Area density control system and method
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHENZHEN MANST TECH CO LTD
- Filing Date
- 2023-12-27
- Publication Date
- 2026-05-29
Smart Images
Figure CN117798028B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium battery technology, and in particular to an areal density control system and method. Background Technology
[0002] In the lithium-ion battery electrode coating process, the control of electrode surface density depends on the dry film surface density value. Limited by the drying time required for the slurry, a control system designed with dry film surface density as feedback is inevitably a system with significant time lag, posing a major challenge to the design of the control scheme. In existing dry film surface density control schemes, the measured feedback value of the dry film surface density is taken as the average of the surface densities of the corresponding sub-regions from several monitoring sessions. The controller uses a PID controller with parameter self-tuning, further exacerbating the system's time lag. Furthermore, the system contains two adjustment mechanisms simultaneously: a die head adjustment block and a screw pump. The screw pump operates in open-loop control, and the setpoint of the die head adjustment block is the average of the surface densities of all sub-regions. The two adjustment mechanisms are highly coupled, making it difficult for the surface density of each region to follow the setpoint. Summary of the Invention
[0003] The purpose of this invention is to provide a surface density control system and method, which can reduce the coupling effect between the die head adjustment component and the screw pump to a certain extent by reasonably allocating the control logic of the die head adjustment component and the screw pump.
[0004] This invention provides an areal density control system, comprising: a first controller, a screw pump, a detection device, and multiple control unit groups. The first controller and multiple control unit groups are all connected to the detection device, and the first controller is connected to the screw pump. Each control unit group includes a second controller and a die head adjustment component. The detection device and the die head adjustment component are both connected to the second controller. Each die head adjustment component acts on the slit of the coating die head. The screw pump is connected to the coating die head.
[0005] The first controller is used to output a first instruction based on the received first slurry coating instruction;
[0006] The screw pump is used to draw slurry from the slurry tank according to a first command and deliver the slurry to the slit of the coating die head;
[0007] Each second controller is used to output a second instruction based on the received second slurry coating instruction;
[0008] Each die head adjustment component is used to adjust the distance between the die head adjustment component and the bottom of the slit according to the second instruction, so as to adjust the slurry flow rate of the lithium battery grade sheet substrate in the width direction and the sub-region corresponding to the die head adjustment component;
[0009] Each second controller is also used to acquire the surface density of the corresponding sub-region detected by the detection device, and output an adjusted second instruction based on 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.
[0010] The first controller is used to acquire the surface density of each sub-region detected by the detection device, calculate the average surface density based on the surface density of each sub-region, and output an adjusted first instruction based on the average surface density and a preset second given value, so as to adjust the surface density of each sub-region according to the adjusted first instruction.
[0011] Furthermore, there are multiple testing devices; each testing device is connected to a first controller and a corresponding second controller.
[0012] Each detection device is used to detect the areal density of the corresponding sub-region and send the areal density to the first controller and the corresponding second controller.
[0013] Furthermore, each mold head adjusting component includes an interconnected mold head adjusting block and a motor; the motor is connected to a second controller.
[0014] Furthermore, each second controller includes a first judgment module and a first calculation module;
[0015] The first judgment module is used to determine whether the surface density of the corresponding sub-region reaches the first given value; if it does not reach the first given value, it generates a first surface density difference based on the surface density and the first given value; and sends the first surface density difference to the corresponding first calculation module.
[0016] The first calculation module is used to calculate the first surface density difference according to the built-in first preset algorithm, obtain the first calculation result, and adjust the speed of the corresponding motor according to the first calculation result. The motor drives the mold head adjusting block to move, so as to adjust the distance between the mold head adjusting block and the bottom of the slit.
[0017] Furthermore, the screw pump includes a frequency converter, and the first controller includes a second judgment module, a second calculation module, and a third calculation module;
[0018] The second calculation module is used to obtain the surface density of each sub-region, calculate the average surface density based on the surface density of each sub-region, and send the average surface density to the second judgment module;
[0019] The second judgment module is used to determine whether the average surface density reaches the second given value; if it does not reach the second given value, it generates a second surface density difference based on the average surface density and the second given value; and sends the second surface density difference to the third calculation module.
[0020] The third calculation module is used to calculate the second surface density difference according to the built-in second preset algorithm, obtain the second calculation result, and adjust the frequency of the frequency converter according to the second calculation result to adjust the flow rate of slurry pumped from the slurry tank by the screw pump.
[0021] Furthermore, the first preset algorithm includes a predictive PI algorithm; the second preset algorithm includes a combined integral algorithm.
[0022] Furthermore, 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 expression of the first-order inertial element corresponding to the modulus adjustment block.
[0023] Furthermore, the combined integral 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.
[0024] Furthermore, the control system also includes a host computer; the host computer is connected to the first controller and each of the second controllers respectively, and is used to send a first given value to the first controller and a second given value to each of the second controllers.
[0025] This invention provides a surface density control method, applicable to any of the above-mentioned surface density control systems; the method includes:
[0026] The first controller outputs a first instruction based on the received first slurry coating instruction;
[0027] According to the first command, the screw pump draws slurry from the slurry tank and delivers the slurry to the slit of the coating die head;
[0028] Each second controller outputs a second instruction based on the received second slurry coating instruction;
[0029] Each die head adjustment component adjusts the distance between the die head adjustment component and the bottom of the slit according to the second instruction, so as to adjust the slurry flow rate of the lithium battery grade sheet substrate in the width direction and the sub-region corresponding to the die head adjustment component;
[0030] Each second controller acquires the surface density of the corresponding sub-region detected by the detection device, and outputs an adjusted second instruction based on 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.
[0031] The first controller acquires the surface density of each sub-region detected by the detection device, calculates the average surface density based on the surface density of each sub-region, and outputs an adjusted first instruction based on the average surface density and a preset second given value, so as to adjust the surface density of each sub-region according to the adjusted first instruction.
[0032] This invention provides a surface density control system and method, comprising a first controller, a screw pump, a detection device, and multiple control unit groups. The first controller and multiple control unit groups are all connected to the detection device, and the first controller is connected to the screw pump. Each control unit group includes a second controller and a die head adjustment component. The detection device and the die head adjustment component are both connected to the second controller. Each die head adjustment component acts on the slit of the coating die head. The screw pump is connected to the coating die head. In this method, the screw pump is under closed-loop control. The first controller uses the average surface density as feedback input, and its output can uniformly change the surface density of each sub-region, ensuring that the average surface density follows a given value. Each second controller uses only the surface density of its corresponding sub-region as feedback input, and its output can change the surface density of that corresponding sub-region, ensuring that the surface density of that sub-region follows a given value. This reduces the impact of pump adjustment on die head adjustment and, to a certain extent, reduces the coupling effect between the die head adjustment component and the screw pump. Attached Figure Description
[0033] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0034] Figure 1 A schematic diagram of an areal density control loop provided in an embodiment of the present invention;
[0035] Figure 2 This is a schematic diagram of the structure of an areal density control system provided in an embodiment of the present invention;
[0036] Figure 3 This is a schematic diagram of another areal density control loop provided in an embodiment of the present invention;
[0037] Figure 4 This is a schematic diagram of another areal density control system provided in an embodiment of the present invention;
[0038] Figure 5 This is a schematic diagram of another areal density control system provided in an embodiment of the present invention;
[0039] Figure 6 This is a schematic diagram of another areal density control system provided in an embodiment of the present invention;
[0040] Figure 7 This is a schematic diagram of another areal density control system provided in an embodiment of the present invention;
[0041] Figure 8This is a flowchart of a surface density control method provided in an embodiment of the present invention. Detailed Implementation
[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0043] In the lithium-ion battery electrode coating process, coating is used to uniformly coat the positive and negative electrode slurries onto the substrate, which are then dried in an oven to form the positive and negative electrode coatings. Correspondingly, areal density is divided into wet film areal density before drying and dry film areal density after drying. When the wet film areal density is unmeasurable or its measurement is inaccurate, the control of electrode areal density depends on the dry film areal density value. In existing dry film areal density control schemes, the feedback value for each coating die adjustment is the average of several monitoring measurements of the areal density of the corresponding zone (i.e., summing the areal density values of the zone obtained at several sampling times and then dividing by the number of sampling times to obtain the average), and the average of the average values of several monitoring measurements of the areal density of each zone (i.e., summing the average values of several monitoring measurements of the areal density of each zone and then dividing by the number of zones to obtain the average). The controller uses a PID controller with parameter self-tuning, and the pump is an open-loop design. For details, please refer to... Figure 1 The diagram shows a surface density control loop. Typically, the pump speed is controlled by manually setting the pump inverter setpoint based on accumulated work experience; the average value of several surface density monitoring readings for the corresponding zone is taken as the reference value. Figure 1 The average density of the substrate in the width direction of zone 1, the average density of the substrate in the width direction of zone 2, ..., the average density of the substrate in the width direction of zone N; the average index of the average of the density of each zone after several monitoring sessions is taken. Figure 1The average of the areal density values is used as the average value of the areal density of each zone. The average areal density of each zone is used as the feedback input to the corresponding zone's control block controller, and the average of the areal density values is used as the setpoint for all control blocks. Due to the time required for slurry drying, existing control systems designed with dry film areal density values as feedback are inherently systems with large time delays, posing a significant challenge to control scheme design. Existing control schemes using self-tuning PID controllers are limited by their own characteristics (resulting in decreased control performance for controlled objects with large time delays) and have design flaws in the overall closed-loop system (for example, using the average of several areal density monitoring readings for a corresponding zone as the feedback value for adjusting the corresponding coating die further exacerbates the system's time delay). This makes it difficult to mitigate the adverse effects of large time delays (reducing the stability of areal density and the quality of battery electrodes, increasing the difficulty of areal density control). Furthermore, the system contains two adjustment mechanisms: a die head adjustment block and a screw pump. These two mechanisms are coupled, making it difficult for the system output to follow the setpoint. Specifically, the setpoint for each die head adjustment block is the average of the areal density values. This value is time-varying due to the pump's influence, so even slight changes in the pump can have a significant impact on the areal density. Moreover, the pump is an open-loop control system with poor anti-interference capabilities. If manual adjustment is not timely, or if abnormal areal density values occur, it will have a significant impact on the average areal density values, making it more difficult to adjust the die head adjustment blocks and causing the areal density to fail to follow the setpoint.
[0044] Based on this, the present invention provides a surface density control system and method that can mitigate the negative impact of large hysteresis associated with dry film surface density measurement. By rationally allocating the control logic of the die head adjustment block and the screw pump and adopting appropriate parameter settings, it has strong anti-interference ability and robustness, and reduces the coupling effect between the two to a certain extent.
[0045] To facilitate understanding of this embodiment, a surface density control system disclosed in this embodiment of the invention will first be described in detail.
[0046] This invention provides an areal density control system, such as... Figure 2 As shown, the control system includes: a first controller 1, a screw pump 2, a detection device 5, and multiple control unit groups; the first controller 1 and the multiple control unit groups are all connected to the detection device 5, and the first controller 1 is connected to the screw pump 2; each control unit group includes a second controller 3 and a die head adjusting component 4; the detection device 5 and the die head adjusting component 4 are both connected to the second controller 3; each die head adjusting component 4 acts on the slit of the coating die head 6; the screw pump 2 is connected to the coating die head 6;
[0047] The first controller 1 is used to output a first instruction according to the received first slurry coating instruction;
[0048] The screw pump 2 is used to draw slurry from the slurry tank 7 according to the first instruction and deliver the slurry to the slit of the coating die head 6;
[0049] Each second controller 3 is used to output a second instruction according to the received second slurry coating instruction;
[0050] Each die head adjustment block 4 is used to adjust the distance between the die head adjustment block 4 and the bottom of the slit according to the second instruction, so as to adjust the slurry flow rate of the sub-region corresponding to the die head adjustment block 4 in the width direction of the lithium battery grade sheet substrate.
[0051] Each second controller 3 is also used to acquire the surface density of the corresponding sub-region detected by the detection device 5, and output an adjusted second instruction based on 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.
[0052] The first controller 1 is used to acquire the surface density of each sub-region detected by the detection device 5, calculate the average surface density based on the surface density of each sub-region, and output an adjusted first instruction based on the average surface density and a preset second given value, so as to adjust the surface density of each sub-region according to the adjusted first instruction.
[0053] The first controller 1 mentioned above can be understood as the controller of the screw pump 2, and the second controller 3 mentioned above can be understood as the controller of the die head adjusting component 4.
[0054] The aforementioned screw pump 2 can be understood as a rotary pump that transports or pressurizes liquid by relying on the change and movement of the meshing space volume formed by the pump body and the screw. When the driving screw rotates, it drives the driven screw meshing with it to rotate as well. The screw meshing space volume at the suction end gradually increases, and the pressure decreases. Liquid enters the meshing space volume under the action of pressure difference. When the volume increases to its maximum and forms a sealed cavity, the liquid moves continuously axially within each sealed cavity until it reaches the discharge end. At this time, the screw meshing space volume at the discharge end gradually decreases, discharging the liquid. Screw pumps are classified according to the number of screws into single-screw pumps, twin, three, and five-screw pumps, etc.
[0055] In fact, lithium battery plates generally include plate substrates and plate slurry coated on both sides of the substrate. The positive and negative electrode plates of lithium batteries are mostly coated by extrusion. The coating die is an important component of the coating machine. Under certain pressure, the slurry is extruded and sprayed out along the gap of the coating die (equivalent to the slit mentioned above) and coated onto the substrate.
[0056] Specifically, the coating machine, the coating die 6, and the die adjusting component 4 are subordinate to each other. The coating die 6 is an essential core component of the coating machine. The die adjusting component 4 is a part on the coating die 6. Specifically, it can act on the gap of the coating die 6, which is equivalent to adding a certain obstruction to the narrow gap through the die adjusting component 4. In actual implementation, the coating die 6 can move up and down relative to the gap. By controlling the distance between the die adjusting component 4 and the bottom of the gap (that is, the vertical distance between the lower surface of the die adjusting component 4 and the bottom of the gap), the coating thickness (that is, the areal density of the coating sheet) can be finely adjusted so that the coating thickness meets the process requirements.
[0057] Specifically, the multiple die head adjustment components 4 on the slit are independent of each other. They can be understood as multiple independent die head adjustment components 4 arranged laterally on the slit to adjust the flow rate of the slurry at different positions in the lateral direction (which can be understood as the lateral position corresponding to each die head adjustment component in the slit, i.e., multiple sub-regions in the width direction of the lithium battery-grade sheet substrate), thereby adjusting the areal density of the corresponding sub-regions. There is a one-to-one correspondence between each die head adjustment component and each lateral position, and there is also a one-to-one correspondence between each lateral position and each sub-region. Therefore, there is also a one-to-one correspondence between each die head adjustment component and each sub-region.
[0058] The aforementioned testing device 4 can be set up independently or on the coating machine. It is used to detect the surface density of each sub-region on the substrate after coating with slurry, and to feed back the surface density of each sub-region to the first controller 1. The surface density of each sub-region is also fed back to the second controller 3 connected to the die head adjustment component 4 corresponding to that sub-region.
[0059] The aforementioned screw pump 2 can be connected to the coating die head 6 via a pipeline to transport the slurry through the pipeline to the die head cavity of the coating die head 6, and then to the slit connected to the die head cavity.
[0060] In actual implementation, the first controller 1 generally integrates a digital control algorithm (which may be a combined integral algorithm) to control the screw pump 2, thereby controlling the average surface density of the substrate in the substrate conveying direction (i.e., parallel to the substrate's forward direction) (i.e., the average value obtained by summing the surface densities of each sub-region in the substrate width direction); the second controller 3 generally integrates a digital control algorithm (which may be an IP algorithm) to control the die head adjusting block 4, thereby controlling the surface density of the corresponding sub-region in the substrate width direction (i.e., perpendicular to the substrate's forward direction).
[0061] Each of the above-mentioned second controllers 3 can correspond to a mold head adjustment component 4, a surface density partition in the width direction of the substrate to be sprayed (that is, a sub-region in the width direction of the lithium battery grade sheet substrate), and the surface density of the surface density partition (that is, the surface density of the corresponding sub-region). The surface density of each sub-region is also called the surface density of each surface density partition in the width direction of the substrate. Assuming there are 5 mold head adjustment blocks, they correspond to 5 second controllers, 5 sub-regions in the width direction of the substrate, and 5 surface densities in the width direction of the substrate.
[0062] In the specific implementation process, when the coating work begins, the host computer can send a first slurry coating instruction to the first controller 1 and a second slurry coating instruction to the second controller 3. The first slurry coating instruction can carry a second surface density standard value (equivalent to the above-mentioned preset second given value) given in advance according to the actual situation, and the second slurry coating instruction can carry a first surface density standard value (equivalent to the above-mentioned preset first given value) given in advance according to the actual situation. Generally, the preset first given value and the preset second given value are the same.
[0063] After receiving the second given value, the first controller 1 calculates the total slurry flow rate corresponding to the given total areal density (i.e., the product of the second areal density standard value and the number of die head adjustment components). It then outputs a first command carrying the total slurry flow rate to the screw pump 2, controlling the screw pump 2 to adjust its speed so that the screw pump 2 draws slurry corresponding to the total slurry flow rate from the slurry tank 7 and delivers it to the slit of the coating die head 6. After the total slurry flow rate in the slit is adjusted by the die head adjustment component 4, it can be output through the slit to each sub-region of the substrate to complete the coating of each sub-region and obtain the areal density (i.e., the thickness of the slurry coating) of each sub-region.
[0064] After receiving the first given value, the second controller 3 calculates the distance (i.e., the distance between the die head adjustment component 4 and the bottom of the slit) corresponding to the first given value (in actual implementation, the surface density of each surface density partition should be uniform and consistent with the first given value). It then outputs a second instruction carrying this distance to the corresponding die head adjustment component 4, controlling the corresponding die head adjustment component 4 to adjust its height. This allows the corresponding die head adjustment component 4 to adjust the slurry flow rate of the sub-region corresponding to the die head adjustment component 4 in the width direction of the lithium battery grade sheet substrate through the slit, thereby adjusting the surface density of the sub-region to meet the first given value.
[0065] However, in actual implementation, various interferences may cause the slurry flow rate output to the sub-region through the slit to not reach or exceed the slurry flow rate corresponding to the first given value, resulting in the surface density of the corresponding sub-region not meeting the first given value. Therefore, the second controller 3 corresponding to the sub-region that does not meet the first given value can be determined first. By using the difference between the surface density of the sub-region and the pre-acquired first given value, the second controller 3 can be used to control the corresponding die head adjustment component 4, thereby adjusting the surface density of the corresponding sub-region. Specifically, if the surface density of the corresponding sub-region does not meet the first given value, the control of the corresponding die head adjustment component 4 can be repeated until the surface density of the corresponding sub-region meets the first given value.
[0066] Specifically, the detection device 5 feeds back the surface density of each detected sub-region to the second controller 3 connected to the die head adjustment component 4 corresponding to that sub-region. The second controller 3 can calculate the difference between the surface density of the sub-region and the first given value, as well as the distance adjustment amount corresponding to the difference. It then outputs a second instruction carrying the adjusted distance adjustment amount to the corresponding die head adjustment component 4, controlling the die head adjustment component 4 to adjust its height, thereby adjusting the flow rate of slurry delivered to the corresponding sub-region through the lateral position of the slit, and thus adjusting the surface density of the corresponding sub-region.
[0067] However, in actual implementation, the total slurry drawn from the slurry tank may not meet the actual requirements, resulting in a situation where even if the process is repeated multiple times, the areal density of the corresponding sub-region cannot meet the first given value. Therefore, the first controller 1 and the second controller 3 can be combined to jointly control the areal density of multiple sub-regions, so that the areal density of the corresponding sub-region meets the first given value (that is, the areal density of the corresponding sub-region is the same as the first given value), and at the same time, the average areal density meets the second given value (that is, the areal density of each sub-region meets the first given value). Specifically, the average areal density (that is, the areal density in the substrate belt direction) can be obtained, and then the screw pump 2 can be controlled according to the difference between the average areal density and the pre-obtained second given value, thereby adjusting the areal density of each sub-region.
[0068] Specifically, after the detection device 5 feeds back all the areal densities of each sub-region to the first controller 1, the first controller 1 can calculate the average areal density, the difference between the average areal density and the preset second given value, and the slurry flow rate adjustment amount corresponding to the difference. It then outputs the adjusted first command carrying the slurry flow rate adjustment amount to the screw pump 2, controls the screw pump 2 to adjust its rotation speed, so as to adjust the slurry flow rate delivered by the screw pump 2 to the slit of the coating die head 6, thereby adjusting the areal density of all sub-regions (equivalent to adjusting the average areal density).
[0069] To better understand the above embodiments, please refer to, for example... Figure 3The diagram shows a surface density control loop, which includes multiple controlled objects and an automatic control mechanism. The automatic control mechanism mainly consists of a die head controller (equivalent to each second controller) and a pump controller (equivalent to the first controller) for each die head adjusting block. The controlled objects are primarily the surface density of the substrate width-direction partitions corresponding to each die head adjusting block (equivalent to the surface density of each sub-region), such as... Figure 3 As shown, the controlled objects include the areal density of the substrate width direction partition 1, the areal density of the substrate width direction partition 2, ..., the areal density of the substrate width direction areal density partition N; the automatic control mechanism includes the die head controller 1 (i.e. the controller of the die head adjusting block 1), the die head controller 2, ..., the die head controller N, and the pump controller (equivalent to the second controller).
[0070] Logically, both the areal density of the substrate width sections and the areal density of the substrate in the belt-carrying direction (parallel to the substrate's forward direction) (i.e., the average areal density in the substrate width direction, equivalent to the average areal density) should maintain the same set value. Therefore, both the pump controller and each die head controller have set signal inputs (equivalent to the first set value and the second set value). The areal density of each substrate width section is only fed back to the corresponding die head controller. For example, the negative feedback signal of die head adjustment controller 1 comes only from the areal density of substrate width section 1. The average areal density of the substrate width reflects the areal density of the substrate in the belt-carrying direction at this moment and is fed back to the pump controller.
[0071] Each die head controller and its corresponding substrate width-direction areal density form a small closed-loop control loop. These small closed-loop control loops together form a large inner-loop control loop, which is used as the controlled object of the pump controller, meaning the pump controller is in the outer-loop control loop. Therefore, the entire control system consists of dual closed-loop loops. Compared to the single-loop system of traditional control schemes, the added outer-loop control loop can play a role in anti-interference control. The controlled object of each pump controller includes the controlled object of the die head controller, reducing the mutual influence between the inner and outer loop controllers and improving the system's anti-interference performance. Thus, the system reduces coupling. The pump controller can calculate the average areal density based on the average areal density in the substrate width direction and control the areal density of each substrate width-direction zone in real time, uniformly changing the areal density of each zone. The areal density fluctuation of each zone is small, reducing the control difficulty of the die head controller, thereby reducing the influence between the die head controller and the pump controller, reducing coupling, and avoiding the large fluctuations in areal density caused by long intervals of manual open-loop control and untimely control, which increases the control difficulty of the die head controller and causes serious coupling. Furthermore, traditional dual-loop control loops generally contain primary and secondary controlled objects, while the dual-loop loop in this embodiment contains only one actual controlled object (the surface density of the substrate width direction partition corresponding to each mold head adjustment block, that is, the surface density of each sub-region), thus simplifying the system structure.
[0072] Furthermore, compared with traditional control schemes, in this embodiment, the setpoint of the mold head controller is not the average of the average values of the surface density of each partition monitored several times. The average of the average values of the surface density of each partition does not need to be fed back to the mold head controller. The feedback of the mold head controller is only the surface density of the corresponding partition. In fact, the setpoint of the mold head controller is pre-given by the host computer. The pump controller does not affect the setpoint pre-given by the host computer, further reducing the mutual influence between the inner and outer loop controllers.
[0073] Furthermore, compared with traditional control schemes, the value fed back to the head controller in this embodiment is the corresponding partition surface density detected at the current sampling time, rather than the average value of several monitoring of the corresponding partition surface density, so it will not aggravate the system's time delay.
[0074] The areal density control system provided in the above embodiments includes a first controller, a screw pump, a detection device, and multiple control unit groups. The first controller and multiple control unit groups are all connected to the detection device, and the first controller is connected to the screw pump. Each control unit group includes a second controller and a die head adjustment component. The detection device and the die head adjustment component are both connected to the second controller. Each die head adjustment component acts on the slit of the coating die head. The screw pump is connected to the coating die head. In this method, the screw pump is under closed-loop control. The first controller uses the average areal density as feedback input, and its output can uniformly change the areal density of each sub-region, allowing the average areal density to follow a given value. Each second controller only uses the areal density of its corresponding sub-region as feedback input, and its output can change the areal density of the corresponding sub-region, allowing the areal density of the corresponding sub-region to follow a given value. This reduces the impact of pump adjustment on die head adjustment and, to a certain extent, reduces the coupling effect between the die head adjustment component and the screw pump.
[0075] Based on the above-described areal density control system, this embodiment of the invention also provides another areal density control system, such as... Figure 4 As shown, the control system includes multiple detection devices 5; each detection device 5 is also connected to the first controller 1 and the corresponding second controller 3.
[0076] Each detection device 5 is used to detect the surface density of the corresponding sub-region and send the surface density to the first controller 1 and the corresponding second controller 3.
[0077] The aforementioned detection device 5 (also known as peripheral equipment) can be understood as a detection sensor used to collect and report surface density.
[0078] In actual implementation, each detection sensor can correspond one-to-one with each sub-region. It can be set individually or on the coating machine. It is used to detect the surface density of the corresponding sub-region on the substrate after the slurry is coated. The surface density of each corresponding sub-region is fed back to the first controller 1, and the surface density of the corresponding sub-region is fed back to the second controller 3 corresponding to that sub-region.
[0079] Based on the above-described areal density control system, this embodiment of the invention also provides another areal density control system, such as... Figure 5 As shown, each mold head adjusting component 4 includes a mold head adjusting block 41 and a motor 42 connected to each other; the motor 42 is connected to the corresponding second controller 3.
[0080] Each second controller 3 includes a first judgment module 31 and a first calculation module 32;
[0081] The first judgment module 31 is used to determine whether the surface density of the corresponding sub-region reaches the first given value; if it does not reach the first given value, it generates a first surface density difference based on the surface density of the corresponding sub-region and the first given value; and sends the first surface density difference to the corresponding first calculation module 32; the first calculation module 32 is used to calculate the first surface density difference according to the built-in first preset algorithm, obtain the first calculation result, and adjust the speed of the corresponding motor 42 according to the first calculation result, so as to drive the mold head adjustment block 41 to move (generally up and down) through the motor 42 to adjust the distance between the mold head adjustment block 41 and the bottom of the slit.
[0082] The aforementioned motor 42 is connected to the die head adjusting block 41, which acts on the slit of the coating die head 6. The aforementioned first preset algorithm is a predictive PI algorithm. In actual implementation, each second controller 3 can integrate a digital control algorithm, i.e., a predictive PI algorithm. In addition, each second controller 3 can also include a first judgment module 31 and a first calculation module 32 connected in communication. When the second controller 3 receives the surface density of the corresponding sub-region fed back by the detection sensor, it can use the first judgment module 31 to determine whether the surface density is consistent with the first given value. If they are inconsistent, it can calculate... The difference between the surface density and the first given value is obtained to obtain the first surface density difference value; and the first surface density difference value is sent to the corresponding first calculation module 32; the first calculation module 32 calculates the first surface density difference value according to the built-in predictive PI algorithm to obtain the distance between the corresponding die head adjustment block 41 and the bottom of the slit (equivalent to obtaining the height position of the corresponding die head adjustment block 41 in the coating die head 6), which is the first calculation result. According to the first calculation result, the speed of the motor 42 connected to the corresponding die head adjustment block 41 can be adjusted to drive the die head adjustment block 41 to move to the position corresponding to the first calculation result.
[0083] For example, if the difference between the surface density of the sub-region and the first given value is negative 2, then the first calculation result corresponding to the first ground density difference of 2 can be calculated, and the speed of motor 42 can be controlled according to the first calculation result. If the original surface density of the sub-region is less than the first given value, the distance needs to be increased so that the slurry flow rate output from the corresponding lateral position in the slit increases, thereby increasing the surface density of the corresponding sub-region to reach the first given value.
[0084] In practice, the aforementioned predictive PI algorithm, when dealing with objects with large time delays, collects and processes system data from the past period for calculation. Compared to the PID controller in traditional control schemes, it can effectively mitigate the negative impact of large time delay caused by dry film surface density measurement.
[0085] Specifically, the discretized input-output expression of the prediction PI algorithm for a single-input single-output system is:
[0086] in, t1 and t2 represent the proportional coefficient and time constant of the controlled object, respectively; t1 represents the lag time of the controlled object. These represent the controller's output at time k (equivalent to the first calculation result mentioned above) and the deviation input (equivalent to the first surface density difference mentioned above), respectively. It is the sampling time (every T) s (At each time point, obtain one input / output value). This is the adjustable parameter of the second controller (also known as the first adjustable parameter), which needs to be tuned according to the actual situation. The larger the value of this adjustable parameter, the stronger the system robustness. The item possesses the characteristics of a PI controller, while The term can be understood as the output of the first controller at a certain moment k being influenced by the historical output of the first controller within the interval [k-t1, k). Therefore, the system's lag is compensated accordingly. Applying this algorithm to the inner loop controller (i.e., the module controller) can effectively alleviate the large lag of the system.
[0087] From a mechanistic perspective, the process of viscous slurry being sprayed from a slit onto the substrate can be approximated as a first-order inertial element. Through methods such as step tests, the actual proportionality coefficient (K1 in the above expression) and time constant (T1 in the above expression) of this element can be obtained. It is important to note that each coating die typically contains multiple die adjustment blocks. Due to the influence of the die structure, the expression for the first-order inertial element of the substrate width direction sub-region's areal density corresponding to each die adjustment block is not entirely the same. However, the lag time constant (t1 in the above expression) of each expression should be identical, because this lag time is mainly determined by the time scale from when the slurry is sprayed to when the dry film are measured. Compared to this scale, the inherent small lag time of each actuator's own action can be ignored.
[0088] The controller design is based on the model of the controlled object and is modeled on the basis of the above mechanism analysis, which simplifies the modeling process and eliminates the frequent parameter self-tuning process of the controller in the production process.
[0089] Based on the above-described areal density control system, this embodiment of the invention also provides another areal density control system, such as... Figure 6 As shown, the screw pump 2 includes a frequency converter 21, and the first controller 1 includes a second judgment module 11, a second calculation module 12, and a third calculation module 13.
[0090] The second calculation module 12 is used to obtain the surface density of each sub-region, calculate the average surface density based on the surface density of each sub-region, and send the average surface density to the second judgment module 11.
[0091] The second judgment module 11 is used to determine whether the average surface density reaches the second given value; if it does not reach the second given value, it generates a second surface density difference based on the average surface density and the second given value; and sends the second surface density difference to the third calculation module 13; the third calculation module 13 is used to calculate the second surface density difference according to the built-in second preset algorithm, obtain the second calculation result, and adjust the frequency of the inverter 21 according to the second calculation result to adjust the flow rate of slurry pumped by the screw pump 2 from the slurry tank 7.
[0092] The aforementioned screw pump 2 includes a frequency converter 21, a pump motor, and a pump body connected in sequence. The frequency converter 21 is connected to the first controller 1. The aforementioned second preset algorithm is a combined integral algorithm. In actual implementation, the first controller 1 can integrate a digital control algorithm, i.e., a combined integral algorithm. In addition, the first controller 3 can also include a second judgment module 11, a second calculation module 12, and a third calculation module 13 connected in communication. When the first controller 1 receives the surface density of each sub-region fed back by the detection sensor, it can use the second calculation module 12 to calculate the average surface density and use the second judgment module 11 to determine the surface density. If the average surface density is inconsistent with the second given value, the difference between the average surface density and the second given value can be calculated to obtain the second surface density difference. The second surface density difference is then sent to the third calculation module 13. The third calculation module 32 calculates the second surface density difference according to the built-in combined integral algorithm to obtain the corresponding slurry flow rate adjustment amount (i.e., the second calculation result). According to the slurry flow rate adjustment amount, the first controller 1 outputs the corresponding signal to the frequency converter 21 to adjust the frequency of the frequency converter 21, thereby adjusting the motor speed in the pump body and thus adjusting the slurry flow rate drawn from the slurry tank 7 by the screw pump 2.
[0093] For example, if the difference between the average surface density and the second given value is negative 5, then the second calculation result corresponding to the average surface density being negative 5 can be calculated, and the frequency of the inverter 21 can be controlled according to the second calculation result. If the original average surface density is less than the second given value, the frequency needs to be increased so that the flow rate of slurry pumped by the screw pump 2 from the slurry tank increases, thereby increasing the average surface density to reach the second given value.
[0094] Specifically, the discretized input-output expression of the combinatorial integral algorithm for a single-input single-output system is: ;
[0095] Where K2 and T2 represent the proportional coefficient and time constant of the controlled object, respectively; t2 and t3 represent the first lag time and the second lag time of the controlled object, respectively. These represent the output of the first controller at time k (equivalent to the second calculation result mentioned above) and the deviation input (equivalent to the second surface density difference mentioned above), respectively. It is the sampling time (every T) s (At each time point, obtain one input / output value). It is the adjustable parameter of the first controller (i.e., the second adjustable parameter), which needs to be adjusted according to the actual situation.
[0096] The term is equivalent to performing a mean filtering operation on the output value over a time interval of length t2. Therefore, the combined integral term can be regarded as a mean filter, which can suppress noise and smoothly handle the influence of abnormal fluctuations in the average areal density in the width direction of the substrate. For example, when a short-term failure of areal density detection in a certain section causes a large fluctuation in the areal density in the substrate's belt direction, it can, to some extent, prevent drastic changes in the output value of the pump controller. Therefore, the mutual influence between the inner and outer loop controllers of the system is reduced. Applying this algorithm to the outer loop controller (pump controller) can effectively alleviate the coupling of the system.
[0097] Furthermore, 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 expression of the first-order inertial element corresponding to the corresponding modulus adjustment block 41.
[0098] Furthermore, the combined integral 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.
[0099] In practice, by setting the controller parameters appropriately, the coupling phenomenon between the inner and outer loop controllers can be further reduced. Specifically, the non-adjustable parameters of each controller are determined by a combination of empirical presets and adaptive adjustments based on system data during operation. Adjustable parameters are manually changed according to actual needs, and generally, the larger the parameter, the stronger the system robustness.
[0100] As can be seen from the above predictive PI algorithm and combined integral algorithm, both have only one adjustable parameter, which simplifies the design difficulty of the first controller and the second controller and avoids the mutual influence between the two controllers due to unreasonable parameter settings to a certain extent.
[0101] Specifically, based on the actual production situation, a suitable adjustable parameter value for the second controller (i.e., the first adjustable parameter mentioned above) can be selected. The value of the adjustable parameter of the second controller is related to the system lag time and is appropriately increased (generally, the adjustable parameter value of the second controller is set to half of the lag time) to reduce the adjustment intensity of the second controller (i.e., the mold head adjustment block controller).
[0102] On the other hand, by optimizing the values of adjustable parameters, such as by differentiating the values of the first and second adjustable parameters, a slight time difference can be created between the inner and outer loops, further reducing the coupling of the system.
[0103] Under normal circumstances, 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, it should meet the preset value range.
[0104] The reasonable combination of the aforementioned predictive PI algorithm and combined integral algorithm not only alleviates the negative impact of the large time delay of the system, but also further reduces the coupling of the system.
[0105] In practical applications, the range of motion of the actuator is subject to strict physical limitations, and most control algorithms, including predictive PI algorithms and combined integral algorithms, have integral components, which can easily lead to integral saturation in the control system.
[0106] In practice, controllers generally operate in two ways: positional and incremental. The expression for the positional controller is shown in the first two algorithm expressions. The integral term of the second controller... Integrating all deviation inputs from time 0 to the current time k is a global integration. The incremental method subtracts the control quantity (output value, i.e., the first calculation result) from the control quantity at the current time, using the difference as the new control quantity (equivalent to calculating the difference between the first calculation result at the current time and the previous calculation result to obtain the target calculation result, and controlling the corresponding mold head adjustment component based on the target calculation result). This is a recursive algorithm, meaning the output is no longer u(k), but Δu(k) = u(k) - u(k-1). Taking PI prediction as an example, the incremental method is written as follows:
[0107]
[0108] Advantages of incremental controllers: (1) Reduces the decrease in surface density consistency caused by drastic fluctuations in output value and reduces the coupling of pump adjustment to the mold head adjustment block. (2) Reduces impact during manual-automatic switching. When the control action switches from manual to automatic, a disturbance-free switching can be achieved. (3) To a certain extent, it avoids the controller from entering integral saturation.
[0109] Based on the above-described areal density control system, this embodiment of the invention also provides another areal density control system, such as... Figure 7 As shown, the control system also includes a host computer 8; the host computer 8 is connected to the first controller 1 and each of the second controllers 3 respectively, and is used to send a first given value to the first controller 1 and a second given value to each of the second controllers 3.
[0110] This invention also provides a method for controlling areal density, such as... Figure 8 As shown, the method includes the following steps:
[0111] Step S102: The first controller outputs a first instruction based on the received first slurry coating instruction;
[0112] In step S104, the screw pump draws slurry from the slurry tank according to the first instruction and delivers the slurry to the slit of the coating die head;
[0113] Step S106: Each second controller outputs a second instruction based on the received second slurry coating instruction;
[0114] In step S108, each die head adjustment component adjusts the distance between the die head adjustment component and the bottom of the slit according to the second instruction, so as to adjust the slurry flow rate of the lithium battery grade sheet substrate in the width direction and the sub-region corresponding to the die head adjustment component.
[0115] In step S110, each second controller obtains the surface density of the corresponding sub-region detected by the detection device, and outputs an adjusted second instruction based on 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.
[0116] In step S112, the first controller acquires the surface density of each sub-region detected by the detection device, calculates the average surface density based on the surface density of each sub-region, and outputs an adjusted first instruction based on the average surface density and a preset second given value, so as to adjust the surface density of each sub-region according to the adjusted first instruction.
[0117] The aforementioned areal density control method includes a first controller, a screw pump, a detection device, and multiple control unit groups. The first controller and multiple control unit groups are all connected to the detection device, and the first controller is connected to the screw pump. Each control unit group includes a second controller and a die head adjustment component. The detection device and the die head adjustment component are both connected to the second controller. Each die head adjustment component acts on the slit of the coating die head. The screw pump is connected to the coating die head. In this method, the screw pump is under closed-loop control. The first controller uses the average areal density as feedback input, and its output can uniformly change the areal density of each sub-region, allowing the average areal density to follow a given value. Each second controller uses only the areal density of its corresponding sub-region as feedback input, and its output can change the areal density of the corresponding sub-region, allowing the areal density of the corresponding sub-region to follow a given value. This reduces the impact of pump adjustment on die head adjustment and, to a certain extent, reduces the coupling effect between the die head adjustment component and the screw pump.
[0118] The areal density control method provided in this embodiment of the invention has the same implementation principle and technical effect as the aforementioned areal density control system embodiment. For the areal density control method embodiment, please refer to the corresponding content in the aforementioned areal density control system embodiment.
[0119] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.
Claims
1. A surface density control system, characterized in that, The control system includes: a first controller, a screw pump, a detection device, and multiple control unit groups. The first controller and the multiple control unit groups are all connected to the detection device, and the first controller is connected to the screw pump. Each control unit group includes a second controller and a die head adjusting component. The detection device and the die head adjusting component are both connected to the second controller. Each die head adjusting component acts on the slit of the coating die head. The screw pump is connected to the coating die head. The first controller is configured to output a first instruction based on the received first slurry coating instruction; The screw pump is used to draw slurry from the slurry tank according to the first instruction and deliver the slurry to the slit of the coating die head; Each of the second controllers is used to output a second instruction based on the received second slurry coating instruction; Each of the die head adjustment components is used to adjust the distance between the die head adjustment component and the bottom of the slit according to the second instruction, so as to adjust the slurry flow rate of the sub-region corresponding to the die head adjustment component in the width direction of the lithium battery grade sheet substrate. Each of the second controllers is further configured to acquire the surface density of the corresponding sub-region detected by the detection device, and output an adjusted second instruction based on 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 to acquire the surface density of each sub-region detected by the detection device, calculate the average surface density based on the surface density of each sub-region, and output an adjusted first instruction based on the average surface density and a preset second given value, so as to adjust the surface density of each sub-region according to the adjusted first instruction.
2. The areal density control system according to claim 1, characterized in that, There are multiple detection devices; each detection device is connected to the first controller and the corresponding second controller. Each of the detection devices is used to detect the surface density of the corresponding sub-region and send the surface density to the first controller and the corresponding second controller.
3. The areal density control system according to claim 2, characterized in that, Each of the die head adjustment components includes an interconnected die head adjustment block and a motor; the motor is connected to the second controller.
4. The areal density control system according to claim 3, characterized in that, Each of the second controllers includes a first judgment module and a first calculation module; The first determination module is used to determine whether the surface density of the corresponding sub-region reaches the first given value; if it does not reach the first given value, it generates a first surface density difference based on the surface density and the first given value; and sends the first surface density difference to the corresponding first calculation module. The first calculation module is used to calculate the first surface density difference value according to the built-in first preset algorithm, obtain the first calculation result, and adjust the rotation speed of the corresponding motor according to the first calculation result. The motor drives the mold head adjusting block to move, so as to adjust the distance between the mold head adjusting block and the bottom of the slit.
5. The areal density control system according to claim 4, characterized in that, The screw pump includes a frequency converter, and the first controller includes a second judgment module, a second calculation module, and a third calculation module; The second calculation module is used to obtain the surface density of each sub-region, calculate the average surface density based on the surface density of each sub-region, and send the average surface density to the second judgment module; The second judgment module is used to determine whether the average surface density reaches the second given value; if it does not reach the second given value, a second surface density difference is generated based on the average surface density and the second given value; and the second surface density difference is sent to the third calculation module. The third calculation module is used to calculate the second surface density difference value according to the built-in second preset algorithm, obtain the second calculation result, and adjust the frequency of the frequency converter according to the second calculation result, so as to adjust the flow rate of the slurry pumped from the slurry tank by the screw pump.
6. The areal density control system according to claim 5, characterized in that, The first preset algorithm includes a predictive PI algorithm; the second preset algorithm includes a combined integral algorithm.
7. The areal density control system according to claim 6, characterized in that, 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 expression of the first-order inertial element corresponding to the modulus adjustment block.
8. The areal density control system according to claim 7, characterized in that, The combined integral 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.
9. The areal density control system according to any one of claims 1-8, characterized in that, The control system further includes a host computer; the host computer is connected to the first controller and each of the second controllers respectively, and is used to send the first given value to the first controller and the second given value to each of the second controllers.
10. A method for controlling areal density, characterized in that, The method is applied to the areal density control system according to any one of claims 1-9; the method includes: The first controller outputs a first instruction based on the received first slurry coating instruction; According to the first instruction, the screw pump draws slurry from the slurry tank and delivers the slurry into the slit of the coating die head; Each second controller outputs a second instruction based on the received second slurry coating instruction; Each die head adjustment component adjusts the distance between the die head adjustment component and the bottom of the slit according to the second instruction, so as to adjust the slurry flow rate of the sub-region corresponding to the die head adjustment component in the width direction of the lithium battery grade sheet substrate. Each of the second controllers acquires the surface density of the corresponding sub-region detected by the detection device, and outputs an adjusted second instruction based on 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 acquires the surface density of each sub-region detected by the detection device, calculates the average surface density based on the surface density of each sub-region, and outputs an adjusted first instruction based on the average surface density and a preset second given value, so as to adjust the surface density of each sub-region according to the adjusted first instruction.