Stretching process control system suitable for synchronous biaxial stretching BOPP film

Abstract

The present application relates to the technical field of polymer material processing and film stretching control, in particular to a stretching process control system suitable for synchronous bidirectional stretching BOPP film, comprising double-source temperature acquisition, temperature fusion, temperature difference judgment, temperature prediction and partition temperature control modules: the ambient temperature of the stretching area and the surface temperature of the film are synchronously acquired, and after time alignment and position correspondence, they are fused into full-width comprehensive temperature distribution; accordingly, the edge area and the middle area are divided, the temperature deviation and the change rate of the middle area are output, and the subsequent temperature change of the middle area is predicted in combination with the inlet thickness distribution, the stretching speed, the stretching tension and the polypropylene equivalent rheological parameters; then the edge area hot air circulating heater, the cooling baffle and the middle area infrared radiation compensator are linked to carry out closed-loop correction, so as to reduce the transverse temperature difference and the roughness unevenness caused by insufficient temperature in the middle area.

Description

Technical Field

[0001] This invention relates to the field of polymer material processing and film stretching control technology, specifically a stretching process control system applicable to synchronous biaxially stretched BOPP films. Background Technology

[0002] In the production process of biaxially oriented polypropylene capacitor film, its application scenarios are not limited to capacitor film, but can also be widely used in composite current collector film, packaging film, optical film, etc. The film needs to maintain transverse temperature consistency that meets the preset consistency threshold in the stretching zone. The temperature state of the stretching zone will directly affect the heating uniformity of the film and the subsequent surface structure stability. The temperature control effect depends on the accurate acquisition and coordinated adjustment of the ambient temperature of the stretching zone and the actual temperature of the film surface. In traditional methods, temperature control in the stretching zone often relies on a single temperature acquisition method or an integrated temperature control structure. This makes it difficult to simultaneously consider the thermal field distribution inside the oven and the actual heating state of the film surface during operation. When there are differences in sampling frequency, response speed, and spatial location, it is easy to cause inaccurate judgment of transverse temperature. Consequently, it is difficult to correct the phenomenon that the temperature in the middle area is lower than the set threshold and the temperature in the edge area is higher than the set threshold in a timely manner. The transverse temperature difference of the film exceeds the preset allowable range, and the production stability still does not meet the process standard requirements. Summary of the Invention

[0003] The purpose of this invention is to provide a stretching process control system suitable for synchronous biaxially stretched BOPP films, which can accurately acquire and coordinately adjust the ambient temperature of the stretching zone and the actual heating state of the film surface, effectively reducing the transverse temperature difference of the film and maintaining... crystal orientation The temperature conditions required for crystal transformation are determined, and the roughness unevenness in the intermediate region caused by insufficient temperature and the subsequent increase in the amount of trimming are reduced, thereby improving the production stability of the capacitor film base film.

[0004] The objective of this invention can be achieved through the following technical solutions: The dual-source temperature acquisition module is used to acquire the ambient temperature of the stretching zone and the surface temperature of the film. After unifying them to the same time reference and the same horizontal coordinate system, time alignment and position correspondence are performed, and the corresponding temperature data is output. The temperature fusion module is used to fuse the corresponding temperature data to form a comprehensive temperature distribution across the entire thin film and output the temperature results for each horizontal zone. The temperature difference judgment module is used to divide the film into edge and middle regions in the horizontal direction according to the temperature results of each horizontal zone, determine the temperature difference between the two regions, and output the temperature deviation and temperature change rate of the middle region. The temperature prediction module combines comprehensive temperature distribution, film inlet thickness distribution, stretching speed, stretching tension, equivalent rheological parameters of polypropylene, and temperature change rate to predict and output the predicted temperature and temperature change trend of the intermediate zone. The control system also includes a hot air circulation heater, a cooling baffle, and an infrared radiation compensator; the zone temperature control module connects the hot air circulation heater and cooling baffle located in the edge zone and the infrared radiation compensator located in the middle zone, and is used to control the hot air circulation heater, cooling baffle, and infrared radiation compensator according to the temperature deviation, temperature change rate, predicted temperature, and temperature change trend, and uses the corresponding temperature data collected by the dual-source temperature acquisition module and processed by time alignment and position correspondence as the feedback temperature correction and adjustment output.

[0005] Preferably, the dual-source temperature acquisition module includes a contact temperature sensor array and an infrared scanning unit. The contact temperature sensor array is set above and below the synchronous biaxial stretching zone and is arranged along the longitudinal and transverse directions to acquire the two-dimensional ambient temperature distribution within the stretching zone. An infrared scanning unit is located at the top of the stretching zone to continuously scan the surface of the film during operation and output the two-dimensional temperature distribution of the film surface.

[0006] As a preferred embodiment, the dual-source temperature acquisition module maps the ambient temperature and the thin film surface temperature to the same time reference and the same horizontal coordinate system, and sends the processed temperature data of the two types to the temperature fusion module.

[0007] Preferably, the temperature fusion module is used to weight and fuse the ambient temperature and the film surface temperature according to preset weights to form a comprehensive temperature distribution, and adjust the preset weights according to the stretching speed, surface vibration amplitude and sensor reliability. The sensor reliability is determined by a weighting coefficient based on the consistency between the ambient temperature and the film surface temperature at the same location, the sensor signal-to-noise ratio, and the stability of continuous sampling; the surface jitter amplitude is obtained by a set ranging sensor, representing the displacement change amplitude of the film surface relative to a preset reference position.

[0008] Preferably, the temperature difference judgment module divides the film laterally into an edge region and a middle region to compare the temperature difference between the edge region and the middle region, and outputs the temperature deviation and temperature change rate of the middle region.

[0009] Preferably, the temperature prediction module is input to the current overall temperature distribution, film inlet thickness distribution, stretching speed, stretching tension, equivalent rheological parameters of polypropylene, and the temperature change rate of the intermediate zone. The temperature prediction module outputs the predicted temperature of the intermediate zone and the temperature change trend indicating heating, cooling, or temperature stabilization.

[0010] Preferably, the temperature prediction module includes a prediction model and a model update unit. The prediction model is constructed based on historical online temperature data and offline roughness detection results. The model update unit is used to update the model parameters according to the deviation between the returned temperature and the prediction results. The returned temperature is the temperature data collected by the dual-source temperature acquisition module and processed by time alignment and location correspondence.

[0011] As a preferred embodiment, the zone temperature control module divides the stretching zone laterally into at least 6 independent control zones, with an infrared radiation compensator installed in the middle zone and a hot air circulation heater and adjustable cooling baffle installed in the edge zone. The zone temperature control module has a built-in process temperature window that meets the requirements of the process temperature window. Crystal melting point is below The crystal melting point was determined, and the compensation trigger value was determined based on the stretching rate, equivalent rheological parameters, and intermediate zone thickness. The temperature gradient exponent in the intermediate zone was also calculated. ; The temperature gradient index is calculated by dividing the absolute value of the difference between the center temperature of the intermediate zone and the average temperature at the edge of the intermediate zone by the lateral width of the intermediate zone.

[0012] Preferably, when the temperature gradient index of the intermediate zone is greater than the compensation trigger value, or when the predicted temperature of the intermediate zone is greater than the compensation trigger value, the temperature gradient index of the intermediate zone is greater than the compensation trigger value. When the absolute value of the difference between the crystal melting point and the safety temperature margin is less than the first preset threshold, the zone temperature control module first sends a compensation command to the middle zone; When the compensation in the middle region causes the temperature in the edge region to be similar to... When the absolute value of the difference in crystal melting points is less than the second preset threshold, the zone temperature control module simultaneously reduces the heating amount of hot air in the edge zone or increases the opening of the cooling baffle; when the compensation in the middle zone causes the temperature in the edge zone to be less than the threshold value, the module will adjust accordingly. When the absolute value of the difference in crystal melting points is greater than or equal to the second preset threshold, the edge region maintains the current control parameters; where the second preset threshold is the safety upper limit difference. When the temperature gradient exponent is less than or equal to the compensation trigger value and the predicted temperature in the middle zone is... When the absolute value of the difference between the crystal melting point and the safety temperature margin is greater than or equal to the first preset threshold, the current control parameters are maintained.

[0013] As a preferred embodiment, after the zone temperature control module issues the adjustment command, it updates the control parameters according to the temperature feedback returned by the dual-source temperature acquisition module. The dual-source temperature acquisition module, temperature fusion module, temperature difference judgment module and temperature prediction module synchronously update the corresponding outputs, and the zone temperature control module executes closed-loop control based on the updated outputs.

[0014] The beneficial effects of this invention are: 1. This invention achieves temperature fusion by using dual-source temperature acquisition, a unified time reference, and lateral coordinate mapping. This transforms the ambient temperature of the stretching zone and the film surface temperature into a full-area temperature result that can be directly used for control, avoiding positional deviations and inaccurate judgments caused by a single temperature measurement method. Furthermore, by combining temperature difference judgment, temperature prediction, and zoned temperature control, the middle and edge regions can be respectively heated, limited, and corrected according to their actual heating conditions, improving lateral temperature consistency and promptly suppressing the problems of low temperatures in the middle region and high temperatures in the edge region. It is particularly suitable for the continuous production of synchronous biaxially stretched polypropylene films, including capacitor films, composite current collector films, packaging films, and optical films, and has the advantages of improving temperature control stability, reducing lateral temperature differences, and reducing subsequent roughness unevenness and increased trimming amount. Attached Figure Description

[0015] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a module architecture diagram of a stretching process control system applicable to synchronous biaxially stretched BOPP film in the embodiments of this application. Detailed Implementation

[0016] The technical solutions of the embodiments 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, and 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.

[0017] Please see Figure 1 A stretching process control system suitable for synchronous biaxially stretched BOPP films, including: The dual-source temperature acquisition module is used to acquire the ambient temperature of the stretching zone and the surface temperature of the film. After unifying them to the same time reference and the same horizontal coordinate system, time alignment and position correspondence are performed, and the corresponding temperature data is output. The temperature fusion module is used to fuse the corresponding temperature data to form a comprehensive temperature distribution across the entire thin film and output the temperature results for each horizontal zone. The temperature difference judgment module is used to divide the thin film into edge regions laterally based on the temperature results of each lateral zone. and the middle area Determine the temperature difference between the two zones and output the intermediate zone. temperature deviation and rate of temperature change ; The temperature prediction module combines comprehensive temperature distribution, film inlet thickness distribution, stretching speed, stretching tension, equivalent rheological parameters of polypropylene, and temperature change rate to predict and output the predicted temperature and temperature change trend of the intermediate zone. The control system also includes a hot air circulation heater, cooling baffles, and an infrared radiation compensator; the zone temperature control module is connected to the edge zone. Hot air circulation heater and cooling baffle and located in the intermediate zone Infrared radiation compensator, used to adjust for temperature deviation Rate of temperature change Predicted temperature The system controls the hot air circulation heater, cooling baffle, and infrared radiation compensator based on temperature change trends, and uses the corresponding temperature data collected by the dual-source temperature acquisition module and processed by time alignment and position correspondence as the feedback temperature correction and adjustment output.

[0018] In the application scenario, after isothermal crystallization, the polypropylene sheet enters the synchronous biaxial stretching zone, and the film runs continuously in the stretching zone. This embodiment provides a method to combine the ambient temperature of the stretching zone and the surface temperature of the film into a full-width temperature result on the same biaxially stretched polypropylene capacitor film base film production line, and to implement heat distribution in the middle area and the edge area accordingly. The dual-source temperature acquisition module consists of a contact temperature sensor array and an infrared scanning unit. The contact temperature sensor array is arranged above and below the synchronous bidirectional stretching zone, and forms a sampling surface covering the stretching zone along the longitudinal and transverse directions to obtain the ambient temperature distribution inside the oven. The infrared scanning unit is located at the top of the stretching zone and continuously scans the surface of the thin film during operation to obtain the two-dimensional temperature distribution of the thin film surface. The two types of data are sampled differently. Ambient temperature reflects thermal field conditions, while film surface temperature reflects the heating result of the material. If they are used directly side by side, positional deviations are likely to occur when judging the lateral partition. Therefore, the dual-source temperature acquisition module first completes the unified mapping. During the unified mapping, the production line control cycle is used as a common time reference, and the lateral width direction of the film is used as a common coordinate reference. The ambient temperature and the thin film surface temperature each have their own sampling markers and lateral position markers. Before entering the temperature fusion module, they undergo time alignment and position correspondence processing. For cases with different sampling frequencies, the most recent valid data within the same control cycle is used for correspondence. For cases where response times differ, the data that has been confirmed to be stable within the current period is used as the valid value for that period; for cases where spatial resolutions differ, data with spatial resolutions greater than the preset resolution threshold are merged according to the horizontal partitioning requirements so that the two types of data ultimately fall into the same horizontal position. The processed temperature data is written into the temperature cache of the current cycle and used as the input of the temperature fusion module. The temperature cache adopts a three-segment sliding window that scrolls according to the control cycle. Data at the same horizontal position is marked as pending confirmation after being written in the current cycle. After the data at the same position arrives in the next cycle and completes alignment, it is converted into a stable state and participates in fusion. If no valid value is obtained at the same position after two consecutive control cycles, the position is marked as a failure state, and the failure is compensated by the stable value of the adjacent position according to the lateral distance coefficient; wherein the lateral distance coefficient is calculated according to the following formula:

[0019] In the formula, For the failure location and the first The lateral physical distance between adjacent stable positions For the failure location and the first The lateral physical distance between adjacent stable positions For the index of adjacent stable positions participating in the summation, The corresponding horizontal distance coefficient is used as the weight for weighted completion to avoid interruption of partitioning judgment due to single-point missing data; The temperature fusion module performs weighted fusion of ambient temperature and film surface temperature according to preset weights to form a comprehensive temperature distribution across the entire film surface, and adjusts the weights based on film running speed, surface jitter amplitude and sensor reliability. The surface jitter amplitude is obtained by a ranging sensor, representing the displacement change amplitude of the thin film surface relative to a preset reference position; the fused comprehensive temperature distribution is output in horizontal partitions and stored in the partition temperature result area for subsequent modules to call. If a local node fails to provide a valid value within a certain control cycle, the stable records of adjacent nodes in the same area will be used to fill the gap. If the infrared scanning unit causes discontinuous sampling in a local area due to surface jitter, the thin film surface temperature will be reduced in weight by a preset reduction ratio while the confirmed valid ambient temperature will be retained. If neither type of data meets the usable condition at the same horizontal position, the combined temperature result at the corresponding position of the previous valid period is maintained and marked as to be corrected. To avoid the feedback temperature correction and the current cycle fusion result from overlapping each other, the system places the current cycle's comprehensive temperature result and the feedback temperature in different control phases, and only replaces the confirmed stable data in the next control cycle, so that the closed-loop correction is always based on the aligned stable temperature sequence. After receiving the temperature results from each horizontal zone, the temperature difference judgment module divides the thin film horizontally into edge zones. and the middle area Compare the temperatures of the two and output the temperature deviation. and rate of temperature change ; The temperature prediction module retrieves the overall temperature distribution and the thin film inlet thickness distribution. , stretching speed Tension Equivalent rheological parameters of polypropylene and the rate of temperature change in the intermediate zone It predicts subsequent temperature changes in the intermediate region and outputs the predicted temperature. and temperature change trends; The zone temperature control module is connected to the hot air circulation heater and cooling baffle in the edge zone, and the infrared radiation compensator in the middle zone. If the temperature in the middle zone is too low and the forecast shows that it will continue to decrease, the infrared radiation compensation amount will be increased. If the temperature in the edge area is too high, reduce the output of the hot air circulation heater or increase the opening of the cooling baffle; after the actuator moves, the dual-source temperature acquisition module continues to collect the temperature and enters the next round of processing to transmit the temperature correction and adjustment output. This implementation method, through the continuous connection of dual-source acquisition, spatiotemporal correspondence, temperature fusion, zone judgment and zone temperature adjustment, enables the temperature deviation in the intermediate region to be identified and transmitted to the actuator within the current control cycle, thereby reducing the unevenness of roughness in the intermediate region caused by insufficient temperature and the increase in subsequent trimming amount.

[0020] In one embodiment, the dual-source temperature acquisition module includes a contact temperature sensor array and an infrared scanning unit. The contact temperature sensor array is disposed above and below the synchronous biaxial stretching zone and is arranged longitudinally and laterally to acquire the two-dimensional ambient temperature distribution within the stretching zone. The specific data acquisition and spatiotemporal mapping process of this implementation method is as described above. In the handling of abnormal data, the same methods are used to avoid interruption of data alignment, such as filling in adjacent nodes, adjusting participation weights, and maintaining the comprehensive temperature results of the previous period. In one embodiment, the dual-source temperature acquisition module maps the ambient temperature and the thin film surface temperature to the same time reference and the same horizontal coordinate system, and sends the processed temperature data of the two types to the temperature fusion module.

[0021] In this implementation, the unified mapping rules for the two types of temperature data and the mechanism for completion and weight adjustment in abnormal situations are consistent with the overall processing logic described above. The processed corresponding temperature data will be written into the temperature cache and sent to the temperature fusion module to execute subsequent algorithms.

[0022] In one embodiment, the temperature fusion module is used to weight and fuse the ambient temperature and the film surface temperature according to a preset weight to form a comprehensive temperature distribution, and adjust the preset weight according to the stretching speed, surface jitter amplitude and sensor reliability. The sensor reliability is determined by a weighting coefficient based on the consistency between the ambient temperature and the film surface temperature at the same location, the sensor signal-to-noise ratio, and the stability of continuous sampling; the surface jitter amplitude is obtained by a set ranging sensor, representing the displacement change amplitude of the film surface relative to a preset reference position.

[0023] In this embodiment, the temperature fusion module performs weighted fusion of ambient temperature and film surface temperature to form a comprehensive temperature distribution across the entire film surface; The fusion weights are not fixed, but are adjusted based on the thin film running speed, surface jitter amplitude, and sensor reliability. In the specific fusion process, the overall temperature is calculated by adding the thin film surface temperature with its weighting coefficient and the ambient temperature with its weighting coefficient, and the sum of the two weighting coefficients is 1. When the thin film operates at a higher speed, the surface temperature change more directly reflects the current heating state, and the system increases the weighting coefficient of the thin film surface temperature proportionally. When the surface vibration amplitude increases, the infrared scanning results may show short-term fluctuations at local locations. The system reduces the weight of the thin film surface temperature according to the preset attenuation rule and transfers the attenuation amount to the weight of the ambient temperature. To avoid the mixing of speed and jitter in terms of dimensions, this implementation method first converts the speed difference and jitter amplitude into dimensionless deviations relative to their respective reference values, and then performs weight correction. Specifically, let the surface temperature weight of the basic thin film be... The reference stretching speed is The reference jitter amplitude is The dynamic weight of surface temperature is determined according to the following formula:

[0024] In the formula, The current stretching speed, Given the current surface jitter amplitude, the truncation function is used to truncate and limit the calculation results to a value within a specified range. and Between; dimensionless correction coefficient and Used to adjust the contribution of deviations in various physical quantities to the weights; Sensor reliability at the current lateral position of the thin film surface temperature channel The value range is 0 to 1; the preset minimum effective weight lower limit and maximum effective weight upper limit are respectively determined by... and express; Correspondingly, ambient temperature weighting Values Velocity variation, surface jitter, and sensor reliability are all incorporated into the correction in a unified dimensionless form to eliminate dimensional conflicts in weight calculation. The reliability of the sensor is determined based on the consistency between the ambient temperature and the film surface temperature at the same location, the sensor signal-to-noise ratio, and the stability of continuous sampling. The specific quantification rules are as follows: The consistency score is given by comparing the absolute value of the temperature difference between the preset reference temperature difference and the temperature difference between the two. When the absolute value of the temperature difference is not greater than the preset reference temperature difference, it is given a full score of 1. When the absolute value of the temperature difference is greater than the preset reference temperature difference, it is given by the ratio of the preset reference temperature difference to the absolute value of the temperature difference. The normalized signal-to-noise ratio (SNR) value is calculated by dividing the currently measured SNR value by the sensor's factory-calibrated maximum SNR, which is 60 dB. The continuous sampling stability score is the percentage of valid sampling times within a set number of control cycles in the past 10 control cycles; the sensor reliability is composed of the consistency score, the normalized signal-to-noise ratio value, and the arithmetic mean of the continuous sampling stability score. When the signal-to-noise ratio or continuous sampling stability is lower than the set safety limit The derating factor is further reduced by a preset derating factor, which ranges from 0.5 to 0.8, thereby reducing the effective weight of the thin film surface temperature in sync and ensuring that the overall temperature distribution does not exhibit false abrupt changes due to surface physical displacement or signal attenuation. The ranging sensor is used to obtain the displacement change amplitude of the thin film surface relative to the preset reference position. This result is used as the surface jitter amplitude to participate in the aforementioned weight correction. The resulting comprehensive temperature distribution and its lateral compensation and abnormal state maintenance strategies when local nodes fail are all executed according to the overall operating rules of the aforementioned system to ensure that stable zone temperature results are continuously provided.

[0025] In one embodiment, the temperature difference determination module divides the thin film laterally into edge regions. and the middle area This is used to compare the temperature difference between the edge region and the middle region, and output the temperature deviation of the middle region. and rate of temperature change .

[0026] In this embodiment, after receiving the lateral partitioning results corresponding to the comprehensive temperature distribution, the temperature difference judgment module divides the thin film laterally into edge regions. and the middle area The edge area The middle area comprises 10% to 20% of the total transverse width of the film on both sides. This represents the remaining central region of the film's total transverse width; After the division, the temperature difference between the edge zone and the middle zone is not calculated only once, but the temperature records of the middle zone for multiple consecutive control cycles are compared to form the temperature deviation for the current cycle. and the rate of temperature change ; Temperature deviation characterizes the degree of deviation of the intermediate zone from the target process zone, while the temperature change rate characterizes the direction and magnitude of change of the intermediate zone in adjacent control cycles. Both are written into the prediction call area for the temperature prediction module to read directly; the zone temperature control module is configured to obtain the comparison results of the current temperature and the preset lower limit, as well as the temperature change trend.

[0027] In one embodiment, the inputs to the temperature prediction module include the current overall temperature distribution and the thin film inlet thickness distribution. , stretching speed Tension Equivalent rheological parameters of polypropylene and the middle area rate of temperature change The temperature prediction module outputs the intermediate zone. Predicted temperature and represent the trend of temperature change, such as rising, falling, or stabilizing.

[0028] When only temperature difference is used for judgment, if the thickness distribution at the film inlet changes, or the stretching speed and stretching tension are adjusted, the temperature change in the middle zone will often be reflected later than that in the edge zone. The temperature prediction module is configured to receive the current overall temperature distribution, film inlet thickness distribution, stretching speed, stretching tension, equivalent rheological parameters of polypropylene, and temperature change rate, and predict subsequent temperature changes in the intermediate zone; the prediction results include the predicted temperature of the intermediate zone. And the trend of temperature change; The temperature change trend is output in the form of heating up, cooling down, or temperature stabilization, so that the control module can directly call the corresponding control logic; for lateral positions with a thickness higher than the preset thickness parameter, the heat transfer and temperature rise rate are usually slower than for positions with a thickness lower than the preset thickness parameter; for working conditions with increased stretching speed, the heating time of the film through the hot zone will change accordingly. For working conditions where tension and equivalent rheological parameters change, the temperature response of the material during the tensile stage will also change; therefore, incorporating the above process parameters and the current temperature distribution into the prediction can make the judgment of subsequent temperature changes in the intermediate zone more consistent with the tensile state. In this embodiment, power, thickness or rheological parameters are not directly added together as original physical quantities. Instead, each input quantity is first converted into a corresponding temperature correction quantity before being included in the prediction, thus avoiding direct mixing of physical quantities with different dimensions. The temperature prediction module uses the current average temperature of the intermediate zone and the rate of temperature change to form a baseline extrapolated temperature. Then, based on the deviation of the inlet thickness distribution, tensile velocity, tensile tension, and equivalent rheological parameters from their respective reference conditions under the current operating conditions, it retrieves or calculates the corresponding thickness correction, velocity correction, and tension-rheological joint correction. All of these corrections are expressed in Celsius temperature increments, and their values ​​are predetermined by the calibration samples. The predicted temperature is given by the following formula:

[0029] In the formula, the number of control cycles corresponding to the prediction step size. Duration of a single control cycle The product of these factors constitutes the time extrapolation reference; the temperature correction caused by thickness, velocity, tension, and equivalent rheological state is denoted as... , and The above three corrections were all calculated from historical calibration data using the following linear mapping formula:

[0030]

[0031]

[0032] in, This represents the current average temperature in the intermediate zone. These are pre-set constant calibration coefficients; These are the reference thickness, reference tensile speed, reference tensile tension, and reference equivalent rheological parameters under the calibration conditions. The system further calculates and If the difference is greater than a preset positive threshold, the temperature change trend is determined to be rising; if the difference is less than a preset negative threshold, the temperature is determined to be falling; if it is between the positive and negative thresholds, the temperature is determined to be stable. By first mapping each process variable to a temperature correction value and then uniformly superimposing it into the predicted temperature, it can be ensured that the prediction link remains consistent in both physical meaning and control implementation.

[0033] In one embodiment, the temperature prediction module includes a prediction model and a model update unit. The prediction model is constructed based on historical online temperature data and offline roughness detection results. The model update unit is used to update the model parameters according to the deviation between the returned temperature and the prediction results. The returned temperature is temperature data collected by the dual-source temperature acquisition module and processed by time alignment and position correspondence.

[0034] In this embodiment, the temperature prediction module includes a prediction model and a model update unit; the prediction model is constructed based on historical online temperature data and offline roughness detection results. The prediction model employs a multiple linear regression structure with a bias term. Its input feature vector has a 6-dimensional dimension, specifically corresponding to the comprehensive temperature of the intermediate zone and the inlet thickness. , stretching speed Tension Equivalent rheological parameters and the rate of temperature change Quantization value; The output vector has a 1-dimensional dimension, corresponding to the predicted temperature result. When the model is initially built, the mean squared error is used as the loss function and least squares fitting is performed based on historical samples to determine the basic weight parameters. Online temperature data is used to reflect the temperature changes of each batch of films in the synchronous biaxial stretching zone. Offline roughness detection results are converted into target temperature labels using a preset penalty rule and a mean square error loss function. The specific conversion rule is as follows: using the historical online temperature of the corresponding batch as the base label, when the local roughness exceeds the set standard value, a fixed temperature penalty term is superimposed on the base label to form the target temperature label. Used for supervised comparison during model training; The model update unit receives the returned temperature during production operation and compares the returned temperature with the prediction results under the same location and the same control cycle. The model update process employs an incremental compensation mechanism, calculating the difference between the current cycle's predicted temperature and the returned temperature. If this difference exceeds the allowable error band for a preset number of consecutive control cycles (5 cycles) and the direction is consistent, it indicates a systematic prediction bias. In this case, the model update unit calculates the arithmetic mean of the differences over these 5 consecutive cycles as the moving average. This moving average is then multiplied by a preset learning rate ranging from 0.1 to 0.2 and used as a compensation increment, which is then added to the temperature output bias parameter of the prediction model. This ensures that the prediction result gradually and smoothly approaches the current production line status, avoiding control oscillations caused by a single sudden disturbance. The returned temperature comes from the dual-source temperature acquisition module, and time alignment and position correspondence processing have been completed. Therefore, the model update unit does not need to re-register the original sensor data when reading it. If the inlet thickness distribution within a certain control cycle If the update fails, the temperature prediction module retains the thickness distribution of the previous valid period as the input value for the current period, and continues to receive the new comprehensive temperature distribution and temperature change rate to ensure that the prediction link is not interrupted. If the stretching speed or tensile tension If a switch occurs within the current control cycle and the process parameters are not yet stable, the deviation formed in this cycle by the model update unit will not be used to update the model parameters immediately. Instead, it will be corrected after a continuous and consistent deviation appears in subsequent effective cycles, so as to avoid the single-cycle deviation when parameters change abruptly directly affecting subsequent predictions. If the returned temperature is missing, the model update will be paused for this cycle, and only the predicted output will be retained for temperature adjustment. The missing cycle will not be included in the model correction basis.

[0035] In one embodiment, the zone temperature control module divides the stretching zone laterally into at least six independent control zones, including the middle zone. Install infrared radiation compensators in the edge area. Equipped with a hot air circulation heater and adjustable cooling baffles; The zone temperature control module has a built-in process temperature window that meets the set temperature parameters. Crystal melting point Below Crystal melting point The compensation trigger value is determined based on the stretching speed, equivalent rheological parameters, and intermediate zone thickness, and the temperature gradient exponent in the intermediate zone is calculated. It is calculated by dividing the absolute value of the difference between the center temperature of the intermediate zone and the average temperature at the edge of the intermediate zone by the transverse width of the intermediate zone.

[0036] In this embodiment, the zone temperature control module divides the stretching zone laterally into at least 6 independent control zones; the middle zone Equipped with an independent infrared radiation compensator, edge area Equipped with a hot air circulation heater and adjustable cooling baffles; An independent infrared radiation compensator is configured to provide heat compensation to the central zone; a hot air circulation heater and an adjustable cooling baffle are configured to regulate the heat exchange conditions in the edge zone. The zone temperature control module has a pre-stored process temperature window that meets the requirements of... Crystal melting point Below Crystal melting point The temperature adjustment process is based on the principle of ensuring that the temperature of each transverse zone of the thin film is within the specified window. Meanwhile, the module determines the compensation trigger value by combining the tensile speed, equivalent rheological parameters, and intermediate zone thickness; the adjustment of the compensation trigger condition follows a clear process influence logic to avoid using the same trigger standard under different operating conditions. When the thickness of the intermediate zone is greater than the preset thickness threshold or the stretching speed is greater than the preset speed threshold, the heat conduction lag inside the film increases, and the system accordingly lowers the compensation trigger value so that compensation can be triggered earlier when the temperature limit is small. When the equivalent rheological parameters characterize the increase in material viscosity leading to an increase in internal heat generated by tensile deformation, the system appropriately increases the compensation trigger value to offset some of the internal heat generation and avoid premature heat compensation causing local temperature over-limit. Specifically, compensation trigger value The determination logic is as follows: Set the baseline trigger value. According to the stretching speed Thickness of the middle zone and equivalent rheological parameters Perform dynamic correction and compensate for trigger values. Determined as:

[0037] In the formula, the calculated compensation trigger value Compared with the base trigger value All dimensions are in the temperature gradient unit to match the temperature gradient exponent in the intermediate region. The reference tensile speed, reference thickness, and reference rheological parameters under the calibration conditions are respectively determined by... express; To ensure strict dimensional consistency in algebraic operations, the sensitivity coefficient... It not only characterizes the intensity of the physical response, but also acts as a dimensional alignment factor; specifically, the sensitivity coefficient... The dimensions of are defined as Sensitivity coefficient The dimensions are Sensitivity coefficient The dimensions are ; The above coefficients were obtained by fitting offline historical process data and verifying by dimension conversion, so as to ensure that the sum of all corrections is uniformly converted into pure temperature gradient change values. The zone temperature control module calls the aforementioned intermediate zone temperature gradient index. It is used to reflect whether a significant lateral temperature trough has appeared inside the intermediate zone, and based on this, in conjunction with the predicted temperature results, to determine whether to enter compensation control.

[0038] In one embodiment, when the temperature gradient in the intermediate region is exponential Greater than the compensation trigger value, or the predicted temperature in the intermediate zone and When the absolute value of the difference is less than the first preset threshold, the zone temperature control module first directs the temperature to the middle zone. A compensation instruction was issued, in which, The first preset threshold is the allowable lower limit difference calibrated based on the specific heat capacity and the maximum heating rate, which is determined according to the maximum dynamic response time of the temperature sensor and the thermal conduction hysteresis error. When the compensation in the middle region causes the temperature in the edge region to be similar to... Crystal melting point When the absolute value of the difference is less than the second preset threshold, the zone temperature control module simultaneously reduces the heating amount of hot air in the edge zone or increases the opening of the cooling baffle; when the compensation in the middle zone causes the temperature in the edge zone to be less than the threshold value, the module will adjust the temperature accordingly. Crystal melting point When the absolute value of the difference is greater than or equal to the second preset threshold, the edge region maintains the current control parameters; when Less than or equal to the compensation trigger value and the predicted temperature in the middle zone and When the absolute value of the difference is greater than or equal to the first preset threshold, the current control parameter is maintained.

[0039] when Greater than the compensation trigger value, or the predicted temperature in the intermediate zone and When the absolute value of the difference is less than the first preset threshold, the zone temperature control module first directs the temperature to the middle zone. Issue a compensation command, the preset safe temperature margin Used to make the middle area close to Compensation begins before the lower limit of the crystal's melting point to reduce recovery lag after reaching the lower limit; Among them, safety temperature margin The temperature is determined based on the maximum dynamic response time and thermal conduction hysteresis error of the temperature sensor, with a specific value set between 1.5℃ and 2.0℃. The calibration of the first preset threshold reflects the allowable lower limit difference of the temperature in the intermediate zone so that it does not fall into the danger zone of heat loss. It is calibrated based on the specific heat capacity of polypropylene under the current tensile tension and the maximum heating rate of the heater. The specific value is set to 2°C to 5°C. The second preset threshold reflects the upper limit difference of the safety range that the edge temperature will not cause melt fracture or overheating degradation. It is calibrated according to the critical temperature difference corresponding to the edge divergence point in the offline roughness test results, and the value is set to 3℃ to 6℃. By clarifying the calibration basis and value range of the above threshold, the accuracy of the system judgment is effectively improved. Intermediate zone compensation is typically achieved by increasing the output of an independent infrared radiation compensator; if the intermediate zone is compensated, the edge zone temperature will be similar to... If the absolute value of the difference is less than the second preset threshold, it indicates that the edge area is approaching the upper limit temperature. At this time, the zone temperature control module will simultaneously reduce the amount of hot air heating in the edge area or increase the opening of the cooling baffle to suppress the edge area from continuing to heat up. when Less than or equal to the compensation trigger value, and the predicted temperature in the middle zone. and When the absolute value of the difference is greater than or equal to the first preset threshold, the current control parameters are maintained and no new adjustment is added to the actuator; like The compensation trigger value has been exceeded, but the temperature in the edge region is also close to... In this case, a compensation command is first sent to the middle zone, and further heating of the edge zone is simultaneously restricted. If the predicted temperature shows that the intermediate zone tends to stabilize, and If the compensation trigger value is not exceeded, the current control parameters will be maintained to avoid repeated adjustments when the temperature has basically reached equilibrium.

[0040] In one embodiment, after the zone temperature control module issues an adjustment command, it updates the control parameters based on the temperature feedback from the dual-source temperature acquisition module. The dual-source temperature acquisition module, temperature fusion module, temperature difference judgment module, and temperature prediction module synchronously update their corresponding outputs, and the zone temperature control module performs closed-loop control based on the updated outputs.

[0041] To ensure temperature stability during continuous operation, the zone temperature control module continues to receive the temperature feedback from the dual-source temperature acquisition module after issuing the adjustment command, and corrects the control parameters based on the updated temperature feedback. Correspondingly, the dual-source temperature acquisition module, temperature fusion module, temperature difference judgment module, and temperature prediction module synchronously update their respective outputs; Synchronous update here refers to using the above production line control cycle as a unified beat, and calling the most recently confirmed valid data and calculation results of each module in the same control cycle to complete a closed-loop update. It does not require all sensors to reach the same instantaneous sampling value at the exact same physical moment. After the zone temperature control module reads the updated results, it decides whether to maintain, increase, or decrease the adjustment amount of each control zone. The control mechanism executed in this way makes the temperature adjustment result gradually converge to the process temperature window based on the feedback temperature, rather than keeping the original output fixed after a single compensation. Specifically, the zone temperature control module compares the returned temperature with the current control target of the corresponding zone. If the absolute value of the deviation is greater than the preset correction band, which is ±0.5℃ to 1.0℃ of the current control target of the corresponding zone, the output of the hot air circulation heater, the opening of the cooling baffle, or the power of the infrared radiation compensator are adjusted in a fixed step of 1% to 3% of the rated power or maximum opening of the actuator. If the deviation falls into the correction zone, the current parameters remain unchanged; if the deviation directions are consistent for two consecutive control cycles, the step size will be increased by one level in the next cycle, that is, the adjustment step size will be doubled to twice the fixed step size, in order to avoid frequent adjustment jitter caused by a single feedback and to accelerate convergence after the trend is confirmed. For the boundary case, if The compensation trigger value has been exceeded, but the temperature in the edge region is also close to... If so, a compensation command is first sent to the middle zone, and further heating of the edge zone is simultaneously restricted to avoid solving the problem of insufficient temperature in the middle zone by raising the overall temperature; If a certain independent control area does not receive a valid temperature feedback in the current control cycle, the area will temporarily maintain the output according to the control parameters of the previous valid cycle, while the other control areas will still execute according to the updated results of this cycle, so as to avoid the interruption of full-area control synchronization due to the lack of temperature measurement in a single area. To ensure a deterministic execution sequence for closed-loop control in engineering, the zone temperature control module operates in four states: pending adjustment, issued, confirmed, and timeout rollback. When the control parameters of the current cycle change, the system first sets the control area to the state to be adjusted and generates an adjustment command; after the command is issued, it enters the issued state and starts the confirmation timer for one control cycle; if a valid feedback temperature corresponding to the control area is received in the timer window, it enters the confirmed state and corrects the step amount for the next cycle accordingly. If no valid feedback is received after the timeout, the system will switch to the timeout rollback state, maintaining the parameters of the previous valid cycle unchanged and not participating in the step multiplication of this cycle, in order to prevent the control quantity from being mistakenly increased due to missing data. The aforementioned state transitions always prioritize safety, prioritizing intermediate zone compensation and suppressing edge zone overheating before determining step acceleration based on continuous deviations. Through the combination of state machines, timeout backoff, and acknowledgment loops, the adjustment actions can form a traceable, backoffable, and convergent deterministic control link within each control cycle. In this production scenario, BOPP film, when used as capacitor film, composite current collector base film, packaging film, optical film, etc., has high requirements for transverse temperature consistency, and the heat distribution in the middle area and the edge area has obvious differences. This implementation method utilizes multi-control zone arrangement and process temperature window constraints. The coordination of criteria, predicted temperature criteria, and feedback correction mechanisms enables temperature regulation to focus on replenishing heat in the central zone and limiting heat in the edge zone, thereby reducing the lateral temperature difference and maintaining [temperature stability]. crystal orientation The temperature conditions required for crystal transformation, and to reduce roughness unevenness in the intermediate region caused by insufficient temperature.

Claims

1. A stretching process control system suitable for synchronous biaxially stretched BOPP film, characterized in that, include: The dual-source temperature acquisition module is used to acquire the ambient temperature of the stretching zone and the surface temperature of the film. After unifying them to the same time reference and the same horizontal coordinate system, time alignment and position correspondence are performed, and the corresponding temperature data is output. The temperature fusion module is used to fuse the corresponding temperature data to form a comprehensive temperature distribution across the entire surface of the thin film and output the temperature results for each horizontal zone. The temperature difference judgment module is used to divide the film laterally into edge regions based on the temperature results of each lateral zone. and the middle area Determine the temperature difference between the two zones and output the intermediate zone. Temperature deviation and rate of temperature change ; The temperature prediction module combines the comprehensive temperature distribution, film inlet thickness distribution, stretching speed, stretching tension, equivalent rheological parameters of polypropylene, and the temperature change rate to predict and output the predicted temperature of the intermediate zone. and temperature change trends; The control system also includes a hot air circulation heater, a cooling baffle, an infrared radiation compensator, and a zone temperature control module; The zone temperature control module is connected to the edge area. The hot air circulation heater and the cooling baffle are located in the intermediate area. The infrared radiation compensator is used to adjust according to the temperature deviation. Rate of temperature change Predicted temperature The hot air circulation heater, the cooling baffle and the infrared radiation compensator are controlled according to the temperature change trend, and the corresponding temperature data collected by the dual-source temperature acquisition module and processed by time alignment and position correspondence are used as the feedback temperature correction and adjustment output. The zoned temperature control module divides the stretching zone laterally into at least 6 independent control zones, including the middle zone. The infrared radiation compensator is installed in the edge region. Equipped with a hot air circulation heater and adjustable cooling baffles; The zone temperature control module has a built-in process temperature window that meets the set temperature parameters. Crystal melting point Below Crystal melting point The compensation trigger value is determined based on the stretching speed, equivalent rheological parameters, and intermediate zone thickness, and the temperature gradient exponent in the intermediate zone is calculated. It is calculated by dividing the absolute value of the difference between the center temperature of the middle zone and the average temperature at the edge of the middle zone by the transverse width of the middle zone. When the temperature gradient index of the intermediate region Greater than the compensation trigger value, or the predicted temperature of the intermediate zone and When the absolute value of the difference is less than a first preset threshold, the zone temperature control module first directs the temperature to the middle zone. A compensation instruction was issued, in which, The first preset threshold is a preset safety temperature margin determined based on the maximum dynamic response time of the temperature sensor and the thermal conduction hysteresis error. It is the difference between the allowable lower limit calibrated based on the specific heat capacity and the maximum heating rate. When the middle area compensation causes the edge area temperature to be similar to the above... Crystal melting point When the absolute value of the difference is less than the second preset threshold, the zone temperature control module simultaneously reduces the heating amount of hot air in the edge zone or increases the opening of the cooling baffle; when the compensation in the middle zone causes the temperature in the edge zone to differ from the... Crystal melting point When the absolute value of the difference is greater than or equal to the second preset threshold, the edge region maintains the current control parameters; when Less than or equal to the compensation trigger value and the predicted temperature in the intermediate zone and When the absolute value of the difference is greater than or equal to the first preset threshold, the current control parameter is maintained.

2. The stretching process control system for synchronous biaxially stretched BOPP film according to claim 1, characterized in that, The dual-source temperature acquisition module includes a contact temperature sensor array and an infrared scanning unit. The contact temperature sensor array is arranged above and below the synchronous biaxial stretching zone and is arranged longitudinally and laterally to acquire the two-dimensional ambient temperature distribution within the stretching zone. The infrared scanning unit is located at the top of the stretching zone and is used to continuously scan the surface of the film during operation and output the two-dimensional temperature distribution of the film surface.

3. The stretching process control system for synchronous biaxially stretched BOPP film according to claim 1, characterized in that, The dual-source temperature acquisition module maps the ambient temperature and the thin film surface temperature to the same time reference and the same horizontal coordinate system, and sends the processed temperature data to the temperature fusion module.

4. The stretching process control system for synchronous biaxially stretched BOPP film according to claim 1, characterized in that, The temperature fusion module is used to weight and fuse the ambient temperature and the film surface temperature according to a preset weight to form a comprehensive temperature distribution, and to adjust the preset weight according to the stretching speed, surface vibration amplitude and sensor reliability. The reliability of the sensor is determined by a weighting coefficient based on the consistency between the ambient temperature and the thin film surface temperature at the same location, the sensor signal-to-noise ratio, and the stability of continuous sampling. The surface jitter amplitude is obtained by a distance measuring sensor and represents the displacement change amplitude of the thin film surface relative to a preset reference position.

5. The stretching process control system for synchronous biaxially stretched BOPP film according to claim 1, characterized in that, The temperature difference judgment module divides the thin film laterally into edge regions. and the middle area This is used to compare the temperature difference between the edge region and the middle region, and output the temperature deviation of the middle region. and rate of temperature change .

6. The stretching process control system for synchronous biaxially stretched BOPP film according to claim 1, characterized in that, The inputs to the temperature prediction module include the current overall temperature distribution and the thin film inlet thickness distribution. , stretching speed Tension The equivalent rheological parameters η of polypropylene and the intermediate region rate of temperature change The temperature prediction module outputs the intermediate zone. Predicted temperature and represent the trend of temperature change, such as rising, falling, or stabilizing.

7. The stretching process control system for synchronous biaxially stretched BOPP film according to claim 6, characterized in that, The temperature prediction module includes a prediction model and a model update unit. The prediction model is constructed based on historical online temperature data and offline roughness detection results. The model update unit is used to update the model parameters according to the deviation between the returned temperature and the prediction result. The returned temperature is the temperature data collected by the dual-source temperature acquisition module and processed by time alignment and position correspondence.

8. The stretching process control system for synchronous biaxially stretched BOPP film according to claim 1, characterized in that, After issuing the adjustment command, the zone temperature control module updates the control parameters according to the temperature feedback returned by the dual-source temperature acquisition module. The dual-source temperature acquisition module, temperature fusion module, temperature difference judgment module, and temperature prediction module synchronously update their corresponding outputs, and the zone temperature control module performs closed-loop control based on the updated outputs.

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