Medicament liquid level balance control system in vacuum infiltration production line

Abstract

The invention relates to the technical field of vacuum infiltration adjustment, and discloses a medicament liquid level balance control system in a vacuum infiltration production line, which comprises a differential pressure type liquid level detection unit, a medicament supplementing unit and a control module, and determining the real-time operation frequency of the medicament supplementing unit so as to calculate the dynamic viscosity parameter of the medicament, determine the phase change resistance data of the gas-liquid mixed phase and the dynamic compensation coefficient corresponding to the liquid level fluctuation lag amount, and adjust the supplementing agent pumping speed. Dynamic decoupling of control logic and fluid physical properties is achieved, apparent liquid level deviation caused by asymmetric movement of gas separation and redissolution rate of a medicament in a variable-pressure environment is effectively eliminated, and accuracy of liquid level adjustment of non-Newtonian fluid and stability of a control loop are improved.

Description

Technical Field

[0001] This invention relates to a reagent level balance control system in a vacuum impregnation production line, belonging to the field of vacuum impregnation regulation technology. Background Technology

[0002] In the current automated manufacturing processes of large automotive castings such as cylinder blocks, cylinder heads, and shock absorber towers, sealing micropores in castings through vacuum impregnation is a necessary means to ensure the airtightness of components. Liquid level regulation in this field mainly relies on a balance control loop between the reagent storage device and the impregnation tank. This involves reciprocating cycles of vacuum pumping, venting, and high-pressure injection to drive the sealing agent into the internal gaps of the workpiece. To maintain production rhythm and ensure complete agent coverage, differential pressure transmitters or ultrasonic sensors are typically used to monitor the liquid level in the reagent tank, and a controller adjusts the output frequency of the replenishment pump to achieve the desired level under fluctuating pressure. To determine the dynamic equilibrium of the liquid level; from a fluid dynamics perspective, the impregnation agent has a high kinematic viscosity and contains a fixed proportion of dissolved air. When the absolute pressure of the system changes drastically between 0.5 kPa and 0.6 MPa, the solubility of the gas inside the agent changes instantaneously with the pressure gradient, causing the agent to exhibit a physical state of gas-liquid mixture. This pressure-induced phase change process alters the equivalent density of the fluid and generates a large amount of foam on the liquid surface, forming an apparent displacement at the physical level. Constrained by the high viscosity of the agent, the expansion and dissolution process of the gas phase exhibits a significant asymmetric hysteresis phenomenon in the time dimension.

[0003] To eliminate such interference, the industry typically employs static damping compensation or adds mechanical flow stabilizers. However, simple static filtering cannot identify the differences in mass transfer kinetics between depressurization / gas release and pressure-boosting / dissolution, leading to phase deviations in the control command during the pressure switching window. The impregnating agent is a typical non-Newtonian fluid, with its dynamic viscosity fluctuating with changes in the shear field. When the controller drives the replenishment pump, the mechanical shear field generated by the impeller reduces the local agent viscosity, thereby disrupting the original gas-liquid mass transfer resistance balance and causing a dynamic shift in the actual bubble dissolution rate with the pump frequency. Existing control methods focus on mechanical structure improvements or static parameter settings, limiting hardware flow stabilization and exhibiting lagging adaptive control logic. For example, Chinese invention patent CN223209831U discloses a liquid level control device for a vacuum impregnation machine. It sets up a lifting mechanism to drive the pallet displacement and change the relative height of the workpiece to adapt to the impregnation requirements. This type of mechanical position compensation technology is based on the assumption that the liquid level measurement value is the true physical value. When processing high-viscosity agents, the system pressure changes drastically, and the precipitation and redissolution of dissolved gas inside the agent have asymmetric hysteresis. Foam is generated on the liquid surface, causing false fluctuations in the apparent liquid level. This solution ignores the phase change interference under fluid pressure variation environment. The mechanical adjustment response rhythm cannot match the changes in rheological properties of non-Newtonian fluids under pumping shear field. In actual production, measurement distortion occurs, causing phase deviation of adjustment commands or system oscillation.

[0004] Therefore, how to construct a regulation mechanism that can identify the asymmetric hysteresis characteristics of fluids and couple the frequency feedback of actuators, and resolve the contradiction between the apparent liquid level noise and measurement distortion generated by the agent during the process of drastic pressure switching, has become the technical problem to be solved by this invention. Summary of the Invention

[0005] To address the problems mentioned in the background art, the technical solution of the present invention is as follows: A reagent level balance control system in a vacuum impregnation production line, comprising:

[0006] Differential pressure level detection unit is used to collect differential pressure signals of liquid level inside the impregnation tank;

[0007] The reagent replenishment unit is used to compensate for reagent backflow during the impregnation process.

[0008] The control module is connected to both the differential pressure level detection unit and the reagent replenishment unit. The control module operates the following logic: Step 101, real-time acquisition of the differential pressure signal and pressure variability data characterizing the instantaneous environmental pressure fluctuation amplitude within the impregnation vessel; Step 102, determination of the real-time operating frequency of the reagent replenishment unit during the compensation process, and calculation of the dynamic viscosity parameters of the reagent under the current pumping shear field based on the real-time operating frequency to characterize the interference of non-Newtonian fluid properties on the liquid surface response characteristics; Step 103, determination of the phase change resistance data of the gas-liquid mixture in the impregnation vessel during the pressure change process using the dynamic viscosity parameters, and determination of the dynamic compensation coefficient corresponding to the liquid level fluctuation hysteresis based on the pressure variability data. The dynamic compensation coefficient is used to perform in-situ correction of the adjustment transfer function within the control module; Step 104, adjustment of the output rotation speed of the reagent replenishment unit based on the differential pressure signal, pressure variability data, and the dynamic compensation coefficient corrected by the transfer function, to eliminate the apparent liquid level detection deviation caused by the asymmetric movement of internal dissolved gas precipitation and re-dissolution rate under pressure change conditions.

[0009] Preferably, when the control module runs step 103, it includes the following sub-steps: Step 1031, using a preset rheological characteristic mapping relationship, establish a monotonic correlation logic between the real-time operating frequency and the phase change resistance data; Step 1032, calculate the fluid hysteresis constant corresponding to the dynamic viscosity parameter through the monotonic correlation logic; Step 1033, map the fluid hysteresis constant to a dynamic compensation coefficient to achieve real-time adjustment of the controller output gain.

[0010] Preferably, the control module satisfies the following quantization logic when calculating the dynamic compensation coefficient: ;in, For dynamic compensation coefficients, This is the shear-thinning sensitivity coefficient of the drug. The real-time operating frequency of the drug replenishment unit. This is a static damping correction term corresponding to the real-time pressure inside the impregnation vessel.

[0011] Preferably, the differential pressure level detection unit includes: a total pressure sensor, located in the liquid phase zone at the bottom of the impregnation vessel; a reference pressure sensor, located in the gas phase space at the top of the impregnation vessel; and a differential pressure calculation module, connected to the total pressure sensor and the reference pressure sensor respectively, for performing differential calculation on the total pressure and gas phase pressure inside the vessel to extract the differential pressure signal of the level.

[0012] Preferably, the system also includes a pressure balancing branch; the two ends of the pressure balancing branch are connected to the impregnation vessel and the reagent storage tank respectively, and a proportional regulating valve is provided on the pressure balancing branch; the control module is also used to adjust the opening of the proportional regulating valve according to the pressure variation data, and when the impregnation vessel is in a depressurized state, the expansion displacement of the reagent under negative pressure is offset in real time by a preset volume compensation model.

[0013] Preferably, the control module is further configured to: set an asymmetric adjustment threshold, the asymmetric adjustment threshold including a first opening threshold for initiating the replenishment action and a second closing threshold for stopping the replenishment action; when the impregnation vessel is in the pressure-boosting and remelting stage, adjust the value of the first opening threshold according to the phase change resistance data to avoid a false drop in liquid level caused by bubble volume compression.

[0014] Preferably, the control module further includes a dynamic prediction unit; the dynamic prediction unit is used to calculate the equilibrium liquid level reference value under the current working condition based on the drainage parameters of the workpiece to be processed and the real-time temperature data of the agent; the control module dynamically corrects the adjustment gain of the agent replenishment unit in step 104 based on the deviation between the equilibrium liquid level reference value and the liquid level differential pressure signal.

[0015] Preferably, the control module contains a fluid characteristic mapping table; the fluid characteristic mapping table records the gas dissolution rate data of agents with different viscosity grades under different pressure gradients; the control module is used to match the corresponding gas dissolution rate from the fluid characteristic mapping table according to the pressure variability data, and use it as the initial physical correction variable for the dynamic compensation coefficient.

[0016] Preferably, the control module obtains the motor frequency converter feedback signal of the drug replenishment unit through the industrial bus; the motor frequency converter feedback signal serves as the physical data source of the real-time operating frequency, and is used to analyze in real time the change in the mechanical shear field intensity generated by the pump impeller on the rheological properties of the drug surface.

[0017] Preferably, the system also includes a status diagnostic unit; the status diagnostic unit is used to continuously record the fluctuation characteristics of the dynamic compensation coefficient within a preset monitoring period; when the rate of change of the fluctuation characteristics exceeds the preset deviation warning threshold, the status diagnostic unit outputs a technical status signal indicating a sudden change in the viscosity of the reagent or cavitation of the impeller of the reagent replenishment unit.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] 1. In the control of reagent liquid level balance, by synchronously collecting the absolute pressure inside the impregnation vessel and the apparent liquid level signal of the drug storage device, and extracting the polarity characteristics of the pressure-time rate of change, an asymmetric compensation mechanism matching the gas-liquid mass transfer dynamics of high-viscosity reagents is constructed. This mechanism addresses the explosive gas release during the depressurization stage and the slow re-dissolution characteristics exhibited during the pressurization stage. By calling differentiated damping coefficients, the nonlinear disturbances caused by the drastic alternation of gas volume with pressure are offset from a logical level. This processing method enables the system to reconstruct the true physical liquid level after eliminating bubble interference in real time, eliminating the phase deviation caused by the inability to perceive phase change hysteresis during the pressure switching window of the traditional static compensation model, and ensuring that the control system always adjusts based on an accurate liquid level reference in complex pressure-changing cycle processes.

[0020] 2. By introducing the operating frequency feedback of the variable frequency pump for the reagent into the liquid level compensation loop, dynamic coupling between the control command execution state and the physical properties of the fluid is achieved. Considering that the impregnating reagent, as a non-Newtonian fluid, has obvious shear thinning properties, the system uses the frequency feedback value of the variable frequency pump to dynamically correct the damping coefficient during the re-dissolution process. This design enables the control logic to automatically identify and offset the local dynamic viscosity decrease caused by the mechanical shear of the pump impeller, preventing liquid level feedback oscillation caused by the collapse of fluid mass transfer resistance during the pressurization and replenishment stage. Through the reverse constraint of the actuator state on the sensing layer data, the system solves the problem of overshoot of the adjustment command caused by the sudden change in reagent viscosity without the need to add a rheological detection entity, thus improving the robustness of the control loop.

[0021] 3. By constructing a multi-dimensional linkage closed loop involving pressure variability identification, asymmetric damping switching, and actuator frequency coupling, the originally isolated pressure sensing, liquid level measurement, and pump drive are transformed into a synergistic gain effect. This cross-variable decoupling control strategy establishes a digital filtering barrier against false liquid level fluctuations under extreme conditions of alternating vacuum and high pressure, controlling the amplitude of liquid level fluctuations within a small physical range. This solution not only effectively avoids material loss caused by the reagent entering the downstream recovery system with the vacuum fluid, but also prevents cavitation in the replenishment pipeline due to severe negative pressure by limiting abnormal peak values ​​of pumping commands. This logical reconstruction based on the mechanism level protects the pump impeller and maintains the continuity of fluid delivery while extending the equipment maintenance cycle of the entire automated production line, demonstrating high engineering practical value. Attached Figure Description

[0022] Figure 1 This is a flowchart of the dynamic decoupling compensation control logic for the drug level in this invention;

[0023] Figure 2 This is a topology diagram of the multi-dimensional operation state switching and monitoring of the system of the present invention.

[0024] The objectives, features, and advantages of this invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0026] A reagent level balance control system for a vacuum impregnation production line includes:

[0027] Differential pressure level detection unit is used to collect differential pressure signals of liquid level inside the impregnation tank;

[0028] The reagent replenishment unit is used to compensate for reagent backflow during the impregnation process.

[0029] The control module is connected to both the differential pressure level detection unit and the reagent replenishment unit. The control module operates the following logic: Step 101, real-time acquisition of the differential pressure signal and pressure variability data characterizing the instantaneous environmental pressure fluctuation amplitude within the impregnation vessel; Step 102, determination of the real-time operating frequency of the reagent replenishment unit during the compensation process, and calculation of the dynamic viscosity parameters of the reagent under the current pumping shear field based on the real-time operating frequency to characterize the interference of non-Newtonian fluid properties on the liquid surface response characteristics; Step 103, determination of the phase change resistance data of the gas-liquid mixture in the impregnation vessel during the pressure change process using the dynamic viscosity parameters, and determination of the dynamic compensation coefficient corresponding to the liquid level fluctuation hysteresis based on the pressure variability data. The dynamic compensation coefficient is used to perform in-situ correction of the adjustment transfer function within the control module; Step 104, adjustment of the output rotation speed of the reagent replenishment unit based on the differential pressure signal, pressure variability data, and the dynamic compensation coefficient corrected by the transfer function, to eliminate the apparent liquid level detection deviation caused by the asymmetric movement of internal dissolved gas precipitation and re-dissolution rate under pressure change conditions.

[0030] Preferably, when the control module runs step 103, it includes the following sub-steps: Step 1031, using a preset rheological characteristic mapping relationship, establish a monotonic correlation logic between the real-time operating frequency and the phase change resistance data; Step 1032, calculate the fluid hysteresis constant corresponding to the dynamic viscosity parameter through the monotonic correlation logic; Step 1033, map the fluid hysteresis constant to a dynamic compensation coefficient to achieve real-time adjustment of the controller output gain.

[0031] Preferably, the control module satisfies the following quantization logic when calculating the dynamic compensation coefficient: Where K is the dynamic compensation coefficient, α is the shear thinning sensitivity coefficient of the reagent, f is the real-time operating frequency of the reagent replenishment unit, and β is the static damping correction term corresponding to the real-time pressure in the impregnation vessel.

[0032] Preferably, the differential pressure level detection unit includes: a total pressure sensor, located in the liquid phase zone at the bottom of the impregnation vessel; a reference pressure sensor, located in the gas phase space at the top of the impregnation vessel; and a differential pressure calculation module, connected to the total pressure sensor and the reference pressure sensor respectively, for performing differential calculation on the total pressure and gas phase pressure inside the vessel to extract the differential pressure signal of the level.

[0033] Preferably, the system also includes a pressure balancing branch; the two ends of the pressure balancing branch are connected to the impregnation vessel and the reagent storage tank respectively, and a proportional regulating valve is provided on the pressure balancing branch; the control module is also used to adjust the opening of the proportional regulating valve according to the pressure variation data, and when the impregnation vessel is in a depressurized state, the expansion displacement of the reagent under negative pressure is offset in real time by a preset volume compensation model.

[0034] Preferably, the control module is further configured to: set an asymmetric adjustment threshold, the asymmetric adjustment threshold including a first opening threshold for initiating the replenishment action and a second closing threshold for stopping the replenishment action; when the impregnation vessel is in the pressure-boosting and remelting stage, adjust the value of the first opening threshold according to the phase change resistance data to avoid a false drop in liquid level caused by bubble volume compression.

[0035] Preferably, the control module further includes a dynamic prediction unit; the dynamic prediction unit is used to calculate the equilibrium liquid level reference value under the current working condition based on the drainage parameters of the workpiece to be processed and the real-time temperature data of the agent; the control module dynamically corrects the adjustment gain of the agent replenishment unit in step 104 based on the deviation between the equilibrium liquid level reference value and the liquid level differential pressure signal.

[0036] Preferably, the control module contains a fluid characteristic mapping table; the fluid characteristic mapping table records the gas dissolution rate data of agents with different viscosity grades under different pressure gradients; the control module is used to match the corresponding gas dissolution rate from the fluid characteristic mapping table according to the pressure variability data, and use it as the initial physical correction variable for the dynamic compensation coefficient.

[0037] Preferably, the control module obtains the motor frequency converter feedback signal of the drug replenishment unit through the industrial bus; the motor frequency converter feedback signal serves as the physical data source of the real-time operating frequency, and is used to analyze in real time the change in the mechanical shear field intensity generated by the pump impeller on the rheological properties of the drug surface.

[0038] Preferably, the system also includes a status diagnostic unit; the status diagnostic unit is used to continuously record the fluctuation characteristics of the dynamic compensation coefficient within a preset monitoring period; when the rate of change of the fluctuation characteristics exceeds the preset deviation warning threshold, the status diagnostic unit outputs a technical status signal indicating a sudden change in the viscosity of the reagent or cavitation of the impeller of the reagent replenishment unit.

[0039] Example 1: In an industrial scenario involving automated vacuum impregnation of large automotive cylinder blocks, the pressure inside the impregnation vessel switches between 0.5 kPa and 0.6 MPa. The impregnation agent, being a high-viscosity non-Newtonian fluid, contains dissolved air. During the high vacuum stage of 0.5 kPa, the system generates agent gas precipitation accompanied by agent volume expansion. This results in the differential pressure signal captured by the differential pressure level detection unit containing measurement deviations caused by apparent bubbles. Simultaneously, during the pressurization to 0.6 MPa, there is a time lag in the re-dissolution of bubbles. The control module acquires the differential pressure signal inside the impregnation vessel in real time and calculates the first-order time derivative of the ambient pressure to extract the polarity characteristics of the pressure variation rate dP / dt. Simultaneously, it reads the feedback signal from the motor inverter of the agent replenishment unit via the industrial bus to obtain the real-time operating frequency f. It then uses a pre-stored rheological mapping table to determine the dynamic viscosity parameters of the agent under the current pumping shear field, characterizing the interference of agent fluid properties on the liquid surface response characteristics. In this conversion and calculation stage, the control module internally executes the dynamic viscosity calculation formula. Where μ is the currently calculated dynamic viscosity parameter. The initial consistency coefficient of this batch of reagent is determined by pre-sampling, k is the impeller shear conversion constant determined by the pump casing structure size, and n is the non-Newtonian fluid characteristic exponent characterizing shear thinning properties with n < 1. The control module performs cycle-by-cycle algebraic calculations on the frequency data transmitted by the communication bus using this built-in formula, seamlessly mapping discrete speed feedback values ​​to continuously decaying viscosity dimensions in the rheological field, establishing a deterministic conversion mechanism for the underlying data. Based on the Ostwald-Dewaer power-law fluid model, the apparent viscosity of the non-Newtonian fluid exhibits a nonlinear decay law with increasing shear force field; combined with Henry's law, the cross-phase dissolution rate of the gas inside the mixed phase is directly constrained by the apparent viscosity of the fluid, constituting the physical transfer... Mass damping: It should be noted that although the pump impeller only generates mechanical shear in a local area of ​​the pipeline, the reagent whose apparent viscosity drops sharply after being sheared by its high frequency will be continuously pumped into the bottom of the impregnation vessel in the form of a high-speed jet under the drive of the system pressure difference. This low-viscosity fluid carrying high kinetic energy violently impacts and breaks the overall static mass transfer boundary layer of the original high-viscosity fluid in the vessel. This allows the surface bubbles, which were originally confined by the high-viscosity liquid film, to obtain a thinner interface film and a higher sliding velocity. Thus, the local shear thinning effect is amplified and diffused across scales to the active phase change zone in the lower part of the entire vessel through forced convection mixing in fluid dynamics, substantially changing the overall damping environment of the mixed phase re-dissolution in the entire vessel.

[0040] To transform the nonlinear multiphase coupled physical process into executable low-level control logic, the control module uses the rated operating fundamental frequency of the reagent replenishment unit as the expansion center. It performs a first-order Taylor approximation expansion on the nonlinear mass transfer damping distribution function of the fluid, transforming the physical time lag effect of dynamic viscosity change on bubble re-dissolution into a linear quantization benchmark driven by a single variable: real-time operating frequency. The control module uses dynamic viscosity parameters to determine the phase change resistance data of the gas-liquid mixture in the impregnation vessel during the pressure change process, and combines this with the pressure change rate dP / dt to determine the dynamic compensation coefficient K corresponding to the liquid level fluctuation hysteresis. This dynamic compensation coefficient K satisfies the quantization logic. Where K is the dynamic compensation coefficient, α is the shear thinning sensitivity coefficient of the reagent, f is the real-time operating frequency of the reagent replenishment unit, and β is the static damping correction term corresponding to the real-time pressure in the impregnation vessel. To obtain the dynamic compensation coefficient K, the control module uses a discretized proportional-integral algorithm as its internal basic adjustment transfer function, setting the dynamic compensation coefficient K as the real-time correction multiplier for the proportional control loop. The control module executes the formula every sampling period. , This is the command to be output to the inverter of the reagent replenishment unit to control the target operating frequency. To correspond to the current volumetric gain constant of the impregnation vessel, e is the physical deviation of the current actual liquid level extracted from the liquid level differential pressure signal. As the integral gain constant, this calculation procedure establishes a deterministic action logic from the fluid surface resistance characteristics to the underlying motor actuator hardware speed constraints. A dynamic prediction unit is added internally to perform feedforward adjustment on top of the base gain. This prediction unit reads the 3D model of the current batch of workpieces from the industrial network to calculate the solid drainage volume parameters under immersion conditions. It then combines this with real-time reagent temperature data fed back from the thermistor inside the impregnation tank and calls the pre-stored fluid thermal expansion coefficient. The drainage volume increment and temperature expansion margin are superimposed onto the initial zero liquid level to calculate the equilibrium liquid level reference value corresponding to the current operating conditions. When the liquid level differential pressure signal deviates from this dynamically evolving reference value, the control module... The proportional gain constant Kp in the aforementioned transfer function formula is then dynamically corrected to achieve adaptive matching of the adjustment margin. The control module adjusts the output speed of the reagent replenishment unit based on the liquid level differential pressure signal, pressure variation rate dP / dt, and the adjustment transfer function corrected by the dynamic compensation coefficient K. When the system is in the pressure boosting and remelting stage and dP / dt is greater than 0, the first opening threshold for starting the reagent replenishment action is increased according to the phase change resistance data to avoid false liquid level drop caused by bubble volume compression. This controls the liquid level fluctuation in the impregnation tank to within 5mm, ultimately preventing pipeline cavitation of the 5.5kW reagent replenishment unit under 0.5kPa negative pressure.

[0041] Example 2: The regulation characteristics of the reagent level balance control system were verified in a sealed container with a volume of 2 cubic meters, simulating an impregnation vessel. The sealed container was connected to a vacuum pump group with a maximum pumping speed of 150 L / s and a compressed air booster unit with a maximum output pressure of 1.0 MPa. The test reagent used was an impregnation liquid with an initial dynamic viscosity of 480 mPa·s. Gaussian white noise with a signal-to-noise ratio of 20 dB and a 50 Hz power frequency interference pulse were superimposed on the liquid level differential pressure signal. The control module controlled the sampling period... The system was configured to identify the signal bandwidth characteristics caused by sudden pressure changes and the hardware response time of the sensor. When the pressure in the impregnation vessel changes from 0.5 kPa to 0.6 MPa within 1 second, the signal bandwidth output by the level detection unit is 20 Hz. To satisfy the sampling theorem and avoid signal aliasing, the sampling frequency is determined to be 5 times the bandwidth. The sampling period T is thus determined to be 10 ms, balancing the real-time monitoring of the liquid level in the vessel with the computational load of the processor. The definition of the above-mentioned 20 Hz physical signal bandwidth boundary comes from the frequency domain characteristic measurement and calibration before the system was put into operation. In the calibration phase, the Fast Fourier Transform (FFT) algorithm was used to perform offline spectral decomposition on 100 sets of original waveforms picked up by the level sensor under extreme pressure shock conditions. The results confirmed that more than 98% of the effective liquid surface fluctuation energy excited by physical phase change processes such as real gas-liquid mixing and foam rise and fall is concentrated in the low frequency range of 0Hz to 20Hz. The high frequency peaks outside this band were identified as background noise caused by frequency conversion electromagnetic interference and pump body mechanical vibration, thus providing solid engineering measurement data support for this core cutoff frequency.

[0042] Three comparative sample groups were set up in the experiment. Comparative sample group 1 used a fixed-gain PID control logic, comparative sample group 2 used logic with pressure variability compensation but without frequency feedback, and the sample group of this invention used closed-loop logic that corrected the dynamic compensation coefficient K based on the real-time operating frequency f, where f is the real-time operating frequency of the reagent replenishment unit and K is the dynamic compensation coefficient. Under the condition of an ambient pressure variability dP / dt of 55 kPa / s, the peak liquid level fluctuation recorded by comparative sample group 1 was 48.6 mm, accompanied by a low-frequency oscillation lasting 1.5 s, while the peak liquid level fluctuation recorded by comparative sample group 2 was 19.3 mm, and the output response had a phase lag of 0.8 s. The sample group of this invention, by mapping the real-time operating frequency f to a shear weakening factor for the decrease in fluid viscosity, maintained the peak liquid level fluctuation at 4.2 mm and the response delay within 85 ms, where dP / dt is the ambient pressure variability, and the logic was applied to the real-time operating frequency f of the reagent replenishment unit. Gradient verification showed that when the real-time operating frequency f increased within the range of 10Hz to 45Hz, the reagent experienced shear thinning due to the mechanical shearing action of the impeller. The dynamic viscosity parameter showed a nonlinear decreasing trend with increasing frequency. The system automatically increased the gain compensation amount through the dynamic compensation coefficient K to match the decrease in fluid resistance, keeping the liquid level fluctuation within the range of less than 4.5mm. However, when the real-time operating frequency f exceeded the performance inflection point of 55Hz, the rate of decrease in the dynamic viscosity parameter slowed down and entered the saturation region due to the shear limit reached by the large molecular entanglement structure of the reagent, and the improvement in liquid level control accuracy tended to level off. By extracting the physical action parameters of the actuator to correct the transfer function of the controlled object, the interference of gas-liquid mass transfer asymmetry under variable pressure environment on liquid level regulation was eliminated. The system controlled the liquid level tracking error within 5mm in a 20dB noise environment, preventing pipeline cavitation in the 5.5kW reagent replenishment unit and maintaining the reagent balance in the impregnation vessel.

[0043] Example 3: In an industrial production maintenance scenario involving the replacement of impregnation agents, the system faces the engineering challenge of unknown rheological parameters of the new agent. The initial viscosity and the sensitivity of the new agent's macromolecular chain density to shear rate differ from those of the original agent. This causes the shear thinning sensitivity coefficient α and rheological property mapping table pre-stored in the control module to fail to characterize the physical damping behavior of the current agent during replenishment pumping. Without in-situ calibration based on the physical properties, the correction amount of the dynamic compensation coefficient K will deviate from the actual pressure response trend of the fluid, thus leading to… To address the issue of delayed or overcompensated replenishment during the pressurization phase and the uncertainty of the aforementioned physical properties, the system initiates an initial calibration procedure based on actuator feedback. The control module drives the agent replenishment unit to operate at three frequency points—15Hz, 30Hz, and 45Hz—and maintains them for 30 seconds. Simultaneously, the system utilizes the real-time operating frequency f fed back by the motor inverter, the corresponding pumping torque signal, and the differential pressure sensors at both ends of the pipeline to measure the instantaneous pressure loss in the flow channel. Based on the fluid dynamics equations, the measured dynamic viscosity values ​​of the agent under different shear intensities are derived.

[0044] The control module calculates the first-order difference sequence of the measured dynamic viscosity values ​​at each working node as a function of the real-time operating frequency f, extracts the slope characteristics of the viscosity decay curve, and thus calibrates the shear thinning sensitivity coefficient α of the agent to be 0.138. Simultaneously, it writes the frequency of each node and the corresponding viscosity value into the storage unit to construct a rheological property mapping table that supports real-time retrieval, thereby providing a definite physical quantity basis for the calculation of the dynamic compensation coefficient K. After calibration, the dynamic compensation coefficient K intervenes to adjust the transfer function during the remelting stage when the impregnation tank pressure rises to 0.6 MPa. The control module adjusts the transfer function based on the real-time pressure variation rate dP / dt and the real-time operating frequency. By locking in the phase change resistance data for bubble re-dissolution, the first activation threshold for the replenishment action was increased by 12% from the original baseline. This adjustment was determined based on the proportional relationship between viscosity increment and pressure transmission delay established during calibration. This compensated for the response lag caused by the increased viscosity of the new reagent, maintaining the liquid level in the impregnation vessel at the preset 500mm median level. The calibrated system was tested under a 1.0MPa ultimate pressure shock based on real-time operating frequency. By adjusting the output speed of the reagent replenishment unit, the phase deviation caused by pressure fluctuations was eliminated. The system controlled the fluctuation amplitude of the liquid level in the impregnation tank to within 5mm, preventing pipeline cavitation caused by the 5.5kW driving power reagent replenishment unit under negative pressure. Example 4: This example combines Figures 1 to 2 A description of a reagent level balance control system in a vacuum impregnation production line, such as... Figure 1As shown, the system executes a decoupling compensation procedure consisting of steps 101 to 104. First, in step 101, the liquid level differential pressure signal and pressure variability data are acquired in real time to characterize the amplitude of the instantaneous environmental pressure change in the impregnation vessel. Then, in step 102, the real-time operating frequency of the reagent replenishment unit is determined and the dynamic viscosity parameter of the reagent is calculated to characterize the interference of non-Newtonian fluid properties on the liquid surface response characteristics. Next, in step 103, the dynamic viscosity parameter is used to determine the phase change resistance data of the gas-liquid mixture, and the dynamic compensation coefficient is determined in combination with the pressure variability data to perform in-situ correction of the adjustment transfer function. Finally, in step 104, the output rotation speed of the reagent replenishment unit is adjusted based on multidimensional data and the corrected transfer function to eliminate the apparent liquid level detection deviation caused by the asymmetric motion inside the reagent.

[0045] like Figure 2 As shown, the control system achieves closed-loop monitoring through topology switching of multi-dimensional operating states. When the system is in state A, i.e., the quasi-steady state of conventional liquid level control, if the reference pressure sensor inside the vessel detects a change in ambient pressure, the system will automatically switch to state B to start instantaneous pressure change monitoring. Subsequently, the pressure rate extraction module generates pressure rate data to drive the system into the core state, i.e., the dynamic compensation factor calculation state. Under this core node, the transfer function in-situ correction module generates a correction factor and guides the system into state C to execute motor frequency conversion adjustment until the reagent replenishment unit adjusts the motor speed and completes the compensation before returning to state A. At the same time, if the state diagnosis unit detects abnormal fluctuation characteristics of the compensation coefficient, the system switches from the core state to the monitoring state and issues an abnormal state and cavitation warning. The feedback branch of the monitoring system is closed by executing the safety intervention action of the total pressure sensor inside the vessel.

[0046] Example 5: In a long-term process scenario with more than 500 continuous impregnation cycles, the solvent of the agent carrier evaporates slightly over time, causing a shift in the initial viscosity of the fluid. The control module initiates an online parameter reconstruction procedure during the unloaded phase of workpiece loading and unloading. By collecting the motor feedback torque of the agent replenishment unit at a fixed frequency of 15Hz and comparing it with the initial calibration reference value in the rheological property mapping table, the viscosity correction vector characterizing the change of agent components is calculated and applied to the real-time solution logic of the dynamic compensation coefficient K. The shear thinning sensitivity coefficient of the agent is dynamically updated to 0.141, realizing the autonomous adaptation of the control loop to the drift of the agent rheological properties, so that the steady-state deviation of the liquid level under the 1.0MPa cyclic pressure impact is maintained within 3mm.

[0047] When the system faces a situation where the absolute pressure inside the impregnation vessel frequently switches between a high vacuum range of 0.5 kPa and a high pressure range of 0.6 MPa, accompanied by pressure bypass relief, the control module determines the value of the static damping correction term β by quantifying the pressure change rate dP / dt and the absolute pressure position in real time. The system discretizes the pressure range covered by the impregnation process into several characteristic steps and extracts the static damping correction term β corresponding to the current physical pressure from the preset damping matrix. At the instant when the sign of the pressure change rate dP / dt changes from negative to positive, the control module adjusts the transfer function to adjust the output gain of the reagent replenishment unit to the level corresponding to the dense phase resistance of the fluid, eliminating the execution caused by the sudden change in gas phase volume. In the event of a pressure relief phase caused by a sudden drop in pressure leading to explosive gas phase precipitation and a rapid expansion of apparent volume, the control module activates a volume compensation model to regulate the pressure balance branch. This model does not futilely drive liquid phase flow to suppress the germination of surface bubbles. Instead, it utilizes the atmospheric pressure reagent storage tank connected after the proportional control valve is opened as an overall unloading buffer. This allows the excess gas-liquid mixture volume forcibly squeezed out of the impregnation vessel due to a large phase change to be autonomously guided and discharged into the storage tank based on the physical pressure difference between the two sides. This mechanism, through spatial transfer, offsets and eliminates the apparent displacement increment inside the vessel at the overall system level, fundamentally preventing the overflow failure of the foam liquid surface.

[0048] Example 6: In a large-scale deployment scenario involving multiple impregnation tanks of different volumes, the sensing end of the differential pressure level detection unit is subjected to a pressure cycle of 0.5 kPa to 0.6 MPa for a long time. The sensing diaphragm undergoes inelastic displacement deviation. During the process interval, the control module initiates the sensor physical zero-point self-calibration procedure. By opening the electromagnetic balance valve in the pressure tapping pipeline, the sensing ends of the total pressure sensor and the reference pressure sensor are placed in the same 0.5 kPa high vacuum environment. The sensing deviation value generated at this time is read and defined as the initial state compensation parameter. This value is applied to the calculation logic of the differential pressure level signal to eliminate the detection error caused by hardware stress hysteresis and ensure that the system always performs level analysis based on the physical zero point within a 10 ms calculation cycle.

[0049] To address the interference from the physical characteristics of replenishment pipelines in different production lines, the control module initiates an association matrix calibration procedure for the static damping correction term β. The drive unit operates at a frequency step of 5Hz within the 5Hz to 60Hz range, simultaneously acquiring the pumping torque signal fed back from the motor inverter. The system establishes a mapping relationship between the measured torque values ​​at each frequency node and the shear thinning sensitivity coefficient of the agent, generating a damping vector sequence and storing it in the internal damping matrix. This allows the dynamic compensation coefficient K, after adjustment of the transfer function, to lock the damping component of the actuator at different flow rates based on the real-time operating frequency f, stabilizing the speed adjustment response delay of the 5.5kW agent replenishment unit within 85ms. This system configuration, combining physical zero-point adaptive calibration with dynamic damping matrix filling, embodies a design approach that leverages initial state determinism to ensure process control determinism. By establishing a compensation barrier within the control logic to address hardware drift and physical environment differences, it achieves the binding of the adjustment algorithm with the underlying physical entity attributes, providing a steady-state liquid level balance control basis for automotive parts impregnation lines.

[0050] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. 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 be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A reagent level balance control system for a vacuum impregnation production line, characterized in that, include: Differential pressure level detection unit is used to collect differential pressure signals of liquid level inside the impregnation tank; The reagent replenishment unit is used to compensate for reagent backflow during the impregnation process. The control module is connected to the differential pressure level detection unit and the reagent replenishment unit respectively; the control module is used to run the following logic: Step 101, real-time acquisition of the differential pressure signal of the liquid level and the pressure rate data characterizing the instantaneous environmental pressure change amplitude in the impregnation tank; Step 102: Determine the real-time operating frequency of the agent replenishment unit during the compensation process, and calculate the dynamic viscosity parameters of the agent under the current pumping shear field based on the real-time operating frequency to characterize the interference of non-Newtonian fluid properties on the liquid surface response characteristics. Step 103: Determine the phase change resistance data of the gas-liquid mixture in the impregnation vessel during the pressure change process using dynamic viscosity parameters, and determine the dynamic compensation coefficient corresponding to the liquid level fluctuation hysteresis by combining the pressure change rate data. The dynamic compensation coefficient is used to correct the regulation transfer function inside the control module in situ. Step 104: Based on the liquid level differential pressure signal, pressure change rate data, and the dynamic compensation coefficient corrected by the transfer function, adjust the output speed of the reagent replenishment unit to eliminate the apparent liquid level detection deviation caused by the asymmetric movement of the internal dissolved gas precipitation and re-dissolution rate under the pressure change environment.

2. The reagent level balance control system in a vacuum impregnation production line according to claim 1, characterized in that, When the control module runs step 103, it includes the following sub-steps: Step 1031, using a preset rheological characteristic mapping relationship, establishes a monotonic correlation logic between the real-time operating frequency and the phase change resistance data; Step 1032, calculates the fluid hysteresis constant corresponding to the dynamic viscosity parameter through the monotonic correlation logic; Step 1033, maps the fluid hysteresis constant to a dynamic compensation coefficient to achieve real-time adjustment of the controller output gain.

3. The reagent level balance control system in a vacuum impregnation production line according to claim 1, characterized in that, When calculating the dynamic compensation coefficients, the control module satisfies the following quantization logic: ;in, For dynamic compensation coefficients, The shear-thinning sensitivity coefficient of the drug. The real-time operating frequency of the drug replenishment unit. This is a static damping correction term corresponding to the real-time pressure inside the impregnation vessel.

4. The reagent level balance control system in a vacuum impregnation production line according to claim 1, characterized in that, The differential pressure level detection unit includes: a total pressure sensor, located in the liquid phase zone at the bottom of the impregnation vessel; a reference pressure sensor, located in the gas phase space at the top of the impregnation vessel; and a differential pressure calculation module, connected to the total pressure sensor and the reference pressure sensor respectively, used to perform differential calculation on the total pressure and gas phase pressure inside the vessel to extract the differential pressure signal of the liquid level.

5. The reagent level balance control system in a vacuum impregnation production line according to claim 1, characterized in that, The system also includes a pressure balancing branch; the two ends of the pressure balancing branch are connected to the impregnation vessel and the reagent storage tank respectively, and a proportional regulating valve is provided on the pressure balancing branch; the control module is also used to adjust the opening of the proportional regulating valve according to the pressure change data, and when the impregnation vessel is in a depressurized state, it uses a preset volume compensation model to counteract the expansion displacement of the reagent under negative pressure in real time.

6. The reagent level balance control system in a vacuum impregnation production line according to claim 1, characterized in that, The control module is also used to: set an asymmetric adjustment threshold, which includes a first opening threshold for initiating the replenishment action and a second closing threshold for stopping the replenishment action; when the impregnation vessel is in the pressure-boosting and remelting stage, the value of the first opening threshold is increased according to the phase change resistance data to avoid a false drop in liquid level caused by bubble volume compression.

7. The reagent level balance control system in a vacuum impregnation production line according to claim 1, characterized in that, The control module also includes a dynamic prediction unit; the dynamic prediction unit is used to calculate the equilibrium liquid level reference value under the current working condition based on the drainage parameters of the workpiece to be processed and the real-time temperature data of the agent; the control module dynamically corrects the adjustment gain of the agent replenishment unit in step 104 based on the deviation between the equilibrium liquid level reference value and the liquid level differential pressure signal.

8. The reagent level balance control system in a vacuum impregnation production line according to claim 1, characterized in that, The control module contains a fluid characteristic mapping table; the fluid characteristic mapping table records the gas dissolution rate data of agents with different viscosity grades under different pressure gradients; the control module is used to match the corresponding gas dissolution rate from the fluid characteristic mapping table according to the pressure variability data, and use it as the initial physical correction variable for the dynamic compensation coefficient.

9. The reagent level balance control system in a vacuum impregnation production line according to claim 1, characterized in that, The control module obtains the motor frequency converter feedback signal of the reagent replenishment unit through the industrial bus; the motor frequency converter feedback signal serves as the physical data source of the real-time operating frequency, and is used to analyze in real time the changes in the mechanical shear field intensity generated by the pump impeller on the rheological properties of the reagent surface.

10. A reagent level balance control system in a vacuum impregnation production line according to claim 1, characterized in that, The system also includes a status diagnostic unit; the status diagnostic unit is used to continuously record the fluctuation characteristics of the dynamic compensation coefficient within a preset monitoring period; when the rate of change of the fluctuation characteristics exceeds the preset deviation warning threshold, the status diagnostic unit outputs a technical status signal indicating a sudden change in the viscosity of the reagent or cavitation of the impeller of the reagent replenishment unit.

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