A method of remote sensing of air target velocity vector

Abstract

The present invention discloses a method for remote sensing the velocity vector of an aerial target, comprising: emitting an annular beam with linear divergence characteristics through a laser radar system; splitting the receiving system into two paths, one path using a range detector to obtain the target's distance, and the other path using an array sensor to obtain the target's azimuth; establishing a three-dimensional coordinate system, and calculating the target's three-dimensional spatial coordinates relative to the laser radar system based on the annular beam's divergence characteristics, distance, and azimuth, and recording a timestamp; when the target passes through the annular beam multiple times, clustering the data points based on spatiotemporal characteristics: data continuously collected at the same location are assigned to the same cluster; averaging the data belonging to the same cluster; and calculating the target's velocity vector relative to the laser radar system when two clusters of valid data exist with different azimuths. The present invention can quickly and accurately obtain the target's spatial position and velocity vector under a simple background.

Description

Technical Field

[0001] The invention belongs to the technical field of laser radar detection, and in particular relates to a remote sensing method for air target velocity vectors. Background Art

[0002] As an active remote sensing technology, LiDAR (Light Detection and Ranging) has been widely used in environmental monitoring, target detection, and terrain mapping.

[0003] Conventional LiDAR systems typically use mechanical rotation or galvanometer scanning to scan the laser beam point by point to acquire target information. In recent years, the development and application of technologies such as phased arrays and MEMS have improved the scanning speed and control accuracy of the laser beam. However, these methods still suffer from low scanning efficiency and insufficient dynamic target tracking capabilities. For high-speed aerial targets, these technologies struggle to quickly and synchronously acquire the target's three-dimensional position and velocity vector information.

[0004] While non-scanning LiDARs based on area array sensors can improve detection efficiency, they are limited by the matching of light field divergence characteristics with the target motion model, resulting in insufficient velocity vector calculation accuracy. Furthermore, target positioning accuracy is also limited by the resolution of the area array sensor.

[0005] Chinese patent documents with publication numbers CN118244287A and CN118243960A respectively propose ring-shaped light target velocity vector detection methods for atmospheric and ocean scattering media. However, they lack effective spatial coordinate solution methods and spatiotemporal clustering algorithms. Data aliasing can lead to invalid detection of velocity vectors, and the system has poor robustness.

[0006] Chinese patent document CN118778143A proposes using two single-pixel detectors to detect the distance and azimuth of a target respectively, thereby improving the detection frame rate. However, it does not take into account the different intensities of target reflection signals at different distances and cannot effectively extract the azimuth of the target. Summary of the Invention

[0007] The present invention provides an aerial target velocity vector remote sensing method, which can quickly and accurately obtain the spatial position and velocity vector of the target under a simple background.

[0008] A method for remote sensing an aerial target velocity vector comprises the following steps:

[0009] (1) The laser radar system emits an annular beam with linear divergence characteristics, and the divergence characteristics satisfy ,in For annular beam transmission distance The radius at is the divergence constant;

[0010] (2) The receiving system is divided into two paths, one of which obtains the distance of the target through the ranging detector , the other way is to obtain the azimuth of the target through the array sensor ;

[0011] (3) Establish a three-dimensional coordinate system based on the divergence characteristics of the annular beam ,distance and azimuth , solve and obtain the three-dimensional coordinates of the target relative to the lidar system , and record the timestamp ;

[0012] (4) When the target passes through the annular beam multiple times, the data points are clustered based on spatiotemporal features: data collected continuously at the same location are assigned to the same cluster;

[0013] (5) Perform average processing on the data belonging to the same cluster. When there are two clusters of valid data with different azimuths, the average value of the spatiotemporal coordinates of the two clusters of data is used. and Calculate the velocity vector of the target relative to the lidar system .

[0014] Preferably, in step (1), the annular light field with linear divergence characteristics can be modulated by a spatial light modulator, a phase plate, an axicon, a cylindrical mirror, etc., including but not limited to vortex light, perfect vortex light, Bessel-Gaussian light and other linearly divergent annular lights.

[0015] Preferably, in step (1), the operating wavelength of the laser radar is a short-wave infrared band in the atmospheric window.

[0016] Preferably, in step (2), the ranging detector is an avalanche photodiode, the array sensor is a CCD or CMOS sensor, and the azimuth angle of the target is extracted through image processing.

[0017] Preferably, in step (3), the origin of the three-dimensional coordinate system is the laser radar system, and the positive direction of the z-axis is the direction of the optical axis emitted by the laser radar system.

[0018] As a preference, in step (3), the three-dimensional coordinates of the target relative to the laser radar system are calculated. , the formula is:

[0019] ;

[0020] ;

[0021] .

[0022] Preferably, in step (4), the data points are clustered based on spatiotemporal features using the DBSCAN clustering algorithm, and the cluster radius R is positively correlated with the target size.

[0023] Preferably, after step (5), the following steps are further included:

[0024] The world coordinate system is constructed based on the initial position of the LiDAR system relative to the ground. When the LiDAR is scanning and rotating, the actual coordinates and velocity of the target are corrected according to the angle and angular velocity of the LiDAR scan:

[0025] ;

[0026] ;

[0027] .

[0028] in, is the horizontal rotation angle of the lidar system, is the pitch angle of the lidar system, is the horizontal scanning angular velocity of the lidar system, is the pitch scanning angular velocity of the lidar system, is the target space coordinate based on the ground coordinate system, is the actual moving speed of the target, For the LiDAR system at a distance The scan line speed at .

[0029] Preferably, the transmitting optical path and the receiving optical path of the laser radar system are coaxial, so that the annular light beam emitted by the laser radar matches the center of the receiving field of view, thereby reducing the detection blind spot and simplifying the data processing process.

[0030] Preferably, the receiving system utilizes a spectrometer module to split the echo signal returned by the annular beam after it strikes the target, sending it to the ranging detector and area array sensor. The spectrometer module can utilize spectrometer components such as a prism or a beam splitter. The splitting ratio of the spectrometer component should be selected based on the sensitivity of the detector and area array sensor.

[0031] Preferably, a timing control device is used to synchronously trigger the pulse laser, ranging detector and array sensor of the laser radar; the timing control device has three outputs, and the relative delay of each output is calibrated according to the external triggering delay of the pulse laser, ranging detector and array sensor to achieve synchronization of multi-sensor timing signals and facilitate subsequent data fusion.

[0032] Preferably, the area array sensor has a gating function, which controls the opening and closing of the gate through the high and low levels of the timing control device signal to achieve the functions of delayed exposure and exposure time control, thereby suppressing invalid lidar backscatter signals and improving the signal-to-noise ratio.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The present invention can fully combine the divergence characteristics of the annular light beam, the orientation information of the area array sensor and the distance information collected by the detector, calculate the three-dimensional coordinates of the target, quickly and accurately obtain the spatial position of the target, and classify the data based on the clustering algorithm, thereby effectively realizing the accurate detection of the velocity vector. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The present invention provides a flow chart of a method for remotely sensing the velocity vector of an aerial target.

[0036] Figure 2 A schematic diagram showing the three-dimensional coordinates of the two contacts obtained by respectively solving the two contacts when a linearly diverging ring light contacts a moving target twice.

[0037] Figure 3 A linearly diverging ring light makes two contacts with a moving target. There are multiple valid data points for each contact. The sample diagram shows how the data is clustered according to spatiotemporal characteristics.

[0038] Figure 4 Schematic diagram of the structure of the laser radar system designed to implement the method of the present invention.

[0039] Figure 5 The distribution of 8 groups of motion trajectory samples at a set distance of 1000 m.

[0040] Figure 6 It is the comparison result of the set speed value and the solved speed and speed components. DETAILED DESCRIPTION

[0041] The present invention will be described in further detail below with reference to the accompanying drawings and examples. It should be noted that the following examples are intended to facilitate understanding of the present invention and do not have any limiting effect on the present invention.

[0042] A method for remote sensing of air target velocity vector, the specific flow chart is as follows Figure 1 As shown in the figure, the three-dimensional coordinates of the target space are calculated based on the divergence characteristics of the annular light beam, the distance information and the azimuth information. Then, data clustering is performed according to the spatiotemporal characteristics of the data. When the same target contacts the ring twice, two clusters of data can be obtained, and the velocity vector of the target can be calculated.

[0043] like Figure 2 As shown, the laser radar emits an annular beam with linear divergence characteristics, where the annular beam is The radius at A three-dimensional spatial coordinate system is constructed with the laser radar as a reference, where the z-axis coincides with the central axis of the annular beam. When the target moves through the annular beam at a certain speed, the spatial coordinates of the target can be obtained. .like Figure 3 As shown in the figure, due to the influence of target size and annular beam thickness, when the target passes through the annular beam, different parts of the target at the same spatial location will be illuminated by the annular beam and generate valid data, resulting in multiple sets of data at the same spatial location. Therefore, cluster analysis is required to classify valid data generated at the same spatial location into the same cluster. When the target passes through the annular beam twice, two clusters of data are generated.

[0044] Key components of the LiDAR system include Figure 4 As shown in the figure, the laser beam is collimated by a beam expander and then passes through an axicon to produce a ring-shaped beam. The receiving system and the transmitting system are designed in a coaxial mode. After the echo signal passes through the telescope, it is filtered out by a filter to remove interference light from other bands. The echo signal is then split into two by a spectroscope and received by the detector and array sensor respectively through a converging lens. The lidar system also has a timing control device to synchronize the triggering of the signals from the laser, array sensor, and detector acquisition module. Finally, the signals from the array sensor and detector acquisition module are processed by a computer to obtain the azimuth and distance information of the target.

[0045] In this embodiment, according to Figure 5 Set eight groups of target trajectories: (1) only moving in the x-axis direction and passing through the center of the annular beam; (2) only moving in the x-axis direction but not passing through the center of the annular beam; (3) only moving in the y-axis direction and passing through the center of the annular beam; (4) only moving in the y-axis direction but not passing through the center of the annular beam; (5) the x- and y-axis components are the same and pass through the center of the annular beam; (6) the x-, y-, and z-axis components are the same; (7) only the x-axis component is zero; (8) only the y-axis component is zero. Set the absolute speed of the target to 10 m / s and the distance from the lidar system to 1000 m.

[0046] Remote sensing of the target velocity vector is achieved through the following steps:

[0047] Step 1: Obtain the divergence characteristics of the annular beam emitted by the lidar and obtain the radius of the ring at different distances .

[0048] Step 2: By Figure 4The LiDAR system shown in the figure obtains information from the detector and the array sensor respectively. Through the timing control generator, the door opening time of the array sensor is delayed to 100 m and the door closing time is controlled to 3000 m to filter the near-field strong backscatter signal. Since the detector and the array sensor are triggered synchronously by the timing control generator, the distance information can be easily obtained. and azimuth information Timing synchronization.

[0049] Step 3: Based on the divergence characteristics of annular beam ,distance and azimuth , solve and obtain the three-dimensional coordinates of the target relative to the lidar system ;

[0050] ;

[0051] ;

[0052] .

[0053] in, , obtained from the first step.

[0054] Step 4: If Figure 3 As shown in FIG, when the target passes through the annular beam twice, a cluster analysis based on spatiotemporal features is performed on the data points to separate the data points generated during the two contacts.

[0055] Step 5: Average the valid data points belonging to the same cluster and calculate the average value of the spatiotemporal coordinates and , and thus calculate the target's velocity vector .

[0056] For 8 sets of motion trajectories, the comparison between the calculated velocity vector and the set value is as follows: Figure 6 As shown in the figure, the horizontal axis is the test sample number, and the vertical axes in the four sub-graphs are the absolute value of velocity and the magnitude of the velocity components on the x, y, and z axes, respectively. It can be seen that both the absolute value of velocity and the velocity components on each axis have a high degree of consistency with the set true value, demonstrating the high stability and accuracy of this method.

[0057] The embodiments described above provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements and equivalent substitutions made within the scope of the principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for remote sensing of air target velocity vector, characterized in that: The following steps are involved: (1) The laser radar system emits a circular beam with linear divergence characteristics, and the divergence characteristics satisfy ,in For annular beam transmission distance The radius at is the divergence constant; (2) The receiving system is divided into two paths, one of which obtains the distance of the target through the ranging detector , the other way is to obtain the azimuth of the target through the array sensor ; (3) Establish a three-dimensional coordinate system based on the divergence characteristics of the annular beam ,distance and azimuth , solve and obtain the three-dimensional coordinates of the target relative to the lidar system , and record the timestamp ; (4) When the target passes through the annular beam multiple times, the data points are clustered based on spatiotemporal features: data collected continuously at the same location are assigned to the same cluster; (5) Perform average processing on the data belonging to the same cluster. When there are two clusters of valid data with different azimuths, the average value of the spatiotemporal coordinates of the two clusters of data is used. and Calculate the velocity vector of the target relative to the lidar system .

2. The method for remote sensing of aerial target velocity vector according to claim 1, characterized in that: In step (2), the ranging detector is an avalanche photodiode, and the array sensor is a CCD or CMOS sensor, and the azimuth angle of the target is extracted through image processing.

3. The method for remote sensing of aerial target velocity vector according to claim 1, characterized in that: In step (3), the origin of the three-dimensional coordinate system is the laser radar system, and the positive direction of the z-axis is the direction of the laser radar system's emission optical axis.

4. The method for remote sensing of aerial target velocity vector according to claim 1, characterized in that: In step (3), the three-dimensional coordinates of the target relative to the lidar system are calculated , the formula is: ； ； 。 5. The method for remote sensing of aerial target velocity vector according to claim 1, characterized in that: In step (4), the DBSCAN clustering algorithm is used to cluster the data points based on spatiotemporal features, and the cluster radius R is positively correlated with the target size.

6. The method for remote sensing of aerial target velocity vector according to claim 1, characterized in that: After step (5), the following steps are also included: The world coordinate system is constructed based on the initial position of the LiDAR system relative to the ground. When the LiDAR is scanning and rotating, the actual coordinates and velocity of the target are corrected according to the angle and angular velocity of the LiDAR scan: ； ； ； in, is the horizontal rotation angle of the lidar system, is the pitch angle of the lidar system, is the horizontal scanning angular velocity of the lidar system, is the pitch scanning angular velocity of the lidar system, is the target space coordinate based on the ground coordinate system, is the actual moving speed of the target, For the LiDAR system at a distance The scan line speed at .

7. The method for remote sensing of aerial target velocity vector according to claim 1, characterized in that: The transmitting optical path and receiving optical path of the laser radar system are coaxial, so that the annular light beam emitted by the laser radar matches the center of the receiving field of view.

8. The method for remote sensing of aerial target velocity vector according to claim 1, characterized in that: The receiving system uses a spectrometer module to split the echo signal returned after the annular light beam hits the target into the ranging detector and the area array sensor.

9. The method for remote sensing of aerial target velocity vector according to claim 1, characterized in that: A timing control device is used to synchronously trigger the pulse laser, ranging detector and array sensor of the laser radar; the timing control device has three outputs, and the relative delay of each output is calibrated according to the external trigger delay of the pulse laser, ranging detector and array sensor to achieve synchronization of multi-sensor timing signals.

10. The method for remote sensing of aerial target velocity vector according to claim 9, characterized in that: The area array sensor has a gating function, which controls the opening and closing of the gate through the high and low levels of the timing control device signal, realizing the functions of delayed exposure and exposure time control, thereby suppressing invalid lidar backscatter signals and improving the signal-to-noise ratio.

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