CN111045458A - Novel non-Newtonian fluid micro-coating system and control method - Google Patents
Novel non-Newtonian fluid micro-coating system and control method Download PDFInfo
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- CN111045458A CN111045458A CN201911355979.3A CN201911355979A CN111045458A CN 111045458 A CN111045458 A CN 111045458A CN 201911355979 A CN201911355979 A CN 201911355979A CN 111045458 A CN111045458 A CN 111045458A
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D7/00—Control of flow
- G05D7/06—Control of flow characterised by the use of electric means
- G05D7/0617—Control of flow characterised by the use of electric means specially adapted for fluid materials
- G05D7/0629—Control of flow characterised by the use of electric means specially adapted for fluid materials characterised by the type of regulator means
- G05D7/0635—Control of flow characterised by the use of electric means specially adapted for fluid materials characterised by the type of regulator means by action on throttling means
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
- B05B12/00—Arrangements for controlling delivery; Arrangements for controlling the spray area
- B05B12/08—Arrangements for controlling delivery; Arrangements for controlling the spray area responsive to condition of liquid or other fluent material to be discharged, of ambient medium or of target ; responsive to condition of spray devices or of supply means, e.g. pipes, pumps or their drive means
- B05B12/085—Arrangements for controlling delivery; Arrangements for controlling the spray area responsive to condition of liquid or other fluent material to be discharged, of ambient medium or of target ; responsive to condition of spray devices or of supply means, e.g. pipes, pumps or their drive means responsive to flow or pressure of liquid or other fluent material to be discharged
- B05B12/087—Flow or presssure regulators, i.e. non-electric unitary devices comprising a sensing element, e.g. a piston or a membrane, and a controlling element, e.g. a valve
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D13/00—Control of linear speed; Control of angular speed; Control of acceleration or deceleration, e.g. of a prime mover
- G05D13/62—Control of linear speed; Control of angular speed; Control of acceleration or deceleration, e.g. of a prime mover characterised by the use of electric means, e.g. use of a tachometric dynamo, use of a transducer converting an electric value into a displacement
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D13/00—Control of linear speed; Control of angular speed; Control of acceleration or deceleration, e.g. of a prime mover
- G05D13/66—Governor units providing for co-operation with control dependent upon a variable other than speed
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- Automation & Control Theory (AREA)
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Abstract
The invention discloses a novel non-Newtonian fluid micro-coating system, which comprises a non-Newtonian fluid material loading mechanism, a fluid modeling unit and an intelligent feedback coating control unit; the non-Newtonian fluid material loading mechanism comprises a material storage pressure barrel internally provided with a pressure regulating valve and a thimble valve type nozzle connected through a feeding pipeline, the pressure regulating valve controls the air pressure of the material storage barrel, and fluid can be sprayed out of the nozzle after being pressed into the feeding pipeline; the fluid modeling system is responsible for carrying out process analysis on the nonlinear characteristic of the non-Newtonian fluid and dynamically modeling the micro-coating process; the intelligent feedback coating control system comprises an upper computer, a signal input module, a controller, a controlled object module, a detection unit and an execution module, and is used for performing feedback control on the flow speed of the pipeline fluid based on a non-Newtonian fluid model. The invention solves the problem that the existing micro-coating process does not carry out feedback control according to the nonlinear characteristics of the fluid, and can be applied to various surface coating processes such as paint spraying, fluorescent powder glue coating and the like.
Description
Technical Field
The invention relates to the field of research of automatic spraying, in particular to a novel non-Newtonian fluid micro-coating system and a control method.
Background
The pre-coating process is continuously developed and perfected, and the precision requirement of a user on the coating effect is higher and higher. In the field of automated coating, the requirement for consistent uniformity of workpiece spray coating is of particular importance. Whether the painting process of the automobile industry or the fluorescent powder gluing process of the high-power white light LED industry is adopted, whether the coating effect is consistent or not affects the final aesthetic property, the practicability and the product percent of pass of the product.
Most of spraying materials in the fields of life and production coating are non-Newtonian fluid materials, and the non-Newtonian fluid is a fluid which does not meet the Newtonian viscosity experimental law, namely the shear stress and the shear strain rate of the fluid are not in a linear relation, so that the modeling control of the non-Newtonian fluid is complex; and the micro-coating process of the non-Newtonian fluid is a nonlinear and multivariable coupling system, and the flow rate and the flow velocity of the fluid are influenced by a plurality of factors and cannot keep high uniform uniformity. The traditional control method utilizing manually determined empirical parameters is not high in reliability and low in efficiency. The implementation of fluid modeling and feedback control in micro-coating processes has become an urgent problem to be solved.
Disclosure of Invention
The invention mainly aims to overcome the defects of the prior art and provide a novel non-Newtonian fluid micro-coating system, and the theoretical model of the non-Newtonian fluid micro-coating process can be obtained by firstly carrying out fluid modeling and motion modeling on a non-Newtonian fluid coating material and carrying out pneumatic system modeling on the coating process; and secondly, based on the established model, adjusting the fluid characteristic parameters and the micro-coating process parameters so as to control the flow rate and the flow velocity of the pipeline fluid with high precision. The invention can overcome the problem that the prior micro-coating process does not carry out feedback control according to the nonlinear characteristic of the fluid to a certain extent, effectively improves the consistency of the coating amount and improves the quality and the yield of products.
Another object of the present invention is to provide a novel method of non-Newtonian fluid micro-coating control.
The purpose of the invention is realized by the following technical scheme:
a novel non-Newtonian fluid micro-coating system is characterized by comprising a non-Newtonian fluid material loading mechanism, a fluid modeling unit and an intelligent feedback coating control unit;
the non-Newtonian fluid material loading mechanism comprises a material storage pressure device and a nozzle device, and the material storage pressure device is connected with the nozzle device through a feeding pipeline;
the fluid modeling unit is used for carrying out process analysis on the non-linear characteristic of the non-Newtonian fluid and establishing a non-Newtonian fluid micro-coating model;
the intelligent feedback coating control unit performs flow rate control according to pressure change and flow change, and specifically comprises an upper computer, a signal input module, a controller, a controlled object module, a detection unit and an execution module; the upper computer is used for setting an input expected value of the controller, monitoring the change of the input expected value and further controlling the system to execute a parameter adjusting instruction; the signal input module is used for inputting signals, and the controller is used for receiving and processing the signals to obtain a control strategy; the controlled object module comprises a material storage pressure device and a nozzle device; the detection unit comprises a pressure detection unit for acquiring pressure change of the material storage pressure barrel and a flow detection unit for acquiring flow change of the feeding pipeline; the execution module comprises a storage pressure device and a nozzle device, and the flow rate of the fluid in the non-Newtonian fluid material loading mechanism is subjected to feedback control through the non-Newtonian fluid micro-coating model.
Further, the material storage pressure device comprises a material storage pressure barrel and a first air pressure control unit, and the air pressure of the material storage pressure barrel is controlled by the material storage pressure barrel through the first air pressure control unit; the spray head device comprises a material cylinder, a second air pressure control unit, a third air pressure control unit and a spray nozzle for spraying an outlet, wherein the second air pressure control unit and the third air pressure control unit are used for changing the flow of fluid.
Further, the first air pressure control unit is a pressure regulating valve, the second air pressure control unit is a thimble type valve, and the third air pressure control unit is an atomizing air pressure valve.
Further, the nozzle is a rigid pipeline, and the diameter of the nozzle is smaller than that of the material cylinder.
Furthermore, the fluid modeling unit adopts a power law equation as a constitutive equation of the non-Newtonian fluid, performs process analysis on the non-linear characteristic of the non-Newtonian fluid and establishes a micro-coating model of the non-Newtonian fluid.
Further, the pressure detection unit is a pressure sensor, and the flow detection unit is a flow sensor.
Furthermore, a communication control card is arranged in the upper computer, and the upper computer is in two-way communication with the controller.
The other purpose of the invention is realized by the following technical scheme:
a novel non-Newtonian fluid micro-coating control method is characterized by comprising the following steps:
setting initial parameters and an expected flow rate, wherein the initial parameters comprise a temperature value, an atomization air pressure value, a viscosity value, a feeding air pressure value, a spraying height and a spraying time;
loading the non-Newtonian fluid coating material into a storage barrel, and controlling compressed air to enter the storage barrel through a pressure regulating valve so that the non-Newtonian fluid coating material enters a material cylinder after being pressed into a feeding pipeline;
the fluid modeling unit establishes a non-Newtonian fluid micro-coating model according to the viscosity change of the non-Newtonian fluid and the momentum conservation law of the fluid;
starting coating action, and sending a starting signal by the ejector pin type valve and starting to move;
calculating an error value between the measured flow rate value and a set value, judging whether the error value is greater than a threshold value, if the error value is greater than the threshold value, performing flow rate control by the controller according to the pressure measurement and flow change of the non-Newtonian fluid material loading mechanism, and continuing coating after correcting parameters; otherwise, the parameters are not changed, and the next coating is carried out;
the intelligent feedback coating unit calculates the output signal of the detected actual object and the output signal of the model object to obtain an error feedback signal, the controller receives the given signal and the error feedback signal of the signal input module, and a control strategy is formulated after processing, so that the system is adjusted and controlled.
Further, the non-Newtonian fluid micro-coating model is established, fluid simplified modeling is carried out, and the following assumptions are made:
1) the micro-coating material is a high viscosity fluid, ignoring gravity;
2) the nozzle is a rigid pipeline with a small inner diameter, and the diameter of the nozzle is smaller than that of the material cylinder;
3) the coating fluid is incompressible and the properties do not change;
based on the hypothesis, a relation describing the shear stress and thus the shear rate of the non-Newtonian fluid is established,
wherein, the shear stress is expressed by adopting a power law equation:
wherein, tau is shear stress, K is viscosity coefficient, u is fluid mass point speed, r is distance from mass point to nozzle axis, and shear rate is:
n is a fluid property index;
considering motion along the direction of axis motion, the fluid motion model is simplified as:
wherein, Δ p is the difference between the internal pressure and the external pressure of the fluid in the nozzle, L is the length of the pipeline of the nozzle, and ρ is the density of the fluid;
when formula (1) is substituted for formula (2), the following are provided:
and (3) solving an approximate value of u by using a spectrum method, and adjusting and compensating the pressure at the outlet of the storage barrel so as to control the flow rate of the pipeline.
Further, the intelligent feedback coating unit makes a control strategy, specifically: the controller is respectively connected with the signal input module and the detection unit, receives a given signal of the signal input module and a detection signal of the detection unit, generates a control strategy by programming calculation and feeds a new instruction back to the host computer to be controlled.
Compared with the prior art, the invention has the following advantages and beneficial effects:
the method is based on the fluid characteristics of the non-Newtonian fluid and combines the process motion of the fluid to establish a theoretical model of the coating process, and designs the feedback control system according to the model, so that the uniformity and consistency of the coating effect can be ensured finally, and the method is particularly suitable for the process with high-precision coating requirements.
Drawings
FIG. 1 is a block diagram of a novel non-Newtonian fluid micro-coating system in accordance with the present invention;
FIG. 2 is a flow chart of a novel method for controlling micro-coating of a non-Newtonian fluid in accordance with the present invention;
FIG. 3 is a schematic diagram of process analysis and modeling for non-Newtonian fluid micro-coating in an embodiment of the present invention;
FIG. 4 is a simplified schematic illustration of a nozzle tube according to an embodiment of the present invention;
fig. 5 is a block diagram of an intelligent feedback coating control architecture in the embodiment of the present invention.
FIG. 6 is a flow chart of a novel method for controlling micro-coating of a non-Newtonian fluid in accordance with an embodiment of the present invention.
In the figure: 100-non-newtonian fluid coating material, 101-stock pressure tank, 102-first air pressure control unit, 103-feed pipe, 104-second air pressure control unit, 105-third air pressure control unit, 106-material cylinder, 107-nozzle, 108-pressure detection unit, 109-controller, 110-flow detection unit, 111-signal input module, 112-upper computer, 113-actual object, 114-model object, 115-external interference signal.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but the present invention is not limited thereto.
Example (b):
a novel non-Newtonian fluid micro-coating system is shown in figure 1 and comprises a non-Newtonian fluid material loading mechanism, a fluid modeling unit and an intelligent feedback coating control unit;
the non-Newtonian fluid material loading mechanism comprises a material storage pressure device and a nozzle device, and the material storage pressure device is connected with the nozzle device through a feeding pipeline; the storage pressure device comprises a storage pressure barrel 101 and a first air pressure control unit 102, wherein the storage pressure barrel 101 controls the air pressure of the storage pressure barrel through the first air pressure control unit 102 of the storage pressure barrel; the spray head device comprises a material cylinder 106, a second air pressure control unit 104 and a third air pressure control unit 105 for changing the flow of fluid, and a spray nozzle 107 for spraying an outlet, wherein the spray nozzle 107 is a rigid pipeline, and the diameter of the spray nozzle is smaller than that of the material cylinder; the first pneumatic control unit 102 is a pressure regulating valve, i.e., a pressure valve, the second pneumatic control unit 104 is a thimble type valve, and the third pneumatic control unit 105 is an atomization pneumatic valve. The pressure of the storage tank is controlled by the pressure regulating valve, and the fluid is pressed into the feeding pipeline and then is sprayed out from the nozzle 107.
The fluid modeling unit is responsible for process analysis of the non-linear characteristics of the non-Newtonian fluid and dynamic modeling of the micro-coating process. The power law equation is selected as a constitutive equation of the non-Newtonian fluid, relevant assumptions are made based on the self properties of the fluid, a motion model of the fluid is simplified, and finally an approximate solution of the flow velocity of the pipeline can be obtained through a spectrum method;
the intelligent feedback coating control unit is mainly responsible for carrying out feedback control on the flow speed of the pipeline fluid based on the established non-Newtonian fluid model; the system specifically comprises an upper computer 112, a signal input module 111, a controller 109, a controlled object module, a detection unit and an execution module; the upper computer 112 is internally provided with a communication control card, the upper computer is in bidirectional communication with the controller 109, and the upper computer 112 is used for setting an input expected value of the controller 109, monitoring the change of the input expected value and further controlling a system to execute a parameter adjusting instruction; the signal input module 111 is configured to input a signal, and the controller 109 is configured to receive and process the signal to obtain a control strategy; the controlled object module comprises a material storage pressure device and a nozzle device; the detection unit comprises a pressure detection unit 108 for acquiring pressure change of the material storage pressure barrel and a flow detection unit 110 for acquiring flow change of the feeding pipeline, wherein the pressure detection unit 108 is a pressure sensor, and the flow detection unit 110 is a flow sensor; the execution module comprises a storage pressure device and a nozzle device, and the flow rate of the fluid in the non-Newtonian fluid material loading mechanism is subjected to feedback control through the non-Newtonian fluid micro-coating model.
A novel method for controlling the micro-coating of a non-newtonian fluid, as illustrated in fig. 2, comprising the steps of:
setting initial parameters and an expected flow rate, wherein the initial parameters comprise a temperature value, an atomization air pressure value, a viscosity value, a feeding air pressure value, a spraying height and a spraying time;
loading the non-Newtonian fluid coating material 100 into a storage pressure barrel 101, and controlling compressed air to enter the storage pressure barrel 101 through a pressure regulating valve, so that the non-Newtonian fluid coating material 100 is pressed into a feeding pipeline 103 and then is fed into a feeding cylinder 106;
the fluid modeling unit establishes a non-Newtonian fluid micro-coating model according to the viscosity change of the non-Newtonian fluid and the momentum conservation law of the fluid;
starting coating action, and sending a starting signal by the ejector pin type valve and starting to move;
calculating an error value between the measured flow rate value and a set value, judging whether the error value is greater than a threshold value, if the error value is greater than the threshold value, performing flow rate control by the controller according to the pressure measurement and flow change of the non-Newtonian fluid material loading mechanism, and continuing coating after correcting parameters; otherwise, the parameters are not changed, and the next coating is carried out;
the intelligent feedback coating control unit calculates the output signal of the detected actual object and the output signal of the model object to obtain an error feedback signal, the controller receives the given signal and the error feedback signal of the signal input module, and a control strategy is formulated after processing, so that the system is adjusted and controlled.
The micro-coating process comprises the following steps:
(1) as shown in FIG. 3, a non-Newtonian fluid coating material 100 is loaded into an accumulator 101, and compressed air is controlled by a pressure regulating valve 102 to enter the accumulator, and fluid is forced into a connected feed pipe 103 and then enters a cylinder;
(2) the needle valve 104 sends a signal to the solenoid valve to drive the needle valve piston upward and simultaneously open the atomizing air valve 105, and the fluid 100 is ejected from the nozzle 107 through the cylinder 106.
Further, the relationship between the viscosity, shear stress and shear rate of the non-Newtonian fluid is described by using a more widely used power law equation; and adopts the idea of analytical modeling to establish a fluid motion model,
fig. 4 shows a simplified schematic diagram of a nozzle line according to the present invention, including: the non-Newtonian fluid coating material 100, the material cylinder 106, the nozzle 107, the length L of the nozzle pipeline, the inner diameter d of the nozzle pipeline, the pressure delta p of the fluid at the nozzle and the annular increment dr of the fluid, wherein the factors influencing the coating effect comprise: fluid viscosity characteristics, process parameters of the coating system, such as spray pressure, time, temperature, spray height, nozzle tube inside diameter, etc.
The non-Newtonian fluid micro-coating model is established, fluid simplified modeling is carried out, and the following assumptions are made:
1) the micro-coating material is a high viscosity fluid, ignoring gravity;
2) the nozzle is a rigid pipeline with a small inner diameter, and the diameter of the nozzle is smaller than that of the material cylinder;
3) the coating fluid is incompressible and the properties do not change;
based on the assumption, a relationship describing the shear stress and shear rate of the non-Newtonian fluid is established,
wherein, the shear stress is expressed by adopting a power law equation:
wherein, tau is shear stress, K is viscosity coefficient, u is fluid mass point speed, r is distance from mass point to nozzle axis, and shear rate is:
n is a fluid property index;
considering motion along the direction of axis motion, the fluid motion model is simplified as:
wherein, Δ p is the difference between the internal pressure and the external pressure of the fluid in the nozzle, L is the length of the pipeline of the nozzle, and ρ is the density of the fluid;
when formula (1) is substituted for formula (2), the following are provided:
for the formula (3), the relationship between the nozzle pipeline fluid flow velocity u and the fluid characteristic parameters (K, n, rho), the system module parameters (L, r) and the external control variables (p, t) is described, the approximate value of u is solved by using a spectrum method, and the pipeline flow velocity is controlled by adjusting and compensating the pressure at the outlet of the storage tank. The characteristics of the fluid and the system parameters are generally selected without manual change, so that the flow rate of the pipeline can be controlled by adjusting and compensating the pressure at the outlet of the storage tank.
The structural schematic diagram of the non-Newtonian fluid coating control system of the present invention is shown in FIG. 5:
the pressure sensor 108 is arranged at the feed pipe port of the storage pressure barrel 101 and connected with the controller 109, when the pressure sensor 108 detects the pressure change in the storage pressure barrel, the pressure change can be fed back to the controller 109, and the controller 109 can immediately control the pressure regulating valve 102 to regulate so as to ensure the stability of the feed pressure. Similarly, a flow sensor 110 is disposed at the pipe of the nozzle 107 and connected to the controller 109, and when the flow sensor 110 detects a flow change, the flow can be fed back to the controller 109, and the controller 109 can immediately adjust the opening degree of the needle valve 104 to maintain the consistency of the flow rate of the spraying flow.
Further, the intelligent feedback coating unit makes a control strategy, specifically: a given signal is set through the signal input module 111 or the upper computer 112, the flow sensor 110 detects an output signal of the actual object 113, and calculates with an output signal obtained by calculation of the model object 114 to obtain an error signal, and the error signal is fed back to the input end;
the controller 109 receives the given signal and the error signal, and selects an appropriate control strategy to generate a control command through calculation.
Specifically, the method comprises the following steps: the structural block diagram of the intelligent feedback coating control structure is shown in fig. 6, an internal mold controller with pre-estimated compensation can be selected on the basis of establishing a non-Newtonian fluid micro-coating process model, and the specific control process of the flow or flow rate of a nozzle pipeline comprises the following steps:
(1) the given signal r of the intelligent feedback coating control system can be set through the signal input module 111 or the upper computer 112.
(2) An external disturbance signal 115 acts on the process output, and the flow sensor 110 detects the output signal y of the real object 113 and compares it with the output signal calculated by the model object 114
Obtaining error signal after correlation operation
And finally fed back to the input terminal.
(3) The controller 109 receives an input signal and an error feedback signal of the upper computer 112 or the signal input module 111, and selects a proper control strategy to generate a control command through internal operation.
Alternatively, a pressure control system similar to that of fig. 5 may be designed to maintain the feed pressure constant to better adjust the opening of the needle valve 104 to control the coating flow rate. The controller 109 is connected to the signal input module 111 and the detection unit, respectively, and the controller 109 receives the given signal of the signal input module 111 and the detection signal of the detection unit, and generates a control strategy by the controller 109 through programmed calculation and feeds a new instruction back to the upper computer 112.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.
Claims (10)
1. A novel non-Newtonian fluid micro-coating system is characterized by comprising a non-Newtonian fluid material loading mechanism, a fluid modeling unit and an intelligent feedback coating control unit;
the non-Newtonian fluid material loading mechanism comprises a material storage pressure device and a nozzle device, and the material storage pressure device is connected with the nozzle device through a feeding pipeline;
the fluid modeling unit is used for carrying out process analysis on the non-linear characteristic of the non-Newtonian fluid and establishing a non-Newtonian fluid micro-coating model;
the intelligent feedback coating control unit performs flow rate control according to pressure change and flow change, and specifically comprises an upper computer, a signal input module, a controller, a controlled object module, a detection unit and an execution module; the upper computer is used for setting an input expected value of the controller, monitoring the change of the input expected value and further controlling the system to execute a parameter adjusting instruction; the signal input module is used for inputting signals, and the controller is used for receiving and processing the signals to obtain a control strategy; the controlled object module comprises a material storage pressure device and a nozzle device; the detection unit comprises a pressure detection unit for acquiring pressure change of the material storage pressure barrel and a flow detection unit for acquiring flow change of the feeding pipeline; the execution module comprises a storage pressure device and a nozzle device, and the flow rate of the fluid in the non-Newtonian fluid material loading mechanism is subjected to feedback control through the non-Newtonian fluid micro-coating model.
2. The novel non-Newtonian fluid micro-coating system of claim 1, wherein the storage pressure device comprises a storage pressure barrel and a first air pressure control unit, the storage pressure barrel controls the air pressure of the storage pressure barrel through the first air pressure control unit; the spray head device comprises a material cylinder, a second air pressure control unit, a third air pressure control unit and a spray nozzle for spraying an outlet, wherein the second air pressure control unit and the third air pressure control unit are used for changing the flow of fluid.
3. The system of claim 2, wherein said first pneumatic control unit is a pressure regulating valve, said second pneumatic control unit is a needle valve, and said third pneumatic control unit is an atomizing pneumatic valve.
4. The novel non-Newtonian fluid micro-coating system of claim 2, wherein the nozzle is a rigid pipe with a nozzle diameter smaller than the diameter of the cylinder.
5. The novel non-Newtonian fluid micro-coating system of claim 1, wherein the fluid modeling unit uses a power law equation as a constitutive equation of the non-Newtonian fluid, performs process analysis on non-linear characteristics of the non-Newtonian fluid, and builds a non-Newtonian fluid micro-coating model.
6. The novel non-Newtonian fluid micro-coating system of claim 1, wherein the pressure sensing unit is a pressure sensor and the flow sensing unit is a flow sensor.
7. The novel non-Newtonian fluid micro-coating system of claim 1, wherein a communication control card is built into the upper computer, and the upper computer is in two-way communication with the controller.
8. A novel non-Newtonian fluid micro-coating control method is characterized by comprising the following steps:
setting initial parameters and an expected flow rate, wherein the initial parameters comprise a temperature value, an atomization air pressure value, a viscosity value, a feeding air pressure value, a spraying height and a spraying time;
loading the non-Newtonian fluid coating material into a storage barrel, and controlling compressed air to enter the storage barrel through a pressure regulating valve so that the non-Newtonian fluid coating material enters a material cylinder after being pressed into a feeding pipeline;
the fluid modeling unit establishes a non-Newtonian fluid micro-coating model according to the viscosity change of the non-Newtonian fluid and the momentum conservation law of the fluid;
starting coating action, and sending a starting signal by the ejector pin type valve and starting to move;
calculating an error value between the measured flow rate value and a set value, judging whether the error value is greater than a threshold value, if the error value is greater than the threshold value, performing flow rate control by the controller according to the pressure measurement and flow change of the non-Newtonian fluid material loading mechanism, and continuing coating after correcting parameters; otherwise, the parameters are not changed, and the next coating is carried out;
the intelligent feedback coating unit calculates the output signal of the detected actual object and the output signal of the model object to obtain an error feedback signal, the controller receives the given signal and the error feedback signal of the signal input module, and a control strategy is formulated after processing, so that the system is adjusted and controlled.
9. The novel non-Newtonian fluid micro-coating control method of claim 8, wherein the non-Newtonian fluid micro-coating model is established, and fluid simplified modeling is performed, assuming that:
1) the micro-coating material is a high viscosity fluid, ignoring gravity;
2) the nozzle is a rigid pipeline with a small inner diameter, and the diameter of the nozzle is smaller than that of the material cylinder;
3) the coating fluid is incompressible and the properties do not change;
based on the hypothesis, a relation describing the shear stress and thus the shear rate of the non-Newtonian fluid is established,
wherein, the shear stress is expressed by adopting a power law equation:
wherein, tau is shear stress, K is viscosity coefficient, u is fluid mass point speed, r is distance from mass point to nozzle axis, and shear rate is:
n is a fluid property index;
considering motion along the direction of axis motion, the fluid motion model is simplified as:
wherein, Δ p is the difference between the internal pressure and the external pressure of the fluid in the nozzle, L is the length of the pipeline of the nozzle, and ρ is the density of the fluid;
when formula (1) is substituted for formula (2), the following are provided:
and (3) solving an approximate value of u by using a spectrum method, and adjusting and compensating the pressure at the outlet of the storage barrel so as to control the flow rate of the pipeline.
10. The novel non-Newtonian fluid micro-coating control method of claim 8, wherein the smart feedback coating unit formulates a control strategy, specifically: the controller is respectively connected with the signal input module and the detection unit, receives a given signal of the signal input module and a detection signal of the detection unit, generates a control strategy by programming calculation and feeds a new instruction back to the host computer to be controlled.
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Cited By (3)
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|---|---|---|---|---|
| CN111889251A (en) * | 2020-07-21 | 2020-11-06 | 华中科技大学无锡研究院 | Spraying process parameter control system of high-speed railway automobile body |
| WO2021129100A1 (en) * | 2019-12-25 | 2021-07-01 | 华南理工大学 | Novel non-newtonian fluid micro-coating system and control method |
| CN113533135A (en) * | 2021-07-15 | 2021-10-22 | 湖南工业大学 | Flow control method based on non-Newtonian fluid rheological property test system |
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| WO2021129100A1 (en) | 2021-07-01 |
| CN111045458B (en) | 2021-07-20 |
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