Dynamic deviation correction method for liquid chromatography infusion pump

Abstract

The application provides a dynamic deviation correction method of a liquid chromatograph infusion pump, the liquid chromatograph infusion pump comprising a position detection mechanism for detecting a fixed position of a cam; first, the difference pulse number from the fixed position to the start position of the cam is measured according to the cam action characteristics; the theoretical pulse number of the cam rotation per correction period is calculated according to the stepping angle of the stepping motor and the transmission ratio; the pulse deviation direction and the deviation amount of the current period are calculated through the cumulative pulse number reaching the fixed position per period; whether the single deviation amount overrun or the cumulative deviation amount overrun is triggered is judged, if not, the pulse count value correction is performed; the pulse count value correction comprises: the recorded count value when reaching the fixed position is corrected to the theoretical pulse number of the correction period. In the application, the dynamic deviation correction does not care about the change of other conditions or environmental factors, and the deviation direction and the deviation amount are fundamentally corrected from the real deviation degree calculated in real time.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of liquid chromatography, in particular to a dynamic deviation correction method for a liquid chromatography infusion pump. BACKGROUND

[0002] A high-performance liquid chromatograph is an instrument that uses chromatographic separation principles, a high-pressure infusion pump pushes a mobile phase into the system, a sample injector injects a sample solution into the mobile phase, a chromatographic column separates the sample, and a detector analyzes each component. The high-pressure infusion pump is a device that drives the mobile phase, and a cam is usually used to control the suction and discharge of the high-pressure infusion pump. During the control process, multiple links require the phase accuracy of the cam action. For example, the action coordination between the two plunger pumps depends on the phase design and accuracy of the cam control. The control of low-pressure gradients usually controls the opening time of each proportional valve according to the set proportion, and the phase accuracy of the cam action is very high. If the phase matching is not good, it may cause a decrease in the accuracy of proportional control, gas mixing, and damage to the device. In addition, in order to control the pressure pulsation in the entire action period, the speed change control according to the cam phase also requires high accuracy of the cam phase. A one-way valve is often used as a liquid flow one-way delivery control between the two plunger pumps. When there is a pressure difference between the two plunger pumps, there is a delay in the opening of the one-way valve. The control timing to eliminate the opening delay of the one-way valve also needs to be matched with the cam phase. If the phase matching is not good, it may cause fluctuations in flow rate and pressure, affecting the stability of the chromatographic system.

[0003] Currently, the controller of the infusion pump usually uses photoelectric sensors, encoders, pulse counting, and other methods to determine the rotation starting point and phase. However, in actual applications, when the infusion pump is continuously running, different system pressure environments, load conditions, and cumulative deviations caused by long-term operation, the phase deviation results in a deviation between the cam phase recognized by the controller and the actual phase of the cam mechanism. The controller controls according to the recognized phase, which may cause inconsistent control results between the mechanism and the expectation. The reasons for the phase deviation are as follows:

[0004] (1) The motor drives the cam shaft through the belt, and the belt has a certain stretchability. When the system pressure increases or the load increases, the belt is stretched, causing a phase deviation between the motor and the cam shaft.

[0005] (2) During long-term operation of the stepper motor, there may be occasional individual pulse out-of-step, which accumulates and causes a phase deviation between the motor and the cam shaft. SUMMARY

[0006] Therefore, the application provides a dynamic deviation correction method of a liquid chromatography infusion pump, which can automatically correct the dynamic phase deviation of a cam shaft of the liquid chromatography infusion pump in each action cycle, and improve the phase accuracy of cam action.

[0007] To this end, the application provides the following technical solutions:

[0008] The application provides a dynamic deviation correction method of a liquid chromatography infusion pump, the liquid chromatography infusion pump comprising a position detection mechanism for detecting a fixed position of a cam; the fixed position at least comprising an origin position; the method comprising:

[0009] According to the step motor step angle and the transmission ratio, the theoretical pulse number of cam rotation in each correction cycle is calculated;

[0010] The pulse deviation direction and deviation amount of the current cycle are calculated through the cumulative pulse number reaching the origin position in each cycle; each cycle comprises one or more correction cycles;

[0011] It is judged whether the single-cycle deviation amount overrun or cumulative deviation amount overrun is triggered, if yes, it is determined as an error, and the action is stopped; if not, the pulse count value is corrected;

[0012] Wherein, the single-cycle deviation amount overrun: Δ>Th1 or Δ<(-1)*Th1; the cumulative deviation amount overrun: ∑Δ>Th or ∑Δ<(-1)*Th; Δ represents the deviation amount, Th1=P*0.5%, indicating the single-cycle deviation amount threshold; ∑Δ represents the cumulative deviation, Th=P*1%, indicating the cumulative deviation amount threshold;

[0013] The pulse count value correction comprises: correcting the recorded count value when reaching the fixed position to the theoretical pulse number of the correction cycle.

[0014] Further, the liquid chromatography infusion pump is a tandem double-plunger pump.

[0015] Further, the position detection mechanism comprises: a light shield, a fixed part, a first photoelectric sensor and a second photoelectric sensor; wherein the light shield is installed on the cam shaft of the liquid chromatography infusion pump and can rotate synchronously with the cam; the first photoelectric sensor and the second photoelectric sensor are installed on the fixed part and arranged in an up-down manner, fixed in position and not rotating; the light shield radius has three specifications of long, medium and short, the long specification can make the first photoelectric sensor and the second photoelectric sensor both be shielded; the medium specification can make the first photoelectric sensor not be shielded and the second photoelectric sensor be shielded; and the short specification can make the first photoelectric sensor and the second photoelectric sensor both not be shielded.

[0016] Further, the fixed position comprises an origin position; and the position detection mechanism detecting the origin position comprises:

[0017] The shade fixed on the camshaft rotates synchronously with the camshaft clockwise;

[0018] The shade outer circle front edge relative to the first photoelectric sensor from the unshielded state to the just shielded state is the original position of the camshaft rotation.

[0019] Further, the fixed position includes four reference positions; the position detection mechanism detects the reference position including:

[0020] The shade fixed on the camshaft rotates synchronously with the camshaft clockwise;

[0021] The shade outer circle front edge relative to the first photoelectric sensor from the unshielded state to the just shielded state, and the shade outer circle front edge relative to the second photoelectric sensor is in the shielded state, corresponding to the first reference position of the camshaft rotation;

[0022] The shade outer circle front edge relative to the first photoelectric sensor from the unshielded state to the just shielded state, and the shade outer circle front edge relative to the second photoelectric sensor is in the shielded state, corresponding to the first reference position of the camshaft rotation;

[0023] The shade outer circle front edge relative to the first photoelectric sensor is in the unshielded state, and the shade outer circle front edge relative to the second photoelectric sensor from the shielded state to the just unshielded state, corresponding to the third reference position of the camshaft rotation;

[0024] The shade outer circle front edge relative to the first photoelectric sensor is in the unshielded state, and the shade outer circle front edge relative to the second photoelectric sensor from the shielded state to the just unshielded state, corresponding to the third reference position of the camshaft rotation;

[0025] Further, the direction and amount of pulse deviation of the current period are calculated, including:

[0026] According to the cam action characteristics, the difference pulse number from the fixed position to the starting position of the cam is measured;

[0027] When the pump is just started, it is in a position uncertain state, and rotates clockwise until the position detection mechanism detects the original position or the first reference position;

[0028] After the difference pulse number of pulses, defined as the starting position, the current pulse count is cleared;

[0029] In the continuous rotation, the pulse count is accumulated, and when the original position or the first reference position is reached again, the theoretical cumulative pulse is the theoretical pulse number of each period minus the difference pulse number, and the single deviation amount is the actual cumulative pulse minus the theoretical cumulative pulse; The positive and negative of the single deviation amount indicates the deviation direction.

[0030] Further, the correction period is every 1 / 4 circle based on the four reference positions.

[0031] Further, the correction period is every 1 / 4 circle based on the four reference positions.

[0032] Advantages and positive effects of the present application: In the continuous operation of the infusion pump, due to the different chromatographic column environment, different eluent, different flow rate and other factors, the pressure is dynamically changing and difficult to predict. The dynamic deviation correction of the present method can not care about the changes of other conditions or environmental factors, and start from the real deviation degree calculated in real time to fundamentally correct the deviation direction and deviation amount. Moreover, the deviation amount can be calculated in a single circle or even 1 / 4 circle, and the correction is performed in the next correction period (1 circle or 1 / 4 circle), which can minimize the influence of deviation. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0034] Figure 1 It is a schematic diagram of a tandem double-plunger pump in the embodiment of the present application;

[0035] Figure 2 It is a schematic diagram of a position detection mechanism installed on a camshaft in the embodiment of the present application;

[0036] Figure 3 It is a cam rotation period position diagram in the embodiment of the present application;

[0037] Figure 4 It is a dynamic deviation correction flowchart in the embodiment of the present application;

[0038] Figure 5 It is a state diagram of the first photoelectric sensor Sen1 and the second photoelectric sensor Sen2 in the embodiment of the present application;

[0039] Figure 6 It is a schematic diagram of four reference positions for deviation detection in the embodiment of the present application. DETAILED DESCRIPTION

[0040] In the following, the technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application, so that those skilled in the art can better understand the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work should fall within the protection scope of the present application.

[0041] It should be noted that the terms "first", "second" and the like in the description and claims of the present application and the above drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0042] The high-pressure infusion pump of the high-performance liquid chromatograph adopts a tandem double-plunger pump. Figure 1 As shown in the figure, the tandem double-plunger pump includes a driving motor 1, a transmission belt 2, a cam shaft 3, a first cam 4, a second cam 5, a first plunger rod 6, a second plunger rod 7, a first plunger pump 8, a second plunger pump 9, a first one-way valve 10, a second one-way valve 11, a pressure sensor 12, a liquid suction inlet 13 and a liquid discharge outlet 14. The driving motor 1 rotates, drives the cam shaft 3 to rotate through the transmission belt 2, the two cams (the first cam 4 and the second cam 5) on the cam shaft 3 rotate synchronously, drive the first plunger rod 6 of the first plunger pump 8 and the second plunger rod 7 of the second plunger pump 9 to reciprocate respectively, and the plunger rod is drawn out and pushed into the plunger pump to form the liquid suction and liquid pushing effect. The first one-way valve 10 is arranged on the liquid suction side of the first plunger pump 8 and the liquid suction side of the second plunger pump 9, and the first one-way valve 10 only allows the liquid flow from the liquid suction inlet 13 to the first plunger pump 8. The second one-way valve 11 is designed between the first plunger pump 8 and the second plunger pump 9, and the second one-way valve 11 only allows the liquid flow from the first plunger pump 8 to the second plunger pump 9. The pressure sensor 12 is connected to the liquid discharge outlet 14 of the second plunger pump 9, and can monitor the pressure in the rear-end pipeline.

[0043] In the tandem double-plunger pump in the embodiments of the present application, a position detection mechanism for detecting the original position is additionally arranged on the cam shaft. Figure 2As shown, the position detection mechanism includes: a light shield 100, a fixed part 200, a first photosensor (Sen1) 300 and a second photosensor (Sen2) 400. Among them, the light shield 100 is installed on the camshaft 3 and can rotate synchronously with the cam. The fixed part 200 is equipped with Sen1 and Sen2, two photosensors arranged up and down, fixed in position and not rotating. The light shield radius has three specifications: long, medium and short. In the "long" position, Sen1 and Sen2 are both shielded; in the "medium" position, Sen1 is not shielded and Sen2 is shielded; in the "short" position, Sen1 and Sen2 are both not shielded.

[0044] In the working process of the tandem double-plunger pump, the driving motor rotates to drive the camshaft to rotate clockwise through the transmission belt. The light shield fixed on the camshaft rotates clockwise synchronously with the camshaft. The outer circle leading edge of the light shield is just shielded relative to Sen1 from the unshielded state (as shown in the right figure), which is defined as the origin of the camshaft rotation (corresponding to the 0° phase position). Figure 2

[0045] As shown in Figure 3 , the relative position of the camshaft rotation period is shown. Starting from the starting position, the pulse is counted from 1; after one rotation, the starting position is reached again, and the pulse count is P; the pulse number of the photosensor origin position from the starting position is x. The origin position is designed to be slightly ahead of the phase of the starting position of the cam stroke. Due to the deviation during assembly of each pump, the pulse number x of the difference between the origin position of the photosensor and the starting position is measured by a phase measuring device after assembly and saved in the control substrate as a control parameter.

[0046] Based on the tandem double-plunger pump with the position detection mechanism described above, the present application provides a method for correcting dynamic deviation.

[0047] In one embodiment, as shown in Figure 4 , in the method for correcting dynamic deviation, the deviation detection and correction are performed every cycle based on the origin position, i.e. the correction period is one cam cycle. Specifically, the following steps are included:

[0048] S101, acquiring a single deviation value.

[0049] According to the step angle of the stepper motor and the transmission ratio, the pulse number of the theoretical cam rotation period can be calculated. The origin position as a fixed mechanism positioning can be used as a reference. Through the cumulative pulse number of each cycle reaching the origin position, the pulse deviation direction and deviation amount of the current cycle can be calculated.

[0050] In specific implementation, S101 is performed according to the following steps:

[0051] ​S111, according to the cam action characteristics, measure the difference pulse number x from the original point position to the start point position of the cam, and save it into the substrate memory.

[0052] S112, according to the step angle and the belt transmission ratio, calculate the pulse number P of a cam period.

[0053] S113, when the pump is just started, it is in a position uncertain state, and the needle is rotated until the sensor detects the original point position.

[0054] S114, define the start point position after the action x pulse, and clear the current pulse count C.

[0055] S115, in the continuous rotation, the pulse count C is accumulated, and when the original point position is reached again, the accumulated pulse should be P-x in theory, and the single deviation amount Δ0=C-(P-x) is defined.

[0056] For example: the theoretical pulse number of a single period is 1000, and the actual pulse count between the two times through the original point position sensor is 1002. Then a deviation of +2 pulses is generated.

[0057] The direction of the deviation can be determined by the positive and negative of the deviation, and the degree of the deviation can be determined by the size of the deviation. These information can be used as the basis for error judgment and deviation dynamic correction.

[0058] S102, deviation amount judgment.

[0059] A large deviation of the mechanism may indicate a fault of the electrical control part or a blockage of the pipeline, which needs to be fed back to the user in time and repaired to avoid affecting the normal analysis work of the user. The error can be detected in time and effectively indicated by the deviation value judgment.

[0060] In specific implementation, S102 is executed according to the following steps:

[0061] S121, calculate the single deviation amount each time the original point position is reached.

[0062] S122, accumulate the single deviation amount of each period, and record it as the accumulated deviation amount ∑Δ.

[0063] S123, judge whether the single deviation amount exceeds the limit or the accumulated deviation amount exceeds the limit, if yes, judge as an error and stop the action; if not, correct the pulse count value.

[0064] Wherein, the single deviation amount exceeds the limit: Δ0>Th1 or Δ0<(-1)*Th1; the accumulated deviation amount exceeds the limit: ∑Δ>Th or ∑Δ<(-1)*Th; Th1=P*0.5%, indicating the single deviation amount threshold; Th=P*1%, indicating the accumulated deviation amount threshold.

[0065] If the single deviation amount is too large, or the cumulative deviation amount is too large, it is possible that the stepping motor is out of step due to insufficient motor torque. The determination is an error, and the operation is stopped.

[0066] If the stepping motor torque is insufficient or even stuck, a single positive deviation or the origin position sensor detection timeout will occur.

[0067] S103, deviation correction (pulse count value correction): the count value when reaching the origin position is C, which is corrected to P-x, and the counting continues until P is reached, and the next cycle is started with zero reset.

[0068] For example: P=12000, x=100, C=11903, C is changed to 12000-100=11900, and the operation continues and the count is accumulated. When C reaches 12000, C is reset to zero, and the next cycle is restarted.

[0069] In a single cycle, due to pressure increase and belt stretching, a single deviation value will occur. According to the theoretical deviation value, the correction of the operation pulse can correct the phase of the deviation. It ensures that the operation phase is consistent with the design. When the pressure decreases and the belt contracts, a reverse single deviation value will occur. According to the same principle, the deviation phase is dynamically corrected. In this way, the accuracy of the phase can be ensured in each cam cycle.

[0070] For example: the theoretical pulse number of a single cycle is 1000. Due to pressure increase and belt stretching, the cam rotation phase is delayed, the sensor detection time is delayed, and the actual measured pulse count between the two origin position sensors is increased, for example 1002. Then a +2 pulse deviation occurs. In the next cycle, each control phase is delayed by 2 pulses, which corrects the deviation generated in this cycle, and there is no deviation in the phase from the next cycle. After the pressure decreases, the belt contracts elastically, the cam rotation phase is advanced, the sensor detection time is advanced, and the actual measured pulse count through a single cycle is reduced, for example 998. Then a -2 pulse deviation occurs. In the next cycle, each control phase is advanced by 2 pulses to correct the deviation.

[0071] In continuous operation of the infusion pump, due to different chromatographic column environments, different elution solutions, different flow rates, and other factors, the pressure is dynamically changing and difficult to predict. The dynamic deviation correction method in the embodiment of the present application can not care about the changes of other conditions or environmental factors, and can correct the direction and amount of deviation based on the real-time calculation of the actual deviation degree. Moreover, the deviation amount can be calculated in a single cycle, and the correction can be made in the next cycle, which can minimize the impact of deviation.

[0072] In another embodiment, in addition to the origin position, four reference positions are defined in the embodiment of the present application, which are similar to the origin position and can also be detected fixed positions. For example,Figure 5 As shown, Sen1 and Sen2 can constitute 4 states. The timing of phase interval A, B, C, D switching can locate 4 phase positions, specifically: D->A: 0°; A->B: 90°; B->C: 180°; C->D: 270°. As shown, 0°, 90°, 180°, 270° are 4 reference positions. Figure 6 As shown, 0°, 90°, 180°, 270° are 4 reference positions.

[0073] Table 1

[0074]

[0075]

[0076] In the method of correcting dynamic deviation, deviation detection and correction are performed every 1 / 4 cycle based on 4 reference positions. The 4 reference positions are respectively a first reference position corresponding to a 0° phase position, a second reference position corresponding to a 90° phase position, a third reference position corresponding to a 180° phase position, and a fourth reference position corresponding to a 270° 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 in this embodiment can correct earlier than the above embodiment, further reducing the influence of deviation. The specific method includes the following steps:

[0077] S201, obtaining a single deviation value.

[0078] According to the step angle of the stepper motor and the transmission ratio, the number of pulses of the theoretical cam rotation period can be calculated. Each reference position is a fixed mechanism positioning, which can be used as a reference. Through the cumulative pulse number of each 1 / 4 cycle reaching the reference position, the pulse deviation direction and deviation amount of the current 1 / 4 cycle can be calculated.

[0079] In specific implementation, S201 is performed according to the following steps:

[0080] S211, according to the cam action characteristics, measure the differential pulse number x1 from the first reference position to the starting position, and save it into the substrate memory.

[0081] S212, according to the step angle and the belt transmission ratio, calculate the number of pulses P of one cam period. According to the characteristics of uniform division of four reference positions, the theoretical pulse number between each reference position is P / 4.

[0082] S213, when the pump is just started, it is in a position uncertain state, and it is naturally rotated until the sensor detects the first reference position (i.e. the origin position).

[0083] S214, after moving x1 pulses, define it as the starting position, and clear the current pulse count C1.

[0084] S215, in the continuous rotation, the pulse count C1 accumulates, and when reaching the first reference position again, the accumulated pulse should be P-x1 in theory, and the single-cycle deviation amount Δ1 is defined as C1-(P-x1).

[0085] The direction of the deviation can be determined by the positive and negative of the deviation, and the degree of the deviation can be determined by the size of the deviation. These information can be used as the basis for error determination and deviation dynamic correction.

[0086] S202, deviation amount determination.

[0087] In a specific implementation, S202 is performed according to the following steps:

[0088] S221, single-cycle deviation amount is calculated each time the reference position is reached.

[0089] S222, the single-cycle deviation amount of each cycle is accumulated, and is recorded as the accumulated deviation amount ∑Δ.

[0090] S223, it is determined whether the single-cycle deviation amount exceeds the limit or the accumulated deviation amount exceeds the limit, if yes, it is determined as an error and the action is stopped; if no, the pulse count value is corrected.

[0091] Wherein, the single-cycle deviation amount exceeds the limit: Δ1>Th1 or Δ1<(-1)*Th1; the accumulated deviation amount exceeds the limit: ∑Δ>Th or ∑Δ<(-1)*Th; Th1=P*0.5%, indicating the single-cycle deviation amount threshold; Th=P*1%, indicating the accumulated deviation amount threshold.

[0092] If the single-cycle deviation amount is too large, or the accumulated deviation amount is too large, it may be a step motor out of step with insufficient motor torque. It is determined as an error and the action is stopped.

[0093] If the stepping motor torque is insufficient or even stuck, the positive deviation of a single turn or the original position sensor detection timeout may occur.

[0094] S203, deviation correction (pulse count value correction): the count value from one reference position to the next reference position is C1, which is corrected to 1 / 4P, and is cleared and counted again, until the next reference position is reached, and is corrected to 1 / 4P again, and so on.

[0095] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for correcting dynamic deviation of a liquid chromatograph infusion pump, characterized in that, The liquid chromatograph infusion pump comprises a position detection mechanism for detecting fixed positions of a cam; the fixed positions at least include an origin position; the method comprises: According to the step motor step angle and the transmission ratio, the theoretical pulse number of the cam rotation per correction period is calculated; The pulse deviation direction and deviation amount of the current period are calculated through the cumulative pulse number reaching the origin position per period; each period includes one or more correction periods; It is judged whether the single-period deviation amount exceeds the limit or the cumulative deviation amount exceeds the limit, if yes, it is determined as an error and the action is stopped, if not, the pulse count value is corrected; Wherein, the single-period deviation amount exceeds the limit: Δ>Th1 or Δ<(-1)*Th1; the cumulative deviation amount exceeds the limit: ∑Δ>Th or ∑Δ<(-1)*Th; Δ represents the deviation amount, Th1=P*0.5%, which represents the single-period deviation amount threshold; ∑Δ represents the cumulative deviation, Th=P*1%, which represents the cumulative deviation amount threshold; P represents the pulse number of one cam period; The pulse count value correction includes: correcting the recorded count value when reaching the fixed position to the theoretical pulse number of the correction period; Wherein, the position detection mechanism comprises: a light shield, a fixed part, a first photoelectric sensor and a second photoelectric sensor; wherein the light shield is installed on the cam shaft of the liquid chromatograph infusion pump and can rotate synchronously with the cam; the first photoelectric sensor and the second photoelectric sensor are installed on the fixed part and arranged in an up-down manner, fixed in position and not rotating; the light shield has three specifications of long, medium and short radius, the long specification can make the first photoelectric sensor and the second photoelectric sensor both be shielded; the medium specification can make the first photoelectric sensor not be shielded and the second photoelectric sensor be shielded; the short specification can make the first photoelectric sensor and the second photoelectric sensor both not be shielded; Wherein, the fixed positions include the origin position; the position detection mechanism detects the origin position, which comprises: The light shield fixed on the cam shaft rotates synchronously with the cam shaft clockwise; The state that the outer circle leading edge of the light shield just shields the first photoelectric sensor from the unshielded state is the origin position of the cam shaft rotation.

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

3. The method of dynamic bias correction for a liquid chromatography infusion pump of claim 1, wherein, The fixed positions include four reference positions; the position detection mechanism detects the reference positions, which comprises: The light shield fixed on the cam shaft rotates synchronously with the cam shaft clockwise; The state that the outer circle leading edge of the light shield switches from the unshielded state to the just-shielded state relative to the first photoelectric sensor and is shielded relative to the second photoelectric sensor corresponds to the first reference position of the cam shaft rotation; The state that the outer circle leading edge of the light shield switches from the shielded state to the just-unshielded state relative to the first photoelectric sensor and is shielded relative to the second photoelectric sensor corresponds to the second reference position of the cam shaft rotation; The state that the outer circle leading edge of the light shield is unshielded relative to the first photoelectric sensor and switches from the shielded state to the just-unshielded state relative to the second photoelectric sensor corresponds to the third reference position of the cam shaft rotation; The front edge of the shade outer ring is in an unshielded state relative to the first photosensor, and the front edge of the shade outer ring is switched from the unshielded state to the just shielded state relative to the second photosensor, corresponding to the fourth reference position of the rotation of the camshaft.

4. The method of dynamic bias correction of a liquid chromatography fluid delivery pump of claim 1 or 3, wherein, The pulse deviation direction and deviation amount of the current period are calculated, including: According to the cam action characteristics, the differential pulse number from the fixed position to the starting position of the cam is measured; When the pump is just started, it is in a position uncertain state, and the needle is rotated, until the position detection mechanism detects the origin position or the first reference position; After moving the differential pulse number of pulses, the starting position is defined, and the current pulse count is cleared. During continuous rotation, the pulse count is accumulated, and when the origin position or the first reference position is reached again, the theoretical cumulative pulse is the theoretical pulse number per period minus the differential pulse number, and the single deviation amount is the actual cumulative pulse minus the theoretical cumulative pulse; The positive and negative of the single deviation amount indicates the deviation direction.

5. The method of dynamic bias correction for a liquid chromatography fluid delivery pump of claim 1, wherein, Taking the origin position as the reference, the correction period is every circle.

6. The method of dynamic bias correction for a liquid chromatography fluid delivery pump of claim 3, wherein, Taking the four reference positions as the reference, the correction period is every 1 / 4 circle.

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