CN117798028A - Surface density control system and method - Google Patents
Surface density control system and method Download PDFInfo
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- CN117798028A CN117798028A CN202311820659.7A CN202311820659A CN117798028A CN 117798028 A CN117798028 A CN 117798028A CN 202311820659 A CN202311820659 A CN 202311820659A CN 117798028 A CN117798028 A CN 117798028A
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- 238000000034 method Methods 0.000 title claims abstract description 21
- 238000001514 detection method Methods 0.000 claims abstract description 49
- 238000000576 coating method Methods 0.000 claims abstract description 46
- 239000011248 coating agent Substances 0.000 claims abstract description 44
- 230000001105 regulatory effect Effects 0.000 claims abstract description 23
- 239000002002 slurry Substances 0.000 claims description 64
- 238000004364 calculation method Methods 0.000 claims description 48
- 239000000758 substrate Substances 0.000 claims description 44
- 238000007581 slurry coating method Methods 0.000 claims description 17
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 14
- 229910052744 lithium Inorganic materials 0.000 claims description 14
- 230000010354 integration Effects 0.000 claims description 13
- 230000014509 gene expression Effects 0.000 claims description 12
- 239000000284 extract Substances 0.000 claims description 4
- 230000008859 change Effects 0.000 abstract description 11
- 230000001808 coupling effect Effects 0.000 abstract description 6
- 238000005192 partition Methods 0.000 description 28
- 230000008878 coupling Effects 0.000 description 10
- 238000010168 coupling process Methods 0.000 description 10
- 238000005859 coupling reaction Methods 0.000 description 10
- 230000007246 mechanism Effects 0.000 description 9
- 238000012544 monitoring process Methods 0.000 description 9
- 230000001276 controlling effect Effects 0.000 description 8
- 238000010586 diagram Methods 0.000 description 8
- 238000013461 design Methods 0.000 description 5
- 238000001035 drying Methods 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 230000008569 process Effects 0.000 description 5
- 238000005070 sampling Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- 239000007788 liquid Substances 0.000 description 4
- 230000009471 action Effects 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 238000004891 communication Methods 0.000 description 2
- 239000000306 component Substances 0.000 description 2
- 238000001739 density measurement Methods 0.000 description 2
- 230000009977 dual effect Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 238000012935 Averaging Methods 0.000 description 1
- 230000002159 abnormal effect Effects 0.000 description 1
- 230000003044 adaptive effect Effects 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 230000003750 conditioning effect Effects 0.000 description 1
- 239000008358 core component Substances 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 238000001125 extrusion Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000004513 sizing Methods 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05C—APPARATUS FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05C11/00—Component parts, details or accessories not specifically provided for in groups B05C1/00 - B05C9/00
- B05C11/10—Storage, supply or control of liquid or other fluent material; Recovery of excess liquid or other fluent material
- B05C11/1002—Means for controlling supply, i.e. flow or pressure, of liquid or other fluent material to the applying apparatus, e.g. valves
- B05C11/1005—Means for controlling supply, i.e. flow or pressure, of liquid or other fluent material to the applying apparatus, e.g. valves responsive to condition of liquid or other fluent material already applied to the surface, e.g. coating thickness, weight or pattern
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Coating Apparatus (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
Abstract
The invention provides an areal density control system and method, comprising a first controller, a screw pump, detection equipment and a plurality of control unit groups, wherein the first controller and the plurality of control unit groups are connected with the detection equipment, and the first controller is connected with the screw pump; each control unit group comprises a second controller and a die head regulating piece; the detection equipment and the die head adjusting piece are connected with a second controller; each die adjuster acts on a slot of the coating die; the screw pump is connected with the coating die head; in the mode, the screw pump is in closed-loop control, the first controller takes the surface density average value as feedback input, the output result can integrally and uniformly change the surface density of each subarea, so that the surface density average value can follow a given value, each second controller only takes the surface density of the corresponding subarea as feedback input, the output result can change the surface density of the corresponding subarea, the influence of pump adjustment on die head adjustment is reduced, and the coupling effect between a die head adjusting piece and the screw pump is reduced to a certain extent.
Description
Technical Field
The invention relates to the technical field of lithium batteries, in particular to an area density control system and method.
Background
In the lithium battery pole piece coating process, the control of the pole piece surface density depends on the dry film surface density value, is limited by the time required for drying the slurry, and a control system designed by taking the dry film surface density value as feedback is necessarily a large hysteresis system, thus the design of a control scheme is very challenging. In the existing dry film surface density control scheme, the measurement feedback value of the dry film surface density takes the average value of the surface densities of corresponding subareas monitored for a plurality of times, the controller adopts a PID controller with parameter self-setting, the time lag of the system is further increased, in addition, two adjusting mechanisms of a die head adjusting block and a screw pump are simultaneously arranged in the system, the screw pump is in open loop control, the given value of the die head adjusting block is the average value of the surface densities of all subareas, and larger coupling exists between the two adjusting mechanisms, so that the surface densities of all areas are difficult to follow a given value.
Disclosure of Invention
The invention aims to provide an area density control system and an area density control method, which can reduce the coupling effect between a die head adjusting piece and a screw pump to a certain extent by reasonably distributing control logics of the die head adjusting piece and the screw pump.
The invention provides an area density control system, which comprises: the device comprises a first controller, a screw pump, detection equipment and a plurality of control unit groups, wherein the first controller and the plurality of control unit groups are connected with the detection equipment, and the first controller is connected with the screw pump; each control unit group comprises a second controller and a die head regulating piece; the detection equipment and the die head adjusting piece are connected with a second controller; each die adjuster acts on a slot of the coating die; the screw pump is connected with the coating die head;
The first controller is used for outputting a first instruction according to the received first slurry coating instruction;
the screw pump is used for extracting the slurry from the slurry tank according to a first instruction and conveying the slurry into a slit of the coating die head;
each second controller is used for outputting a second instruction according to the received second slurry coating instruction;
each die head adjusting piece is used for adjusting the distance between the die head adjusting piece and the bottom of the slit according to the second instruction so as to adjust the slurry flow of the subarea corresponding to the die head adjusting piece in the width direction of the lithium battery level substrate;
each second controller is further used for acquiring the surface density of the corresponding subarea detected by the detection equipment, outputting an adjusted second instruction according to the surface density of the corresponding subarea and a preset first given value, and adjusting the surface density of the corresponding subarea according to the adjusted second instruction;
the first controller is used for acquiring the surface density of each sub-area detected by the detection equipment, calculating the surface density average value according to the surface density of each sub-area, and outputting an adjusted first instruction based on the surface density average value and a preset second given value so as to adjust the surface density of each sub-area according to the adjusted first instruction.
Further, the detection device is a plurality of detection devices; each detection device is respectively connected with the first controller and the corresponding second controller;
each detection device is used for detecting the surface density of the corresponding subarea and sending the surface density to the first controller and the corresponding second controller.
Further, each die head adjusting member comprises a die head adjusting block and a motor which are connected with each other; the motor is connected with the second controller.
Further, each second controller comprises a first judging module and a first calculating module;
the first judging module is used for judging whether the surface density of the corresponding subarea reaches a first given value or not; if the first set value is not reached, generating a first surface density difference value according to the surface density and the first set value; transmitting the first area density difference value to a corresponding first calculation module;
the first calculation module is used for calculating a first area density difference value according to a built-in first preset algorithm to obtain a first calculation result, adjusting the rotating speed of a corresponding motor according to the first calculation result, and driving the die head adjusting block to move through the motor so as to adjust the distance between the die head adjusting block and the bottom of the slit.
Further, the screw pump comprises a frequency converter, and the first controller comprises a second judging module, a second calculating module and a third calculating module;
The second calculation module is used for obtaining the surface density of each sub-area, calculating the surface density average value according to the surface density of each sub-area, and sending the surface density average value to the second judgment module;
the second judging module is used for judging whether the section density average value reaches a second given value; if the second set value is not reached, generating a second surface density difference value according to the surface density average value and the second set value; and sending the second areal density difference to a third computing module;
the third calculation module is used for calculating the second surface density difference value according to a built-in second preset algorithm to obtain a second calculation result, and adjusting the frequency of the frequency converter according to the second calculation result so as to adjust the slurry flow extracted from the slurry tank by the screw pump.
Further, the first preset algorithm comprises a predictive PI algorithm; the second preset algorithm includes a combined integration algorithm.
Further, the predictive PI algorithm includes a first adjustable parameter; the value of the first adjustable parameter is half of the lag time; the lag time is a lag time constant in a first-order inertial link expression corresponding to the corresponding die head regulating block.
Further, the combined integration algorithm includes a second adjustable parameter; the difference between the value of the second adjustable parameter and the value of the first adjustable parameter satisfies a preset threshold range.
Further, the control system also comprises an upper computer; the upper computer is respectively connected with the first controller and each second controller and is used for sending the first given value to the first controller and sending the second given value to each second controller.
The invention provides an area density control method which is applied to any one of the area density control systems; the method comprises the following steps:
the first controller outputs a first instruction according to the received first slurry coating instruction;
the screw pump extracts the slurry from the slurry tank according to a first instruction and conveys the slurry into a slit of the coating die head;
each second controller outputs a second instruction according to the received second slurry coating instruction;
each die head adjusting piece adjusts the distance between the die head adjusting piece and the bottom of the slit according to the second instruction so as to adjust the slurry flow of the subarea corresponding to the die head adjusting piece in the width direction of the lithium battery level substrate;
each second controller obtains the surface density of the corresponding subarea detected by the detection equipment, and outputs an adjusted second instruction according to the surface density of the corresponding subarea and a preset first given value so as to adjust the surface density of the corresponding subarea according to the adjusted second instruction;
The first controller obtains the surface density of each sub-area detected by the detection device, calculates the surface density average value according to the surface density of each sub-area, and outputs an adjusted first instruction based on the surface density average value and a preset second given value so as to adjust the surface density of each sub-area according to the adjusted first instruction.
The invention provides an areal density control system and method, comprising a first controller, a screw pump, detection equipment and a plurality of control unit groups, wherein the first controller and the plurality of control unit groups are connected with the detection equipment, and the first controller is connected with the screw pump; each control unit group comprises a second controller and a die head regulating piece; the detection equipment and the die head adjusting piece are connected with a second controller; each die adjuster acts on a slot of the coating die; the screw pump is connected with the coating die head. In the mode, the screw pump is in closed-loop control, the first controller takes the surface density average value as feedback input, the output result can integrally and uniformly change the surface density of each subarea, so that the surface density average value can follow a given value, each second controller only takes the surface density of the corresponding subarea as feedback input, the output result can change the surface density of the corresponding subarea, so that the surface density of the corresponding subarea can follow the given value, the influence of pump adjustment on die head adjustment is reduced, and the coupling effect between a die head adjusting piece and the screw pump is reduced to a certain extent.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of an areal density control loop according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of an areal density control system according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of another exemplary areal density control loop according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of another system for controlling areal density according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of another system for controlling areal density according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of another system for controlling areal density according to an embodiment of the present invention;
FIG. 7 is a schematic diagram of another system for controlling areal density according to an embodiment of the present invention;
fig. 8 is a flowchart of an areal density control method according to an embodiment of the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In the lithium battery pole piece coating process, the coating function is to uniformly coat positive and negative pole sizing agent on a base material, and then the positive and negative pole coating is formed after drying by an oven. Correspondingly, the areal density is also divided into the wet film areal density before drying and the dry film areal density after drying. In the event that the wet film areal density is not measurable or the measurement is not accurate, the control of the pole piece areal density will depend on the dry film areal density value. In the existing dry film surface density control scheme, the feedback value adjusted by each coating die head takes the average value of the monitoring of the corresponding partition surface density for several times (i.e. the partition surface density value obtained by several sampling moments is summed and divided by the sampling moment to obtain the average value), and the average value of the monitoring of the partition surface density for several times (i.e. the average value of the monitoring of the partition surface density for several times is summed and divided by the partition quantity to obtain the average value), the controller adopts a PID controller with self-setting parameters, and the pump is designed in an open loop. Specifically, referring to a schematic diagram of an areal density control loop shown in fig. 1, the pump speed is generally controlled by directly setting a pump inverter according to accumulated working experience by a human operator; taking the average value of monitoring the area density of the corresponding partition for several times to refer to the average value of the area density of the partition 1 in the width direction of the substrate, the average value of the area density of the partition 2 in the width direction of the substrate, … … and the average value of the area density of the partition N in the width direction of the substrate in the figure 1; taking the average of the average values of the monitoring of the area density of each partition several times to refer to the average value of the area density in fig. 1; the average value of the surface density of each partition is used as the feedback input of the regulating block controller of the corresponding partition, the average value of the surface density average value is used as the set value of all regulating blocks, the time required for drying the slurry is limited, and the control system designed by taking the dry film surface density value as the feedback in the prior art is necessarily a large-lag system, so that a great challenge is caused to the design of a control scheme. The self-tuning PID controller adopted by the existing control scheme is limited by the self-tuning PID controller (the control performance of a controlled object with large time lag is reduced) and the design of a closed loop of the whole system is defective (for example, the average value of monitoring the area density of a corresponding partition for several times is taken as the feedback value corresponding to the adjustment of a coating die head, so that the time lag of the system is further emphasized), and the adverse effect caused by the large time lag is difficult to be relieved (the stability of the area density and the quality of a battery pole piece are reduced, and the difficulty of the area density control is increased). In addition, two adjusting mechanisms, namely a die head adjusting block and a screw pump, exist in the system at the same time, and coupling exists between the two adjusting mechanisms, so that the output of the system is difficult to follow a given value, namely a given value of each die head adjusting block is an average value of the surface density average value, the value is influenced by the pump to be time-varying, so that slight change of the pump can greatly influence the surface density, the pump is in open-loop control, the anti-interference capability is poor, if manual adjustment is not timely, abnormal values and the like occur in the surface density, the adjustment difficulty of the die head adjusting block is increased, and the surface density is difficult to follow a set point.
Based on the above, the invention provides an areal density control system and method, which can relieve the negative influence of large hysteresis attached to dry film areal density measurement; the die head adjusting block and the control logic of the screw pump are reasonably distributed, and proper parameter settings are adopted, so that the die head adjusting block has stronger anti-interference capability and robustness, and the coupling effect between the die head adjusting block and the screw pump is reduced to a certain extent.
For ease of understanding the present embodiment, a detailed description of an areal density control system disclosed in embodiments of the invention will be provided.
The present invention provides an areal density control system, as shown in fig. 2, the control system includes: a first controller 1, a screw pump 2, a detecting device 5, and a plurality of control unit groups; the first controller 1 and the plurality of control unit groups are connected with the detection equipment 5, and the first controller 1 is connected with the screw pump 2; each control unit group comprises a second controller 3 and a die head regulator 4; the detection device 5 and the die head adjusting piece 4 are connected with the second controller 3; each die regulator 4 acts on the slit of the coating die 6; the screw pump 2 is connected with the coating die head 6;
the first controller 1 is configured to output a first instruction according to the received first slurry coating instruction;
The screw pump 2 is used for extracting slurry from the slurry tank 7 according to a first instruction and conveying the slurry into a slit of the coating die 6;
each second controller 3 is configured to output a second instruction according to the received second slurry coating instruction;
each die head regulating block piece 4 is used for regulating the distance between the die head regulating piece 4 and the bottom of the slit according to the second instruction so as to regulate the slurry flow of the subarea corresponding to the die head regulating piece 4 in the width direction of the lithium battery level substrate;
each second controller 3 is further configured to obtain the surface density of the corresponding sub-region detected by the detection device 5, and output an adjusted second instruction according to the surface density of the corresponding sub-region and a preset first given value, so as to adjust the surface density of the corresponding sub-region according to the adjusted second instruction;
the first controller 1 is configured to obtain the surface density of each sub-area detected by the detecting device 5, calculate an average value of the surface densities according to the surface density of each sub-area, and output an adjusted first instruction based on the average value of the surface densities and a preset second given value, so as to adjust the surface density of each sub-area according to the adjusted first instruction.
The first controller 1 may be understood as a controller of the screw pump 2, and the second controller 3 may be understood as a controller of the die adjusting member 4.
The screw pump 2 can be understood as a rotary pump which conveys or pressurizes liquid by means of the change and movement of the volume of the meshing space formed by the pump body and the screw, and when the driving screw rotates, the driven screw meshed with the driving screw is driven to rotate together, the volume of the meshing space of the screw at one end of the suction cavity is gradually increased, and the pressure is reduced. Liquid enters the engagement space volume under the action of a pressure differential. When the volume is maximized to form a sealed chamber, the liquid is continuously moved axially within each sealed chamber until it is discharged from one end of the chamber. At this time, the volume of the screw engagement space at one end of the discharge chamber is gradually reduced, so that the liquid is discharged; screw pumps are classified into single screw pumps, double, triple and five screw pumps, etc. according to the number of screws.
In practice, the lithium battery grade sheet generally includes a grade sheet substrate and grade sheet slurry coated on both side surfaces of the substrate, the positive and negative electrode sheets of the lithium battery are mostly coated by extrusion, the coating die is an important component of the coating machine, and the slurry is extruded and sprayed along a slit (corresponding to the slit) of the coating die under a certain pressure to be coated on the substrate.
Specifically, the coater, the coating die 6 and the die regulator 4 belong to a subordinate relationship, wherein the coating die 6 is an essential important core component of the coater; the die head adjusting block 4 is a component on the coating die head 6, and specifically, the die head adjusting block can act on a slit of the coating die head 6, which is equivalent to adding a certain obstruction to the slit through the die head adjusting block 4, when the die head adjusting block is actually realized, the coating die head 6 can move up and down relative to the slit, and the thickness of coating (i.e. the area density of the stage sheet) can be finely adjusted by controlling the distance between the die head adjusting block 4 and the bottom of the slit (i.e. the vertical distance between the lower surface of the die head adjusting block 4 and the bottom of the slit), so that the thickness of coating meets the process requirement.
Specifically, the plurality of die head adjusting members 4 on the slit are independent of each other, which means that the plurality of die head adjusting members 4 independent of each other are formed transversely on the slit and are used for adjusting the flow rate of the slurry at different positions in the transverse direction (which means that each die head adjusting member corresponds to the transverse position of the slit, namely, corresponds to the plurality of subareas in the width direction of the lithium battery level substrate), so as to adjust the area density of the corresponding subareas; wherein, each die head regulating element and each transverse position have a one-to-one correspondence, and each transverse position and each sub-area have a one-to-one correspondence, so that each die head regulating element and each sub-area have a one-to-one correspondence.
The detection device 4 may be separately provided, or may be provided on a coater, for detecting the surface density of each sub-region on the substrate after the slurry is applied, feeding back the surface density of each sub-region to the first controller 1, and feeding back the surface density of each sub-region to the second controller 3 connected to the die regulator 4 corresponding to the sub-region.
The screw pump 2 described above may be in communication with the coating die 6 through a conduit for delivering the slurry through the conduit to the die cavity of the coating die 6 and further to a slot in communication with the die cavity.
In actual implementation, a digitized control algorithm (may be a combined integration algorithm) is generally integrated in the first controller 1 and is used for controlling the screw pump 2, so as to control the average value of the surface densities in the substrate travelling direction (i.e., parallel to the substrate advancing direction) (i.e., the value obtained by summing the surface densities of the sub-areas in the width direction of the substrate and then averaging the sum); the second controller 3 is generally integrated with a digital control algorithm (which may be an IP algorithm) for controlling the die adjusting block 4, so as to control the areal density of the corresponding subarea in the width direction of the substrate (i.e., perpendicular to the advancing direction of the substrate).
Each of the second controllers 3 may correspond to one die adjusting member 4, one substrate to be sprayed having a surface density in the width direction of the substrate (i.e., one sub-region in the width direction of the lithium battery level substrate), and one surface density of the surface density region (i.e., the surface density of the corresponding sub-region), wherein the surface density of each sub-region is also referred to as the surface density of each surface density region in the width direction of the substrate; assuming that 5 die-head adjusting blocks are provided, the area densities of the 5 second controllers, the 5 substrate width-direction sub-areas, and the 5 substrate width-direction sub-areas correspond.
In a specific implementation process, when the coating work starts to be executed, the upper computer may send a first slurry coating instruction to the first controller 1 and send the first slurry coating instruction to the second controller 3, where the first slurry coating instruction may carry a second specific surface density standard value (corresponding to the preset second specific value) preset according to an actual situation, and the second slurry coating instruction may carry a first specific surface density standard value (corresponding to the preset first specific value, and the preset first specific value and the preset second specific value are generally the same).
After receiving the given second set value, the first controller 1 can obtain the total slurry flow corresponding to the given total surface density value (that is, the product result of the second surface density standard value and the number of die head regulating members) through calculation, so as to output a first instruction carrying the total slurry flow to the screw pump 2, control the screw pump 2 to adjust the rotating speed, so that the screw pump 2 extracts slurry corresponding to the total slurry flow from the slurry tank 7 and conveys the slurry to the slit of the coating die head 6, and after the total slurry flow in the slit is regulated by the die head regulating members 4, the slurry can be output to each subarea of the base material through the slit, and coating of each subarea is completed, so that the surface density (that is, the thickness of slurry coating) of each subarea is obtained.
After the second controller 3 receives the first given value, it may obtain the distance corresponding to the first given value (the surface density of each surface density partition is required to be uniform and consistent with the first given value in actual implementation) through calculation, output the second instruction carrying the distance to the corresponding die regulator 4, control the height of the corresponding die regulator 4, so that the corresponding die regulator 4 adjusts the slurry flow rate output to the sub-region corresponding to the die regulator 4 in the width direction of the lithium battery level substrate through the slit, thereby adjusting the surface density of the sub-region to meet the first given value.
However, in actual implementation, there is a possibility that the slurry flow rate outputted to the subregion through the slit does not reach or exceed the slurry flow rate corresponding to the first given value due to various disturbances, so that the surface density of the corresponding subregion does not satisfy the first given value, and therefore, the second controller 3 corresponding to the subregion that does not satisfy the first given value may be determined first, the corresponding die head regulator 4 may be controlled by the second controller 3 through the difference between the surface density of the subregion and the first given value obtained in advance, and further, the surface density of the corresponding subregion may be adjusted, and specifically, if the surface density of the corresponding subregion does not satisfy the first given value, the control of the corresponding die head regulator 4 may be repeatedly performed until the surface density of the corresponding subregion satisfies the first given value.
Specifically, after the above-mentioned detection device 5 feeds back the detected surface density of each sub-area to the second controller 3 connected to the die head adjusting member 4 corresponding to the sub-area, the second controller 3 may calculate a difference value between the surface density of the corresponding sub-area and the first given value, and a distance adjustment amount corresponding to the difference value, output an adjusted second instruction carrying the distance adjustment amount to the corresponding die head adjusting member 4, and control the die head adjusting member 4 to adjust the height, so as to adjust the slurry flow rate conveyed to the corresponding sub-area through the slit corresponding to the lateral position, and further adjust the surface density of the corresponding sub-area.
However, in actual implementation, there is a possibility that the total slurry sucked from the slurry tank does not satisfy the actual requirement, so that even if the repeated execution is performed a plurality of times, the surface density of the corresponding subregion cannot be made to satisfy the first given value, and therefore, the first controller 1 and the second controller 3 may be combined to jointly control the surface densities of the plurality of subregions, so that the surface density of the corresponding subregion satisfies the first given value (i.e., the surface density of the corresponding subregion is the same as the first given value), and at the same time, the surface density average value satisfies the second given value (i.e., the surface density of each subregion satisfies the first given value); specifically, an average value of the surface density (i.e., the surface density in the direction of the substrate running) may be obtained, and then the screw pump 2 may be controlled according to the difference between the average value of the surface density and a second given value obtained in advance, thereby adjusting the surface density of each sub-region.
Specifically, after the above-mentioned detection device 5 feeds all detected surface densities of the sub-areas back to the first controller 1, the first controller 1 may calculate an average value of the surface densities, a difference value between the average value of the surface densities and a preset second given value, and a slurry flow adjustment amount corresponding to the difference value, output an adjusted first instruction carrying the slurry flow adjustment amount to the screw pump 2, control the screw pump 2 to adjust the rotation speed, so as to adjust the slurry flow in the slit of the screw pump 2 delivered to the coating die 6, and further adjust the surface densities of all the sub-areas (corresponding to the adjustment of the average value of the surface densities).
For a better understanding of the above embodiments, reference may be made to a schematic illustration of an areal density control loop, as shown in fig. 3, which includes multiple sets of controlled objects, an automatic control mechanism; wherein the automatic control mechanism mainly comprises a die head controller (corresponding to each second controller) and a pump controller (corresponding to the first controller) of each die head regulating block; as shown in fig. 3, the controlled object mainly includes the area density of the substrate width direction partition 1, the area density of the substrate width direction partition 2, …, and the area density of the substrate width direction area density partition N; the automatic control mechanism described above includes a die controller 1 (i.e., a controller of the die adjusting block 1), a die controller 2, …, a die controller N, and a pump controller (corresponding to the second controller).
Logically, both the areal density of the substrate in the widthwise zones and the areal density of the substrate in the direction of travel (parallel to the direction of travel of the substrate) (i.e., the average areal density of the substrate in the widthwise direction, corresponding to the average areal density) should be maintained at the same set point, so that the pump controller and each die controller have a given signal input (corresponding to the first set point, the second set point). The areal density of each substrate widthwise zone is fed back only to the corresponding die controller, e.g., die controller 1 negative feedback signals are derived only from the areal density of substrate widthwise zone 1. The average surface density in the widthwise direction of the substrate reflects the surface density in the direction of the substrate running at that time and is fed back to the pump controller.
Each die head controller and the corresponding substrate width direction partition area density form each small closed-loop control loop, and each small closed-loop control loop forms a large inner loop control loop together and is used as a control object of the pump controller, namely the pump controller is positioned in the outer loop control loop. Therefore, the whole control system consists of double closed loops, and compared with a single loop system of the traditional control scheme, the added outer loop control loop can play a role in controlling the interference advance, and the control object of each pump controller comprises the control object of the die head controller, so that the mutual influence between the inner loop controller and the outer loop controller is reduced, the anti-interference performance of the system is improved, and the coupling of the system is reduced; the pump controller can calculate the surface density average value according to the average surface density in the width direction of the base material, control the partition surface density in the width direction of each base material in real time, integrally and uniformly change the surface density of each partition, the fluctuation of the partition surface density is smaller, and the control difficulty of the die head controller is reduced, so that the influence between the die head controller and the pump controller is reduced, the coupling is reduced, the time interval of manual open-loop control is longer, the fluctuation of the partition surface density caused by untimely control is larger, the control difficulty of the die head controller is increased, and serious coupling exists. In addition, the conventional dual closed-loop control circuit generally comprises a main controlled object and a secondary controlled object, and the dual closed-loop control circuit in the embodiment only comprises one substantially controlled object (the area density of the substrate width direction partition corresponding to each die adjusting block, namely the area density of each self-subarea), so that the system structure is simplified.
Further, compared with the conventional control scheme, in this embodiment, the given value of the die controller is not an average value of the monitoring of each partition area density for several times, the average value of the monitoring of each partition area density for several times does not need to be fed back to the die controller, and the feedback of the die controller only corresponds to the partition area density.
Further, compared with the conventional control scheme, in this embodiment, the value fed back to the die head controller is the detected area density of the corresponding partition at the current sampling time, and is not the average value of monitoring the area density of the corresponding partition for several times, so that the time lag of the system is not aggravated.
The surface density control system provided by the embodiment comprises a first controller, a screw pump, detection equipment and a plurality of control unit groups, wherein the first controller and the plurality of control unit groups are connected with the detection equipment, and the first controller is connected with the screw pump; each control unit group comprises a second controller and a die head regulating piece; the detection equipment and the die head adjusting piece are connected with a second controller; each die adjuster acts on a slot of the coating die; the screw pump is connected with the coating die head. In the mode, the screw pump is in closed-loop control, the first controller takes the surface density average value as feedback input, the output result can integrally and uniformly change the surface density of each subarea, so that the surface density average value can follow a given value, each second controller only takes the surface density of the corresponding subarea as feedback input, the output result can change the surface density of the corresponding subarea, so that the surface density of the corresponding subarea can follow the given value, the influence of pump adjustment on die head adjustment is reduced, and the coupling effect between a die head adjusting piece and the screw pump is reduced to a certain extent.
On the basis of the above-mentioned surface density control system, the embodiment of the present invention also provides another surface density control system, as shown in fig. 4, where the control system includes a plurality of detection devices 5; each detection device 5 is also connected to the first controller 1 and the corresponding second controller 3, respectively.
Each detection device 5 is adapted to detect the areal density of the corresponding sub-area and to send this areal density to the first controller 1 and the corresponding second controller 3.
The above-described detection device 5 (also referred to as peripheral device) can be understood as a detection sensor for detecting and feeding back the areal density.
In actual implementation, each detection sensor can be in one-to-one correspondence with each sub-area, can be independently arranged, can also be arranged on a coating machine and is used for detecting the surface density of the corresponding sub-area on the substrate after the slurry is coated, feeding back the surface density of each corresponding sub-area to the first controller 1 and feeding back the surface density of the corresponding sub-area to the second controller 3 corresponding to the sub-area.
On the basis of the above-described areal density control system, the embodiment of the present invention also provides another areal density control system, as shown in fig. 5, in which each die adjustment member 4 includes a die adjustment block 41 and a motor 42 connected to each other; the motor 42 is connected to the corresponding second controller 3.
Each second controller 3 comprises a first judging module 31 and a first calculating module 32;
the first judging module 31 is configured to judge whether the area density of the corresponding sub-area reaches a first given value; if the first set value is not reached, generating a first surface density difference value according to the surface density of the corresponding subarea and the first set value; and sends the first areal density difference to the corresponding first calculation module 32; the first calculating module 32 is configured to calculate the first area density difference according to a built-in first preset algorithm, obtain a first calculation result, and adjust a rotation speed of a corresponding motor 42 according to the first calculation result, and drive the die head adjusting block 41 to move (generally move up and down) through the motor 42, so as to adjust a distance between the die head adjusting block 41 and the bottom of the slit.
The motor 42 is connected to the die head adjusting block 41, the die head adjusting block 41 acts on the slit of the coating die head 6, the first preset algorithm is a predictive PI algorithm, in actual implementation, a digitized control algorithm, that is, a predictive PI algorithm, may be integrated in each second controller 3, and in addition, each second controller 3 may further include a first judging module 31 and a first calculating module 32 that are communicatively connected; when the second controller 3 receives the surface density of the corresponding sub-region fed back by the detection sensor, the first judging module 31 can be utilized to judge whether the surface density is consistent with the first given value, if not, the difference value between the surface density and the first given value can be calculated, and the first surface density difference value is obtained; and sends the first areal density difference to the corresponding first calculation module 32; the first calculation module 32 calculates the first area density difference according to the built-in predictive PI algorithm, to obtain the distance between the corresponding die head adjusting block 41 and the bottom of the slit (corresponding to the height position of the corresponding die head adjusting block 41 in the coating die head 6), that is, the first calculation result, and according to the first calculation result, the rotation speed of the motor 42 connected with the corresponding die head adjusting block 41 can be adjusted, so as to drive the die head adjusting block 41 to move to the position corresponding to the first calculation result.
For example, if the difference between the area density of the subarea and the first given value is minus 2, a first calculation result corresponding to the difference between the first ground densities is 2 may be calculated, so as to control the rotation speed of the motor 42 according to the first calculation result, and if the original area density of the subarea is smaller than the first given value, the distance needs to be increased, so that the slurry flow output from the corresponding transverse position in the slot becomes larger, and further, the area density of the corresponding subarea becomes larger, so as to reach the first given value.
In particular, when facing a large time lag object, the predictive PI algorithm performs calculation by collecting and processing system data of a period of time, and compared with a PID controller in a traditional control scheme, the predictive PI algorithm can well relieve the large lag negative effect caused by dry film surface density measurement.
Specifically, the discrete input-output expression of the predictive PI algorithm of the single-input single-output system is:
wherein,respectively representing the proportionality coefficient and the time constant of the controlled object; t is t 1 Indicating the lag time of the controlled object, +.>Respectively representing the output (corresponding to the first calculation result) and the deviation input (corresponding to the first area density difference value) of the controller at the kth time and +.>Is the sampling time (per T s Time, obtain one input/output value). />The adjustable parameter (namely the first adjustable parameter) of the second controller needs to be set according to actual conditions, and the larger the value of the adjustable parameter is, the stronger the system robustness is. />The term has the characteristics of a PI controller, and +.>The term can be understood as the output of the first controller at a certain instant k being based on the interval k-t 1 The historical output impact of the first controller in k). Therefore, the hysteresis of the system is correspondingly compensated, and the algorithm is applied to the inner loop controller (namely the die head controller), so that the large hysteresis of the system can be effectively relieved.
The process of spraying the viscous slurry from the slit to the substrate can be approximated to a first-order inertia link by the principle analysis, and the actual proportionality coefficient of the link (namely K in the expression is obtained by the step test 1 ) And a time constant (i.e., T in the above expression) 1 ). It should be noted that each coating die generally comprises a plurality of die adjusting blocks, and the first-order inertial link expression of the area density of the subarea of each die adjusting block in the width direction of the substrate is different under the influence of the die structure. But howeverThe lag time constant of each expression (i.e., t in the above expression 1 ) It should be equivalent because the lag time is determined primarily by the time scale of the slurry from being sprayed to the dry film surface density being tested, and the small lag time inherent to each actuator's own motion is negligible compared to this scale.
The design of the controller takes the controlled object model as the premise, and models on the base material of the mechanism analysis, so that the modeling flow is simplified, and the frequent parameter self-setting process of the controller in the production process is omitted.
On the basis of the above-mentioned surface density control system, the embodiment of the present invention further provides another surface density control system, as shown in fig. 6, the screw pump 2 includes a frequency converter 21, and the first controller 1 includes a second judging module 11, a second calculating module 12, and a third calculating module 13.
The second calculating module 12 is configured to obtain the surface density of each sub-area, calculate an average value of the surface densities according to the surface density of each sub-area, and send the average value of the surface densities to the second judging module 11;
the second judging module 11 is used for judging whether the average value of the surface density reaches a second given value; if the second set value is not reached, generating a second surface density difference value according to the surface density average value and the second set value; and sends the second areal density difference to the third calculation module 13; the third calculation module 13 is configured to calculate the second surface density difference according to a built-in second preset algorithm, obtain a second calculation result, and adjust the frequency of the frequency converter 21 according to the second calculation result, so as to adjust the slurry flow rate of the screw pump 2 extracted from the slurry tank 7.
The screw pump 2 includes a frequency converter 21, a pump motor, and a pump body that are sequentially connected, the frequency converter 21 is connected with the first controller 1, the second preset algorithm is a combined integration algorithm, in which a digitized control algorithm, that is, a combined integration algorithm, may be integrated in the first controller 1 when actually implemented, and in addition, the first controller 3 may further include a second judging module 11, a second calculating module 12, and a third calculating module 13 that are communicatively connected; when the first controller 1 receives the surface density of each sub-area fed back by the detection sensor, the second calculation module 12 can be used for calculating the surface density average value, the second judgment module 11 is used for judging whether the surface density average value is consistent with a second given value, if not, the difference value between the surface density average value and the second given value can be calculated, and a second surface density difference value is obtained; and sends the second areal density difference to the third calculation module 13; the third calculation module 32 calculates the second surface density difference according to a built-in combined integral algorithm to obtain a corresponding slurry flow adjustment amount (i.e., a second calculation result), and according to the slurry flow adjustment amount, the first controller 1 outputs the corresponding signal to the frequency converter 21 to adjust the frequency of the frequency converter 21 so as to adjust the motor rotation speed in the pump body, thereby adjusting the slurry flow extracted from the slurry tank 7 by the screw pump 2.
For example, if the difference between the surface density average value and the second set point is minus 5, a second calculation result corresponding to the case that the surface density average value is minus 5 may be calculated to control the frequency of the frequency converter 21 according to the second calculation result, and if the original surface density average value is smaller than the second set point, the frequency needs to be increased to increase the slurry flow rate of the screw pump 2 from the slurry tank, so that the surface density average value becomes larger, and the second set point is reached.
Specifically, the discretized input-output expression of the combined integration algorithm of the single-input single-output system is as follows:
；
wherein K is 2 、T 2 Respectively representing the proportionality coefficient and the time constant of the controlled object; t is t 2 、t 3 Respectively represent a first lag time and a second lag time of the controlled object,respectively representing the output (corresponding to the second calculation result) and the deviation input (corresponding to the second surface density difference value) of the first controller at the kth time point and +.>Is the sampling time (per unitT is exceeded s Time, obtain one input/output value). />The adjustable parameter of the first controller (i.e. the second adjustable parameter) needs to be set according to the actual situation.
The term corresponds to the output at length t 2 The output value of the pump controller is prevented from being changed drastically to a certain extent when the area density detection short-time failure causes the area density of the substrate in the tape feeding direction to be greatly fluctuated, so that the mutual influence between the inner loop controller and the outer loop controller of the system is reduced, and the algorithm is applied to the outer loop controller (pump controller) to effectively relieve the coupling of the system.
Further, the predictive PI algorithm includes a first adjustable parameter; the value of the first adjustable parameter is half of the lag time; wherein the lag time is the lag time constant in the first-order inertial-link expression corresponding to the corresponding die head adjusting block 41.
Further, the combined integration algorithm includes a second adjustable parameter; the difference between the value of the second adjustable parameter and the value of the first adjustable parameter satisfies a preset threshold range.
In actual implementation, through reasonable setting of the parameters of the controllers, the coupling phenomenon between the inner ring controller and the outer ring controller can be further weakened. Specifically, the non-adjustable parameters of each controller are determined by combining empirical preset and adaptive adjustment according to system data in the running process, the adjustable parameters are artificially changed according to actual requirements, and generally, the larger the system is, the stronger the robustness of the system is.
According to the predictive PI algorithm and the combined integral algorithm, only one adjustable parameter exists between the predictive PI algorithm and the combined integral algorithm, so that the design difficulty of the first controller and the second controller is simplified, and the mutual influence between the two controllers caused by unreasonable parameter setting is avoided to a certain extent.
Specifically, according to the actual situation of production, an appropriate second controller adjustable parameter value (i.e., the first adjustable parameter) may be selected, where the value of the second controller adjustable parameter is related to the system lag time and is appropriately increased (the second controller adjustable parameter value is generally set to be half of the lag time), so as to slow down the adjustment strength of the second controller (i.e., the die head adjusting block controller).
On the other hand, by optimizing the values of the adjustable parameters, for example, performing differential values on the first adjustable parameter and the second adjustable parameter, a slight time difference exists between the inner ring and the outer ring, so that the coupling of the system is further lightened.
In general, the difference between the value of the second adjustable parameter and the value of the first adjustable parameter should be greater than or equal to the lowest preset threshold and less than or equal to the highest preset threshold, that is, satisfy the preset value interval.
The reasonable collocation of the predictive PI algorithm and the combined integral algorithm not only relieves the negative effect caused by the large time lag of the system, but also further reduces the coupling of the system.
In practical application, the action range of the actuating mechanism has strict physical limitation, and most control algorithms including a predictive PI algorithm and a combined integration algorithm have an integration link, so that the phenomenon of integration saturation of the control system is easy to occur.
The actual modes of operation of the controller are generally divided into two types, namely a position type and an increment type: the expression of the position type is shown as the previous two algorithm expressions, and the integral term of the second controllerIntegrating all bias inputs from time 0 to current time k, which is a global integration; incrementally subtracting the control amount at the current time (output value, i.e., first calculation result) from the control amount at the previous time, taking the difference as a new control amount (corresponding to the difference between the first calculation result at the current time and the previous calculation result The target calculation result is obtained, and the corresponding die regulator is controlled based on the target calculation result), which is a recursive algorithm, i.e., the output is no longer u (k), but Δu (k) =u (k) -u (k-1). Taking predicted PI as an example, the incremental writing is as follows:
incremental controller advantage: (1) Slowing down the sharp fluctuations in output results in reduced areal density uniformity and coupling of the pump adjustment to the die conditioning block. And (2) the impact is small during manual-automatic switching. When the control action is switched from manual to automatic, the non-disturbance switching can be performed; (3) The controller is prevented from entering integral saturation to a certain extent.
On the basis of the above-mentioned surface density control system, the embodiment of the invention also provides another surface density control system, as shown in fig. 7, the control system also comprises an upper computer 8; the upper computer 8 is respectively connected with the first controller 1 and each second controller 3, and is used for sending the first given value to the first controller 1 and sending the second given value to each second controller 3.
The embodiment of the invention also provides an area density control method, as shown in fig. 8, which comprises the following steps:
step S102, the first controller outputs a first instruction according to the received first slurry coating instruction;
Step S104, the screw pump extracts slurry from the slurry tank according to a first instruction and conveys the slurry into a slit of a coating die head;
step S106, each second controller outputs a second instruction according to the received second slurry coating instruction;
step S108, each die head regulating piece adjusts the distance between the die head regulating piece and the bottom of the slit according to the second instruction so as to regulate the slurry flow of the subarea corresponding to the die head regulating piece in the width direction of the lithium battery level substrate;
step S110, each second controller obtains the surface density of the corresponding subarea detected by the detection equipment, and outputs an adjusted second instruction according to the surface density of the corresponding subarea and a preset first given value so as to adjust the surface density of the corresponding subarea according to the adjusted second instruction;
in step S112, the first controller obtains the surface density of each sub-area detected by the detecting device, calculates an average value of the surface densities according to the surface density of each sub-area, and outputs an adjusted first instruction based on the average value of the surface densities and a preset second given value, so as to adjust the surface density of each sub-area according to the adjusted first instruction.
The surface density control method comprises a first controller, a screw pump, detection equipment and a plurality of control unit groups, wherein the first controller and the plurality of control unit groups are connected with the detection equipment, and the first controller is connected with the screw pump; each control unit group comprises a second controller and a die head regulating piece; the detection equipment and the die head adjusting piece are connected with a second controller; each die adjuster acts on a slot of the coating die; the screw pump is connected with the coating die head; in the mode, the screw pump is in closed-loop control, the first controller takes the surface density average value as feedback input, the output result can integrally and uniformly change the surface density of each subarea, so that the surface density average value can follow a given value, each second controller only takes the surface density of the corresponding subarea as feedback input, the output result can change the surface density of the corresponding subarea, so that the surface density of the corresponding subarea can follow the given value, the influence of pump adjustment on die head adjustment is reduced, and the coupling effect between a die head adjusting piece and the screw pump is reduced to a certain extent.
The implementation principle and the generated technical effects of the surface density control method provided by the embodiment of the invention are the same as those of the embodiment of the surface density control system, and the embodiment part of the surface density control method can refer to the corresponding content in the embodiment of the surface density control system.
Finally, it should be noted that: the above examples are only specific embodiments of the present invention, and are not intended to limit the scope of the present invention, but it should be understood by those skilled in the art that the present invention is not limited thereto, and that the present invention is described in detail with reference to the foregoing examples: any person skilled in the art may modify or easily conceive of the technical solution described in the foregoing embodiments, or perform equivalent substitution of some of the technical features, while remaining within the technical scope of the present disclosure; such modifications, changes or substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention, and are intended to be included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (10)
1. An areal density control system, the control system comprising: the device comprises a first controller, a screw pump, detection equipment and a plurality of control unit groups, wherein the first controller and the control unit groups are connected with the detection equipment, and the first controller is connected with the screw pump; each control unit group comprises a second controller and a die head regulating piece; the detection equipment and the die head adjusting piece are connected with the second controller; each of the die adjusters acts on a slot of a coating die; the screw pump is connected with the coating die head;
the first controller is used for outputting a first instruction according to the received first slurry coating instruction;
the screw pump is used for extracting slurry from a slurry tank according to the first instruction and conveying the slurry into the slit of the coating die head;
each second controller is used for outputting a second instruction according to the received second slurry coating instruction;
each die head adjusting piece is used for adjusting the distance between the die head adjusting piece and the bottom of the slit according to the second instruction so as to adjust the slurry flow of the subarea corresponding to the die head adjusting piece in the width direction of the lithium battery level substrate;
Each second controller is further configured to obtain the surface density of the corresponding sub-region detected by the detection device, and output an adjusted second instruction according to the surface density of the corresponding sub-region and a preset first given value, so as to adjust the surface density of the corresponding sub-region according to the adjusted second instruction;
the first controller is used for acquiring the surface density of each subarea detected by the detection equipment, calculating an average value of the surface density according to the surface density of each subarea, and outputting an adjusted first instruction based on the average value of the surface density and a preset second given value so as to adjust the surface density of each subarea according to the adjusted first instruction.
2. The areal density control system of claim 1 wherein the detection apparatus is a plurality of; each detection device is respectively connected with the first controller and the corresponding second controller;
each detection device is used for detecting the surface density of the corresponding subarea and sending the surface density to the first controller and the corresponding second controller.
3. The areal density control system of claim 2 wherein each of said die adjustment members comprises an interconnected die adjustment block and motor; the motor is connected with the second controller.
4. The areal density control system of claim 3 wherein each of said second controllers comprises a first determination module, a first calculation module;
the first judging module is used for judging whether the surface density of the corresponding subarea reaches the first given value or not; if the first given value is not reached, generating a first surface density difference value according to the surface density and the first given value; transmitting the first area density difference value to the corresponding first computing module;
the first calculation module is used for calculating the first surface density difference value according to a built-in first preset algorithm to obtain a first calculation result, adjusting the rotating speed of a corresponding motor according to the first calculation result, and driving the die head adjusting block to move through the motor so as to adjust the distance between the die head adjusting block and the bottom of the slit.
5. The areal density control system of claim 4 wherein the screw pump comprises a frequency converter and the first controller comprises a second determination module, a second calculation module, a third calculation module;
the second calculation module is used for obtaining the surface density of each subarea, calculating the surface density average value according to the surface density of each subarea, and sending the surface density average value to the second judgment module;
The second judging module is used for judging whether the surface density average value reaches the second given value or not; if the second given value is not reached, generating a second surface density difference value according to the surface density average value and the second given value; and sending the second areal density difference to the third computing module;
the third calculation module is used for calculating the second surface density difference value according to a built-in second preset algorithm to obtain a second calculation result, and adjusting the frequency of the frequency converter according to the second calculation result so as to adjust the slurry flow extracted from the slurry tank by the screw pump.
6. The areal density control system of claim 5 wherein the first predetermined algorithm comprises a predictive PI algorithm; the second preset algorithm includes a combined integration algorithm.
7. The areal density control system of claim 6 wherein the predictive PI algorithm includes a first adjustable parameter; the value of the first adjustable parameter is half of the lag time; the lag time is a lag time constant in a first-order inertial link expression corresponding to the corresponding die head regulating block.
8. The areal density control system of claim 7 wherein the combined integration algorithm comprises a second adjustable parameter; the difference between the value of the second adjustable parameter and the value of the first adjustable parameter meets a preset threshold range.
9. The areal density control system of any one of claims 1-8, wherein the control system further comprises an upper computer; the upper computer is respectively connected with the first controller and each second controller and is used for sending the first given value to the first controller and sending the second given value to each second controller.
10. An areal density control method, characterized by being applied to an areal density control system according to any one of the preceding claims 1 to 9; the method comprises the following steps:
the first controller outputs a first instruction according to the received first slurry coating instruction;
the screw pump extracts slurry from the slurry tank according to the first instruction and conveys the slurry into a slit of the coating die head;
each second controller outputs a second instruction according to the received second slurry coating instruction;
each die head adjusting piece adjusts the distance between the die head adjusting piece and the bottom of the slit according to the second instruction so as to adjust the slurry flow of a subarea corresponding to the die head adjusting piece in the width direction of the lithium battery level substrate;
Each second controller obtains the surface density of the corresponding subarea detected by the detection equipment, and outputs an adjusted second instruction according to the surface density of the corresponding subarea and a preset first given value so as to adjust the surface density of the corresponding subarea according to the adjusted second instruction;
the first controller obtains the surface density of each subarea detected by the detection equipment, calculates the surface density average value according to the surface density of each subarea, and outputs an adjusted first instruction based on the surface density average value and a preset second given value so as to adjust the surface density of each subarea according to the adjusted first instruction.
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