Film blowing production line material thickness measuring method and system

Abstract

The invention relates to the technical field of pipe film thickness measurement, in particular to a film blowing production line material thickness measurement method and system, and the method comprises the steps: carrying out the alignment flattening of a tubular thin film when the tubular thin film formed through the blowing of a film blowing machine enters a traction flattening roller, and obtaining a double-layer thin film; a thickness gauge is adopted for continuous scanning measurement in the film advancing direction, a double-layer thickness data sequence is obtained, rotation phase data of the film blowing machine are collected in real time, and the circumferential point position alignment relation of the double-layer film corresponding to each thickness measurement moment is determined based on the double-layer thickness data sequence; based on the circumferential point alignment relation and the corresponding double-layer thickness data, an overdetermined observation equation set is obtained, mathematical solution is carried out, and the thickness value of each single-layer point of the tubular film in the circumferential direction is obtained. Therefore, the thickness gauge cannot accurately measure the double-layer measurement value to the corresponding single-layer point position, and the single-layer thickness distribution accuracy is reduced.

Description

Technical Field

[0001] This application relates to the technical field of blown film thickness measurement, and in particular to a method and system for measuring the thickness of materials in a blown film production line. Background Technology

[0002] With the continuous expansion of applications in packaging, agriculture, and industry, the quality requirements for blown film products are increasing. Among these requirements, film thickness uniformity is a key indicator affecting its mechanical, optical, and barrier properties. To achieve high-precision thickness control, blown film production lines are generally equipped with thickness measurement systems, especially non-contact thickness gauges based on optical principles (such as lasers and infrared interferometry), which are widely used due to their fast response speed and high accuracy.

[0003] Existing optical thickness measurement methods typically involve directly scanning the flattened tubular film to obtain its total thickness after it has been drawn and flattened into a double-layer film. However, in blown film production, to achieve uniform film thickness, the blown film die is often designed as a rotatable structure. This causes the material distribution on the circumference of the tubular film to continuously rotate relative to the die exit position after forming. When this tubular film with a rotating phase change is flattened, at any given measurement moment, the specific points on the circumference of the upper and lower layers constituting the double-layer film for measuring total thickness are dynamically changing, rather than fixed.

[0004] Most existing optical thickness measurement schemes neglect the dynamic changes in the flattening alignment points caused by die rotation, leading to fundamental errors in the measurement principle: they mistakenly interpret dynamically changing, random combinations of upper and lower layer thicknesses as a simple superposition of two fixed, equal layers. Therefore, even with high-precision optical thickness gauges, the directly output double-layer thickness data cannot accurately reflect the true single-layer thickness distribution of the original tubular film in the circumferential direction. This distortion masks crucial information about the film's circumferential inhomogeneity, rendering process adjustments based on such measurement data (such as die gap adjustment) inaccurate and failing to meet the refined thickness uniformity control requirements of high-end thin film manufacturing. Summary of the Invention

[0005] In view of this, this application provides a method and system for measuring the thickness of materials in a blown film production line. By simultaneously collecting the dynamic alignment relationship and double-layer thickness data after the film is flattened, and constructing and solving the overdetermined observation equation set, the accuracy of the thickness distribution measurement of each single-layer point in the circumferential direction of the tubular film is improved while maintaining the advantages of non-contact and continuous optical thickness measurement. This solves the technical problem in the prior art where the uncertainty of the alignment relationship caused by dynamic rotation makes it impossible for the thickness gauge to accurately measure the double-layer measurement value to the corresponding single-layer point, thus reducing the accuracy of the single-layer thickness distribution.

[0006] This application provides a method and system for measuring the thickness of materials in a blown film production line, which adopts the following technical solution: A method for measuring the thickness of materials in a blown film production line includes: When the tubular film blown into shape by the blown film machine enters the traction flattening roller, the tubular film is aligned and flattened to obtain a double-layer film; Based on a bilayer film, a thickness gauge is used to continuously scan and measure the thickness of the bilayer film along the film's travel direction to obtain a bilayer thickness data sequence. The rotation phase data of the blown film machine is collected in real time, and the alignment relationship of the circumferential points of the double-layer film is determined based on the double-layer thickness data sequence at each thickness measurement moment. Based on the alignment relationship of the circumferential points and the corresponding double-layer thickness data, the overdetermined observation equation set is obtained; By mathematically solving the overdetermined observation equations, the thickness values ​​of each single layer point in the circumferential direction of the tubular film are obtained.

[0007] By adopting the above technical solution, the thickness signal that is easy to measure is obtained by using the flattened double-layer film structure. By synchronously acquiring the rotational phase and dynamically tracking the alignment changes of the circumferential points, and on this basis establishing an overdetermined observation equation set, the dynamically aligned multiple sets of double-layer thickness measurements are inverted and solved into the accurate thickness distribution of each single-layer point in the circumferential direction. This achieves the acquisition of the complete circumferential thickness profile of the tubular film without the need to directly measure the single-layer film, overcoming the fundamental problem of measurement inaccuracy caused by neglecting rotational dynamics in traditional optical thickness measurement methods.

[0008] Preferably, based on a bilayer thin film, a thickness gauge is used to continuously scan and measure along the film's travel direction to obtain a bilayer thickness data sequence, including: The thickness gauge is driven to reciprocate in the width direction of the double-layer film at a preset fixed frequency, and samples are taken at equal intervals along the film's travel direction in each scanning cycle to obtain a set of thickness measurement points. By correlating each thickness measurement point with the corresponding sampling time and the probe's position coordinates in the film width direction, a double-layer thickness data sequence is obtained.

[0009] By adopting the above technical solution, the thickness gauge is driven to reciprocate by a preset fixed frequency, achieving full coverage of the film width direction. Equal-interval sampling is performed in each scanning cycle to ensure the regularity and continuity of the measurement along the film's travel direction. Each measurement point is precisely associated with its sampling time and probe position coordinates, constructing a spatiotemporally synchronized and positionally clear double-layer thickness data sequence, ensuring full coverage and temporal synchronization of thickness measurement in two-dimensional space of film width and travel direction.

[0010] Preferably, based on the double-layer thickness data sequence, determining the circumferential alignment relationship of the double-layer film at each thickness measurement moment includes: The circumference of the tubular film is divided into multiple discrete points; Establish a mapping function between the rotated phase data and the discrete point positions; Based on the sampling time of each data point in the double-layer thickness data sequence, query the rotation phase data at the corresponding time. Based on the rotation phase data and mapping function at the corresponding time, the alignment relationship of the circumferential points at each sampling time is obtained.

[0011] By adopting the above technical solution, the continuous space is transformed into a set of discrete points that can be described by a mapping function by discretizing the circumference of the tubular film. By establishing a mapping function between the rotation phase and the discrete points, a conversion bridge is built between the physical rotation motion and the mathematical point number. Then, based on the thickness data sampling time, the rotation phase is queried, and the time synchronization between the measurement time and the state of the film circumference is achieved. Finally, by using the phase-point mapping relationship, the specific single-layer point combination that constitutes each double-layer thickness measurement value is tracked during the rotation process, and the dynamic alignment law during the rotation process is accurately characterized by a mathematical model.

[0012] Preferably, establishing a mapping function between the rotated phase data and discrete point positions includes: Phase rotation data includes the mold head rotation angle; Based on the die head rotation angle and the total number of discrete points, determine the actual phase of each point on the die head in the blown film machine at the current moment; Based on the actual phase, the known travel time of the tubular film from the blown film die outlet to the thickness gauge measurement position and the preset film stretching ratio are used for compensation to obtain the compensated phase of the film point at the thickness gauge measurement position. The compensation phase is matched with the discrete points on the circumference of the tubular film to obtain multiple pairs of aligned circumferential point numbers. A mapping function is established based on multiple pairs of aligned circular point numbers.

[0013] By adopting the above technical solution, the real-time state of the mechanical phase determined from the rotation angle of the die head provides an accurate spatial reference for the mapping function. Then, by introducing film travel time delay and tensile deformation compensation, the instantaneous phase at the die head is corrected to the effective phase of the film point at the thickness gauge measurement section, thereby accurately depicting the dynamic deformation process of the film from forming to measurement. By matching the corrected compensation phase with the circumferential discretized model, the specific point number pairs that are actually in the aligned state at the measurement moment are determined. Finally, based on these specific point alignment relationships, a complete mapping function from the rotation angle to the circumferential discrete point alignment relationship is constructed. Through multi-level compensation and correction, the accuracy of the mapping relationship between the rotation phase and the actual spatial position of the film point is improved.

[0014] Preferably, a mapping function is established based on multiple pairs of aligned circumferential point numbers, which further includes: Optical marking points are set on the tubular section of the tubular film before it enters the traction flattening roller; Continuously capture the actual position of optical markers; The actual position is compared with the preset theoretical position to obtain the position deviation; Adjust the mapping function based on the positional deviation.

[0015] By adopting the above technical solution, optical markers are set and tracked on the tubular film to obtain their actual motion trajectory. By comparing the actual position with the expected position of the theoretical model, the dynamic position deviation is calculated, and the mapping function is corrected in real time using this deviation. This can effectively compensate for actual production disturbances not covered by the theoretical model, such as speed fluctuations or non-uniform stretching, thereby dynamically improving the accuracy of the point alignment mapping and the robustness of the system.

[0016] Preferably, based on the alignment relationship of the circumferential points and the corresponding double-layer thickness data, the overdetermined observation equation set is obtained, which also includes: Real-time acquisition of temperature distribution data of the double-layer film at the measurement location of the thickness gauge; Based on temperature distribution data and preset material thermal expansion coefficients, thermal expansion compensation correction is performed on the original measured values ​​in the double-layer thickness data sequence to obtain the corrected double-layer thickness data sequence.

[0017] By adopting the above technical solution, the original physical thickness value obtained by the thickness gauge is divided into two parts: the inherent thickness of the material and the effect of environmental thermal expansion, by collecting the temperature distribution data of the thin film in real time. Based on the thermal expansion coefficient of the material, the original thickness measurement value is corrected point by point, thereby eliminating the measurement deviation caused by temperature change and obtaining a data sequence that better reflects the true thickness state of the thin film material, thus eliminating the interference of temperature fluctuation on the measurement accuracy.

[0018] Preferably, based on the alignment relationship of the circumferential points and the corresponding double-layer thickness data, an overdetermined observation equation set is obtained, including: The thickness of the single-layer film corresponding to each discrete point is defined as an unknown variable. A linear equation is established for each pair of circumferential point alignment relationships and the corresponding double-layer thickness measurements; The linear equations established at all measurement times are summarized to form a system of linear equations, which serves as the overdetermined observation equation system.

[0019] By adopting the above technical solution, the thickness of a single layer at discrete points on the circumference is defined as an unknown variable. Each thickness measurement and its corresponding alignment relationship are transformed into a linear equation. By summarizing the measurement data at all times, an overdetermined set of observation equations with more equations than unknowns is formed. Thus, the dynamic physical measurement process is systematically transformed into a linear model that can be solved mathematically. This enables the accurate separation and reconstruction of the thickness of each single layer at each point on the circumference, thereby improving the accuracy of the thickness distribution of the tubular film at each single layer at each point on the circumference.

[0020] A material thickness measurement system for a blown film production line, comprising: A blown film machine is used to blow tubular thin films; The flattening traction unit is used to flatten the tubular film into a double-layer film when the tubular film is detected. The thickness gauge is located downstream of the flattening and traction unit and is used to continuously scan and measure the double-layer film along the film's travel direction to obtain a double-layer thickness data sequence. A rotating phase sensor is installed on the rotating parts of a blown film machine to collect rotating phase data in real time. The data processing and control unit is communicatively connected to both the thickness gauge and the rotating phase sensor, and is used to perform the following: Receives dual-layer thickness data sequences and rotation phase data; Determine the alignment relationship of the circumferential points at each measurement time; Based on the alignment relationship of the circumferential points and the corresponding double-layer thickness data, an overdetermined observation equation set was constructed and solved. Output the thickness value of each single layer point in the circumferential direction of the tubular film.

[0021] By adopting the above technical solution, the flattening and traction unit provides a stable and reliable physical morphology for film measurement. The thickness gauge and rotating phase sensor synchronously acquire the film's thickness and spatial state information with high precision. The data processing and control unit uses a mathematical model to process multi-source data in real time, transforming the dynamic physical process into a solvable mathematical problem and outputting accurate single-layer thickness distribution. Through hardware integration and algorithm collaboration, accurate perception and compensation of rotational dynamics are achieved on existing blown film production lines, thereby solving the industry technical problem of inaccurate single-layer thickness measurement caused by the inability to determine dynamic alignment relationships, and improving the application depth and accuracy of optical thickness measurement equipment in rotary blown film scenarios.

[0022] An electronic device includes a memory and a processor. The memory stores a computer program, which, when executed by the processor, causes the processor to perform the steps of a method for measuring the thickness of materials in a blown film production line.

[0023] A computer-readable storage medium having a computer program stored thereon, which, when executed, implements a method for measuring the thickness of materials in a blown film production line.

[0024] In summary, this application includes at least one of the following beneficial technical effects: By flattening a tubular thin film into a double-layer structure and performing continuous scanning measurements, combined with real-time synchronous acquisition of rotational phase data, the dynamically changing alignment relationship of circumferential points is systematically correlated with the double-layer thickness measurement value. Based on this, an overdetermined observation equation set is constructed and solved, enabling the acquisition of the complete circumferential thickness profile of the tubular thin film without the need for direct measurement of the single-layer film. This overcomes the fundamental problem of measurement inaccuracy caused by neglecting rotational dynamics in traditional optical thickness measurement methods. To address the issues of uncertain alignment and inaccurate single-layer thickness measurement caused by neglecting the dynamic rotation of the thin film in existing technologies, this method fundamentally overcomes the inherent errors caused by alignment point drift in traditional methods by simultaneously sensing the rotation phase and thickness data and establishing a dynamic alignment relationship, thereby improving the measurement accuracy of single-layer thickness distribution. To address the problem that traditional indirect measurement methods cannot obtain a complete thickness profile in the circumferential direction, this method transforms the physical measurement process into solving an overdetermined set of equations, enabling low-cost, non-invasive acquisition of detailed thickness distribution across the entire circumference of the thin film without direct measurement of the single layer, providing a reliable data foundation for precise process adjustments. Furthermore, by introducing optimized schemes such as dynamic calibration with optical markers and temperature compensation correction, the system further enhances its adaptability and robustness to various dynamic disturbances and environmental factors in actual production processes, ensuring long-term stability and accuracy under complex operating conditions. This better meets the industry demand for refined control and improvement of thickness uniformity in high-end thin film manufacturing. Attached Figure Description

[0025] Figure 1This is a flowchart illustrating the steps of a blown film production line material thickness measurement method provided in an embodiment of this application.

[0026] Figure 2 This is a schematic diagram of the double-layer thin film alignment structure provided in the embodiments of this application.

[0027] Figure 3 This is a structural block diagram of a blown film production line material thickness measurement system provided in an embodiment of this application. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. It should be noted that in the optional embodiments of this application, the object information and other related data involved require the permission or consent of the object when the embodiments of this application are applied to specific products or technologies, and the collection, use, and processing of related data must comply with the relevant laws, regulations, and standards of the relevant countries and regions. That is to say, if the embodiments of this application involve data related to the object, it needs to be obtained with the authorization and consent of the object, the authorization and consent of the relevant departments, and in compliance with the relevant laws, regulations, and standards of the country and region. If personal information is involved in the embodiments, the acquisition of all personal information requires the consent of the individual. If sensitive information is involved, the separate consent of the information subject is required, and the embodiments also need to be implemented with the authorization and consent of the object. Example 1

[0029] Please see Figure 1 , Figure 2 This application provides a method for measuring the thickness of materials in a blown film production line, comprising: Film blowing machine: A film blowing machine is a plastic processing equipment that heats and melts plastic particles and blows them into a film. It is mainly used to produce packaging films made of materials such as PE, POF, and PVC. Its core processes include plastic particle melt extrusion, compressed air blowing molding, cooling and shaping, and traction winding, involving components such as screw extruders, dies, cooling devices, and winding systems.

[0030] Thickness gauge: An optical measuring device used to detect the thickness of thin films during the blown film process, especially non-contact thickness gauges based on optical principles such as laser, infrared, or interferometry (e.g., laser thickness measurement, infrared thickness measurement, spectral interferometry, etc.). These gauges can monitor the thickness distribution of the film in real time, ensuring product quality during production. Laser thickness measurement involves scanning the surface of the film with a laser beam and measuring the intensity change of the reflected laser beam to estimate the film thickness. This method allows for real-time, non-contact thickness measurement and is suitable for high-precision measurements. X-ray (or other rays such as γ-rays and α-rays) transmission methods calculate film thickness using the attenuation of X-rays as they pass through the film. The thicker the film, the lower the X-ray transmittance. This method is applicable to various materials, especially non-metallic films. Ultrasonic thickness measurement uses the change in the propagation speed of ultrasonic waves as they pass through the film to measure thickness. The advantage of this method is that it can be used on different film materials and is suitable for thicker films.

[0031] Step 101: When the tubular film blown into shape by the blown film machine enters the traction flattening roller, the tubular film is aligned and flattened to obtain a double-layer film.

[0032] Tubular films are continuous tubular structures formed by extruding molten plastic from a die, inflating it with compressed air, and then cooling and shaping it.

[0033] Traction flattening rollers refer to the paired roller devices installed in the traction section of a blown film machine. Their function is to press the blown tubular film into a tightly bonded double-layer flat film structure while maintaining the basic alignment of the film layers, so as to facilitate subsequent thickness measurement.

[0034] Alignment flattening refers to adjusting the gap, parallelism, and traction tension of the flattening rollers to ensure that the two opposite surfaces (i.e., the upper and lower layers that will form the double-layer film) of the tubular film maintain a point-to-point correspondence as much as possible during the flattening process. This avoids non-uniform deformation caused by misalignment, folding, or wrinkles, thereby ensuring that the flattened double-layer film has a clear and stable two-layer superimposed structure in the width direction. Figure 2 As shown.

[0035] In this embodiment, the tubular film extruded and blown into shape by the blown film die head is cooled and shaped, and then pulled to the flattening roller unit. By adjusting the inter-roller pressure and traction speed of the flattening roller, the tubular film is gradually pressed into a double-layer film in a naturally stretched state, while maintaining its original circumferential point correspondence basically unchanged. This provides a structurally consistent and morphologically stable test object for subsequent thickness measurement and single-layer inversion based on the double-layer structure.

[0036] Step 102: Based on the double-layer film, use a thickness gauge to continuously scan and measure along the film's travel direction to obtain a double-layer thickness data sequence.

[0037] The double-layer thickness data sequence is a structured data set obtained by a thickness gauge during continuous scanning measurement of a flattened double-layer film. The data is arranged in chronological order and includes optical thickness measurement values, sampling time, and the corresponding position coordinates of the probe in the width direction of the film.

[0038] Preferably, step 102 includes the following sub-steps: S21. Drive the thickness gauge to reciprocate in the width direction of the double-layer film at a preset fixed frequency, and sample at equal intervals along the film's travel direction in each scanning cycle to obtain a set of thickness measurement points.

[0039] The preset fixed frequency refers to the time frequency of the periodic motion corresponding to one complete reciprocating transverse scan of the thickness gauge probe in the width direction of the film, measured in Hertz (Hz). This frequency determines the speed of the probe's transverse scan and the density of the transverse distribution of measurement points. Preferably, the fixed frequency set in this embodiment is selected between 0.5Hz and 5Hz to ensure full coverage of the width direction during the film's movement.

[0040] The scanning cycle refers to the time it takes for the thickness gauge probe to complete one full transverse reciprocating motion from one side of the film width direction to the other side and back to the starting position.

[0041] In this embodiment, the thickness gauge probe performs a transverse reciprocating scan in the width direction of the film at a preset fixed frequency (e.g., 1Hz), with a corresponding scanning cycle of 1 second. Within this scanning cycle, the thickness gauge triggers a thickness measurement at equal time intervals (e.g., every 10 milliseconds), thereby achieving equidistant sampling in the film's travel direction. Each measurement synchronously records the thickness value, sampling time, and the real-time position coordinates of the probe in the film's width direction. By integrating and sorting the data collected from multiple consecutive scanning cycles, a two-dimensional thickness measurement point set covering the film's width and travel direction is obtained.

[0042] S22. Correlate each thickness measurement point with the corresponding sampling time and the position coordinates of the probe in the film width direction to obtain a double-layer thickness data sequence.

[0043] In this embodiment, after each sampling, the thickness gauge encapsulates and associates the output original thickness value, the precise sampling time provided by the system clock, and the real-time position coordinates of the probe in the film width direction fed back by the encoder of the scanning mechanism to form a structured data record containing a time-position-thickness triplet. By arranging and indexing all sampling points in a time sequence, a double-layer thickness data sequence is finally generated, realizing the precise alignment and structured storage of thickness measurement data in the time and space dimensions, and preventing model construction errors caused by data chaos or spatiotemporal mismatch.

[0044] Step 103: Collect the rotation phase data of the blown film machine in real time, and determine the circumferential point alignment relationship of the double-layer film at each thickness measurement moment based on the double-layer thickness data sequence.

[0045] Rotational phase data refers to quantitative information used to describe the circumferential position of the rotating component (the die head in this embodiment) of a blown film machine at any given time.

[0046] In the embodiments of this application, the rotation phase data includes, but is not limited to, the rotation angle of the mold head, which is measured and output in real time by a high-precision encoder (such as an absolute encoder) mounted on the rotation shaft of the mold head. Its value range is typically 0° to 360°, representing a complete rotation cycle.

[0047] The circumferential point alignment relationship refers to the correspondence between a pair of single-layer film points that were originally located at different positions on the circumference of the tubular film at a specific measurement moment when the tubular film is flattened to form a double-layer film, but are now closely attached to each other after flattening and together constitute the double-layer thickness of the measurement point.

[0048] Preferably, step 103 includes the following sub-steps: S31. Divide the circumference of the tubular film into multiple discrete points.

[0049] Discrete points refer to a number of uniquely numbered, equally spaced locations that are virtually divided into the circumference of a continuous tubular film for mathematical modeling and analysis.

[0050] Preferably, the number of points determines the spatial resolution of the subsequent model. The larger the number of points, the more refined the final calculated circumferential thickness distribution will be, but the computational load will also increase accordingly. Preferably, in this embodiment, the number of points can be set to between 100 and 200.

[0051] In this embodiment, it is assumed that the ideal circumferential cross-section of the tubular film is uniformly discretized into N points. For example, if N=120, starting from an arbitrarily set zero point on the circumference (such as the initial point aligned with the zero point of the mold rotation), a discrete point is defined every 3° (360° / 120) along the circumferential direction, and sequentially numbered as P1, P2, ..., P120, forming a circumferential coordinate system to uniquely identify any virtual position on the circumference of the film.

[0052] It is important to understand that the discrete points referred to are theoretical divisions and do not need to be physically marked on the thin film. Their purpose is to provide a location index for calculation.

[0053] S32. Establish a mapping function between the rotated phase data and the discrete point positions.

[0054] A mapping function is a rule used to establish a deterministic relationship between the motion of rotating machinery and the spatial position of a thin film. It maps the rotation angle of the die head at any given moment to a specific pair of point numbers that form the alignment relationship of the two-layer thin film at the thickness gauge measurement position at that moment.

[0055] Preferably, step S32 includes the following steps: S321. Based on the die head rotation angle and the total number of discrete points, determine the actual phase of each point on the die head in the blown film machine at the current moment.

[0056] The actual phase refers to the real-time angular position of each discrete point on the thin film relative to a fixed reference system at the die exit.

[0057] Preferably, due to the rotation of the die head, the circumferential position of any point on the die head will change over time.

[0058] In this embodiment, let the current time t be θ(t) (e.g., θ(t) = 45°) of the rotation angle of the mold head, which is collected in real time by the rotating phase sensor. Given that the circumference is divided into N equal points, and the theoretical position (initial phase) of each point when the mold head is stationary is fixed, then for point Pk (k = 1, 2, ..., N), its actual phase φ at the mold head... m (k,t) is calculated by adding the initial phase to the current rotation angle. For example, if the initial phase of P1 is defined as 0°, then its actual phase φ on the mold head at the current moment is... m (1,t)=0°+θ(t)=45°. Similarly, the initial phase of Pk is (k-1)*(360° / N), then φ m (k,t)=(k-1)*(360° / N)+θ(t) accurately calculates the physical rotation angle of the mold head as the real-time spatial phase of each discrete point, realizing the digital conversion of rotating mechanical motion into the circumferential position information of the thin film.

[0059] S322. Based on the actual phase, and combined with the known travel time of the tubular film from the blown film die outlet to the thickness gauge measurement position, and the preset film stretching ratio, compensation is performed to obtain the compensated phase of the film position at the thickness gauge measurement position.

[0060] Travel time refers to the time delay experienced by the film after it is extruded from the die outlet, through blowing, cooling, and traction, to the measurement position directly below the thickness gauge probe.

[0061] Preferably, the travel time can be calculated from the film's traction speed and the fixed path length from the die exit to the thickness gauge, denoted as Δt. More preferably, the travel time can be set to 3 seconds.

[0062] Film elongation refers to the ratio of film elongation in the machine direction (MD) due to traction force. This causes the film to shrink in the transverse direction (TD), i.e., the circumferential direction, according to Poisson's ratio.

[0063] Preferably, the film stretching ratio can be preset by material properties and production process parameters or estimated online by sensors, and is denoted as the shrinkage coefficient α (0<α≤1, for example, α=0.97, which means that the circumference length shrinks to 97% of the original length).

[0064] In this embodiment, when the thickness gauge measures at time t, the detected thin film element is actually extruded from the die at an earlier time (t-Δt). Therefore, for any discrete point Pk, the die rotation angle θ(t-Δt) corresponding to the extrusion time (t-Δt) at the die exit is first obtained based on the historical data recorded by the rotating phase sensor, and then the historical actual phase φ at the die exit of that point is calculated. m (k,t-Δt)=(k-1)*(360° / N)+θ(t -Δt), and in order to reflect the circumferential deformation caused by traction and stretching during the movement of the film from the die head to the thickness gauge position, it is necessary to perform circumferential shrinkage compensation on the historical actual phase.

[0065] Specifically, φ m (k,t-Δt) is multiplied by a preset shrinkage coefficient α, and the result is moduloed to ensure that the phase value is within a circumferential range of 0° to 360°, thus obtaining the compensated phase φ at the current measurement time t, located at the thickness gauge measurement section. c (k,t)=[φ m (k,t-Δt)*α] mod 360°.

[0066] In this embodiment, by introducing two process parameters, travel time and film stretching shrinkage coefficient, the phase information at the die head is double-corrected through time delay compensation and deformation shrinkage compensation, so that the calculated compensated phase φ c (k,t) can more realistically reflect the actual spatial position of the film material when it finally arrives at the measurement section after going through the complete production process of extrusion, blowing, cooling, traction and stretching deformation. It improves the accuracy of the mapping relationship from the rotation phase to the measurement point, overcomes the systematic mapping error caused by ignoring the material conveying delay and physical deformation in the traditional method, and finally ensures the accuracy and reliability of the single-layer film thickness inversion results.

[0067] S323. Match the compensation phase with the discrete points on the circumference of the tubular film to obtain multiple pairs of aligned circumferential point numbers.

[0068] In this embodiment of the application, the compensation phase φ of all discrete points is obtained. c After (k,t), it is necessary to determine which two single-layer points are aligned and bonded together at the measurement time t, directly below the thickness gauge probe, to form the double-layer film. This fundamentally solves the dynamic uncertainty of the alignment relationship caused by the rotation of the film, and enables the double-layer thickness measurement value to be correctly decomposed and associated with its corresponding single-layer thickness unknown.

[0069] It should be noted that, according to the physical flattening process, ideally, two points that were originally 180° out of phase on the circumference of the tubular film will coincide after flattening.

[0070] Preferably, the matching process is as follows: For each discrete point P i (Its compensation phase is φ) c (i,t)), find another point P among all points. j This allows the absolute value of the compensated phase difference between the two to be closest to 180°. That is, finding the condition that satisfies min|φ c (j,t)-φ c (i,t)-180° | Point P under the condition j Due to phase calculation and discretization errors, a phase tolerance threshold ε is typically set (e.g., ε = 5°). If the found point P... j Satisfy |φ c (j,t)-φ c (i,t)-180°|<ε, then determine (P) i ,P jThese constitute a valid pair of aligned points. By traversing all points or using optimization algorithms (such as avoiding duplicate pairings), we can eventually obtain the set of all aligned point number pairs at time t, such as {(P5,P65),(P6,P66),...,(Pm,Pn)}.

[0071] S324. Based on multiple pairs of aligned circular point numbers, establish a mapping function.

[0072] In this embodiment of the application, after determining the set of all aligned point number pairs at a specific time t, these specific point correspondences are associated with and encapsulated with the rotation phase data θ(t) at that time and the measurement time t itself.

[0073] Specifically, the rule describing "at a given measurement time t, when the rotation phase of the mold head is θ(t), the set of point pairs constituting the alignment relationship of the double-layer thin film is" is transformed into a function, thus forming a variable from input variables (time t, rotation phase θ) to output variable (set of alignment point pairs {(i,j)}). t The deterministic mapping relationship is established. That is, the mapping function is established: {(i,j)}= F(t,θ(t), model parameters), where the function F encapsulates all the logic of the aforementioned discretization, phase compensation and matching, and is used to connect the rotational physical motion and the mathematical point model, so that for any subsequent measurement time, the corresponding point alignment relationship can be quickly and automatically determined through this function.

[0074] To further improve the long-term stability and adaptability to production disturbances of the mapping function, after establishing the mapping function based on multiple pairs of aligned circumferential point numbers, dynamic calibration and correction steps are also included: a. Set optical markers on the surface of the tubular section (i.e. the section that still maintains the shape of a round tube) before the tubular film enters the traction flattening roller; b. Continuously capture the actual motion trajectory and position of optical markers during the thin film's movement using a high-speed industrial camera; c. Compare the captured actual position with the theoretical position predicted based on the current mapping function, traction speed and other parameters in real time, and calculate the position deviation. d. Based on the positional deviation, dynamically adjust the relevant parameters in the mapping function (e.g., fine-tune the travel time, film stretching and shrinkage coefficient, or directly compensate for the offset of the output point number pairs) to achieve online correction and optimization of the mapping function.

[0075] In this embodiment, the optical marker can be a specific pattern pre-printed on the film, or a virtual marker tracked by a machine vision algorithm using the film's natural texture. Positional deviation reflects the impact of actual production factors (such as small fluctuations in traction speed, non-uniform stretching, and airflow disturbances) not fully covered by the theoretical model. By using this deviation as a feedback signal, the mapping function can continuously adapt to the actual production state, thereby enhancing the robustness of the entire measurement system to complex operating conditions. This ensures that even during long-term operation or slow drift in process conditions, the prediction of point alignment remains highly accurate, ultimately guaranteeing the long-term reliability and accuracy of the thickness inversion results.

[0076] S33. Based on the sampling time of each data point in the double-layer thickness data sequence, query the rotation phase data at the corresponding time.

[0077] In this embodiment, the double-layer thickness data sequence is a collection arranged in chronological order, wherein each data record contains a precise sampling time timestamp t. m (Provided by the global clock of the data acquisition system) and the thickness value Y and probe position information measured at that moment. At the same time, the rotating phase sensor continuously acquires and records the rotation angle data of the mold head at the same or higher frequency, forming another time-phase sequence synchronized with the global clock. Each record contains a timestamp and the corresponding rotation angle. By successfully associating a specific spatial state parameter with each thickness measurement value, precise synchronization of physical measurement (thickness) and mechanical motion (rotation) in the time dimension is achieved.

[0078] Preferably, to accurately correlate the thickness measurement with the spatial state of the thin film, for each data point in the thickness data sequence (e.g., the m-th point), its sampling time t is used. m Used as a query key, it performs a matching query in the time-phase sequence of the rotated phase data.

[0079] It should be noted that, since the data acquisition is synchronous or near-synchronous, the phase data record with the same or closest timestamp (within an allowable small time tolerance, such as ±1 millisecond) can be directly found, and its corresponding head rotation angle can be extracted. If there are differences in the acquisition frequency, an interpolation algorithm (such as linear interpolation) can be used to calculate the precise rotation angle at each moment based on the phase data of adjacent moments.

[0080] S34. Based on the rotation phase data and mapping function at the corresponding time, obtain the alignment relationship of the circumferential points at each sampling time.

[0081] In this embodiment of the application, for each data point in the double-layer thickness data sequence, after obtaining the mold head rotation angle corresponding to its sampling time through step S33, the mold head rotation angle together with the moment itself is used as input parameters, and the mapping function F established in step S324 is called and executed.

[0082] Preferably, the internal logic of the mapping function F encapsulates a complete calculation chain from the rotation phase to the alignment relationship of discrete points on the circumference, including: determining the actual phase of the points on the die head based on the sampling time and the die head rotation angle; compensating for the travel time and stretching rate to obtain the compensated phase of the thickness gauge position; and finally determining the alignment point pair through phase matching. After executing this function, the specific circumferential point alignment relationship constituting the currently measured double-layer thickness value is directly output at that specific sampling time, i.e., one or more determined point number pairs. For example, for a certain measurement point, the output is (Pi, Pj).

[0083] Thus, each measurement in the thickness data sequence is assigned a pair of associated single-layer film point numbers, realizing the inversion from double-layer measurement to single-layer measurement.

[0084] It is worth noting that during the measurement process, because the thickness gauge probe has a specific effective measurement spot size or measurement area, when the angular spacing (i.e., 360° / N) of this spot size relative to the discrete points of the thin film is not negligible, a single thickness measurement may not correspond to only a pair of ideal, infinitesimally small point alignments, but rather cover a tiny region centered on the ideal alignment point. Within this tiny region, there may actually be partial contributions from multiple discrete points, or due to slight microscopic fluctuations, wrinkles, or alignment deviations in the thin film, the measurement spot may simultaneously cover multiple combinations of neighboring points. Therefore, to improve model accuracy and robustness, each thickness measurement value can be assigned multiple pairs of associated single-layer thin film point numbers, and each pair of points can be assigned a corresponding weighting coefficient to more realistically reflect the actual physical measurement process, enabling better modeling of spatial averaging and edge effects during the measurement process.

[0085] For example, for the measured value Y m This allows us to determine the primary associated point pairs (Pi, Pj), while also considering neighboring point pairs (Pi±1, Pj±1) as secondary associated pairs, forming a weighted association relationship, such as: { (Pi,Pj): 0.7, (Pi+1, Pj-1): 0.2, (Pi-1, Pj+1): 0.1}.

[0086] Step 104: Based on the alignment relationship of the circumferential points and the corresponding double-layer thickness data, the overdetermined observation equation set is obtained.

[0087] In this embodiment, each thickness measurement value Y_m not only has a numerical value, but is also associated with a specific circumferential point alignment relationship. Based on this, a set of mathematical equations is constructed to solve for the single-layer thickness at each point. Preferably, in order to improve the accuracy of the thickness measurement in representing the true geometric state of the thin film material, before constructing the overdetermined observation equation set based on the point alignment relationship and the original thickness data, it is necessary to first perform thermal expansion compensation correction on the double-layer thickness data sequence, specifically as follows: Real-time acquisition of temperature distribution data for the bilayer thin film at the measurement location of the thickness gauge. This can be achieved by deploying a non-contact infrared temperature sensor array near the thickness gauge to obtain the temperature profile of the film along the width of the measurement section.

[0088] Based on real-time acquired temperature distribution data and the thermal expansion coefficient γ of the thin film material pre-calibrated or obtained from a material database, the original measured values ​​in the double-layer thickness data sequence are corrected for thermal expansion compensation.

[0089] Specifically, for a given measurement value Y m Based on the real-time temperature T at its measurement location m With a set reference temperature T ref (e.g., 20℃), the compensation amount for thickness change caused by temperature can be calculated as follows:

[0090] Subtract (or add, depending on the direction of thermal expansion and contraction) this compensation amount from the original measurement to obtain the corrected double-layer thickness value. Perform this operation on all raw thickness data to obtain a corrected sequence of bilayer thickness data. This process removes the effects of physical expansion or contraction of the film caused by ambient temperature fluctuations, allowing the thickness data to more purely reflect the geometric thickness of the material itself.

[0091] In this embodiment of the application, after completing the thermal expansion compensation correction, the corrected double-layer thickness data sequence is used to construct the subsequent equation set.

[0092] Furthermore, step 104 includes the following sub-steps: S41. Define the thickness of the single-layer film corresponding to each discrete point as an unknown variable.

[0093] In step S31, the circumference of the tubular film has been divided into N discrete points. In this embodiment, an unknown variable X is defined for each discrete point Pk (k=1, 2, ..., N). k This represents the physical thickness of the single-layer film at that point, and all N unknown variables form a column vector. The core objective of the entire single-layer thickness inversion problem is to solve for this vector X containing N unknowns, where the unknown variable X is the complete thickness distribution of the film in the circumferential direction.

[0094] S42. Establish a linear equation for each pair of circumferential point alignment relationships and the corresponding double-layer thickness measurement values.

[0095] In this embodiment of the application, for each thickness measurement value Y m (or Y after thermal expansion compensation correction) m '), has matched and obtained one or more pairs of circumferential point alignment relationships associated with it.

[0096] It should be noted that the total thickness of the bilayer film should be equal to the sum of the thicknesses of the two single-layer films that make it up. Therefore, the following linear equation can be established to represent a linear constraint imposed on the unknown thickness distribution by a single independent measurement observation:

[0097] Among them, X i and X j These are the unknown variables for the single-layer thickness at corresponding points Pi and Pj, respectively, and Y. m It is the measured (or corrected) double-layer thickness value. If a measured value Y m If multiple pairs of points are associated (e.g., with weights), multiple linear equations or a weighted equation can be established (e.g., ...). However, for the sake of simplicity, we will take a pair of main related relationships as an example here.

[0098] S43. Summarize the linear equations established at all measurement times to form a system of linear equations, which serves as the overdetermined observation equation system.

[0099] In the embodiments of this application, during the continuous measurement process, measurements will be taken at different times t1, t2, ...t N ,t M (M is much larger than N) A large number of thickness measurements Y1, Y2, ..., Y are obtained. M And for each measurement, a linear equation as described above was established. Combining all M (or more, considering multi-point correlations) linear equations forms a equation concerning N unknowns X1, X2, ..., X... N The system of linear equations. Since the number of measurements M is usually much greater than the number of unknowns N, the system of equations is overdetermined, meaning that the number of equations is greater than the number of unknowns. It is called the overdetermined observation equation system, which systematically encapsulates all measurement data and the physical constraints they reflect, thus enabling the inversion of single-layer thickness.

[0100] This system of equations can be concisely represented in matrix form as follows:

[0101] Where A is an M×N coefficient matrix. For the m-th equation (corresponding to the measured value Y) m and its associated points (i,j) m The element in the m-th row of matrix A is 1 only at the positions corresponding to the i-th and j-th columns (or weight values ​​if weights are considered), and 0 at the other positions. X is the previously defined N×1 unknown single-layer thickness vector. Y is an M×1 vector composed of measured (or corrected) values. m The column vector formed by these.

[0102] Step 105: Solve the overdetermined observation equations mathematically to obtain the thickness values ​​of each single-layer point of the tubular film in the circumferential direction.

[0103] In this embodiment, a definite numerical vector is obtained by performing mathematical operations on the overdetermined observation equations using preset solution logic. Each component X of this vector... k That is, the solution value of the single-layer film thickness corresponding to the kth discrete point on the circumference. All components together constitute the complete single-layer thickness distribution profile of the tubular film in the circumferential direction, thus realizing the accurate inversion from the mixed double-layer thickness measurement data to the separated single-layer thickness at each point.

[0104] It should be noted that the pre-defined solution logic is not specifically limited here, and technical personnel can proceed based on the existing solution logic.

[0105] The implementation principle of this application embodiment is as follows: By continuously scanning the flattened double-layer film using a thickness gauge based on optical principles (such as laser, infrared, or interferometry), an easily measurable total thickness optical signal is obtained. Simultaneously, a rotating phase sensor synchronously acquires the rotational phase data of the blown film machine in real time. By establishing a dynamic mapping function between the rotational phase and discrete points on the film circumference, the alignment relationship of the specific single-layer optical points corresponding to the measured total optical thickness signal of the double-layer film at each optical measurement moment is accurately tracked and determined. Based on this, the thickness measurement value obtained by each optical thickness gauge and its associated optical point alignment relationship are transformed into a linear observation equation. By collecting a large amount of optical measurement data, an overdetermined set of observation equations is constructed, with the number of equations far exceeding the number of unknowns. Finally, by solving this overdetermined set of equations, the thickness of the single-layer film at each discrete point is inverted from a series of mixed double-layer optical thickness observation values. Thus, high-precision, non-invasive measurement of the full circumferential thickness distribution of tubular films is achieved without the need for direct optical measurement of the single-layer film. Example 2

[0106] Please see Figure 3 This application provides a material thickness measurement system for a blown film production line, comprising: A blown film machine is used to blow tubular thin films; The flattening traction unit is used to flatten the tubular film into a double-layer film when the tubular film is detected. The thickness gauge is located downstream of the flattening and traction unit and is used to continuously scan and measure the double-layer film along the film's travel direction to obtain a double-layer thickness data sequence. A rotating phase sensor is installed on the rotating parts of a blown film machine to collect rotating phase data in real time. The data processing and control unit is communicatively connected to both the thickness gauge and the rotating phase sensor, and performs the following: Receives dual-layer thickness data sequences and rotation phase data; Determine the alignment relationship of the circumferential points at each measurement time; Based on the alignment relationship of the circumferential points and the corresponding double-layer thickness data, an overdetermined observation equation set was constructed and solved. Output the thickness value of each single layer point in the circumferential direction of the tubular film.

[0107] In this embodiment, the flattening traction unit includes a pair of adjustable gap pressure rollers that receive tubular films from a blown film machine and press them into an aligned double-layer structure.

[0108] The thickness gauge is preferably a non-contact scanning thickness gauge based on optical principles such as laser, infrared or interference. Its probe moves back and forth along the width of the film under the drive mechanism to achieve continuous coverage measurement of the entire film width.

[0109] The rotary phase sensor is a high-precision encoder that is directly mounted on the rotating shaft of the blown film machine die head to ensure the accuracy and real-time performance of phase signal acquisition.

[0110] The data processing and control unit includes a data acquisition card, a processor, and a storage medium. It connects to the thickness gauge and encoder via a communication interface (such as Ethernet, fieldbus, etc.) to acquire thickness and phase data in real time. It also has a built-in algorithm program to execute a series of steps in the method embodiment, such as establishing the mapping function, compensating for thermal expansion, constructing and solving the system of equations. Finally, it outputs the thickness values ​​and distribution charts of each single-layer point through a human-machine interface or control bus, realizing a deep integration of optical measurement technology and dynamic rotation modeling.

[0111] Since the above is a system corresponding to a method for measuring the thickness of materials in a blown film production line, and its implementation principle is the same as that of a method for measuring the thickness of materials in a blown film production line, for the sake of convenience and brevity, those skilled in the art can clearly understand that the specific working process of the system and modules described above can be referred to the corresponding process in the aforementioned method embodiments, and will not be repeated here. Example 3

[0112] An electronic device according to an embodiment of the present invention includes: a memory and a processor, wherein the memory stores a computer program; when the computer program is executed by the processor, the processor performs a material thickness measurement method for a blown film production line as described in any of the above embodiments.

[0113] The memory can be an electronic memory such as flash memory, EEPROM (Electrically Erasable Programmable Read-Only Memory), EPROM, hard disk, or ROM. The memory has storage space for program code used to perform any of the method steps described above. For example, the storage space for program code may include individual program codes for implementing the various steps in the methods described above. This program code can be read from or written to one or more computer program products. These computer program products include program code carriers such as hard disks, compact discs (CDs), memory cards, or floppy disks. The program code may be compressed, for example, in a suitable form. When run by a computing processing device, this code causes the computing processing device to perform the various steps in the methods described above. Example 4

[0114] This invention provides a computer-readable storage medium storing a computer program thereon, which, when executed, implements a material thickness measurement method for a blown film production line as described in any embodiment of this invention.

[0115] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0116] In the embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection between devices or units through some interfaces, and may be electrical, mechanical, or other forms.

[0117] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0118] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0119] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0120] It should be noted that the terms "first," "second," etc., used in this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this disclosure described herein can be implemented in orders other than those illustrated or described herein. The implementations described in the following exemplary embodiments do not represent all implementations consistent with this disclosure.

[0121] Furthermore, the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article, unless otherwise specified, generally indicates that the preceding and following related objects have an "or" relationship.

[0122] The embodiments described in this specific description are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Identical components are represented by the same reference numerals. Therefore, all equivalent changes made to the structure, shape, and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for measuring the thickness of materials in a blown film production line, characterized in that, include: When the tubular film blown into shape by the blown film machine enters the traction flattening roller, the tubular film is aligned and flattened to obtain a double-layer film. Based on the aforementioned double-layer film, a thickness gauge is used to continuously scan and measure along the film's travel direction to obtain a double-layer thickness data sequence. The rotation phase data of the blown film machine is collected in real time, and the alignment relationship of the circumferential points of the double-layer film is determined based on the double-layer thickness data sequence at each thickness measurement moment. Based on the alignment relationship of the circumferential points and the corresponding double-layer thickness data, the overdetermined observation equation set is obtained; The overdetermined observation equations are solved mathematically to obtain the thickness values ​​of each single-layer point of the tubular film in the circumferential direction.

2. The method for measuring material thickness in a blown film production line according to claim 1, characterized in that, Based on the bilayer film, a thickness gauge is used to continuously scan and measure the thickness along the film's travel direction to obtain a bilayer thickness data sequence, including: The thickness gauge is driven to reciprocate scanning along the width direction of the double-layer film at a preset fixed frequency, and in each scanning cycle, samples are taken at equal intervals along the film's travel direction to obtain a set of thickness measurement points. By associating each thickness measurement point with the corresponding sampling time and the probe's position coordinates in the film width direction, a double-layer thickness data sequence is obtained.

3. The method for measuring material thickness in a blown film production line according to claim 1, characterized in that, The step of determining the circumferential alignment of the bilayer film at each thickness measurement moment based on the bilayer thickness data sequence includes: The circumference of the tubular film is divided into multiple discrete points; Establish a mapping function between the rotation phase data and the discrete point positions; Based on the sampling time of each data point in the double-layer thickness data sequence, query the rotation phase data at the corresponding time. Based on the rotation phase data at the corresponding time and the mapping function, the alignment relationship of the circumferential points at each sampling time is obtained.

4. The method for measuring material thickness in a blown film production line according to claim 3, characterized in that, The step of establishing the mapping function between the rotation phase data and the discrete point positions includes: The phase rotation data includes the mold head rotation angle; Based on the rotation angle of the die head and the total number of discrete points, determine the actual phase of each point on the die head of the blown film machine at the current moment; Based on the actual phase, and combined with the known travel time of the tubular film from the blown film die outlet to the thickness gauge measurement position, a preset film stretching ratio is used for compensation to obtain the compensated phase of the film point at the thickness gauge measurement position. The compensation phase is matched with the discrete points on the circumference of the tubular film to obtain multiple pairs of aligned circumferential point numbers. A mapping function is established based on the multiple pairs of aligned circumferential point numbers.

5. The method for measuring material thickness in a blown film production line according to claim 4, characterized in that, The process of establishing a mapping function based on the multiple pairs of aligned circumferential point numbers further includes: Optical marking points are set on the tubular section of the tubular film before it enters the traction flattening roller; Continuously capture the actual position of the optical markers; The actual position is compared with the preset theoretical position to obtain the position deviation; The mapping function is adjusted based on the positional deviation.

6. The method for measuring material thickness in a blown film production line according to claim 3, characterized in that, The process of obtaining the overdetermined observation equation set based on the alignment relationship of the circumferential points and the corresponding double-layer thickness data also includes: Real-time acquisition of temperature distribution data of the double-layer film at the measurement position of the thickness gauge; Based on the temperature distribution data and the preset material thermal expansion coefficient, the original measured values ​​in the double-layer thickness data sequence are corrected by thermal expansion compensation to obtain the corrected double-layer thickness data sequence.

7. The method for measuring material thickness in a blown film production line according to claim 3, characterized in that, Based on the alignment relationship of the circumferential points and the corresponding double-layer thickness data, the overdetermined observation equation set is obtained, including: The thickness of the single-layer film corresponding to each discrete point is defined as an unknown variable; A linear equation is established for each pair of circumferential point alignments and the corresponding double-layer thickness measurements; The linear equations established at all measurement times are summarized to form a system of linear equations, which serves as the overdetermined observation equation system.

8. A material thickness measurement system for a blown film production line, characterized in that, include: A blown film machine is used to blow tubular thin films; A flattening traction unit is used to flatten the tubular film into a double-layer film when the tubular film is detected. A thickness gauge is located downstream of the flattening and traction unit and is used to continuously scan and measure the double-layer film along the film's travel direction to obtain a double-layer thickness data sequence. A rotating phase sensor is installed on the rotating part of the blown film machine to collect rotating phase data in real time; The data processing and control unit is communicatively connected to both the thickness gauge and the rotating phase sensor, and performs the following: Receive the double-layer thickness data sequence and the rotation phase data; Determine the alignment relationship of the circumferential points at each measurement time; Based on the alignment relationship of the circumferential points and the corresponding double-layer thickness data, an overdetermined observation equation set was constructed and solved. Output the thickness value of each single layer point in the circumferential direction of the tubular film.

9. An electronic device, characterized in that, The device includes a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor causes the processor to perform the steps of the blown film production line material thickness measurement method as described in any one of claims 1-7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed, it implements the material thickness measurement method for blown film production line as described in any one of claims 1-7.

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