Operating pressure protection system for a digital metering pump

Abstract

The application provides a running pressure protection system of a digital metering pump, comprising a power acquisition unit, a data processing unit, an algorithm compensation unit, a BLDC driving unit and a flow rate and rotating speed control unit, wherein the voltage, current, power and other electric parameters of motor operation are acquired by the power acquisition unit, the multivariable power-pressure mapping model is established by the algorithm compensation unit after the filtering and solving of the data processing unit, the outlet pressure is calculated in real time, and the overpressure / underpressure grading protection and load dynamic adjustment are executed accordingly, so that the voltage, current and power parameters deeply participate in the algorithm compensation, and the pressure safety protection and stable and accurate operation of the digital metering pump are realized under the condition of no pressure sensor.

Description

Technical Field

[0001] This invention relates to the fields of fluid metering and conveying equipment, intelligent control of brushless DC motors (BLDC), and soft measurement technology. Specifically, it relates to an operating pressure protection system for a digital metering pump, which can realize real-time estimation of outlet pressure, overpressure / underpressure protection, and dynamic load adjustment without relying on traditional pressure sensors. It is suitable for pumping scenarios that require pressure safety protection and accurate metering, such as chemical dosing, water treatment, petrochemicals, and food and beverage. Background Technology

[0002] During operation, the outlet pipeline pressure of a digital metering pump is a critical parameter related to equipment safety and process stability. Excessive outlet pressure can lead to pipeline rupture, seal failure, pump head damage, or even motor overload and burnout; conversely, insufficient outlet pressure or abnormal power may indicate pipeline leakage, pump chamber lack of fluid (dry running), or check valve failure. Therefore, pressure protection is an indispensable function of the metering pump control system.

[0003] In existing technologies, pressure protection for metering pumps mainly adopts the following schemes: Scheme 1: External pressure sensor. A mechanical pressure switch or electronic pressure transmitter is installed on the pump outlet pipeline, and the pressure signal is connected to the controller for threshold judgment. This scheme has high measurement accuracy, but has the following drawbacks: 1) Increased hardware cost and installation complexity; 2) The pressure sensor is in direct contact with the process medium, and is easily damaged or blocked in corrosive, high-viscosity, or particulate media, resulting in poor reliability; 3) Sensor cables are susceptible to electromagnetic interference in industrial environments, and this increases the risk of leakage; 4) Regular calibration and maintenance are required. Scheme 2: Motor overcurrent protection. Overload is indirectly determined by detecting whether the motor current exceeds a threshold, and the drive is cut off when the current exceeds the limit. This solution only provides basic "overcurrent stop" protection and has the following drawbacks: 1) Current and pressure are not linearly correlated, and are affected by multiple factors such as grid voltage fluctuations, motor temperature, and speed changes, resulting in a high false alarm rate; 2) It cannot distinguish between actual overpressure and instantaneous load fluctuations; 3) It can only provide shutdown protection and cannot perform gradual load adjustment; 4) It cannot detect low-voltage faults such as undervoltage, idling, and leakage. Solution 3: Inverter power protection. Some inverter drives have power monitoring functions, but these are only used for general motor protection and do not establish a power-pressure mapping model for the volumetric load characteristics of metering pumps. Therefore, they cannot output accurate pressure estimates or achieve pressure closed-loop and flow coordinated control.

[0004] In summary, existing technologies share the following common shortcomings: (1) It relies on hardware pressure sensors, which are costly, have poor reliability, and limited media compatibility; (2) Simple overcurrent protection has low accuracy and cannot distinguish the influence of pressure and other factors on current; (3) Lack of a pressure soft measurement model that integrates multiple parameters such as voltage, current, and power; (4) The protection measures are limited (mainly shutdown), lacking graded derating and dynamic load adjustment; (5) It cannot simultaneously detect multiple faults such as overpressure, underpressure, idling, and leakage; (6) The calculated pressure was not included in the flow metering compensation, resulting in a decrease in metering accuracy when the pressure changes.

[0005] Therefore, there is an urgent need for a digital metering pump operating pressure protection system that is based on soft measurement of motor power, requires no additional pressure sensor, can accurately calculate outlet pressure, and achieve graded protection and load optimization. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a pressure protection system for a digital metering pump. The system acquires electrical parameters such as voltage, current, and power of the motor through a power acquisition unit. After filtering and calculation by a data processing unit, an algorithm compensation unit establishes a multivariable power-pressure mapping model (soft measurement) to calculate the outlet pressure in real time. Based on this, it performs overpressure / underpressure graded protection and dynamic load adjustment, so that voltage, current, and power parameters are deeply involved in algorithm compensation. This enables pressure safety protection and stable and accurate operation of the digital metering pump without a pressure sensor.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a digital metering pump operating pressure protection system, comprising a power acquisition unit, a data processing unit, an algorithm compensation unit, a BLDC drive unit, and a flow rate and speed control unit: (1) Power acquisition unit: A bus voltage sampling circuit (resistor voltage divider + ADC) and a phase current sampling circuit are arranged in the BLDC motor drive circuit. The bus voltage U_dc(k) and phase current I_phase(k) are synchronously acquired at a fixed sampling frequency, and the instantaneous power P_inst(k)=U_dc(k)×I_dc(k) is calculated in real time. At the same time, the sampling circuit is self-checked for open circuit, short circuit and over-range faults. (2) Data processing unit: performs digital filtering (moving average or low-pass filtering) on ​​the raw voltage and current data, calculates the active power P_active, apparent power S and power factor cosφ, removes outliers (based on power change rate threshold and 3σ criterion), calculates the power change rate dP / dt, and outputs stable power characteristic value P(k) and change rate dP / dt to the algorithm compensation unit; (3) Algorithm compensation unit: Based on power characteristic values ​​and operating status, the following algorithm logic is executed: ① Power-Pressure Mapping Model (Soft Measurement Core): Establish the outlet pressure estimation formula P_est = f(P_active, n, T_media, U_dc), where P_active is the motor active power, n is the current speed, T_media is the medium temperature (optional compensation), and U_dc is the bus voltage. The model is based on the load characteristics of a positive displacement pump: P_active = P_loss(n) + K_pump × ΔP, where P_loss(n) is the speed-related no-load loss (mechanical friction + iron loss + copper loss + hydraulic loss), K_pump is the pump's pressure-power conversion coefficient, and ΔP is the difference between the outlet pressure and the inlet pressure. The P_loss(n) curve and K_pump coefficient are obtained through factory calibration, and ΔP is calculated in real time during operation, thus obtaining the outlet pressure P_est = P_inlet + ΔP; ② Multi-parameter compensation: Voltage compensation (correcting the power reference when the power grid fluctuates), speed compensation (no-load loss is different at different speeds), temperature compensation (copper loss is affected by the change of winding resistance with temperature), and viscosity compensation (friction loss is affected by the viscosity of the medium) are performed on the power-pressure mapping to ensure the accuracy of pressure estimation. ③ Overpressure graded protection: Set multiple pressure thresholds (warning level P_warn, derating level P_derate, protection level P_limit, shutdown level P_shutdown), combine power change rate dP / dt to predict stall, and execute strategies such as alarm, speed reduction and derating, flow restriction and safe shutdown at different levels; ④ Underpressure / Idle / Leak Detection: When the estimated pressure is lower than the no-load threshold and the power is consistently low, it is determined to be idling due to lack of liquid; when the power suddenly drops and the estimated pressure drops sharply, it is determined to be a pipeline leak; the corresponding alarms and protections are triggered respectively. ⑤ Load adjustment strategy: Dynamically adjust the target speed and power limit based on the calculated pressure. When the pressure is over-pressured, smoothly reduce the speed to reduce the output flow and reduce the system pressure; when the pressure is under-pressured, appropriately increase the speed to maintain the flow, thereby achieving pressure-flow synergistic optimization. ⑥ Pressure closed-loop compensation: The calculated pressure is introduced into the flow metering correction. Since pressure changes will cause changes in volumetric efficiency (internal leakage increases with the increase of pressure difference), the actual flow calculation is corrected by the pressure compensation coefficient K_q(P) to ensure the metering accuracy under high pressure conditions. (4) BLDC drive unit: receives the drive limiting command and PWM adjustment parameters output by the algorithm compensation unit, executes three-phase inverter bridge drive, PWM duty cycle adjustment and commutation logic control, integrates hardware overcurrent and overvoltage protection, and transforms the pressure protection strategy of the algorithm layer into the actual drive behavior of the motor. (5) Flow rate and speed control unit: Receives load adjustment instructions and speed optimization instructions output by the algorithm compensation unit, and performs closed-loop speed control in combination with feedback from the grating sensor, and performs flow metering and pressure compensation correction; at the same time, it feeds back the actual speed, estimated torque, actual flow and other operating status to the algorithm compensation unit to form a closed loop.

[0008] The above five units work together to form a complete sensorless pressure protection closed-loop system, consisting of power acquisition, data processing, algorithm compensation (pressure soft measurement), drive and control, and load power feedback.

[0009] Compared with the prior art, the present invention has the following beneficial effects: (1) Sensorless pressure detection: No pressure sensor needs to be installed in the pipeline, reducing hardware costs and installation complexity, eliminating media compatibility limitations and leakage points, and improving system reliability; (2) High accuracy of multi-parameter fusion: The compensation model is established by fusing multiple parameters such as voltage, current, power, speed and temperature, which greatly improves the accuracy of pressure estimation compared with simple overcurrent protection. The typical error can be controlled within ±5%FS. (3) Graded overpressure protection: Multi-level threshold combined with power change rate prediction to achieve progressive protection from early warning, derating to safe shutdown, avoiding the impact of "overcurrent shutdown" on the process; (4) Fault types can be distinguished: It can simultaneously identify multiple types of faults such as overpressure, stall, idling, lack of liquid, and leakage, and trigger differentiated protection strategies accordingly; (5) Dynamic load optimization: Adjust the speed and power in real time according to the calculated pressure. When the pressure is over-pressured, the speed is automatically reduced and the pressure is reduced. When the pressure is under-pressured, the speed is increased and the flow is maintained, so as to achieve the optimal pressure-flow coordination. (6) Metering accuracy assurance: By compensating for volumetric efficiency through pressure, the actual flow rate is ensured to remain accurate and controllable under high pressure conditions; (7) Strong anti-interference capability: The digital filtering and multi-parameter cross-verification of the data processing unit effectively suppress power grid fluctuations and electromagnetic interference, avoiding false protection; (8) Proactive stall protection: Introducing the power change rate dP / dt, it can quickly identify and protect the motor and pump head in the early stage of stall, preventing damage to the motor and pump head. Attached Figure Description

[0010] Figure 1 This is a system topology diagram of the digital metering pump operating pressure protection algorithm described in this invention.

[0011] Explanation of each mark in the diagram: Power acquisition unit – responsible for sampling bus voltage and phase current and calculating instantaneous power; The data processing unit is responsible for electrical parameter filtering, active power calculation, and power feature extraction. Algorithm compensation unit – the core unit, responsible for generating power-pressure soft measurement, graded protection, and load adjustment strategies; BLDC drive unit – responsible for three-phase power drive and PWM control of the motor; Flow rate and speed control unit – responsible for speed closed-loop, flow rate measurement and load torque feedforward compensation; Solid arrows represent the main control signal flow, while dashed arrows represent the feedback signal flow (including load power feedback, which is the signal source for pressure soft measurement). Detailed Implementation

[0012] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0013] like Figure 1 As shown, the operating pressure protection system for the digital metering pump described in this invention comprises five parts: a power acquisition unit, a data processing unit, an algorithm compensation unit, a BLDC drive unit, and a flow rate / speed control unit. The digital metering pump (including a BLDC motor, pump head / diaphragm, and pressure / flow output) is the controlled object. The system uses the algorithm compensation unit as its core. It acquires the motor's electrical parameters through the power acquisition unit and indirectly calculates the outlet pressure using the power-pressure soft measurement model of the algorithm compensation unit, forming a closed-loop architecture of "power acquisition → data processing → pressure soft measurement → drive control → load power feedback," requiring no additional pressure sensors throughout the entire process.

[0014] 1. Power Acquisition Unit: The power acquisition unit consists of a voltage sampling circuit, a current sampling circuit, a signal conditioning circuit, and a high-precision A / D converter.

[0015] Bus voltage sampling: A precision resistor voltage divider network is used to attenuate the DC bus voltage (typically 24V / 48V / 310V) to the ADC range (0~3.3V). The voltage divider resistors are low-temperature drift type (±25ppm / ℃), followed by an RC low-pass filter and a voltage follower. The sampling resolution is ≥12 bits and the sampling frequency is ≥10kHz. Phase current sampling: A milliohm-level shunt resistor (e.g., 5mΩ / 1%) is connected in series in the lower arm of the three-phase inverter bridge, and the phase current is obtained through a differential amplifier circuit; for high current scenarios, it can be replaced with a Hall current sensor to achieve electrical isolation; DC bus current: I_dc is obtained by reconstructing the three-phase current or by sampling the resistor in series with the bus, and is used for instantaneous power calculation P_inst=U_dc×I_dc; Synchronous sampling: Voltage and current are sampled synchronously using the same dual-channel ADC to ensure phase consistency and facilitate power factor calculation; Fault self-check: During power-on and operation, the sampling voltage is checked to see if it is within a reasonable range. If it exceeds the range, a sampling fault is marked and the system enters the safety protection phase.

[0016] 2. Data Processing Unit: The data processing unit performs software-level cleaning and feature extraction on the raw electrical parameters: (1) Digital filtering: Perform first-order IIR low-pass filtering on U_dc and I_dc respectively (the cutoff frequency is configurable, typically 50~200Hz) to suppress PWM switching ripple and high-frequency noise; perform moving average filtering on the power signal (window 8~32 points).

[0017] (2) Power calculation: Instantaneous power: P_inst(k) = U_dc(k) × I_dc(k) Active power: P_active = mean(P_inst), which is the average value over one electrical cycle. Apparent power: S = U_rms × I_rms Power factor: cosφ = P_active / S (3) Outlier removal: The power change rate threshold method is adopted. If |dP / dt| > ΔP_max (typical value is 50% of rated power / 10ms), it is judged as an abnormal peak and discarded; if the continuous abnormality exceeds M times, it is judged as a sampling or drive failure.

[0018] (4) Calculation of power change rate: dP / dt = (P(k) - P(kN)) / (N·Ts), where N is the differential step size (typically 10~50), used for rapid prediction of stall and pressure change.

[0019] 3. Algorithm Compensation Unit: The algorithm compensation unit is the core of this invention. It receives P_active(k) and dP / dt output by the data processing unit, as well as the actual rotational speed n_act, estimated torque T_est, and actual flow rate Q_act fed back by the flow rate and rotational speed control unit, and executes the following algorithm: (1) Power-pressure mapping model (soft measurement): Based on the power balance principle of positive displacement metering pumps, the active power output by the motor is mainly consumed in three parts: P_active = P_loss(n, T_w) + P_hydraulic(ΔP, n) + P_other in: P_loss(n, T_w): No-load loss, including mechanical friction loss (positively correlated with rotational speed), core loss (correlated with the square of rotational speed), and winding copper loss (I²R, which varies with winding temperature T_w). P_hydraulic(ΔP, n): Hydraulic output power, which is approximately P_hydraulic = ΔP × Q / η_v for a positive displacement pump, where Q is the theoretical flow rate (proportional to the rotational speed) and η_v is the volumetric efficiency; at a fixed rotational speed, P_hydraulic is approximately linear with ΔP. P_other: Other stray losses, which can be classified as no-load losses or ignored.

[0020] At a fixed rotational speed n, the hydraulic power is linearly related to the pressure difference ΔP: P_active = P_loss(n) + K × ΔP Where K = V_stroke × n / (60 × η_v) is the pressure-power conversion coefficient (V_stroke is the displacement per stroke, in L / rev).

[0021] Therefore, the formula for estimating export pressure is: P_est = P_inlet + (P_active - P_loss(n, T_w, U_dc)) / K(n, η_v) Where P_inlet is the inlet pressure (usually atmospheric pressure or a known inlet pressure), and P_loss is obtained by looking up the speed-loss curve obtained from the factory calibration, and temperature and voltage compensation are performed.

[0022] (2) Multi-parameter compensation mechanism: To improve the accuracy of pressure estimation, the model incorporates the following compensation: Voltage compensation: When the bus voltage fluctuates, the current will change in the opposite direction under the same load. The power reference is corrected in real time by U_dc to eliminate the impact of grid fluctuations. Speed ​​compensation: The no-load loss P_loss is different at different speeds. A piecewise polynomial P_loss(n)=a0+a1·n+a2·n² is used for fitting. During operation, the table is looked up according to the actual speed. Aging compensation: Records the power baseline drift during long-term operation, periodically and adaptively updates the P_loss curve, and compensates for pump head wear and seal aging.

[0023] (3) Overpressure graded protection strategy: Four pressure thresholds are set, and a comprehensive judgment is made based on the power change rate: Level 1: Pre-Warning P_est ≥ P_warn (e.g. 80% of rated) dP / dt ≥ Pre-warning rate Overpressure pre-warning, log pressure, no intervention Level 2: Derate P_est ≥ P_derate (e.g. 90% of rated) dP / dt ≥ Derate rate Start speed compensation, smooth reduction of target speed, reduce output flow to reduce system pressure Level 3: Limit Flow P_est ≥ P_limit (e.g. 100% of rated) dP / dt ≥ Protection rate Force limit maximum speed and flow to safe values, limit PWM duty cycle, maintain minimum safe flow Level 4: Shutdown P_est ≥ P_shutdown (e.g. 110% of rated) or dP / dt spike (stall characteristic) Perform safe shutdown (first speed reduction then power off), lock protection state, manual reset required Rapid stall protection: When a sharp rise in dP / dt (exceeding 30% of the rated power per 100ms) is detected accompanied by a simultaneous decrease in rotational speed, a pump head stall or complete line blockage is determined, and a level 4 shutdown is directly triggered with a response time of <200ms to prevent damage to the motor and pump head.

[0024] Pressure hysteresis design: When each level of protection exits, the pressure must be 3%~5% lower than the entry threshold to prevent frequent switching near the threshold.

[0025] Undervoltage / idle running / leakage detection: Idle running / lack of fluid detection: When P_active continuously remains below the no-load power threshold P_idle (1.1 times the calibrated value) and the estimated pressure is close to the inlet pressure, it is determined that the pump chamber lacks fluid or the inlet flow is interrupted, an idle running alarm is triggered, and shutdown or intermittent operation mode can be selected to prevent dry abrasion of the diaphragm; Line leakage detection: When P_active and P_est drop suddenly (dP / dt is negative and exceeds the threshold) while the rotational speed remains unchanged, it is determined that the outlet line leaks or the check valve fails, and a leakage alarm is triggered; Inlet blockage detection: When the estimated pressure value is low and the flow rate decreases, combined with the rotational speed feedback, it can be determined that the inlet filter is blocked.

[0026] (5) Load dynamic adjustment strategy: Dynamically adjust the operating parameters according to the deviation between the estimated pressure P_est and the target pressure P_target: Overpressure condition: n_comp = n_set × K_n(P), K_n(P) is 1 when P_est<P_warn, and decreases smoothly with the increase of pressure in the overpressure zone, reducing the output flow by lowering the rotational speed, so as to reduce the system pressure; Undervoltage condition: If the process permits, the rotational speed can be appropriately increased to compensate for the flow loss and maintain the target flow; Power upper limit: P_max(P) = P_rated × K_p(P), the power upper limit is synchronously limited in the overpressure zone; Adjustment rate: The rotational speed change rate is limited to dn / dt ≤ 10% of the rated rotational speed per second, so as to avoid pressure shock and water hammer effect.

[0027] (6) Pressure closed-loop flow compensation: The volumetric efficiency η_v of the positive displacement pump decreases as the outlet pressure rises (internal leakage increases), and a pressure-volumetric efficiency correction coefficient is established: η_v(P) = η_v0 × (1 - γ × ΔP) where γ is the leakage coefficient (factory calibrated). The actual flow rate is corrected as: Q_actual = n_act × V_stroke × η_v(P_est) Ensure that the displayed flow rate matches the actual output flow rate under high-pressure conditions, and compensate for flow loss caused by reduced volumetric efficiency by fine-tuning the rotation speed if necessary.

[0028] 4. BLDC drive unit: The BLDC drive unit consists of a three-phase inverter bridge, a pre-drive chip, and current sampling and gate drive logic. The PWM limiting instruction duty_max output by the algorithm compensation unit is received, limiting the actual duty cycle duty ≤ duty_max; Receive the target speed n_comp after load adjustment, and execute a six-step commutation or FOC SVPWM drive; Hardware-level overcurrent protection: The drive is shut down within <10μs when the phase current exceeds the hardware threshold; The drive status (bus voltage, phase current, fault code) is fed back in real time, providing a data source for the power acquisition unit.

[0029] 5. Flow rate and speed control unit: Speed ​​feedback: n_act is obtained by Hall sensor (six steps) or encoder (FOC) with a resolution ≥1 rpm; Speed ​​closed loop: Incremental PID, with n_comp as the target, outputs PWM to the BLDC drive unit; Load torque feedforward: The load torque T_load=K×ΔP is estimated based on the calculated pressure and fed forward to the current loop to improve dynamic response; Flow measurement: Q_theory=n×V_stroke, output Q_actual after pressure-volume efficiency correction; State feedback: n_act, T_est (estimated by current), and Q_act are fed back to the algorithm compensation unit.

[0030] 6. System workflow: The workflow of the system of this invention is as follows: Step S1: The power acquisition unit synchronously acquires the bus voltage U_dc(k) and bus current I_dc(k); Step S2: The data processing unit performs filtering, power calculation (P_active, cosφ), anomaly removal, and power change rate dP / dt calculation; Step S3: The algorithm compensation unit looks up the no-load loss table P_loss(n) based on the current speed n_act, and after voltage and temperature compensation, calculates the outlet pressure P_est using the power-pressure mapping model; Step S4: Determine the pressure level, and combine dP / dt to identify operating conditions such as stall / idle / leakage, and determine the protection level; Step S5: Calculate the speed compensation coefficient K_n(P) and power limit K_p(P) according to the protection level, and generate the load adjustment command; Step S6: Calculate the pressure-volume efficiency correction coefficient η_v(P) to correct the flow rate measurement; Step S7: Send n_comp, PWM limiting, and feedforward torque to the BLDC drive unit and the flow rate and speed control unit; Step S8: Collect actual rotational speed, current, and power, feed them back to the power acquisition and algorithm compensation unit, and return to step S1 to form a closed loop.

Claims

1. A pressure protection system for a digital metering pump, comprising a digital metering pump, characterized in that... The digital metering pump is equipped with a power acquisition unit, a data processing unit, an algorithm compensation unit, a BLDC drive unit, and a flow rate and speed control unit. The power acquisition unit is responsible for sampling the bus voltage and phase current and calculating instantaneous power; the data processing unit is responsible for filtering electrical parameters, calculating active power, and extracting power features. The algorithm compensation unit is responsible for power and pressure soft measurement, graded protection and load adjustment strategy generation; the BLDC drive unit is responsible for motor three-phase power drive and PWM control; the flow rate and speed control unit is responsible for speed closed loop, flow metering and load torque feedforward compensation; the five units work together to form a complete sensorless pressure protection closed loop system.

2. The operating pressure protection system for a digital metering pump as described in claim 1, characterized in that... The power acquisition unit includes a voltage sampling circuit, a current sampling circuit, a signal conditioning and high-precision A / D converter. The bus voltage sampling circuit and the phase current sampling circuit are arranged in the BLDC motor drive circuit of the digital metering pump. The bus voltage and phase current are synchronously acquired at a fixed sampling frequency, and the instantaneous power is calculated in real time. At the same time, the sampling circuit is self-checked for open circuit, short circuit and over-range faults.

3. The operating pressure protection system for a digital metering pump as described in claim 1 or 2, characterized in that... The data processing unit performs digital filtering on the raw voltage and current data, calculates active power, apparent power and power factor, removes outliers, calculates the power change rate, and outputs stable power characteristic values ​​and change rates to the algorithm compensation unit.

4. The operating pressure protection system for a digital metering pump as described in claim 1 or 2, characterized in that... The algorithm compensation unit receives P_active(k) and dP / dt output by the data processing unit, as well as the actual rotational speed n_act, estimated torque T_est, and actual flow rate Q_act fed back by the flow rate and rotational speed control unit, and executes the following algorithm logic: (1) Power-pressure mapping model: The formula for estimating outlet pressure is P_est = f(P_active, n, T_media, U_dc), where P_active is the active power of the motor, n is the current speed, T_media is the medium temperature, and U_dc is the bus voltage. The model is based on the load characteristics of a positive displacement pump: P_active = P_loss(n) + K_pump × ΔP, where P_loss(n) is the speed-related no-load loss, K_pump is the pump's pressure-to-power conversion coefficient, and ΔP is the difference between the outlet pressure and the inlet pressure; The P_loss(n) curve and K_pump coefficient are obtained through factory calibration. ΔP is then calculated in real time during operation to obtain the outlet pressure P_est = P_inlet + ΔP. (2) Multi-parameter compensation: Voltage compensation, speed compensation, temperature compensation and viscosity compensation are performed on the power-pressure mapping to ensure the accuracy of pressure estimation; (3) Overpressure graded protection: Set multiple pressure thresholds, combine power change rate to predict stall, and execute strategies such as alarm, speed reduction and derating, flow restriction and safe shutdown at different levels; (4) Underpressure / idle / leakage detection: When the estimated pressure is lower than the no-load threshold and the power is consistently low, it is determined to be idling due to lack of liquid; when the power suddenly drops and the estimated pressure drops sharply, it is determined to be pipeline leakage. Each triggers the corresponding alarm and protection; (5) Load adjustment strategy: The target speed and power limit are dynamically adjusted according to the calculated pressure. When the pressure is over-pressured, the speed is smoothly reduced to reduce the output flow and reduce the system pressure; when the pressure is under-pressured, the speed is appropriately increased to maintain the flow, so as to achieve pressure-flow synergistic optimization. (6) Pressure closed-loop compensation: The calculated pressure is introduced into the flow metering correction. Since pressure changes will cause changes in volumetric efficiency, the actual flow calculation is corrected by the pressure compensation coefficient K_q(P) to ensure the metering accuracy under high pressure conditions.

5. The operating pressure protection system for a digital metering pump as described in claim 1 or 2, characterized in that... The BLDC drive unit receives the drive limiting command and PWM adjustment parameters output by the algorithm compensation unit, executes three-phase inverter bridge drive, PWM duty cycle adjustment and commutation logic control, integrates hardware overcurrent and overvoltage protection, and transforms the pressure protection strategy of the algorithm layer into the actual drive behavior of the motor.

6. The operating pressure protection system for a digital metering pump as described in claim 1 or 2, characterized in that... The flow rate and speed control unit receives load adjustment commands and speed optimization commands output by the algorithm compensation unit, and performs closed-loop speed control in conjunction with feedback from the grating sensor to perform flow metering and pressure compensation correction; at the same time, it feeds back the actual speed, estimated torque, actual flow rate and other operating status to the algorithm compensation unit to form a closed loop.

7. The operating pressure protection system for a digital metering pump as described in claim 1 or 2, characterized in that... The main loop workflow of the system includes the following steps: Step S1: The power acquisition unit synchronously acquires the bus voltage and bus current; Step S2: The data processing unit performs filtering, power calculation, anomaly removal, and power change rate calculation; Step S3: The algorithm compensation unit looks up the no-load loss table based on the current speed, and after voltage and temperature compensation, calculates the outlet pressure using the power-pressure mapping model; Step S4: Determine the pressure level, and combine dP / dt to identify operating conditions such as stall / idle / leakage, and determine the protection level; Step S5: Calculate the speed compensation coefficient and power limit based on the protection level, and generate a load adjustment command; Step S6: Calculate the pressure-volume efficiency correction factor and correct the flow rate measurement; Step S7: Send n_comp, PWM limiting, and feedforward torque to the BLDC drive unit and the flow rate and speed control unit; Step S8: Collect actual rotational speed, current, and power, feed them back to the power acquisition and algorithm compensation unit, and return to step S1 to form a closed loop.

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