CN116255329A

CN116255329A - Dynamic deviation correction method for liquid chromatography infusion pump

Info

Publication number: CN116255329A
Application number: CN202310144457.9A
Authority: CN
Inventors: 于忠瀚
Original assignee: Kunpeng Instrument Dalian Co ltd
Current assignee: China Spectrum Tech Beijing Technology Co ltd
Priority date: 2023-02-21
Filing date: 2023-02-21
Publication date: 2023-06-13

Abstract

The invention provides a dynamic deviation correction method of a liquid chromatograph infusion pump, which comprises a position detection mechanism for detecting the fixed position of a cam; firstly, measuring the differential pulse number from the fixed position of a cam to the starting point position according to the cam action characteristics; calculating the theoretical pulse number of the cam rotation in each correction period according to the step angle and the transmission ratio of the stepping motor; calculating the pulse deviation direction and the deviation amount of the current period through the accumulated pulse number of each period reaching a fixed position; judging whether the single deviation amount is triggered to exceed the limit or the accumulated deviation amount is triggered to exceed the limit, and if not, correcting the pulse count value; the pulse count value correction includes: the recorded count value at the time of reaching the fixed position is corrected to the theoretical pulse number of the correction period. The dynamic deviation correction in the invention does not concern the change of other conditions or environmental factors, and fundamentally corrects the direction and the deviation amount of the deviation from the real deviation degree calculated in real time.

Description

Dynamic deviation correction method for liquid chromatography infusion pump

Technical Field

The invention relates to the technical field of liquid chromatograph, in particular to a dynamic deviation correction method of a liquid chromatograph infusion pump.

Background

The high performance liquid chromatograph is an instrument which utilizes the chromatographic separation principle, pushes a mobile phase into a system by a high pressure infusion pump, injects a sample solution into the mobile phase by a sample injector, forms separation on a chromatographic column and performs analysis on each component by a detector. The high-pressure infusion pump is a device for driving a mobile phase, and a cam is generally used for controlling the liquid suction and the liquid discharge of the high-pressure infusion pump, and in the control process, a plurality of links have requirements on the phase accuracy of cam action. For example, the motion engagement between two plunger pumps depends on the accuracy of the cam's phase design and control. The control of low pressure gradient, which is to control the opening time of each proportional valve according to the set proportion, has high requirement on the phase accuracy of cam action, and if the phase matching is not good, the accuracy of the proportional control may be reduced, gas may be mixed in, and the device may be damaged. In addition, in order to control the pressure pulsation in the entire operation cycle, the speed change control is performed in accordance with the cam phase, and a high requirement is also placed on the accuracy of the cam phase. When pressure difference exists between the two plunger pumps, the opening of the one-way valve is delayed, and the control moment of the opening delay of the check valve also needs to be matched with a cam, if the phase matching is poor, the fluctuation of flow speed and pressure can be caused, and the result stability of a chromatographic system is affected.

Currently, the controller of an infusion pump often determines the rotational start point and phase by means of a photosensor, encoder, pulse count, etc. However, in practical applications, when the infusion pump is continuously operated, accumulated deviations caused by different system pressure environments, load conditions and long-term operation are caused, and as a result of the phase deviations, the cam phase recognized by the controller is deviated from the actual phase of the cam mechanism, and the controller controls the cam mechanism according to the recognized phase, which results in inconsistent control results of the mechanism and the expectations. The phase deviation is caused by the following factors:

(1) The motor drives the cam shaft to rotate through the belt, and the belt has certain stretchability. When the system pressure increases, or the load increases, the belt is stretched and the motor forms a phase offset with the camshaft.

(2) During long-term operation of the stepper motor, there may be occasional loss of synchronization of individual pulses, which, when accumulated, result in phase misalignment of the motor and the camshaft.

Disclosure of Invention

In view of the above, the present invention provides a method for correcting dynamic deviation of a liquid chromatograph infusion pump, which can automatically correct dynamic phase deviation of a cam shaft of the liquid chromatograph infusion pump in each action cycle, and improve phase accuracy of cam action.

For this purpose, the invention provides the following technical scheme:

the invention provides a dynamic deviation correction method of a liquid chromatograph infusion pump, which comprises a position detection mechanism for detecting the fixed position of a cam; the fixed position at least comprises an origin position; the method comprises the following steps:

calculating the theoretical pulse number of the cam rotation in each correction period according to the step angle and the transmission ratio of the stepping motor;

calculating the pulse deviation direction and the deviation amount of the current period according to the accumulated pulse number of each period reaching the original point position; each cycle comprising 1 or more correction cycles;

judging whether the single-period deviation amount is triggered to exceed the limit or the accumulated deviation amount is triggered to exceed the limit, if so, judging that the error is caused, and stopping the operation; if not, carrying out pulse count value correction;

wherein the single period deviation amount exceeds the limit: delta > Th1 or delta < (-1) Th1; the cumulative deviation amount exceeds the limit: ΣΔ > Th or ΣΔ < (-1) Th; delta represents the deviation amount, th1=p0.5%, representing the single period deviation amount threshold; ΣΔ represents the cumulative deviation, th=p×1%, representing the cumulative deviation amount threshold;

the pulse count value correction includes: and correcting the recorded count value when the fixed position is reached to the theoretical pulse number of the correction period.

Further, the liquid chromatograph infusion pump is a tandem type double-plunger pump.

Further, the position detection mechanism includes: the light shielding sheet, the fixing part, the first photoelectric sensor and the second photoelectric sensor; the anti-dazzling screen is arranged on a cam shaft of the infusion pump of the liquid chromatograph and can synchronously rotate along with the cam; the first photoelectric sensor and the second photoelectric sensor are arranged at the fixing part in an up-down arrangement mode, are fixed in position and do not rotate; the radius of the shading sheet has 3 specifications of long, medium and short, and the long specification can shade the first photoelectric sensor and the second photoelectric sensor; the first photoelectric sensor is not shielded, and the second photoelectric sensor is shielded by the medium specification; the short specification enables neither the first photosensor nor the second photosensor to be shielded.

Further, the fixed position includes an origin position; the position detection mechanism detecting the origin position includes:

the shading sheet fixed on the cam shaft synchronously rotates clockwise along with the cam shaft;

the state that the front edge of the outer ring of the shading sheet is just shaded from the non-shading state relative to the first photoelectric sensor is the original position of the rotation of the cam shaft.

Further, the fixed positions include 4 reference positions; the position detection mechanism detecting a reference position includes:

the front edge of the outer ring of the shading sheet is switched from an unshielded state to a just shielded state relative to the first photoelectric sensor, and is in a shielded state relative to the second photoelectric sensor, and corresponds to a first reference position of the rotation of the cam shaft;

the front edge of the outer ring of the shading sheet is switched from a shading state to a state just not shading relative to the first photoelectric sensor, and the front edge of the outer ring of the shading sheet is in a shading state relative to the second photoelectric sensor and corresponds to a second reference position of the rotation of the cam shaft;

the front edge of the outer ring of the shading sheet is in a non-shading state relative to the first photoelectric sensor, and is switched from a shading state to a just non-shading state relative to the second photoelectric sensor, and corresponds to a third reference position of the rotation of the cam shaft;

the front edge of the outer ring of the shading sheet is in an unshielded state relative to the first photoelectric sensor, and is switched from the unshielded state to a just shielded state relative to the second photoelectric sensor, and corresponds to a fourth reference position of the rotation of the cam shaft.

Further, calculating the pulse deviation direction and the deviation amount of the current period includes:

measuring the differential pulse number from the fixed position to the starting position of the cam according to the cam action characteristics;

when the pump is just started, the pump is in a state of uncertain position, and rotates clockwise until the position detection mechanism detects the original point position or the first reference position;

then, after the differential pulse acts for a plurality of pulses, defining the differential pulse as a starting point position, and resetting the current pulse count;

in the continuous rotation, the pulse count is accumulated, and when the initial point position or the first reference position is reached again, the theoretical accumulated pulse is obtained by subtracting the differential pulse number from the theoretical pulse number of each period, and the single deviation is obtained by subtracting the theoretical accumulated pulse from the actual accumulated pulse; the positive and negative of the single deviation amount indicate the deviation direction.

Further, the correction period is each turn with the origin position as a reference.

Further, the correction period is every 1/4 turn based on the 4 reference positions.

The invention has the advantages and positive effects that: in continuous operation of an infusion pump, the pressure is dynamically changed and difficult to predict due to different chromatographic column environments, different solutions, different flow rates and other factors. The dynamic deviation correction of the method can be carried out without concern about the change of other conditions or environmental factors, and the direction and the deviation amount of the deviation are corrected fundamentally from the real deviation degree calculated in real time. The deviation amount can be calculated by a single circle or even 1/4 circle, and the deviation is corrected in the next correction period (1 circle or 1/4 circle), so that the influence caused by the deviation can be reduced to the greatest extent.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to the drawings without inventive effort to a person skilled in the art.

FIG. 1 is a schematic diagram of a tandem double plunger pump in accordance with an embodiment of the present invention;

FIG. 2 is a schematic view of a position sensing mechanism mounted on a camshaft in an embodiment of the present invention;

FIG. 3 is a diagram of a cam rotation cycle position in an embodiment of the present invention;

FIG. 4 is a flow chart of dynamic bias correction in an embodiment of the invention;

fig. 5 is a schematic diagram showing states of the first photoelectric sensor Sen1 and the second photoelectric sensor Sen2 according to an embodiment of the present invention;

fig. 6 is a schematic diagram of 4 reference positions for deviation detection in an embodiment of the present invention.

Detailed Description

In order that those skilled in the art will better understand the present invention, a technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in which it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.

It should be noted that the terms "first," "second," and the like in the description and the claims of the present invention and the above figures are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that the embodiments of the invention described herein may be implemented in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

The high-pressure infusion pump of the high-performance liquid chromatograph adopts a serial double-plunger pump. As shown in fig. 1, the tandem double plunger pump includes: the driving motor 1, the driving belt 2, the cam shaft 3, the first cam 4, the second cam 5, the first plunger rod 6, the second plunger rod 7, the first plunger pump 8, the second plunger pump 9, the first check valve 10, the second check valve 11, the pressure sensor 12, the liquid suction port 13, and the liquid discharge port 14. Wherein, driving motor 1 rotates, drives camshaft 3 through driving belt 2 and rotates, and two cams (first cam 4 and second cam 5) on the camshaft 3 synchronous rotation drive the reciprocating motion of the first plunger rod 6 of first plunger pump 8 and the second plunger rod 7 of second plunger pump 9 respectively, and the plunger rod is taken out in the plunger pump, is pushed in, forms imbibition and pushes away the liquid effect. First check valves 10 are provided on the liquid suction side of the first plunger pump 8 and the liquid suction side of the second plunger pump 9, respectively, and the first check valves 10 allow only the flow of liquid from the liquid suction port 13 into the direction of the first plunger pump 8. A second non-return valve 11 is arranged between the first plunger pump 8 and the second plunger pump 9, the second non-return valve 11 only allowing a flow in the direction from the first plunger pump 8 into the second plunger pump 9. The liquid outlet 14 of the second plunger pump 9 is connected with a pressure sensor 12 which can monitor the pressure in the back end pipeline.

In the tandem double-plunger pump in the embodiment of the invention, a position detection mechanism for detecting the original position is additionally arranged on the cam shaft. As shown in fig. 2, the position detection mechanism includes: the light shielding sheet 100, the fixing portion 200, the first photosensor (Sen 1) 300, and the second photosensor (Sen 2) 400. Wherein, the light shielding sheet 100 is installed on the cam shaft 3 and can synchronously rotate along with the cam. The fixing part 200 is provided with Sen1, sen2 and 2 photosensors, which are arranged up and down, fixed in position, and not rotated. The radius of the shading sheet has 3 specifications of long, medium and short, and the 'long' position is shaded by Sen1 and Sen 2; in the "middle" position, sen1 is not masked and Sen2 is masked; in the "short" position, neither Sen1 nor Sen2 is masked.

In the working process of the tandem double plunger pump, the driving motor rotates, and the driving belt drives the cam shaft to rotate clockwise. The shading sheet fixed on the cam shaft synchronously rotates clockwise along with the cam shaft. The state where the outer ring leading edge of the light shielding sheet is just shielded from the non-shielded state with respect to Sen1 (as shown in the right diagram of fig. 2) is defined as the origin of rotation of the camshaft (corresponding to the 0 ° phase position).

As shown in fig. 3, which shows the relative position of the camshaft rotation cycle. Counting pulses starting from 1 starting from a starting position; after rotating for 1 week, reaching the starting point position again, and counting the pulse to be P; the number of pulses that the origin position of the photosensor differs from the origin position is x. The origin position is designed to be a position slightly advanced from the cam stroke start position phase. Because of the deviation of each pump during assembly, the pulse number x of the phase difference between the original position and the starting position of the photoelectric sensor is measured through a phase measuring device after assembly and is stored in a control substrate as a control parameter.

Based on the tandem double plunger pump with the position detection mechanism, the invention provides a method for correcting dynamic deviation.

In one embodiment, as shown in fig. 4, in the method for correcting dynamic deviation, deviation detection and correction are performed every turn with reference to the origin position, i.e., the correction period is 1 cam period. The method specifically comprises the following steps:

s101, acquiring a single deviation value.

Based on the step angle and the gear ratio of the stepper motor, the number of pulses of the theoretical cam rotation period can be calculated. The origin position is used as a fixed mechanism for positioning and can be used as a reference datum. The pulse deviation direction and the deviation amount of the current period can be calculated by the accumulated number of pulses reaching the origin position per period.

In a specific implementation, S101 is performed according to the following steps:

s111, according to the cam action characteristics, measuring the differential pulse number x from the origin position to the starting position of the cam, and storing the differential pulse number x in a substrate memory.

S112, calculating the pulse number P of one cam cycle according to the step angle and the belt transmission ratio.

And S113, when the pump is started, the pump is in a state of uncertain position, and the needle rotates until the sensor detects the original position.

S114, after the x pulses are operated again, defining the starting point position, and resetting the current pulse count C.

In S115, during the continuous rotation, the pulse counts C are accumulated, and when the pulse reaches the origin again, the accumulated pulse should be P-x theoretically, and a single deviation Δ0=c- (P-x) is defined.

For example: the theoretical pulse number per cycle is 1000, and the pulse count between actually measured two passes through the origin position sensor is 1002. A deviation of +2 pulses is generated.

The direction of occurrence of the deviation can be determined by the positive and negative of the deviation, and the magnitude of the deviation can be determined to the extent of occurrence of the deviation. This information can be used as a basis for error determination and dynamic correction of deviations.

S102, deviation amount judgment.

The great step-out of the mechanism may be directed to failure of the electrical control part or pipeline blockage, and the error needs to be timely fed back to the user and maintained so as not to influence the normal analysis work of the user. The error detection is judged by the deviation value, so that the abnormality of the rotating mechanism can be indicated timely and effectively.

In a specific implementation, S102 is performed according to the following steps:

s121, calculating a single deviation amount every time the origin position is reached.

S122, accumulating the single deviation amount per cycle, and recording as accumulated deviation amount Sigma delta.

S123, judging whether the single deviation amount exceeds the limit or the accumulated deviation amount exceeds the limit, if yes, judging that the deviation amount is wrong, and stopping the operation; if not, the pulse count value is corrected.

Wherein the single deviation amount exceeds the limit: Δ0> th1 or Δ0< (-1) Th1; the cumulative deviation amount exceeds the limit: ΣΔ > Th or ΣΔ < (-1) Th; th1=p0.5% representing a single deviation amount threshold; th=p×1%, and denotes an accumulated deviation amount threshold.

If the single deviation amount is too large, or the accumulated deviation amount is too large, there is a possibility that the stepping motor is out of step, in which the motor torque is insufficient. And judging that the operation is wrong, and stopping the operation.

If the stepping motor is not enough in torque and even is blocked, single-turn positive deviation or overtime of detection of the origin position sensor can occur.

S103, deviation correction (pulse count value correction): and when the count value reaches the original point position is C, correcting the count value to be P-x, continuing counting, and resetting to zero to start the next period until the count value reaches P.

For example: p=12000, x=100, and c=11903, and changing C to 12000-100=11900, continuing the operation and accumulating the count. When C reaches 12000, C is zeroed, and the next circle of accumulation is restarted.

In a single cycle, a single deviation value occurs due to the tension of the belt as the pressure increases. The correction of the motion pulse is performed based on the theoretical deviation value, and the phase of the deviation can be corrected. Ensuring the motion phase to be consistent with the design. When the pressure drops, the belt contracts, a single deviation value in the opposite direction is generated, and the deviation phase is corrected dynamically according to the same theory. Thus, each cam cycle can ensure the accuracy of the phase.

For example: the theoretical number of pulses per cycle is 1000. As the pressure increases, the belt stretches, resulting in a delay in cam rotational phase, a delay in timing of sensor detection, and an increase in pulse count between two passes of the home position sensor, e.g., 1002. A deviation of +2 pulses is generated. The next cycle delays each control phase by 2 pulses backward, thus correcting the deviation generated in the present cycle, and the phase is not deviated from the next cycle. After the pressure is reduced, the belt is elastically contracted, the rotation phase of the cam is advanced, the detection time of the sensor is advanced, and the pulse count actually measured after a single period is reduced, for example 998. Then a deviation of-2 pulses is generated. The next cycle advances each control phase by 2 pulses to correct the deviation.

In continuous operation of an infusion pump, the pressure is dynamically changed and difficult to predict due to different chromatographic column environments, different solutions, different flow rates and other factors. The dynamic deviation correcting method in the embodiment of the invention can fundamentally correct the direction and the deviation amount of the deviation from the real deviation degree calculated in real time without concern of the change of other conditions or environmental factors. The deviation amount can be calculated by a single circle, and the deviation amount can be corrected in the next period, so that the influence caused by the deviation can be reduced to the greatest extent.

In another embodiment, in addition to the origin position, 4 reference positions are defined in the practice of the present invention, and like the origin position, the 4 reference positions are also fixed positions that can be detected. As shown in fig. 5, sen1 and Sen2 may constitute 4 states. The timing of the phase interval A, B, C, D shift can locate 4 phase positions, specifically: d- > A:0 °; a- > B:90 °; b- > C:180 °; c- > D:270 deg.. As shown in fig. 6, 0 °, 90 °, 180 °, 270 ° are 4 reference positions.

TABLE 1

In the method for correcting dynamic deviation, the deviation is detected and corrected every 1/4 turn by taking 4 reference positions as references. The 4 reference positions are respectively a first reference position corresponding to a 0-degree phase position, a second reference position corresponding to a 90-degree phase position, a third reference position corresponding to a 180-degree phase position and a fourth reference position corresponding to a 270-degree phase position. The specific method is the same as the above embodiment except that the angle and pulse are 1/4 of the above embodiment. The method of the present embodiment can perform correction earlier than the above embodiment, and further reduce the influence of the deviation. The specific method comprises the following steps:

s201, acquiring a single deviation value.

Based on the step angle and the gear ratio of the stepper motor, the number of pulses of the theoretical cam rotation period can be calculated. Each datum position is positioned as a fixed mechanism and can be used as a reference datum. The pulse deviation direction and the deviation amount of the current 1/4 period can be calculated by the accumulated pulse number reaching the reference position every 1/4 period.

In a specific implementation, S201 is performed according to the following steps:

s211, measuring the differential pulse number x1 from the first reference position to the starting position of the cam according to the cam action characteristic, and storing the differential pulse number x1 in a substrate memory.

S212, calculating the pulse number P of one cam cycle according to the step angle and the belt transmission ratio. The theoretical number of pulses between the respective reference positions is P/4 based on the characteristic that the four reference positions are uniformly divided.

And S213, when the pump is started, the pump is in a state of uncertain position, and the needle rotates until the sensor detects a first reference position (namely the original point position).

S214, after the x1 pulse is operated again, defining the starting point position, and clearing the current pulse count C1.

In S215, during the continuous rotation, the pulse counts C1 are accumulated, and when reaching the first reference position again, the accumulated pulses should be P-x1 theoretically, and a single period deviation Δ1=c1- (P-x 1) is defined.

S202, deviation amount judgment.

In a specific implementation, S202 is performed according to the following steps:

s221, calculating a single deviation amount every time the reference position is reached.

S222, the single-cycle deviation amount per cycle is accumulated and is denoted as accumulated deviation ΣΔ.

S223, judging whether the single-period deviation amount exceeds the limit or the accumulated deviation amount exceeds the limit, if yes, judging that the error exists, and stopping the operation; if not, the pulse count value is corrected.

Wherein the single period deviation amount exceeds the limit: Δ1> Th1 or Δ1< (-1) Th1; the cumulative deviation amount exceeds the limit: ΣΔ > Th or ΣΔ < (-1) Th; th1=p0.5% representing a single period deviation amount threshold; th=p×1%, and denotes an accumulated deviation amount threshold.

If the single cycle deviation amount is too large, or the accumulated deviation amount is too large, there is a possibility that the stepping motor is out of step, in which the motor torque is insufficient. And judging that the operation is wrong, and stopping the operation.

S203, deviation correction (pulse count value correction): the count value from one reference position to the next reference position is C1, corrected to 1/4P, cleared for re-counting, corrected again to 1/4P until the next reference position is reached, and so on.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.

Claims

1. The dynamic deviation correcting method for the liquid chromatograph infusion pump is characterized in that the liquid chromatograph infusion pump comprises a position detecting mechanism for detecting the fixed position of a cam; the fixed position at least comprises an origin position; the method comprises the following steps:

2. The method for dynamic bias correction of a liquid chromatograph infusion pump of claim 1, wherein the liquid chromatograph infusion pump is a tandem double plunger pump.

3. The method for correcting dynamic deviation of a liquid chromatograph infusion pump according to claim 1 or 2, wherein the position detection mechanism includes: the light shielding sheet, the fixing part, the first photoelectric sensor and the second photoelectric sensor; the anti-dazzling screen is arranged on a cam shaft of the infusion pump of the liquid chromatograph and can synchronously rotate along with the cam; the first photoelectric sensor and the second photoelectric sensor are arranged at the fixing part in an up-down arrangement mode, are fixed in position and do not rotate; the radius of the shading sheet has 3 specifications of long, medium and short, and the long specification can shade the first photoelectric sensor and the second photoelectric sensor; the first photoelectric sensor is not shielded, and the second photoelectric sensor is shielded by the medium specification; the short specification enables neither the first photosensor nor the second photosensor to be shielded.

4. The method for dynamic bias correction of a liquid chromatograph infusion pump according to claim 3, wherein the fixed position includes an origin position; the position detection mechanism detecting the origin position includes:

5. The method for dynamic bias correction of a liquid chromatograph infusion pump according to claim 3, wherein the fixed positions include 4 reference positions; the position detection mechanism detecting a reference position includes:

6. The method for correcting dynamic deviation of an infusion pump for a liquid chromatograph according to claim 4 or 5, wherein calculating the pulse deviation direction and the deviation amount of the current cycle includes:

7. The method according to claim 4, wherein the correction period is each turn based on the origin position.

8. The method according to claim 5, wherein the correction period is 1/4 turn based on the 4 reference positions.