Ultramicro dispensing device and method based on air pressure-vision double closed-loop control

Abstract

The invention provides an ultramicro dispensing device and method based on air pressure-vision double closed-loop control, and belongs to the technical field of micro-nano manufacturing, the device comprises an air source, a pressure reducing valve, a Venturi tube, an electronic pressure controller, an electromagnetic valve circuit, a digital-to-analog conversion module, a calculation module, an air pressure sensor, a dispensing needle tube, a vision module and a dispensing platform, the method comprises the following steps: detecting the diameter of a glue spot in real time by adopting a visual unit, dynamically identifying an air pressure-glue spot diameter nonlinear compensation model, and adjusting the air pressure of a dispensing needle tube by adopting a closed-loop controller to realize accurate control of the glue spot. Experimental results show that the glue spot control with the minimum diameter of 9.87 microns can be realized, the quantitative dispensing of 10 microns, 20 microns, 30 microns and 40 microns can be completed, the error is within 8.3%, and the glue spot control device has the advantages of high precision and high stability.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of micro-nano manufacturing technology, and particularly relates to an ultramicro dispensing device and method based on air pressure-vision double closed-loop control. BACKGROUND

[0002] Ultramicro dispensing technology is to dispense a proper size of glue spot through a dispensing needle to meet packaging requirements. According to whether the dispensing needle tip is in contact with the dispensing surface, the ultramicro dispensing technology can be divided into non-contact dispensing and contact dispensing. The non-contact dispensing is to make liquid spray on the dispensing surface at a certain speed through external force to form a droplet, which has been widely used in SMT chip packaging field and is suitable for batch planar dispensing occasions. The non-contact dispensing mainly includes piezoelectric driving, electromagnetic driving and pressure driving micro dispensers. The advantage of non-contact dispensing is that it does not need to consider the influence of the material of the dispensing surface on dispensing, and has good consistency. However, the size of the glue spot dispensed by the current non-contact dispensing is greater than 100 μm, and for a capillary injection tube (radius less than 3 μm), the surface tension that needs to be broken through by the non-contact dispensing is very large, and it is difficult to realize small dose dispensing task. At the same time, the non-contact dispensing is vertical dispensing, and when facing assembly tasks in complex situations, the horizontal injection speed needs to be considered, and the calibration is difficult.

[0003] The advantage of contact dispensing compared with non-contact dispensing is that it can be dispensed in a more complex environment. The contact dispensing includes spiral, piston, transfer and time-pressure types. The spiral and piston types respectively use a piston or a rotating screw to directly extrude the glue, and then make the liquid advance through the dispensing tip, and then retract to complete a dispensing cycle. However, the screw or mechanical piston has slow response, certain mechanical interference and glue damage to the structure, which affects the model accuracy. The transfer type is to dip the dispensing needle into the glue liquid and then contact the dispensing surface to complete the dispensing work. However, the transfer type dispensing cannot dynamically adjust the amount of glue liquid. The time-pressure type dispensing is connected with a pressure controller at the back end, and compared with other contact dispensing, the time-pressure type dispensing has the advantages of small front-end needle port (<5 μm) and flexible pressure control, and can dynamically adjust the dispensing amount by changing the pressure.

[0004] For time-pressure type air pressure controller, the common air pressure driving mode is based on the principle of syringe, which drives micro operation by adjusting the volume of gas in the syringe chamber through linear motion platform. With its simple operation characteristics, it has a wide application in the field of micro connection and micro operation, but it has the limitation of maximum gas capacity, and is not suitable for applications with large air demand. Moreover, it relies on pressure closed loop adjustment of mechanical shaft displacement. In this way, the air pressure dynamically changes continuously, and the pressure change curve is disturbed, resulting in poor consistency of dispensing. Another is a discrete pressure control system, in which a gas pump and a vacuum pump are used as the air source to generate positive and negative pressure respectively, and an electromagnetic valve is used to control the switching state and limit the flow direction in the pneumatic circuit. In this method, the pressure is controlled by the pressure regulating valve on the gas pump, and the electromagnetic valve is only used to switch the gas flow but not to control the pressure. Therefore, most pneumatic systems that rely mainly on electromagnetic valves are usually designed to deliver a single positive or negative pressure state, which restricts the movement of the actuator. Usually, these systems are applied in environments with simple movement requirements and moderate precision requirements, such as quantitative drug injection of zebrafish. Continuous pressure control systems are usually composed of a gas pump and a proportional valve. These valves accurately adjust the pressure of the actuator through a specific voltage signal, which is very suitable for high-precision micro connection occasions, has the advantages of stable pressure and rapid switching, and is suitable for ultra-micro quantitative dispensing occasions.

[0005] In summary, a dynamic adjustment of a small amount of sub-picoliter dispensing scheme for complex scene micro connection has not been reported, and it is urgently needed to be proposed. SUMMARY

[0006] The present application aims to solve the problem of precise control of ultra-micro dispensing in micro connection in complex environment, and provides an ultra-micro dispensing device and method based on air pressure-vision double closed loop control, which realizes high precision and high stability of ultra-micro quantitative dispensing.

[0007] The present application adopts the following technical solutions to solve the above problems:

[0008] In one aspect, the present application provides an ultra-micro dispensing device based on air pressure-vision double closed loop control, which comprises an air source, a pressure reducing valve, a Venturi tube, an electronic pressure controller, an electromagnetic valve circuit, an analog-digital conversion module, a calculation module, an air pressure sensor and an operation module. The operation module comprises a dispensing needle tube, a vision module and a dispensing platform. The air source is connected with the pressure reducing valve and the Venturi tube in sequence. The Venturi tube is connected with the electronic pressure controller. The electromagnetic valve circuit is arranged between the pressure reducing valve and the Venturi tube. The electromagnetic valve circuit is connected with the electronic pressure controller and the dispensing needle tube in gas circuit respectively. The air pressure sensor is arranged between the electromagnetic valve circuit and the dispensing needle tube. The calculation module is connected with the electromagnetic valve circuit, the analog-digital conversion module, the air pressure sensor and the vision module circuit respectively. The analog-digital conversion module is connected with the electronic pressure controller circuit.

[0009] Furthermore, the pressure reducing valve includes a negative pressure reducing valve, a high positive pressure channel pressure reducing valve, and a low positive pressure channel pressure reducing valve; the electronic pressure controller includes a negative pressure electronic pressure controller, a high positive pressure electronic pressure controller, and a low positive pressure electronic pressure controller; the air source is connected sequentially to each level of pressure reducing valve; the negative pressure reducing valve is connected to the negative pressure electronic pressure controller via a solenoid valve circuit and a venturi tube; the high positive pressure channel pressure reducing valve is connected to the high positive pressure electronic pressure controller; the low positive pressure channel pressure reducing valve is connected to the low positive pressure electronic pressure controller; and the output terminals of the negative pressure electronic pressure controller, the high positive pressure electronic pressure controller, and the low positive pressure electronic pressure controller are respectively connected to the solenoid valve circuit.

[0010] Furthermore, the three channels encoded by the solenoid valve circuit can divide different air paths into three groups: a low positive pressure channel, a negative pressure channel, and a high positive pressure channel. The low positive pressure channel and the negative pressure channel are used to dynamically adjust the size of the glue spot during the dispensing process, and the high positive pressure channel is used to clear air bubbles in the syringe at the end of the glue solution.

[0011] Furthermore, the calculation module adopts a microcontroller or computer, and the calculation module realizes closed-loop control of air pressure. The calculation module transmits the signal to the digital-to-analog conversion module, and the digital-to-analog conversion module is connected to the electronic pressure controller to perform air pressure control on different paths.

[0012] Furthermore, the vision module transmits signals back to the calculation module, which dynamically adjusts the air pressure based on the dispensing model and the real-time dispensing diameter. The dispensing platform is made of an opaque material, and the vision module is built on the side. Alternatively, the dispensing platform can be transparent, and the vision module can be positioned below it.

[0013] Furthermore, the air pressure sensor collects the pressure inside the dispensing microneedle in real time, and adjusts the size of the dispensing spot in real time through a closed-loop calculation module.

[0014] On the other hand, the present invention provides an ultra-micro dispensing method based on pneumatic-visual dual closed-loop control, which uses the device described in the first aspect to perform ultra-micro dispensing operations. The method specifically includes the following steps:

[0015] S1: Determine the output ΔP of the air pressure controller based on the colloidal flow equation and dispensing morphology model. C The relationship between d and the diameter d of the gel spot: d = f(ΔP) C );

[0016] S2: The diameter d of the adhesive spot is detected in real time using a vision module;

[0017] S3: Based on the closed-loop controller of the computing unit, the air pressure of the dispensing needle is adjusted to achieve precise control of the glue spot.

[0018] Further, before S1, device building and debugging need to be carried out, which specifically includes the following steps:

[0019] S01: Prepare the glue-dipping microneedle and glue, pour the glue into a sterile syringe with a needle, insert the needle of the sterile syringe into the rear end of the glue-dipping microneedle, press the needle tube plunger of the sterile syringe with hand, fill the glue into the glue-dipping microneedle, and complete the glue filling of the glue-dipping microneedle;

[0020] S02: Start the gas source, connect the high-pressure gas to each stage of the pressure reducing valve and the Venturi tube in turn, and after processing, obtain stable negative pressure and positive pressure meeting the rated input gas pressure value of the electronic pressure controller group;

[0021] S03: Connect the electromagnetic valve circuit as required, and successfully divide the gas circuit into three groups of negative pressure path, low positive pressure path and high positive pressure path;

[0022] S04: Select an industrial computer as a calculation module, assemble a digital-to-analog conversion module, a gas pressure sensor, a glue-dipping needle tube, a vision module and a glue-dipping platform according to the device connection requirements;

[0023] S05: Control the electromagnetic valve circuit by the calculation module, switch the gas pressure control device to the negative pressure, low positive pressure and high positive pressure gears respectively, and the calculation module starts the input voltage of each electronic pressure controller from 0 to the highest voltage with a step of 0.001V, and reads the gas pressure value of the corresponding gas pressure sensor at the same time;

[0024] S06: Design a PID controller to realize closed-loop automatic control of gas pressure, and after the gas pressure controller is set, carry out glue-dipping on the glue-dipping platform and calculation.

[0025] Compared with the prior art, the above one or more technical solutions have the following beneficial effects:

[0026] 1. The gas pressure controller in the ultra-micro glue-dipping device and method based on gas pressure-vision double closed loop control has flexible and wide adaptability; the common time-pressure type gas pressure controller, such as the driving mode based on the syringe principle, has problems of limited gas capacity, large disturbance of pressure change curve, etc., and the discrete pressure controller cannot quickly adjust the accurate pressure size; in the device, the high-pressure gas generated by the gas source is processed by the pressure reducing valve and the Venturi tube to obtain stable positive pressure and negative pressure with different amplitudes; the electromagnetic valve divides the gas circuit into three groups, sends coded digital signals to realize gas path switching through the calculation module, and controls each electronic pressure controller through the digital-to-analog conversion module. The negative pressure and low positive pressure path are used for dynamically adjusting the glue spot size, and the high positive pressure path is used for unblocking the needle tube bubble, which can flexibly adapt to various glue-dipping requirements of micro-connection in complex scenes.

[0027] 2, The ultramicro dispensing device and method based on the air pressure-vision double closed loop control have small minimum glue spot size, high precision and strong stability. The existing non-contact dispensing is difficult to realize small dose dispensing task, the screw type and piston type in the contact type dispensing have slow response, mechanical interference and other problems, and the transfer type cannot dynamically adjust the glue liquid quantity; the air pressure-vision double closed loop control method is adopted, the vision unit detects the glue spot diameter in real time, the dynamic identification air pressure-glue spot diameter nonlinear compensation model is combined, and the closed loop controller is used for adjusting the air pressure of the dispensing needle tube, so that the glue spot with a diameter of 9.87 μm can be controlled, the quantitative dispensing of 10 μm, 20 μm, 30 μm and 40 μm can be completed, the error is within 8.3%, and the ultramicro dispensing with high precision and high stability can be guaranteed in a complex environment. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the specific embodiments of the present application, the drawings required in the following specific embodiment description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0029] Figure 1 is the air circuit and circuit diagram of the ultramicro dispensing device based on the air pressure-vision double closed loop control in the embodiment of the present application;

[0030] Figure 2 is the voltage-air pressure collection result of the negative pressure, low positive pressure and high positive pressure gear in the embodiment of the present application;

[0031] Figure 3 is the model identification result of the negative pressure, low positive pressure and high positive pressure gear in the embodiment of the present application;

[0032] Figure 4 is the air pressure set value tracking of the negative pressure, low positive pressure and high positive pressure gear in the embodiment of the present application;

[0033] Figure 5 is the parameter of the planar ultramicro dispensing glue spot morphological approximate spherical cap in the embodiment of the present application;

[0034] Figure 6 is the surface tension analysis of the planar ultramicro dispensing glue spot morphological influence in the embodiment of the present application;

[0035] Figure 7 is the simulation morphological diagram of the planar ultramicro dispensing in the embodiment of the present application;

[0036] Figure 8 is the pressure glue spot diameter relationship and fitting curve in the embodiment of the present application;

[0037] Figure 9This is a stress analysis of the planar dispensing process in an embodiment of the present invention.

[0038] In the diagram, 10-air source; 20-pressure reducing valve; 30-venturi tube; 40-electronic pressure controller; 50-solenoid valve circuit; 60-analog-digital converter module; 70-computing module; 80-pressure sensor; 90-dispensing needle; 91-vision module; 92-dispensing platform. Detailed Implementation

[0039] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0040] like Figure 1 As shown, this invention provides an ultra-micro dispensing device based on pneumatic-visual dual closed-loop control, including an air source 10, a pressure reducing valve 20, a venturi tube 30, an electronic pressure controller 40, a solenoid valve circuit 50, an analog-to-digital converter module 60, a calculation module 70, an air pressure sensor 80, and an operation module. The operation module includes a dispensing needle 90, a vision module 91, and a dispensing platform 93. The air source 10 is connected sequentially to the pressure reducing valve 20 and the venturi tube 30. The venturi tube 30 is connected to the electronic pressure controller 40. The solenoid valve circuit 50 is located between the pressure reducing valve 20 and the venturi tube 30. The air path of the solenoid valve circuit 50 is connected to the electronic pressure controller 40 and the dispensing needle 90. The air pressure sensor 80 is located between the solenoid valve circuit 50 and the dispensing needle 90. The calculation module 70 is connected to the solenoid valve circuit 50 and the analog-to-digital converter module 60. The air pressure sensor 80 and vision module 91 are connected in circuit. The analog-to-digital converter module 60 is connected in circuit with the electronic pressure controller 40. The calculation module 70 uses a microcontroller or computer to realize closed-loop control of air pressure. The calculation module 70 transmits the signal to the analog-to-digital converter module 60, which is electrically connected to the electronic pressure controller 40 to control the air pressure in different paths. The air pressure sensor 80 collects the pressure in the dispensing microneedle 90 in real time and adjusts the size of the dispensing spot in real time through the calculation module 70 in a closed loop. The vision module 91 transmits the signal back to the calculation module 70. The calculation module 70 realizes dynamic adjustment of air pressure according to the dispensing model and the real-time dispensing diameter. If the dispensing platform 92 is made of opaque material, the vision module 91 is built on the side; if the dispensing platform 92 is transparent, the vision module 91 is located below the dispensing platform 92.

[0041] In this embodiment, the pressure reducing valve 20 includes a negative pressure reducing valve, a high positive pressure channel reducing valve and a low positive pressure channel reducing valve, the electronic pressure controller 40 includes a negative pressure electronic pressure controller, a high positive pressure electronic pressure controller and a low positive pressure electronic pressure controller, the gas source 10 is connected with each stage of the pressure reducing valve in turn, the negative pressure reducing valve is connected with the negative pressure electronic pressure controller through the electromagnetic valve circuit 50 and the Venturi tube 30, the high positive pressure channel reducing valve is connected with the high positive pressure electronic pressure controller, the low positive pressure channel reducing valve is connected with the low positive pressure electronic pressure controller, and the output ends of the negative pressure electronic pressure controller, the high positive pressure electronic pressure controller and the low positive pressure electronic pressure controller are connected with the electromagnetic valve circuit 50; three paths coded by the electromagnetic valve circuit 50 can divide different gas paths into three groups, which are a low positive pressure path, a negative pressure path and a high positive pressure path, respectively, the low positive pressure path and the negative pressure path are used for dynamically adjusting the glue spot size in the dispensing process, and the high positive pressure path is used for removing the air bubbles in the needle tube at the end of the glue solution.

[0042] In operation, the gas source 10 serves as a high-pressure gas supply device, and the high-pressure gas generated by the gas source 10 is usually greater than 0.4 MPa and is connected with each stage of the pressure reducing valve 20 and the Venturi tube 30 in turn, so that stable positive pressure and negative pressure with different amplitudes are obtained after processing to meet the rated input voltage of the corresponding electronic pressure controller 40 group; the electromagnetic valve circuit 50 divides the gas path into three groups of negative pressure paths, low positive pressure paths and high positive pressure paths, wherein the negative pressure paths and the low positive pressure paths are used for dynamically adjusting the glue spot size in the dispensing process, and the high positive pressure paths are used for removing the air bubbles in the needle tube at the end of the glue solution; the valve opening degree of the electronic pressure controller 40 is given by the analog-digital conversion module 60, the calculation module 70 realizes the switching of the three gas path paths by sending the encoded digital signal to the electromagnetic valve group; the gas path output end is connected with a three-way joint, one side of which outputs to the air pressure sensor 80 for real-time collection of the pressure of the output end, and the other side of which outputs to the dispensing microneedle 90 to realize air pressure-vision double closed loop quantitative dispensing in combination with the vision module 91 and the dispensing platform 92; the calculation module 70 realizes closed loop control of air pressure, and outputs to the electronic pressure controller 40 after signal transmission to the digital-analog converter 60 to realize air pressure control on different paths; the air pressure value collected by the vision module 91 is fed back to the calculation unit 70, and the calculation unit 70 realizes dynamic adjustment of air pressure according to the dispensing model and the real-time dispensing diameter; the vision module 91 can be built on the side, and if the dispensing platform is of transparent material, an additional vision module 91 can be additionally arranged below the dispensing platform to realize more comprehensive vision detection.

[0043] The application also provides an ultramicro dispensing method based on air pressure-vision double closed loop control, which adopts the above device to perform ultramicro dispensing operation, and the method specifically comprises the following steps:

[0044] S1: determining air pressure controller output ΔP according to the colloid flow equation and the dispensing model C and the relationship between the glue spot diameter d and ΔP, d=f(ΔP C);

[0045] S2: The diameter d of the adhesive spot is detected in real time using a vision module 91;

[0046] S3: Based on the closed-loop controller of the computing unit 70, the air pressure of the dispensing needle is adjusted to achieve precise control of the glue spot.

[0047] In this embodiment, the ultra-micro dispensing method specifically includes the following steps:

[0048] Prepare the dispensing microneedles and adhesive. The dispensing microneedles are made by drawing a glass electrode (Sutter, BF100-78-15) to a 4μm inner diameter at the end using a needle puller (Sutter, P1000). The adhesive has a density of 1.2 g / cm³ and a viscosity of 1 p. Pour the adhesive into a sterile syringe with a needle (sharp, 1ml type). Insert the syringe needle into the rear end of the dispensing needle and press the plunger of the dispensing needle tube by hand to pour the adhesive into the dispensing microneedles, completing the dispensing of the microneedles.

[0049] like Figure 1 As shown, a nitrogen cylinder is used as the gas source 10, which generates high-pressure gas with a pressure of 0.6 MPa upon opening. The high-pressure gas is sequentially connected to various pressure reducing valves 20 and venturi tubes 30. After processing, a stable negative pressure and positive pressure that meet the rated input pressure values ​​of the electronic pressure controller 40 are obtained. The solenoid valve circuit 50 is connected as required, successfully dividing the gas path into three groups: a negative pressure path, a low positive pressure path, and a high positive pressure path. An industrial control computer is selected as the computing module 70. The analog-to-digital converter module 60, the pressure sensor 80, the dispensing needle 90, the vision module 91, and the dispensing platform 92 are assembled according to the device connection requirements, with the vision module 91 built below the dispensing platform 92.

[0050] The calculation module 70 controls the solenoid valve circuit 50 to switch the air pressure control device to negative pressure, low positive pressure, and high positive pressure positions, respectively. The calculation module 70, through the digital-to-analog converter 60, iterates through the input voltage of each electronic pressure controller 40 from 0 to the highest voltage in increments of 0.001V, while simultaneously reading the air pressure values ​​of the corresponding air pressure sensors. The results are as follows: Figure 2 As shown.

[0051] By identifying the circuit models of the air pressure controller, P1 = f N (V1),(0 <V1<V 1max ),P2=f LP (V2),(0 <V2<V 2max ) and P3 = f HP (V3),(0 <V3<V 3max ),like Figure 3 As shown.

[0052] Since the function is monotonically increasing in each channel interval, the inverse function can be obtained and arranged as

[0053]

[0054] PID controller is designed to realize the closed-loop automatic control of air pressure, as shown in Figure 4 , the switching time of pressure in the same gear of negative pressure, low positive pressure or high positive pressure is within 0.1s; The switching time of three gears and the large range pressure change (>100hPa) is within 0.3s.

[0055] The air pressure controller is completed, and the following is the plane dispensing embodiment, as shown in Figure 5 For plane dispensing, the glue spot can be approximated as a spherical cap, and the volume

[0056]

[0057] where V is the volume of the glue spot;

[0058] r is the radius of the glue spot,

[0059] θ is the contact angle of the glue spot with the plane;

[0060] The air pressure value provided by the air pressure control box is

[0061] ΔP C =P C -P AIR (4)

[0062] where P C is the pressure value provided by the air pressure control box;

[0063] P AIR is the atmospheric pressure;

[0064] The dispensing process is shown in Figure 6 In the ultramicro dispensing process, concave interfaces with different radii of curvature are formed on the inside and outside of the dispensing microneedle, respectively. The liquid surface generated by capillary action is quantitatively calculated as an arc, and the radii of curvature of the outside and inside are R outside and R inside , respectively. According to the Young-Laplace equation, it can be known that

[0065]

[0066] where γ is the surface tension coefficient of glue and air, usually 20-50mN / m;

[0067] PM is the pressure size at the glue dispensing microneedle port,

[0068] R inside is the approximate curvature radius of the capillary action generated inside the glue dispensing

[0069] R outside is the approximate curvature radius of the capillary action generated outside the glue dispensing

[0070] As shown in Figure 7 , simulation collaboration verifies that the approximate curvature radius of the capillary action generated outside the glue dispensing under negative pressure is almost unchanged, so the R outside of the outside is approximated as a constant

[0071]

[0072] where P outside is a constant;

[0073] The pressure difference in the needle tube is

[0074]

[0075] For low viscosity glue, assuming its viscosity is a constant value, setting the downward axial direction as the positive direction, according to Poiseuille's law, the flow rate Q satisfies

[0076]

[0077] where r m is the inner diameter of the glue dispensing needle tube end;

[0078] η is the viscosity of the glue;

[0079] ΔP c is the relative value of the pressure in the glue dispensing needle tube and atmospheric pressure;

[0080] k is a constant, related to the length, shape, etc. of the glue dispensing tube;

[0081] Therefore, the change rate of the glue spot radius is

[0082]

[0083] In the pL level glue dispensing, force analysis is performed on the glue, mainly including the suction force F p generated by negative pressure, gravity G, friction force F f between the glue and the tube wall, and the force F c generated by capillary action. When Δ , the force analysis is as shown in Figure 8 (a), when F p , F f , and F c , the glue spot diameter r will continue to increase, and when Δ , the force analysis is as shown in Figure 8(b) As shown, the bead will decrease in size according to the rate shown in equation (9) until it reaches a certain value r min At this point, the force balance will no longer decrease, and the force balance will be maintained; continue to decrease ΔP C As the force along the axis of the dispensing needle increases, the balance is broken, and the bead will further decrease until a new balance is reached, d min The relationship between d C and ΔP is shown in Figure 1. The value of ΔP min required to set the bead size to d can be determined by fitting a curve to the data, and ΔP C Since the function is monotonic, the function can be fitted to the data Figure 9

[0084]

[0085] and satisfies

[0086] d = 2r (11)

[0087] Solving equations (8), (9) and (10) together, we get

[0088]

[0089] First, identify k, and combine the known constants, i.e.

[0090] We get

[0091] To deal with the noise in the data,

[0092] In the plane, M points are selected, and the parameters k are identified by minimizing the sum of the squares of the residuals

[0093] For the control process of the system, the tracking error is defined as

[0094] e = d - d d (17) For ease of derivation, let

[0095] The controlled variable ΔP = u will write equation (12) as

[0096]

[0097] Since d d is a constant, i.e. the desired bead radius is fixed, so Therefore

[0098] In order to make e→0, the control rate u is designed to make

[0099] ​

[0100] wherein k p is a proportional gain, satisfying k p > 0

[0101] Thus, we have

[0102] f(d)(u-g(d)) = -k p e (23)

[0103] We can solve

[0104]

[0105] Substituting the expressions of f(d) and g(d) into the above equation, we have

[0106]

[0107] The stability of the control system is determined by selecting Lyapunov function

[0108]

[0109] The time derivative of V(e) is calculated as

[0110]

[0111] Substituting the control rate into the above equation, we have

[0112]

[0113] Thus, we have According to the Lyapunov stability theorem, the origin e = 0 is asymptotically stable if and only if e = 0.

[0114] Based on the above dispensing method, a dispensing example is implemented on a plane, and the target glue spot diameter is set to 10, 20, 30, and 40 μm, respectively, and 25 glue spots are dispensed for each, and the results are shown in Table 1:

[0115] Table 1: Results of plane dispensing example

[0116] Serial number Target blob diameter (pm) Actual blob diameter (pm) Maximum error 1 10 10.19±0.32(n＝25) 5.1％ 2 20 20.08±0.87(n＝25) 4.8％ 3 30 30.61±1.25(n＝25) 6.2％ 4 40 41.17±2.15(n＝25) 8.3％

[0117] Experiments show that the ultramicro dispensing device and method based on air pressure-vision double closed-loop control proposed in the embodiment can complete quantitative dispensing of 10 μm, 20 μm, 30 μm, and 40 μm, and can control the glue spot with a minimum diameter of 9.87 μm. Through the method, the error is within 8.3%.

[0118] The application is described in detail above by way of examples, but the content is only the preferred embodiment of the application, and cannot be considered as limiting the scope of the application. Any equivalent changes and improvements made according to the scope of the application should still belong to the patent coverage of the application.

Claims

1. An ultramicro dispensing device based on air pressure-visual double closed loop control, characterized in that: The device comprises a gas source (10), a pressure reducing valve (20), a Venturi tube (30), an electronic pressure controller (40), an electromagnetic valve circuit (50), an analog-digital conversion module (60), a calculation module (70), a gas pressure sensor (80), and an operation module, wherein the operation module comprises a dispensing needle tube (90), a visual module (91), and a dispensing platform (92); the gas source (10) is connected with the pressure reducing valve (20) and the Venturi tube (30) in sequence; the Venturi tube (30) is connected with the electronic pressure controller (40); the electromagnetic valve circuit (50) is arranged between the pressure reducing valve (20) and the Venturi tube (30); the electromagnetic valve circuit (50) is connected with the electronic pressure controller (40) and the dispensing needle tube (90) in the gas circuit; the gas pressure sensor (80) is arranged between the electromagnetic valve circuit (50) and the dispensing needle tube (90); the calculation module (70) is connected with the electromagnetic valve circuit (50), the analog-digital conversion module (60), the gas pressure sensor (80), and the visual module (91) in the circuit; and the analog-digital conversion module (60) is connected with the electronic pressure controller (40) in the circuit.

2. The ultra-micro point glue device based on the air pressure-visual double closed loop control according to claim 1, wherein: The pressure reducing valve (20) comprises a negative pressure reducing valve, a high positive pressure channel reducing valve, and a low positive pressure channel reducing valve; the electronic pressure controller (40) comprises a negative pressure electronic pressure controller, a high positive pressure electronic pressure controller, and a low positive pressure electronic pressure controller; the gas source (10) is connected with the pressure reducing valves in sequence; the negative pressure reducing valve is connected with the negative pressure electronic pressure controller through the electromagnetic valve circuit (50) and the Venturi tube (30); the high positive pressure channel reducing valve is connected with the high positive pressure electronic pressure controller; the low positive pressure channel reducing valve is connected with the low positive pressure electronic pressure controller; and the output ends of the negative pressure electronic pressure controller, the high positive pressure electronic pressure controller, and the low positive pressure electronic pressure controller are connected with the electromagnetic valve circuit (50).

3. The ultra-micro point glue device based on the air pressure-visual double closed loop control according to claim 2, characterized in that: The three paths coded by the electromagnetic valve circuit (50) can divide different gas circuits into three groups, namely, a low positive pressure path, a negative pressure path, and a high positive pressure path; the low positive pressure path and the negative pressure path are used for dynamically adjusting the glue spot size in the dispensing process; and the high positive pressure path is used for removing the air bubbles in the needle tube at the end of the glue solution.

4. The ultra-micro point glue device based on the air pressure-visual double closed loop control according to claim 1, wherein: The calculation module (70) adopts a single-chip microcomputer or a computer; the calculation module (70) realizes closed-loop control of the gas pressure; the calculation module (70) transmits signals to the digital-analog conversion module (60); and the digital-analog conversion module (60) is connected with the electronic pressure controller (40) in the circuit to control the gas pressure on different paths.

5. The ultra-micro point glue device based on the air pressure-visual double closed loop control according to claim 1, characterized in that: The visual module (91) transmits signals back to the calculation module (70); the calculation module (70) realizes dynamic adjustment of the gas pressure according to a dispensing model and a real-time dispensing diameter; the dispensing platform (92) is made of opaque material; and the visual module (91) is arranged on the side.

6. The ultra-micro point glue device and method based on the air pressure-visual double closed loop control according to claim 1, characterized in that: The gas pressure sensor (80) collects the pressure in the dispensing needle (90) in real time and adjusts the dispensing glue spot size in real time through the calculation module (70).

7. An ultramicro dispensing method based on air pressure-visual double closed loop control, characterized in that: The device of any one of claims 1-6 is used for ultramicro dispensing operation, and the method specifically comprises the following steps: S1: determining the output ΔP of the air pressure controller according to the colloid flow equation and the dispensing pattern model C and the relationship d = f(ΔP C ) between the air pressure ΔP and the glue spot diameter d S2: Real-time detection of glue spot diameter d is performed by using a vision module (91); S3: The dispensing needle tube air pressure is adjusted based on a closed-loop controller of a calculation unit (70) to realize accurate control of the glue spot.

8. The ultra-micro dispensing method based on the air pressure-visual double closed loop control according to claim 7, characterized in that: Before S1, device construction and debugging are required, and the specific steps include the following: S01: Dispensing microneedles and glue are prepared, the glue is poured into a sterile syringe with a needle, the needle of the sterile syringe is inserted into the rear end of the dispensing microneedle, the needle tube push rod of the sterile syringe is pressed by hand, the glue is filled into the dispensing microneedle, and the glue filling of the dispensing microneedle is completed; S02: A gas source (10) is opened, high-pressure gas is sequentially connected to each stage of pressure reducing valve (20) and venturi tube (30), and after treatment, stable negative pressure and positive pressure meeting the rated input air pressure value of the electronic pressure controller (40) group are obtained; S03: The solenoid valve circuit (50) is connected as required, and the gas circuit is successfully divided into three groups of negative pressure path, low positive pressure path and high positive pressure path; S04: An industrial computer is selected as a calculation module (70), a digital-to-analog conversion module (60), a glue dispensing needle tube (90), a vision module (91) and a dispensing platform (92) are assembled according to the device connection requirements; S05: The solenoid valve circuit (50) is controlled by the calculation module (70), and the air pressure control device is switched to negative pressure, low positive pressure and high positive pressure respectively, the input voltage of each electronic pressure controller (40) is increased from 0 to the highest voltage by the digital-to-analog conversion module (60) with a step of 0.001V, and the air pressure value of the corresponding air pressure sensor is read at the same time; S06: A PID controller is designed to realize closed-loop automatic control of air pressure, after the air pressure controller is set, dispensing is performed on the dispensing platform (92), and calculation is performed.

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