Device and method for detecting ice layer melting amount and melting rate of airplane based on infrared digital holography

Abstract

The application relates to the technical field of infrared digital holographic detection, and discloses an aircraft ice layer melting amount and melting rate detection device and method based on infrared digital holography. The method combines the excellent characteristics of infrared digital holographic high-precision three-dimensional topography measurement, non-contact and strong anti-environmental interference capability, and realizes real-time detection of the solid-liquid phase change interface of the aircraft surface ice layer on the premise of not damaging the ice layer and the aerodynamic shape by relying on the double-exposure holographic interferometric measurement principle. In the process of aircraft flight or deicing operation, the dynamic melting amount and melting rate of the ice layer are acquired in real time, and the high-fidelity data is transmitted to the electric heating deicing system as a feedback signal to accurately control the heating power and time, so that blind over-heating is effectively avoided, the structural thermal stress is reduced, and the generation of fatal backflow ice is fundamentally prevented.

Description

Technical Field

[0001] This invention relates to the field of infrared digital holographic detection technology, specifically to a device and method for detecting the amount and rate of aircraft ice melting based on infrared digital holography. Background Technology

[0002] Aircraft icing, a significant threat to aviation safety, not only alters the aerodynamic shape of components such as wings but also leads to a substantial decrease in lift (up to 11.1%) and a sharp increase in drag (up to 48.2%). Icing occurs rapidly when an aircraft passes through clouds containing supercooled water droplets. If de-icing systems (such as electrothermal de-icing systems) malfunction, melted ice can flow backward and refreeze in unprotected areas behind the wings, forming highly destructive "backflow icing." To date, numerous serious aviation accidents, both domestically and internationally, have resulted in loss of aircraft control due to improper de-icing or backflow icing, causing enormous economic losses to airlines and severely threatening the lives of passengers and crew.

[0003] The main reasons for the low efficiency and derivative hazards of existing electrothermal de-icing systems are twofold: First, due to the inability to accurately control the melting state of the ice, the system often blindly overheats during flight. This not only wastes a large amount of energy but also generates enormous thermal stress due to the mismatch in thermal expansion coefficients between the metal heating element and the composite material skin, leading to thermal fatigue, decreased interlaminar shear strength, and even interface delamination. Second, improper control of heating time or power results in excessive meltwater at the interface between the ice layer and the substrate, which overflows backward under the action of airflow, forming a fatal "backflow ice" defect. Therefore, real-time monitoring of ice melting amount, transient melting rate, and dynamic monitoring of the solid-liquid phase transition interface are the main aspects of quality and performance testing for modern high-efficiency de-icing systems.

[0004] Existing traditional methods for detecting ice melting amount and melting rate can be mainly divided into three types: 1. Physical weighing method based on AS6170 standard test method, which relies on manually collecting meltwater (saltwater) at fixed time intervals and weighing it to estimate the average rate; 2. Using traditional ice layer thickness sensors or relying on visual / video observation of the surface, which can only determine the physical displacement or presence of ice; 3. Using methods such as two-dimensional infrared thermal imaging to monitor surface temperature distribution. Current traditional detection methods have the disadvantages of low detection efficiency, large human intervention, and low detection accuracy due to lack of depth data. More importantly, they can only provide two-dimensional surface information or discrete average data, and cannot perform non-contact three-dimensional real-time detection of melting amount and melting rate of the phase transition interface inside the ice layer during aircraft flight.

[0005] Therefore, how to efficiently, accurately, and non-contactly detect the amount and rate of ice melting in real time during aircraft flight or de-icing operations, and how to provide early warning and closed-loop control for the risks of overheating or backflowing ice, so as to significantly reduce energy consumption and the occurrence of de-icing accidents, remains an urgent technical problem to be solved. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a device and method for detecting the amount and rate of aircraft ice melting based on infrared digital holography. It has advantages such as effectively avoiding blind overheating, reducing structural thermal stress, and fundamentally preventing the generation of fatal backflow ice, thus solving the aforementioned technical problems.

[0007] To achieve the above objectives, the present invention provides the following technical solution: an infrared digital holographic-based device for detecting the amount and rate of aircraft ice melting, comprising an infrared pulse laser and a beam splitter I. The infrared pulse laser emits a laser beam that is directed towards the beam splitter I and splits into two beams, which enter a first optical path channel and a second optical path channel, respectively. The first optical path channel outputs a reference beam to a beam combiner installed on the surface of the aircraft. The second optical path channel outputs a reference beam to the surface of the aircraft ice layer, which is reflected to obtain an object beam, which is then input into the beam combiner. After beam combining, the object beam enters an infrared image sensor and is then input into a computer for detection.

[0008] As a preferred technical solution of the present invention, the first optical path channel includes a reflector I, an optical path compensator, an optical intensity attenuator, a beam expander I, a spatial filter I, and a Fourier lens I. The first laser beam enters the optical path compensator after passing through the reflector I for optical path adjustment, and is transmitted to the optical intensity attenuator for optical power attenuation. The attenuated beam is filtered by the beam expander I and the spatial filter I, and then passes through the Fourier lens I to form a reference beam.

[0009] As a preferred technical solution of the present invention, the second optical path channel includes a reflector II, a beam expander II, a spatial filter II, and a Fourier lens II. The second laser beam is reflected by the reflector II, filtered by the beam expander II and the spatial filter II, and then passes through the Fourier lens II to form a parallel detection beam. This beam illuminates the surface of the aircraft ice layer and is reflected to obtain an object beam.

[0010] As a preferred embodiment of the present invention, the center wavelength of the laser emitted by the infrared pulsed laser is in the range of 1064nm to 1550nm.

[0011] As a preferred embodiment of the present invention, the computer is communicatively connected to the optical path compensator and the optical intensity attenuator, respectively.

[0012] This invention also provides a method for detecting the amount and rate of aircraft ice melting based on infrared digital holography, and based on the above-mentioned device for detecting the amount and rate of aircraft ice melting based on infrared digital holography, the method includes the following steps: S1: Turn on the infrared pulsed laser. The object beam and the reference beam form an infrared holographic interference pattern on the beam combiner. S2: The first infrared hologram in the initial state is acquired by an infrared image sensor, transmitted to a computer, and the initial complex optical field U1 is obtained by the angular spectrum reconstruction algorithm in the computer. S3: During the process of heating and melting the ice layer, the infrared image sensor continuously or at predetermined time intervals acquires the infrared hologram to be tested, transmits it to the computer, and obtains the deformation complex light field U2 at the time of melting through the angular spectrum reconstruction algorithm in the computer. S4: The computer divides the deformed complex optical field U2 with the initial complex optical field U1 to obtain the phase wrapped by the deformed field. S5: Perform phase unwrapping processing on the computer to obtain the true phase change Δ. ; S6: Based on phase change Δ The transient melting amount Δz at the ice interface was calculated, and the ice melting rate v was calculated by combining the sampling time interval. S7: Transmit the ice melting rate v and transient melting amount Δz to the de-icing control unit; S8: During the heating and melting process, the control unit first compares the real-time feedback melting rate v with the preset safe melting rate range. If the ice melting rate v exceeds the upper threshold of the range, the duty cycle is reduced. If the ice melting rate v is lower than the lower threshold of the preset safe melting rate range, the duty cycle is increased. At the same time, the de-icing endpoint is monitored. Specifically, when the transient melting amount Δz is less than 100 micrometers, it is determined that the mechanical adhesion between the ice layer and the aircraft surface has been destroyed, and heat input is stopped.

[0013] As a preferred technical solution of the present invention, the specific expression for the transient melting amount Δz is as follows: in, Indicates the amount of phase change. λ represents the refractive index of the ice layer and water film medium, and λ is the wavelength of the infrared pulsed laser.

[0014] Compared with existing technologies, this invention provides a device and method for detecting the amount and rate of aircraft ice melting based on infrared digital holography, which has the following advantages: This invention combines the superior characteristics of infrared digital holography, such as high-precision three-dimensional topography measurement, non-contact operation, and strong resistance to environmental interference, to perform real-time detection of the solid-liquid phase transition interface of ice on aircraft surfaces without damaging the ice layer or aerodynamic shape. It relies on the principle of double-exposure holographic interferometry. During aircraft flight or de-icing operations, the dynamic melting amount and rate of the ice layer are acquired in real time, and this high-fidelity data is transmitted as a feedback signal to the electrothermal de-icing system. This allows for precise control of heating power and time, effectively avoiding blind overheating, reducing structural thermal stress, and fundamentally preventing the formation of fatal backflow ice. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall framework of the present invention; Figure 2 This is a schematic diagram of the overall invention; Figure 3 This is a schematic diagram of the process of the present invention.

[0016] Among them, 1. Infrared pulsed laser; 2. Beam splitter I; 3. Reflector I; 4. Optical path compensator; 5. Optical intensity attenuator; 6. Beam expander I; 7. Spatial filter I; 8. Fourier lens I; 9. Beam combiner; 10. Reflector II; 11. Beam expander II; 12. Spatial filter II; 13. Fourier lens II; 14. Aircraft surface; 15. Infrared image sensor; 16. Computer; 17. Outer shell. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Please see Figure 1 - Figure 3 The aircraft ice melting amount and melting rate detection device based on infrared digital holography includes: an infrared pulse laser 1, a beam splitter I2, a reflector I3, an optical path compensator 4, an optical intensity attenuator 5, a beam expander I6, a spatial filter I7, a Fourier lens I8, a beam combiner 9, a reflector II10, a beam expander II11, a spatial filter II12, a Fourier lens II13, an aircraft ice surface 14, an infrared image sensor 15, a computer 16, and a de-icing control unit. The computer 16 is housed inside a housing 17, specifically an opaque and vibration-resistant housing. All of the above components are mounted on the aircraft surface. The laser beam emitted by infrared pulse laser 1 is split into two beams upon reaching beam splitter I2; The first laser beam passes through mirror I3 and enters optical path compensator 4 for optical path adjustment. It is then transmitted to optical intensity attenuator 5 for optical power attenuation. The attenuated beam is filtered by beam expander I6 and spatial filter I7, and then passes through Fourier lens I8 to form a parallel laser beam, which serves as a reference beam. The optical path compensator 4 contains multiple optical path levels of fiber optic channels to compensate for the optical path value of the reference beam; the optical intensity attenuator 5 can attenuate the optical power of the reference beam so that the optical intensity value of the reference beam is as consistent as possible with the optical intensity value of the object beam. The second laser beam is reflected by mirror II10, filtered by beam expander II11 and spatial filter II12, and then passes through Fourier lens II13 to form a parallel detection beam, which illuminates the surface 14 of the aircraft ice layer. The infrared laser penetrates the ice layer, is reflected by the solid-liquid phase transition interface of the ice-substrate, and returns, carrying dynamic three-dimensional phase information of the ice melting process. This beam serves as the object beam. The object beam and the reference beam are combined at the beam combiner 9, causing interference and forming an infrared interference hologram. The infrared image sensor 15 is synchronously triggered with the infrared pulse laser 1 to acquire the interference hologram in real time and transmit it to the computer 16 for data processing. Infrared pulsed laser 1, whose center wavelength of emitted laser is in the range of 1064nm to 1550nm. This band can not only penetrate ice and melt water film with high transmittance, but its longer wavelength also greatly improves the tolerance of the interferometric system to mechanical vibration of aircraft body or wind tunnel model, which is about 20 times that of the visible light band. Fourier lens I8, Fourier lens II13, beam splitter I2 and beam combiner 9 are made of germanium, silicon or zinc selenide, and their surfaces are coated with a thin film to prevent visible light interference, allowing only infrared beams that match the wavelength emitted by infrared pulse laser 1 to pass through. Computer 16 is connected to optical path compensator 4 and optical intensity attenuator 5 respectively. It automatically adjusts the optical path and intensity of the reference beam through computer program to match the optical path and intensity of the object beam in order to obtain an interference hologram with the best contrast. In traditional de-icing systems such as electrothermal de-icing systems, due to the lack of real-time status sensing of the ice interface, the system typically performs open-loop timed heating. This can easily lead to overheating of the aircraft surface 14, causing a large amount of meltwater to overflow into the unprotected area behind the wing and refreeze, forming a fatal "backflow ice." This embodiment also includes: A method for detecting the amount and rate of aircraft ice melting based on infrared digital holography includes the following steps: S1: Turn on the infrared pulsed laser 1. The object beam and the reference beam form an infrared holographic interference pattern on the beam combiner 9. Adjust the optical path and intensity to match them. The computer 16 automatically adjusts the optical path compensator 4 and the intensity attenuator 5 to make the optical path and intensity values ​​of the reference beam and the object beam as consistent as possible to obtain holographic interference fringes with the best contrast. Specifically: Adjust the optical path compensation knob to make the optical path values ​​of the reference beam and the object beam as consistent as possible; adjust the light intensity attenuation knob to make the light intensity values ​​of the reference beam and the object beam as consistent as possible. S2: The first infrared hologram in the initial state is acquired by the infrared image sensor 15 and transmitted to the computer for digital reconstruction to obtain the initial complex optical field and the initial envelope phase. Infrared image sensor 15 acquires the first infrared hologram as the initial infrared hologram, which is then transmitted to computer 16 for storage. Computer 16 uses numerical reconstruction programs such as angular spectrum reconstruction algorithms to digitally reconstruct the initial infrared hologram and extract the complex optical field of the ice-substrate interface at the initial moment, i.e., the initial complex optical field U1, which includes the initial amplitude and the initial phase. 1; S3: During the process of heating and melting the ice layer, the infrared image sensor 15 continuously or at predetermined time intervals acquires the infrared hologram to be measured, transmits it to the computer 16 for digital reproduction, and obtains the deformation complex light field and the phase of the package to be measured at the time to be measured. During the ablation process of continuous heating in the electrothermal de-icing system, the infrared image sensor 15 acquires the infrared hologram to be measured at the time t to be measured. The computer 16 digitally reconstructs the hologram to obtain the deformed complex optical field U2 (including the deformed phase) at the time of ablation. 2); S4: Computer 16 divides the deformed complex optical field with the initial complex optical field and takes the phase angle of the calculated complex optical field to obtain a phase difference change diagram caused by the melting of ice. Computer 16 divides the deformed complex optical field U2 with the initial complex optical field U1 (or uses conjugate multiplication), and takes the phase angle of the complex optical field after the operation to obtain the phase r of the deformed field caused by solid-liquid phase transition and ice layer thickness attenuation. S5: Perform phase unwrapping processing (on computer 16) to obtain the true phase change Δ ; S6: Based on the phase change Δ The transient melting amount Δz at the ice interface was calculated, and combined with the sampling time interval, the dynamic ice melting rate was calculated. The phase change was converted into the transient melting thickness change (melting amount Δz) at the ice interface on the aircraft surface 14. Combined with the sampling time interval Δt between adjacent holograms, the transient ice melting rate v = Δz / Δt was calculated. The formula for calculating the transient melting amount Δz is: , where λ is the wavelength of infrared pulse laser 1, and n is the refractive index of the ice layer and water film medium; S7: The transient melting amount and melting rate calculated by computer 16 are used as feedback signals and transmitted to the electrothermal de-icing control unit of the aircraft or equipment. S8: The de-icing control unit dynamically adjusts the output power of the heating element or the duty cycle of the pulse width modulation (PWM) based on the feedback signal to match the latent heat required for the solid-liquid phase change interface. Specifically, during the heating and melting process, the control unit first compares the real-time feedback melting rate v with the preset safe melting rate range. If the ice melting rate v exceeds the upper threshold of the range, it indicates that the input heat is excessive, which may cause a large amount of melt water to overflow to the rear of the wing and refreeze to form "reflow ice". The system automatically reduces the duty cycle of the PWM in steps of 5% to 15% to save energy. If the melting rate v is lower than the lower threshold of the range, the system automatically increases the duty cycle in steps of 5% to 15% to ensure de-icing efficiency until the melting rate v returns to the safe melting rate range. At the same time, the system monitors the de-icing endpoint. When the transient melting amount Δz is less than 100 micrometers, it is determined that the mechanical adhesion between the ice layer and the aircraft surface 14 has been destroyed. The system stops the high-power heat input to the corresponding heating area by cutting off the power supply to the corresponding heating area or significantly reducing the duty cycle of the PWM.

[0019] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An aircraft ice accretion and accretion rate detection device based on infrared digital holography, characterized in that: The system includes an infrared pulsed laser (1) and a beam splitter I (2). The infrared pulsed laser (1) emits a laser beam that is directed toward the beam splitter I (2) and splits into two beams, which enter the first optical path channel and the second optical path channel respectively. The first optical path channel outputs a reference beam to a beam combiner (9) mounted on the surface of the aircraft. The second optical path channel outputs a reference beam to the surface of the aircraft ice layer (14), which is reflected to obtain an object beam and input to the beam combiner (9). After beam combining, the object beam enters the infrared image sensor (15) and is then input into the computer (16) for detection.

2. The aircraft ice melting amount and melting rate detection device based on infrared digital holography according to claim 1, characterized in that: The first optical path channel includes a reflector I (3), an optical path compensator (4), an optical intensity attenuator (5), a beam expander I (6), a spatial filter I (7), and a Fourier lens I (8). After the first laser beam passes through the reflector I (3), it enters the optical path compensator (4) for optical path adjustment and is transmitted to the optical intensity attenuator (5) for optical power attenuation. After the attenuated beam is filtered by the beam expander I (6) and the spatial filter I (7), it passes through the Fourier lens I (8) to form a reference beam.

3. The aircraft ice melting amount and melting rate detection device based on infrared digital holography according to claim 2, characterized in that: The second optical path channel includes a reflector II (10), a beam expander II (11), a spatial filter II (12), and a Fourier lens II (13). The second laser beam is reflected by the reflector II (10), filtered by the beam expander II (11) and the spatial filter II (12), and then passes through the Fourier lens II (13) to form a parallel detection beam. This beam illuminates the surface (14) of the aircraft ice layer and is reflected to obtain the object beam.

4. The aircraft ice melting amount and melting rate detection device based on infrared digital holography according to claim 1, characterized in that: The infrared pulsed laser (1) emits lasers with a center wavelength between 1064 nm and 1550 nm.

5. The aircraft ice melting amount and melting rate detection device based on infrared digital holography according to claim 4, characterized in that: The computer (16) is communicatively connected to the optical path compensator (4) and the optical intensity attenuator (5).

6. A method for detecting the amount and rate of aircraft ice melting based on infrared digital holography, and based on the device for detecting the amount and rate of aircraft ice melting based on infrared digital holography as described in any one of claims 1-5, characterized in that: Includes the following steps: S1: Turn on the infrared pulse laser (1), and the object beam and the reference beam form an infrared holographic interference pattern on the beam combiner (9); S2: The first infrared hologram in the initial state is acquired by the infrared image sensor (15) and transmitted to the computer (16). The initial complex light field U1 is obtained by the angular spectrum reconstruction algorithm in the computer (16). S3: During the process of heating and melting the ice layer, the infrared image sensor (15) continuously or according to a predetermined time interval collects the infrared hologram to be tested and transmits it to the computer (16). The deformation complex light field U2 at the melting moment is obtained through the angular spectrum reconstruction algorithm in the computer (16). S4: The computer (16) divides the deformed complex optical field U2 with the initial complex optical field U1 to obtain the phase wrapped by the deformed field; S5: Perform phase unwrapping processing on the computer (16) to obtain the actual phase change Δ ; S6: Based on phase change Δ The transient melting amount Δz at the ice interface was calculated, and the ice melting rate v was calculated by combining the sampling time interval. S7: Transmit the ice melting rate v and transient melting amount Δz to the de-icing control unit; S8: During the heating and melting process, the control unit first compares the real-time feedback melting rate v with the preset safe melting rate range. If the ice melting rate v exceeds the upper threshold of the range, the duty cycle is reduced. If the ice melting rate v is lower than the lower threshold of the preset safe melting rate range, the duty cycle is increased. At the same time, the de-icing endpoint is monitored. Specifically, when the transient melting amount Δz is less than 100 micrometers, it is determined that the mechanical adhesion between the ice layer and the aircraft surface has been destroyed, and heat input is stopped.

7. The method for detecting the amount and rate of aircraft ice melting based on infrared digital holography according to claim 6, characterized in that: The specific expression for the transient melting amount Δz is as follows: in, Indicates the amount of phase change. λ represents the refractive index of the ice layer and water film medium, and λ is the wavelength of the infrared pulsed laser.

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