A method for real-time compensation correction of pressure smooth control of liquid chromatography pump

Abstract

This invention discloses a real-time compensation and correction method for stable pressure control of a liquid chromatography pump. It ensures that the liquid chromatograph, which is based on low pulsation of the liquid pump under high pressure, can maintain stable constant flow rate accuracy and pulsation index under different operating conditions and media conditions. It overcomes the problems of large pressure pulsation rate and offline non-compensation of operating parameters of existing liquid pumps, and has high accuracy and stable operating conditions.

Description

Technical Field

[0001] This application relates to the technical field of electronic engineering, and in particular to a method for real-time compensation and correction of pressure stabilization control of a liquid chromatography pump. Background Technology

[0002] Currently, ultra-high performance liquid chromatography (UHPLC), with its higher resolution, faster analysis speed, and higher sensitivity, represents the development trend of liquid chromatography systems. However, there is a significant gap between domestic and international UHPLC technology, particularly in the core component—the liquid chromatography pump. This gap manifests in unresolved issues such as the precision of multi-axis coordinated control, online compensation for compressible fluid flow rate, and the stability of pulsations under ultra-high pressure. These challenges hinder the achievement of required flow accuracy, precision, and pressure pulsation control, thus restricting the further development of UHPLC. Summary of the Invention

[0003] This application addresses the problems of large pressure pulsation rate and offline non-compensation of operating parameters in existing liquid chromatography pumps using cam-driven methods, and proposes a real-time compensation and correction method for stable pressure control of liquid chromatography pumps.

[0004] Firstly, a method for real-time compensation and correction of pressure stabilization control in a liquid chromatography pump is provided. This method is applied to a dual-cylinder tandem pump flow path system, which includes a main cylinder and an auxiliary cylinder. The main cylinder inlet is a one-way valve, and the main cylinder outlet is connected to a one-way solenoid valve at the auxiliary cylinder inlet. Both the main cylinder and auxiliary cylinder outlets have pressure sensors. The main cylinder pressure sensor is sequentially connected to the one-way solenoid inlet valve of the auxiliary cylinder, and the auxiliary cylinder outlet pressure sensor is connected to the pump outlet. The dual-cylinder tandem pump flow path may further include an M1 motor and an M2 motor. The M1 motor drives the plunger rod in the main cylinder to move, and the M2 motor drives the plunger rod in the auxiliary cylinder to move. The method includes:

[0005] During the main and auxiliary cylinder reversal process T0, the pump controller collects the current pressure difference between the main and auxiliary cylinders ΔP(t)=Pzhu(t)-Pfu(t) according to the acquisition cycle;

[0006] When ΔP(t) < 0, the solenoid check valve is closed.

[0007] When ΔP(t) > 0, the value collected in the previous collection cycle ΔP(t-1) is compared with ΔP(t). When ΔP(t) > ΔP(t-1), the electromagnetic check valve is closed; when ΔP(t) < ΔP(t-1), the electromagnetic check valve is opened.

[0008] In conjunction with the first aspect, in some implementations of the first aspect, the method further includes:

[0009] Before the master cylinder and auxiliary cylinder reversal section, the master cylinder pressure sensor is calibrated.

[0010] In conjunction with the first aspect, in some implementations of the first aspect, the calibration of the master cylinder pressure sensor includes:

[0011] The pressure sensors of the master cylinder and the auxiliary cylinder record the pressure difference ΔPn(t) collected every 10 milliseconds during the alternating reciprocating process of the master and auxiliary cylinders and calculate the average value ΔP12(t), which is used as the reference calibration value of the master cylinder pressure sensor in cycle t+1. Pzhu(t+1)=Pzhu(t)+ΔP12(t).

[0012] In conjunction with the first aspect, in some implementations of the first aspect, when the main cylinder and auxiliary cylinder switch directions, the main cylinder discharge speed is set to N times the auxiliary cylinder suction speed.

[0013] In conjunction with the first aspect, in some implementations of the first aspect, the cross-sectional area of ​​the main cylinder cavity is the same as that of the auxiliary cylinder cavity, the length of the main cylinder cavity is N times the length of the auxiliary cylinder cavity, and the liquid propulsion speed V1(t) of the main cylinder per unit time is proportional to the liquid suction speed V2(t) of the auxiliary cylinder and the flow rate, V1(t)∶V2(t)=N∶1.

[0014] In conjunction with the first aspect, in some implementations of the first aspect, the method further includes:

[0015] During the compression process of the main cylinder, Tzhu, the pressure difference between the main cylinder and the auxiliary cylinder is collected at all times: ΔP(t) = Pzhu(t) - Pfu(t).

[0016] When ΔP(t) < 0, the controller realizes the main cylinder compression stroke L1. i The cycle continues to advance, and the calculation formula is as follows:

[0017]

[0018] β=f(P2)

[0019] β is the solvent compressibility coefficient, which is a parameter that has a corresponding functional relationship with the auxiliary cylinder pressure value P2. ΔP(t) is the pressure difference between the main and auxiliary cylinders, and P2(t) is the current pressure value of the auxiliary cylinder.

[0020] When ΔP(t)>0, L i ≤0.

[0021] In conjunction with the first aspect, in some implementations of the first aspect, the method further includes: during the auxiliary cylinder propulsion process Tfu, the controller continuously adjusts the auxiliary cylinder propulsion stroke based on the current auxiliary cylinder pressure value P2(t).

[0022]

[0023] In conjunction with the first aspect, in some implementations of the first aspect, the auxiliary cylinder pressure value P2(t) is calibrated periodically. In the initial stage of normal operation of the main and auxiliary cylinders, the average value of the data detected by the auxiliary cylinder pressure sensor is calculated, and the average value is used to calibrate the auxiliary cylinder pressure value P2(t).

[0024] In a second aspect, a pump controller is provided for performing the method as described in any of the implementations of the first aspect above.

[0025] Thirdly, a dual-cylinder series pump flow path system is provided, comprising a main cylinder and an auxiliary cylinder. The main cylinder inlet is a one-way valve, and the main cylinder outlet is connected to the auxiliary cylinder inlet with a one-way solenoid valve. Both the main cylinder and the auxiliary cylinder outlets have pressure sensors. The main cylinder pressure sensor is sequentially connected to the auxiliary cylinder solenoid inlet one-way valve, and the auxiliary cylinder outlet pressure sensor is connected to the pump outlet. The dual-cylinder series pump flow path may further include an M1 motor and an M2 motor. The M1 motor is used to drive the piston rod in the main cylinder to move, and the M2 motor is used to drive the piston rod in the auxiliary cylinder to move. The dual-cylinder series pump flow path system also includes a pump controller for executing the method described in any of the implementations of the first aspect above.

[0026] Compared with the prior art, the solution provided in this application has at least the following beneficial technical effects:

[0027] This invention provides a real-time compensation and correction method for stabilizing the pressure of a liquid chromatography pump. It utilizes a dual-cylinder series flow path to achieve alternating continuous discharge from the main and auxiliary cylinders. Independent pressure sensors for both cylinders are used to compare and correct the pressure data in real time, ensuring consistent calibration. An electromagnetic check valve controls the switching discharge process between the main and auxiliary cylinders, reducing pressure pulsation in the flow path. The main controller estimates and compensates based on the fluid compressibility coefficient of the liquid pump, rapidly stabilizing the main cylinder pressure to approach the auxiliary cylinder pressure, further reducing the pulsation rate during the cylinder switching discharge process. This method is applicable under any operating pressure condition and offers better pressure pulsation control accuracy. Attached Figure Description

[0028] Figure 1 This is a block diagram of the series pump assembly described in the invention.

[0029] Figure 2 The flowchart of the pressure stabilization algorithm described in the invention. Detailed Implementation

[0030] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0031] This application provides a real-time compensation and correction method for stabilizing the pressure of a liquid chromatography pump. In a dual-cylinder series flow path mode, independent pressure sensors for the main and auxiliary cylinders compare and correct the pressure data of the two cylinders in real time, ensuring the consistency of the pressure data calibration between the main and auxiliary cylinders. An electromagnetic check valve controls the liquid discharge process during the switching between the main and auxiliary cylinders, reducing pressure pulsation in the flow path. The main controller estimates and compensates based on the fluid compressibility coefficient of the liquid pump, enabling the pressure in the main cylinder to quickly and stably approach the pressure value of the auxiliary cylinder, further reducing the pulsation rate during the liquid discharge process during the switching between the main and auxiliary cylinders.

[0032] The method for stabilizing the pressure of a liquid chromatography pump can be applied to, for example... Figure 1 The diagram shows a dual-cylinder tandem pump flow path system. This system can include a main cylinder and an auxiliary cylinder. The main cylinder inlet is a check valve, and the main cylinder outlet is connected to a check solenoid valve at the auxiliary cylinder inlet. Both the main and auxiliary cylinder outlets have pressure sensors. The main cylinder pressure sensor is sequentially connected to the check valve at the auxiliary cylinder inlet, and the auxiliary cylinder outlet pressure sensor is connected to the pump outlet. The dual-cylinder tandem pump flow path can also include motors M1 and M2. Motor M1 drives the piston rod in the main cylinder, and motor M2 drives the piston rod in the auxiliary cylinder.

[0033] The main cylinder, acting as a continuous liquid storage unit, pressurizes external liquid and delivers it to the auxiliary cylinder cavity. The pump controller drives the main cylinder motor to push the plunger rod in a reciprocating motion. When it advances, it discharges the liquid in the cavity into the auxiliary cylinder; when it retracts, it draws external liquid into the cavity. This process repeats continuously, with a period of time T, thus ensuring that external liquid reaches the auxiliary cylinder cavity.

[0034] The auxiliary cylinder, acting as a continuous infusion unit, delivers the high-pressure liquid from the main cylinder to the pump outlet continuously and evenly. The pump controller drives the auxiliary cylinder motor to push the plunger rod in a reciprocating motion. During the forward motion, the liquid in the chamber is discharged to the pump outlet. During the reverse motion, the forward speed of the main cylinder and the opening and closing time of the solenoid valve are controlled to ensure that the liquid's forward speed is greater than the reverse speed of the auxiliary cylinder, thus guaranteeing that the liquid is discharged to the pump outlet. This process is repeated cyclically, with a period of time T, thus achieving the flow of liquid from the main cylinder to the pump outlet.

[0035] The actions of the main and auxiliary cylinders can be referenced from the dual-plunger coordinated operation curve. The liquid pump achieves liquid delivery through the coordinated action of the main and auxiliary cylinders in series, constructing mathematical curves for velocity advection and gradient operation. This curve architecture design is mathematically precise, servo control is easy to implement, the program has applicability to positive and negative gradients, and velocity and acceleration constraints are established, along with multivariate correlation constraint equations. One cycle of the main and auxiliary cylinders (one cycle of the main cylinder includes liquid suction + compression, and one cycle of the auxiliary cylinder includes liquid suction + discharge) can only achieve a short period of flow output; therefore, multiple cycles need to be superimposed to achieve continuous advection.

[0036] Pressure sensors are located at the outlets of the main cylinder and the auxiliary cylinder, respectively. They collect the pressure value of each cylinder chamber in real time during each operating cycle T and feed it back to the pump controller to realize sensor differential pressure correction, main cylinder pressure establishment, main cylinder and auxiliary cylinder reversal and drainage, and auxiliary cylinder pressure stabilization.

[0037] The opening and closing of the one-way solenoid valve controls the timing of liquid exchange between the main cylinder and the auxiliary cylinder. During the rapid switching and liquid discharge process between the main cylinder and the auxiliary cylinder, there is a certain operating phase difference between the two cylinders. The one-way solenoid valve controls the timing of liquid flowing from the main cylinder into the auxiliary cylinder by opening and closing, so as to achieve a stable output value of liquid from the auxiliary cylinder at the pump outlet under pressure conditions and reduce pump outlet pressure pulsation.

[0038] The flow path of a dual-cylinder tandem pump may also include a pump controller. The pump controller operates throughout the entire operation of the main and auxiliary cylinders, performing real-time transient compensation calculations and estimating the compressibility coefficient of the medium in the main and auxiliary cylinders and adjusting the stroke of the main and auxiliary cylinders based on the current state parameters of the pump.

[0039] During the main and auxiliary cylinder circulation, to ensure the sum of velocity vectors is not zero, the main cylinder phase always leads the auxiliary cylinder phase. The phase lead is dynamically adjusted based on the velocity vectors. A multivariate quadratic equation is solved under the combined constraints of phase and time. When the main and auxiliary cylinders switch directions, the main cylinder discharge speed is set to N times the auxiliary cylinder suction speed, ensuring that the combined flow rate matches the individual operating speed of the auxiliary cylinder. Illusory roots are eliminated using numerical criteria, and multiple roots are eliminated after multiple iterations of regression constraints, resulting in the velocity-time variation curves of the main and auxiliary cylinders within one cycle T, as shown below. Figure 2 As shown.

[0040] In one embodiment, to achieve a main cylinder discharge speed that is N times the auxiliary cylinder suction speed, the cross-sectional area of ​​the main cylinder cavity can be the same as that of the auxiliary cylinder cavity, and the length of the main cylinder cavity is N times the length of the auxiliary cylinder cavity. The main cylinder and auxiliary cylinder simultaneously complete an alternating reciprocating process to achieve liquid reversal. Therefore, the liquid propulsion speed V1(t) of the main cylinder per unit time is directly proportional to the liquid suction speed V2(t) of the auxiliary cylinder, where V1(t):V2(t) = N:1.

[0041] During the master-slave reversal segment T0, in the t-th cycle of master-slave operation, the pressure sensors of the master and slave cylinders respectively record the pressure difference ΔPn(t) collected every 10 milliseconds during the alternating operation of the master and slave cylinders and calculate the average value ΔP12(t), which serves as the reference calibration value for the master cylinder pressure sensor in cycle t+1: Pzhu(t+1) = Pzhu(t) + ΔP12(t). In one embodiment, the slave cylinder sensor P2 may not require calibration. The above method enables the calibration of the master cylinder sensor P1 with the slave cylinder as the reference. Since sensor detection is prone to numerical drift, the above method can reduce the relative error between the master cylinder sensor P1 and the slave cylinder sensor P2.

[0042] In one embodiment, the average value ΔP12(t) can be calculated as follows: During the t-th cycle of the main and auxiliary cylinders, the pressure sensors of the main and auxiliary cylinders record the pressure difference ΔP1(t) between the pressure sensors at the beginning of the alternating cycle and ΔP2(t) at the end of the alternating cycle. The average value ΔP12(t) of ΔP1(t) and ΔP2(t) is then calculated.

[0043] During the main and auxiliary cylinder reversal process T0, the opening and closing time of the solenoid valve is determined by the pressure difference ΔP(t) between the main and auxiliary cylinders. The pump controller collects the current pressure difference ΔP(t) = Pzhu(t) - Pfu(t) at 10-millisecond intervals. When ΔP(t) < 0, the pressure value of the main cylinder is less than that of the auxiliary cylinder, and the solenoid check valve is closed. When ΔP(t) > 0, the value collected in the previous 10-millisecond cycle ΔP(t-1) is compared with ΔP(t). When ΔP(t) > ΔP(t-1), the solenoid check valve is closed to ensure that the pressure value of ΔP(t) does not continue to increase. When ΔP(t) < ΔP(t-1), the solenoid check valve opens, and the liquid from the main cylinder enters the auxiliary cylinder to form a connection. The pressures of the main and auxiliary cylinders are balanced, and the pressure value of ΔP(t) quickly returns to 0. The pressures of the main and auxiliary cylinders are the same, and the pressure of the auxiliary cylinder is stabilized by controlling the flow rate of liquid from the main cylinder to the auxiliary cylinder.

[0044] During the compression process Tzhu in the main cylinder, the pressure difference ΔP(t) between the main cylinder and the auxiliary cylinder is constantly collected, which is calculated as Pzhu(t) - Pfu(t). Based on the pressure status of the auxiliary cylinder and the type of medium, the pre-compression amount of the main cylinder is estimated online through the relationship between the medium compressibility coefficient and pressure change.

[0045] When ΔP(t) < 0, the controller realizes the main cylinder compression stroke L1. i The cycle continues to advance, and the calculation formula is as follows:

[0046]

[0047] β=f(P2)

[0048] β is the solvent compressibility coefficient, a parameter that has a corresponding functional relationship with the auxiliary cylinder pressure value P2. ΔP(t) is the pressure difference between the main and auxiliary cylinders, and P2(t) is the current pressure value of the auxiliary cylinder.

[0049] When ΔP(t) > 0,

[0050] L i ≤0

[0051] In other words, the plunger in the master cylinder can retract. The hydraulic pressure in the master cylinder is established within a time frame of Tzhu ≤ 0.3T.

[0052] During the auxiliary cylinder propulsion process Tfu, the controller constantly adjusts the auxiliary cylinder propulsion stroke based on the current auxiliary cylinder pressure value P2(t).

[0053]

[0054] In some embodiments, the auxiliary cylinder pressure value P2(t) can be calibrated periodically. The average value of the data detected by the auxiliary cylinder pressure sensor is calculated during the initial stage of normal operation of the main and auxiliary cylinders, and this average value is used to calibrate the auxiliary cylinder pressure value P2(t). The value output by the auxiliary cylinder pressure sensor can represent the stability of the external fluid supply, thereby reducing the absolute error caused by numerical drift of the auxiliary cylinder pressure sensor.

[0055] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims of the present invention.

Claims

1. A method for real-time compensation corrected pressure smoothing control of a liquid chromatography pump, characterized in that, The method is applied to a dual-cylinder tandem pump flow path system, which includes a main cylinder and an auxiliary cylinder. The main cylinder inlet is a one-way valve, and the main cylinder outlet is connected to the auxiliary cylinder inlet with a one-way solenoid valve. Both the main cylinder and auxiliary cylinder outlets have pressure sensors. The main cylinder pressure sensor is sequentially connected to the auxiliary cylinder solenoid inlet one-way valve, and the auxiliary cylinder outlet pressure sensor is connected to the pump outlet. The dual-cylinder tandem pump flow path system also includes an M1 motor and an M2 motor. The M1 motor is used to drive the piston rod in the main cylinder to move, and the M2 motor is used to drive the piston rod in the auxiliary cylinder to move. The method includes: During the main and auxiliary cylinder reversal process The pump controller collects the current pressure difference between the master cylinder and the auxiliary cylinder according to the collection cycle. ; when When this happens, the solenoid check valve closes. when At that time, the previous collection cycle will be... The collected values ​​and To make a comparison, when When the solenoid check valve closes, When this happens, the solenoid check valve opens; During the compression process of the master cylinder The pressure difference between the master cylinder and the auxiliary cylinder is collected at all times. ; when At that time, the controller realizes the compression stroke L1 of the master cylinder. 𝒾 The cycle continues to advance, and the calculation formula is as follows: β is the solvent compressibility coefficient, a parameter that has a corresponding functional relationship with the auxiliary cylinder pressure value P2. The pressure difference between the main and auxiliary cylinders. This is the current pressure value of the auxiliary cylinder; when At that time, L1 𝒾 ≤0; During the auxiliary cylinder propulsion process The controller constantly adjusts the pressure value of the auxiliary cylinder. Adjust the stroke of the auxiliary cylinder. 。 2. The method according to claim 1, characterized in that, The method further includes: Before the master cylinder and auxiliary cylinder reversal section, the master cylinder pressure sensor is calibrated.

3. The method according to claim 2, characterized in that, The calibration of the master cylinder pressure sensor includes: The pressure sensors of the master cylinder and auxiliary cylinder respectively record the pressure difference collected every 10 milliseconds during the alternating reciprocating process of the master and auxiliary cylinders. And calculate the average value. As Reference calibration value of the master cylinder pressure sensor. .

4. The method according to claim 1, characterized in that, When the main cylinder and auxiliary cylinder switch directions, the main cylinder discharge speed is set to N times the auxiliary cylinder suction speed.

5. The method according to claim 4, characterized in that, The cross-sectional area of ​​the main cylinder cavity is the same as that of the auxiliary cylinder cavity, and the length of the main cylinder cavity is N times the length of the auxiliary cylinder cavity. The fluid propulsion speed of the main cylinder per unit time is... With the suction speed of the auxiliary cylinder liquid Traffic is directly proportional. .

6. The method according to claim 1, characterized in that, Periodically check the auxiliary cylinder pressure value Calibration is performed by averaging the data detected by the auxiliary cylinder pressure sensor during the initial stage of normal operation of the main and auxiliary cylinders, and then using this average value to determine the auxiliary cylinder pressure value. Perform calibration.

7. A pump controller, characterized in that, The pump controller is used to perform the method as described in any one of claims 1 to 6.

8. A dual-cylinder series pump flow path system, characterized in that, The dual-cylinder series pump flow path system includes a main cylinder and an auxiliary cylinder. The main cylinder inlet is a one-way valve, and the main cylinder outlet is connected to the auxiliary cylinder inlet with a one-way solenoid valve. Both the main cylinder and the auxiliary cylinder outlets have pressure sensors. The main cylinder pressure sensor is sequentially connected to the auxiliary cylinder solenoid inlet one-way valve, and the auxiliary cylinder outlet pressure sensor is connected to the pump outlet. The dual-cylinder series pump flow path system may also include an M1 motor and an M2 motor. The M1 motor is used to drive the piston rod in the main cylinder to move, and the M2 motor is used to drive the piston rod in the auxiliary cylinder to move. The dual-cylinder series pump flow path system also includes a pump controller for executing the method as described in any one of claims 1 to 6.

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