Helicopter snowblindness visibility measurement method based on image processing

Abstract

The present application proposes a helicopter snow blindness visibility measurement method based on image processing, belonging to the field of helicopter flight test. The purpose is to solve the problem that the existing helicopter visibility measurement in the high-cold snow area is mainly based on the subjective and difficult to quantify continuous monitoring artificial observation method, which cannot meet the automatic and objective measurement requirements under this special working condition. The present application comprises the following steps: S1 selecting test environment and test site that meet the test conditions; S2 determining the flight condition; S3 test flight practice; S4, installing test equipment; S5 judging the snow condition; S6 pre-flight inspection; S7 take-off test; S8 landing test; S9 test end inspection of helicopter state; S10 confirming whether there is remaining experiment; S11 image processing after the end; S12 data analysis. The present application solves the problem that the existing technology is mainly based on subjective and difficult to quantify continuous monitoring artificial observation method, which cannot meet the automatic and objective measurement requirements under this special working condition.

Description

Technical Field

[0001] This invention relates to flight test technology, and more particularly to a method for measuring helicopter snow blindness visibility based on image processing, which belongs to the field of helicopter flight test. Background Technology

[0002] When helicopters operate in high-altitude, snowy regions, they typically need to take off and land on snow-covered ground. During takeoff and landing, the interaction between the rotor downwash and the snow on the ground can easily cause "snow blindness." Snow blindness occurs when the rotor downwash lifts up large amounts of snow particles during takeoff, landing, or hovering, forming high-density snow fog clouds that significantly reduce visibility outside the cockpit. Under these conditions, pilots struggle to identify the ground and obstacles, and cannot obtain effective attitude reference information, easily leading to disorientation and flight safety risks. This phenomenon is particularly pronounced in high-latitude regions, mountainous snowfields, or polar scientific expeditions and search and rescue missions, and is one of the key factors limiting the safety of helicopter flights in snowy areas.

[0003] Currently, visibility measurement from a helicopter cockpit primarily relies on manual observation, where an observer assesses visibility by visually determining the furthest identifiable ground target. This method is highly subjective, significantly affected by individual differences, and difficult to quantify and continuously monitor. With the development of image processing and intelligent sensing technologies, visibility assessment methods based on digital image analysis have become an important direction for visibility measurement in complex visual environments due to their objectivity and repeatability. However, a dedicated image-based visibility measurement method is still lacking for the specific scenario of limited field of vision for helicopter cockpit occupants during takeoff and landing in snowy conditions.

[0004] In summary, there is an urgent need to design an image processing-based method for measuring helicopter visibility in snow blindness, which would solve the problem that existing technologies for helicopter visibility measurement in high-altitude and cold snowy areas mainly rely on manual observation methods that are highly subjective and difficult to quantify and continuously monitor, and cannot meet the needs of automated and objective measurement under such special conditions. Summary of the Invention

[0005] A brief overview of the invention is given below to provide a basic understanding of certain aspects of it. It should be understood that this overview is not an exhaustive summary of the invention. It is not intended to identify key or essential parts of the invention, nor is it intended to limit the scope of the invention. Its purpose is merely to present certain concepts in a simplified form as a prelude to the more detailed description that follows.

[0006] In view of this, in order to solve the problem that the existing helicopter visibility measurement in high-altitude and cold snowy areas mainly relies on manual observation methods that are highly subjective and difficult to quantify and continuously monitor, and cannot meet the needs of automated and objective measurement under this special working condition, this invention provides a helicopter snow blind visibility measurement method based on image processing.

[0007] The technical solution of this invention is a helicopter snow blindness visibility measurement method based on image processing, which specifically includes the following steps:

[0008] S1. Select a test environment and test site that meet the test conditions;

[0009] S2. Develop a flight test plan covering takeoff, landing, and hovering, and determine the operating parameters for the test;

[0010] S3. According to the flight conditions determined in S2, helicopter pilots first conduct simulation training on the simulator, and then conduct test flights on snow-free ground.

[0011] S4. After confirming the helicopter test location at the test site, install the equipment used for the test;

[0012] S5. Determine whether the existing snow cover at the test site meets the test requirements for creating a snow blind scenario that can be blown up by the rotor downwash. If the snow cover meets the test requirements, proceed directly to step S6. If the existing natural snow cover does not meet the test requirements, measures must be taken to make the ground snow cover meet the test requirements.

[0013] S6. Before the flight test, maintenance personnel shall complete the routine inspection and system verification of the helicopter; install a digital camera in the helicopter cockpit; the digital camera shall be positioned in the direction of the pilot's or crew's line of sight to record image data of the blackbody target from the cockpit viewpoint, and the digital camera's field of view shall include an unobstructed sky background.

[0014] S7. Conduct helicopter takeoff tests based on the determined flight conditions;

[0015] S8. Conduct helicopter landing tests according to the determined flight conditions;

[0016] S9. After a single test run is completed and the helicopter has completely stopped outputting power, ground personnel should promptly remove snow from the surface of the aircraft and rotor to ensure equipment safety and the reliability of subsequent tests.

[0017] S10. Confirm if there are any remaining tests for the day; if there are remaining test tasks for the day, proceed to S6; if all tests for the day are completed, proceed to S11.

[0018] S11. Data processing was performed on the images acquired by the digital camera during the experiment to obtain the changes in cockpit visibility during snow blindness in the helicopter takeoff and landing phases. The image processing method is as follows:

[0019] By cropping the region of the blackbody target in the image, the apparent brightness of the blackbody target as observed by the digital camera is obtained. Including the attenuated intrinsic brightness of the blackbody target. and the brightness of the air column ,Right now ;

[0020] Let the distance between the digital camera inside the cockpit and the blackbody target be... According to Beer-Lambert's law, the inherent brightness of a blackbody target... After a distance of R Afterwards, the brightness decreased to ,in The atmospheric extinction coefficient along the optical path between the digital camera and the blackbody target is defined as the average atmospheric extinction coefficient along the optical path between the digital camera and the blackbody target. ,but ;

[0021] Similarly, by cropping the sky region from the image, the apparent brightness of the sky background as observed by the digital camera is obtained. ,in The apparent brightness of the sky background is the inherent brightness of the background. Assuming that external lighting conditions remain stable during the experiment and the sky brightness does not change significantly over time, the apparent brightness of the sky background in the environmental reference image collected before the helicopter rotor airflow disturbs the snow accumulation on the ground is [value missing]. .

[0022] The inherent brightness of a blackbody target Approximately 0, from the above equations we can obtain:

[0023] ;

[0024] ;

[0025] ;

[0026] ;

[0027] The average extinction coefficient between the digital camera and the blackbody target was obtained. Visibility values ​​can be obtained from Koschmieder's law. ,in The human eye contrast threshold is set to 0.02, resulting in a final visibility value. ;

[0028] S12. Based on the image data processing results, evaluate the visibility value during the take-off and landing phase of the helicopter under different test conditions in the snowy environment when there is snow blindness, and evaluate the impact of different test conditions on the severity of snow blindness.

[0029] Furthermore, the flight conditions described in S2 include the helicopter's takeoff weight, the helicopter 1's flight altitude as a function of time, hovering altitude, and altitude holding time.

[0030] Furthermore, if the existing natural snow cover at the test site described in S5 cannot meet the requirements of the snow blindness test, the following measures must be taken:

[0031] If the existing snow cover is too thin, or if the surface layer becomes hardened due to sunlight, wind erosion, or other reasons, making it difficult to be disturbed by airflow, then it is necessary to improve the surface snow layer condition by manually loosening the snow layer, collecting snow from other areas, or supplementing with artificial snowfall, so as to meet the snow blindness generation conditions required for the experiment.

[0032] Furthermore, the helicopter in question is a full-size manned helicopter and must be equipped with standard helicopter flight instruments.

[0033] Furthermore, the standard flight instruments for the helicopter include flight data recording equipment and weather sensors.

[0034] Furthermore, the digital camera parameters remain unchanged during the same test run. During each image acquisition, a precision ranging device such as a laser rangefinder is used to accurately determine the distance between the digital camera in the cockpit and the blackbody target.

[0035] The present invention has the following advantages over the prior art:

[0036] 1. This invention uses a digital camera installed on a helicopter to directly capture images from the cockpit perspective, realistically restoring the pilot's visual environment during takeoff and landing in snowy areas. This effectively avoids measurement deviations caused by differences in observation position and perspective in traditional ground visibility meters, significantly improving the authenticity and representativeness of the measurement results, and making them closer to actual visual perception.

[0037] 2. Based on image processing algorithms, this invention extracts the brightness information of a preset blackbody target and the background sky in an image, and combines it with a visibility calculation model to achieve a quantitative and objective assessment of visibility outside the cockpit. This overcomes the limitations of manual observation methods, which rely on subjective judgment and have poor repeatability, and improves the accuracy and consistency of the measurement.

[0038] 3. The method and system of this invention are simple to construct, requiring only the installation of camera equipment in the cockpit and the setting of standard targets on the ground to achieve fully automated monitoring. This not only provides reliable technical support for the safe flight of helicopters in complex environments such as polar regions and high-altitude cold areas, but also provides executable and reproducible test methods and technical requirements for verifying the snow-covered flight capabilities of helicopters in my country, studying snow blindness effects, and formulating flight operation specifications. It has significant engineering application value and guiding significance.

[0039] 4. This invention has good environmental adaptability. In addition to snow blindness scenarios, it can also be extended to the assessment and verification of visual clarity under other low visibility and complex meteorological conditions such as sandstorms and haze, and has broad applicability and promotion prospects. Attached Figure Description

[0040] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0041] Figure 1 This is a flowchart of an image processing-based method for measuring helicopter snow-blind visibility.

[0042] Figure 2 This is a schematic diagram of the structure of a blackbody target object;

[0043] Figure 3 Aerial view of the equipment layout at the test site;

[0044] Figure 4 A schematic diagram showing the installation of a digital camera inside a helicopter cockpit.

[0045] Figure 5 This is a schematic diagram showing the height change of the blackbody support frame during helicopter takeoff and landing.

[0046] Figure 6 This is a schematic diagram of the cockpit view during data acquisition.

[0047] Figure 7 This is an example of a helicopter snow blindness visibility measurement result; the dashed box area represents the helicopter takeoff and landing phase.

[0048] In the image: 1-Helicopter, 2-Electric lifting support frame, 3-Blackbody target, 4-Mobile meteorological monitoring equipment, 5-Digital camera, 6-Sky background. Detailed Implementation

[0049] To make the technical solutions and advantages of the embodiments of the present invention clearer, the exemplary embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not an exhaustive list of all embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0050] Examples, References Figure 1-7 This embodiment describes a helicopter snow-blind visibility measurement method based on image processing, which specifically includes the following steps:

[0051] S1. Select a test environment and test site that meet the test conditions:

[0052] The test environment was chosen to be a cold outdoor natural environment, and the test site was chosen to be a flat area far away from people; according to the size and flight characteristics of helicopter 1, the test site needs to have sufficient space.

[0053] S2. Develop a flight test plan covering takeoff, landing, and hovering, and determine the operating parameters for the test;

[0054] S3. According to the flight conditions determined in S2, the helicopter pilot first conducts simulated training on the simulator, and then conducts test flights on snow-free ground.

[0055] S4. After confirming the test location of helicopter 1 at the test site, install the equipment used for the test:

[0056] After confirming the test location of helicopter 1, an electric lifting support frame 2 is installed at a location away from the take-off and landing center of helicopter 1 within the test site, and a blackbody target object 3 is installed on the electric lifting support frame 2; a mobile meteorological monitoring device 4 is installed within the test site.

[0057] S5. Determine whether the existing snow cover at the test site meets the test requirements for creating a snow blind scenario that can be blown up by the rotor downwash. If the snow cover meets the test requirements, proceed directly to step S6. If the existing natural snow cover does not meet the test requirements, measures must be taken to make the ground snow cover meet the test requirements.

[0058] S6. Before the flight test, maintenance personnel shall complete the routine inspection and system verification of helicopter 1; install digital camera 5 in the cockpit of helicopter 1; digital camera 5 shall be positioned in the line of sight of the pilot or crew to record image data of blackbody target 3 from the cockpit viewpoint, and the field of view of digital camera 5 shall include an unobstructed sky background 6.

[0059] S7. Conduct a takeoff test of helicopter 1 according to the determined flight conditions:

[0060] Before the rotor is started, the electric lifting support frame 2 is adjusted so that the height of the blackbody target 3 is consistent with the height of the digital camera 5 inside the helicopter 1. The digital camera 5 is turned on and set to manual mode. Parameters such as aperture, shutter speed, focal length, and ISO are adjusted to collect environmental reference images. Then, the helicopter 1 is started and gradually ascends to the predetermined hovering height. At the same time, the height of the blackbody target 3 always increases with the height of the helicopter 1. After the helicopter's height and attitude are stable, the electric lifting support frame 2 is finely adjusted so that the height of the blackbody target 3 is consistent with the digital camera 5. Snow blind image data from the cockpit perspective during the takeoff and hovering phases of the helicopter 1 are collected.

[0061] S8. Conduct a landing test of helicopter 1 according to the determined flight conditions:

[0062] Helicopter 1 begins its descent from a high position on the test site, briefly hovering at an altitude where the rotor downwash has not yet disturbed the snow-covered ground. While hovering and stable, the electric lift support 2 is adjusted to ensure that the height of the blackbody target 3 is consistent with the height of the digital camera 5 inside the helicopter 1, thus acquiring an environmental baseline image of the undisturbed snow-covered ground. Subsequently, helicopter 1 begins its descent, with the height of the electric lift support 2 constantly changing to match the helicopter 1's altitude. When the rotor downwash stirs up the snow on the ground 7, creating snow blindness, helicopter 1 hovers at a predetermined altitude and maintains a stable attitude before fine-tuning the electric lift support 2 to keep the height of the blackbody target 3 consistent with the camera, acquiring snow blindness image data from the cockpit perspective during the landing and hovering phases of helicopter 1.

[0063] S9. After a single test run is completed, once helicopter 1 has completely stopped outputting power, ground personnel should promptly remove snow from the surface of the aircraft and rotor to ensure equipment safety and the reliability of subsequent tests.

[0064] S10. Confirm if there are any remaining tests for the day; if there are remaining test tasks for the day, proceed to S6; if all tests for the day are completed, proceed to S11.

[0065] S11. Data processing is performed on the images acquired by digital camera 5 during the experiment to obtain the changes in cockpit visibility during snow blindness in the takeoff and landing phases of helicopter 1. The image processing method is as follows:

[0066] By cropping the region of the blackbody target 3 in the image, the apparent brightness of the blackbody target 3 observed by the digital camera 5 is obtained. Including the attenuated inherent brightness of the blackbody target 3 and the brightness of the air column ,Right now ;

[0067] Let the distance between the digital camera 5 in the cockpit and the blackbody target 3 be... According to Beer-Lambert's law, the inherent brightness of the blackbody target 3 is... After a distance of R Afterwards, the brightness decreased to ,in The atmospheric extinction coefficient along the optical path between digital camera 5 and blackbody target 3 is defined as the average atmospheric extinction coefficient along the optical path between digital camera 5 and blackbody target 3. ,but ;

[0068] Similarly, by cropping the sky region from the image, the apparent brightness of the sky background 6 observed by digital camera 5 is obtained. ,in Let be the inherent brightness of the sky background 6; assuming that external lighting conditions remain stable during the experiment and the sky brightness does not change significantly over time, then the apparent brightness of the sky background 6 in the environmental reference image collected when the helicopter rotor airflow has not yet disturbed the snow accumulation on the ground is . .

[0069] The inherent brightness of blackbody target 3 Approximately 0, from the above equations we can obtain:

[0070] ;

[0071] ;

[0072] ;

[0073] ;

[0074] The average extinction coefficient between digital camera 5 and blackbody target 3 was obtained. Visibility values ​​can be obtained from Koschmieder's law. ,in The human eye contrast threshold is set to 0.02, resulting in a final visibility value. ;

[0075] S12. Based on the image data processing results, evaluate the visibility value during the take-off and landing phase of helicopter 1 under different test conditions in the snowy environment, and evaluate the impact of different test conditions on the severity of snow blindness.

[0076] Based on the test results, the visibility and safety of helicopter 1 during takeoff and landing in snowy environments were evaluated, and suggestions for optimizing the visibility distance for cockpit occupants were proposed.

[0077] Furthermore, the flight conditions described in S2 include the takeoff weight of helicopter 1, the flight altitude of helicopter 1 as a function of time, hovering altitude, and altitude holding time.

[0078] Furthermore, if the existing natural snow cover at the test site described in S5 cannot meet the requirements of the snow blindness test, the following measures must be taken:

[0079] If the existing snow cover is too thin, or if the surface layer becomes hardened due to sunlight, wind erosion, or other reasons, making it difficult to be disturbed by airflow, then it is necessary to improve the surface snow layer condition by manually loosening the snow layer, collecting snow from other areas, or supplementing with artificial snowfall, so as to meet the snow blindness generation conditions required for the experiment.

[0080] Furthermore, the helicopter 1 is a full-size manned helicopter and must be equipped with standard helicopter flight instruments.

[0081] Furthermore, the standard flight instruments of the helicopter 1 include flight data recording equipment and weather sensors.

[0082] Furthermore, the parameters of the digital camera 5 remain unchanged in the same test vehicle. During each image acquisition, a precision ranging device such as a laser rangefinder is used to accurately determine the distance between the digital camera 5 in the cockpit and the blackbody target 3, providing accurate input parameters for subsequent visibility calculation and image contrast analysis.

[0083] This invention installs a digital camera on a helicopter to directly capture images from the cockpit perspective, realistically reproducing the pilot's visual environment during takeoff and landing in snowy areas. This effectively avoids measurement deviations caused by differences in observation position and perspective in traditional ground visibility meters, significantly improving the authenticity and representativeness of the measurement results and making them closer to actual visual perception. At the same time, based on image processing algorithms, the brightness information of the preset blackbody target and the background sky in the image is extracted and combined with the visibility calculation model to achieve a quantitative and objective assessment of visibility outside the cockpit. This overcomes the limitations of manual observation methods, which rely on subjective judgment and have poor repeatability, and improves the accuracy and consistency of the measurement.

[0084] The method and system of this invention are simple to construct, requiring only the deployment of camera equipment in the cockpit and the setting of standard targets on the ground to achieve fully automated monitoring. It not only provides reliable technical support for the safe flight of helicopters in complex environments such as polar regions and high-altitude cold regions, but also provides executable and reproducible test methods and technical requirements for the verification of helicopter snow-covered flight capabilities, research on snow blindness effects, and the formulation of flight operation specifications in China, possessing significant engineering application value and guiding significance. Furthermore, this invention has good environmental adaptability; in addition to snow blindness scenarios, it can be extended to the assessment and verification of visual clarity under other low-visibility complex weather conditions such as sandstorms and haze, demonstrating broad applicability and promising prospects for promotion.

[0085] Although the invention has been described with reference to a limited number of embodiments, those skilled in the art will understand from the foregoing description that other embodiments are conceivable within the scope of the invention described herein. Furthermore, it should be noted that the language used in this specification has been chosen primarily for readability and instructional purposes, and not for the purpose of interpreting or limiting the subject matter of the invention. Therefore, many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure of the invention is illustrative and not restrictive, and the scope of the invention is defined by the appended claims.

Claims

1. A helicopter snow-blind visibility measurement method based on image processing, characterized in that, Specifically, the following steps are included: S1. Select a test environment and test site that meet the test conditions; S2. Develop a flight test plan covering takeoff, landing, and hovering, and determine the operating parameters for the test; S3. According to the flight conditions determined in S2, the helicopter (1) pilot first conducts simulation training on the simulator, and then conducts test flights on snowless ground. S4. After confirming the test location of the helicopter (1) at the test site, install the equipment used for the test; S5. Determine whether the existing snow cover at the test site meets the test requirements for creating a snow blind scenario that can be blown up by the rotor downwash. If the snow cover meets the test requirements, proceed directly to step S6. If the existing natural snow cover does not meet the test requirements, measures must be taken to make the ground snow cover meet the test requirements. S6. Before the flight test, the maintenance personnel shall complete the routine inspection and system verification of the helicopter (1); install a digital camera (5) in the cockpit of the helicopter (1); the digital camera (5) shall be positioned in the direction of the pilot's or crew's line of sight to record the image data of the blackbody target (3) from the cockpit view, and the field of view of the digital camera (5) shall include an unobstructed sky background (6). S7. Conduct a takeoff test of the helicopter (1) according to the determined flight conditions; S8. Conduct a landing test of the helicopter (1) according to the determined flight conditions; S9. After a single test vehicle is completed, once the helicopter (1) has completely stopped outputting power, ground personnel should promptly remove the snow from the surface of the fuselage and rotor to ensure equipment safety and the reliability of subsequent tests. S10. Confirm if there are any remaining tests for the day; if there are remaining test tasks for the day, proceed to S6; if all tests for the day are completed, proceed to S11. S11. Data processing is performed on the images acquired by the digital camera (5) during the experiment to obtain the change in visibility of the cockpit during snow blindness in the take-off and landing phase of the helicopter (1). The image processing method is as follows: By cropping the area of ​​the blackbody target (3) in the image, the apparent brightness of the blackbody target (3) observed by the digital camera (5) is obtained. Including the attenuated intrinsic brightness of the blackbody target (3) and the brightness of the air column ,Right now ; Let the distance between the digital camera (5) in the cockpit and the blackbody target (3) be... According to Beer-Lambert's law, the inherent brightness of the blackbody target (3) is... After a distance of R Afterwards, the brightness decreased to ,in The atmospheric extinction coefficient in the optical path between the digital camera (5) and the blackbody target 3 is defined as the average atmospheric extinction coefficient in the optical path between the digital camera (5) and the blackbody target 3. ,but ; Similarly, by cropping the sky region from the image, the apparent brightness of the sky background (6) observed by the digital camera (5) is obtained. ,in The inherent brightness of the sky background (6); assuming that the external lighting conditions remain stable during the experiment and the sky brightness does not change significantly over time, the apparent brightness of the sky background (6) in the environmental reference image collected when the helicopter (1) rotor airflow has not disturbed the snow accumulation on the ground is [value missing]. ; The inherent brightness of blackbody target 3 Approximately 0, from the above equations we can obtain: ； ； ； ； The average extinction coefficient between the digital camera (5) and the blackbody target (3) was obtained. Visibility values ​​can be obtained from Koschmieder's law. ,in The human eye contrast threshold is set to 0.02, resulting in a final visibility value. ; S12. Based on the image data processing results, evaluate the visibility value of the helicopter (1) during take-off and landing in snow blindness under different test conditions in the snowy environment, and evaluate the impact of different test conditions on the severity of snow blindness.

2. The helicopter snow blindness visibility measurement method based on image processing according to claim 1, characterized in that, The flight conditions described in S2 include the takeoff weight of the helicopter (1), the flight altitude of the helicopter (1) as a function of time, the hovering altitude, and the altitude holding time.

3. The helicopter snow blindness visibility measurement method based on image processing according to claim 1, characterized in that, When the existing natural snow cover at the test site described in S5 cannot meet the requirements of the snow blindness test, the following measures must be taken: If the existing snow cover is too thin, or if the surface layer becomes hardened due to sunlight, wind erosion, or other reasons, making it difficult to be disturbed by airflow, then it is necessary to improve the surface snow layer condition by manually loosening the snow layer, collecting snow from other areas, or supplementing with artificial snowfall, so as to meet the snow blindness generation conditions required for the experiment.

4. The helicopter snow blindness visibility measurement method based on image processing according to claim 1, characterized in that, The helicopter (1) is a full-size manned helicopter and must be equipped with standard helicopter flight instruments.

5. The helicopter snow blindness visibility measurement method based on image processing according to claim 1, characterized in that, The standard flight instruments of the helicopter (1) include flight data recording equipment and weather sensors.

6. The helicopter snow blindness visibility measurement method based on image processing according to claim 1, characterized in that, In the same test vehicle, the parameters of the digital camera (5) remain unchanged. During each image acquisition, a laser rangefinder and other precision ranging equipment are used to accurately determine the distance between the digital camera (5) in the cockpit and the blackbody target (3).

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