure 5 This is a schematic diagram comparing the interface phase change coupling impedance in the open-loop state of the prior art and the closed-loop control state of the present invention in an embodiment of the present invention. It can be seen that in the open-loop state of the prior art, the interface phase change coupling impedance curve fluctuates violently and deviates significantly from the ideal baseline, with its high value range corresponding to flash evaporation or poor wetting. However, under the dual-variable closed-loop control of the present invention, the interface phase change coupling impedance curve closely follows the ideal baseline, indicating that even under harsh environmental conditions, the system can still maintain the film formation state within the optimal wetting range.

Claims

1. A closed-loop control method for trace synergist spraying film formation based on multi-source feedback, characterized in that, include: The system can acquire in real time the initial temperature of the substrate before it enters the spraying area, the transient response temperature after spraying, the relative humidity of the spraying environment, the atomized airflow velocity, and the instantaneous mass flow rate of fertilizer particles. Based on initial temperature, relative humidity, and atomized airflow velocity, a microenvironment evaporation potential energy index characterizing the driving force of environmental evaporation is constructed. ,satisfy: ； Indicates the initial temperature of the matrix; Indicates the initial temperature of the substrate before it enters the spraying area. The solvent saturated vapor pressure at the specified value; Indicates standard atmospheric pressure; Indicates the velocity of the atomized airflow; It is the boundary layer thinning factor, which characterizes the destructive effect of high-speed atomized airflow on the surface gas film; Indicates relative humidity; Based on the microenvironment evaporation potential energy index, instantaneous mass flow rate, initial temperature, and transient response temperature, an interfacial phase transition coupling impedance characterizing the wetting and spreading state of the liquid film on the matrix surface is constructed. ,satisfy: ； This indicates the instantaneous mass flow rate of fertilizer granules; This indicates the specific heat capacity of the current fertilizer variety; Indicates the transient response temperature after substrate spraying; This represents the standard heat exchange power reference value under reference operating conditions; Represents an exponential function with the natural constant as its base; Indicates the activation energy of viscous flow; Represents the gas constant; This is a bias constant used to prevent the denominator from being zero; The impedance deviation between the interfacial phase change coupling impedance and the standard impedance value under standard film formation conditions is calculated. Based on the impedance deviation and the microenvironment evaporation potential energy index, the correction amount of atomizing air pressure and the correction amount of drug solution preheating temperature are determined respectively. The atomizing air pressure correction is added to the base setting pressure to drive the air path adjustment unit, and the liquid preheating temperature correction is added to the base setting temperature to drive the liquid preheating control unit.

2. The closed-loop control method for trace synergist spraying film formation based on multi-source feedback as described in claim 1, characterized in that, The method for obtaining the boundary layer thinning factor is as follows: In a standard laboratory environment, the morphological evolution of standard droplets in a continuously changing horizontal airflow is recorded, the oscillation frequency spectrum of the droplet surface is extracted, the characteristic frequency at which the droplet first undergoes microscopic breakage or atomization plume separation is defined as the stability threshold, the corresponding critical airflow velocity is recorded, and the boundary layer thinning factor is set as the product of the reciprocal of the critical airflow velocity and the shape correction coefficient.

3. The closed-loop control method for trace synergist spraying film formation based on multi-source feedback according to claim 2, characterized in that, The method for obtaining the shape correction coefficient is as follows: Select several droplet samples with clear field of view, extract the major and minor axes of each droplet sample, and take the average ratio of the major and minor axes of all droplet samples as the average deformation rate. Obtain the shape correction coefficient based on the average deformation rate. ,in Indicates the shape correction factor. This represents the average deformation rate.

4. The closed-loop control method for trace synergist spraying film formation based on multi-source feedback as described in claim 1, characterized in that, The method for obtaining the viscous flow activation energy is as follows: The viscosity of the synergist at different temperatures was measured using a rotational rheometer, and Arrhenius curves were plotted. The slope of the Arrhenius curves was used as the activation energy for viscous flow.

5. The closed-loop control method for trace synergist spraying film formation based on multi-source feedback according to claim 1, characterized in that, The atomized air pressure correction amount satisfies the expression: ； In the formula, Indicates the correction amount for atomized air pressure; Indicates the pressure response gain coefficient; Represents a symbolic function; Indicates the interface phase transition coupling impedance; This represents the standard impedance value under standard film-forming conditions. This represents the natural logarithm function.

6. The closed-loop control method for trace synergist spraying film formation based on multi-source feedback according to claim 1, characterized in that, The correction amount for the preheating temperature of the drug solution satisfies the following expression: ； In the formula, This indicates the correction amount for the preheating temperature of the medicine solution; Indicates the temperature response gain coefficient; It is a function with maximum value. This represents the current microenvironment evaporation potential energy index. This represents the standard microenvironment evaporative potential energy index under reference operating conditions; Indicates the interface phase transition coupling impedance; This represents the standard impedance value under standard film-forming conditions.

7. The closed-loop control method for trace synergist spraying film formation based on multi-source feedback according to claim 1, characterized in that, The method for obtaining the basic setting pressure is as follows: Under standard atmospheric pressure and room temperature of 25 degrees Celsius, the atomization field is monitored using a laser particle size analyzer, and the spraying pressure is adjusted until the average particle size of the droplets matches the average micropore size of the fertilizer particles. The pressure value at this time is recorded as the basic setting pressure. The method for obtaining the basic set temperature is as follows: measure the viscosity-temperature characteristic curve of the synergist, and select the rheological inflection point temperature when the fluid viscosity changes gradually with temperature as the basic set temperature.

8. The closed-loop control method for trace synergist spraying film formation based on multi-source feedback according to claim 1, characterized in that, Also includes: If the final pressure control command of the air circuit regulating unit exceeds the safety threshold, or the instantaneous mass flow rate of the fertilizer granules drops to zero, the atomizing air pressure correction and the liquid preheating temperature correction will be forcibly reset to zero and an alarm will be triggered.

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