An on-line thickness measurement and control system for a kind of powder skin food

Abstract

The application discloses a kind of powder skin food thickness on-line measurement and control system.System includes: electromagnetic induction unit, located above or below powder skin food, for producing through powder skin food closed magnetic circuit;Detection unit is used to detect the inductance measured value of closed magnetic circuit, obtains inductance correction value to inductance measured value is temperature and humidity compensation, and according to inductance correction value calculate the thickness measured value of powder skin food;Control unit is used to generate corresponding adjustment signal according to the difference between thickness measured value and preset thickness;Adjustment unit is used to adjust slurry flow according to adjustment signal, so that the thickness of processed powder skin food is equal to preset thickness.The application can non-contact, high-precision real-time detection powder skin food thickness in processing, and can adapt to high temperature and high humidity environment, through closed-loop control significantly improve the thickness uniformity and consistency of product.

Description

Technical Field

[0001] This invention belongs to the field of automatic control technology in food processing, and more specifically, relates to an online thickness measurement and control system for rice noodle sheets. Background Technology

[0002] In traditional production, the thickness control of strip-shaped foods such as rice noodles, wheat noodles, and sweet potato starch sheets largely relies on the experience of operators, achieved through manual observation and adjustment of valves or pump speeds. This manual method suffers from low control precision, poor stability, and high scrap rates, and can no longer meet the demands of the modern food industry for high quality, high efficiency, and automated production. To replace manual labor, some automatic thickness detection and control solutions have been introduced in existing technologies, such as mechanical contact thickness gauges, optical thickness gauges, and ultrasonic thickness gauges. However, none of these can perform non-contact, high-precision online measurement of semi-transparent, highly scattering, and uneven-surfaced wet rice paste in harsh environments with high temperature, high humidity, and steam.

[0003] Mechanical contact thickness gauges require the measuring head to directly contact the product surface, making them prone to adhesion. This not only significantly affects measurement accuracy but can also damage the surface integrity. The adhered slurry necessitates frequent production interruptions for cleaning and maintenance, rendering this solution unsuitable for continuous production lines. Optical thickness gauges suffer from weak reflected signals due to the translucent and highly scattering nature of rice slurry. In the high-temperature saturated steam and diffuse condensation environment of the steaming process, the optical lens of such sensors can become contaminated and blurred within a very short time, leading to attenuation of the incident light signal, distortion of the reflected light signal, and ultimately, measurement system failure. Ultrasonic thickness gauges rely heavily on the homogeneity and stability of the propagation medium for accuracy. The non-uniformity of the steam medium in the steaming environment, along with temperature and humidity fluctuations, significantly alters the ultrasonic wave propagation speed, introducing measurement errors. Furthermore, ultrasonic waves are scattered and attenuated in the soft, non-homogeneous rice husk containing microbubbles, resulting in low detection accuracy, slow response speed, and difficulty in achieving real-time precise control.

[0004] In addition, for wide-width products (width ≥ 600mm, commonly 1500mm or even wider), the slurry is prone to uneven distribution during application due to hydrodynamic effects, resulting in a product that is "thick in the middle and thin on both sides" or has random variations in lateral thickness. This severely affects subsequent processing (such as folding and cutting) and the quality and taste of the final product. At the control level, existing automatic control schemes are mostly simple proportional-integral-derivative (PID) adjustments with fixed parameters. However, in the production of rice noodle sheets, fluctuations in raw material batches (such as viscosity and Baumé degree), ambient temperature, and humidity are common. These fluctuations pose a continuous challenge to control systems with fixed parameters, leading to decreased control performance and even system oscillations. Especially in wide-width production, how to adjust the lateral thickness distribution in real time and accurately remains a problem that current technology has not effectively solved. Summary of the Invention

[0005] The main objective of this invention is to provide an online thickness measurement and control system for rice noodle products, in order to overcome the shortcomings of the prior art.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0007] This invention provides an online thickness measurement and control system for rice noodle sheets, comprising: an electromagnetic induction unit located above or below the rice noodle sheet, used to generate a closed magnetic circuit passing through the rice noodle sheet; a detection unit, used to detect the measured inductance value of the closed magnetic circuit, perform temperature and humidity compensation on the measured inductance value to obtain an inductance correction value, and calculate the measured thickness value of the rice noodle sheet based on the inductance correction value; a control unit, used to generate a corresponding adjustment signal based on the difference between the measured thickness value and a preset thickness; and an adjustment unit, used to adjust the slurry flow rate according to the adjustment signal so that the thickness of the processed rice noodle sheet is equal to the preset thickness.

[0008] Preferably, the number of electromagnetic induction units is three or more, evenly distributed above or below the rice noodle sheet food along the width direction of the rice noodle sheet food; the adjustment unit includes a scraper, a flexible airbag, a rigid pressure plate, and a stabilizing air source; the scraper is located above the slurry forming area along the width direction of the rice noodle sheet food; the number of flexible airbags is three or more, evenly distributed above the scraper along the width direction of the rice noodle sheet food, and they are in contact with the scraper through connectors, corresponding one-to-one with the electromagnetic induction units; the rigid pressure plate is disposed above the flexible airbags; the stabilizing air source is connected to each of the flexible airbags through an independent proportional solenoid valve; wherein, the control unit is used to generate adjustment signals to control each proportional solenoid valve according to the difference between the measured thickness value at each point along the width direction of the rice noodle sheet food and the preset thickness, so as to adjust the air pressure of each flexible airbag, so that the thickness of the processed rice noodle sheet food at each point is equal to the preset thickness.

[0009] Preferably, the relationship between the pressure change of each flexible airbag located on both sides and the difference is as follows:

[0010] ;

[0011] The relationship between the pressure change of each flexible airbag located in the middle and the aforementioned difference is as follows:

[0012] ;

[0013] in, , These represent the pressure changes of each flexible airbag located on both sides, and the corresponding differences. , These represent the pressure changes of each flexible airbag located in the middle, and the corresponding differences. This is the gain coefficient. The decoupling coefficient is... , These represent the pressure changes of the flexible airbags on the left and right sides of the flexible airbag located in the middle.

[0014] Preferably, the system further includes: n micro-orifice nozzles, which are evenly distributed around the electromagnetic induction unit with the electromagnetic induction unit as the center, and the micro-orifice nozzles are oriented towards the electromagnetic induction unit at a set angle, where n≥4; during the detection process, gas is introduced into the micro-orifice nozzles to form an annular air curtain to prevent water vapor and particulate matter from contacting the electromagnetic induction unit.

[0015] Preferably, the surface of the electromagnetic induction unit is coated with a superhydrophobic anti-stick coating to prevent slurry and condensate from adhering to the surface of the electromagnetic induction unit.

[0016] Preferably, the electromagnetic induction unit includes a first iron core, a second iron core, a common magnetic yoke, a first winding wound on the first iron core, and a second winding wound on the second iron core; the cross-sectional areas of the first iron core and the second iron core parallel to the rice noodle-like food are different; the first iron core is located above or below the rice noodle-like food and is used to generate a main magnetic circuit passing through the rice noodle-like food and the common magnetic yoke; the second iron core is located in a non-detection area and is used to generate a reference magnetic circuit passing through the rice noodle-like food and the common magnetic yoke; the closed magnetic circuit includes the main magnetic circuit and the reference magnetic circuit.

[0017] Preferably, the system further includes: a temperature and humidity sensing unit for collecting ambient temperature and ambient humidity; the detection unit performs temperature and humidity compensation on the measured inductance value based on the ambient temperature and ambient humidity to obtain an inductance correction value.

[0018] ;

[0019] in, This is the inductance correction value. This is the measured value of the inductance. This is the first-order temperature compensation coefficient. This is the second-order temperature compensation coefficient. This is the first-order humidity compensation coefficient. This serves as the reference value for temperature calibration. This is the humidity calibration reference value. For ambient temperature, This refers to ambient humidity.

[0020] Preferably, the detection unit calculates the measured thickness of the rice noodle food based on the inductance correction value, specifically including: calculating the real-time thickness corresponding to the currently obtained inductance correction value according to a preset nonlinear mapping model characterizing the relationship between the inductance correction value and the thickness value; and performing first-order low-pass filtering and moving average filtering on the real-time thickness in sequence to obtain the measured thickness value.

[0021] Preferably, the nonlinear mapping model is:

[0022] ;

[0023] in, This is the inductance correction value. To fix the air gap length, This is the thickness value. The first fitted parameter is... The second fitting parameter, and The value was obtained through experimental calibration.

[0024] Preferably, the control unit generates a corresponding adjustment signal based on the difference between the measured thickness value and the preset thickness, specifically including: performing a first-order low-pass filter on the absolute value of the difference between the measured thickness value and the preset thickness to obtain a smooth thickness difference signal; and generating a corresponding adjustment signal when the smooth thickness difference signal is higher than a preset threshold and the duration reaches a set value.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: It provides an online thickness measurement and control system for rice noodle sheets, which measures and controls the thickness of samples during the processing of rice noodle sheets based on the principle of electromagnetic induction. A closed magnetic circuit driven by an electromagnetic induction unit passes through the rice noodle sheet, and the magnetic resistance of the closed magnetic circuit determines the inductance value of the coil. When the product thickness changes, it is equivalent to modulating the magnetic resistance of the "product gap" in the magnetic circuit, thereby causing a precise and measurable change in the coil inductance value. Thus, the non-electrical thickness change is converted into an electrical quantity that can be accurately collected and processed. This system can work stably and accurately in a high-temperature and high-humidity steaming environment, and can realize fully automatic and intelligent thickness detection and control. At the same time, it has the ability to solve the problem of product lateral uniformity, fundamentally improving the production quality and efficiency of rice noodle sheets. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the online thickness measurement and control system for rice noodle sheets provided in an embodiment of the present invention.

[0028] Figure 2 This is a schematic diagram of the structure of the adjustment unit provided in an embodiment of the present invention.

[0029] Figure 3 This is a schematic diagram of the distribution of micro-orifice nozzles provided in an embodiment of the present invention.

[0030] Explanation of reference numerals in the attached drawings: 100 is an electromagnetic induction unit, 201 is a proportional solenoid valve, 202 is a rigid pressure plate, 203 is a flexible airbag, 204 is a scraper, 205 is a connector, and 301 is a micro-orifice nozzle. Detailed Implementation

[0031] The following will provide a further explanation of the technical solution, its implementation process, and its principles.

[0032] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0033] Furthermore, in the description of this invention, it should be understood that the terms "upper," "lower," "inner," "outer," "horizontal," "vertical," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0034] In the description of this specification, the references to terms such as "an embodiment," "a particular embodiment," or "the embodiment" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0035] Figure 1 This is a schematic diagram of the online thickness measurement and control system for rice noodle sheets provided in an embodiment of the present invention. (See attached diagram.) Figure 1 , combined Figures 2-3 The present invention provides a detailed description of the online thickness measurement and control system for rice noodle sheets.

[0036] See Figure 1 The online thickness measurement and control system for rice noodle sheets includes an electromagnetic induction unit, a detection unit, a control unit, and an adjustment unit. The electromagnetic induction unit, located above or below the rice noodle sheet, generates a closed magnetic circuit passing through it. The detection unit detects the measured inductance of the closed magnetic circuit, performs temperature and humidity compensation to obtain an inductance correction value, and calculates the measured thickness of the rice noodle sheet based on this correction value. The control unit generates a corresponding adjustment signal based on the difference between the measured thickness and a preset thickness. The adjustment unit adjusts the slurry flow rate according to the adjustment signal to ensure the processed rice noodle sheet thickness equals the preset thickness.

[0037] The online thickness measurement and control system for rice noodle sheets provided by this invention can be used to detect and adjust the thickness of rice noodle sheets during processing, ensuring that the thickness of each part of the processed rice noodle sheet meets the expected standard. Rice noodle sheets include, but are not limited to, rice sheets, wheat sheets, and sweet potato sheets made from rice flour, wheat batter, sweet potato starch, etc., through steaming. This system can operate stably and accurately in high-temperature and high-humidity steaming environments, achieving fully automatic and intelligent thickness detection and control. It also has the ability to solve the problem of lateral uniformity in the product, fundamentally improving the production quality and efficiency of rice noodle sheets.

[0038] The core of the online thickness measurement and control system for rice noodle sheets is a closed magnetic circuit driven by an electromagnetic induction unit (e.g., an excitation coil). One part of this closed magnetic circuit consists of a magnetic core and a yoke, while the other part consists of non-magnetic, non-metallic rice noodle sheets passing through it. According to Ohm's law for magnetic circuits, the magnetic reluctance of the closed magnetic circuit determines the inductance of the coil. When the product thickness changes, it is equivalent to modulating the magnetic reluctance of the "product gap" in the magnetic circuit, thereby causing a precise and measurable change in the coil inductance. Thus, this invention converts the non-electrical thickness change into an electrical quantity that can be accurately acquired and processed.

[0039] Preferably, the number of electromagnetic induction units is three or more, and they are evenly distributed above or below the rice noodle sheet food along the width direction. This allows the detection unit to measure the thickness of the rice noodle sheet food area above or below each electromagnetic induction unit, thereby measuring the thickness of the rice noodle sheet food at different locations along the width direction and ultimately ensuring the lateral uniformity of the rice noodle sheet food.

[0040] Preferably, the regulating unit includes a scraper 204, a flexible airbag 203, a rigid pressure plate 202, and a pressure-stabilizing air source (not shown in the figure), such as Figure 2 As shown. The scraper 204 is positioned above the slurry forming area along the width direction of the rice noodle sheet. Three or more flexible airbags 203 are evenly distributed above the scraper along the width direction of the rice noodle sheet, contacting the scraper 204 via connectors 205, and corresponding one-to-one with the electromagnetic induction unit. A rigid pressure plate 202 is positioned above the flexible airbags 203. A stabilizing air source is connected to each flexible airbag 203 via an independent proportional solenoid valve 201. The control unit generates adjustment signals to control each proportional solenoid valve 201 based on the difference between the measured thickness at various points along the width direction of the rice noodle sheet and the preset thickness, thereby adjusting the air pressure of each flexible airbag 203 to ensure that the thickness of the processed rice noodle sheet is equal to the preset thickness at all points. Each flexible airbag 203 corresponds to a different control area, enabling independent adjustment of the thickness of the rice noodle sheet by zone.

[0041] A further preferred embodiment of the relationship between the pressure change and the pressure difference of each flexible airbag located on both sides is as follows:

[0042] ;

[0043] The relationship between the pressure change and the difference of each flexible airbag located in the middle is as follows:

[0044] ;

[0045] in, , These represent the pressure changes and corresponding differences for each flexible airbag located on both sides. , These represent the pressure changes and corresponding differences for each flexible airbag located in the middle. This is the gain coefficient. The decoupling coefficient is... , These represent the pressure changes of the flexible airbags on the left and right sides of the flexible airbag located in the middle.

[0046] Preferred options, please refer to Figure 3 The online thickness measurement and control system for rice noodle sheets also includes: n micro-orifice nozzles 301, evenly distributed around the electromagnetic induction unit 100, with the nozzles 301 facing the unit at a set angle, where n ≥ 4. During the detection process, gas is introduced into the micro-orifice nozzles to form an annular air curtain to prevent water vapor and particulate matter from contacting the electromagnetic induction unit. Figure 3 In the diagram, the arrows indicate the spray direction of the micro-orifice nozzles 301. Each nozzle is tilted at a set angle towards the electromagnetic induction unit 100, forming an annular air curtain. The dashed circles in the diagram represent the area of ​​effect of the annular air curtain formed by the airflow ejected from each micro-orifice nozzle. Taking n=4 as an example, the positions of the four micro-orifice nozzles are distributed as follows: Figure 3 As shown.

[0047] Preferably, the surface of the electromagnetic induction unit is coated with a superhydrophobic anti-stick coating to prevent slurry and condensate from adhering to the surface of the electromagnetic induction unit.

[0048] Preferably, the electromagnetic induction unit includes a first iron core, a second iron core, a common magnetic yoke, a first winding wound on the first iron core, and a second winding wound on the second iron core; the cross-sectional areas of the first and second iron cores parallel to the rice noodle-like food are different. The first iron core is located above or below the rice noodle-like food and is used to generate a main magnetic circuit passing through the rice noodle-like food and the common magnetic yoke. The second iron core is located in a non-detection area and is used to generate a reference magnetic circuit passing through the rice noodle-like food and the common magnetic yoke; the closed magnetic circuit includes the main magnetic circuit and the reference magnetic circuit.

[0049] Preferably, the online thickness measurement and control system for rice noodle sheets also includes: a temperature and humidity sensing unit for collecting ambient temperature and humidity data. The detection unit performs temperature and humidity compensation on the measured inductance value based on the ambient temperature and humidity to obtain the inductance correction value.

[0050] ;

[0051] in, This is the inductance correction value. This is the measured value of the inductance. This is the first-order temperature compensation coefficient. This is the second-order temperature compensation coefficient. This is the first-order humidity compensation coefficient. This serves as the reference value for temperature calibration. This is the humidity calibration reference value. For ambient temperature, This refers to ambient humidity.

[0052] Compared with other existing measurement and control methods (such as optical and ultrasonic methods), the system of the present invention has an essential and structural advantage in terms of anti-interference, which is specifically reflected in the following aspects.

[0053] (1) The system has “innate immunity” to steam and water mist.

[0054] The propagation characteristics of electromagnetic / magnetic fields in non-magnetic media (such as air, water vapor, and liquid water) are almost unaffected, which contrasts sharply with sensors that heavily rely on light or sound signals. Therefore, the high-temperature saturated steam and condensed water mist generated during the steaming process do not cause attenuation or distortion of the inductive measurement signal, unlike the attenuation of light signals or interference with sound waves. Based on this, this system can still output a stable and reliable thickness signal in dense fog environments with extremely low visibility, fundamentally solving the failure problem of optical and ultrasonic sensors.

[0055] (2) Through a triple collaborative design, the "active defense and passive inhibition" mechanism for rice / flour paste adhesion and contamination completely solves the adhesion problem of mechanical sensors and the resulting measurement drift.

[0056] Active physical isolation—air curtain protection. The annular air curtain continuously generates a clean, dry positive pressure air barrier, actively blocking most of the suspended rice / flour slurry particles and condensed water droplets outside the detection area, reducing the contact between contaminants and the magnetic pole surface of the electromagnetic induction unit from the source.

[0057] Passive surface protection—anti-stick coating. A superhydrophobic anti-stick coating (such as a superhydrophobic and oleophobic polytetrafluoroethylene coating) is applied to the magnetic pole surface of the electromagnetic induction unit. This makes it difficult for small amounts of contaminants to adhere firmly to the surface of the electromagnetic induction unit even if they break through the annular air curtain. They are easily carried away by the airflow, ensuring the long-term cleanliness of the critical measurement surfaces of the electromagnetic induction unit.

[0058] Signal drift compensation—differential magnetic circuit and environmental compensation algorithm. By setting a reference magnetic circuit, common-mode drift caused by changes in environmental temperature and humidity, mechanical vibration, etc., is sensed and compensated in real time. The temperature and humidity sensor integrated into the magnetic yoke provides real-time data, and the compensation algorithm further corrects for the remaining environmental effects.

[0059] The multi-layered, collaborative defense system of "active air curtain isolation + passive anti-stick coating + signal differential compensation" provided by the embodiments of the present invention ensures that the system can maintain measurement accuracy and stability for a long time in the rice / flour slurry environment where adhesion is very likely to occur, avoiding the problem of frequent cleaning and maintenance or even product damage caused by adhesion of mechanical contact sensors.

[0060] Preferably, the detection unit calculates the measured thickness of the rice noodle-type food based on the inductance correction value, specifically including: calculating the real-time thickness corresponding to the currently obtained inductance correction value based on a preset nonlinear mapping model characterizing the relationship between the inductance correction value and the thickness value; and performing first-order low-pass filtering and moving average filtering on the real-time thickness in sequence to obtain the measured thickness value.

[0061] A further preferred nonlinear mapping model is:

[0062] ;

[0063] in, This is the inductance correction value. To fix the air gap length, This is the thickness value. The first fitted parameter is... The second fitting parameter, and The value was obtained through experimental calibration.

[0064] Preferably, the control unit generates a corresponding adjustment signal based on the difference between the measured thickness value and the preset thickness. Specifically, this includes: performing a first-order low-pass filter on the absolute value of the difference between the measured thickness value and the preset thickness to obtain a smooth thickness difference signal; and generating a corresponding adjustment signal when the smooth thickness difference signal is higher than a preset threshold and the duration reaches a set value.

[0065] The online thickness measurement and control system for rice noodle sheets provided by this invention can non-contactly and with high precision detect the thickness of rice noodle sheets in real time. It can adapt to high temperature and high humidity environments, and through closed-loop control, it significantly improves the uniformity and consistency of product thickness, stabilizing the product thickness control accuracy within ±0.05mm, and effectively solving the problem of uneven lateral thickness. This system, through fully automatic closed-loop control, eliminates the uncertainty of manual adjustment, significantly reduces the scrap rate, and improves product quality consistency.

[0066] The technical solution of the present invention will be further described in detail below with reference to several preferred embodiments and 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. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions.

[0067] Example 1

[0068] This embodiment provides an online thickness measurement and control system for rice noodle products with differential compensation, air curtain self-monitoring, and environmental self-calibration functions. It addresses the problem of online thickness measurement in the high temperature, high humidity, and easy adhesion environment of the steaming production line, achieving a detection accuracy of ±0.10mm and long-term stable operation.

[0069] The electromagnetic induction unit is preferably installed approximately 1 meter downstream of the steam slurry machine outlet, below the conveyor belt. The advantages of this location are: the product thickness is already stable, resulting in minimal measurement error; the response time of subsequent detection, control, and adjustment units is suitable; and environmental steam impact is reduced, improving sensor lifespan. Typical operating conditions are: temperature 85±5℃, relative humidity 80±10%RH.

[0070] The electromagnetic induction unit employs a dual-E type differential magnetic circuit detection module. The dual-E type differential magnetic circuit detection module consists of a first iron core, a second iron core, a manganese-zinc high permeability shared magnetic yoke, a first winding wound on the first iron core, and a second winding wound on the second iron core, thereby generating a closed magnetic circuit.

[0071] Unlike traditional symmetrical designs, this embodiment employs an asymmetrical structure to enhance differential sensitivity and suppress zero-point drift. The main magnetic circuit is located below the conveyor belt, while the reference magnetic circuit is installed in the non-detection area. The cross-sectional area of ​​the E-type iron core column in the main magnetic circuit (parallel to the cross-sectional area of ​​the rice noodle-type food) is A1 = 120 mm². 2 Number of winding turns N1=800; Reference magnetic circuit A2=100mm 2 The number of winding turns N2 = 780. This asymmetric design causes the magnetic flux distributions of the two magnetic circuits to not completely cancel each other out, thereby increasing the slope of the differential output response to thickness changes.

[0072] The inductance L of the electromagnetic induction unit can be approximately expressed as: Where L is the coil inductance, N is the number of turns, μ is the effective permeability, and A is the effective cross-sectional area of ​​the core column. To maintain a fixed air gap length, let d represent the thickness of the rice noodle sheet. From this formula, it can be seen that when the thickness d of the rice noodle sheet changes, the inductance value L changes accordingly, thus enabling thickness detection.

[0073] When A1 > A2 and N1 ≈ N2, differential sensitivity Experimental results show that the asymmetric differential structure improves sensitivity by about 15%, and the zero-point drift of the thickness is ±0.06mm with an accuracy of ±0.20mm.

[0074] To address the issues of steam condensation and slurry adhesion on the surface of the electromagnetic induction unit under high-temperature and high-humidity slurry conditions, this embodiment incorporates a ring-shaped air curtain protective structure around the detection area. Existing detection devices typically employ closed or semi-closed protective structures. Under high-temperature and high-humidity conditions, steam easily condenses within the protective space and adheres to the probe electrode surface, causing inductance baseline drift and decreased detection sensitivity. To overcome this problem, this embodiment arranges four evenly distributed micro-orifice nozzles (0.6mm orifice diameter, tilted at 30° towards the center of the electromagnetic induction unit) around the detection area, with the nozzles spaced 90° apart, forming a ring-shaped air curtain.

[0075] Dry air is supplied after multi-stage filtration. An annular air curtain forms a stable positive pressure zone on the surface of the electromagnetic induction unit, effectively preventing suspended water vapor and slurry particles from entering the magnetic core pole area, thus avoiding condensation and adhesion. The distance between the electromagnetic induction unit and the air curtain outlet is 5-7 mm. Analysis and verification show that under the above structure and operating conditions, the influence of the air curtain on the magnetic flux distribution and inductance detection results is negligible. Actual test results show that under typical continuous operation conditions of 85±5℃ and 80±10%RH, the annular air curtain protection structure of this embodiment can significantly reduce the amount of water vapor and slurry particles adhering to the surface of the electromagnetic induction unit, thereby effectively suppressing zero-point drift and improving the long-term stability of the system. After 8 hours of continuous operation, the residual mass of contaminants on the system surface decreased from 23.5 mg to 10.5 mg, the surface contaminant mass of the electromagnetic induction unit decreased by approximately 55%, and the zero-point drift of the thickness decreased from ±0.06 mm to ±0.05 mm. After adopting the annular air curtain protection structure of this embodiment, the system maintenance cycle was extended from 2 days to 4 days, and the maintenance frequency was significantly reduced.

[0076] To further prevent slurry droplets and condensate from adhering to the magnetic core and yoke poles of the electromagnetic induction unit during the production of steamed slurry sheet, a double-layer composite anti-stick coating is applied to the poles of the magnetic core and yoke. The anti-stick coating structure includes: a bottom layer of approximately 5 μm thick fluorinated siloxane-modified primer, which forms a stable bond with the magnetic core metal surface through silicon-oxygen bonds, improving the interfacial activity and wetting properties of the pole surface and providing a stable bonding base for the upper coating; and a top layer of approximately 10 μm thick polytetrafluoroethylene sintered film with a surface energy of approximately 18 mN / m and a hydrophobic contact angle of approximately 115°, used to reduce the probability of liquid adhesion. The coating thickness is controlled within 1% of the total air gap length. Finite element simulation verification shows that within this thickness range, the impact of the anti-stick coating on magnetic flux distribution and inductance detection sensitivity is negligible and will not have a substantial impact on the thickness detection results. When the anti-stick coating and the annular air curtain protection structure are used in conjunction, the air curtain actively blocks and blows away unattached microdroplets, while the anti-stick coating inhibits the solidification of residual liquid film and slurry. Together, they form a synergistic protection mechanism, enabling the electromagnetic induction unit to operate stably for extended periods in high-temperature and high-humidity environments. With both the annular air curtain and the double-layer coating (fully protected, uncompensated) activated, after 8 hours of continuous operation, the zero-point drift of the thickness decreased from ±0.06 mm in the unprotected state to ±0.03 mm, with a contaminant residue of only 4.0 mg. The signal-to-noise ratio of the thickness output signal improved from 28.3 dB in the unprotected state to 38.5 dB, significantly enhancing the detectability of thickness changes. In high-temperature and high-humidity environments, this synergistic protection scheme significantly improves the long-term stability and anti-contamination capability of the electromagnetic induction unit, extending the system maintenance cycle from 2 days to 12 days, achieving comprehensive technical effects that are difficult to anticipate with existing technologies.

[0077] In the high-temperature and high-humidity environment of the slurry production line, the magnetic permeability μ of the magnetic core, the coil resistance R, and the air gap size all drift asynchronously with changes in temperature and humidity, leading to baseline shift and sensitivity changes in the detection inductor L. To eliminate the impact of these environmental disturbances on thickness measurement, this embodiment designs an embedded temperature and humidity detection and online compensation structure. Specifically, a digital temperature sensor and a humidity sensor are embedded inside the yoke, both of which are in the same thermal equilibrium body as the magnetic core, thereby avoiding the time lag error between environmental changes and changes in magnetic circuit parameters, and enabling real-time acquisition of the ambient temperature and relative humidity at the detection point. The compensation model is based on the engineering approximation assumption: within the typical slurry operating conditions, the change in magnetic permeability caused by temperature and humidity can be regarded as a first-order linear disturbance. The detection unit converts the measured inductance value... Before being converted into a thickness signal, the measured inductance value is compensated based on the real-time ambient temperature T and relative humidity H. Within the typical operating range of the slurry production line (85±5℃, 80±10%RH), experiments have verified that the relationship between inductance and temperature / humidity can be approximated as linear. Therefore, first-order linear compensation is performed on the measured inductance value, and the following compensation calculation is executed:

[0078] ;

[0079] To compensate for the inductance. Compensation factor. and The calibration process is as follows: Install the sensor in a controlled temperature and humidity chamber, keep the sample thickness constant, and record the temperature and humidity at different conditions. The change curve is obtained by performing linear regression on each set of data. and The sample point coverage area is T=80~90°C, H=70~90%RH. For example, the calibration results... , . , .

[0080] After 8 hours of continuous operation at 85±5℃ and 80±10%RH, the thickness measurement error of the uncompensated system was ±0.14mm. Under the above-mentioned compensation conditions, within the typical operating range, the thickness measurement error can be reduced to ±0.10mm, and the thickness zero-point drift can be reduced to ±0.02mm. Under conditions of a ±5°C temperature step change, the compensation algorithm can restore the thickness error to the allowable range of ±0.10mm within approximately 3 minutes.

[0081] Compared to traditional external temperature compensation schemes, this embodiment significantly shortens the compensation response lag time caused by environmental changes because the temperature and humidity detection points and the magnetic circuit share the same temperature and humidity, thereby improving the real-time performance of compensation and system stability. In summary, this compensation algorithm, together with the dual-E type differential magnetic circuit, forms a dual anti-interference structure: differential elimination of common-mode interference and compensation correction of residual drift, achieving thickness output under typical operating conditions.

[0082] Example 2

[0083] Building upon Example 1, this example further reveals that under conditions requiring higher precision detection (preferably better than ±0.10 mm) and with significant fluctuations in environmental parameters, such as frequent changes in steam load, batch production changes, or equipment start-up and shutdown, the temperature in the detection area can fluctuate within the range of 75~95℃, and the relative humidity can change rapidly within the range of 70~95%RH, exhibiting significant nonlinear characteristics. Within this extended operating range, the magnetic core permeability, the equivalent magnetic reluctance of the air gap, and the coil resistance undergo coupled changes with temperature and humidity, causing the relationship between the total magnetic reluctance and inductance of the magnetic circuit to no longer satisfy a single linear approximation. Simultaneously, there is a proportional change relationship between the magnetic reluctance change corresponding to the product thickness and the fixed air gap magnetic reluctance, resulting in a nonlinear shift in the mapping relationship between thickness and inductance. Therefore, within the range of environmental fluctuations, the compensation method based on the first-order linear model is insufficient to completely eliminate inversion errors, especially with systematic deviations easily occurring at both ends of the measurement range. This embodiment, while maintaining the hardware structure of Embodiment 1, introduces a nonlinear inversion model based on the physical mechanism of magnetic circuits at the thickness inversion model level, and superimposes a dynamic environmental compensation algorithm on it to correct the systematic inversion deviation across the entire range. At the same time, it enhances the model's adaptability to temperature and humidity fluctuations, thereby further improving the thickness calculation accuracy without increasing hardware complexity.

[0084] Example 2 no longer uses inductance drift as the compensation object, but instead uses the total magnetic reluctance of the magnetic circuit as the modeling object. Based on treating the fixed air gap magnetic reluctance in the magnetic circuit as a constant, the magnetic reluctance component that varies with product thickness is modeled, and combined with a nonlinear correction term, a physical inversion of the product thickness is achieved. According to Ohm's law for magnetic circuits, inductance is inversely proportional to the total magnetic reluctance of the magnetic circuit. The total magnetic reluctance of the magnetic circuit mainly consists of the fixed air gap magnetic reluctance and the equivalent magnetic reluctance introduced by the material of the tested product. The iron core magnetic reluctance is relatively small and can be ignored in the modeling. For non-magnetic materials (such as rice noodles, rice vermicelli, and wheat noodles), their equivalent magnetic reluctance is approximately linearly related to the thickness, as follows:

[0085] ;

[0086] Considering factors such as edge effects, temperature nonlinearity, and magnetic flux leakage, a correction coefficient is introduced to derive the nonlinear model used in this embodiment:

[0087] ;

[0088] Under conditions of 75–95°C and 70–95%RH, calibration was performed using standard silicone samples with a thickness of 0.5–3.0 mm. α and β were obtained using a nonlinear fitting algorithm. Experimental results show that, within the full measurement range, the linear thickness inversion model in Example 1 exhibits systematic deviations at both ends of the range. The nonlinear model used in this example effectively eliminates these deviations, reducing the maximum inversion error across the full range from approximately ±0.10 mm to approximately ±0.05 mm, and resulting in a more uniform error distribution.

[0089] Furthermore, this embodiment proposes a dynamic nonlinear environment compensation algorithm:

[0090] ;

[0091] The detection unit calls upon temperature and humidity sensor data in real time and dynamically calculates based on the above model. This achieves nonlinear coupling compensation for temperature and humidity. The compensation algorithm runs within the main processor of the detection unit in a software logic embedded manner, achieving both real-time performance and stability through data caching and interpolation lookup table technology. The dynamic compensation method establishes a piecewise nonlinear compensation model within a temperature range of 80~95℃ and a humidity range of 70~95%RH. The system automatically selects the corresponding compensation interval based on the real-time collected temperature and humidity data. Within the above environmental range, when the working environment experiences temperature fluctuations of no more than ±5℃ and humidity fluctuations of no more than ±10%RH around any stable operating point, the nonlinear inversion and dynamic compensation algorithm of Example 2 can stably control the thickness measurement error within ±0.05mm.

[0092] Inductance value after temperature and humidity compensation The detection unit is based on a nonlinear model Real-time inversion thickness can be quickly calculated using table lookup and linear interpolation. After obtaining the real-time thickness signal, it is filtered by a first-order low-pass filter and a 5-point moving average filter.

[0093] ;

[0094] The thickness value output after filtering fluctuates less than ±0.03mm.

[0095] Under rice production conditions, the dynamic nonlinear compensation model of Example 2 can significantly improve measurement accuracy without changing the hardware structure, as shown in Table 1. The temperature and humidity drift of Example 1 can reach ±0.02mm under typical operating conditions, but expands to ±0.04mm across the entire operating range (75~95℃, 70~95%RH). Example 2, through nonlinear dynamic compensation, can still maintain a drift level of ±0.02mm across the entire operating range, demonstrating its wide-range adaptability advantage. The signal-to-noise ratio in Table 1 is the equivalent signal-to-noise ratio calculated based on the thickness output signal, used to characterize the overall output stability of the system after compensation and filtering.

[0096] Table 1. System performance in Examples 1 and 2

[0097]

[0098] Compared to traditional single-magnetic-circuit inductive detectors, Example 1, through the synergistic design of an asymmetric differential magnetic circuit, air curtain protection, and anti-stick coating, achieved an online thickness detection accuracy of ±0.10mm for the first time in the high-temperature and high-humidity rice noodle production environment. This significantly improved the system's anti-interference capability and maintenance cycle, meeting the needs of industrial production. Example 2 is introduced when the assumptions of Example 1 are not met. Example 2 is suitable for complex operating conditions with rapid temperature and humidity fluctuations or significant nonlinearity. By introducing a nonlinear thickness-inductance model based on physical mechanisms and a dynamic temperature and humidity compensation algorithm, Example 2 further reduces the thickness detection error to within ±0.05mm, making it suitable for high-end rice noodle production scenarios with high requirements for product thickness consistency. Example 2 is suitable for complex operating conditions with rapid temperature and humidity fluctuations or significant nonlinearity.

[0099] Example 3

[0100] The online thickness measurement and control system for rice noodle sheets provided in this embodiment, based on embodiment 2, achieves closed-loop adjustment and control of the lateral thickness of rice noodle sheets through multi-point zone detection and flexible zone execution mechanism.

[0101] Along the width of the rice noodle food, at least three electromagnetic induction units as shown in Example 2 are arranged, corresponding to the left, middle and right control areas respectively, to realize real-time detection of the thickness values ​​of the left area, the middle area and the right area.

[0102] The regulating unit employs a three-section pneumatic flexible diversion scraper mechanism, installed at the outlet of the slurry distribution device at the feed inlet of the forming unit. This three-section pneumatic flexible diversion scraper mechanism is the core actuator in this embodiment, comprising: ① a scraper body made of 2.0mm thick, 1500mm long stainless steel elastic strip with a PTFE anti-stick coating; ② a pneumatic actuator unit, with a flexible airbag as an actuator in three areas (approximately 500mm each) along the back of the scraper, on the left, middle, and right sides. A rigid pressure plate is positioned above the flexible airbag, and it contacts the scraper via a connector below; ③ an air circuit unit, with each flexible airbag connected to an independent proportional solenoid valve. All three valves share a regulated air source (0.5~0.6MPa). The proportional solenoid valve has a response time of less than 0.2s and a control pressure range of 0.05~0.30MPa.

[0103] The working principle of the adjustment unit is as follows: when air pressure is applied to the airbag in a certain area, the airbag expands and pushes the scraper section downward through the pressure plate, forming a local deflection. As a result, the discharge gap in that area is reduced, the slurry flow is obstructed, and the thickness of the finished product in the corresponding area is reduced. Conversely, when the air pressure is reduced, the scraper rebounds under its own elasticity, the gap increases, the slurry flow increases, and the finished product becomes thicker.

[0104] A quantitative relationship model of "pressure change - scraper deflection - thickness change" was established through calibration experiments. This model was pre-installed in the detection unit to convert the thickness deviation into a precise pressure adjustment.

[0105] The control unit adopts a multi-input multi-output partitioned decoupled control strategy, combined with the temperature and humidity compensation algorithm and real-time filtering mechanism of Example 2. The specific process is as follows: The thickness values ​​of the left, middle and right regions of the rice noodle sheet food are measured in real time. The algorithm of Example 2 is used for signal filtering and environmental compensation to ensure the accuracy of the input signal. Then, the deviation between the thickness value of each region and the preset thickness (target thickness) is calculated. The deviation signal is subjected to first-order low-pass digital filtering to filter out smooth fluctuations. A dead zone threshold (e.g., ±0.03mm) is set. Adjustment is only triggered when the filtered deviation continuously exceeds the threshold and remains for a certain period of time (e.g., 3 seconds) to avoid frequent system oscillations.

[0106] To prevent coupling interference to other regions when adjusting one region, this embodiment adopts a decoupling control strategy based on feedforward compensation, with basic proportional control:

[0107] ;

[0108] in, For example, the gain coefficient. .

[0109] When both sides require opposite adjustments simultaneously (e.g., the left side needs to be thickened while the right side needs to be thinned), a decoupling algorithm is introduced to constrain the output of the middle region in order to avoid excessive impact on the middle region:

[0110] ;

[0111] in, This is the decoupling coefficient, used to weaken the coupling effect and maintain the relative stability of the total slurry flow rate, for example... .

[0112] The calculated three air pressure adjustment values ​​are output to the corresponding proportional solenoid valves to adjust the airbag pressure, completing one control cycle. The control frequency is set to 1~2Hz to ensure a balance between response speed and system stability. The control unit outputs a pulse width modulation signal to drive the proportional valves, realizing airbag pressure adjustment and dynamic fine-tuning of the scraper.

[0113] The verification was conducted under the following production conditions: steaming line width 1500mm, conveyor belt speed 3.0m / min, target thickness 1.00mm, ambient temperature 80±5℃, and ambient humidity 75~85%RH. The experimental results are as follows: Under the traditional manual adjustment scheme, the lateral thickness range (maximum-minimum) is 0.25-0.40mm, the standard deviation of lateral thickness under stable conditions is 0.08mm, the recovery time for simulated lateral disturbances is greater than 20min and requires manual intervention, and the scrap rate due to lateral unevenness is approximately 20%. In Example 3, the lateral thickness range (maximum-minimum) is ≤0.15mm, uniformity is improved by more than 60%, the standard deviation of lateral thickness under stable conditions is 0.03mm, product consistency is significantly improved, the recovery time for simulated lateral disturbances is approximately 2min and can be completed fully automatically, the scrap rate due to lateral unevenness is <1.5%, and the economic benefits are significant.

[0114] When a simulated scenario occurs where insufficient slurry supply on the right side leads to a thinner thickness, the system detects the deviation within 45 seconds and automatically increases the pressure of the right-side airbag by approximately 0.02 MPa. Within 90 seconds, the thickness on the right side is restored from 0.82 mm to 0.99 mm. The entire process requires no manual intervention, and the impact on the thickness of the left and center regions is less than ±0.02 mm. Through zoned closed-loop control, the lateral thickness variation of wide-width products is reduced from ±0.25 mm to ±0.10 mm, improving lateral uniformity. The control response is faster, automatically restoring the target thickness within 90 seconds, avoiding manual delays. The system is stable and reliable, with no mechanical wear on the pneumatic structure and a long operating cycle. It has high environmental adaptability, operating stably even in high-temperature and high-humidity slurry steaming environments. It has high industrial application value, a simple structure, is easy to retrofit existing production lines, and its cost is lower than similar vision inspection solutions.

[0115] Based on Examples 1 and 2, this embodiment constructs a complete closed-loop control system from high-precision thickness detection to intelligent signal compensation to lateral partitioning execution. The actuator structure is simple, easy to modify, and cost-effective. This system is the first to achieve lateral self-uniform control based on multi-point inductive detection and a flexible actuator in a food steaming process. It represents an innovative integration of electromechanical control and food processing, demonstrating significant technological advancement and industrial application value.

[0116] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. An online thickness measurement and control system for rice noodle sheets, characterized in that, include: An electromagnetic induction unit, located above or below the rice noodle sheet food, is used to generate a closed magnetic circuit passing through the rice noodle sheet food. The detection unit is used to detect the measured inductance value of the closed magnetic circuit, perform temperature and humidity compensation on the measured inductance value to obtain an inductance correction value, and calculate the measured thickness value of the rice noodle food based on the inductance correction value. The control unit is used to generate a corresponding adjustment signal based on the difference between the measured thickness value and the preset thickness. An adjustment unit is used to adjust the slurry flow rate according to the adjustment signal so that the thickness of the processed rice noodle food is equal to the preset thickness. The number of electromagnetic induction units is three or more, and they are evenly distributed above or below the rice noodle sheet food along the width direction of the rice noodle sheet food. The adjustment unit includes a scraper, flexible airbags, a rigid pressure plate, and a pressure-stabilizing air source. The scraper is located above the slurry forming area along the width direction of the rice noodle sheet food. There are three or more flexible airbags, which are evenly distributed above the scraper along the width direction of the rice noodle sheet food and are in contact with the scraper through connectors, corresponding one-to-one with the electromagnetic induction unit. The rigid pressure plate is located above the flexible airbags. The pressure-stabilizing air source is connected to each of the flexible airbags through an independent proportional solenoid valve. The control unit is used to generate adjustment signals for controlling each proportional solenoid valve according to the difference between the measured thickness of each part of the width direction of the rice noodle sheet food and the preset thickness, so as to adjust the air pressure of each flexible airbag and make the thickness of each part of the processed rice noodle sheet food equal to the preset thickness. The electromagnetic induction unit includes a first iron core, a second iron core, a common magnetic yoke, a first winding wound on the first iron core, and a second winding wound on the second iron core; the cross-sectional areas parallel to the rice noodle food in the first iron core and the second iron core are different; The first iron core is located above or below the rice noodle-like food, and is used to generate a main magnetic circuit passing through the rice noodle-like food and the shared magnetic yoke; The second iron core is located in the non-detection area and is used to generate a reference magnetic circuit that passes through the rice noodle food and the shared magnetic yoke; the closed magnetic circuit includes the main magnetic circuit and the reference magnetic circuit.

2. The online thickness measurement and control system for rice noodle sheets according to claim 1, characterized in that, The relationship between the pressure change of each flexible airbag located on both sides and the aforementioned difference is as follows: ； The relationship between the pressure change of each flexible airbag located in the middle and the aforementioned difference is as follows: ； in, , These represent the pressure changes of each flexible airbag located on both sides, and the corresponding differences. , These represent the pressure changes of each flexible airbag located in the middle, and the corresponding differences. This is the gain coefficient. The decoupling coefficient is... , These represent the pressure changes of the flexible airbags on the left and right sides of the flexible airbag located in the middle.

3. The online thickness measurement and control system for rice noodle sheets according to claim 1, characterized in that, The system further includes: n micro-orifice nozzles, which are evenly distributed around the electromagnetic induction unit with the electromagnetic induction unit as the center, and the micro-orifice nozzles are oriented towards the electromagnetic induction unit at a set angle, where n≥4; During the detection process, gas is introduced into the microporous nozzle to form an annular air curtain to prevent water vapor and particulate matter from contacting the electromagnetic induction unit.

4. The online thickness measurement and control system for rice noodle sheets according to claim 1, characterized in that, The surface of the electromagnetic induction unit is coated with a superhydrophobic anti-stick coating to prevent slurry and condensate from adhering to the surface of the electromagnetic induction unit.

5. The online thickness measurement and control system for rice noodle sheets according to claim 1, characterized in that, The system also includes: a temperature and humidity sensing unit, used to collect ambient temperature and ambient humidity; The detection unit performs temperature and humidity compensation on the measured inductance value based on the ambient temperature and humidity to obtain the inductance correction value: ； in, This is the inductance correction value. This is the measured value of the inductance. This is the first-order temperature compensation coefficient. This is the second-order temperature compensation coefficient. This is the first-order humidity compensation coefficient. This serves as the reference value for temperature calibration. This is the humidity calibration reference value. For ambient temperature, This refers to ambient humidity.

6. The online thickness measurement and control system for rice noodle sheets according to claim 1, characterized in that, The detection unit calculates the measured thickness of the rice noodle-type food based on the inductance correction value, specifically including: Based on a preset nonlinear mapping model representing the relationship between inductance correction value and thickness value, the real-time thickness corresponding to the currently obtained inductance correction value is calculated. The real-time thickness is subjected to first-order low-pass filtering and moving average filtering in sequence to obtain the measured thickness value.

7. The online thickness measurement and control system for rice noodle sheets according to claim 6, characterized in that, The nonlinear mapping model is as follows: ； in, This is the inductance correction value. To fix the air gap length, This is the thickness value. The first fitted parameter is... The second fitting parameter, and The value was obtained through experimental calibration.

8. The online thickness measurement and control system for rice noodle sheets according to claim 1, characterized in that, The control unit generates a corresponding adjustment signal based on the difference between the measured thickness value and the preset thickness, specifically including: The absolute value of the difference between the measured thickness and the preset thickness is subjected to a first-order low-pass filter to obtain a smooth thickness difference signal. When the smooth thickness difference signal is higher than a preset threshold and the duration reaches a set value, a corresponding adjustment signal is generated.

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