Extrusion screw closed-loop control method, device, electronic device and storage medium

Abstract

The present application provides a closed-loop control method, device, electronic device and storage medium for an extruder screw, and relates to the field of screw extruder control technology. The key points of the technical solution are: obtaining the first current of the motor that drives the screw to rotate during the operation of the screw extruder; according to the pre-established current-extrusion amount relationship, controlling the speed of the motor that drives the screw to rotate in the screw extruder to keep the first current stable. The closed-loop control method, device, electronic device and storage medium for an extruder screw provided by the present application have the advantages of being able to adapt to the influence of factors such as screw wear, improving the extrusion amount control accuracy, and reducing maintenance costs.

Description

Technical Field

[0001] The present application relates to the technical field of screw extruder control, and in particular to an extrusion screw closed-loop control method, device, electronic device and storage medium. Background Art

[0002] Plastic extrusion is an important process in the plastic processing industry, in which the stable operation of the screw extruder is crucial to product quality. The traditional screw extruder control method mainly relies on fixed screw speed or pressure parameters, which is difficult to adapt to the influence of factors such as screw wear. Specifically, when the screw is worn after long-term use, the wear will cause the outer diameter of the screw to decrease, or the inner diameter of the barrel to increase, or both will occur at the same time, which will cause the gap between the screw and the barrel to increase. When the gap between the screw and the barrel increases, the increase in the gap will cause more material to flow back between the threads, reducing the amount of material transported forward. The worn thread profile cannot effectively "scrape" the barrel wall, weakening the ability to build pressure, resulting in a decrease in the pressure formed at the extruder head, thereby reducing the extrusion volume. The increase in the gap and the change in the thread profile will reduce the friction between the screw and the material, resulting in a decrease in the torque required for the screw to rotate, which leads to a decrease in the extrusion volume and internal pressure.

[0003] Specifically, for the spinning production line, there are very strict requirements on the stability of the extrusion volume. If the extrusion volume fluctuates, it will greatly affect the product quality.

[0004] The existing method usually adopts closed-loop control based on pressure sensors, but pressure sensors are susceptible to contamination and wear, have high maintenance costs, and the relationship between pressure and actual extrusion volume is not linear, so the control accuracy is limited.

[0005] Therefore, it is necessary to improve the existing technology. Summary of the invention

[0006] The purpose of the present application is to provide an extrusion screw closed-loop control method, device, electronic device and storage medium, which have the advantages of being able to adapt to the influence of factors such as screw wear, improve the extrusion volume control accuracy and reduce maintenance costs.

[0007] In the first aspect, the present application provides an extrusion screw closed-loop control method, and the technical solution is as follows:

[0008] include:

[0009] Obtaining a first current of a motor that drives a screw to rotate during operation of the screw extruder;

[0010] According to the pre-established current-extrusion volume relationship, the rotation speed of the motor driving the screw in the screw extruder is controlled to keep the first current stable.

[0011] Further, in the present application, the step of controlling the rotation speed of the motor driving the screw in the screw extruder according to the pre-established current-extrusion amount relationship so as to keep the first current stable comprises:

[0012] Obtain the first material extrusion amount required for current production;

[0013] According to the extrusion amount of the first material, determining a target current value from the current-extrusion amount relationship;

[0014] The rotation speed of the motor driving the screw in the screw extruder is controlled so that the first current is kept close to the target current value and remains stable after reaching the target current value.

[0015] Further, in the present application, the step of keeping the first current close to the target current value and maintaining stability after reaching the target current value includes:

[0016] When the first current is greater than the target current value, the speed of the motor driving the screw in the screw extruder is controlled to decrease, and after the first current reaches the target current value, the corresponding target speed is obtained, and the target speed is kept constant;

[0017] When the first current is less than the target current value, the speed of the motor driving the screw in the screw extruder is controlled to increase, and after the first current reaches the target current value, the corresponding target speed is obtained, and the target speed is kept constant;

[0018] Also includes:

[0019] When the first current is greater than the target current value and exceeds a first preset value, controlling the motor driving the screw in the screw extruder to stop running;

[0020] When the first current is less than the target current value and less than a second preset value, the speed of the motor driving the screw in the screw extruder is controlled to decrease to a set speed within a specified time.

[0021] Further, in the present application, the step of controlling the speed of the motor driving the screw in the screw extruder to reduce includes:

[0022] Controlling the speed of the motor driving the screw in the screw extruder to decrease according to the set first deceleration time, first deceleration frequency and first deceleration magnitude;

[0023] The step of controlling the speed of the motor driving the screw in the screw extruder to increase includes:

[0024] The rotation speed of the motor driving the screw in the screw extruder is increased according to the set first acceleration time, first acceleration frequency and first acceleration magnitude.

[0025] Further, in the present application, the step of controlling the speed of the motor driving the screw in the screw extruder to decrease according to the set first deceleration time, first deceleration frequency and first deceleration magnitude includes:

[0026] Calculating a first difference between the first current and the target current value;

[0027] The first deceleration time, the first deceleration frequency and the first deceleration magnitude are selected and set according to the first difference value to control the speed of the motor driving the screw in the screw extruder to decrease;

[0028] The step of controlling the speed of the motor driving the screw in the screw extruder to increase according to the set first acceleration time, first acceleration frequency and first acceleration magnitude comprises:

[0029] Calculating a second difference between the first current and the target current value;

[0030] The first acceleration time, the first acceleration frequency and the first acceleration magnitude are selected and set according to the second difference value to control the speed of the motor driving the screw in the screw extruder to increase.

[0031] Furthermore, in the present application, the speed of the motor driving the screw in the screw extruder is controlled by PID control.

[0032] Furthermore, the present application also includes:

[0033] Collecting first data of the first current and the corresponding rotation speed;

[0034] Establishing a current-speed model according to the first data;

[0035] When performing PID control, PID parameters are adjusted according to the current-speed model.

[0036] In a second aspect, the present application also proposes an extrusion screw closed-loop control device, comprising:

[0037] An acquisition module, used for acquiring a first current of a motor that drives a screw to rotate during operation of the screw extruder;

[0038] The control module is used to control the rotation speed of the motor driving the screw in the screw extruder according to the pre-established current-extrusion amount relationship, so that the first current remains stable.

[0039] In a third aspect, the present application further proposes an electronic device, comprising a processor and a memory, wherein the memory stores computer-readable instructions, and when the computer-readable instructions are executed by the processor, the steps in the above method are executed.

[0040] In a fourth aspect, the present application further proposes a storage medium on which a computer program is stored, and when the computer program is executed by a processor, the steps in the above method are executed.

[0041] From the above, it can be seen that the present application provides an extrusion screw closed-loop control method, device, electronic device and storage medium, which obtains the first current of the motor that drives the screw to rotate during the operation of the screw extruder, and controls the speed of the motor that drives the screw to rotate in the screw extruder according to the pre-established current-extrusion amount relationship, so that the first current remains stable, thereby achieving precise control of the extrusion amount, being able to adapt to the influence of factors such as screw wear, and improving the extrusion amount control accuracy. At the same time, it avoids the use of pressure sensors and reduces maintenance costs. It has the advantages of being able to adapt to the influence of factors such as screw wear, improving the extrusion amount control accuracy, and reducing maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A flow chart of an extrusion screw closed-loop control method provided in this application.

[0043] Figure 2 This is a schematic structural diagram of an extrusion screw closed-loop control device provided in this application.

[0044] Figure 3 A schematic diagram of the structure of an electronic device provided in this application.

[0045] Figure 4 A schematic diagram of an extrusion screw closed-loop control method provided in the present application being implemented in a production line.

[0046] In the figure: 210, acquisition module; 220, control module; 310, processor; 320, memory; 400, screw extruder; 500, reducer; 600, motor. DETAILED DESCRIPTION

[0047] The technical solutions in the present application will be clearly and completely described below in conjunction with the drawings in the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The components of the present application generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the present application for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application.

[0048] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. At the same time, in the description of this application, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0049] Plastic extrusion is an important process in the plastic processing industry, in which the stable operation of the screw extruder is crucial to product quality. Early screw extruder control mainly relied on fixed screw speed, which was difficult to adapt to the influence of factors such as screw wear. With the development of technology, closed-loop control methods based on pressure sensors have been introduced, but pressure sensors are susceptible to contamination and wear, have high maintenance costs, and there is a non-linear relationship between pressure and actual extrusion volume, resulting in limited control accuracy.

[0050] In the spinning production line, the stability of the extrusion volume has strict requirements on product quality. However, as the screw is used for a long time, wear will cause the outer diameter of the screw to decrease or the inner diameter of the barrel to increase, which will increase the gap between the screw and the barrel. This increase in gap will cause more material to flow back between the threads, reducing the amount of material transported forward. At the same time, the worn thread profile cannot effectively "scrape" the barrel wall, weakening the ability to build pressure, resulting in a decrease in the pressure formed at the extruder head, thereby reducing the extrusion volume. In addition, the increase in gap and the change in thread profile will reduce the friction between the screw and the material, resulting in a decrease in the torque required for the screw to rotate, further affecting the extrusion volume and internal pressure.

[0051] In this case, the traditional fixed speed or pressure sensor-based control method is difficult to ensure the stability of the extrusion volume. In order to solve this problem, a new method is needed that can adapt to the influence of factors such as screw wear and accurately control the extrusion volume. This method should be able to monitor the operating status of the screw extruder in real time and dynamically adjust the control parameters according to the actual situation to maintain a stable material extrusion volume and avoid changes in extrusion volume due to screw wear, thereby ensuring the stability of product quality.

[0052] When faced with the problem of unstable extrusion volume of screw extruder, we first need to analyze the root cause of this problem. Screw wear is a key factor, which will cause the gap between the screw and the barrel to increase, thus affecting the material delivery and pressure establishment. The traditional fixed speed control method cannot adapt to this change, and the control based on pressure sensors has problems such as high maintenance cost and limited accuracy.

[0053] Then, how to design a method that can adapt to screw wear and accurately control the extrusion volume becomes a problem. An intuitive idea is to directly measure the extrusion volume, but this is often difficult to achieve in actual production. Another idea is to find a parameter related to the extrusion volume that is easy to measure as a control basis.

[0054] Considering that the torque required for screw rotation is correlated with the material extrusion volume, and the motor current can reflect the torque required for screw rotation, the motor current is used as an indirect indicator of the extrusion volume. This method does not require additional sensors, can reduce maintenance costs, and avoids the complexity of directly measuring the extrusion volume or pressure.

[0055] Based on this idea, this application proposes a closed-loop control method for an extrusion screw. Figure 1 , the method includes two key steps:

[0056] S110, obtaining a first current of a motor that drives the screw to rotate during the operation of the screw extruder;

[0057] S120, according to the pre-established current-extrusion amount relationship, controlling the rotation speed of the motor driving the screw in the screw extruder to rotate so that the first current remains stable.

[0058] The core of this method is to use the motor current as an indirect indicator of the extrusion volume, and to indirectly maintain the stability of the extrusion volume by maintaining the current stable. Compared with the traditional control method based on fixed speed or pressure parameters, this method can better adapt to the influence of factors such as screw wear and improve the stability of the extrusion volume.

[0059] In the specific implementation, the current-extrusion relationship needs to be established first. This can be done by fitting experimental data or deducing theoretical models. When establishing this relationship, it is necessary to consider the changes under different working conditions, such as the influence of different materials, different temperatures, different humidity and other factors.

[0060] The motor current can be obtained by adding a current detection device to the motor drive circuit. In order to improve the measurement accuracy, the method of taking the average value of multiple samplings can be adopted, or a filtering algorithm can be used to eliminate the influence of noise.

[0061] The motor speed can be controlled by a frequency converter or other motor drive device. The control algorithm can be PID control, fuzzy control or other advanced control algorithms. The most suitable control method can be selected according to the actual situation.

[0062] In practical applications, it may be necessary to consider the dynamic changes of the current-extrusion relationship. For example, as the degree of screw wear changes, this relationship may change. Therefore, an adaptive mechanism can be designed to regularly update the current-extrusion relationship to ensure long-term control accuracy.

[0063] For example, when the screw extruder is initially operated, the relationship between the current and the extrusion volume is obtained to determine the current degree of wear of the screw, and the corresponding current-extrusion volume relationship is selected according to the current degree of wear of the screw.

[0064] In addition, it is also necessary to consider the handling of some abnormal situations. For example, when the current suddenly increases abnormally, it may indicate a screw blockage or other failure. At this time, the machine should be stopped in time to prevent equipment damage.

[0065] This method allows precise control of the extrusion volume without directly measuring the extrusion volume or pressure. This is of great significance for production lines that require strict and stable extrusion volume (such as spinning production lines), and can effectively improve product quality. At the same time, by avoiding the use of pressure sensors that are susceptible to contamination and wear, maintenance costs are reduced and system reliability is improved.

[0066] In general, the method proposed in this application realizes closed-loop control of the extrusion screw by innovatively utilizing the motor current, that is, the first current of the motor that drives the screw to rotate, as an indirect indicator of the extrusion amount, effectively solving the problem of unstable extrusion amount caused by factors such as screw wear, and providing a new technical means for improving the quality and efficiency of plastic extrusion processing.

[0067] The solution of this application can be implemented in the following specific ways:

[0068] In a specific embodiment, a screw extruder is used to produce polyester fibers. First, a current-extrusion amount relationship is established. This can be done by fitting experimental data or deriving a theoretical model, taking into account the changes under different working conditions, such as the influence of different temperatures, different raw materials, and other factors. Then, a current detection device is set in the motor drive circuit of the screw extruder to monitor the first current of the motor that drives the screw to rotate in real time.

[0069] The control system obtains the first material extrusion amount required for the current production, and determines the target current value according to the pre-established current-extrusion amount relationship. The control system adjusts the motor speed through the inverter so that the actual first current approaches and eventually reaches the target current value. When the actual first current reaches the target current value, the control system keeps the speed unchanged, thereby maintaining a stable extrusion amount.

[0070] In another embodiment, considering that the current-extrusion relationship may change over time, an adaptive mechanism is designed. The system regularly collects data on the first current and the corresponding speed and updates the current-extrusion relationship. This can adapt to long-term changing factors such as screw wear and ensure long-term control accuracy.

[0071] The present application scheme realizes precise control of the extrusion volume by using the first current as an indirect indicator of the extrusion volume. Compared with the traditional fixed speed control, the present scheme can adapt to the influence of factors such as screw wear and maintain a stable extrusion volume. This is particularly important for polyester fiber production lines that require strict and stable extrusion volume, and can significantly improve the consistency of product quality.

[0072] Compared with the closed-loop control method based on pressure sensors, the solution of this application avoids the use of pressure sensors that are susceptible to contamination and wear, reduces maintenance costs, and improves system reliability. In addition, since the relationship between current and extrusion volume is closer to linear, compared with the nonlinear relationship between pressure and extrusion volume, this solution can achieve more precise control.

[0073] In the prior art, the motor speed is usually controlled according to the current to avoid equipment damage. For example, due to the excessive viscosity of the material, the torque of the screw increases, which leads to an increase in current. When the current increases, the motor speed will be reduced to reduce the torque, but this often leads to a reduction in extrusion. The core of the present application is to ensure the stability of the extrusion amount, and to maintain a stable current by adjusting the speed, thereby indirectly maintaining a stable extrusion amount, which is essentially different from the prior art. This method can better meet production needs, especially in scenarios requiring strict and stable extrusion amounts, and can effectively improve the consistency of product quality.

[0074] Specifically, refer to Figure 4 , Figure 4This is a schematic diagram of the application of the method of the present application in an actual spinning production line. The spinning production line is arranged at one end of a screw extruder 400. A feeder is provided on the screw extruder 400 for feeding materials (not shown in the figure). A reducer 500 is provided at the other end of the screw extruder 400. The reducer 500 is connected to a motor 600, the motor 600 is connected to a frequency converter, the frequency converter is connected to a PLC, and the PLC is connected to a host computer. The host computer may specifically include a WINCC host computer and a touch screen. The user may set the current parameters, speed lower limit parameters, target current value parameters, and PID parameters of the overcurrent shutdown through the touch screen. Information such as a first current curve, a screw speed and first current correlation curve may also be displayed. A manual control conversion button may also be provided.

[0075] Specifically, the frequency converter obtains the current information of the motor 600, that is, the first current, and then sends the current information to the PLC, and the PLC executes the control strategy set by the host computer. That is, the host computer sets various parameters to enable the PLC to perform control operations according to the set control strategy after obtaining the first current.

[0076] In addition, the frequency converter can also obtain the current speed information of the motor 600, send the speed information to the PLC, and the PLC sends it to the host computer, which is then displayed on the touch screen.

[0077] In some specific implementations, the PLC can send a speed control instruction to the frequency converter. After receiving the speed control instruction, the frequency converter controls the speed of the motor 600 according to the speed control instruction, thereby ensuring that the screw extruder 400 stably outputs the molten body to the spinning production line.

[0078] In some of the above-mentioned embodiments, during the implementation of the present application, there is still the problem of how to accurately control the motor speed of the screw extruder according to the pre-established current-extrusion amount relationship to achieve a stable material extrusion amount.

[0079] In this regard, the present application further proposes obtaining the extrusion amount of the first material required for current production; determining the target current value from the current-extrusion amount relationship based on the extrusion amount of the first material; controlling the speed of the motor that drives the screw in the screw extruder to keep the first current close to the target current value and remain stable after reaching the target current value.

[0080] This solution converts the extrusion volume, which is difficult to measure directly, into a current parameter that is easy to measure and control by establishing a current-extrusion volume relationship. The current is adjusted by precisely controlling the motor speed, thereby achieving stable control of the extrusion volume. This method avoids the difficulty of directly measuring the extrusion volume or pressure, while taking into account the impact of factors such as screw wear on the extrusion process. It can control the extrusion volume more accurately, improving the stability of the extrusion process and product quality.

[0081] The core of this application is to use the motor current as an indirect indicator of the extrusion amount. First, an accurate current-extrusion amount relationship needs to be established. This can be done by fitting experimental data or deriving theoretical models, taking into account changes under different working conditions, such as the influence of different materials, different temperatures and other factors. For example, a variety of commonly used plastic materials (such as PE, PP, PVC, etc.) can be tested under different temperature conditions (such as 180°C, 200°C, 220°C) to establish a comprehensive current-extrusion amount relationship database.

[0082] The first current of the motor can be obtained by adding a high-precision current detection device to the motor drive circuit. To improve the measurement accuracy, the method of taking the average value of multiple samplings can be adopted, or a digital filtering algorithm can be used to eliminate the influence of noise. For example, the current value can be taken as the current value by sampling 100 times per second and taking the average value of 10 times to reduce the influence of instantaneous fluctuations.

[0083] The motor speed can be controlled by a frequency converter or other high-performance motor drive device. The control algorithm can be PID control, fuzzy control or other advanced control algorithms, and the most suitable control method can be selected according to the actual situation. For example, an adaptive PID control algorithm can be used to dynamically adjust the PID parameters according to the size of the current deviation to achieve a balance between fast response and stable control.

[0084] A key advantage of the present application is that it can effectively deal with the impact of screw wear. As the screw wears, the traditional fixed speed control method will cause the extrusion volume to gradually decrease. The present application maintains a stable current by adjusting the motor speed, thereby indirectly maintaining a stable extrusion volume. This dynamic adjustment capability makes the present solution show better stability and adaptability in long-term operation.

[0085] In a specific embodiment, the present application scheme is applied to the control of a screw extruder of a polyester fiber production line. First, a large amount of experimental data is used to establish the current-extrusion volume relationship of polyester materials under different temperature and pressure conditions. A high-precision Hall current sensor is installed in the motor drive circuit of the screw extruder to monitor the first current of the motor in real time. The control system sets the target extrusion volume according to production requirements and determines the corresponding target current value through the current-extrusion volume relationship. The system adopts an adaptive PID control algorithm to adjust the motor speed in real time through the frequency converter so that the actual first current approaches and eventually reaches the target current value. When the actual first current reaches the target current value, the control system keeps the speed unchanged, thereby maintaining a stable extrusion volume.

[0086] In some of the above-mentioned embodiments, during the implementation of the present application, there is still the problem of how to accurately control the motor speed during the operation of the screw extruder to maintain current stability and achieve the target extrusion volume while avoiding motor overload.

[0087] In this regard, the present application further proposes that when the first current is greater than the target current value, the speed of the motor that drives the screw to rotate in the screw extruder is controlled to decrease, and after the first current reaches the target current value, the corresponding target speed is obtained, and the target speed is kept constant; when the first current is less than the target current value, the speed of the motor that drives the screw to rotate in the screw extruder is controlled to increase, and after the first current reaches the target current value, the corresponding target speed is obtained, and the target speed is kept constant; when the first current is greater than the target current value and exceeds a first preset value, the motor that drives the screw to rotate in the screw extruder is controlled to stop running; when the first current is less than the target current value and less than a second preset value, a technical solution is provided to control the speed of the motor that drives the screw to rotate in the screw extruder to decrease to the set speed within a specified time.

[0088] The scheme dynamically adjusts the motor speed by monitoring the first current of the motor in real time and comparing it with the target current value to achieve stable control of the first current. Specifically: when the first current is greater than the target current value, the first current is reduced by reducing the motor speed until the target current value is reached; when the first current is less than the target current value, the first current is increased by increasing the motor speed until the target current value is reached. This two-way adjustment mechanism can quickly respond to current changes and keep the first current stable near the target current value. Once the first current reaches the target current value, the system records the motor speed at this time as the target speed and keeps the speed constant. This method can avoid fluctuations caused by frequent speed regulation while ensuring the stability of the extrusion volume. In addition, the scheme also sets a current upper limit threshold (first preset value). When the first current exceeds the threshold, the motor will stop running immediately to prevent the motor from being overloaded and damaged. This is an important safety protection measure.

[0089] When the first current is less than the target current value and less than the second preset value, the speed of the motor driving the screw in the screw extruder is controlled to decrease to the set speed within a specified time;

[0090] Among them, the second preset value is determined according to the on-site process. When there is no material in the screw, the screw will idle. In this case, although the first current value is small, its idling speed is too fast, which can easily cause damage to the internal screw ribs and accelerate the wear of the screw. Therefore, it needs to be reduced to the set speed.

[0091] For example, the second preset value is 180A. When the screw current is continuously less than 180A (in some embodiments, its duration can also be detected, such as 10S), the screw speed is triggered to gradually decelerate to 10 revolutions within 5S. The above parameters can be specifically set in the control interface.

[0092] In a specific embodiment, the present application scheme first establishes the current-extrusion volume relationship through a large amount of experimental data, taking into account the influence of factors such as different temperatures and different raw materials. A high-precision current detection device is installed in the motor drive circuit of the screw extruder, and a sampling frequency of 10kHz is used to monitor the motor current in real time, and a sliding average filter algorithm is used to eliminate the influence of noise.

[0093] The control system obtains the material extrusion amount required for the current production and determines the target current value based on the pre-established current-extrusion amount relationship. Assume that the target current value is 240A and the first preset value (current upper limit threshold) is 280A. The control system adjusts the motor speed through the inverter so that the actual first current approaches and eventually reaches the target current value. When the actual current reaches 240A, the control system records the motor speed at this time as the target speed and keeps the speed unchanged, thereby maintaining a stable extrusion amount.

[0094] If the current detected is more than 240A but less than 280A, the system will reduce the motor speed. The speed reduction adopts the PID control algorithm, and the PID parameters are dynamically adjusted according to the deviation between the current first current and the target current value to achieve fast response and stable control. If the first current is less than 240A, the system will increase the motor speed, also using the PID control algorithm. If the first current exceeds 280A, the system immediately stops the motor operation and triggers an alarm signal to prompt the operator to check the equipment status.

[0095] In this way, the screw extruder of the polyester fiber production line can maintain a stable extrusion volume and maintain good control even when the screw is slightly worn. At the same time, the motor overload protection mechanism effectively prevents equipment damage and improves the safety and reliability of the production line.

[0096] In addition, since the relationship between current and extrusion volume is closer to linear, compared with the nonlinear relationship between pressure and extrusion volume, this scheme can achieve more precise control.

[0097] In some of the above embodiments, during the implementation of the present application, there is still a problem of how to more accurately and smoothly control the speed change of the screw extruder motor to achieve the first current being stable at the target current value and avoid large fluctuations.

[0098] In this regard, the present application further proposes that the step of controlling the speed of the motor that drives the screw to rotate in the screw extruder to decrease includes: controlling the speed of the motor that drives the screw to rotate in the screw extruder to decrease according to the set first deceleration time, the first deceleration frequency and the first deceleration size; the step of controlling the speed of the motor that drives the screw to rotate in the screw extruder to increase includes: controlling the speed of the motor that drives the screw to rotate in the screw extruder to increase according to the set first acceleration time, the first acceleration frequency and the first acceleration size.

[0099] The technical solution introduces the parameters of the first deceleration time, the first deceleration frequency, the first deceleration magnitude, the first acceleration time, the first acceleration frequency and the first acceleration magnitude to control the change of the motor speed. The introduction of these parameters makes the adjustment of the motor speed more precise, smooth and controllable. By setting the above parameters, the system can control the change process of the motor speed more finely and smoothly. This fine control helps to avoid violent fluctuations in the speed adjustment process, so that the first current can smoothly approach and finally stabilize at the target current value.

[0100] The present application controls the change of motor speed by introducing time and frequency parameters, thereby achieving more refined and smooth speed adjustment. Specifically, when the speed needs to be reduced, the system will gradually reduce the speed according to the preset first deceleration time, the first deceleration frequency, and the first deceleration size. This gradual adjustment method avoids sudden and large changes in speed and helps to reduce drastic fluctuations in current. Similarly, when the speed needs to be increased, the system will gradually increase the speed according to the preset first acceleration time, the first acceleration frequency, and the first acceleration size.

[0101] Compared with simple linear speed regulation or step speed regulation, this time and frequency-based speed regulation method can better adapt to the speed regulation requirements under different working conditions. For example, under different material viscosities or temperature conditions, these parameters can be adjusted to achieve the best speed change curve, thereby ensuring the stability of current. In addition, this method may also help reduce the mechanical stress of the motor and extend the life of the equipment.

[0102] It is worth noting that the scheme of the present application forms a closed-loop control system with the aforementioned method based on current to control the speed. The control based on the current-extrusion amount relationship determines the direction and amplitude of the speed that needs to be adjusted, while the present scheme determines how to achieve this speed adjustment. This combination can not only accurately control the extrusion amount, but also ensure the stability of the control process, effectively avoiding oscillation or overshoot that may occur during the control process.

[0103] In a specific embodiment, the control system detects that the current first current is higher than the target current value and the motor speed needs to be reduced. The system sets the first deceleration time to 5 seconds and the first deceleration frequency to 50r / s. This means that the system will reduce the motor by 50 revolutions per second within 5 seconds to achieve a smooth deceleration process, and the first deceleration size is 250 revolutions. On the contrary, if the speed needs to be increased, the system may set the first acceleration time to 3 seconds and the first acceleration frequency to 50r / s to achieve a faster but still smooth acceleration process, and the first acceleration size is 150 revolutions. Through this fine control, the system can respond quickly to current changes while avoiding drastic speed fluctuations, thereby maintaining stable extrusion volume and product quality.

[0104] The solution of the present application achieves fine control of the speed change process by introducing time and frequency parameters. This method can not only adapt to different process conditions, but also effectively reduce fluctuations in the control process and improve the stability of the extrusion volume. Especially in scenarios that require strict and stable extrusion volume, such as polyester fiber production, the solution of the present application can significantly improve the consistency of product quality and reduce product defects caused by fluctuations in extrusion volume. At the same time, since drastic speed changes are avoided, it may also extend the service life of the equipment and reduce maintenance costs.

[0105] In some of the above embodiments, during the implementation of the present application, there is still the problem of how to select appropriate deceleration or acceleration parameters to control the motor speed according to the difference between the current current and the target current value to achieve more precise, smooth and efficient closed-loop control.

[0106] In this regard, the present application further proposes a step of controlling the speed of the motor that drives the screw to rotate in the screw extruder to decrease according to the set first deceleration time, the first deceleration frequency and the first deceleration size, including: calculating the first difference between the current first current and the target current value; selecting the set first deceleration time, the first deceleration frequency and the first deceleration size according to the first difference to control the speed of the motor that drives the screw to rotate in the screw extruder to decrease; the step of controlling the speed of the motor that drives the screw to rotate in the screw extruder to increase according to the set first acceleration time, the first acceleration frequency and the first acceleration size includes: calculating the second difference between the current first current and the target current value; selecting the set first acceleration time, the first acceleration frequency and the first acceleration size according to the second difference to control the speed of the motor that drives the screw to rotate in the screw extruder to increase.

[0107] The scheme controls the motor speed by calculating the difference between the current current and the target current value, and selecting the appropriate deceleration or acceleration parameters according to the difference. This method can adjust the motor speed more accurately and smoothly, thereby achieving more stable extrusion control. Specifically, when deceleration is required, the first difference between the current current and the target current value is first calculated, and then the appropriate first deceleration time, first deceleration frequency and first deceleration size are selected according to this first difference. In this way, the deceleration amplitude can be adjusted according to the size of the deviation to avoid over-adjustment or under-adjustment. Similarly, when acceleration is required, a similar method is also used to select the appropriate first acceleration time, first acceleration frequency and first acceleration size according to the second difference. This difference-based parameter selection method is the key technical feature of the scheme. It can achieve more precise and dynamic speed regulation, and can better adapt to different working conditions and current deviations compared to the fixed parameter adjustment method.

[0108] The core of this embodiment is to dynamically select deceleration or acceleration parameters based on the difference. This method can be implemented in a variety of ways. For example, a series of predetermined deceleration and acceleration parameter combinations can be set, and each set of parameters corresponds to a current difference range. After calculating the current difference, the system will select the most suitable parameter combination. Another implementation method is to use a continuous function relationship to directly calculate the optimal deceleration or acceleration parameters based on the current difference.

[0109] The deceleration and acceleration processes are interrelated. When the system detects that the current deviates from the target current value, it first decides whether to decelerate or accelerate based on the direction of the deviation. Then, the corresponding parameters are selected based on the size of the deviation. This approach not only takes into account the current state, but also implicitly considers the changing trend of the system, thereby achieving a smoother control process.

[0110] In practical applications, multiple current difference thresholds can be set, such as ±1A, ±5A, ±10A, etc. Each threshold corresponds to a different deceleration or acceleration parameter. When the current difference is within ±1A, a smaller adjustment range can be used; when the difference exceeds ±10A, a more aggressive adjustment strategy is used to quickly respond to large deviations.

[0111] This difference-based dynamic parameter selection method is combined with the aforementioned current-extrusion relationship control to form a complete closed-loop control system. The current-extrusion relationship provides the overall control target, while the dynamic parameter selection optimizes the process of achieving the target. This combination not only improves control accuracy, but also enhances the robustness and adaptability of the system.

[0112] For example, when the current is detected to be higher than the target current value of 5A, the system selects the deceleration parameters: the first deceleration time is 2 seconds, the first deceleration frequency is 50r / s, and the first deceleration size is 100 turns. On the contrary, if the current is lower than the target current value of 3A, the system selects the acceleration parameters: the first acceleration time is 1.5 seconds, the first acceleration frequency is 20r / s, and the first acceleration size is 30 turns. These parameters are obtained based on actual production experience and multiple test optimizations, and can be adjusted according to specific equipment and production needs.

[0113] In this way, the system can respond quickly to current changes while avoiding over-adjustment. In actual production, this fine control can control the fluctuation of extrusion volume within a very small deviation, significantly improving the consistency of product quality.

[0114] Compared with the fixed parameter control method, the dynamic parameter selection method of the present application has obvious advantages. Traditional methods usually use fixed PID parameters or preset speed control curves, which are difficult to adapt to the needs under different working conditions. For example, in the early and late stages of screw wear, the same current deviation may require different adjustment strategies. The method of the present application can select the most appropriate parameters based on the deviation value calculated in real time, thereby achieving more precise and flexible control.

[0115] In general, the difference-based dynamic parameter selection method proposed in this application, combined with the current-extrusion amount relationship control, forms an efficient, accurate and adaptable closed-loop control system. This method not only improves the stability of the extrusion amount, but also enhances the system's ability to adapt to changes in various working conditions, thereby effectively improving the stability of the extrusion process and product quality.

[0116] In some of the above-mentioned embodiments, during the implementation of the present application, there is still a problem of how to more accurately control the rotation speed of the motor that drives the screw in the screw extruder to keep the current stable and achieve precise control of the extrusion amount.

[0117] In this regard, the present application further proposes to control the speed of the motor driving the screw in the screw extruder by specifically adopting a PID control method.

[0118] This solution introduces the PID control method to control the speed of the screw extruder motor. PID control is a closed-loop feedback control algorithm that can accurately control the system based on the deviation between the set value and the actual value through the combined action of the three links of proportion, integration and differentiation. In this technical solution, the goal of PID control is to keep the first current stable. By adjusting the motor speed, the PID controller can respond to changes in current in real time and quickly and smoothly adjust the first current to the target current value. Compared with simple open-loop control or single proportional control, this method can better handle the dynamic characteristics and external interference of the system, thereby achieving more accurate extrusion volume control.

[0119] The PID control method used in this application can be implemented specifically through the following steps: First, set the target current value, which is usually determined based on the expected extrusion volume. Then, monitor the actual first current of the motor in real time. The PID controller calculates the motor speed that needs to be adjusted based on the deviation between the target current value and the first current. In this process, the proportional term is used to quickly respond to the deviation, the integral term is used to eliminate the steady-state error, and the differential term is used to suppress overshoot and oscillation.

[0120] PID controller parameter adjustment is key. The optimal proportional, integral, and differential coefficients can be determined by experiment or simulation. The selection of these parameters requires a balance between response speed and stability. For example, during the start-up phase of a screw extruder, a larger proportional coefficient may be required to quickly reach the target current value; while during the steady-state operation phase, a smaller proportional coefficient and a larger integral coefficient may be required to maintain a stable state.

[0121] In addition, considering the complexity of the working environment of the screw extruder, an adaptive PID control strategy can be introduced. This strategy can automatically adjust the PID parameters according to the changes in the system response. For example, when it is detected that the screw wear causes the system characteristics to change, the controller can automatically adjust the parameters to maintain the best control effect.

[0122] The present application scheme can also combine fuzzy control theory to construct a fuzzy PID controller. This controller can better handle nonlinear and time-varying characteristics and adapt to control requirements under different working conditions. For example, the PID parameters can be dynamically adjusted according to the size and change rate of the current deviation to achieve more precise control.

[0123] In a specific embodiment, the PID control method of the present application is applied to a screw extruder for producing polyester fibers. First, the optimal PID parameters are determined by experiments: proportional coefficient Kp=0.5, integral coefficient Ki=0.1, differential coefficient Kd=0.05. The control system samples the first current of the motor every 100 milliseconds and calculates the deviation from the target current value. The PID controller calculates the motor speed that needs to be adjusted based on the deviation, and adjusts the motor speed in real time through the frequency converter.

[0124] In actual operation, when the first current is detected to increase suddenly by more than 20% of the target current value, the system will immediately increase the Kp value to 0.8 to quickly respond to this sudden change. At the same time, the system will check whether this sudden change lasts. If it lasts for more than 5 seconds, it is judged that a blockage may have occurred, and the system will automatically reduce the speed or shut down to prevent equipment damage.

[0125] By adopting the PID control method, the present application scheme has significant advantages over the traditional fixed speed control method. First, PID control can respond to system changes in real time and quickly adjust the motor speed to keep the first current near the target current value. This dynamic adjustment capability enables the system to effectively cope with the impact of factors such as screw wear and changes in material properties, and maintain a stable extrusion volume.

[0126] Secondly, the PID control method has self-correction capabilities. Through the integral action, it can gradually eliminate the steady-state error of the system, which is impossible to achieve with simple proportional control. This means that even after long-term operation, the system can still maintain high-precision control effects, which is particularly important for processes such as spinning that require long-term continuous production.

[0127] Furthermore, the differential effect of PID control can predict the changing trend of the system and make adjustments in advance, thereby reducing the fluctuation and oscillation of the system. This is crucial to maintain the stability of the extrusion volume and can significantly improve the consistency of product quality.

[0128] Compared with the closed-loop control method based on pressure sensor, the PID control scheme of this application avoids the use of pressure sensors that are susceptible to contamination and wear, and improves the reliability and maintainability of the system. At the same time, since the relationship between current and extrusion volume is closer to linear, compared with the nonlinear relationship between pressure and extrusion volume, this scheme can achieve more precise control.

[0129] In addition, the PID control scheme of the present application has stronger adaptability and flexibility. By adjusting the PID parameters, it can easily adapt to different material and process requirements without replacing or adjusting the hardware equipment. This software-level adjustability greatly improves the versatility and economy of the system.

[0130] In general, the PID control method proposed in this application stabilizes the current by accurately controlling the motor speed, thereby achieving accurate control of the extrusion volume, effectively solving the problem of unstable extrusion volume caused by factors such as screw wear, and providing a new technical means for improving the quality and efficiency of plastic extrusion processing. This method not only improves product quality, but also reduces production costs, improves the reliability and service life of equipment, and makes an important contribution to the technological progress of the plastic extrusion industry.

[0131] In some of the above-mentioned embodiments, during the implementation of the present application, there is still the problem of how to improve the accuracy and adaptability of PID control so that it can better adapt to the changes that may occur in the screw extruder during long-term use.

[0132] In this regard, the present application further proposes a technical solution of collecting first data of a first current and a corresponding rotational speed; establishing a current-speed model based on the first data; and adjusting PID parameters according to the current-speed model when performing PID control.

[0133] This technical solution improves the accuracy and adaptability of PID control by collecting first data, building models and dynamically adjusting parameters. Collecting first current and speed data provides a basis for modeling, building a current-speed model reflects the actual relationship between the two, and adjusting PID parameters according to the model enables control to adapt to changes in actual conditions. These features work together to improve the performance of the control system.

[0134] When implementing it, you first need to design a data acquisition system. You can use high-precision current sensors and speed encoders to improve data reliability by taking the average value through multiple sampling. To establish a current-speed model, you can use methods such as polynomial fitting and neural networks, and you need to consider changes under different working conditions. In the PID control process, you can dynamically adjust the three parameters of proportion, integration, and differentiation according to the model characteristics near the current working point.

[0135] This method can not only adapt to the long-term changes caused by screw wear, but also cope with short-term changes such as raw material characteristics and ambient temperature. For example, when the screw wear causes the first current to decrease at the same speed, the model will reflect this change, and the PID parameters will be adjusted accordingly to maintain a stable extrusion volume. At the same time, this adaptive mechanism can also cope with the processing requirements of different materials, improving the versatility of the system.

[0136] In a specific embodiment, the present application is applied to the control of a screw extruder of a polyester fiber production line. The system collects the first current and speed data every 10 minutes, and uses the data of the last 24 hours to establish a current-speed model. The model adopts a cubic polynomial fit, and temperature is considered as an additional variable. The parameter adjustment of the PID controller adopts fuzzy rules, and the three parameters of proportion, integration, and differentiation are adjusted according to the slope and curvature of the model at the current working point.

[0137] Compared with traditional fixed parameter PID control, the scheme of this application has significant advantages. Traditional methods require manual debugging of PID parameters, which is difficult to adapt to changes in equipment and processes. However, this application enables the control system to maintain good performance continuously through real-time modeling and adaptive adjustment. This not only improves product quality, but also reduces manual intervention, reduces operational difficulty and the risk of human error.

[0138] In addition, compared with closed-loop control based on pressure sensors, this application avoids the problem that pressure sensors are susceptible to contamination and wear, and improves system reliability. At the same time, since the relationship between current and extrusion volume is closer to linear, compared with the nonlinear relationship between pressure and extrusion volume, this solution can achieve more precise control. This is particularly important for the production of polyester fibers that require strict and stable extrusion volume, which can effectively reduce product specification fluctuations and improve the yield rate.

[0139] In general, this application achieves more precise control of the screw extruder by establishing a current-speed model and dynamically adjusting PID parameters. This method can effectively cope with the impact of factors such as equipment wear and raw material changes, ensure the stability of extrusion volume, and thus improve product quality and production efficiency.

[0140] Second, refer to Figure 2 The present application also proposes an extrusion screw closed-loop control device, including an acquisition module 210 and a control module 220. The acquisition module 210 is used to acquire a first current of a motor that drives the screw to rotate during operation of the screw extruder; the control module 220 is used to control the speed of the motor that drives the screw to rotate in the screw extruder according to a pre-established current-extrusion amount relationship, so that the first current remains stable.

[0141] By obtaining the first current of the motor that drives the screw to rotate during the operation of the screw extruder, and controlling the speed of the motor that drives the screw to rotate in the screw extruder according to the pre-established current-extrusion amount relationship, the first current is kept stable, thereby achieving precise control of the extrusion amount, being able to adapt to the influence of factors such as screw wear, and improving the extrusion amount control accuracy, while avoiding the use of pressure sensors and reducing maintenance costs. It has the advantages of being able to adapt to the influence of factors such as screw wear, improving the extrusion amount control accuracy, and reducing maintenance costs.

[0142] In addition, in some preferred embodiments, an extrusion screw closed-loop control device proposed in the present application can perform any one of the steps in the above method.

[0143] Thirdly, refer to Figure 3 The present application also provides an electronic device, including a processor 310 and a memory 320, wherein the memory 320 stores computer-readable instructions. When the computer-readable instructions are executed by the processor, the steps in the above method are executed.

[0144] Through the above technical solution, the processor 310 and the memory 320 are interconnected and communicate with each other through a communication bus and / or other forms of connection mechanisms (not marked), and the memory 320 stores computer-readable instructions executable by the processor 310. When the electronic device is running, the processor 310 executes the computer-readable instructions to execute the method in any optional implementation of the above embodiment to achieve the following functions: obtaining a first current of the motor that drives the screw to rotate during the operation of the screw extruder; controlling the speed of the motor that drives the screw to rotate in the screw extruder according to a pre-established current-extrusion amount relationship to keep the first current stable.

[0145] In a fourth aspect, the present application also provides a storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps in the above method are executed.

[0146] Through the above technical solution, when the computer program is executed by the processor, the method in any optional implementation method of the above embodiment is executed to achieve the following functions: obtaining the first current of the motor that drives the screw to rotate during the operation of the screw extruder; according to the pre-established current-extrusion amount relationship, controlling the speed of the motor that drives the screw to rotate in the screw extruder to keep the first current stable.

[0147] Among them, the computer-readable storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable red-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, magnetic disk or optical disk.

[0148] In the embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are merely schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some communication interfaces, and the indirect coupling or communication connection of devices or units can be electrical, mechanical or other forms.

[0149] In addition, the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, and may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0150] Furthermore, the functional modules in the various embodiments of the present application may be integrated together to form an independent part, or each module may exist separately, or two or more modules may be integrated to form an independent part.

[0151] The above description is only an embodiment of the present application and is not intended to limit the protection scope of the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A closed-loop control method for an extrusion screw, characterized in that: include: Obtaining a first current of a motor that drives a screw to rotate during operation of the screw extruder; According to the pre-established current-extrusion volume relationship, the speed of the motor driving the screw in the screw extruder is controlled to keep the first current stable, and the extrusion volume is indirectly kept stable by keeping the current stable; The step of controlling the rotation speed of the motor driving the screw in the screw extruder according to the pre-established current-extrusion amount relationship to keep the first current stable comprises: Obtain the extrusion amount of the first material required for current production; According to the extrusion amount of the first material, determining a target current value from the current-extrusion amount relationship; Controlling the rotation speed of the motor driving the screw in the screw extruder so that the first current remains close to the target current value and remains stable after reaching the target current value; Regularly collect data of the first current and the corresponding rotation speed, and update the relationship between the current and the extrusion amount; When the screw extruder is initially operated, the relationship between the current and the extrusion volume is obtained to determine the current degree of wear of the screw, and the corresponding current-extrusion volume relationship is selected according to the current degree of wear of the screw.

2. The closed-loop control method for an extrusion screw according to claim 1, characterized in that: The step of keeping the first current close to the target current value and keeping the first current stable after reaching the target current value comprises: When the first current is greater than the target current value, the speed of the motor driving the screw in the screw extruder is controlled to decrease, and after the first current reaches the target current value, the corresponding target speed is obtained, and the target speed is kept constant; When the first current is less than the target current value, the speed of the motor driving the screw in the screw extruder is controlled to increase, and after the first current reaches the target current value, the corresponding target speed is obtained, and the target speed is kept constant; Also includes: When the first current is greater than the target current value and exceeds a first preset value, controlling the motor driving the screw in the screw extruder to stop running; When the first current is less than the target current value and less than a second preset value, the speed of the motor driving the screw in the screw extruder is controlled to decrease to a set speed within a specified time.

3. The extrusion screw closed-loop control method according to claim 2, characterized in that: The step of controlling the speed of the motor driving the screw in the screw extruder to decrease comprises: Controlling the speed of the motor driving the screw in the screw extruder to decrease according to the set first deceleration time, first deceleration frequency and first deceleration magnitude; The step of controlling the speed of the motor driving the screw in the screw extruder to increase includes: The rotation speed of the motor driving the screw in the screw extruder is increased according to the set first acceleration time, first acceleration frequency and first acceleration magnitude.

4. The closed-loop control method for an extrusion screw according to claim 3, characterized in that: The step of controlling the speed of the motor driving the screw in the screw extruder to decrease according to the set first deceleration time, the first deceleration frequency and the first deceleration magnitude comprises: Calculating a first difference between the first current and the target current value; The first deceleration time, the first deceleration frequency and the first deceleration magnitude are selected and set according to the first difference value to control the speed of the motor driving the screw in the screw extruder to decrease; The step of controlling the speed of the motor driving the screw in the screw extruder to increase according to the set first acceleration time, first acceleration frequency and first acceleration magnitude comprises: Calculating a second difference between the first current and the target current value; The first acceleration time, the first acceleration frequency and the first acceleration magnitude are selected and set according to the second difference to control the speed of the motor driving the screw in the screw extruder to increase.

5. The closed-loop control method for an extrusion screw according to claim 1, characterized in that: The speed of the motor driving the screw in the screw extruder is controlled by PID control.

6. The closed-loop control method for an extrusion screw according to claim 5, characterized in that: Also includes: Collecting first data of the first current and the corresponding rotation speed; Establishing a current-speed model according to the first data; When performing PID control, PID parameters are adjusted according to the current-speed model.

7. An extrusion screw closed-loop control device, characterized in that: include: An acquisition module, used for acquiring a first current of a motor that drives a screw to rotate during operation of the screw extruder; A control module, for controlling the speed of a motor driving a screw in the screw extruder according to a pre-established current-extrusion volume relationship, so as to keep the first current stable, and indirectly keep the extrusion volume stable by keeping the current stable; The step of controlling the rotation speed of the motor driving the screw in the screw extruder according to the pre-established current-extrusion amount relationship to keep the first current stable comprises: Obtain the extrusion amount of the first material required for current production; According to the extrusion amount of the first material, determining a target current value from the current-extrusion amount relationship; Controlling the rotation speed of the motor driving the screw in the screw extruder so that the first current remains close to the target current value and remains stable after reaching the target current value; Regularly collect data of the first current and the corresponding rotation speed, and update the relationship between the current and the extrusion amount; When the screw extruder is initially operated, the relationship between the current and the extrusion volume is obtained to determine the current degree of wear of the screw, and the corresponding current-extrusion volume relationship is selected according to the current degree of wear of the screw.

8. An electronic device, characterized in that: The method comprises a processor and a memory, wherein the memory stores computer-readable instructions, and when the computer-readable instructions are executed by the processor, the steps in the method according to any one of claims 1 to 6 are executed.

9. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are executed.

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