Helicopter radar echo signal calculation method and device

Abstract

The invention discloses a helicopter radar echo signal calculation method and device. The method comprises the steps of correcting radar echoes of each rotor wing of the helicopter in a static state based on observation parameters of a radar and structural parameters and flight parameters of the helicopter, and obtaining an initial echo signal, containing micro-vibration information, of each rotor wing; the observation parameters comprise an azimuth angle, a pitch angle and a frequency of a detection signal when the radar detects each rotor; the structural parameters comprise the number of blades of the rotor wing and the size of each blade; the flight parameters comprise flight speed and direction; based on the variable pitch angle of the helicopter blade, correcting the initial echo signal of each rotor to obtain a final echo signal of each rotor; calculating a fuselage echo signal of the helicopter; and superposing the final echo signal of each rotor and the echo signal of the helicopter body to obtain a radar echo signal of the whole helicopter. According to the invention, the calculated echo signal is more real.

Description

Technical Field

[0001] The invention relates to the field of radar detection technology, and in particular to a method and device for calculating a helicopter radar echo signal. Background Art

[0002] During the flight of a helicopter, on the one hand, micro-vibration will be generated due to the rotation of the rotor, and on the other hand, pitch change will occur. Both micro-vibration and pitch change will be reflected in the radar echo signal. However, when the relevant technology uses microwave darkroom measurement or electromagnetic modeling simulation to calculate the helicopter target, it usually only considers the impact of the helicopter's micro-vibration on the echo, and does not consider the impact of pitch change and the fuselage on the echo. Therefore, the existing method cannot accurately obtain the real echo signal of the helicopter, which is not conducive to the analysis of the helicopter's movement form and structural information.

[0003] Based on this, there is an urgent need for a method and device for calculating helicopter radar echo signals to solve the above problems. Summary of the invention

[0004] The present invention provides a method and device for calculating a helicopter radar echo signal, and the calculated echo signal is more realistic. The technical solution is as follows:

[0005] In a first aspect, a method for calculating a helicopter radar echo signal is provided, the method comprising:

[0006] Based on the radar observation parameters, the helicopter's structural parameters and flight parameters, the radar echo of each rotor of the helicopter in a stationary state is corrected to obtain an initial echo signal of each rotor containing micro-vibration information; the observation parameters include the azimuth angle, pitch angle and frequency of the detection signal when the radar detects each rotor; the structural parameters include the number of rotor blades and the size of each blade; the flight parameters include flight speed and direction;

[0007] Based on the variable pitch angle of the helicopter blades, the initial echo signal of each rotor is corrected to obtain the final echo signal of each rotor;

[0008] Calculate the helicopter's fuselage echo signal;

[0009] The final echo signal of each rotor and the fuselage echo signal are superimposed to obtain the radar echo signal of the entire helicopter.

[0010] In a second aspect, a device for calculating a helicopter radar echo signal is provided, the device comprising:

[0011] A first calculation unit is used to correct the radar echo of each rotor of the helicopter in a stationary state based on the observation parameters of the radar, the structural parameters of the helicopter and the flight parameters, so as to obtain an initial echo signal of each rotor containing micro-vibration information; the observation parameters include the azimuth angle, the pitch angle and the frequency of the detection signal when the radar detects each rotor; the structural parameters include the number of rotor blades and the size of each blade; the flight parameters include the flight speed and direction;

[0012] The second calculation unit is used to correct the initial echo signal of each rotor based on the pitch angle of the helicopter blade to obtain the final echo signal of each rotor;

[0013] A third calculation unit, used for calculating the fuselage echo signal of the helicopter;

[0014] The fourth calculation unit is used to superimpose the final echo signal of each rotor and the fuselage echo signal to obtain the radar echo signal of the entire helicopter.

[0015] In a third aspect, an embodiment of the present invention further provides an electronic device, including a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the method described in any embodiment of this specification is implemented.

[0016] In a fourth aspect, a computer-readable storage medium is provided, wherein the storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the above-mentioned method for calculating the helicopter radar echo signal are implemented.

[0017] In a fifth aspect, a computer program product is provided, comprising a computer program, which, when executed by a processor, implements the steps of the above-mentioned method for calculating the helicopter radar echo signal.

[0018] The embodiment of the present invention provides a method for calculating the radar echo signal of a helicopter. The micro-Doppler characteristics of a helicopter are closely related to the structure and flight parameters of the target rotating blades, the observation parameters of the radar, etc. Based on the above-mentioned influencing factors, the present application derives a theoretical formula for the micro-Doppler characteristics caused by the rotating blades of the rotor on the basis of the radar echo in the static state of the rotor, and obtains the initial echo signal of the rotor containing micro-vibration information. In addition, since the blades of the helicopter will have a pitch angle in dynamic flight, and the pitch angle will change with the flight attitude, the final echo signal of the rotor modulated by the pitch angle is further calculated. Finally, the sum of the echo signal of the fuselage and the echo signal of the rotor is taken as the radar echo signal of the entire helicopter. It can be seen that the echo signal calculated by the present application not only includes the micro-vibration characteristics of the rotor, but also includes the influence of the blade pitch angle. The calculated echo signal is closer to the actual situation, which is conducive to analyzing the movement form and structural information of the helicopter. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 It is a flow chart of a method for calculating a helicopter radar echo signal provided by one embodiment of the present invention;

[0021] Figure 2 It is a structural diagram of a computing device for helicopter radar echo signals provided by one embodiment of the present invention;

[0022] Figure 3 is a hardware architecture diagram of a computer device provided by an embodiment of the present invention;

[0023] Figure 4 is a schematic diagram of the geometric relationship between a radar and a helicopter rotor provided by an embodiment of the present invention;

[0024] Figure 5 is a schematic diagram of the geometric relationship between a radar and a rotor blade provided by an embodiment of the present invention;

[0025] Figure 6 is a schematic diagram of a blade without pitch change provided by an embodiment of the present invention;

[0026] Figure 7 is a schematic diagram of a blade after pitch change provided by an embodiment of the present invention;

[0027] Figure 8 is a helicopter echogram provided by an embodiment of the present invention;

[0028] Fig. 9 is a helicopter echo spectrum diagram provided by an embodiment of the present invention;

[0029] Fig.10 This is a time-frequency diagram of a helicopter echo provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0031] The specific implementation of the above concept is described below.

[0032] Please refer to Figure 1 , an embodiment of the present invention provides a method for calculating a helicopter radar echo signal, the method comprising:

[0033] Step 100, based on the radar observation parameters, the structural parameters and flight parameters of the helicopter, the radar echo of each rotor of the helicopter in a stationary state is corrected to obtain an initial echo signal of each rotor containing micro-vibration information; the observation parameters include the azimuth angle, pitch angle and frequency of the detection signal when the radar detects each rotor; the structural parameters include the number of rotor blades and the size of each blade; the flight parameters include the flight speed and direction;

[0034] Step 102, based on the pitch angle of the helicopter blades, correct the initial echo signal of each rotor to obtain the final echo signal of each rotor;

[0035] Step 104, calculating the fuselage echo signal of the helicopter;

[0036] Step 106, superimpose the final echo signal of each rotor and the fuselage echo signal to obtain the radar echo signal of the entire helicopter.

[0037] In this embodiment, the micro-Doppler characteristics of the helicopter are closely related to the structure and flight parameters of the target rotating blades, the observation parameters of the radar, etc. Starting from the above-mentioned influencing factors, the present application derives a theoretical formula for the micro-Doppler characteristics caused by the rotating blades of the rotor on the basis of the radar echo in the static state of the rotor, and obtains the initial echo signal of the rotor containing micro-vibration information. In addition, since the blades of the helicopter will have a pitch angle in dynamic flight, and the pitch angle will change with the flight attitude, the final echo signal of the rotor modulated by the pitch angle is further calculated. Finally, the sum of the echo signal of the fuselage and the echo signal of the rotor is used as the radar echo signal of the entire helicopter. It can be seen that the echo signal calculated by the present application not only includes the micro-vibration characteristics of the rotor, but also includes the influence of the blade pitch angle. The calculated echo signal is closer to the actual situation, which is conducive to analyzing the movement form and structural information of the helicopter.

[0038] Described below Figure 1 How the various steps are performed.

[0039] First, for step 100, assume that the radar transmission signal x(t) is:

[0040] x(t)=exp(jω0t)

[0041] When the scattering characteristics of a helicopter are in the optical region, since the rotor blades are usually made of metal or composite materials, strong radar reflection will be generated. The linear superposition of q scattering centers constitutes the radar echo of the target, and each scattering center can be regarded as a point with a certain reflectivity. Therefore, the radar echo s(t) of a stationary target can be expressed as:

[0042]

[0043] In the above formula, σ n and φ n represents the amplitude and phase of the nth scattering center; r n (t) is the distance between the nth scattering center and the radar at time t, c is the speed of light, and ω0 is the frequency of the signal.

[0044] However, due to micro-vibrations and pitch changes in helicopters during flight, it is necessary to correct the radar echo of the target in a stationary state in order to obtain an echo signal that is more in line with the actual situation.

[0045] In some embodiments, based on the observation parameters of the radar, the structural parameters of the helicopter, and the flight parameters, the radar echo of each rotor of the helicopter in a stationary state is corrected to obtain an initial echo signal of each rotor containing micro-vibration information, including:

[0046] S1, establish the geometric relationship coordinate system between the radar and the rotor;

[0047] S2, in the geometric coordinate system, for each scattering point in each blade of the rotor, execute:

[0048] S3, assuming that the azimuth and pitch angles of the radar when detecting the scattering point are zero and the height of the scattering point in the rotor coordinate system is zero, calculate a first distance from the radar to the scattering point;

[0049] S4, calculating a first echo signal and a first phase function of the scattering point based on the first distance;

[0050] S5, correcting the first distance based on the true azimuth angle when the radar detects the scattering point to obtain a corrected first distance;

[0051] S6, based on the corrected first distance, the true azimuth and pitch angle when the radar detects the scattering point, and the true height of the scattering point in the rotor coordinate system, correct the first phase function to obtain a corrected first phase function;

[0052] S7, correcting the first echo signal based on the corrected first phase function to obtain a corrected first echo signal of the scattering point;

[0053] S8, calculating a baseband echo signal of the corrected first echo signal;

[0054] S9, integrating the baseband echo signal of each scattering point on each blade respectively to obtain a total baseband echo signal of each blade;

[0055] S10, summing up the total baseband echo signal of each blade to obtain the initial echo signal of the rotor.

[0056] The implementation process of steps S1 to S10 is described in detail below:

[0057] In step S1, the geometric relationship coordinate system includes the first coordinate system of the radar, the second coordinate system of the rotor and the reference coordinate system; the origin of the first coordinate system is the signal transmitting end of the radar, the origin of the second coordinate system is the rotation center of the rotor, the origin of the reference coordinate system coincides with the origin of the second coordinate system, and the reference coordinate system is parallel to the first coordinate system.

[0058] like Figure 4 As shown, the radar is located at the origin of the first coordinate system (X, Y, Z), the center of the rotor is located at the origin of the second coordinate system of the object, its rotation axis is the z axis, the rotation angular rate is Ω, and the rotation plane is the plane (x, y, z = 0). The reference coordinate system is (X', Y', Z') and is parallel to the fixed coordinate system in space. The distance between the radar and the origin of the reference coordinate system is R0, and the azimuth and pitch angles of the rotor observed by the radar are α and β respectively.

[0059] Assume α=β=0°, such as Figure 5 If the scattering point P at (x0, y0, z0 = 0) rotates around the z-axis in the object's second coordinate system at a constant angular velocity Ω, the distance from the scattering point P to the origin of the object's second coordinate system is The effective length of the blade is L = L2-L1, L1 is the distance from the root of the blade to the center of rotation, and L2 is the distance from the tip of the blade to the center of rotation. If the initial rotation angle of point P at t = 0 is Then at time t, point P rotates to (x t ,y t ,z t =0), the rotation angle becomes The distance between the rotor's rotation center and the radar is R t =R0+vt, v is the radial velocity of the aircraft, so the first distance from the radar to the scattering point P is:

[0060]

[0061] Since in the far field, (l p / R t ) 2 →0. Therefore, the first echo signal of the scattering point P received by the radar is:

[0062]

[0063] In the formula, Φ P (t)=4πR P (t) / λ is the first phase function.

[0064] In actual flight of a helicopter, the azimuth angle α, the pitch angle β and the height z0 of the rotor blade are not necessarily zero, so the first distance, the first echo signal and the first phase function need to be corrected.

[0065] Corrected first distance R P '(t) is:

[0066]

[0067] The modified first phase function Φ P '(t) is:

[0068]

[0069] The corrected first echo signal is:

[0070]

[0071] Since the helicopter is a moving target, after obtaining the first echo signal, its baseband echo signal must be calculated. B=(4π / λ)l P cosβ, the corrected first echo signal can be represented by a first-order Bessel function. Since the spectrum of the scattering point on the blade is composed of a center frequency f0-f d The interval between adjacent spectral lines is Ω / (2π) and the spectral line pairs are composed. Therefore, the baseband echo signal s of the corrected first echo signal can be calculated by the following formula: B (t):

[0072]

[0073] Integrate the above formula over the effective length L of the blade to obtain the total baseband signal s of each blade L (t):

[0074]

[0075] There are N blades on each rotor, each blade is evenly distributed and installed on the rotating shaft of the rotor, and the structure of each blade is exactly the same. The N blades of the rotor have different initial rotation angles. Assume that the initial rotation angle of the first blade is The rotation angle of the kth blade is Then the following relationship exists:

[0076]

[0077] Therefore, the echo signal s of the entire rotor can be derived from the total baseband signal of each blade Σ (t):

[0078]

[0079] In the above formula, R t is the distance between the rotor's rotation center and the radar, R t =R0+vt;l P is the distance from the scattering point P to the origin of the second coordinate system of the rotor, x0 and y0 are the coordinates of the scattering point P in the x-direction and y-direction in the second coordinate system respectively; R0 is the distance between the radar and the origin of the reference coordinate system; v is the radial velocity of the helicopter; t represents the time; is the initial rotation angle of the scattered point P; Ω is the rotation angular velocity of the scattered point P around the z-axis in the second coordinate system; is the rotation angle of the scatter point P at time t; f0 is the center frequency; α is the azimuth angle of the radar; β is the pitch angle of the radar; z0 is the z-direction coordinate of the scatter point P in the second coordinate system; f d is the Doppler frequency shift caused by the radial motion of the aircraft, f d =2v / λ; λ is the wavelength; L1 is the distance from the root of the blade to the center of rotation; L2 is the distance from the tip of the blade to the center of rotation; the sum of L1 and L2 is the length of the blade L; k represents the kth blade, k = 0, 1, 2, ..., N-1; N is the total number of blades in the rotor; Φ k (t) is the phase function of the kth blade; is the baseband echo signal of the kth blade.

[0080] For step 102, the pitch angle of the helicopter blades in flight is as follows: Figure 6 and Figure 7 As shown, Figure 5 6 is a schematic diagram of pitch change, and φ is a schematic diagram of pitch change. The rotor radar echo signal modulated by the blade pitch angle is shown in the following formula:

[0081]

[0082] Wherein, φ is the pitch angle of the blade; A1 and A2 are intermediate parameters, A1 = sin(β+φ)+sin(β-φ), A2 = sign(β)[sin(β+φ)-sin(β-φ)], sign(·) is a function, when β≥0, sign(β) = 1; when β<0, sign(β) = -1.

[0083] It can be seen from the above formula that the radar echo of the blade is periodically modulated by the blade pitch angle, and the degree of modulation is related to the blade pitch angle φ.

[0084] For step 104, the fuselage echo can be expressed as:

[0085]

[0086] Where v is the radial velocity of the helicopter, σ(t) is the echo intensity at different times, and R0′ is the initial distance between the helicopter and the radar.

[0087] Finally, for step 106, generally, a helicopter has two rotating parts: the main rotor and the tail. The main rotor has a large RCS and a low rotation speed, while the tail has a small RCS and a high rotation speed. The radar echo of a helicopter is a superposition of the echoes of the main rotor, the tail, and the fuselage. The calculation formula is as follows:

[0088] S Helicopter (t) = s blade(main) (t)+s blade(tail) (t)+s body (t)

[0089] In the formula, s blade(main) (t) is the final echo signal of the main rotor; s blade(tail) (t) is the final echo signal of the tail wing.

[0090] It should be noted that, in actual work, it is determined according to the specific number of rotors.

[0091] In order to prove the effect of the method of the present application, the inventor used the method of the present application to verify a helicopter: the overall echo of the helicopter is as follows: Figure 8 As shown, the overall echo spectrum of the helicopter is as follows Fig. 9 As shown in the time-frequency diagram Fig.10 As shown. Figure 8 to Figure 10 It can be seen that the method of the present application can accurately calculate the echo signal of the helicopter during flight, which is consistent with the actual situation.

[0092] like Figure 2 , Figure 3 As shown, an embodiment of the present invention provides a device for calculating a helicopter radar echo signal. The device embodiment can be implemented by software, or by hardware or a combination of software and hardware. From the hardware level, Figure 2 FIG. 1 is a hardware architecture diagram of a computing device where a computing device for computing a helicopter radar echo signal provided by an embodiment of the present invention is located. Figure 2In addition to the processor, memory, network interface, and non-volatile memory shown in the figure, the computing device in which the device is located in the embodiment may also generally include other hardware, such as a forwarding chip responsible for processing messages, etc. Taking software implementation as an example, Figure 3 As shown, as a device in a logical sense, the CPU of the computing device in which it is located reads the corresponding computer program in the non-volatile memory into the internal memory and runs it.

[0093] Please refer to Figure 3 The embodiment of the present invention provides a device for calculating a helicopter radar echo signal, the device comprising:

[0094] The first calculation unit 300 is used to correct the radar echo of each rotor of the helicopter in a stationary state based on the observation parameters of the radar, the structural parameters of the helicopter and the flight parameters, so as to obtain an initial echo signal of each rotor containing micro-vibration information; the observation parameters include the azimuth angle, the pitch angle and the frequency of the detection signal when the radar detects each rotor; the structural parameters include the number of rotor blades and the size of each blade; the flight parameters include the flight speed and direction;

[0095] The second calculation unit 302 is used to correct the initial echo signal of each rotor based on the pitch angle of the helicopter blades to obtain the final echo signal of each rotor;

[0096] The third calculation unit 304 is used to calculate the fuselage echo signal of the helicopter;

[0097] The fourth calculation unit 306 is used to superimpose the final echo signal of each rotor and the fuselage echo signal to obtain the radar echo signal of the entire helicopter.

[0098] In some implementations, the first computing unit 300 is configured to perform the following operations:

[0099] Establishing a geometric relationship coordinate system between the radar and the rotor;

[0100] In the geometric relation coordinate system, for each scattering point in each blade of the rotor, the following operations are performed:

[0101] Assuming that the azimuth and pitch angles of the radar when detecting the scattering point are zero and the height of the scattering point in the rotor coordinate system is zero, calculate the first distance from the radar to the scattering point;

[0102] Based on the first distance, calculating a first echo signal and a first phase function of the scattering point;

[0103] Correcting the first distance based on the true azimuth angle when the radar detects the scattering point to obtain a corrected first distance;

[0104] Based on the corrected first distance, the true azimuth and pitch angle when the radar detects the scattering point, and the true height of the scattering point in the rotor coordinate system, the first phase function is corrected to obtain a corrected first phase function;

[0105] Correcting the first echo signal based on the corrected first phase function to obtain a corrected first echo signal of the scattering point;

[0106] Calculating a baseband echo signal of the corrected first echo signal;

[0107] Integrate the baseband echo signal of each scattering point on each blade to obtain the total baseband echo signal of each blade;

[0108] The total baseband echo signal of each blade is summed to obtain the initial echo signal of the rotor.

[0109] In some embodiments, the geometric relationship coordinate system includes a first coordinate system of the radar, a second coordinate system of the rotor, and a reference coordinate system; the origin of the first coordinate system is the signal transmitting end of the radar, the origin of the second coordinate system is the rotation center of the rotor, the origin of the reference coordinate system coincides with the origin of the second coordinate system, and the reference coordinate system is parallel to the first coordinate system.

[0110] In some embodiments, the radar is at a first distance R from the scattering point p. P (t) is:

[0111]

[0112] The first echo signal s of the scattering point p R (t) is:

[0113]

[0114] The first phase function Φ P The expression of (t) is:

[0115] Φ P (t)=4πR P (t) / λ

[0116] Corrected first distance R P '(t) is:

[0117]

[0118] The modified first phase function Φ P '(t) is:

[0119]

[0120] The corrected first echo signal is:

[0121]

[0122] The baseband echo signal s of the corrected first echo signal B (t) is:

[0123]

[0124] The total baseband echo signal of each blade is s L (t) is:

[0125]

[0126] The initial echo signal of the rotor s Σ (t) is:

[0127]

[0128] In the formula, R t is the distance between the rotor's rotation center and the radar, R t =R0+vt;l P is the distance from the scattering point P to the origin of the second coordinate system of the rotor, x0 and y0 are the coordinates of the scattering point P in the x-direction and y-direction in the second coordinate system respectively; R0 is the distance between the radar and the origin of the reference coordinate system; v is the radial velocity of the helicopter; t represents the time; is the initial rotation angle of the scattered point P; Ω is the rotation angular velocity of the scattered point P around the z-axis in the second coordinate system; is the rotation angle of the scatter point P at time t; f0 is the center frequency; α is the azimuth angle of the radar; β is the pitch angle of the radar; z0 is the z-direction coordinate of the scatter point P in the second coordinate system; f d is the Doppler frequency shift caused by the radial motion of the aircraft, f d =2v / λ; λ is the wavelength; L1 is the distance from the root of the blade to the center of rotation; L2 is the distance from the tip of the blade to the center of rotation; the sum of L1 and L2 is the length of the blade L; k represents the kth blade, k = 0, 1, 2, ..., N-1; N is the total number of blades in the rotor; Φ k (t) is the phase function of the kth blade; is the baseband echo signal of the kth blade.

[0129] In some embodiments, the final echo signal s of each rotor blade (t) is:

[0130]

[0131] Wherein, φ is the pitch angle of the blade; A1 and A2 are intermediate parameters, A1 = sin(|β|+φ)+sin(|β|-φ), A2 = sign(β)[sin(|β|+φ)-sin(|β|-φ)], sign(·) is a function, when β≥0, sign(β) = 1; when β<0, sign(β) = -1.

[0132] In some embodiments, the helicopter fuselage echo signal s body (t) is calculated by the following formula:

[0133]

[0134] Where v is the radial velocity of the helicopter, σ(t) is the echo intensity at different times, and R0′ is the initial distance between the helicopter and the radar.

[0135] In some embodiments, the helicopter includes a main rotor and a tail wing, and the radar echo signal S of the entire helicopter is Helicopter (t) is calculated by the following formula:

[0136] S Helicopter (t) = s blade(main) (t)+s blade(tail) (t)+s body (t)

[0137] In the formula, s blade(main) (t) is the final echo signal of the main rotor; s blade(tail) (t) is the final echo signal of the tail wing.

[0138] It should be noted that the helicopter radar echo signal calculation device provided in the above embodiment is only illustrated by the division of the above functional modules. In actual application, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device is divided into different functional modules to complete all or part of the functions described above. In addition, the helicopter radar echo signal calculation device provided in the above embodiment and the helicopter radar echo signal calculation method embodiment belong to the same concept. The specific implementation process is detailed in the method embodiment and will not be repeated here.

[0139] The embodiment of the present application also provides a computer device, please refer to Figure 3 The computer device includes a processor and a memory, in which at least one instruction, at least one program, a code set or an instruction set is stored, and the at least one instruction, at least one program, a code set or an instruction set is loaded and executed by the processor to implement the calculation method of the helicopter radar echo signal provided by the above-mentioned method embodiments.

[0140] An embodiment of the present application also provides a computer-readable storage medium, on which is stored at least one instruction, at least one program, code set or instruction set, and the at least one instruction, at least one program, code set or instruction set is loaded and executed by a processor to implement the calculation method of the helicopter radar echo signal provided by the above-mentioned method embodiments.

[0141] An embodiment of the present application also provides a computer program product, which includes a computer program. A processor of a computer device reads the computer program from a computer-readable storage medium, and the processor executes the computer program, so that the computer device executes the method for calculating the helicopter radar echo signal described in any of the above embodiments.

[0142] For the convenience of description, the above system or device is described by dividing it into various modules or units according to its functions. Of course, when implementing the present application, the functions of each unit can be implemented in the same or multiple software and / or hardware.

[0143] It can be known from the description of the above implementation methods that those skilled in the art can clearly understand that the present application can be implemented by means of software plus a necessary general hardware platform. Based on such an understanding, the technical solution of the present application can be essentially or partly contributed to the prior art in the form of a software product, which can be stored in a storage medium such as ROM / RAM, a magnetic disk, an optical disk, etc., and includes several instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in the various embodiments of the present application or certain parts of the embodiments.

[0144] Finally, it should be noted that, in this article, relational terms such as first, second, third and fourth are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0145] The above is only a preferred implementation of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A method for calculating a helicopter radar echo signal, characterized in that: The method comprises: Based on the radar observation parameters, the helicopter's structural parameters and flight parameters, the radar echo of each rotor of the helicopter in a stationary state is corrected to obtain an initial echo signal of each rotor containing micro-vibration information; the observation parameters include the azimuth angle, pitch angle and frequency of the detection signal when the radar detects each rotor; the structural parameters include the number of rotor blades and the size of each blade; the flight parameters include flight speed and direction; Based on the variable pitch angle of the helicopter blades, the initial echo signal of each rotor is corrected to obtain the final echo signal of each rotor; Calculate the helicopter's fuselage echo signal; The final echo signal of each rotor and the fuselage echo signal are superimposed to obtain the radar echo signal of the entire helicopter.

2. The method according to claim 1, characterized in that The method corrects the radar echo of each rotor of the helicopter in a stationary state based on the observation parameters of the radar, the structural parameters of the helicopter and the flight parameters to obtain the initial echo signal of each rotor containing micro-vibration information, including: Establishing a geometric relationship coordinate system between the radar and the rotor; In the geometric relation coordinate system, for each scattering point in each blade of the rotor, the following is performed: Assuming that the azimuth and pitch angles of the radar when detecting the scattering point are zero and the height of the scattering point in the rotor coordinate system is zero, calculate the first distance from the radar to the scattering point; Based on the first distance, calculating a first echo signal and a first phase function of the scattering point; Correcting the first distance based on the true azimuth angle when the radar detects the scattering point to obtain a corrected first distance; Based on the corrected first distance, the true azimuth and pitch angle when the radar detects the scattering point, and the true height of the scattering point in the rotor coordinate system, the first phase function is corrected to obtain a corrected first phase function; Correcting the first echo signal based on the corrected first phase function to obtain a corrected first echo signal of the scattering point; Calculating a baseband echo signal of the corrected first echo signal; Integrate the baseband echo signal of each scattering point on each blade to obtain the total baseband echo signal of each blade; The total baseband echo signal of each blade is summed to obtain the initial echo signal of the rotor.

3. The method according to claim 2, characterized in that The geometric relationship coordinate system includes a first coordinate system of the radar, a second coordinate system of the rotor and a reference coordinate system; the origin of the first coordinate system is the signal transmitting end of the radar, the origin of the second coordinate system is the rotation center of the rotor, the origin of the reference coordinate system coincides with the origin of the second coordinate system, and the reference coordinate system is parallel to the first coordinate system.

4. The method according to claim 3, characterized in that The first distance R from the radar to the scattering point p P (t) is: The first echo signal s of the scattering point p R (t) is: The first phase function Φ P The expression of (t) is: F P (t)=4πR P (t) / min Corrected first distance R P '(t) is: The corrected first phase function Φ P '(t) is: The corrected first echo signal is: The baseband echo signal s of the corrected first echo signal B (t) is: The total baseband echo signal s of each blade L (t) is: The initial echo signal of the rotor s Σ (t) is: In the formula, R t is the distance between the rotor's rotation center and the radar, R t =R0+vt;l P is the distance from the scattering point P to the origin of the second coordinate system of the rotor, x0 and y0 are the coordinates of the scattering point P in the x-direction and y-direction in the second coordinate system respectively; R0 is the distance between the radar and the origin of the reference coordinate system; v is the radial velocity of the helicopter; t represents the time; is the initial rotation angle of the scattered point P; Ω is the angular velocity of the scattered point P around the z-axis in the second coordinate system; is the rotation angle of the scatter point P at time t; f0 is the center frequency; α is the azimuth angle of the radar; β is the pitch angle of the radar; z0 is the z-direction coordinate of the scatter point P in the second coordinate system; f d is the Doppler frequency shift caused by the radial motion of the aircraft, f d =2v / λ; λ is the wavelength; L1 is the distance from the root of the blade to the center of rotation; L2 is the distance from the tip of the blade to the center of rotation; is the total length of the blade, L=L1+L2; k represents the kth blade, k=0,1,2,…,N-1; N is the total number of blades in the rotor; Φ k (t) is the phase function of the kth blade; is the baseband echo signal of the kth blade.

5. The method according to claim 4, characterized in that The final echo signal s of each rotor blade (t) is: Wherein, φ is the pitch angle of the blade; A1 and A2 are intermediate parameters, A1 = sin(|β|+φ)+sin(|β|-φ), A2 = sign(β)[sin(|β|+φ)-sin(|β|-φ)], sign(·) is a function, when β≥0, sign(β) = 1; when β<0, sign(β) = -1.

6. The method according to claim 5, characterized in that Helicopter fuselage echo signal body (t) is calculated by the following formula: Where v is the radial velocity of the helicopter, σ(t) is the echo intensity at different times, and R0′ is the initial distance between the helicopter and the radar.

7. The method according to claim 6, characterized in that The helicopter includes a main rotor and a tail wing. The radar echo signal S of the entire helicopter Helicopter (t) is calculated by the following formula: S Helicopter (t)=s blade(main) (t)+s blade(tail) (t)+s body (t) In the formula, s blade(main) (t) is the final echo signal of the main rotor; s blade(tail) (t) is the final echo signal of the tail wing.

8. A device for calculating helicopter radar echo signals, characterized in that: The device comprises: A first calculation unit is used to correct the radar echo of each rotor of the helicopter in a stationary state based on the observation parameters of the radar, the structural parameters of the helicopter and the flight parameters, so as to obtain an initial echo signal of each rotor containing micro-vibration information; the observation parameters include the azimuth angle, the pitch angle and the frequency of the detection signal when the radar detects each rotor; the structural parameters include the number of rotor blades and the size of each blade; the flight parameters include the flight speed and direction; The second calculation unit is used to correct the initial echo signal of each rotor based on the pitch angle of the helicopter blade to obtain the final echo signal of each rotor; A third calculation unit, used for calculating the fuselage echo signal of the helicopter; The fourth calculation unit is used to superimpose the final echo signal of each rotor and the fuselage echo signal to obtain the radar echo signal of the entire helicopter.

9. A computer device, characterized in that: The computer device includes a memory and a processor, the memory is used to store a computer program, and the processor is used to execute the computer program stored in the memory to implement the steps of any one of the methods described in claims 1-7.

10. A computer-readable storage medium, characterized in that: The storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the method described in any one of claims 1 to 7 are implemented.

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