Pulse Doppler echo simulation method for rotor unmanned aerial vehicle

Abstract

The invention particularly relates to a pulse Doppler echo simulation method for a rotor unmanned aerial vehicle, which comprises the following steps: enabling a fuselage to be equivalent to an isotropic scattering point, and simulating a radar echo signal of the fuselage based on the RCS of the scattering point of the fuselage and the distance between a radar and the gravity center of the fuselage; rotor blades are equivalent to a group of isotropic scattering points uniformly distributed on a straight line, and radar echo signals of the rotor scattering points are simulated based on the RCS of the rotor scattering points and the distance from the rotor scattering points to the gravity center of the fuselage; simulating a radar echo signal of a single blade based on the radar echo signal of the rotor wing scattering point, simulating a radar echo signal of a single rotor wing based on the radar echo signal of the single blade, and simulating radar echo signals of all rotor wings based on the radar echo signal of the single rotor wing; and simulating a pulse Doppler echo signal of the rotor unmanned aerial vehicle based on the radar echo signals of all the rotors, the radar echo signal of the fuselage and the echo signal noise. According to the method, the radar echo characteristics of the rotor unmanned aerial vehicle are simulated more truly.

Description

Technical Field

[0001] The invention relates to the technical field of echo modeling and simulation, and in particular to a pulse Doppler echo simulation method for a rotary-wing unmanned aerial vehicle. Background Art

[0002] There are three main modeling methods for the rotor echo model, namely, integral model, equivalent radar cross section (RCS) model and scattering point model.

[0003] The integral model regards the rotor blades as rigid lines with the same scattering coefficient, and then integrates them to finally obtain the corresponding radar echo model analytical expression.

[0004] The equivalent RCS model uses physical optics method, equivalent electromagnetic flow method, quasi-static method and other methods to calculate the RCS of the rotor blades, and then analyzes the time-frequency domain characteristics of the blades based on the time-frequency transformation method to obtain the rotor target echo model.

[0005] The scattering point model treats the blades as multiple strong scattering points and performs echo modeling on the motion state of the scattering points.

[0006] The integral model and equivalent RCS model focus more on the echo amplitude change, while the scattering point model focuses more on the echo phase change.

[0007] However, the rotor blades are simplified in the existing rotor UAV radar echo modeling, which can lead to significant deviations between the simulation results and the actual echo.

[0008] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present invention, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0009] The present invention provides a pulse Doppler echo simulation method for a rotary-wing UAV, which treats rotor blades as equivalent to a series of scattering points. Not only the reflection characteristics of a single blade are considered, but also the dynamic changes of the rotor blades under different flight states are comprehensively analyzed, thereby more realistically simulating the radar echo characteristics of the rotary-wing UAV.

[0010] Other features and advantages of the present invention will become apparent from the following detailed description, or may be learned in part by practice of the present invention.

[0011] According to a first aspect of the present invention, a pulse Doppler echo simulation method for a rotary-wing UAV is provided, the method comprising:

[0012] The fuselage is equivalent to an isotropic scattering point, and the radar echo signal of the fuselage is simulated based on the RCS of the fuselage scattering point and the distance between the radar and the center of gravity of the fuselage;

[0013] The rotor blades are equivalent to a set of isotropic scattering points evenly distributed on a straight line, and the radar echo signals of the rotor scattering points are simulated based on the RCS of the rotor scattering points and the distance from the rotor scattering points to the center of gravity of the fuselage;

[0014] The radar echo signal based on the rotor scattering point simulates the radar echo signal of a single blade, the radar echo signal based on the radar echo signal of a single blade simulates the radar echo signal of a single rotor, and the radar echo signal based on a single rotor simulates the radar echo signals of all rotors;

[0015] The pulse Doppler echo signal of the rotor UAV is simulated based on the radar echo signals of all rotors, the radar echo signal of the fuselage and the echo signal noise.

[0016] In some exemplary embodiments, two adjacent rotors of the rotorcraft rotate in opposite directions.

[0017] In some exemplary embodiments, the radar echo signal of the fuselage is simulated based on the RCS of the fuselage scattering point and the distance between the radar and the center of gravity of the fuselage, and the formula used is as follows:

[0018]

[0019] Among them, σ b is the RCS of the fuselage scattering point, c is the speed of light, t f Indicates fast time, f c Indicates the signal carrier frequency, R b Indicates the distance between the radar and the center of gravity of the fuselage.

[0020] In some exemplary embodiments, the radar echo signal of the rotor scattering point is simulated based on the RCS of the rotor scattering point and the distance from the rotor scattering point to the center of gravity of the fuselage, and the formula used is as follows:

[0021]

[0022] Among them, σ P is the RCS of the rotor scattering point, R P is the distance from the rotor scattering point to the center of gravity of the fuselage.

[0023] In some exemplary embodiments, the radar echo signal based on the rotor scattering point simulates the radar echo signal of a single blade, and the formula used is as follows:

[0024]

[0025] Among them, n s is the number of rotor scattering points for a single blade.

[0026] In some exemplary embodiments, the radar echo signal of a single rotor is simulated based on the radar echo signal of a single blade, and the formula used is as follows:

[0027]

[0028] Among them, n j is the number of blades of a single rotor.

[0029] In some exemplary embodiments, the radar echo signals of all rotors are simulated based on the radar echo signal of a single rotor, and the formula used is as follows:

[0030]

[0031] Among them, n k is the number of rotors with different angular velocities and initial phases.

[0032] According to a second aspect of the present invention, there is provided a storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the pulse Doppler echo simulation method for a rotary-wing UAV as described in the first aspect is implemented.

[0033] According to a third aspect of the present invention, there is provided a computer program product having a computer program stored thereon, and when the computer program is executed by a processor, the pulse Doppler echo simulation method for a rotary-wing UAV as described in the first aspect is implemented.

[0034] According to a fourth aspect of the present invention, there is provided an electronic device, comprising:

[0035] Processor; and

[0036] A memory, configured to store executable instructions of the processor;

[0037] Wherein, the processor is configured to implement the pulse Doppler echo simulation method of the rotorcraft UAV described in the first aspect by executing the executable instructions.

[0038] The pulse Doppler echo simulation method of the rotor UAV provided by the embodiment of the present invention represents the rotor blades with a set of isotropic scattering points evenly distributed on a straight line, and the fuselage with one isotropic scattering point; the model takes into account the reflection characteristics of a single rotor blade and the dynamic changes of multiple blades under different flight states; in order to offset the anti-torque caused by the rotation of the rotor and maintain the stability of the fuselage, the two adjacent rotors rotate in opposite directions. Whether it is the peak formed by the overall movement of the UAV or the spectrum broadening caused by the micro-motion of the rotor, the simulated echo is very close to the measured echo.

[0039] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings herein are incorporated into and constitute a part of the specification, illustrate embodiments consistent with the present invention, and together with the specification are used to explain the principles of the present invention. Obviously, the accompanying drawings described below are only some embodiments of the present invention, and for those of ordinary skill in the art, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0041] Figure 1 It is a flow chart of a pulse Doppler echo simulation method for a rotary-wing UAV according to an embodiment of the present invention;

[0042] Figure 2 The position relationship between the radar and the UAV in an embodiment of the present invention;

[0043] Figure 3 The position relationship between the radar and the rotor single scattering point in the embodiment of the present invention;

[0044] Figure 4 A single blade model according to an embodiment of the present invention;

[0045] Figure 5 This is the UAV echo simulation result of the embodiment of the present invention;

[0046] Figure 6 The measured results of the hovering echo of the UAV according to the embodiment of the present invention;

[0047] Figure 7 The actual measurement result of the UAV flight echo of the embodiment of the present invention;

[0048] Figure 8 This is the distance unit where the target is located in the MTD plane extracted in an embodiment of the present invention. DETAILED DESCRIPTION

[0049] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that the present invention will be more comprehensive and complete and fully convey the concepts of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0050] The echo model involved in the present invention is based on the following assumptions:

[0051] 1. The echo model is based on pulse Doppler (PD) radar;

[0052] 2. The range resolution of the radar is much greater than the size of the drone;

[0053] 3. The frequency resolution of the radar is much smaller than the linear speed of the rotor;

[0054] 4. The distance between the radar and the drone meets the far-field condition;

[0055] 5. The reception time of radar transmission signal is much longer than the transmission time;

[0056] 6. The echo model is interested in the echo phase rather than the echo amplitude, so the attenuation of the radar signal in space is ignored.

[0057] Based on the above assumptions, the echo model adopts the "stationary-motion" method, that is, when the scattering point reflects the signal, the distance from the radar is considered to remain unchanged; the echo model does not consider multipath, diffraction or structural reflection, and ignores the distance between the rotor center point and the fuselage; therefore, the reflection signal of the entire UAV is regarded as the vector superposition of the echo signals of all scattering points.

[0058] The relationship between radar and drone position is as follows Figure 2 As shown in the figure, right-handed coordinate systems are established at the radar and the drone. The radar coordinates are expressed as (x r ,y r ,z r ) indicates that the coordinate origin O r At the geometric center of the radar array, x r is the horizontal direction of the array, y r is the normal direction of the array. The coordinates of the drone are expressed as (x u ,y u ,z u ) indicates that the coordinate origin O u is the center of gravity of the fuselage, (x u ,y u ,z u ) direction and (x r ,y r ,z r ) in the same direction. u to r The initial distance is R0, O u In (x r ,y r ,z r ) The azimuth and elevation angles of the coordinate system are α and β respectively.

[0059] Assume that the radar transmission signal is a linear frequency modulation signal:

[0060]

[0061] Among them, t fIndicates fast time, which refers to the sampling data of the receiving time in a pulse repetition interval (PRI), T p Indicates signal time width, K = B / T p represents the slope of the linear frequency modulation, B represents the bandwidth of the transmitted signal, and f c Indicates the signal carrier frequency.

[0062] Assume that the drone is at x r The axis is flying at a constant speed v, then at a certain moment O u With O r The distance is:

[0063] R b =R0+vt s

[0064] Among them, t s represents the slow time, and its expression is t s =m·PRI, where m represents the mth PRI number in a coherent pulse integration (CPI).

[0065] The fuselage echo signal received by the radar is

[0066]

[0067] Where c is the speed of light, σ b Represents the amplitude of the echo signal, which is proportional to the RCS of the scattering point.

[0068] Here, the propagation attenuation of electromagnetic waves in space is ignored, so σ b It is equivalent to the RCS of the scattering point. This model assumes that the angle between the fuselage and the radar remains unchanged, so the RCS of the fuselage scattering point is considered unchanged.

[0069] Assume that the accumulated points of radar moving target detection (MTD) are m max , the slow time sampling rate is the pulse repetition frequency (PRF), and the spectrum after slow time FFT is distributed at (-PRF / 2, +PRF / 2), where the relationship between speed and frequency is PRF / 2 = 2v / λ, then the maximum unambiguous speed (positive and negative unambiguous) is v max =PRF·λ / 4, the velocity resolution is Here, λ=c / f represents the carrier wavelength.

[0070] The relationship between the rotor linear velocity v and the angular velocity ω is v = ω·d, where d is the distance from the scattering point to the rotation center. When the blade is equivalent to a series of scattering points, the maximum spacing between each scattering point is The number of scattering points of a single leaf is Where L represents the total length of the blade, and the distance from each scattering point to the rotation center is expressed as d i =i·l.

[0071] To simplify the analysis, we first consider a model with only a single rotor scattering point P, α and β are set to 0, and the simplified model of the radar and the scattering point P is as follows: Figure 3 shown.

[0072] Figure 3 where θ represents the scattering point P and x u Angle between the axes, x t With y t Indicates that the scattering point P is at x u With y u The projected distance on the axis, ω represents the angular velocity of the rotor, d P Represents the distance from the scattering point P to the rotation center;

[0073] O u In (x r ,y r ,z r ) coordinate system is (R b ,0,0), the scattering point P is at (x r ,y r ,z r ) coordinate system is (d P cosθ t , d P sinθ t , 0), then point P is at (x r ,y r ,z r ) coordinate system is (R b +d P cosθ t , d P sinθ t , 0), at a certain moment, the scattering point P to O u The distance R P for

[0074]

[0075] Among them, θ t =θ0+ωt a , t a =t d +t s +t f , td is the time interval from the take-off time t0 to the start time of the simulated echo.

[0076] The radar echo signal of the rotor scattering point is

[0077]

[0078] Among them, σ P Equivalent to the RCS of the scattering point P, which varies with fast time.

[0079] Here σ P The optical projection method is used for calculation, and the rotor blade is simplified into a rectangular plate perpendicular to the radar line of sight, such as Figure 4 shown.

[0080] Figure 4 h represents the height of the rectangular blade. Since the model satisfies the far-field condition, n on the same blade s Scattering points and x r The angle is the same, so it is assumed that the σ of all scattering points of the same leaf P Same, σ P =hl|sinθ t |.

[0081] Then, the radar echo signal of a single blade can be expressed as

[0082] For n j For a rotor with 10 blades, considering that the initial phase of each blade is different, the radar echo signal of a single rotor is

[0083] Consider n k The rotors have different angular velocities ω k and the initial phase θ k , then the radar echo signals of all rotors are Among them, θ t =θ k +(j-1)2π / n j +ω k t a .

[0084] The radar echo signal of the entire rotor UAV is s(t s ,t a )=s b (t s )+s total (t a )+s n , where s n Indicates the noise in the echo signal.

[0085] In order to illustrate the simulation effect of the present invention, three scenarios of hovering, slow flight and fast flight are designed. The following table gives detailed simulation experiment parameters.

[0086]

[0087] In order to offset the anti-torque caused by the rotation of the rotors and maintain the stability of the fuselage, the two adjacent rotors rotate in opposite directions, and the flight speed of the drone does not exceed the radar fuzzy speed;

[0088] The simulation results of the drone in hovering, slow flight and fast flight are as follows Figure 5 shown.

[0089] from Figure 5 As can be seen from (a, c, e), the simulated echo exhibits an obvious "flickering" effect in the time domain. Figure 5 It can be seen from (b, d, f) that the simulated echo forms a peak on the MTD plane. The micro-motion of the rotor causes the target peak to widen on both sides of the Doppler dimension, and the degree of widening increases with the increase of the rotor speed. When the UAV is hovering, the echo peak falls on the clutter channel.

[0090] Figure 6 and Figure 7 The results of pulse compression and MTD processing of the echoes of the hovering and fast-flying states of the rotorcraft UAV measured by radar on a ground armored platform are given respectively;

[0091] from Figure 6 and Figure 7 It can be seen that the measured echo forms a peak on the MTD plane, and the peak has a spectrum broadening on both sides of the Doppler dimension;

[0092] When the drone is hovering, the echo peak falls on the clutter channel. In addition, the measured echo also contains ground clutter and cloud and rain clutter;

[0093] In order to further verify the effectiveness of the proposed pulse Doppler echo simulation method for rotary-wing UAVs, all Doppler channels of the distance unit where the target is located in the MTD plane are extracted for analysis, such as Figure 8 shown.

[0094] from Figure 8 It can be seen that the simulated echo and the measured echo show similar spectrum distribution on the MTD plane;

[0095] Whether it is the peak formed by the overall movement of the drone or the spectrum broadening caused by the micro-motion of the rotor, the simulated echo is very close to the measured echo.

[0096] It should be noted that, as another aspect, the present application also provides a storage medium, which can be included in an electronic device; or it can exist independently without being installed in the electronic device. The above storage medium carries one or more programs, and when the above one or more programs are executed by an electronic device, the electronic device implements the method described in the following embodiments. For example, the electronic device can implement the following Figure 1 The individual steps of the method are shown.

[0097] In one embodiment, the present application provides a computer program product, including a computer program, which implements the steps in the above-mentioned method embodiments when executed by a processor.

[0098] In addition, the above-mentioned figures are only schematic illustrations of the processes included in the method according to an exemplary embodiment of the present invention, and are not intended to be limiting. It is easy to understand that the processes shown in the above-mentioned figures do not indicate or limit the time sequence of these processes. In addition, it is also easy to understand that these processes can be performed synchronously or asynchronously, for example, in multiple modules.

[0099] Other embodiments of the invention will readily occur to those skilled in the art after considering the specification and practicing the invention herein. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the claims.

[0100] It should be understood that the present invention is not limited to the exact construction that has been described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A pulse Doppler echo simulation method for a rotary wing UAV, characterized in that: The method comprises: The fuselage is equivalent to an isotropic scattering point, and the radar echo signal of the fuselage is simulated based on the RCS of the fuselage scattering point and the distance between the radar and the center of gravity of the fuselage; The rotor blades are equivalent to a set of uniformly distributed isotropic scattering points on a straight line, and the radar echo signals of the rotor scattering points are simulated based on the RCS of the rotor scattering points and the distance from the rotor scattering points to the center of gravity of the fuselage; The radar echo signal based on the rotor scattering point simulates the radar echo signal of a single blade, the radar echo signal based on the radar echo signal of a single blade simulates the radar echo signal of a single rotor, and the radar echo signal based on a single rotor simulates the radar echo signals of all rotors; The pulse Doppler echo signal of the rotor UAV is simulated based on the radar echo signals of all rotors, the radar echo signal of the fuselage and the echo signal noise.

2. The pulse Doppler echo simulation method for a rotary wing UAV according to claim 1, characterized in that: The two adjacent rotors of the rotor UAV rotate in opposite directions.

3. The pulse Doppler echo simulation method for a rotary wing UAV according to claim 1, characterized in that: The radar echo signal of the fuselage is simulated based on the RCS of the fuselage scattering point and the distance between the radar and the center of gravity of the fuselage. The formula used is as follows: Among them, σ b is the RCS of the fuselage scattering point, c is the speed of light, t f Indicates fast time, f c Indicates the signal carrier frequency, R b Indicates the distance between the radar and the center of gravity of the fuselage.

4. The pulse Doppler echo simulation method for a rotary wing UAV according to claim 1, characterized in that: The radar echo signal of the rotor scattering point is simulated based on the RCS of the rotor scattering point and the distance from the rotor scattering point to the center of gravity of the fuselage, and the formula used is as follows: Among them, σ P is the RCS of the rotor scattering point, R P is the distance from the rotor scattering point to the center of gravity of the fuselage.

5. The pulse Doppler echo simulation method for a rotary wing UAV according to claim 4, characterized in that: The radar echo signal based on the rotor scattering point simulates the radar echo signal of a single blade, and the formula used is as follows: Among them, n s is the number of rotor scattering points for a single blade.

6. The pulse Doppler echo simulation method for a rotary wing UAV according to claim 5, characterized in that: The radar echo signal based on a single blade simulates the radar echo signal of a single rotor, and the formula used is as follows: Among them, n j is the number of blades of a single rotor.

7. The pulse Doppler echo simulation method for a rotary wing UAV according to claim 6, characterized in that: The radar echo signal based on a single rotor is used to simulate the radar echo signals of all rotors, and the formula used is as follows: Among them, n k is the number of rotors with different angular velocities and initial phases.

8. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the pulse Doppler echo simulation method for a rotary-wing UAV as described in any one of claims 1 to 7 is implemented.

9. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the pulse Doppler echo simulation method for the rotary-wing UAV according to any one of claims 1 to 7 is implemented.

10. An electronic device, characterized in that: include: processor; as well as A memory, configured to store executable instructions of the processor; Wherein, the processor is configured to execute the pulse Doppler echo simulation method for a rotary-wing UAV according to any one of claims 1 to 7 by executing the executable instructions.

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