CN113238288B - Rotor wing target feature extraction method based on difference spectral line - Google Patents
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Abstract
The invention discloses a rotor wing target characteristic extraction method based on difference spectral lines, which is characterized by comprising the following steps of: 1) constructing a rotor wing target blade and a vortex electromagnetic wave model; 2) processing the simulation data by using a spectral decomposition method to obtain a difference spectral line; 3) and (3) changing the number of the blades, the length of the blades, the width of the blades and the position angle of the blades, and repeating the step 2) to respectively obtain difference spectral lines influencing the OAM. The method can accurately acquire the blade characteristics of the rotor target, thereby improving the precision of detecting and identifying the rotor target.
Description
Technical Field
The invention relates to the field of electromagnetic vortex target detection, in particular to a rotor wing target feature extraction method based on a difference spectral line.
Background
Nowadays, in people's social life, many rotor crafts have not been enough, and the big outbreak of unmanned aerial vehicle industry is widely used in fields such as aerial photography, agriculture, military affairs, and unmanned aerial vehicle belongs to typical rotor target. The frequent appearance of rotor target brings convenience in the life of giving people, has also brought some potential safety hazards, like unmanned aerial vehicle "black flight" incident frequently in recent years, uses unmanned aerial vehicle to carry out malicious investigation and monitoring, direct attack crowd etc.. However, a rotor target has the characteristics of a "low, slow, small" target, and the rotor target can hover in the air at any time, which is not detectable at all for conventional radars.
In recent years, with the introduction of vortex electromagnetic waves carrying Orbital Angular Momentum (OAM), a new angle and a new method are provided for the field of target detection for people, theoretically, the vortex electromagnetic waves have infinite different topological charge numbers, namely modes of orbital angular momentum, for convenience of calculation, the modes generally take integers, the modes of different orbital angular momentum are orthogonal to each other, namely the vortex electromagnetic waves with different modal numbers can be linearly superposed, and the property shows that the vortex electromagnetic waves with different modal numbers can be physically separated.
Aiming at the rotor target, no matter the rotor target is in a flying state or a hovering state, the spiral blades of the rotor target are always in rotation, the number, the length, the width and the like of the blades of the rotor target can be different according to different types of the rotor targets, and the different characteristics can be used as detection and identification bases for the rotor target.
Disclosure of Invention
The invention aims to provide a rotor wing target feature extraction method based on difference spectral lines, aiming at the defects of the prior art. The method can accurately acquire the blade characteristics of the rotor wing target, thereby improving the precision of detecting and identifying the rotor wing target.
The technical scheme for realizing the purpose of the invention is as follows:
a rotor wing target characteristic extraction method based on difference spectral lines is different from the prior art and comprises the following steps:
1) constructing a rotor target blade and vortex electromagnetic wave model: adopting feko electromagnetic simulation software to construct a simulation model of a rotor target blade and vortex electromagnetic waves, generating vortex electromagnetic waves by forming a circular array by 8 dipole antennas which are arranged at equal intervals, sequentially applying signal excitation sources with the same amplitude and gradually increased phase to the array elements with the frequency of the array elements being 10GHz and the radius of the array being 30mm, namely the length of one wavelength, generating vortex electromagnetic waves with different modal numbers, a sampling circumference with the radius of 30mm is arranged at the position 300mm above the circular array, the radius of the sampling circumference is 30mm consistent with the radius of the circular array, the number of sampling points is 360 points, a rotor wing target spiral blade model is arranged between the circular array and the sampling circumference, namely at a position 150mm above the circular array, and parameters such as the number of blades, the length of the blades, the width of the blades and the position angle of the blades of the rotor wing target spiral blade model can be adjusted;
2) obtaining a difference spectral line: changing the phase of an excitation source, generating vortex electromagnetic waves with different modal numbers, emitting the vortex electromagnetic waves with different modal numbers, and carrying out spectral decomposition method processing on simulated data by adopting MATLAB to obtain a difference spectral line, wherein the method specifically comprises the following steps: firstly, rotor target helical blades are not added between the circular array and the sampling circumference, namely, the vortex electromagnetic waves directly reach the sampling circumference, and the circular array antenna respectively emits the vortex electromagnetic waves with the modal numbers of 0, 1, 2 and 3 to obtain a group of simulation data as a comparison group; and then, a rotor target spiral blade is added between the circular array and the sampling circumference, the circular array antenna respectively emits vortex electromagnetic waves with the modal numbers of 0, 1, 2 and 3, and the vortex electromagnetic waves reach the sampling circumference after being influenced by the blades to obtain a group of simulation data as an experimental group. Because the mode numbers are mutually orthogonal, drawing a mode spectrogram of the vortex electromagnetic wave by a spectral decomposition method, and subtracting the mode spectrum of the control group from the mode spectrum of the experimental group to obtain a mode difference value spectral line, namely a difference value spectral line for short;
3) obtaining a difference spectral line influencing OAM: changing the number of blades, the length of the blades, the width of the blades and the position angle of the blades, repeating the step 2) to obtain a plurality of groups of simulation data as experimental group data, respectively obtaining difference spectral lines influencing OAM, and obtaining the difference spectral lines by the difference spectral lines: the number, the length and the width of the blades have great influence on high-mode vortex electromagnetic waves and small influence on low modes; the number of the blades takes the main mode as a central axis, the number of the blades is taken as a stepping number to influence the secondary mode, the influence of the blades on OAM is irrelevant to the position angle, the speed of electromagnetic waves is far greater than the rotation speed of a propeller, and the propeller can be regarded as a static state with different position angles for the electromagnetic waves, so that the influence of the rotating blades on OAM is equivalent to the influence of the static blades on OAM, the change of a secondary mode spectrum is analyzed, whether a rotor target exists can be judged, the parameter characteristics of the rotor target blades are obtained, and the accuracy is improved for the detection and the identification of the rotor target.
Compared with the prior radar detection rotor wing target, the technical scheme has the following characteristics:
the invention constructs a model of a rotor target blade and vortex electromagnetic waves, the rotor target can cause influence on the mode number of the vortex electromagnetic waves by taking the blade number as a period, the influence is irrelevant to the position angle of the rotor target blade, and whether the rotor target is in a flying state or a hovering state, the spiral blade is always in a rotating state, so whether the rotor target exists in a range can be effectively judged by observing the change of a vortex electromagnetic wave mode spectrum, if the rotor target exists, the blade characteristic of the rotor target can be extracted, and the type identification of the rotor target is realized.
The method can accurately acquire the blade characteristics of the rotor target, thereby improving the precision of detecting and identifying the rotor target.
Drawings
FIG. 1 is a schematic view of an embodiment of a rotor target blade and a vortex electromagnetic wave model;
fig. 2 is a difference spectrum diagram after the OAM is affected by the blade numbers of 2, 3, and 4 in the embodiment, in which fig. 2 (a) shows the effect of different blade numbers on the vortex electromagnetic waves with the mode numbers of 0 and 1, and fig. 2 (b) shows the effect of different blade numbers on the vortex electromagnetic waves with the mode numbers of 2 and 3;
fig. 3 is a difference spectrum chart of the blade lengths of 30mm, 70mm and 120mm respectively after the OAM is affected in the embodiment, in which fig. 3 (a) shows the results of different blade lengths affecting the vortex electromagnetic waves with the mode numbers of 0 and 1, and fig. 3 (b) shows the results of different blade lengths affecting the vortex electromagnetic waves with the mode numbers of 2 and 3;
fig. 4 is a difference spectrum diagram after the blade widths of 10mm and 20mm respectively affect OAM in the embodiment, wherein fig. 4 (a) shows the results of different blade widths affecting vortex electromagnetic waves with mode numbers of 0 and 1, and fig. 4 (b) shows the results of different blade widths affecting vortex electromagnetic waves with mode numbers of 2 and 3;
fig. 5 is a difference spectrum diagram of the blade position angles of 0 °, 20 ° and 80 ° in the embodiment after the influence is generated on the vortex electromagnetic wave with the mode numbers of 0 and 1.
Detailed Description
The invention will be further illustrated, but not limited, by the following description, with reference to the accompanying drawings and examples.
Example (b):
a rotor wing target feature extraction method based on difference spectral lines comprises the following steps:
1) constructing a rotor target blade and vortex electromagnetic wave model: adopting feko electromagnetic simulation software to construct a simulation model of a rotor wing target blade and vortex electromagnetic waves, as shown in fig. 1, the vortex electromagnetic wave generates a circular array composed of 8 dipole antennas arranged at equal intervals, each dipole array element antenna has a frequency of 10GHz and an array radius of 30mm, that is, a wavelength length, signal excitation sources with the same amplitude and gradually increased phases are sequentially applied to the array elements, the frequency of the array elements is 10GHz, vortex electromagnetic waves with different modal numbers are generated, a sampling circumference with the radius of 30mm is arranged at the position 300mm above the circular array, the radius of the sampling circumference is 30mm consistent with the radius of the circular array, the number of sampling points is 360 points, a rotor wing target spiral blade model is arranged between the circular array and the sampling circumference, namely 150mm above the circular array, and the number of blades, the length of the blades, the width of the blades and the position angle parameters of the blades of the rotor wing target spiral blade model are adjustable;
2) obtaining a difference spectral line: changing the phase of an excitation source, generating vortex electromagnetic waves with different modal numbers, emitting the vortex electromagnetic waves with different modal numbers, and carrying out spectral decomposition method processing on simulated data by adopting MATLAB to obtain a difference spectral line, wherein the method specifically comprises the following steps: rotor target spiral blades are not added between the circular array and the sampling circumference, namely, vortex electromagnetic waves directly reach the sampling circumference, and the circular array antenna respectively transmits the vortex electromagnetic waves with the modal numbers of 0, 1, 2 and 3 to obtain a group of simulation data as a comparison group; and then, a rotor target spiral blade is added between the circular array and the sampling circumference, the circular array antenna respectively emits vortex electromagnetic waves with the modal numbers of 0, 1, 2 and 3, and the vortex electromagnetic waves reach the sampling circumference after being influenced by the blades to obtain a group of simulation data as an experimental group. All the modal numbers are mutually orthogonal, a modal spectrogram of the vortex electromagnetic wave is drawn through a spectral decomposition method, and a modal difference spectrogram is obtained by subtracting the modal spectrum of the control group from the modal spectrum of the experimental group;
3) obtaining a difference spectral line influencing OAM: changing the number of blades, the length of the blades, the width of the blades and the position angle of the blades, and repeating the step 2) to obtain a plurality of groups of simulation data as experimental group data, specifically:
3-1) changing the number of blades, setting the length of the blades to be 120mm, obtaining a difference spectral line of the blade number on the OAM, wherein as shown in FIG. 2, the abscissa corresponding to the difference spectral line being less than 0 in the graph is the number of modes for emitting vortex electromagnetic waves, namely the main mode, the main mode is reduced in ratio and the secondary mode is increased in ratio due to the influence of the blades, when the blade number is 2, the secondary mode is larger in ratio change and takes the main mode as a central axis, and 2 as a stepping secondary mode, for example, when the main mode is 0, the secondary mode is larger in ratio change and is-4, -2, 4; when the number of the blades is 3, the ratio of the secondary mode is changed greatly by taking the main mode as a central axis and taking 3 as a stepped secondary mode, and compared with fig. 2 (a) and fig. 2 (b), the ratio of the difference spectral lines when the main mode is 3 is reduced most, namely, the influence of the blades on the high-mode vortex electromagnetic waves is larger than that of the low-mode vortex electromagnetic waves;
3-2) setting the number of the blades to be 3, changing the lengths of the blades to be 30mm, 70mm and 120mm respectively, and obtaining difference spectral lines of the lengths of the blades on OAM (operation administration and maintenance) influences, as shown in fig. 3, as can be seen from fig. 3 (a) and 3 (b), as the lengths of the blades increase, the primary mode ratio decreases more, the caused influence is larger, and the secondary mode ratio changes more greatly are both the primary mode as a central axis and the 3 as a stepped secondary mode;
3-3) the number of the blades is 3, the widths of the blades are changed to be 10mm and 20mm respectively, and the lengths of the blades are changed to be 120mm, so as to obtain a difference spectral line of the blade widths on the OAM influence, as shown in fig. 4, as can be seen from fig. 4 (a) and 4 (b), the larger the influence caused by the increase of the blade widths, the larger the change of the ratio of the secondary modes is, the primary mode is taken as the central axis, and the 3 is taken as the stepped secondary mode;
3-3) changing the position angle of the blade to be 0 degree, 20 degrees and 80 degrees respectively, the number of the blades is 3, the length is 120mm, obtaining a difference spectral line of the influence of the position angle of the blade on OAM, as shown in fig. 5, overlapping three lines, showing that the influence of the blade on OAM is irrelevant to the position angle, as the speed of electromagnetic wave is far greater than the rotation speed of the propeller, the propeller can be regarded as a static state of different position angles for the electromagnetic wave, so that the influence of the rotating blade on OAM can be presumed to be equivalent to the influence of the static blade on OAM, the influence of the rotating blade on OAM is equivalent to the influence of the static blade on OAM, analyzing the change of the sub-modal spectrum, judging whether a rotor target exists, obtaining the parameter characteristics of the rotor target blade, and improving the accuracy for the detection and identification of the rotor target.
Claims (1)
1. A rotor wing target feature extraction method based on difference spectral lines is characterized by comprising the following steps:
1) constructing a rotor target blade and vortex electromagnetic wave model: adopting feko electromagnetic simulation software to construct a simulation model of a rotor target blade and vortex electromagnetic waves, generating vortex electromagnetic waves by forming a circular array by 8 dipole antennas which are arranged at equal intervals, sequentially applying signal excitation sources with the same amplitude and gradually increased phase to the array elements with the frequency of the array elements being 10GHz and the radius of the array being 30mm, namely the length of one wavelength, generating vortex electromagnetic waves with different modal numbers, a sampling circumference with the radius of 30mm is arranged at the position 300mm above the circular array, the radius of the sampling circumference is 30mm consistent with the radius of the circular array, the number of sampling points is 360 points, a rotor wing target spiral blade model is arranged between the circular array and the sampling circumference, namely 150mm above the circular array, and the number of blades, the length of the blades, the width of the blades and the position angle parameters of the blades of the rotor wing target spiral blade model are adjustable;
2) obtaining a difference spectral line: changing the phase of an excitation source, generating vortex electromagnetic waves with different modal numbers, transmitting the vortex electromagnetic waves with different modal numbers, and carrying out spectral decomposition method processing on simulated data by adopting MATLAB to obtain a difference spectral line, wherein the method specifically comprises the following steps: rotor target spiral blades are not added between the circular array and the sampling circumference, namely, vortex electromagnetic waves directly reach the sampling circumference, and the circular array antenna respectively transmits the vortex electromagnetic waves with the modal numbers of 0, 1, 2 and 3 to obtain a group of simulation data as a comparison group; then, adding rotor target helical blades between the circular array and the sampling circumference, respectively emitting vortex electromagnetic waves with the modal numbers of 0, 1, 2 and 3 by the circular array antenna, influencing the vortex electromagnetic waves by the blades and reaching the sampling circumference to obtain a group of simulation data as an experimental group, drawing a modal spectrogram of the vortex electromagnetic waves by a spectral decomposition method due to mutual orthogonality among the modal numbers, and subtracting the modal spectrum of the control group from the modal spectrum of the experimental group to obtain a modal difference spectrum, namely a difference spectrum for short;
3) obtaining a difference spectral line influencing OAM: changing the number of blades, the length of the blades, the width of the blades and the position angle of the blades, repeating the step 2) to obtain a plurality of groups of simulation data as experimental group data, respectively obtaining difference spectral lines influencing OAM, and obtaining the difference spectral lines by the difference spectral lines: the number, the length and the width of the blades have great influence on high-mode vortex electromagnetic waves and small influence on low modes; the number of the blades takes the main mode as a central axis, the number of the blades is taken as a stepping number, the secondary mode is influenced, the influence of the blades on OAM is irrelevant to the position angle, the speed of electromagnetic waves is far greater than the rotation speed of a propeller, and for the electromagnetic waves, the propeller can be regarded as a static state of different position angles, so that the influence of the rotating blades on OAM is equivalent to the influence of the static blades on OAM, the change of a secondary mode spectrum is analyzed, whether a rotor target exists can be judged, and the parameter characteristics of the rotor target blades can be obtained.
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