Oil-free self-adaptive addition control method and system for DMDC electromagnetic metering pump

Abstract

The application discloses a kind of DMDC electromagnetic metrology pump oil-free self-adapting addition control method and system.The method includes system initialization, material flow real-time monitoring, DMDC physical property parameter real-time calculation, target stroke frequency initial calculation, temperature-flow-stroke frequency three-dimensional self-adaptive compensation, electromagnetic metrology pump oil-free driving output, closed-loop feedback verification, multi-zone collaborative anti-solidification priority control and the like steps.The system includes electromagnetic metrology pump, electromagnetic flowmeter, multi-zone temperature monitoring module, multi-zone heating module, PLC controller, metrology verification module and local man-machine interface module and the like.The application can completely cancel hydraulic oil system, reduce equipment maintenance cost and food safety risk, and is suitable for beverage production line DMDC cold sterilization online addition.

Description

Technical Field

[0001] This invention relates to the field of control technology for online cold sterilization equipment for beverages, specifically to a control method and system that uses an oil-free electromagnetic metering pump as the core actuator for the precise online addition of dimethyl dicarbonate (DMDC, CAS No. 4525-33-1, trade name Velcorin), and achieves this through a three-dimensional adaptive compensation model of temperature-flow-stroke frequency. Background Technology

[0002] DMDC is a highly effective cold sterilizer that can kill yeast, mold, and spoilage bacteria in beverages at low doses of 50-250 ppm. Its decomposition products are methanol and carbon dioxide, with minimal impact on beverage flavor. However, DMDC has unique physicochemical properties: a freezing point of approximately 17°C (with a tendency to be supercooled), and a density of 1.25 g / cm³ at 20°C. 3 It has a dynamic viscosity of 2.1 ± 0.1 mPa·s and a vapor pressure of only 0.7 hPa (20℃). Its viscosity increases sharply as the temperature approaches its freezing point; it hydrolyzes rapidly upon contact with water; and it is highly irritating to the skin, eyes, and respiratory tract (R23 / R34). These characteristics dictate that DMDC must be added online under closed, constant-temperature, and precisely metered conditions.

[0003] Currently, the dominant DMDC filling equipment in the international market uses an MTV-type magnetically driven hydraulic metal diaphragm metering pump, which uses a special pharmaceutical-grade white oil (WEISSOEL W 505, Ph.Eur. grade) as the hydraulic transmission medium. The metal diaphragm is driven to reciprocate through a hydraulic constant pressure system to achieve accurate DMDC metering. It also integrates functions such as IoT gateway, remote maintenance, WebVisu visualization, E+H Coriolis mass flow meter and touch screen control, covering the full flow range of 0.6-79.2 T / H and possessing Industry 4.0 capabilities. Although this solution has high metering stability, it has the following inherent defects: (1) The hydraulic oil system needs to be replaced regularly (about 15 million strokes or 2 years), resulting in high maintenance costs; (2) There is a risk of minor leakage of hydraulic oil contaminating DMDC or beverages, posing a potential threat to food safety; (3) The hydraulic pump has a complex structure, relies on imported spare parts, and has a long maintenance cycle; (4) The use of touch screen + remote maintenance has complex digital functions, which poses a high operating threshold for small and medium-sized enterprises.

[0004] The domestically produced bamboo filling machine (YS series) uses an electromagnetic metering pump instead of a hydraulic pump, eliminating the hydraulic oil system and reducing costs and pollution risks. However, the stroke volume of the electromagnetic metering pump is significantly affected by changes in DMDC temperature and viscosity. Under conditions of fluctuating ambient temperature or low flow rate, problems such as dosage drift and nozzle crystallization blockage may occur.

[0005] Existing technologies lack adaptive control methods and systems for oil-free electromagnetic metering pumps that address the physical properties of DMDC (especially viscosity abrupt changes near 17°C), resulting in a gap in accuracy and stability between domestically produced equipment and imported equipment. Therefore, there is an urgent need for a control method and system capable of adaptive compensation based on real-time DMDC physical property parameters, material flow rate, and ambient temperature, while avoiding the pitfalls of publicly disclosed patented technologies such as hydraulic pumps, 6-pin interfaces, 10-stroke calibration, and remote maintenance via touchscreens. Summary of the Invention

[0006] To address the aforementioned technical problems and shortcomings in this field, this invention provides an oil-free adaptive addition control method and system for DMDC electromagnetic metering pumps, relating to the field of online addition control technology for beverage cold sterilization. This invention addresses the technical deficiencies of DMDC (dimethyl dicarbonate, CAS No. 4525-33-1), such as its tendency to crystallize near 17℃, significant viscosity changes with temperature, and the high maintenance costs and food safety risks associated with existing hydraulic metering pumps requiring a dedicated white oil system. It adopts an oil-free electromagnetic metering pump solution, establishing a three-dimensional adaptive compensation model based on temperature, flow rate, and stroke frequency. By real-time monitoring of the DMDC storage temperature, material flow rate, and pump head temperature, the stroke frequency and duty cycle of the electromagnetic metering pump are dynamically corrected, and a four-zone coordinated preheating and anti-coagulation priority strategy is implemented. Based on the atmospheric pressure physical properties of DMDC (dynamic viscosity 2.1±0.1 mPa·s at 20℃, density 1.25 g / cm³), the method is optimized for oil-free addition control. 3 This invention establishes a viscosity-temperature index compensation formula and a pump efficiency aging correction model, ensuring that the online addition accuracy error of DMDC is ≤±5% within a flow range of 3-18 T / H and an ambient temperature of 4-35℃, with the addition amount continuously adjustable from 50-250 ppm. This invention completely eliminates the hydraulic oil system, reducing equipment maintenance costs and food safety risks, and is suitable for online addition of DMDC for cold sterilization in domestic beverage production lines. Furthermore, the oil-free adaptive addition control method and system for DMDC electromagnetic metering pumps of this invention are applicable to the online quantitative addition of DMDC for cold sterilization in liquid foods such as fruit juices, non-alcoholic beverages, and low-alcohol wines.

[0007] The specific technical solution of this invention is as follows: In a first aspect, the present invention provides an oil-free adaptive metering control method for a DMDC electromagnetic metering pump, comprising the following steps: S1. Provide an equipment cabinet, including an upper cabinet and a lower cabinet. The lower cabinet houses a DMDC storage bottle, which is connected to a buffer tank via piping and control valves. Construct a multi-zone heating module, including an upper cabinet heating zone, a lower cabinet left heating zone, a lower cabinet right heating zone, and a nozzle piping heating zone. Each zone has independent PID temperature control (ensuring uniform DMDC temperature above its freezing point), so that the DMDC storage temperature T_liquid reaches the preset operating temperature range [T_min, T_max], where T_min ≥ 20℃ and T_max ≤ 30℃. The nozzle piping is connected to an electromagnetic metering pump to deliver the DMDC for mixing with the beverage material flow.

[0008] S2. Real-time acquisition of beverage material flow rate Q, and transmission of the flow rate signal to the PLC controller.

[0009] S3. Based on the real-time T_liquid, dynamically calculate the DMDC density ρ(T) and dynamic viscosity μ(T) at the current temperature using the built-in property parameter lookup table or Arrhenius-type fitting formula. The dynamic viscosity μ(T) of DMDC in the 17-30℃ range is calculated using the formula μ(T) = μ_20·exp[-k_μ·(T-20)], where μ_20 = 2.1 mPa·s (reference viscosity at 20℃) and k_μ = 0.035 / ℃ (temperature sensitivity coefficient). The fitting error of this formula in the 17-30℃ range is <±3%, obtained by regression analysis of 6 measured viscosity data points of DMDC in the 17-30℃ range using the Arrhenius model (directly derived from the Arrhenius-type viscosity temperature dependence law of DMDC carbonate compounds). The density ρ(T) is in g / cm³. 3 The linear formula ρ(T) = 1.25 - 0.0012·(T-20) is used for calculation.

[0010] S4. Based on the set addition ratio C (unit: mL / kL, corresponding to 50-250 ppm) and material flow rate Q, calculate the theoretically required DMDC volumetric flow rate q_DMDC=C·Q / 1000, where C is in mL / kL, Q is in L / h, and q_DMDC is in mL / h. Based on the theoretical single-stroke displacement V_stroke_0 of the electromagnetic metering pump (calibrated by the pump manufacturer, such as 0.5 mL / stroke), calculate the initial stroke frequency f_0=q_DMDC / V_stroke_0.

[0011] S5 and the PLC controller call the temperature-flow-stroke frequency three-dimensional adaptive compensation model to correct the initial stroke frequency f_0, obtaining the actual output stroke frequency f_out = f_0·K_T·K_Q·K_η; where K_T is the temperature compensation coefficient, K_Q is the flow rate compensation coefficient, and K_η is the pump efficiency compensation coefficient. The temperature compensation coefficient K_T considers the effects of density and viscosity changes on pump volumetric efficiency, based on the linear decrease of DMDC density with temperature (temperature coefficient -0.0012 g / (cm³)). 3 The law of viscosity decreasing with temperature (℃) was established; the flow compensation coefficient K_Q was nonlinearly corrected for low flow conditions (<6 T / H); the pump efficiency compensation coefficient K_η was corrected for aging and thermal drift based on the cumulative stroke count and pump head temperature.

[0012] S6, the PLC controller outputs the corrected stroke frequency f_out and duty cycle D to the electromagnetic metering pump drive module, driving the pump head to execute precise strokes in an oil-free manner (no hydraulic oil is required between the electromagnetic metering pump head and the drive mechanism); the electromagnetic metering pump drive module uses PWM chopper drive or constant current chopper drive. This invention adopts an oil-free electromagnetic metering pump solution, which can completely eliminate the hydraulic oil system.

[0013] S7. Monitor the actual DMDC volume q_actual discharged per unit time in real time, and calculate the deviation Δq = q_actual - q_DMDC; if |Δq / q_DMDC| > preset threshold ε (ε = 3%-8%, preferably 5%), return to S5 for correction. The correction method is to multiply each of the original K_T, K_Q, and K_η by λ = 1 + Δq / q_DMDC; if the deviation still exceeds the limit after N consecutive corrections (N≥3), an alarm is triggered and the machine is stopped to prevent over- or under-addition. This invention uses software automatic verification, with the PLC automatically calculating the number of strokes and performing the verification, eliminating the need for manual counting of 10 strokes.

[0014] S8. Priority Control for Anti-condensation under Abnormal Conditions: When the ambient temperature T_amb ≤ 15℃ or 18℃ ≤ T_liquid < 20℃, the PLC controller prioritizes increasing the power of the nozzle pipeline heating zone to exceed the rated power (e.g., 120% of the rated power). The upper cabinet heating zone, lower cabinet left heating zone, and lower cabinet right heating zone heat at the rated power, and can selectively (either reduce or not reduce) reduce the stroke frequency f_out to 60%-80% of the normal value; when 17℃ ≤ T_liquid < 18℃, the PLC... The controller prioritizes increasing the power of the nozzle heating zone to over 120% of its rated power, the power of the lower cabinet left and right heating zones to 105%-115% (e.g., 110%) of their rated power, and the power of the upper cabinet heating zone to 70%-100% (e.g., 80%) of its rated power. It also reduces the stroke frequency f_out to 60%-80% of its normal value (to extend the residence time of the DMDC in the pipeline and ensure sufficient preheating, preventing crystallization and blockage at the nozzles). When T_liquid < 17℃, the system is forced to shut down and a low-temperature alarm is triggered. When the ambient temperature drops sharply or the DMDC temperature approaches its freezing point, the PLC controller activates a priority strategy, prioritizing the heating power of the nozzle pipeline and, if necessary, reducing the stroke frequency to extend the preheating time, fundamentally preventing nozzle crystallization and blockage.

[0015] In the above steps, S1 involves system initialization, S2 involves real-time monitoring of material flow, S3 involves real-time calculation of DMDC physical property parameters, S4 involves initial calculation of target stroke frequency, S5 involves three-dimensional adaptive compensation of temperature-flow-stroke frequency, S6 involves oil-free drive output of electromagnetic metering pump, S7 involves closed-loop feedback verification, and S8 involves multi-zone collaborative anti-solidification priority control.

[0016] Furthermore, the temperature compensation coefficient K_T is calculated using the following formula: K_T=[ρ(T_0) / ρ(T)]·[μ(T) / μ(T_0)]^α, where T_0=20℃ is the reference temperature, and ρ(T_0)=1.25 g / cm³. 3 μ(T_0) = 2.1 mPa·s, where α is the viscosity influence weighting coefficient, ranging from 0.4 to 0.6. The above formula is based on the experimental law that the dynamic viscosity of the DMDC at normal pressure decreases exponentially with temperature, while the density decreases linearly with temperature. The effect of viscosity change on the volumetric efficiency of the electromagnetic metering pump is much greater than that of density change. The weighting coefficient α is set to 0.4-0.6 to reflect the dominant role of viscosity in the total compensation. When T > 20℃, K_T < 1 (frequency reduction); when T < 20℃, K_T > 1 (frequency increase).

[0017] Furthermore, the flow condition compensation coefficient K_Q is set according to a continuous piecewise function: when Q≥6000 L / h, K_Q=1.0; when Q<6000 L / h, K_Q=1.0+β·(6000-Q) / 6000. β is determined through experimental fitting to ensure continuity, and the stroke length of the electromagnetic metering pump is shortened to 50%-70% of the rated value and the PWM response frequency is increased to 130%-150% of the rated value to maintain metering accuracy.

[0018] This invention can use software for automatic stroke verification and touch screen input of set values, with the PLC controller automatically calculating and performing the verification.

[0019] Furthermore, the pump efficiency compensation coefficient K_η is adjusted for aging based on the cumulative number of operating strokes N_stroke and the pump head temperature T_pumphead: K_η=1-γ·ln(1+N_stroke / N_0)-δ·|T_pumphead–T_opt|, where N_0 is the baseline life (the example value can be 1×10). 6 The pump head aging coefficients are: γ (e.g., stroke), δ (e.g., temperature deviation coefficient), and T_opt (e.g., optimal pump head operating temperature). K_η is required to be ≥ 0.5. When K_η < the warning value, a pump head aging warning is triggered, prompting maintenance personnel to check diaphragm wear and / or spring fatigue. The warning value can be 0.85, corresponding to a pump efficiency decrease of approximately 15%, at which point the single-stroke displacement deviation will exceed the compensable range.

[0020] Furthermore, the temperature setpoints for each zone of the multi-zone heating module are automatically sorted according to anti-freezing priority: the target temperature for the nozzle pipeline heating zone is T_set_nozzle = 28±2℃, the target temperatures for the lower left and lower right heating zones are T_set_lower = 24±2℃, and the target temperature for the upper heating zone is T_set_upper = 22±2℃. When the total heating power is limited, the PLC controller allocates power according to the priority of T_set_nozzle > T_set_lower > T_set_upper, ensuring that the DMDC temperature at the nozzle is always more than 10℃ higher than the freezing point of 17℃. This priority strategy is based on the fluid dynamics characteristics of DMDC, where the viscosity increases sharply and the flow resistance increases near 17℃.

[0021] Furthermore, the electromagnetic metering pump drive module has an adjustable drive frequency of 10-200 Hz and an adjustable duty cycle D of 20%-95%.

[0022] Furthermore, the electromagnetic metering pump is either an electromagnetically driven diaphragm pump or an electromagnetically driven plunger pump. The pump head uses a PTFE diaphragm or a ceramic plunger, and the material of the pump head contacting the DMDC is 316L stainless steel or Hastelloy C-276. This oil-free drive completely eliminates the hydraulic oil transmission system, avoiding the risk of hydraulic oil leakage contaminating the DMDC or beverages. The PLC controller outputs a PWM signal to drive the electromagnetic metering pump, and the electromagnet directly drives the diaphragm or plunger to reciprocate, eliminating the need for hydraulic oil as a force transmission medium.

[0023] Furthermore, the oil-free adaptive addition control method for the DMDC electromagnetic metering pump also includes a DMDC storage bottle internal pressure monitoring and adaptive suction control step: A pressure sensor installed at the DMDC storage bottle opening and / or the top of the buffer tank monitors the internal pressure P_bottle in real time; when P_bottle > 0.05 MPa gauge pressure, the PLC controller extends the intermittent compressed air suction interval to 1.5-2 times the normal value to prevent DMDC leakage due to full bottle pressure; when P_bottle < -0.02 MPa gauge pressure, the suction interval is shortened to 0.5-0.7 times the normal value to prevent excessive negative pressure from causing the electromagnetic metering pump to run dry and cavitate. 0.05 MPa corresponds to 80% of the rated pressure of the storage bottle, and -0.02 MPa corresponds to the minimum allowable suction pressure of the pump head. The above adaptive suction control does not require a dedicated 6-pin interface and K2 Bottle Change pin definition. This invention can use a domestically produced general-purpose RS485 / Modbus or dry contact interface.

[0024] Furthermore, the oil-free adaptive addition control method for the DMDC electromagnetic metering pump also includes a safety redundancy control step based on DMDC decomposition kinetics: the PLC controller calculates the DMDC decomposition rate η_decomp=1-exp(-k_d·t_residence) according to the first-order decomposition kinetic model based on the real-time T_liquid and the residence time t_residence of DMDC in the buffer tank, where k_d is the temperature-dependent decomposition rate constant, k_d=k_d(20)·exp[-Ea / R·(1 / T-1 / 293.15)], and k_d(20) represents the decomposition rate constant at 20℃ (approximately 0.012 h). -1 Ea represents the empirical value of the decomposition activation energy parameter, R represents the molar gas constant, and T represents the temperature. When η_decomp > the preset warning value (e.g., 8%), a DMDC activity decay warning is triggered, prompting the operator to replace the storage solution or shorten the replenishment cycle. The decomposition kinetic parameters can be established based on the thermodynamic stability data of the DMDC at atmospheric pressure with a vapor pressure of 0.7 hPa (20℃).

[0025] Furthermore, the PLC controller has a built-in local touchscreen HMI that supports multiple languages ​​(e.g., Chinese / English / Spanish / Russian, etc.). The HMI has two levels of password access: administrator and operator. Operator access is hard-locked by the hardware circuitry, preventing them from modifying or adding parameters such as the proportional gain (C), temperature compensation coefficient (K_T), and anti-condensation priority control parameters. Access management is local hardware-level locking and does not involve IoT remote access or WebVisu remote visualization functions. This invention does not advocate for IoT remote maintenance, WebVisu, or other digital functions; it is a local, independent control system focusing on local PLC adaptive control algorithms.

[0026] Secondly, this invention provides an oil-free adaptive dosing control system for a DMDC electromagnetic metering pump, comprising: An electromagnetic metering pump is used to add DMDC to the beverage material flow at a set ratio (there is no hydraulic oil transmission between the pump head and the drive mechanism of the electromagnetic metering pump). An electromagnetic flow meter (which can output 4-20 mA or pulse signals to a PLC controller) is installed in the material inlet pipeline to monitor the flow rate Q of beverage materials in real time. The multi-zone temperature monitoring module includes temperature sensors installed in the DMDC storage bottle, buffer tank, pump head, and nozzle pipeline to acquire the DMDC temperature T_liquid and pump head temperature T_pumphead in real time. Pressure sensor, located at the mouth of DMDC reservoir and / or the top of buffer tank; The multi-zone heating module includes an upper cabinet heater, a lower cabinet left heater, a lower cabinet right heater, and a nozzle pipeline heater. Each zone is independently controllable, and the total heating power is allocated according to the priority of preventing solidification. The PLC controller (which may not integrate an IoT gateway and remote maintenance function) has a built-in three-dimensional adaptive compensation model for temperature-flow-stroke frequency and is electrically connected to electromagnetic metering pumps, electromagnetic flowmeters, multi-zone temperature monitoring modules and multi-zone heating modules. The metering calibration module, including the metering tube and the liquid level sensor, is used for closed-loop feedback calibration of the actual DMDC discharge volume. The local human-machine interface module is electrically connected to the PLC controller and is used for parameter setting, status display and access control. The PLC controller is configured to execute the oil-free adaptive addition control method for the DMDC electromagnetic metering pump as described in the first aspect.

[0027] In this invention, the lower cabinet is further divided into lower cabinet left and lower cabinet right, with lower cabinet left heater and lower cabinet right heater respectively installed, corresponding to the lower cabinet left heating zone and lower cabinet right heating zone. This forms a four-zone independent temperature control (upper cabinet / lower cabinet left / lower cabinet right / sprayer pipe) + anti-condensation priority algorithm.

[0028] Compared with the prior art, the beneficial effects of this invention are as follows: This invention establishes a three-dimensional compensation model of temperature-flow rate-stroke frequency, utilizing precise physical property parameters of DMDC under normal pressure (viscosity 2.1 mPa·s at 20℃, density 1.25 g / cm³). 3 This invention solves the metering drift problem caused by the temperature-viscosity change of DMDC in electromagnetic metering pumps under oil-free conditions, achieving high-precision online addition within the full flow range of 3-18 T / H and the ambient temperature of 4-35℃, with an addition error of ≤±5%. It also completely eliminates the hydraulic oil system, avoiding the need for hydraulic pumps and remote maintenance technology. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the overall structure of an oil-free adaptive addition control system for a DMDC electromagnetic metering pump according to the present invention.

[0030] Figure 2 This invention presents a control logic block diagram of a three-dimensional adaptive compensation model for temperature-flow-stroke frequency in a DMDC electromagnetic metering pump, which is described as an oil-free adaptive addition control method and a system thereof. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Operating methods not specifically specified in the following embodiments are generally performed under conventional conditions or as recommended by the manufacturer.

[0032] See Figure 1 An oil-free adaptive addition control system for a DMDC electromagnetic metering pump includes an electromagnetic metering pump 1 (oil-free electromagnetically driven diaphragm pump), a general-purpose electromagnetic flowmeter 2 (outputting 4-20mA or pulse signals), a multi-zone temperature monitoring module 3 (containing multiple PT100 probes), a pressure sensor, a multi-zone heating module 4 (containing a 250W heater in the upper cabinet, a 400W heater in the left lower cabinet, a 400W heater in the right lower cabinet, and a 70W heater in the nozzle pipeline), a PLC controller 5 (with a built-in three-dimensional adaptive compensation algorithm), a metering calibration module 6 (containing a metering tube and a liquid level sensor), and a local human-machine interface module 7.

[0033] The electromagnetic metering pump 1 is used to add DMDC to the beverage material flow at a set ratio (there is no hydraulic oil transmission between the pump head and the drive mechanism of the electromagnetic metering pump).

[0034] Electromagnetic flow meter 2 (which can output 4-20 mA or pulse signals to the PLC controller) is installed on the material inlet pipeline to monitor the flow rate Q of beverage materials in real time.

[0035] The multi-zone temperature monitoring module 3 includes temperature sensors installed in the DMDC storage bottle, buffer tank, pump head, and nozzle pipeline to acquire the DMDC temperature T_liquid and the pump head temperature T_pumphead in real time.

[0036] The pressure sensor is located at the mouth of the DMDC reservoir and / or the top of the buffer tank.

[0037] The multi-zone heating module 4 includes an upper cabinet heater, a lower cabinet left heater, a lower cabinet right heater, and a nozzle pipeline heater. Each zone is independently controllable, and the total heating power is allocated according to the priority of preventing solidification.

[0038] PLC controller 5 (which may not integrate IoT gateway and remote maintenance function) has a built-in three-dimensional adaptive compensation model of temperature-flow-stroke frequency, and is electrically connected to electromagnetic metering pump 1, electromagnetic flowmeter 2, multi-zone temperature monitoring module 3, multi-zone heating module 4, metering calibration module 6 and local human-machine interface module 7.

[0039] The metering calibration module 6 includes a metering tube and a liquid level sensor, which are used for closed-loop feedback calibration of the actual DMDC discharge volume.

[0040] The local human-machine interface module 7 is electrically connected to the PLC controller 5 and is used for parameter setting, status display and access control.

[0041] PLC controller 5 is configured to execute the DMDC electromagnetic metering pump oil-free adaptive addition control method.

[0042] The oil-free adaptive addition control method for DMDC electromagnetic metering pumps includes: The equipment cabinet includes an upper cabinet and a lower cabinet. The lower cabinet is further divided into lower cabinet left and lower cabinet right, each equipped with a lower cabinet left heater and a lower cabinet right heater, corresponding to the lower cabinet left heating zone and lower cabinet right heating zone, respectively. This enables four-zone independent temperature control (upper cabinet / lower cabinet left / lower cabinet right / sprayer pipe) + anti-coagulation priority algorithm. The lower cabinet houses a DMDC storage bottle, which is connected to a buffer tank via piping and control valves. A multi-zone heating module is constructed, including the upper cabinet heating zone, lower cabinet left heating zone, lower cabinet right heating zone, and sprayer pipe heating zone. Each zone has independent PID temperature control (ensuring uniform DMDC temperature and above the freezing point), so that the DMDC storage liquid temperature T_liquid reaches the preset operating temperature range [T_min, T_max], where T_min≥20℃ and T_max≤30℃. The sprayer pipe is connected to an electromagnetic metering pump to deliver DMDC for mixing with the beverage material flow.

[0043] The flow rate Q of beverage materials is acquired in real time and the flow rate signal is transmitted to the PLC controller.

[0044] Based on the real-time T_liquid, the density ρ(T) and dynamic viscosity μ(T) of DMDC at the current temperature are dynamically calculated using a built-in property parameter lookup table or an Arrhenius-type fitting formula. The dynamic viscosity μ(T) of DMDC in the 17-30℃ range is calculated using the formula μ(T) = μ_20·exp[-k_μ·(T-20)], where μ_20 = 2.1 mPa·s (reference viscosity at 20℃) and k_μ = 0.035 / ℃ (temperature sensitivity coefficient). The fitting error of this formula in the 17-30℃ range is <±3%, and it is obtained by regression analysis using the Arrhenius model based on 6 measured viscosity data points of DMDC in the 17-30℃ range (directly derived from the Arrhenius-type viscosity temperature dependence law of DMDC carbonate compounds). The density ρ(T) is in g / cm³. 3 The linear formula ρ(T) = 1.25 - 0.0012·(T-20) is used for calculation.

[0045] Based on the set addition ratio C (unit: mL / kL, corresponding to 50-250 ppm) and material flow rate Q, calculate the theoretically required DMDC volumetric flow rate q_DMDC=C·Q / 1000, where C is in mL / kL, Q is in L / h, and q_DMDC is in mL / h. Based on the theoretical single-stroke displacement V_stroke_0 of the electromagnetic metering pump (calibrated by the pump manufacturer, such as 0.5 mL / stroke), calculate the initial stroke frequency f_0=q_DMDC / V_stroke_0.

[0046] The PLC controller invokes a three-dimensional adaptive compensation model based on temperature, flow rate, and stroke frequency to correct the initial stroke frequency f_0, obtaining the actual output stroke frequency f_out = f_0·K_T·K_Q·K_η; where K_T is the temperature compensation coefficient, K_Q is the flow rate compensation coefficient, and K_η is the pump efficiency compensation coefficient. The temperature compensation coefficient K_T considers the effects of density and viscosity changes on pump volumetric efficiency, based on the linear decrease of DMDC density with temperature (temperature coefficient -0.0012 g / (cm³)). 3 The law of viscosity decreasing with temperature (℃) was established; the flow compensation coefficient K_Q was nonlinearly corrected for low flow conditions (<6 T / H); the pump efficiency compensation coefficient K_η was corrected for aging and thermal drift based on the cumulative stroke count and pump head temperature.

[0047] The temperature compensation coefficient K_T is calculated using the following formula: K_T=[ρ(T_0) / ρ(T)]·[μ(T) / μ(T_0)]^α, where T_0=20℃ is the reference temperature, and ρ(T_0)=1.25 g / cm³. 3μ(T_0) = 2.1 mPa·s, where α is the viscosity influence weighting coefficient, ranging from 0.4 to 0.6. The above formula is based on the experimental law that the dynamic viscosity of the DMDC at normal pressure decreases exponentially with temperature, while the density decreases linearly with temperature. The effect of viscosity change on the volumetric efficiency of the electromagnetic metering pump is much greater than that of density change. The weighting coefficient α is set to 0.4-0.6 to reflect the dominant role of viscosity in the total compensation. When T > 20℃, K_T < 1 (frequency reduction); when T < 20℃, K_T > 1 (frequency increase).

[0048] The flow rate compensation coefficient K_Q is set according to a continuous piecewise function: when Q≥6000 L / h, K_Q=1.0; when Q<6000 L / h, K_Q=1.0+β·(6000-Q) / 6000. β is determined by experimental fitting to ensure continuity. At the same time, the stroke length of the electromagnetic metering pump is shortened to 50%-70% of the rated value, and the PWM response frequency is increased to 130%-150% of the rated value to maintain metering accuracy.

[0049] This invention can use software for automatic stroke verification and touch screen input of set values, with the PLC controller automatically calculating and performing the verification.

[0050] The pump efficiency compensation coefficient K_η is adjusted for aging based on the cumulative number of strokes N_stroke and the pump head temperature T_pumphead of the electromagnetic metering pump: K_η=1-γ·ln(1+N_stroke / N_0)-δ·|T_pumphead–T_opt|, where N_0 is the baseline life (the example value can be 1×10). 6 The pump head aging coefficients are: γ (e.g., stroke), δ (e.g., temperature deviation coefficient), and T_opt (e.g., optimal pump head operating temperature). K_η is required to be ≥ 0.5. When K_η < the warning value, a pump head aging warning is triggered, prompting maintenance personnel to check diaphragm wear and / or spring fatigue. The warning value can be 0.85, corresponding to a pump efficiency decrease of approximately 15%, at which point the single-stroke displacement deviation will exceed the compensable range.

[0051] The PLC controller outputs the corrected stroke frequency f_out and duty cycle D to the electromagnetic metering pump drive module, driving the pump head to execute precise strokes in an oil-free manner (no hydraulic oil is required between the electromagnetic metering pump head and the drive mechanism); the electromagnetic metering pump drive module uses PWM chopper drive or constant current chopper drive. This invention adopts an oil-free electromagnetic metering pump solution, which can completely eliminate the hydraulic oil system.

[0052] The actual DMDC volume q_actual discharged per unit time is monitored in real time, and the deviation Δq = q_actual - q_DMDC is calculated. If |Δq / q_DMDC| > the preset threshold ε (ε = 3%-8%, preferably 5%), the system returns to step S5 for correction. The correction method is to multiply each of the original K_T, K_Q, and K_η by λ = 1 + Δq / q_DMDC. If the deviation still exceeds the limit after N consecutive corrections (N≥3), an alarm is triggered and the machine is stopped to prevent over- or under-addition. This invention uses software automatic verification, with the PLC automatically calculating the number of strokes and performing the verification, eliminating the need for manual counting of 10 strokes.

[0053] Combination Figure 2 The model inputs include DMDC storage liquid temperature (T_liquid, from the multi-zone temperature monitoring module), material flow rate (Q, from the electromagnetic flowmeter), cumulative number of running strokes (N_stroke, from the PLC counter), and pump head temperature (T_pumphead, from the pump head temperature probe). The intermediate processing utilizes a physical property parameter calculation module (including ρ(T), μ(T) lookup tables), a three-dimensional compensation module (including K_T, K_Q, K_η calculations), and a PWM generation module. The model outputs include f_out and D (duty cycle), which are transmitted to the electromagnetic metering pump drive module (electromagnetic metering pump 1). The electromagnetic metering pump drive module (electromagnetic metering pump 1), in conjunction with the metering verification module 6 (metering tube and level sensor), provides feedback q_actual for further deviation calculation. If the deviation calculation result exceeds the threshold (5%), the compensation coefficient is recalculated and corrected, and this is recorded as one correction. After correction, the deviation is recalculated and it is determined whether it exceeds the threshold. This deviation calculation-judgment-correction process is repeated. If the deviation still exceeds the limit after three consecutive corrections, an alarm is triggered and the machine is shut down.

[0054] Abnormal Condition Anti-condensation Priority Control: When the ambient temperature T_amb≤15℃ or 18℃≤T_liquid<20℃, the PLC controller prioritizes increasing the power of the nozzle pipeline heating zone to exceed the rated power (e.g., 120% of the rated power). The upper cabinet heating zone, lower cabinet left heating zone, and lower cabinet right heating zone heat at the rated power, and can selectively (either reduce or not reduce) reduce the stroke frequency f_out to 60%-80% of the normal value; when 17℃≤T_liquid<18℃, the PLC controller... The system prioritizes increasing the power of the nozzle heating zone to over 120% of its rated power, with the power of the lower left and right heating zones at 105%-115% (e.g., 110%) of their rated power, and the power of the upper heating zone at 70%-100% (e.g., 80%) of its rated power. It also reduces the stroke frequency f_out to 60%-80% of its normal value (to extend the residence time of the DMDC in the pipeline and ensure sufficient preheating, preventing crystallization and blockage at the nozzles). When T_liquid < 17℃, the system is forced to shut down and triggers a low-temperature alarm. When the ambient temperature drops sharply or the DMDC temperature approaches its freezing point, the PLC controller activates a priority strategy, prioritizing the heating power of the nozzle pipeline and, if necessary, reducing the stroke frequency to extend the preheating time, fundamentally preventing nozzle crystallization and blockage.

[0055] The temperature setpoints for each zone of the multi-zone heating module are automatically prioritized according to anti-freezing priority: the target temperature for the nozzle pipeline heating zone is T_set_nozzle = 28±2℃, the target temperatures for the lower left and right heating zones are T_set_lower = 24±2℃, and the target temperature for the upper heating zone is T_set_upper = 22±2℃. When the total heating power is limited, the PLC controller allocates power according to the priority of T_set_nozzle > T_set_lower > T_set_upper to ensure that the DMDC temperature at the nozzle is always more than 10℃ higher than the freezing point of 17℃. This priority strategy is based on the fluid dynamics characteristics of DMDC, where the viscosity increases sharply and the flow resistance increases near 17℃.

[0056] The electromagnetic metering pump drive module has an adjustable drive frequency of 10-200 Hz and an adjustable duty cycle D of 20%-95%.

[0057] The electromagnetic metering pump is either an electromagnetically driven diaphragm pump or an electromagnetically driven plunger pump. The pump head uses a PTFE diaphragm or ceramic plunger, and the parts in contact with the DMDC are made of 316L stainless steel or Hastelloy C-276. This oil-free drive completely eliminates the hydraulic oil transmission system, avoiding the risk of hydraulic oil leakage contaminating the DMDC or beverages. The PLC controller outputs a PWM signal to drive the electromagnetic metering pump, and the electromagnet directly drives the diaphragm or plunger to reciprocate, eliminating the need for hydraulic oil as a force transmission medium.

[0058] The oil-free adaptive addition control method for the DMDC electromagnetic metering pump also includes a DMDC storage bottle internal pressure monitoring and adaptive suction control step: A pressure sensor installed at the DMDC storage bottle opening and / or the top of the buffer tank monitors the internal pressure P_bottle in real time. When P_bottle > 0.05 MPa gauge pressure, the PLC controller extends the intermittent compressed air suction interval to 1.5-2 times the normal value to prevent DMDC leakage due to full bottle pressure. When P_bottle < -0.02 MPa gauge pressure, the suction interval is shortened to 0.5-0.7 times the normal value to prevent excessive negative pressure from causing the electromagnetic metering pump to run dry and cavitate. 0.05 MPa corresponds to 80% of the rated pressure of the storage bottle, and -0.02 MPa corresponds to the minimum allowable suction pressure of the pump head. The above adaptive suction control does not require a dedicated 6-pin interface and K2 Bottle Change pin definition. This invention can use a domestically produced general-purpose RS485 / Modbus or dry contact interface.

[0059] The oil-free adaptive addition control method for the DMDC electromagnetic metering pump also includes a safety redundancy control step based on DMDC decomposition kinetics: the PLC controller calculates the DMDC decomposition rate η_decomp=1-exp(-k_d·t_residence) according to the first-order decomposition kinetic model based on the real-time T_liquid and the residence time t_residence of DMDC in the buffer tank, where k_d is the temperature-dependent decomposition rate constant, k_d=k_d(20)·exp[-Ea / R·(1 / T-1 / 293.15)], and k_d(20) represents the decomposition rate constant at 20℃ (approximately 0.012 h). -1 Ea represents the empirical value of the decomposition activation energy parameter, R represents the molar gas constant, and T represents the temperature. When η_decomp > the preset warning value (e.g., 8%), a DMDC activity decay warning is triggered, prompting the operator to replace the storage solution or shorten the replenishment cycle. The decomposition kinetic parameters can be established based on the thermodynamic stability data of the DMDC at atmospheric pressure with a vapor pressure of 0.7 hPa (20℃).

[0060] The PLC controller has a built-in local touchscreen HMI that supports multiple languages ​​(e.g., Chinese / English / Spanish / Russian, etc.). The HMI has two levels of password access: administrator and operator. Operator access is hardware-locked, preventing modification or addition of parameters such as the proportional gain (C), temperature compensation coefficient (K_T), and anti-condensation priority control parameters. Access management is local hardware-level locking and does not involve IoT remote access or WebVisu remote visualization functions. This invention does not advocate for IoT remote maintenance or WebVisu and is a local, independent control system focusing on local PLC adaptive control algorithms.

[0061] Example 1: Standard operating conditions (ambient temperature 20℃, material flow rate 10 T / H, set addition amount 200 mL / kL) After system startup, the multi-zone heating module operates, stabilizing the DMDC liquid temperature T_liquid at 22℃ within 15 minutes. The material flow rate measured by the general-purpose electromagnetic flowmeter is Q = 10000 L / h. The PLC calls the physical property parameter module: based on the DMDC atmospheric pressure physical property data, ρ(22℃) = 1.25 - 0.0012 × (22 - 20) = 1.2476 g / cm³. 3 μ(22℃) = 2.1 × exp[-0.035 × (22-20)] = 2.1 × 0.9324 = 1.96 mPa·s. Setting the addition ratio C = 200 mL / kL, then q_DMDC = 200 × 10000 / 1000 = 2000 mL / h. The single-stroke displacement of the electromagnetic metering pump is V_stroke_0 = 0.5 mL, therefore f_0 = 2000 / 0.5 = 4000 strokes / h = 66.7 strokes / min.

[0062] Entering 3D compensation: Reference temperature T_0 = 20℃, ρ_0 = 1.25 g / cm³ 3 μ_0 = 2.1 mPa·s. α is taken as 0.5. K_T = (1.25 / 1.2476) × (1.96 / 2.1)^0.5 = 1.0019 × 0.966 = 0.968. Q = 10000 L / h ≥ 6000 L / h, therefore K_Q = 1.0. Cumulative stroke count N_stroke = 5 × 10 5 Pump head temperature T_pumphead=24℃, γ=0.03, δ=0.01, T_opt=25℃. K_η=1-0.03×ln(1+0.5)-0.01×|24-25|=1-0.03×0.405-0.01=0.978. Final f_out=66.7×0.968×1.0×0.978=63.1 strokes / min. The PLC outputs a PWM signal with a duty cycle D=65%, driving the electromagnetic metering pump to run at 63.1 strokes / min.

[0063] After running for 30 minutes, the metering tube level sensor reported an actual discharge volume of q_actual = 1985 mL / h, with a deviation of Δq = (1985-2000) / 2000 = -0.75%, which is within ±5%. The system maintains the current parameters.

[0064] Example 2: Low temperature operation (ambient temperature 8°C, material flow rate 4 T / H, set addition amount 200 mL / kL) The ambient temperature is 8℃. The lower cabinet heating zone operates at full power (400 W × 2), and the nozzle piping heating zone operates at 120% of its rated power (70 W) = 84 W (priority increased). The T_liquid reaches 19℃ after 20 minutes of preheating. Q = 4000 L / h, which is in the low flow range. β = 0.1, K_Q = 1.0 + 0.1 × (6000 - 4000) / 6000 = 1.033. μ(19℃) = 2.1 × exp[-0.035 × (19 - 20)] = 2.1 × 1.0356 = 2.17 mPa·s, ρ(19℃) = 1.25 - 0.0012 × (-1) = 1.2512 g / cm³. 3 K_T = (1.25 / 1.2512) × (2.17 / 2.1)^0.5 = 0.9990 × 1.016 = 1.015. f_0 = 2000 / 0.5 = 4000 strokes / h. f_out = 4000 × 1.015 × 1.033 × 0.98 = 4110 strokes / h.

[0065] Simultaneously, the PLC activates an anti-solidification priority strategy: since T_liquid=19℃ is close to the freezing point of 17℃, the stroke frequency is reduced to 75% of the normal value, i.e., the actual output frequency f_out_prime=4110×0.75=3082.5 strokes / h=51.4 strokes / min. The stroke length is simultaneously shortened to 60% of the rated value, and the PWM frequency is increased to 120 Hz, ensuring that the single-stroke displacement is reduced but the response speed is increased, maintaining metering accuracy. This embodiment verifies that the present invention can still maintain ±5% accuracy at critical temperatures close to the DMDC freezing point through a multi-zone priority heating + frequency reduction and heat preservation strategy.

[0066] Example 3: High-temperature aging conditions (ambient temperature 30℃, cumulative operation of 20 million strokes) Total number of strokes N_stroke = 2 × 10 7 The pump head temperature has exceeded the standard maintenance threshold of 15 million strokes. T_pumphead = 28℃. K_η = 1 - 0.04 × ln(1 + 20) - 0.01 × |28 - 25| = 1 - 0.04 × 3.045 - 0.03 = 0.848. The PLC detects K_η = 0.848 < 0.85, triggering a pump head aging warning and prompting maintenance personnel to check for diaphragm wear and spring fatigue. However, the system continues to run, ensuring accuracy by increasing f_out to compensate for efficiency degradation. This embodiment verifies that the aging correction function of the pump efficiency compensation coefficient K_η can maintain accuracy even after exceeding the standard maintenance cycle, extending the actual service life of the electromagnetic metering pump and reducing maintenance frequency.

[0067] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A method for oil-free adaptive metering control of a DMDC electromagnetic metering pump, characterized in that, Including the following steps: S1. Provide equipment cabinets, including upper and lower cabinets. The lower cabinet houses a DMDC liquid storage bottle, which is connected to a buffer tank via pipelines and control valves. Construct a multi-zone heating module, including an upper cabinet heating zone, a lower cabinet left heating zone, a lower cabinet right heating zone, and a nozzle pipeline heating zone. Each zone has independent PID temperature control to ensure that the DMDC liquid storage temperature T_liquid reaches the preset operating temperature range [T_min, T_max], where T_min≥20℃ and T_max≤30℃. S2. Real-time acquisition of beverage material flow rate Q, and transmission of the flow signal to the PLC controller; S3. Based on the real-time T_liquid, dynamically calculate the DMDC density ρ(T) and dynamic viscosity μ(T) at the current temperature using the built-in property parameter lookup table or an Arrhenius-type fitting formula. The dynamic viscosity μ(T) of DMDC in the 17-30℃ range is calculated using the formula μ(T) = μ_20·exp[-k_μ·(T-20)], where μ_20 = 2.1 mPa·s and k_μ = 0.035 / ℃. The fitting error of this formula in the 17-30℃ range is <±3%, and it is obtained by regression analysis using the Arrhenius model based on 6 measured viscosity data points of DMDC in the 17-30℃ range. The density ρ(T) is in g / cm³. 3 Calculated using the linear formula ρ(T) = 1.25 - 0.0012·(T-20); S4. Based on the set addition ratio C and material flow rate Q, calculate the theoretical required DMDC volumetric flow rate q_DMDC=C·Q / 1000, where C is in mL / kL, Q is in L / h, and q_DMDC is in mL / h. Based on the theoretical single-stroke displacement V_stroke_0 of the electromagnetic metering pump, calculate the initial stroke frequency f_0=q_DMDC / V_stroke_0. S5, the PLC controller calls the temperature-flow-stroke frequency three-dimensional adaptive compensation model to correct the initial stroke frequency f_0, and obtain the actual output stroke frequency f_out=f_0·K_T·K_Q·K_η; where K_T is the temperature compensation coefficient, K_Q is the flow condition compensation coefficient, and K_η is the pump efficiency compensation coefficient. S6, the PLC controller outputs the corrected stroke frequency f_out and duty cycle D to the electromagnetic metering pump drive module, driving the pump head to perform precise strokes in an oil-free manner; the electromagnetic metering pump drive module adopts PWM chopper drive or constant current chopper drive. S7. Monitor the actual DMDC volume q_actual discharged per unit time in real time, and calculate the deviation Δq=q_actual-q_DMDC; if |Δq / q_DMDC|>the preset threshold ε (ε=3%-8%, preferably 5%), then return to S5 for correction. The correction method is to multiply each of the original K_T, K_Q, and K_η by λ=1+Δq / q_DMDC; if the deviation still exceeds the limit after N consecutive corrections (N≥3), then trigger an alarm and shut down the machine. S8. Priority Control for Preventing Condensation in Abnormal Conditions: When the ambient temperature T_amb ≤ 15℃ or 18℃ ≤ T_liquid < 20℃, the PLC controller prioritizes increasing the power of the nozzle pipeline heating zone to above the rated power. The upper cabinet heating zone, lower cabinet left heating zone, and lower cabinet right heating zone are heated at the rated power, and the stroke frequency f_out can be selectively reduced to 60%-80% of the normal value. When 17℃ ≤ T_liquid < 18℃, the PLC controller prioritizes increasing the power of the nozzle pipeline heating zone to above 120% of the rated power. The power of the lower cabinet left heating zone and lower cabinet right heating zone is 105%-115% of the rated power, and the power of the upper cabinet heating zone is 70%-100% of the rated power. The stroke frequency f_out is reduced to 60%-80% of the normal value. When T_liquid < 17℃, the machine is forcibly shut down and a low-temperature alarm is triggered.

2. The oil-free adaptive addition control method for the DMDC electromagnetic metering pump according to claim 1, characterized in that, The temperature compensation coefficient K_T is calculated using the following formula: K_T=[ρ(T_0) / ρ(T)]·[μ(T) / μ(T_0)]^α, where T_0=20℃ is the reference temperature, and ρ(T_0)=1.25 g / cm³. 3 μ(T_0) = 2.1 mPa·s, where α is the viscosity influence weighting coefficient, with a value of 0.4-0.

6.

3. The oil-free adaptive addition control method for the DMDC electromagnetic metering pump according to claim 1, characterized in that, The flow rate compensation coefficient K_Q is set according to a continuous piecewise function: when Q≥6000 L / h, K_Q=1.0; when Q<6000 L / h, K_Q=1.0+β·(6000-Q) / 6000. β is determined by experimental fitting to ensure continuity. At the same time, the stroke length of the electromagnetic metering pump is shortened to 50%-70% of the rated value, and the PWM response frequency is increased to 130%-150% of the rated value to maintain metering accuracy.

4. The oil-free adaptive addition control method for the DMDC electromagnetic metering pump according to claim 1, characterized in that, The pump efficiency compensation coefficient K_η is adjusted for aging based on the cumulative number of strokes N_stroke and the pump head temperature T_pumphead of the electromagnetic metering pump: K_η=1-γ·ln(1+N_stroke / N_0)-δ·|T_pumphead–T_opt|, where N_0 is the reference life, γ is the stroke aging coefficient, δ is the temperature deviation coefficient, and T_opt is the optimal operating temperature of the pump head; K_η is required to be ≥0.5; when K_η<the warning value, the pump head aging warning is triggered, prompting maintenance personnel to check diaphragm wear and / or spring fatigue.

5. The oil-free adaptive addition control method for the DMDC electromagnetic metering pump according to claim 1, characterized in that, The temperature settings of each zone in the multi-zone heating module are automatically sorted according to the priority of anti-condensation: the target temperature of the nozzle pipeline heating zone is T_set_nozzle=28±2℃, the target temperature of the lower cabinet left and lower cabinet right heating zones is T_set_lower=24±2℃, and the target temperature of the upper cabinet heating zone is T_set_upper=22±2℃. When the total heating power is limited, the PLC controller allocates power according to the priority of T_set_nozzle>T_set_lower>T_set_upper to ensure that the DMDC temperature at the nozzle is always more than 10℃ higher than the freezing point of 17℃.

6. The oil-free adaptive addition control method for the DMDC electromagnetic metering pump according to claim 1, characterized in that, The electromagnetic metering pump drive module has an adjustable drive frequency of 10-200 Hz and an adjustable duty cycle D of 20%-95%. The electromagnetic metering pump is an electromagnetically driven diaphragm pump or an electromagnetically driven plunger pump. The pump head uses a PTFE diaphragm or a ceramic plunger, and the pump head and the contact parts with the DMDC are made of 316L stainless steel or Hastelloy C-276.

7. The oil-free adaptive addition control method for the DMDC electromagnetic metering pump according to claim 1, characterized in that, The oil-free adaptive addition control method for the DMDC electromagnetic metering pump also includes a step of monitoring the gas pressure inside the DMDC storage bottle and adaptive suction control: The pressure sensor installed at the DMDC storage bottle opening and / or the top of the buffer tank monitors the bottle pressure P_bottle in real time; when P_bottle > 0.05 MPa gauge pressure, the PLC controller extends the intermittent suction interval of compressed air to 1.5-2 times the normal value to prevent DMDC leakage due to full bottle pressure; when P_bottle < -0.02 MPa gauge pressure, the suction interval is shortened to 0.5-0.7 times the normal value to prevent excessive negative pressure from causing the electromagnetic metering pump to run dry and cavitate.

8. The oil-free adaptive addition control method for the DMDC electromagnetic metering pump according to claim 1, characterized in that, The oil-free adaptive addition control method for the DMDC electromagnetic metering pump also includes a safety redundancy control step based on DMDC decomposition kinetics: The PLC controller calculates the DMDC decomposition rate η_decomp=1-exp(-k_d·t_residence) according to the first-order decomposition kinetic model based on the real-time T_liquid and the residence time t_residence of DMDC in the buffer tank. Here, k_d is the temperature-dependent decomposition rate constant, k_d=k_d(20)·exp[-Ea / R·(1 / T-1 / 293.15)], k_d(20) represents the decomposition rate constant at 20℃, Ea represents the empirical value of the decomposition activation energy parameter, R represents the molar gas constant, and T represents the temperature. When η_decomp>the preset reminder value, a DMDC activity decay warning is triggered, prompting the operator to replace the storage liquid or shorten the replenishment cycle.

9. The oil-free adaptive addition control method for DMDC electromagnetic metering pumps according to claim 1, characterized in that, The PLC controller has a built-in local touch screen human-machine interface that supports multiple languages. The human-machine interface has two levels of password permissions: administrator and operator. The operator's permissions are hard-locked by the hardware circuit and they do not have the right to modify or add proportional C, temperature compensation coefficient K_T, and anti-condensation priority control parameters. The permission management is local hardware-level locked and does not involve IoT remote access or WebVisu remote visualization functions.

10. A DMDC electromagnetic metering pump oil-free adaptive dosing control system, characterized in that, include: An electromagnetic metering pump is used to add DMDC to the beverage material stream at a set ratio. An electromagnetic flow meter is installed in the material inlet pipeline to monitor the flow rate Q of beverage materials in real time. The multi-zone temperature monitoring module includes temperature sensors installed in the DMDC storage bottle, buffer tank, pump head, and nozzle pipeline to acquire the DMDC temperature T_liquid and pump head temperature T_pumphead in real time. Pressure sensor, located at the mouth of DMDC reservoir and / or the top of buffer tank; The multi-zone heating module includes an upper cabinet heater, a lower cabinet left heater, a lower cabinet right heater, and a nozzle pipeline heater. Each zone is independently controllable, and the total heating power is allocated according to the priority of preventing solidification. The PLC controller has a built-in three-dimensional adaptive compensation model for temperature, flow rate and stroke frequency, and is electrically connected to the electromagnetic metering pump, electromagnetic flow meter, multi-zone temperature monitoring module and multi-zone heating module. The metering calibration module, including the metering tube and the liquid level sensor, is used for closed-loop feedback calibration of the actual DMDC discharge volume. The local human-machine interface module is electrically connected to the PLC controller and is used for parameter setting, status display and access control. The PLC controller is configured to perform the oil-free adaptive addition control method for the DMDC electromagnetic metering pump as described in any one of claims 1-9.

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