Resin infusion multi-point monitoring system based on ultrasonic echo attenuation and reference correction

Abstract

The present application relates to the technical field of composite vacuum infusion, and particularly relates to a resin infusion multi-point monitoring system based on ultrasonic echo attenuation and benchmark correction, which comprises an ultrasonic emission and reception module, a multiplexer, a vacuum negative pressure acquisition module for acquiring the vacuum negative pressure value of the whole mold cavity, an infiltration identification module for determining the resin infiltration state of the fiber preform in the mold cavity, an angle acquisition module for detecting the bending angle of the mold to be infused, a negative pressure control module for determining the pumping pressure, and a global flow analysis module for determining the resin-based composite material starting infiltration time and the resin-based composite material flow rate. The present application solves the problem that the subsequent destructive modification of the mold, such as drilling, cannot accurately monitor the infusion process by using ultrasonic detection to monitor the resin infusion of the mold with a bending angle and adjusting the mold bending angle and the vacuum negative pressure value.

Description

Technical Field

[0001] This invention relates to the field of composite material vacuum infusion technology, and in particular to a multi-point monitoring system for resin infusion based on ultrasonic echo attenuation and reference correction. Background Technology

[0002] Resin-based composite materials are high-performance materials formed by adding reinforcing materials such as glass fiber, carbon fiber, and aramid fiber to the resin matrix. Their characteristics include lightweight and high strength, corrosion resistance, high design flexibility, and fatigue resistance, leading to their widespread application in various fields. Vacuum infusion is a closed-mold composite material manufacturing technology. Its core principle is to uniformly infuse resin into pre-laid reinforcing materials using vacuum negative pressure, achieving efficient wetting. However, the timing of opening the injection valve directly affects the resin flow behavior and fiber wetting effect. Opening the valve too early or too late can lead to critical defects in the composite material, such as bubbles, dry spots, and uneven resin distribution.

[0003] Chinese Patent Publication No. CN118456916A discloses a fully automated vacuum infusion method and system for wind turbine blades, including: vacuum infusion preparation, vacuum decompression and resin infusion of wind turbine blades, monitoring of resin flow direction and resin curing degree of wind turbine blades. This invention uses a carbon nanotube sensing layer integrated with an electrical conductivity tomography method to monitor the resin infusion process of wind turbine blades, achieving high-precision imaging of the infusion area and accurately reflecting the detailed changes in the infusion process. It uses an infrared thermal imager to achieve non-contact measurement of the wind turbine blade surface temperature, establishes a heat conduction model, estimates the internal temperature of the blade in real time based on the surface temperature, and establishes a Kalman filter equation to more accurately estimate the degree of resin curing of the wind turbine blades, allowing for timely adjustment of energy consumption during the wind turbine blade curing process and reducing production costs.

[0004] It is evident that the existing technology has the following problems: when monitoring resin injection at multiple points, the lack of a monitoring system that prevents damage during resin injection into molds with bending angles leads to subsequent destructive modifications to the mold, such as drilling, resulting in mold structural damage or air leakage. Summary of the Invention

[0005] Therefore, the present invention provides a resin injection multi-point monitoring system based on ultrasonic echo attenuation and reference correction, which overcomes the problem in the prior art that when performing multi-point monitoring of resin injection, the lack of a monitoring system that does not damage the mold with bending angle during resin injection leads to subsequent destructive modifications to the mold, such as drilling, resulting in mold structure damage or air leakage.

[0006] To achieve the above objectives, the present invention provides a multi-point monitoring system for resin infusion based on ultrasonic echo attenuation and reference correction, comprising: An ultrasonic transmitter and receiver module is installed at various monitoring points on the outer wall of the mold to be injected, and is used to transmit ultrasonic waves to the mold and collect the ultrasonic echoes at the corresponding points. A multiplexer is connected to the ultrasonic transmitter and receiver module to achieve multi-point ultrasonic polling acquisition; Vacuum negative pressure acquisition module, which is used to acquire the overall vacuum negative pressure value of the mold cavity; The signal reference correction module is used to calibrate the ultrasonic static reference signal of each monitoring point in the dry reference state after the vacuum negative pressure value has stabilized, and to calculate the noise standard deviation corresponding to each monitoring point. The impregnation identification module determines the resin impregnation state of the fiber preform inside the mold cavity based on the difference between the real-time echo amplitude of each monitoring point and the corresponding ultrasonic static reference signal. Angle acquisition module, which is used to detect the bending angle of the mold to be poured; The global flow analysis module determines the initiation time of the resin-based composite material based on the relationship between the difference and the noise threshold, and determines the flow velocity of the resin-based composite material based on the difference in the infiltration time sequence of each monitoring point and the distance between each monitoring point, wherein the noise threshold is determined according to the noise standard deviation. The polling acquisition cycle is the total time for the multiplexer to complete one round of sensor ultrasonic signal acquisition.

[0007] Furthermore, the resin infusion multi-point monitoring system also includes: The negative pressure control module determines the suction pressure based on the comparison between the vacuum negative pressure value and the preset target negative pressure, so as to stabilize the negative pressure fluctuation within the preset negative pressure fluctuation threshold range. The immersion start control module is used to control the opening of the glue injection pipeline after the ultrasonic static reference signal of each monitoring point has been calibrated and the vacuum negative pressure in the mold cavity has been stabilized and reached the standard. An ultrasonic polling acquisition control module determines the polling acquisition cycle based on the flow velocity; A flow rate control module controls the opening degree of the injection valve for the resin-based composite material based on the flow rate and the bending angle of the mold.

[0008] Furthermore, the signal reference correction module includes: The dry-state reference acquisition submodule is used to acquire and calibrate the ultrasonic static reference signal at each monitoring point in the dry-state reference state after the vacuum negative pressure value has stabilized. The noise parameter calculation submodule is used to calculate the noise standard deviation corresponding to each monitoring point based on the calibrated ultrasonic static reference signal of each monitoring point.

[0009] Furthermore, the impregnation identification module determines the resin impregnation state based on the difference between the real-time echo amplitude and the corresponding ultrasonic static reference signal, combined with a noise threshold. Based on the difference being less than or equal to the noise threshold, the resin impregnation state is determined to be an unimpregnated state. Based on the difference being greater than the noise threshold and less than the preset first amplitude threshold, the resin impregnation state is determined to be a semi-impregnation transition state. Based on the difference being greater than or equal to a preset first amplitude threshold, the resin impregnation state is determined to be a fully impregnated state. The noise threshold is three times the noise standard deviation, and the first amplitude threshold is used to characterize the critical value of the ultrasonic echo difference corresponding to the air in the mold cavity fiber preform being filled with resin-based composite material.

[0010] Furthermore, the global flow analysis module includes an immersion initiation time extraction submodule, which records the infiltration initiation time of the resin-based composite material at any monitoring point as the immersion initiation time of the resin-based composite material at the corresponding monitoring point based on the echo amplitude difference being greater than the noise threshold. The echo amplitude difference is determined based on the real-time echo amplitude and the ultrasonic static reference signal at each monitoring point to determine the initial time when the resin-based composite material arrives at each monitoring point.

[0011] Furthermore, the global flow analysis module also includes: The flow time difference calculation submodule determines the flow duration of the resin-based composite material between adjacent monitoring points based on the wetting start time of adjacent monitoring points. The resin flow rate calculation submodule determines the flow rate of the resin-based composite material based on the monitoring distance between each monitoring point and the flow duration.

[0012] Furthermore, the negative pressure control module increases the pumping pressure based on the difference between the preset target negative pressure and the vacuum negative pressure value when the vacuum negative pressure value is less than the preset target negative pressure value, so as to make the vacuum negative pressure value reach the immersion start requirement; when the vacuum negative pressure value is greater than or equal to the preset target negative pressure, it maintains the current pumping pressure to keep the negative pressure fluctuation stable. The preset target negative pressure is determined based on the bending angle, and the preset target negative pressure is positively correlated with the bending angle.

[0013] Furthermore, the ultrasonic polling acquisition control module determines the polling acquisition cycle based on the flow velocity, wherein the polling acquisition cycle is negatively correlated with the flow velocity.

[0014] Furthermore, the flow rate control module increases the opening of the injection valve based on the difference between the minimum value of the preset standard flow rate range and the flow rate when the flow rate is less than the minimum value of the preset standard flow rate range, thereby accelerating the filling rate of the resin-based composite material; maintains the current injection valve opening based on the flow rate within the preset standard flow rate range, thereby maintaining the current filling rate; and decreases the injection valve opening based on the difference between the flow rate and the maximum value of the preset standard flow rate range when the flow rate is greater than the maximum value of the preset standard flow rate range, thereby reducing the filling rate of the resin-based composite material. The preset standard flow rate range is determined based on the viscosity of the resin-based composite material.

[0015] Furthermore, after the flow rate control module determines the opening degree of the injection valve based on the flow rate, it further determines the opening degree of the injection valve by combining the bending angle of the mold. The opening degree of the glue injection valve is positively correlated with the bending angle of the mold.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: In implementation, by collecting ultrasonic echoes from the outer wall of the mold, destructive modifications such as drilling can be avoided, thus preventing damage to the mold structure or the risk of air leakage. When collecting ultrasonic static reference signals, by collecting ultrasonic static reference signals at each monitoring point multiple times under stable vacuum negative pressure conditions, ultrasonic static reference signals can be obtained more accurately to accurately identify the subsequent resin impregnation state, avoiding acquisition errors caused by random circuit noise, environmental airflow disturbances, and instantaneous ultrasonic emission fluctuations. By combining the bending angle of the mold to be poured with the flow rate and suction pressure, the impregnation state of the mold cavity with the bending angle can be accurately monitored, so that the resin-based composite material can completely impregnate the mold cavity.

[0017] Furthermore, during implementation, the negative pressure control module determines the suction pressure based on the comparison between the vacuum negative pressure value and the preset target negative pressure. This ensures that the negative pressure fluctuation remains stable within the preset negative pressure fluctuation threshold range, avoiding frequent speed adjustments and start-stop cycles of the vacuum pump. Simultaneously, it maintains a constant pressure difference within the mold cavity, ensuring consistent compaction within the fiber preform. The ultrasonic polling acquisition control module adaptively matches the polling acquisition cycle of the multiplexer based on the real-time flow rate of the resin-based composite material. The polling acquisition cycle is negatively correlated with the flow rate; when the resin-based composite material flows at a higher speed, the flow front advances faster within the mold cavity, resulting in a more consistent wetting state at each monitoring point. The rapid changes in flow rate mean that if a fixed and long polling acquisition cycle is still used, the ultrasonic signal sampling will lag, making it impossible to accurately capture the brief semi-permeation transition process at the monitoring point. This can lead to missed or false judgments of the wetting state. Therefore, shortening the polling acquisition cycle increases the sampling frequency of ultrasonic signals at each monitoring point, enabling real-time and accurate tracking of the dynamic changes in the flow front of the resin-based composite material. Conversely, when the flow rate of the resin-based composite material is slow, the changes in the resin wetting state inside the cavity are gradual, and high-frequency sampling monitoring is not required. Accordingly, the polling acquisition cycle is extended to reduce frequent switching of the multiplexer and high-frequency data processing, effectively reducing the hardware load and power consumption of the entire monitoring system.

[0018] Furthermore, in implementation, by acquiring and calibrating the ultrasonic static reference signal under dry reference conditions through the dry reference acquisition submodule, the true ultrasonic echo amplitude under dry reference conditions can be accurately obtained. This avoids the impact of fluctuations caused by sudden and accidental factors such as transient electromagnetic interference, slight mold vibration, and short-term airflow impact on the accuracy of ultrasonic echo amplitude. The noise parameter calculation submodule can characterize the degree of noise signal fluctuation by calculating the noise standard deviation to accurately distinguish between equipment circuit noise, invalid signal fluctuations caused by environmental disturbances, and changes in the true ultrasonic echo amplitude caused by the impregnation of resin-based composite materials.

[0019] Furthermore, in implementation, by determining the noise threshold using three times the noise standard deviation, the resin impregnation state can be more accurately determined. Based on the difference being less than or equal to the noise threshold, the resin impregnation state is determined to be unimpregnated. This avoids the random noise caused by equipment circuit noise, mold vibration, and airflow disturbance reducing the accuracy of resin impregnation state determination. Based on the difference being greater than the noise threshold but less than the preset first amplitude threshold, the resin impregnation state is determined to be a semi-impregnation transition state. This enables accurate judgment of the impregnation effect of resin-based composite materials, improving the accuracy and sensitivity of resin-based composite material impregnation identification.

[0020] Furthermore, in implementation, the negative pressure control module increases the suction pressure based on the difference between the vacuum negative pressure value and the preset target negative pressure value, which ensures that the fiber preform is fully compacted, improves the flow uniformity of the resin-based composite material, and avoids the preform being squeezed and deformed and the layup collapsing due to excessive vacuum negative pressure. The preset target negative pressure is positively correlated with the bending angle, which can also prevent the preform from being squeezed and deformed and the layup from collapsing due to excessive vacuum negative pressure, and prevent the accumulation of resin-based composite material and the phenomenon of insufficient glue at the bending position.

[0021] Furthermore, in implementation, based on the flow rate being less than the minimum value of the preset standard flow rate range, the opening of the injection valve is increased according to the difference between the minimum value of the preset standard flow rate range and the flow rate to accelerate the filling rate of the resin-based composite material. This can quickly increase the flow rate and filling rate of the resin-based composite material, making the flow rate match the vacuum negative pressure value, and avoiding a slow resin filling rate that would lead to delayed curing of the resin-based composite material and excessive filling time, thus reducing filling efficiency. Based on the flow rate being greater than the maximum value of the preset standard flow rate range, the opening of the injection valve is decreased according to the difference between the flow rate and the maximum value of the preset standard flow rate range to reduce the filling rate of the resin-based composite material. This can ensure the flow state of the resin-based composite material and avoid eddies at the bends and corners of the mold caused by excessively fast flow of the resin-based composite material, which could lead to bubbles and reduce film quality.

[0022] Furthermore, in implementation, after the flow rate control module determines the opening of the injection valve based on the flow rate, it further determines the opening of the injection valve based on the bending angle of the mold. This allows for a secondary adjustment of the injection valve opening based on the mold angle, resulting in more precise control of the flow rate of the resin-based composite module. This avoids the defects caused by excessively fast flow rates that can trap air and form bubbles, leading to uneven wetting of localized resin-based composite materials. Attached Figure Description

[0023] Figure 1 This is a block diagram of the resin infusion multi-point monitoring system described in this embodiment; Figure 2 This is a block diagram of the signal reference correction module described in this embodiment; Figure 3 This is a block diagram of the global flow analysis module described in this embodiment; Figure 4 This is a flowchart illustrating the process by which the flow rate control module controls the flow rate in this embodiment. Detailed Implementation

[0024] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0025] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0026] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate the direction or positional relationship, are based on the direction or positional relationship shown in the drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0027] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0028] Please see Figure 1 The diagram shown is a block diagram of the resin infusion multi-point monitoring system described in this embodiment. This embodiment of the invention provides a resin infusion multi-point monitoring system based on ultrasonic echo attenuation and reference correction, comprising: An ultrasonic transmitter and receiver module is installed at various monitoring points on the outer wall of the mold to be injected. It is used to transmit ultrasonic waves to the mold and collect the ultrasonic echoes at the corresponding points. A multiplexer is connected to the ultrasonic transmitter and receiver module to achieve multi-point ultrasonic polling acquisition; Vacuum negative pressure acquisition module, which is used to acquire the overall vacuum negative pressure value of the mold cavity; The signal reference correction module is used to calibrate the ultrasonic static reference signal of each monitoring point in the dry reference state after the vacuum negative pressure value has stabilized, and to calculate the noise standard deviation corresponding to each monitoring point. The impregnation identification module determines the resin impregnation state of the fiber preform inside the mold cavity based on the difference between the real-time echo amplitude of each monitoring point and the corresponding ultrasonic static reference signal. Angle acquisition module, which is used to detect the bending angle of the mold to be poured; The global flow analysis module determines the initiation time of the resin-based composite material based on the relationship between the difference and the noise threshold, and determines the flow velocity of the resin-based composite material based on the difference in the infiltration time sequence of each monitoring point and the distance between each monitoring point, wherein the noise threshold is determined according to the noise standard deviation. The polling acquisition cycle is the total time for the multiplexer to complete one round of sensor ultrasonic signal acquisition.

[0029] In this embodiment of the invention, the resin-based composite material is a composite material formed by adding reinforcing materials to a resin matrix. It can be understood that the reinforcing materials are determined according to the usage requirements. In this embodiment of the invention, the reinforcing materials include glass fiber, carbon fiber and aramid fiber.

[0030] When fixing the ultrasonic transmitting and receiving module to the outer wall of the mold, a uniform method is used to fix it to the outer wall of the mold, including but not limited to elastic bonding, clamping, and adsorption, so as to avoid the impact of different fixing parameters on the stability of subsequent ultrasonic echo signal acquisition.

[0031] The multiplexer uses a time-division switching acquisition method to avoid signal crosstalk caused by the synchronous transmission of multiple ultrasonic signals. At the same time, it only needs to be configured with one set of back-end signal processing circuits, which reduces the hardware cost of multi-point monitoring.

[0032] After the mold cavity is sealed, the vacuum negative pressure acquisition module collects the overall vacuum negative pressure value inside the cavity in real time through the negative pressure sensor. After the vacuum negative pressure value stabilizes, the signal reference correction module performs dry-state reference acquisition, controls the multiplexer to sequentially collect multiple sets of ultrasonic echo signals under the dry-state reference state at each monitoring point, so as to obtain the average value of the ultrasonic echo signal under the dry-state reference state at each monitoring point, avoiding acquisition errors caused by random circuit noise, environmental airflow disturbances, and instantaneous ultrasonic emission fluctuations. The dry-state reference state is the working condition in which the mold is lined with release cloth, fiberglass cloth, carbon fiber cloth, balsa wood core material, foam core material, isolation membrane, flow guide net, and vacuum bag film and is sealed and vacuumed, with no resin-based composite materials inside the cavity, and the vacuum negative pressure value is constant for a long time.

[0033] In practice, by collecting ultrasonic echoes from the outer wall of the mold, destructive modifications such as drilling can be avoided, thus preventing damage to the mold structure or the risk of air leakage. When collecting ultrasonic static reference signals, the ultrasonic static reference signals corresponding to each monitoring point are collected multiple times under stable vacuum negative pressure conditions, which can more accurately obtain the ultrasonic static reference signals to accurately identify the subsequent resin impregnation state. This avoids acquisition errors caused by random circuit noise, environmental airflow disturbances, and instantaneous ultrasonic emission fluctuations. By combining the bending angle of the mold to be poured with the flow rate and suction pressure, the impregnation state of the mold cavity with the bending angle can be accurately monitored, so that the resin-based composite material can completely impregnate the mold cavity.

[0034] Specifically, the resin infusion multi-point monitoring system also includes: The negative pressure control module determines the suction pressure based on the comparison between the vacuum negative pressure value and the preset target negative pressure, so as to stabilize the negative pressure fluctuation within the preset negative pressure fluctuation threshold range. The immersion start control module is used to control the opening of the glue injection pipeline after the ultrasonic static reference signal of each monitoring point has been calibrated and the vacuum negative pressure in the mold cavity has been stabilized and reached the standard. An ultrasonic polling acquisition control module determines the polling acquisition cycle based on the flow velocity; A flow rate control module controls the opening degree of the injection valve for the resin-based composite material based on the flow rate and the bending angle of the mold.

[0035] In this embodiment of the invention, a preset negative pressure fluctuation threshold range is used to limit the allowable fluctuation range of the vacuum negative pressure value of the mold cavity, and serves as a criterion for the negative pressure control module to adjust the suction pressure. The ultrasonic polling acquisition control module determines the polling acquisition cycle based on the flow rate. The polling acquisition cycle is negatively correlated with the flow rate. When the flow rate of the resin-based composite material is fast, the resin-based composite material is pushed into the mold cavity at a fast speed, and the wetting state of each monitoring point changes rapidly. At this time, if the polling acquisition cycle is too long, it will be impossible to accurately capture the wetting transition process, and it is easy to miss the semi-permeable state. Therefore, the polling acquisition cycle should be shortened to increase the sampling frequency of the signal at each monitoring point, so as to facilitate real-time tracking of the leading dynamics of the resin-based composite material. The slower the flow rate of resin-based composite materials, the longer the polling acquisition cycle needs to be to reduce the frequent switching of multiplexers and high-frequency data processing, thereby reducing the operating load and energy consumption of the resin infusion multi-point monitoring system.

[0036] In this embodiment, the negative pressure control module determines the suction pressure based on the comparison between the vacuum negative pressure value and the preset target negative pressure. This ensures that the negative pressure fluctuation remains stable within the preset negative pressure fluctuation threshold range, avoiding frequent speed adjustments and start-stop cycles of the vacuum pump. Simultaneously, it maintains a constant pressure difference within the cavity, ensuring consistent compaction within the fiber preform. The ultrasonic polling acquisition control module adaptively matches the polling acquisition cycle of the multiplexer based on the real-time flow rate of the resin-based composite material. The polling acquisition cycle is negatively correlated with the flow rate; when the resin-based composite material flows at a higher speed, the flow front advances faster within the mold cavity, and the wetting state at each monitoring point changes rapidly. If a fixed and long polling acquisition cycle is still used, the ultrasonic signal sampling will lag, making it impossible to accurately capture the brief semi-permeation transition process of the monitoring point, which will lead to the problem of missed or false judgment of the immersion state. Therefore, the polling acquisition cycle is shortened to increase the sampling frequency of ultrasonic signals at each monitoring point and to track the dynamic changes of the flow front of the resin-based composite material in real time and accurately. Conversely, when the flow rate of the resin-based composite material is slow, the resin immersion state inside the cavity changes gradually, and there is no need for high-frequency sampling monitoring. The corresponding polling acquisition cycle is extended to reduce the frequent switching of the multiplexer and high-frequency data operation, which effectively reduces the hardware load and power consumption of the entire monitoring system.

[0037] Please see Figure 2 As shown, it is a block diagram of the signal reference correction module described in this embodiment; Specifically, the signal reference correction module includes: The dry-state reference acquisition submodule is used to acquire and calibrate the ultrasonic static reference signal at each monitoring point in the dry-state reference state after the vacuum negative pressure value has stabilized. The noise parameter calculation submodule is used to calculate the noise standard deviation corresponding to each monitoring point based on the calibrated ultrasonic static reference signal of each monitoring point.

[0038] In this embodiment of the invention, the dry-state reference acquisition submodule controls the multiplexer to continuously acquire multiple sets of ultrasonic static reference signals under dry-state reference conditions at the same monitoring point, and removes outlier signals caused by sudden abnormal disturbances during the acquisition process. It is understood that outlier signals are generated by sudden and accidental factors such as instantaneous electromagnetic interference, slight vibration of the mold, and short-term airflow impact, and cannot reflect the true ultrasonic echo amplitude under dry-state reference conditions. Therefore, they need to be removed in advance, and the average echo amplitude of the remaining valid ultrasonic static reference signals is calculated, which is the ultrasonic static reference signal.

[0039] The noise parameter calculation submodule determines the noise standard deviation corresponding to each monitoring point. In this embodiment of the invention, the noise standard deviation is used to characterize the degree of noise signal fluctuation. The larger the noise standard deviation value, the greater the noise fluctuation. It is understood that the calculation of the noise standard deviation is existing technology and will not be described in detail here. Based on the corresponding noise standard deviation, a corresponding noise threshold is generated to accurately distinguish between equipment circuit noise, invalid signal fluctuations caused by environmental disturbances, and changes in the amplitude of real ultrasonic echoes caused by the impregnation of resin-based composite materials.

[0040] In this embodiment, the ultrasonic static reference signal under dry reference conditions is acquired and calibrated by the dry reference acquisition submodule, which can accurately obtain the true ultrasonic echo amplitude under dry reference conditions. This avoids the impact of fluctuations caused by sudden accidental factors such as transient electromagnetic interference, slight mold vibration, and short-term airflow impact on the accuracy of ultrasonic echo amplitude. The noise parameter calculation submodule can characterize the degree of noise signal fluctuation by calculating the noise standard deviation, so as to accurately distinguish the equipment circuit noise, invalid signal fluctuations caused by environmental disturbances, and changes in the true ultrasonic echo amplitude caused by the impregnation of resin-based composite materials.

[0041] Specifically, the impregnation identification module determines the resin impregnation state based on the difference between the real-time echo amplitude and the corresponding ultrasonic static reference signal, combined with a noise threshold. Based on the difference being less than or equal to the noise threshold, the resin impregnation state is determined to be an unimpregnated state. Based on the difference being greater than the noise threshold and less than the preset first amplitude threshold, the resin impregnation state is determined to be a semi-impregnation transition state. Based on the difference being greater than or equal to a preset first amplitude threshold, the resin impregnation state is determined to be a fully impregnated state. The noise threshold is three times the noise standard deviation, and the first amplitude threshold is used to characterize the critical value of the ultrasonic echo difference corresponding to the air in the mold cavity fiber preform being filled with resin-based composite material.

[0042] In this embodiment of the invention, the noise threshold is determined based on three times the noise standard deviation. Those skilled in the art will understand that, according to the statistical principle of normal distribution, equipment circuit noise, mold vibration, and airflow disturbance dry-state random noise all follow a normal Gaussian distribution. Under the normal distribution law, the probability of noise signal fluctuation falling within three times the noise standard deviation is extremely high, almost encompassing all inherent random noise under normal working conditions. There is only a very small probability of signal fluctuation exceeding three times the noise standard deviation. Therefore, when the difference between the real-time echo amplitude and the corresponding ultrasonic static reference signal is less than or equal to the noise threshold, it indicates that the signal fluctuation is within the normal noise fluctuation range and is judged as pure noise interference without resin impregnation. When the difference between the real-time echo amplitude and the corresponding ultrasonic static reference signal is greater than the noise threshold, it indicates that the signal fluctuation exceeds the normal noise limit and is no longer considered noise interference. It is determined to be a change in the real ultrasonic signal caused by resin impregnation.

[0043] When the difference in echo amplitude exceeds the noise threshold but does not reach the preset first amplitude threshold, it indicates that the resin has begun to penetrate into the gap of the fiber preform, but has not completely filled it. A large amount of air remains inside the cavity, and the fiber impregnation is in an uneven semi-permeable transition state.

[0044] When the difference in echo amplitude is greater than or equal to the preset first amplitude threshold, it means that the air in the gap of the fiber preform has been basically filled by the resin-based composite material, the fiber is fully impregnated, and it is judged to be in a fully impregnated state.

[0045] In this embodiment of the invention, the echo amplitude difference is the difference between the real-time echo amplitude and the corresponding ultrasonic static reference signal.

[0046] In practice, the noise threshold is determined by three times the noise standard deviation, which can more accurately determine the resin impregnation state. Based on the difference being less than or equal to the noise threshold, the resin impregnation state is determined to be unimpregnated. This can avoid the random noise caused by equipment circuit noise, mold vibration and airflow disturbance reducing the accuracy of resin impregnation state determination. Based on the difference being greater than the noise threshold and less than the preset first amplitude threshold, the resin impregnation state is determined to be a semi-impregnation transition state. This can make an accurate judgment on the impregnation effect of resin-based composite materials and improve the accuracy and sensitivity of resin-based composite material impregnation identification.

[0047] Please see Figure 3 As shown, this is a block diagram of the global flow analysis module described in this embodiment. In this embodiment of the invention, the global flow analysis module includes an immersion start time extraction submodule, which records the immersion start time of the resin-based composite material at the corresponding monitoring point as the time when the difference in echo amplitude at any monitoring point is greater than the noise threshold. The difference in echo amplitude is determined based on the real-time echo amplitude and the ultrasonic static reference signal at each monitoring point to determine the initial time when the resin-based composite material arrives at each monitoring point.

[0048] The immersion start time extraction submodule can determine the initial immersion time of resin based on the relationship between the echo amplitude difference and the noise threshold. Since signal fluctuations that do not exceed the noise threshold are invalid noise disturbances caused by equipment circuits, ambient airflow, and mold vibration, they cannot represent the resin immersion behavior. Therefore, the immersion start time extraction submodule only locks and records the moment when the echo amplitude difference first exceeds the noise threshold, ensuring that the immersion start time recorded at each monitoring point is accurate and effective.

[0049] Specifically, the global flow analysis module also includes: The flow time difference calculation submodule determines the flow duration of the resin-based composite material between adjacent monitoring points based on the wetting start time of adjacent monitoring points. The resin flow rate calculation submodule determines the flow rate of the resin-based composite material based on the monitoring distance between each monitoring point and the flow duration.

[0050] In this embodiment of the invention, the flow time difference calculation submodule can determine the flow duration between two monitoring points by the infiltration start time of adjacent or any two monitoring points.

[0051] The resin flow rate calculation submodule can determine the flow rate of resin-based composite materials based on the monitoring distance between each monitoring point and the flow duration. The monitoring distance between each monitoring point can be obtained through conventional measurement methods.

[0052] Specifically, the negative pressure control module increases the pumping pressure based on the difference between the preset target negative pressure and the vacuum negative pressure value when the vacuum negative pressure value is less than the preset target negative pressure value, so as to make the vacuum negative pressure value reach the immersion start requirement; when the vacuum negative pressure value is greater than or equal to the preset target negative pressure, it maintains the current pumping pressure to keep the negative pressure fluctuation stable. The preset target negative pressure is determined based on the bending angle, and the preset target negative pressure is positively correlated with the bending angle.

[0053] In this embodiment of the invention, the preset target negative pressure is positively correlated with the bending angle of the mold. For large-angle gentle bending areas, a higher preset target negative pressure is adjusted to ensure that the fiber preform is fully compacted and improve the flow uniformity of the resin-based composite material. For small-angle sharp bending areas, a lower preset target negative pressure is adjusted to avoid excessive vacuum negative pressure value causing preform extrusion deformation and layup collapse, and to prevent resin-based composite material accumulation and glue shortage at the bending position. The difference between the preset target negative pressure and the vacuum negative pressure value characterizes the degree of deviation of the current negative pressure condition of the mold cavity; When the vacuum negative pressure value is less than the preset target negative pressure, the larger the difference between the preset target negative pressure and the vacuum negative pressure value, the worse the vacuuming effect in the mold cavity is, and the fiber preform is not sufficiently compacted. It is necessary to increase the suction pressure accordingly to quickly make up the negative pressure difference and make the cavity negative pressure reach the resin impregnation start-up standard.

[0054] A vacuum negative pressure value greater than or equal to the preset target negative pressure indicates that the current cavity negative pressure is sufficient to meet the process setting requirements, the mold fiber preform is in a stable compaction state, and maintaining the current suction pressure is sufficient to ensure the stability of the negative pressure.

[0055] In implementation, the negative pressure control module increases the suction pressure based on the difference between the vacuum negative pressure value and the preset target negative pressure value, which ensures that the fiber preform is fully compacted, improves the flow uniformity of the resin-based composite material, and avoids the preform extrusion deformation and ply collapse caused by excessive vacuum negative pressure value. The preset target negative pressure is positively correlated with the bending angle, which can also prevent the preform extrusion deformation and ply collapse caused by excessive vacuum negative pressure value, and prevent the accumulation of resin-based composite material and glue shortage at the bending position.

[0056] Specifically, the ultrasonic polling acquisition control module determines the polling acquisition cycle based on the flow velocity, wherein the polling acquisition cycle is negatively correlated with the flow velocity.

[0057] Please see Figure 4 As shown, it is a flowchart of the process of the flow rate control module controlling the flow rate in this embodiment; Specifically, the flow rate control module increases the injection valve opening based on the difference between the minimum preset standard flow rate range and the flow rate when the flow rate is less than the minimum preset standard flow rate range, thereby accelerating the filling rate of the resin-based composite material; maintains the current injection valve opening based on the flow rate within the preset standard flow rate range, thereby maintaining the current filling rate; and decreases the injection valve opening based on the difference between the flow rate and the maximum preset standard flow rate range when the flow rate is greater than the maximum preset standard flow rate range, thereby reducing the filling rate of the resin-based composite material. The preset standard flow rate range is determined based on the viscosity of the resin-based composite material.

[0058] In this embodiment of the invention, the difference between the minimum value of the preset standard flow rate range and the flow rate characterizes the low-speed deviation of the current resin-based composite material filling rate, representing the degree of lag of the actual resin flow rate compared to the minimum flow rate of the process qualification and the degree of lack of filling power. The difference between the flow rate and the maximum value of the preset standard flow rate range characterizes the degree of overspeed deviation of the current resin-based composite material filling rate, representing the excessive value of the actual flow rate of the resin-based composite material exceeding the upper limit of the safe process. The preset standard flow rate range is determined based on the viscosity of the resin-based composite material. The higher the viscosity of the resin-based composite material, the greater the flow resistance. The corresponding preset standard flow rate range should be generally smaller to avoid uneven wetting and air entrapment defects caused by excessively fast flow rate. The lower the viscosity of the resin-based composite material, the better the resin flowability. The corresponding preset standard flow rate range needs to be adjusted upward to improve the pouring efficiency while ensuring molding quality.

[0059] In implementation, based on the flow rate being less than the minimum value of the preset standard flow rate range, the opening of the injection valve is increased according to the difference between the minimum value of the preset standard flow rate range and the flow rate to accelerate the filling rate of the resin-based composite material. This can quickly increase the flow rate and filling rate of the resin-based composite material, making the flow rate match the vacuum negative pressure value, and avoiding a slow resin filling rate that would lead to delayed curing of the resin-based composite material and excessive filling time, thus reducing filling efficiency. Based on the flow rate being greater than the maximum value of the preset standard flow rate range, the opening of the injection valve is decreased according to the difference between the flow rate and the maximum value of the preset standard flow rate range to reduce the filling rate of the resin-based composite material. This can ensure the flow state of the resin-based composite material and avoid eddies at the bends and corners of the mold caused by excessively fast flow of the resin-based composite material, which could lead to bubbles and reduce film quality.

[0060] Specifically, the flow rate control module determines the opening degree of the injection valve based on the flow rate, and then further determines the opening degree of the injection valve based on the bending angle of the mold. The opening degree of the glue injection valve is positively correlated with the bending angle of the mold.

[0061] In this embodiment of the invention, the opening degree of the injection valve is positively correlated with the bending angle of the mold. The larger the bending angle of the mold, the larger the opening degree of the injection valve after secondary correction. The smaller the bending angle of the mold, the sharper the structure at the corner of the mold, and the smaller the opening degree of the injection valve after secondary correction.

[0062] For large-angle, gently curving areas, the flow channels of resin-based composite materials are wide, making it less likely to generate airflow eddies and air stagnation. The valve opening should be increased to improve the filling flow rate of the resin-based composite material and speed up the filling process, thereby improving the overall injection efficiency while ensuring molding quality. For sharp bends with small angles, the flow channels inside the mold cavity are narrow. If the flow rate of the resin-based composite material is too fast, it is easy to trap air and form air bubble defects, resulting in uneven accumulation and wetting of the local resin-based composite material. Therefore, the valve opening should be reduced accordingly to slow down the advance speed of the resin-based composite material in the corner area, so as to ensure that the resin-based composite material is evenly spread, fully expel the air inside the cavity, and avoid air bubbles and accumulation of resin-based composite material at the corner position.

[0063] In implementation, the flow rate control module determines the opening of the injection valve based on the flow rate, and then further determines the opening of the injection valve based on the bending angle of the mold. This allows for a secondary adjustment of the injection valve opening based on the mold angle, resulting in more precise control of the flow rate of the resin-based composite module. This avoids the defects caused by excessively fast flow rates that can trap air and form bubbles, leading to uneven wetting of localized resin-based composite materials.

[0064] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

[0065] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A multi-point monitoring system for resin infusion based on ultrasonic echo attenuation and reference correction, characterized in that, include: An ultrasonic transmitter and receiver module is installed at various monitoring points on the outer wall of the mold to be injected. It is used to transmit ultrasonic waves to the mold and collect the ultrasonic echoes at the corresponding points. A multiplexer is connected to the ultrasonic transmitter and receiver module to achieve multi-point ultrasonic polling acquisition; Vacuum negative pressure acquisition module, which is used to acquire the overall vacuum negative pressure value of the mold cavity; The signal reference correction module is used to calibrate the ultrasonic static reference signal of each monitoring point in the dry reference state after the vacuum negative pressure value has stabilized, and to calculate the noise standard deviation corresponding to each monitoring point. The impregnation identification module determines the resin impregnation state of the fiber preform inside the mold cavity based on the difference between the real-time echo amplitude of each monitoring point and the corresponding ultrasonic static reference signal. Angle acquisition module, which is used to detect the bending angle of the mold to be poured; The global flow analysis module determines the initiation time of the resin-based composite material based on the relationship between the difference and the noise threshold, and determines the flow velocity of the resin-based composite material based on the difference in the infiltration time sequence of each monitoring point and the distance between each monitoring point, wherein the noise threshold is determined according to the noise standard deviation. The polling acquisition cycle is the total time for the multiplexer to complete one round of sensor ultrasonic signal acquisition.

2. The resin infusion multi-point monitoring system based on ultrasonic echo attenuation and reference correction according to claim 1, characterized in that, Also includes: The negative pressure control module determines the suction pressure based on the comparison between the vacuum negative pressure value and the preset target negative pressure, so as to stabilize the negative pressure fluctuation within the preset negative pressure fluctuation threshold range. The immersion start control module is used to control the opening of the glue injection pipeline after the ultrasonic static reference signal of each monitoring point has been calibrated and the vacuum negative pressure in the mold cavity has been stabilized and reached the standard. An ultrasonic polling acquisition control module determines the polling acquisition cycle based on the flow velocity; A flow rate control module controls the opening degree of the injection valve for the resin-based composite material based on the flow rate and the bending angle of the mold.

3. The resin infusion multi-point monitoring system based on ultrasonic echo attenuation and reference correction according to claim 2, characterized in that, The signal reference correction module includes: The dry-state reference acquisition submodule is used to acquire and calibrate the ultrasonic static reference signal at each monitoring point in the dry-state reference state after the vacuum negative pressure value has stabilized. The noise parameter calculation submodule is used to calculate the noise standard deviation corresponding to each monitoring point based on the calibrated ultrasonic static reference signal of each monitoring point.

4. The resin infusion multi-point monitoring system based on ultrasonic echo attenuation and reference correction according to claim 3, characterized in that, The impregnation identification module determines the resin impregnation state based on the difference between the real-time echo amplitude and the corresponding ultrasonic static reference signal, combined with a noise threshold. Based on the difference being less than or equal to the noise threshold, the resin impregnation state is determined to be an unimpregnated state. Based on the difference being greater than the noise threshold and less than the preset first amplitude threshold, the resin impregnation state is determined to be a semi-impregnation transition state. Based on the difference being greater than or equal to a preset first amplitude threshold, the resin impregnation state is determined to be a fully impregnated state. The noise threshold is three times the noise standard deviation, and the first amplitude threshold is used to characterize the critical value of the ultrasonic echo difference corresponding to the air in the mold cavity fiber preform being filled with resin-based composite material.

5. The resin infusion multi-point monitoring system based on ultrasonic echo attenuation and reference correction according to claim 4, characterized in that, The global flow analysis module includes an immersion initiation time extraction submodule, which records the initiation time of the resin-based composite material at any monitoring point as the immersion initiation time of the resin-based composite material at the corresponding monitoring point based on the difference in echo amplitude at any monitoring point being greater than the noise threshold. The difference in echo amplitude is determined based on the real-time echo amplitude and the ultrasonic static reference signal at each monitoring point to determine the initial time when the resin-based composite material arrives at each monitoring point.

6. The resin infusion multi-point monitoring system based on ultrasonic echo attenuation and reference correction according to claim 5, characterized in that, The global flow analysis module also includes: The flow time difference calculation submodule determines the flow duration of the resin-based composite material between adjacent monitoring points based on the wetting start time of adjacent monitoring points. The resin flow rate calculation submodule determines the flow rate of the resin-based composite material based on the monitoring distance between each monitoring point and the flow duration.

7. The resin infusion multi-point monitoring system based on ultrasonic echo attenuation and reference correction according to claim 6, characterized in that, The negative pressure control module increases the pumping pressure based on the difference between the preset target negative pressure and the vacuum negative pressure value when the vacuum negative pressure value is less than the preset target negative pressure value, so as to make the vacuum negative pressure value reach the immersion start requirement; when the vacuum negative pressure value is greater than or equal to the preset target negative pressure value, it maintains the current pumping pressure to keep the negative pressure fluctuation stable. The preset target negative pressure is determined based on the bending angle, and the preset target negative pressure is positively correlated with the bending angle.

8. The resin infusion multi-point monitoring system based on ultrasonic echo attenuation and reference correction according to claim 7, characterized in that, The ultrasonic polling acquisition control module determines the polling acquisition cycle based on the flow velocity, wherein the polling acquisition cycle is negatively correlated with the flow velocity.

9. The resin infusion multi-point monitoring system based on ultrasonic echo attenuation and reference correction according to claim 8, characterized in that, The flow rate control module increases the injection valve opening based on the difference between the minimum preset standard flow rate range and the flow rate when the flow rate is less than the minimum preset standard flow rate range, thereby accelerating the filling rate of the resin-based composite material; it maintains the current injection valve opening based on the flow rate within the preset standard flow rate range, thereby maintaining the current filling rate; and it decreases the injection valve opening based on the difference between the flow rate and the maximum preset standard flow rate range when the flow rate is greater than the maximum preset standard flow rate range, thereby reducing the filling rate of the resin-based composite material. The preset standard flow rate range is determined based on the viscosity of the resin-based composite material.

10. The resin infusion multi-point monitoring system based on ultrasonic echo attenuation and reference correction according to claim 9, characterized in that, After determining the opening degree of the injection valve based on the flow rate, the flow rate control module further determines the opening degree of the injection valve by combining the bending angle of the mold. The opening degree of the glue injection valve is positively correlated with the bending angle of the mold.

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