CN111408420A - Precision control method of electronic pipettor - Google Patents
Precision control method of electronic pipettor Download PDFInfo
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- CN111408420A CN111408420A CN201910013560.3A CN201910013560A CN111408420A CN 111408420 A CN111408420 A CN 111408420A CN 201910013560 A CN201910013560 A CN 201910013560A CN 111408420 A CN111408420 A CN 111408420A
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- 238000000034 method Methods 0.000 title claims abstract description 34
- 239000007788 liquid Substances 0.000 claims abstract description 22
- 230000008569 process Effects 0.000 claims description 5
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- 238000004804 winding Methods 0.000 claims description 4
- 238000012544 monitoring process Methods 0.000 claims description 3
- 238000012546 transfer Methods 0.000 description 6
- 230000007246 mechanism Effects 0.000 description 3
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
- B01L3/00—Containers or dishes for laboratory use, e.g. laboratory glassware; Droppers
- B01L3/02—Burettes; Pipettes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
- B01L2400/00—Moving or stopping fluids
- B01L2400/04—Moving fluids with specific forces or mechanical means
- B01L2400/0403—Moving fluids with specific forces or mechanical means specific forces
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Abstract
The invention discloses a precision control method of an electronic pipettor, which comprises the following steps: s1: acquiring a linear relation between the rotating speed and the overshoot of a motor of the electronic pipettor during braking; s2: calculating the number of turns of the corresponding motor according to the volume of the liquid to be removed so as to determine the stop position; s3: and after the pipetting is started, the number of rotation turns of the motor and the rotating speed of the motor are monitored, the overshoot corresponding to the current rotating speed is braked in advance in a braking mode, and the motor stops at the stop position of the step S2 after the motor continuously runs the overshoot through inertia. According to the precision control method of the electronic pipettor, the rotating speed and the overshoot of the motor are calculated and monitored, so that the motor can be accurately positioned, the error is extremely small, and the stability is extremely high; the motor is braked by induced electromotive force of the motor, any additional braking device is not needed, the realization is simple, and the occupied space is small.
Description
Technical Field
The invention relates to the field of pipettors, in particular to a precision control method of an electronic pipettor.
Background
The pipettor is mainly used for operations such as moving, taking and distributing liquid, is the most commonly used instrument in a laboratory, and the liquid moving accuracy of the pipettor has an important influence effect on an experimental result. When the traditional manual pipettor is used, the operation experience and the skill of an operator have great influence on the accuracy and the stability of the pipettor; the electronic pipettor is controlled by a program, and has many advantages of high precision, good stability and the like compared with a manual pipettor, so the electronic pipettor is generally favored by users. For an electronic pipettor, at present, the precision control of pipetting is mainly realized by controlling the stalling and positioning of a motor, and at present, the following two realization modes are common:
the implementation mode is as follows: an electronic brake is used. The implementation mode is that a code wheel with a groove is fixed on a rotating shaft of a motor, and after the motor rotates to drive a piston to move to a set capacity, a program control electromagnet extends out of a brake rod to the groove to stop the motor. This approach has the following disadvantages: 1. the electromagnet realizes the extension and retraction of the brake rod through the principle of electromagnetic conversion so as to achieve the purpose of controlling the motor to stop, but the electromagnet has large volume and needs to occupy larger installation space; in addition, the electromagnetic brake has larger power consumption, so that the service life of a liquid transfer device powered by a battery is greatly limited, and the liquid transfer device is difficult to accept by experimenters; 2. because the code wheel with the groove is often used as a brake notch and an encoder of the motor, and the code wheel and the motor must be fixed at the same time, the structural design difficulty of the product is increased; 3. the action principle of the electronic brake is similar to that of mechanical brake, and the more the electronic brake is used, the greater the influence on the service life, stability and reliability of the machine is. Therefore, in the actual use process, the electric pipettor is difficult to manufacture in batches and popularize and use in the market.
The implementation mode two is as follows: the motor of the electronic pipettor is a stepping motor, the rotating speed and the stopping position of the stepping motor only depend on the frequency and the pulse number of the pulse signal and are not influenced by load change, when the stepping driver receives the pulse signal, the stepping motor is driven to rotate by a fixed angle according to the set direction, but the rotating speed of the stepping motor is very low, so that the pipetting efficiency is low, and more time is consumed for pipetting each time.
Disclosure of Invention
Therefore, the technical problem to be solved by the invention is to overcome the defects of the existing electronic pipettor and further provide a precision control method of the electronic pipettor.
In order to achieve the purpose, the invention adopts the following technical scheme:
a precision control method of an electronic pipettor comprises the following steps:
s1: acquiring a linear relation between the rotating speed and the overshoot of a motor of the electronic pipettor during braking;
s2: calculating the number of turns of the corresponding motor according to the volume of the liquid to be removed so as to determine the stop position;
s3: and after the pipetting is started, the number of rotation turns of the motor and the rotating speed of the motor are monitored, the overshoot corresponding to the current rotating speed is braked in advance in a braking mode, and the motor stops at the stop position of the step S2 after the motor continuously runs the overshoot through inertia.
Preferably, the braking mode in step S3 is to cut off the power supply of the motor and make the motor winding form a closed loop, and the current generated in the closed loop makes the motor instantly generate a very large braking torque to achieve rapid braking of the motor.
Preferably, the motor is a coreless rotor motor.
Preferably, the motor is a dc coreless motor.
Preferably, the motor is a brushed dc coreless motor or a brushless dc coreless motor.
Preferably, the braking manner in step S3 is short-circuit braking or dynamic braking.
Preferably, the rotation of the motor is a constant speed rotation.
Preferably, the working power supply of the motor is provided by a voltage stabilizing circuit and does not fluctuate along with fluctuation of the power supply of the pipettor.
Preferably, the calibration data is updated after monitoring the rotational speed and brake overshoot at the time of braking during each pipetting.
The invention has the beneficial effects that:
according to the precision control method of the electronic pipettor, the rotating speed and the overshoot of the motor are calculated and monitored, so that the motor can be accurately positioned, the error is extremely small, and the stability is extremely high; the motor is braked by induced electromotive force of the motor, any additional braking device is not needed, the realization is simple, and the occupied space is small; the precision control method of the electronic pipettor adopts the direct current motor to drive the liquid suction, and the pipetting efficiency is high.
Drawings
In order that the present invention may be more readily and clearly understood, reference is now made to the following detailed description taken in conjunction with the accompanying drawings, in which:
fig. 1 is a functional block diagram of a method of precision control of an electronic pipette of the present invention;
fig. 2 is a diagram of the correspondence between the overshoot amount of the motor and the motor rotation speed in the present embodiment.
Detailed Description
The electronic pipettor adopted by the invention comprises a motor, a microprocessor, a transmission piece, a piston and the like, the motor is controlled by a program to rotate, the rotating motion of the motor is converted into the linear motion of the piston through the conversion of the transmission piece, and the liquid transfer is realized through the air replacement principle or the external piston principle; for a set pipetting capacity, the following relationship exists with the number of turns of the motor:
volume is the sectional area and the lead screw stroke is 1 formula
Lead screw stroke (lead screw pitch) lead screw rotation number 2 type
Mechanism rotation speed ratio 3 formula with lead screw rotation number of turns ═ motor number of turns-
Obtained by the formulas 1, 2 and 3:
capacity is the cross section area lead screw pitch mechanism speed ratio is the number of turns of motor
Referring to fig. 1, the method for controlling the accuracy of the electronic pipette specifically includes the following steps:
s1: acquiring a linear relation between the rotating speed and the overshoot of a motor of the electronic pipettor during braking (see fig. 2);
s2: calculating the number of turns of the corresponding motor according to the volume of the liquid to be removed so as to determine the stop position;
s3: and after the pipetting is started, the number of rotation turns of the motor and the rotating speed of the motor are monitored, the overshoot corresponding to the current rotating speed is braked in advance in a braking mode, and the motor stops at the stop position of the step S2 after the motor continuously runs the overshoot through inertia.
For the liquid transfer with the target capacity, when the program control motor runs to reach the target circle number, braking is carried out, the motor can still continue to rotate due to inertia after braking, the rotating quantity exceeding the braking position is the overshoot, the target circle number of the motor rotation and the number of the over-impulse rotating circles (the over-impulse visual expression is that a certain overshoot angle is provided, and the process angle is converted into the circle number) jointly drive the liquid extracted by the piston of the liquid transfer machine to be the target liquid transfer quantity.
The braking mode of the invention is that the power supply of the rotating motor is cut off and the winding of the motor forms a closed loop, so that the motor can instantaneously generate a great braking torque to achieve the purpose of rapid braking, but because of the inertia of the motor, the motor still has partial overshoot, by obtaining the linear relation between the rotating speed and the overshoot when the motor is braked, in the pipetting process, the program of the pipettor monitors the number of turns and the rotating speed of the motor in operation, and calculates the overshoot braking corresponding to the rotating speed, after the motor is completely stopped, the actual number of turns of the motor in operation is consistent with the set number of turns through the inertia of the motor, namely the target capacity, and the method can achieve very high control precision.
In order to further improve the pipetting precision of the pipettor adopting the method, the motor selected by the precision control method is a coreless rotor motor, and a direct current hollow cup motor is preferably selected, the motor can realize precise real-time positioning, the metering error that the stepping motor rotates a certain stepping angle every time according to pulses is avoided, and the pipetting precision can be further improved.
The precision control method of the electronic pipettor is preferably short-circuit braking or energy-consumption braking for the braking mode of the motor, the specific short-circuit mode is not limited, and for the pipettor, as long as the power supply is adopted to cut off and the motor windings form a closed loop, the motor can instantly generate a great braking torque, and the purpose of quickly braking can be achieved.
The rotation of the motor is constant-speed rotation, wherein the constant-speed rotation refers to that the motor rotates at a constant speed every time the motor rotates, so that the rotation condition of the motor is convenient to count and control, but when liquid in different times or different quantities is removed, the rotating speed of the motor is different, if liquid in a larger volume needs to be removed, the rotating speed of the motor is higher, liquid in a smaller volume is removed, the rotating speed of the motor is lower, the faster the motor rotates, the larger the corresponding overshoot is, the slower the rotating speed of the motor is, the smaller the corresponding overshoot is, and the overshoot of the motor in the same model is slightly different, so that the method requires that each motor installed on a pipettor needs to be calibrated before being controlled according to the method. The working power supply of the motor is provided by the voltage stabilizing circuit, the working power supply does not fluctuate along with the fluctuation of the power supply of the liquid moving device, the specific form of the voltage stabilizing circuit is not limited, and the purpose of stabilizing the voltage can be achieved.
And monitoring the rotating speed and the brake overshoot during braking in each pipetting process, and then updating the calibration data. The corresponding relation between the rotating speed and the overshoot of the direct current motor with the diameter of 22mm determined by the invention is as follows:
| rotational speed (unit: rpm) | Overshoot (unit: number of turns) |
| 2500 | 0.3125 |
| 3000 | 0.3958 |
| 3500 | 0.4583 |
| 4000 | 0.5147 |
| 4500 | 0.625 |
| 5000 | 0.7083 |
| 5500 | 0.7708 |
| 6000 | 0.8542 |
| 6500 | 0.9375 |
| 7000 | 1.0625 |
| 7500 | 1.4583 |
The relationship between the overshoot and the motor speed in the above table can be processed by sampling or smoothing into a corresponding linear relationship, see fig. 2, and then according to the formula:
capacity is the cross section area lead screw pitch mechanism speed ratio is the number of turns of motor
Wherein, the number of turns of the motor is equal to the number of turns of the over impulse plus the number of turns of the motor during braking
And then calculate the motor and need rotate how many times and carry on the brake.
According to the precision control method of the electronic pipettor, the rotating speed and the overshoot of the motor are calculated and monitored, so that the motor can be accurately positioned, the error is extremely small, and the stability is extremely high; the motor is braked by induced electromotive force of the motor, any additional braking device is not needed, the realization is simple, and the occupied space is small; the precision control method of the electronic pipettor adopts the direct current motor to drive the liquid suction, and the pipetting efficiency is high.
The invention is not only applicable to electronic pipettors, but also to electric liquid handling devices including, but not limited to, electric suction aids, electric large capacity pipetting devices, pipette controllers, vial mouth dispensers, vial mouth pipetting devices, vial mouth dispensers, continuous injectors, vacuum pipetting devices, liquid handling workstations, and the like.
The above embodiments are merely to explain the technical solutions of the present invention in detail, and the present invention is not limited to the above embodiments, and it should be understood by those skilled in the art that all modifications and substitutions based on the above principles and spirit of the present invention should be within the protection scope of the present invention.
Claims (9)
1. A precision control method of an electronic pipettor is characterized in that: the method comprises the following steps:
s1: acquiring a linear relation between the rotating speed and the overshoot of a motor of the electronic pipettor during braking;
s2: calculating the number of turns of the corresponding motor according to the volume of the liquid to be removed so as to determine the stop position;
s3: and after the pipetting is started, the number of rotation turns of the motor and the rotating speed of the motor are monitored, the overshoot corresponding to the current rotating speed is braked in advance in a braking mode, and the motor stops at the stop position of the step S2 after the motor continuously runs the overshoot through inertia.
2. The method for controlling the accuracy of an electronic pipette according to claim 1, characterized in that: the braking mode in the step S3 is to cut off the power supply of the motor and make the motor winding form a closed loop, and the current generated in the closed loop makes the motor instantly generate a very large braking torque to achieve rapid braking of the motor.
3. The method for controlling the accuracy of an electronic pipette according to claim 1 or 2, characterized in that: the motor is a coreless rotor motor.
4. The method for controlling the accuracy of an electronic pipette according to claim 3, wherein: the motor is a direct current coreless motor.
5. The method for controlling the accuracy of an electronic pipette according to claim 3, wherein: the motor is a brush DC coreless motor or a brushless DC coreless motor.
6. The method for controlling the accuracy of an electronic pipette according to any one of claims 1 to 5, wherein: the braking mode in the step S3 is short-circuit braking or dynamic braking.
7. The method for controlling the accuracy of an electronic pipette according to any one of claims 1 to 6, wherein: the rotation of the motor is constant speed rotation.
8. The method for controlling the accuracy of an electronic pipette according to claim 7, wherein: the working power supply of the motor is provided by the voltage stabilizing circuit and does not fluctuate along with fluctuation of the power supply of the liquid moving device.
9. A method of controlling the accuracy of an electronic pipette according to any of claims 1 to 8, wherein: and monitoring the rotating speed and the brake overshoot during braking in each pipetting process, and then updating the calibration data.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910013560.3A CN111408420A (en) | 2019-01-07 | 2019-01-07 | Precision control method of electronic pipettor |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201910013560.3A CN111408420A (en) | 2019-01-07 | 2019-01-07 | Precision control method of electronic pipettor |
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| CN111408420A true CN111408420A (en) | 2020-07-14 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116618109A (en) * | 2023-04-13 | 2023-08-22 | 西安天隆科技有限公司 | Modular pipette driven by DC brushless servo system and control method thereof |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN2038159U (en) * | 1988-04-23 | 1989-05-24 | 王志云 | Power-driven hand-handle-type micropipet |
| CN1848664A (en) * | 2005-04-05 | 2006-10-18 | 深圳市兆伟科技开发有限公司 | Method for realizing precision positioning utilizing electric machine |
| US20100199789A1 (en) * | 2007-06-29 | 2010-08-12 | Rainin Instrument, Llc | Hybrid manual-electronic pipette |
| CN103920548A (en) * | 2014-04-23 | 2014-07-16 | 张建明 | Quantitative liquid transferring device |
| CN207271280U (en) * | 2017-09-08 | 2018-04-27 | 莫纳（苏州）生物科技有限公司 | Electronic craft sample injector |
| CN108375405A (en) * | 2018-01-29 | 2018-08-07 | 中国第汽车股份有限公司 | Liquid flow measurement device and measurement method |
-
2019
- 2019-01-07 CN CN201910013560.3A patent/CN111408420A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN2038159U (en) * | 1988-04-23 | 1989-05-24 | 王志云 | Power-driven hand-handle-type micropipet |
| CN1848664A (en) * | 2005-04-05 | 2006-10-18 | 深圳市兆伟科技开发有限公司 | Method for realizing precision positioning utilizing electric machine |
| US20100199789A1 (en) * | 2007-06-29 | 2010-08-12 | Rainin Instrument, Llc | Hybrid manual-electronic pipette |
| CN103920548A (en) * | 2014-04-23 | 2014-07-16 | 张建明 | Quantitative liquid transferring device |
| CN207271280U (en) * | 2017-09-08 | 2018-04-27 | 莫纳（苏州）生物科技有限公司 | Electronic craft sample injector |
| CN108375405A (en) * | 2018-01-29 | 2018-08-07 | 中国第汽车股份有限公司 | Liquid flow measurement device and measurement method |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116618109A (en) * | 2023-04-13 | 2023-08-22 | 西安天隆科技有限公司 | Modular pipette driven by DC brushless servo system and control method thereof |
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Application publication date: 20200714 |