Aircraft trailing vortex identification method based on connected domain identification

Abstract

The invention discloses an aircraft trailing vortex recognition method based on connected domain recognition, and relates to the technical field of atmospheric sciences, and the method comprises the steps: carrying out the scanning of a laser radar in a direction perpendicular to a runway, obtaining a two-dimensional radial velocity field and a spectral width field, and carrying out the recognition of the trailing vortex through employing the feature that the trailing vortex occurs in a whole continuous space; the method comprises the following steps: firstly, finding a communication region in which a trailing vortex possibly exists from a spectral wide field as a candidate trailing vortex region, and then further judging whether a two-dimensional radial velocity field conforms to trailing vortex characteristics in the candidate trailing vortex region to realize trailing vortex identification. The method comprehensively considers the characteristics of the trailing vortex on the spectral width field and the radial velocity field, has a high recognition rate, does not need a large amount of data for training compared with a neural network and deep learning recognition method, and is simple in algorithm, small in calculation amount, high in recognition efficiency and good in portability.

Description

Technical Field

[0001] The present application relates to the field of atmospheric science and technology, and in particular to an aircraft wake vortex identification method based on connected domain identification. Background Art

[0002] According to the principle of aerodynamics, when an aircraft is flying, the wings of the aircraft generate the main lift required for the flight of the aircraft. Compared with the lower surface of the wing, the pressure on the upper surface is small, and the airflow at the wing tip will flow from the lower surface to the upper surface at the wing tip, forming a pair of counter-rotating vortices, that is, generating wake vortices. Compared with the cruise phase, the aircraft is more likely to generate strong wake vortices during takeoff or landing, and the generated wake vortices will extend backward along the runway direction (i.e., the aircraft movement direction) and gradually spread to both sides of the runway (lateral expansion). The wake vortices pose a safety hazard to subsequent takeoff or landing aircraft. When an aircraft encounters the wake vortices of the previous aircraft, the fuselage may vibrate, sink, and even flip, and in severe cases, it may lead to the crash of the aircraft. Therefore, detecting and identifying the wake vortices of the aircraft to adjust the flight path of the subsequent aircraft in advance to avoid the wake vortices can improve the flight safety of the subsequent aircraft, which is of great significance.

[0003] Lidar has been recognized as one of the most effective tools for wake vortex detection due to its narrow beam width, high resolution, etc. Existing commonly used lidar-based identification methods are basically based on single spectral line (single range bin) features or single element features for identification. Although some wake vortices can be identified, the calculation efficiency is low and the misidentification rate is relatively high. In recent years, some people have also developed wake vortex identification methods based on deep learning or neural networks, which can improve the identification accuracy to a certain extent, but require a large amount of data for training and verification, with a large amount of calculation, and this method requires a large amount of data accumulation in the early stage and has poor portability. Summary of the Invention

[0004] In view of the above problems and technical requirements, the present application proposes an aircraft wake vortex identification method based on connected domain identification. The technical solution of the present application is as follows:

[0005] An aircraft wake vortex identification method based on connected domain identification, the aircraft wake vortex identification method includes:

[0006] Performing RHI scanning perpendicular to the runway direction by using lidar to obtain a two-dimensional radial velocity field and a spectral width field;

[0007] After performing binarization processing on the spectral width field by using a spectral width threshold, performing morphological processing and connected domain identification on the region reaching the spectral width threshold, and extracting candidate wake vortex regions;

[0008] For any candidate wake vortex region, when the velocity distribution feature of the two-dimensional radial velocity field in the candidate wake vortex region conforms to the wake vortex feature, it is determined that a wake vortex is identified at the candidate wake vortex region.

[0009] A further technical solution thereof is that detecting whether the velocity distribution characteristics of the two-dimensional radial velocity field in the candidate wake vortex region conform to the wake vortex characteristics includes:

[0010] Taking the geometric center of the candidate wake vortex region as the coordinate origin, and establishing a rectangular coordinate system with the horizontal direction and the vertical direction as the coordinate axes respectively to divide the candidate wake vortex region into four quadrant regions;

[0011] When it is detected that the two-dimensional radial velocity field in the first set of diagonal quadrant regions of the candidate wake vortex region is greater than the two-dimensional radial velocity field in the second set of diagonal quadrant regions, it is determined that the velocity distribution characteristics of the two-dimensional radial velocity field in the candidate wake vortex region conform to the wake vortex characteristics;

[0012] Wherein, the first set of diagonal quadrant regions includes the first quadrant region and the third quadrant region of the candidate wake vortex region, and the second set of diagonal quadrant regions includes the second quadrant region and the fourth quadrant region of the candidate wake vortex region.

[0013] A further technical solution thereof is that detecting whether the two-dimensional radial velocity field in the first set of diagonal quadrant regions of the candidate wake vortex region is greater than the two-dimensional radial velocity field in the second set of diagonal quadrant regions includes:

[0014] Calculating the average radial velocity of the two-dimensional radial velocity field in the candidate wake vortex region within the first set of diagonal quadrant regions, and calculating the average radial velocity of the two-dimensional radial velocity field in the candidate wake vortex region within the second set of diagonal quadrant regions;

[0015] When the average radial velocity in the first set of diagonal quadrant regions is less than the average radial velocity in the second set of diagonal quadrant regions, and the maximum radial velocity in the candidate wake vortex region is located in the second set of diagonal quadrant regions, and the minimum radial velocity in the candidate wake vortex region is located in the first set of diagonal quadrant regions, it is determined that the two-dimensional radial velocity field in the first set of diagonal quadrant regions of the candidate wake vortex region is greater than the two-dimensional radial velocity field in the second set of diagonal quadrant regions.

[0016] A further technical solution thereof is that the aircraft wake vortex recognition method further includes:

[0017] When the velocity distribution characteristics of the two-dimensional radial velocity field in the candidate wake vortex region conform to the wake vortex characteristics, and the geometric center of the candidate wake vortex region is within a predetermined space range, it is determined that the candidate wake vortex region is a wake vortex influence region, and the geometric center of the candidate wake vortex region is the vortex core position of the identified wake vortex.

[0018] A further technical solution thereof is that extracting the candidate wake vortex region includes:

[0019] Performing morphological processing and connected domain recognition on the region reaching the spectral width threshold to obtain a number of connected regions;

[0020] Filter out the connected regions within the preset area range and having predetermined shape features as candidate wake vortex regions.

[0021] A further technical solution thereof is that detecting whether the connected region conforms to the predetermined shape features includes:

[0022] Calculate the ratio of the length dimension along the horizontal direction to the width dimension along the vertical direction of the connected region to obtain the aspect ratio of the connected region;

[0023] When the aspect ratio of the connected region is within the preset aspect ratio range, it is determined that the connected region conforms to the predetermined shape features.

[0024] A further technical solution thereof is that obtaining the two-dimensional radial velocity field and the spectral width field includes:

[0025] After performing data quality control on the observation data of the RHI scan of the lidar, obtain the two-dimensional radial velocity field and the spectral width field.

[0026] The beneficial technical effects of this application are:

[0027] This application discloses an aircraft wake vortex recognition method based on connected domain recognition. This method utilizes the feature that the wake vortex occurs in a whole continuous space. First, find the connected regions where the wake vortex may exist on the spectral width field as candidate wake vortex regions, and then further determine whether the two-dimensional radial velocity field conforms to the wake vortex features within the candidate wake vortex regions. This method comprehensively considers the features of the wake vortex on the spectral width field and the radial velocity field, has a high recognition rate, and compared with the recognition methods of neural networks and deep learning, does not require a large amount of data for training, has a simple algorithm, a small amount of calculation, a high recognition efficiency, and good portability.

[0028] This method can eliminate the influence of background wind on the wake vortex, can effectively recognize the wake vortex both in calm wind and windy conditions, and can recognize the situation where there are multiple wake vortices at the same time, has a wide application range, and is easy to promote. Description of the Drawings

[0029] Figure 1 is a schematic flowchart of an aircraft wake vortex recognition method according to an embodiment of this application.

[0030] Figure 2 is a schematic flowchart of an aircraft wake vortex recognition method according to another embodiment of this application.

[0031] Figure 3 is the spectral width field obtained by lidar scanning in an example.

[0032] Figure 4 is based on Figure 3 the spectral width field extraction to obtain the candidate wake vortex region.

[0033] Figure 5Yes Figure 4 Schematic diagram of the coverage range of the extracted candidate wake vortex region on the two-dimensional radial velocity field obtained by lidar scanning and the schematic diagram of the finally extracted vortex core position. Detailed implementation manners

[0034] The following further describes the detailed implementation manners of the present application with reference to the accompanying drawings.

[0035] The present application discloses an aircraft wake vortex recognition method based on connected component recognition. Please refer to Figure 1 the shown flowchart. The aircraft wake vortex recognition method includes the following steps:

[0036] Step S1: Use lidar to perform RHI scanning perpendicular to the runway direction to obtain a two-dimensional radial velocity field and a spectral width field. Since an aircraft is more likely to generate strong wake vortices during takeoff or landing, posing a safety hazard to subsequent takeoff or landing aircraft, the aircraft wake vortex recognition method of the present application is also more commonly applied in this scenario. The wake vortices move along the runway direction and spread to both sides. Therefore, when the lidar scans perpendicular to the runway, it can cut across the path of the wake vortices, making it easier to capture the lateral movement of the vortices from the two-dimensional radial velocity field and the spectral width field.

[0037] The detection area of the lidar covers a predetermined width range in the horizontal direction and a predetermined height range in the vertical direction. Additionally, after completing the RHI scanning to obtain the observation data, the observation data is further subjected to data quality control to obtain the two-dimensional radial velocity field and the spectral width field to prevent misrecognition caused by clutter interference. The data quality control methods mainly include operations such as outlier removal and missing value filling.

[0038] Step S2: After binarizing the spectral width field using a spectral width threshold, perform morphological processing and connected component recognition on the area that reaches the spectral width threshold, and extract the candidate wake vortex region.

[0039] The spectral width threshold in this step is set customarily. The morphological processing includes first performing a dilation operation and then an erosion operation. The wake vortices occur in a continuous space as a whole, and the wake vortices will cause an increase in the spectral width. Therefore, in this step, the connected regions where the wake vortices may exist are first found from the spectral width field to achieve the first-stage screening.

[0040] In one embodiment, to improve the accuracy of the extracted candidate wake vortex region, the connected regions obtained after completing the morphological processing and connected component recognition are not directly used as the candidate wake vortex region, but are further screened, including the following steps. Please refer to Figure 2 the flowchart: After performing morphological processing and connected component recognition on the area that reaches the spectral width threshold to obtain several connected regions, screen out the connected regions with an area within a preset area interval and having a predetermined shape feature as the candidate wake vortex region.

[0041] Regarding the shape characteristics of the connected region, the aspect ratio of the connected region is calculated by obtaining the ratio of the length dimension along the horizontal direction to the width dimension along the vertical direction of the connected region. When the aspect ratio of the connected region is within the preset aspect ratio range, it can be determined that the connected region conforms to the predetermined shape characteristics.

[0042] The wake vortex scale is positively correlated with the wingspan of the aircraft. Therefore, the reasonable intervals of the area and aspect ratio of the region where the spectral width increases caused by the wake vortex can be determined in advance. The reasonable interval of the area is set as the preset area range, and the reasonable interval of the aspect ratio is set as the preset aspect ratio range. Thus, further identification of the connected region from both the area and shape aspects can reduce the misidentification in the first stage. The selected candidate wake vortex regions enter step S3 for the second-stage identification, and other connected regions are filtered out and no longer judged.

[0043] Step S3: For any candidate wake vortex region, when the velocity distribution characteristics of the two-dimensional radial velocity field within the candidate wake vortex region conform to the wake vortex characteristics, it is determined that a wake vortex is identified at the candidate wake vortex region. It includes the following steps:

[0044] First, taking the geometric center of the candidate wake vortex region as the coordinate origin, and taking the horizontal direction and the vertical direction as the coordinate axes respectively, a rectangular coordinate system is established to divide the candidate wake vortex region into four quadrant regions, namely the first quadrant region, the second quadrant region, the third quadrant region, and the fourth quadrant region. The distribution positions of the four quadrant regions are defined using the standard quadrant division.

[0045] If the candidate wake vortex region is a wake vortex influence region, then the geometric center of the candidate wake vortex region is the position of the aircraft, that is, the position of the vortex core of the wake vortex. Affected by the wake vortex, the distribution of the radial velocity within the four quadrant regions will change and show specific wake vortex characteristics: when it is detected that the two-dimensional radial velocity field in the first set of diagonal quadrant regions of the candidate wake vortex region is greater than the two-dimensional radial velocity field in the second set of diagonal quadrant regions, it is determined that the velocity distribution characteristics of the two-dimensional radial velocity field within the candidate wake vortex region conform to the wake vortex characteristics, and it is determined that a wake vortex is identified at the candidate wake vortex region. Among them, the first set of diagonal quadrant regions includes the first quadrant region and the third quadrant region of the candidate wake vortex region, and the second set of diagonal quadrant regions includes the second quadrant region and the fourth quadrant region of the candidate wake vortex region.

[0046] Theoretically, when the influence of the background wind is not considered, the radial velocity in the first set of diagonal quadrant regions is negative, and the radial velocity in the second set of diagonal quadrant regions is positive. However, in the actual environment, it is always affected by the background wind, resulting in the radial velocities in the four quadrant regions not having an absolute positive-negative relationship, but only relative large-value and small-value regions. Therefore, in this embodiment, the identification is not based on detecting the positive and negative of the radial velocity in the two sets of diagonal quadrant regions, but on detecting the relative magnitude relationship of the radial velocities in the two sets of diagonal quadrant regions, so as to exclude the influence of the background wind on the wake vortex and ensure effective wake vortex identification both in calm wind and windy conditions. Specifically:

[0047] First, calculate the average radial velocity of the two-dimensional radial velocity field in the first set of diagonal quadrant regions within the candidate wake vortex region, and calculate the average radial velocity of the two-dimensional radial velocity field in the second set of diagonal quadrant regions within the candidate wake vortex region. And determine the maximum radial velocity and the minimum radial velocity within the entire candidate wake vortex region.

[0048] When the average radial velocity in the first set of diagonal quadrant regions is less than the average radial velocity in the second set of diagonal quadrant regions, and the maximum radial velocity within the candidate wake vortex region is located in the second set of diagonal quadrant regions, and the minimum radial velocity within the candidate wake vortex region is located in the first set of diagonal quadrant regions, it is determined that the two-dimensional radial velocity field in the first set of diagonal quadrant regions within the candidate wake vortex region is greater than the two-dimensional radial velocity field in the second set of diagonal quadrant regions, so as to determine that the velocity distribution characteristics of the two-dimensional radial velocity field within the candidate wake vortex region conform to the wake vortex characteristics.

[0049] Furthermore, after determining that the velocity distribution characteristics of the two-dimensional radial velocity field within the candidate wake vortex region conform to the wake vortex characteristics, it is not directly determined that the candidate wake vortex region is the wake vortex influence region, but further screening is carried out to improve the identification accuracy, including: when the velocity distribution characteristics of the two-dimensional radial velocity field within the candidate wake vortex region conform to the wake vortex characteristics, and the geometric center of the candidate wake vortex region is within a predetermined spatial range, it is finally determined that the candidate wake vortex region is the wake vortex influence region, and the geometric center of the candidate wake vortex region is the vortex core position of the identified wake vortex.

[0050] That is, after determining that the velocity distribution characteristics conform to the wake vortex characteristics, further judge whether the spatial position of the geometric center of the candidate wake vortex region is reasonable. This is because the wake vortex can only appear in the runway centerline and the areas on both sides in the horizontal direction, and can also only appear within a fixed height range in the vertical direction. Therefore, it can be determined that the range covering the runway centerline and the areas on both sides in the horizontal direction and covering the predetermined height interval in the vertical direction is the predetermined spatial range, and this predetermined spatial range is the reasonable region where the wake vortex appears. This step can further eliminate the wake vortices with unreasonable positions, thereby improving the identification accuracy and reliability.

[0051] For example, in one example, the wide-field spectrum obtained by using a laser radar to perform RHI scanning in the direction perpendicular to the runway is as follows: Figure 3 The two-dimensional radial velocity field is shown as Figure 5 Based on Figure 3 The candidate tail vortex regions extracted from the wide-field spectrum are as follows Figure 4 As shown in the red area in the figure. Figure 5 Whether the velocity distribution characteristics of the two-dimensional radial velocity field in the candidate wake vortex area 300 meet the wake vortex characteristics, it is finally determined that the candidate wake vortex area 300 is the wake vortex influence area, and the geometric center O of the candidate wake vortex area 300 is the aircraft position and also the position of the vortex core.

[0052] The above is only a preferred embodiment of the present application, and the present application is not limited to the above embodiments. It is understood that other improvements and changes directly derived or associated by those skilled in the art without departing from the spirit and concept of the present application should be considered to be included in the protection scope of the present application.

Claims

1. An aircraft wake vortex recognition method based on connected component recognition, characterized in that, The aircraft wake vortex identification method includes: Performing RHI scanning perpendicular to the runway direction using a lidar to obtain a two-dimensional radial velocity field and a spectral width field; After performing binarization processing on the spectral width field using a spectral width threshold, performing morphological processing and connected component identification on the regions that reach the spectral width threshold, and extracting candidate wake vortex regions; For any candidate wake vortex region, when the velocity distribution characteristics of the two-dimensional radial velocity field within the candidate wake vortex region conform to the wake vortex characteristics, it is determined that a wake vortex is identified at the candidate wake vortex region.

2. The aircraft wake vortex recognition method according to claim 1, wherein, Detecting whether the velocity distribution characteristics of the two-dimensional radial velocity field within the candidate wake vortex region conform to the wake vortex characteristics includes: Taking the geometric center of the candidate wake vortex region as the coordinate origin, and establishing a rectangular coordinate system with the horizontal direction and the vertical direction as the coordinate axes respectively to divide the candidate wake vortex region into four quadrant regions; When it is detected that the two-dimensional radial velocity field within the first set of diagonal quadrant regions of the candidate wake vortex region is greater than the two-dimensional radial velocity field within the second set of diagonal quadrant regions, it is determined that the velocity distribution characteristics of the two-dimensional radial velocity field within the candidate wake vortex region conform to the wake vortex characteristics; Wherein, the first set of diagonal quadrant regions includes the first quadrant region and the third quadrant region of the candidate wake vortex region, and the second set of diagonal quadrant regions includes the second quadrant region and the fourth quadrant region of the candidate wake vortex region.

3. The aircraft wake vortex recognition method according to claim 2, wherein, Detecting whether the two-dimensional radial velocity field within the first set of diagonal quadrant regions of the candidate wake vortex region is greater than the two-dimensional radial velocity field within the second set of diagonal quadrant regions includes: Calculating the average radial velocity of the two-dimensional radial velocity field within the candidate wake vortex region within the first set of diagonal quadrant regions, and calculating the average radial velocity of the two-dimensional radial velocity field within the candidate wake vortex region within the second set of diagonal quadrant regions; When the average radial velocity within the first set of diagonal quadrant regions is less than the average radial velocity within the second set of diagonal quadrant regions, and the maximum radial velocity within the candidate wake vortex region is located within the second set of diagonal quadrant regions, and the minimum radial velocity within the candidate wake vortex region is located within the first set of diagonal quadrant regions, it is determined that the two-dimensional radial velocity field within the first set of diagonal quadrant regions of the candidate wake vortex region is greater than the two-dimensional radial velocity field within the second set of diagonal quadrant regions.

4. The aircraft wake vortex recognition method according to claim 1, wherein The aircraft wake vortex identification method further includes: When the velocity distribution characteristics of the two-dimensional radial velocity field within the candidate wake vortex region conform to the wake vortex characteristics, and the geometric center of the candidate wake vortex region is within a predetermined spatial range, it is determined that the candidate wake vortex region is a wake vortex influence region, and the geometric center of the candidate wake vortex region is the vortex core position of the identified wake vortex.

5. The aircraft wake vortex recognition method according to claim 1, characterized in that The extraction of candidate wake vortex regions includes: Performing morphological processing and connected component identification on the regions that reach the spectral width threshold to obtain a number of connected regions; Selecting the connected regions with an area within a preset area interval and having predetermined shape characteristics as candidate wake vortex regions.

6. The method for identifying aircraft wake vortices according to claim 5, wherein Detecting whether the connected regions conform to the predetermined shape characteristics includes: Calculating the ratio of the length dimension along the horizontal direction to the width dimension along the vertical direction of the connected region to obtain the aspect ratio of the connected region; When the aspect ratio of the connected region is within a preset aspect ratio range, it is determined that the connected region conforms to a predetermined shape feature.

7. The aircraft wake vortex recognition method according to claim 1, wherein The obtaining of the two-dimensional radial velocity field and the spectral width field includes: After performing data quality control on the observation data of the RHI scan of the lidar, a two-dimensional radial velocity field and a spectral width field are obtained.

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