System and method for testing ship RCS in open sea

Abstract

The invention discloses a system and method for testing the RCS of a ship in an open sea. The device comprises a mooring unmanned aerial vehicle, a bearing platform, a tested ship and a control station, the mooring unmanned aerial vehicle is connected with the bearing platform through an active cable, stable transmission of electric power and signals is achieved, and the requirement for long endurance of open seas is met. The control station is provided with a dynamic tracking module, the radar direction is adjusted through video tracking or satellite positioning guidance, and continuous alignment of the moving ship is ensured; and the calibration reflector is used for field calibration in the open sea. The testing method comprises the steps of distance range determination, open sea area screening, dynamic tracking testing, field calibration and RCS calculation, the problem that an existing offshore / shore-based test cannot simulate the real environment of the open sea is solved, the testing result has practical significance, and the requirements of ship stealth design, weapon equipment demonstration and the like can be met.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of radar testing, in particular, to a system and method for testing the RCS of a ship at sea. BACKGROUND

[0002] The radar cross section (RCS) of a ship is an important indicator of its radar detectability and is an important basis for evaluating the survivability and combat effectiveness of the ship. In modern warfare, the widespread use of radar-guided weapons and surveillance systems makes it necessary to accurately grasp and effectively control the RCS of a ship in order to improve combat effectiveness.

[0003] Currently, the traditional methods for testing the RCS of a ship mainly include using a scaled model for testing in a microwave anechoic chamber or an open test field and using shore-based equipment for testing at sea. Although these methods can obtain high-precision data, they also have significant limitations,

[0004] The scaled model test may deviate from the test results due to the scale effect and material differences, and cannot fully reflect the electromagnetic scattering characteristics of the actual ship. At the same time, the test is usually carried out under experimental conditions, making it difficult to truly reproduce the running state of the ship in the actual marine environment and its impact on the RCS. When testing at sea, the test radar is set up on the shore, and the ship target moves in the near-sea area at a certain distance from the shore to complete the test. However, there are many restrictions on the test site in the near-sea area due to the presence of reefs and marine aquaculture facilities. The ship target may have to travel a long distance from the base to reach the suitable test area, which seriously affects the test efficiency. At the same time, the sea wave pattern in the near-sea area is different from that in the open sea, which affects the coupling between the target and the sea waves, which will have some impact on the measurement of the target characteristics.

[0005] In particular, testing the RCS of a ship in an open sea scenario presents the following technical challenges, including:

[0006] (1) No fixed test facilities: There are no facilities such as ship rotation platforms and fixed radar stations that can be deployed in the open sea, and mobile / followable test systems are needed. In particular, in the open sea test, the wind and waves are large, which puts higher requirements on the endurance and wind resistance of the unmanned aerial vehicle, as well as the power required for the radar to test in a harsh environment, especially in a high-power, multi-band, and multi-polarization environment;

[0007] (2) Dynamic measurement requirements: The ship to be tested in the open sea needs to sail according to the actual working conditions, rather than being stationary or rotating passively. The problem of "radar alignment in motion" needs to be solved to enable the unmanned aerial vehicle to perform multi-directional testing without affecting the ship being tested, and to simulate the real battle environment more realistically;

[0008] Therefore, how to obtain more realistic data on the scattering characteristics of ships in the open ocean environment, so as to obtain more practical test results, reduce the limitations of the test site, and improve the test efficiency, has become a technical problem that needs to be solved by existing technologies. Summary of the Invention

[0009] The purpose of this invention is to propose a system and method for testing the RCS of ships in open sea, overcoming limitations on testing locations, improving testing efficiency, and increasing the realism of the tests. Furthermore, it enables long-endurance, multi-mode, multi-band, and even multi-sea-state RCS testing through tethered unmanned aerial vehicles (UAVs).

[0010] To achieve this objective, the present invention adopts the following technical solution:

[0011] An apparatus for testing the RCS of ships at sea, comprising:

[0012] Unmanned aerial vehicles (UAVs), the ship being tested, the control station, and the platform;

[0013] The drone includes a positioning module, a radar module, and a communication module. The drone is a tethered drone and is connected to the carrier platform via an active cable.

[0014] The positioning module is installed on the drone and is used to provide the drone's location and altitude information;

[0015] The radar module is used to emit radar electromagnetic waves to continuously test the ship under test moving along a predetermined track, and to receive and store radar echoes. The radar module is equipped with a dynamic alignment unit that can adjust the antenna pointing according to the tracking command of the control station.

[0016] The communication module is used to transmit the UAV's position, altitude information, radar electromagnetic wave transmission and reception information, and flight status information to the control station, and to receive flight control from the control station; the communication module can be wired and / or wireless.

[0017] The control station is used to send and receive control information and radar test information for the UAV via wired and / or wireless means, control the flight and testing of the UAV, and realize the RCS calculation of the tested ship. The control station is equipped with a dynamic tracking module, which is used to generate antenna alignment instructions through video tracking technology or satellite positioning guidance technology, and control the antenna to always be aligned with the tested ship moving along the predetermined track.

[0018] The support platform provides power and stable support to the tethered drone via active cables.

[0019] Optionally, the load-bearing platform can be a mobile load-bearing platform or a fixed load-bearing platform.

[0020] The mobile support platform includes small boats or accompanying vessels.

[0021] The fixed support platform includes offshore drilling platforms, observation platforms, or aquaculture platforms.

[0022] Optionally, the wireless communication method is short-range wireless communication (WIFI, Bluetooth) or long-range wireless communication (5G, satellite communication, microwave communication);

[0023] The control station can be located on land, on the ship being tested, or on the carrier platform.

[0024] When the control station is located on land, long-range wireless communication is used.

[0025] When the control station is set up on the ship or platform being tested, short-range or long-range wireless communication methods are used.

[0026] Optionally, the active cable can transmit power, control signals and communication signals simultaneously. The tensile strength of the active cable is not less than 1000N, and the salt spray corrosion resistance level is not less than the 96-hour neutral salt spray test standard specified in GB / T 10125-2021, so as to adapt to the harsh offshore environment.

[0027] Optionally, the mobile carrier platform is equipped with a ship tracking radar to assist in locating the real-time position of the ship under test and to transmit the position information to the control station to coordinate the adjustment of the flight trajectory of the tethered UAV.

[0028] Optionally, a calibration reflector is also included, which is a metal sphere or corner reflector with a known radar cross-section and an error not exceeding ±0.5dB, used to calibrate the transmit / receive power of the radar module at the offshore test site and verify the accuracy of the test results;

[0029] The calibration reflector is deployed on a support platform or on a temporary buoy near the ship being measured.

[0030] Optionally, the communication frequency of the communication module differs from the operating frequency of the radar module by no less than 500MHz to avoid electromagnetic interference to the RCS testing operation; and / or

[0031] The drone is also equipped with safety devices, including a parachute and floats. The buoyancy of the floats is not less than 1.2 times the maximum takeoff weight of the drone, in order to improve the safety of offshore operations.

[0032] The present invention further discloses a testing method using the above-described device, characterized by comprising the following steps:

[0033] Distance range test step S110:

[0034] Based on the radar antenna parameters and test mode, combined with the maximum size D of the tested ship in the open sea, ship Determine the distance range R between the UAV and the ship being measured. range ;

[0035] The test modes include far-field testing and near-field testing.

[0036] In far-field testing, the distance range R between the drone and the tested ship was... range for

[0037]

[0038] In the formula, max represents the maximum value, L is the protection width to ensure that the tested ship can be stably covered by the antenna beam, and θ radar This refers to the width of the main lobe of the radar antenna beam.

[0039] In near-field testing, the distance range R between the drone and the tested ship was... range for

[0040]

[0041] In the formula denoted as the angular width of the near-field and far-field transformation, and f as the radar test frequency;

[0042] Sea area determination step S120:

[0043] Taking into account the effects of the Earth's curvature and atmospheric refraction in the open ocean, the flight altitude H of the UAV and the distance R between the UAV and the ship being measured were determined. M The relationship between them

[0044] Flight altitude range H range The following relationship, as shown in equation (3), needs to be satisfied:

[0045]

[0046] Where, θ sq The maximum allowable incident angle is set between 5° and 15° to simulate the illumination scenario of offshore sea-skimming radar. Based on this relationship, offshore sea areas without reefs and with sea state level ≤ 4 are selected.

[0047] Test system setup step S130:

[0048] The tested ship proceeds to the starting point of the predetermined trajectory, and the carrier platform is deployed to the side and rear of the tested ship, at a distance greater than R. range To avoid interfering with radar echoes, the tethered drone is raised, its position is calibrated using the positioning module, the antenna pointing direction of the radar module is adjusted to align it with the ship being tested, and the power calibration of the radar module is completed using a calibration reflector.

[0049] Tracking and testing the tested ship, procedure S140:

[0050] The tested ship operates according to a predetermined trajectory and conditions. The control station's dynamic tracking module generates antenna alignment commands in real time using video tracking technology or satellite positioning guidance technology, adjusting the radar module's antenna pointing to ensure that the radar antenna beam always covers the tested ship. The radar module continuously tracks and tests, recording the radar module's transmit power P every 0.5 seconds. iM Received power P rM Each test shall last no less than 30 minutes;

[0051] Calibration step S150:

[0052] At least one on-site calibration should be performed during the test, preferably every 10 minutes: Deploy the calibration reflector in the lateral area between the UAV and the ship under test to avoid blocking the ship's echo, and record the distance R between the standard calibration reflector and the tethered UAV. D σ, the radar cross-section of the standard calibration body D Transmit power P iD and received power P rD ;

[0053] RCS calculation steps for the tested ship S160:

[0054] The radar cross section σ of the tested ship is calculated using formula (4). M ,

[0055] Radar cross section σ of the tested ship M for

[0056]

[0057] And for σ within a single test duration M The arithmetic mean is calculated to remove outliers caused by wave reflection, resulting in the final RCS measurement.

[0058] Optionally, in step S140, the design of the predetermined trajectory must meet the following requirement: the relative distance change rate between the tested ship and the carrier platform does not exceed 5 knots, so as to ensure that the length of the active cable of the tethered UAV does not need to be frequently adjusted.

[0059] Optionally, in step S160, outlier removal employs the 3σ criterion: calculating all σ values... M The mean μ and standard deviation σ of the data are used to remove data that are outside the range of [μ-3σ, μ+3σ], and then the remaining data are averaged.

[0060] The present invention has achieved the following beneficial effects:

[0061] (1) A series of adaptive designs were made for RCS testing of moving ships in the open sea, including the use of tethered UAVs to provide high-power, continuous and stable power supply through active cables; dynamic alignment units were set on the radar of the UAVs and dynamic tracking modules of the control station to achieve accurate testing in the "moving" to "moving" mode, and to realize RCS testing in the open sea under high sea state conditions with multiple bands, multiple modes, multiple distances, large distances and high power, which is more adapted to the real sea conditions of open sea operations and improves the effectiveness and authenticity of the test.

[0062] (2) The test method takes into account the real ocean test environment and makes a series of optimizations in the test mode, flight altitude, sea wave echo, etc. The calibration steps are performed regularly in short cycles during the test to avoid the error from increasing continuously in the RCS test and improve the test accuracy. Attached Figure Description

[0063] Figure 1 This is a framework diagram of a system for testing the RCS of a test ship in the open sea according to a specific embodiment of the present invention;

[0064] Figure 2 This is a block diagram of a tethered unmanned aerial vehicle according to a specific embodiment of the present invention;

[0065] Figure 3 This is a flowchart of a method for testing the RCS of a ship at sea according to a specific embodiment of the present invention.

[0066] The technical features referred to by the reference numerals in the figure are as follows:

[0067] 1. Unmanned Aerial Vehicle (UAV); 2. Platform; 3. Ship under test; 4. Active cable; 5. Control station; 10. Positioning module; 20. Radar module; 30. Communication module. Detailed Implementation

[0068] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0069] The main features of this invention are: using a tethered UAV and a carrier platform to measure the radar cross-section (RCS) of a target ship in open sea, and then transmitting the measured data to a control station via wired and / or wireless means. The control station controls the UAV and calculates the RCS. The UAV's radar module is equipped with a dynamic alignment unit, and the control station is equipped with a dynamic tracking module. This module generates antenna alignment commands using video tracking technology or satellite positioning guidance technology, ensuring the antenna is always aligned with the target ship moving along a predetermined track. This enables long-endurance, high-power, multi-polarization radar testing in open sea, reduces the impact of wind and waves on the test, improves the UAV's alignment accuracy with the target ship, and achieves precise testing in a "moving" to "moving" mode.

[0070] For details, see Figure 1 , Figure 2 The diagram shows a block diagram of a system for testing the RCS of ships at sea according to the present invention, and a block diagram of an unmanned aerial vehicle, including:

[0071] 1. Unmanned aerial vehicle (UAV), 3. Ship under test, 5. Control station, and 2. Carrier platform;

[0072] The drone includes a positioning module 10, a radar module 20, and a communication module 30.

[0073] The drone 1 is a tethered drone, connected to the support platform 2 via an active cable.

[0074] The positioning module 10 is installed on the drone 1 and is used to provide the drone 1's position and altitude information;

[0075] The radar module 20 is used to emit radar electromagnetic waves to continuously test the ship 3 under test moving along a predetermined track, and to receive and store radar echoes. The radar module 20 is equipped with a dynamic alignment unit, which can adjust the antenna pointing according to the tracking command of the control station 5. Therefore, since the ship 3 under test moves along the predetermined track, the test of the ship 3 under test by the UAV 1 is a kind of "movement" to "movement" motion test, which is quite difficult. Moreover, the test is conducted in the open sea environment with large winds and waves, making it difficult to maintain stability. Therefore, the radar module 20 of the present invention is equipped with a dynamic alignment module, which can adjust the antenna pointing according to the tracking command of the control station 5 to improve the accuracy and adaptability of the test.

[0076] The communication module 30 is used to transmit the UAV's position, altitude information, radar electromagnetic wave transmission and reception information, and flight status information to the control station, and to receive flight control from the control station; the communication module can be wired and / or wireless.

[0077] Control station 5 is used to send and receive control information and radar test information of the UAV via wired and / or wireless means, control the flight and testing of the UAV, and realize the RCS calculation of the tested ship 3. The control station is equipped with a dynamic tracking module, which is used to generate antenna alignment instructions through video tracking technology or satellite positioning guidance technology, and control the antenna to always be aligned with the tested ship moving along the predetermined track.

[0078] The carrier platform 2 provides power and stable support to the tethered drone via an active cable.

[0079] Therefore, since this invention continuously tests the ship 3 under test moving along a predetermined track in an open sea environment, the test time is long, lasting several hours or days. In the open sea environment, with wind and waves, conventional drones are difficult to operate continuously. Furthermore, both the ship under test and the drone are in a dynamic and unstable state and are also affected by wind and waves.

[0080] Therefore, this invention uses a tethered drone to provide a high-power, continuous, and stable power supply through an active cable, which enables the drone to work continuously and cope with harsh offshore environments such as high winds and waves. It also provides the radar with high power and multi-polarization radar band selection, reducing the impact of offshore winds and waves on the test.

[0081] Furthermore, by setting up a dynamic alignment unit on the UAV and a dynamic tracking module in the control station, the alignment accuracy of the UAV with the tested ship can be further improved, enabling precise testing in a "moving" to "moving" mode.

[0082] The supporting platform 2 can be a mobile supporting platform or a fixed supporting platform.

[0083] The mobile support platform includes small boats or accompanying vessels.

[0084] The fixed support platform includes offshore drilling platforms, observation platforms, or aquaculture platforms.

[0085] The wireless communication method is short-range wireless communication (e.g., WIFI, Bluetooth) or long-range wireless communication (e.g., 5G, satellite communication, microwave communication);

[0086] Control station 5 can be set up on land, on the ship being tested, or on the carrier platform;

[0087] When control station 5 is located on land, long-range wireless communication is used.

[0088] When the control station 5 is located on the ship under test 3 or the carrier platform 2, short-range or long-range wireless communication is used.

[0089] Those skilled in the art should know that, whether it is a mobile or fixed carrier platform, it should be placed on the opposite side of the ship or drone being tested during the test to avoid affecting the test results.

[0090] Preferably, a mobile carrier platform is used, with the control station set up on the mobile carrier platform. RCS measurement is carried out by tethered UAVs, which not only expands the working range, working time and radar working parameters of the UAVs, but also allows them to follow the movement of the ship being tested, greatly expanding the testing flexibility and convenience, and facilitating the selection of testing sea areas.

[0091] The active cable 4 can transmit power, control signals and communication signals simultaneously, enabling the UAV 1 to measure the ship under test 3 for a long time. It can also support large UAVs equipped with various large radars to measure different signals of the ship under test 3, or use large UAVs to achieve multi-band, multi-mode and multi-distance RCS testing.

[0092] Furthermore, the active cable 4 has a tensile strength of not less than 1000N and a salt spray corrosion resistance level of not less than the 96-hour neutral salt spray test standard specified in GB / T 10125-2021, in order to adapt to the harsh offshore environment.

[0093] In addition, the mobile carrier platform is equipped with a ship tracking radar to assist in locating the real-time position of the ship under test 3 and transmit the position information to the control station 5 to coordinate the adjustment of the flight trajectory of the tethered UAV.

[0094] Furthermore, the testing system of the present invention also includes a calibration reflector, which is used to provide a reference benchmark with known radar scattering characteristics to calibrate and verify the accuracy of the test results. The calibration reflector can be further verified and validated on-site.

[0095] The calibration reflector is a metal sphere or corner reflector with a known radar cross-section and an error not exceeding ±0.5dB. It is used to calibrate the transmit / receive power of the radar module at the offshore test site and verify the accuracy of the test results.

[0096] The calibration reflector is deployed on the carrier platform 2 or on a temporary buoy near the ship being measured 3.

[0097] The drone 1 is further equipped with safety devices, including parachutes and floats, to enhance the safety of operations.

[0098] Further, see Figure 3 The present invention further discloses a testing method for the system used for testing as described above, comprising the following steps:

[0099] Distance range test step S110:

[0100] Based on the radar antenna parameters and test mode, combined with the maximum size D of the tested ship in the open sea, ship Determine the distance range R between the UAV and the ship being measured. range .

[0101] The test modes include far-field testing and near-field testing.

[0102] In far-field testing, the distance range R between the drone and the tested ship was... range for

[0103]

[0104] In the formula, max represents the maximum value, L is the protection width to ensure that the tested ship can be stably covered by the antenna beam, and θ radar This refers to the width of the main lobe of the radar antenna beam.

[0105] In near-field testing, the distance range R between the drone and the tested ship was... range for

[0106]

[0107] In the formula denoted as angular width for near-field and far-field transformation, and f as radar test frequency.

[0108] Where L is the protection width that ensures the tested ship can be stably covered by the antenna beam, typically D. ship Half to 1.5 times the amount is used to compensate for track deviations of ships at sea.

[0109] Sea area determination step S120:

[0110] Taking into account the effects of the Earth's curvature and atmospheric refraction in the open ocean, the flight altitude H of the UAV and the distance R between the UAV and the ship being measured were determined. M The relationship between them

[0111] Flight altitude range H range The following relationship, as shown in equation (3), needs to be satisfied:

[0112]

[0113] Where, θ sq The maximum permissible incident angle, ranging from 5° to 15°, is used to simulate offshore sea-skimming radar illumination scenarios. Based on this relationship, offshore sea areas without reefs and with sea state level ≤ 4 are selected.

[0114] Sea area determination step S120:

[0115] Determine the drone's flight altitude H and the distance R between the drone and the ship being measured.M Based on the relationship between the two, a suitable sea area for measurement is determined.

[0116] Specifically, in order to meet the low-altitude grazing conditions, the electromagnetic wave is incident almost parallel to the sea surface, and the maximum allowable incident angle θ is determined. sq The value of H represents the flight altitude range. range for

[0117] H range <R range sinθ sq

[0118] At the same time, ensuring that electromagnetic waves still propagate in a straight line after taking into account atmospheric refraction and the curvature of the Earth, the effective line-of-sight distance is calculated based on the antenna height.

[0119]

[0120] Therefore, considering the effects of the Earth's curvature and atmospheric refraction in the open ocean, the flight altitude H of the UAV and the distance R between the UAV and the ship being measured were determined. M The relationship between the flight altitude range H range The following relationship, as shown in equation (3), needs to be satisfied:

[0121]

[0122] Therefore, that is, the drone's flight altitude H and the distance R between the drone and the ship being measured... M It satisfies formula (3).

[0123] By combining formulas (1)-(3) from steps S110 and S120, the distance R between the tethered UAV and the measured ship is determined. M The appropriate sea area for measurement is determined by the flight altitude H of the tethered drone.

[0124] Where, θ sq The maximum allowable incident angle is set between 5° and 15° to simulate the illumination scenario of sea-skimming radar in the open ocean. Based on this relationship, open ocean areas without reefs and with sea state level ≤ 4 are selected.

[0125] Test system setup step S130:

[0126] The tested ship proceeds to the starting point of the predetermined trajectory, and the carrier platform is deployed to the side and rear of the tested ship, at a distance greater than R. range To avoid interfering with radar echoes, the tethered UAV is raised, its position is calibrated using the positioning module, the antenna pointing direction of the radar module is adjusted to align it with the ship being tested, and the power calibration of the radar module is completed using a calibration reflector.

[0127] Therefore, the impact of radar echoes under high sea states was explicitly considered when setting up the test environment.

[0128] Tracking and testing the tested ship, procedure S140:

[0129] The tested ship operates according to a predetermined trajectory and conditions. The control station's dynamic tracking module generates antenna alignment commands in real time using video tracking technology or satellite positioning guidance technology, adjusting the radar module's antenna pointing to ensure that the radar antenna beam always covers the tested ship. The radar module continuously tracks and tests, recording the radar module's transmit power P every 0.5 seconds. iM Received power P rM Each test should last no less than 30 minutes.

[0130] In this step, the dynamic tracking module generates antenna alignment commands in real time through video tracking technology or satellite positioning guidance technology, which improves the adaptive alignment measures and enhances the test accuracy for offshore radar RCS testing.

[0131] Calibration step S150:

[0132] At least one on-site calibration should be performed during the test: the calibration reflector should be deployed in the lateral area between the UAV and the ship under test to avoid obstructing the ship's echo, and the distance R between the standard calibration reflector and the tethered UAV should be recorded. D σ, the radar cross-section of the standard calibration body D Transmit power P iD and received power P rD .

[0133] In one specific embodiment, on-site calibration can be performed every 10 minutes to improve the testing accuracy during the testing process.

[0134] During offshore testing, the tested ship always travels along a predetermined track, while the drone dynamically tracks it, resulting in constantly changing errors between the two. Therefore, this invention performs periodic calibration, for example, on-site calibration every 10 minutes, and takes into account the influence of the ship's echo, thus improving the accuracy of the test.

[0135] RCS calculation steps for the tested ship S160:

[0136] The radar cross section σ of the tested ship is calculated using formula (4). M ,

[0137] The radar cross-section of the tested ship is

[0138]

[0139] In step S140, the design of the predetermined trajectory must meet the following requirement: the relative distance change rate between the tested ship and the carrier platform does not exceed 5 knots, so as to ensure that the cable length of the tethered UAV does not need to be frequently adjusted.

[0140] In step S160, outlier removal employs the 3σ criterion: calculating all σ values... M The mean μ and standard deviation σ of the data are used to remove data that are outside the range of [μ-3σ, μ+3σ], and then the remaining data are averaged.

[0141] The present invention has achieved the following beneficial effects:

[0142] (1) A series of adaptive designs were made for RCS testing of moving ships in the open sea, including the use of tethered UAVs to provide high-power, continuous and stable power supply through active cables; dynamic alignment units were set on the radar of the UAVs and dynamic tracking modules of the control station to achieve accurate testing in the "moving" to "moving" mode, and to realize RCS testing in the open sea under high sea state conditions with multiple bands, multiple modes, multiple distances, large distances and high power, which is more adapted to the real sea conditions of open sea operations and improves the effectiveness and authenticity of the test.

[0143] (2) The test method takes into account the real ocean test environment and makes a series of optimizations in the test mode, flight altitude, sea wave echo, etc. The calibration steps are performed regularly in short cycles during the test to avoid the error from increasing continuously in the RCS test and improve the test accuracy.

[0144] Obviously, those skilled in the art will understand that the various units or steps of the present invention described above can be implemented using general-purpose computing devices. They can be centralized on a single computing device, or alternatively, they can be implemented using computer-executable program code, thereby allowing them to be stored in a storage device for execution by the computing device. Alternatively, they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. Thus, the present invention is not limited to any particular combination of hardware and software.

[0145] The above description is a further detailed explanation of the present invention in conjunction with specific preferred embodiments. It should not be considered that the specific embodiments of the present invention are limited to this. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered to fall within the scope of protection of the present invention as defined by the submitted claims.

Claims

1. A system for testing the RCS of ships at sea, characterized in that, include: Unmanned aerial vehicles (UAVs), the ship being tested, the control station, and the platform; The drone includes a positioning module, a radar module, and a communication module. The drone is a tethered drone and is connected to the carrier platform via an active cable. The positioning module is installed on the drone and is used to provide the drone's location and altitude information; The radar module is used to emit radar electromagnetic waves to continuously test the ship under test moving along a predetermined track, and to receive and store radar echoes. The radar module is equipped with a dynamic alignment unit that can adjust the antenna pointing according to the tracking command of the control station. The communication module is used to transmit the UAV's position, altitude information, radar electromagnetic wave transmission and reception information, and flight status information to the control station, and to receive flight control from the control station; the communication module can be wired and / or wireless. The control station is used to send and receive control information and radar test information for the UAV via wired and / or wireless means, control the flight and testing of the UAV, and realize the RCS calculation of the tested ship. The control station is equipped with a dynamic tracking module, which is used to generate antenna alignment instructions through video tracking technology or satellite positioning guidance technology, and control the antenna to always be aligned with the tested ship moving along the predetermined track. The support platform provides power and stable support to the tethered drone via active cables.

2. The system according to claim 1, characterized in that: The load-bearing platform can be a mobile load-bearing platform or a fixed load-bearing platform. The mobile support platform includes small boats or accompanying vessels. The fixed support platform includes offshore drilling platforms, observation platforms, or aquaculture platforms.

3. The system according to claim 2, characterized in that: The wireless communication method is either short-range wireless communication (WIFI, Bluetooth) or long-range wireless communication (5G, satellite communication, microwave communication); The control station can be located on land, on the ship being tested, or on the carrier platform. When the control station is located on land, long-range wireless communication is used. When the control station is set up on the ship or platform being tested, short-range or long-range wireless communication methods are used.

4. The system according to claim 1, characterized in that: The active cable can transmit power, control signals and communication signals simultaneously. The tensile strength of the active cable is not less than 1000N, and the salt spray corrosion resistance level is not less than the 96-hour neutral salt spray test standard specified in GB / T 10125-2021, so as to adapt to the harsh offshore environment.

5. The system according to any one of claims 1-4, characterized in that: It also includes a calibration reflector, which is a metal sphere or corner reflector with a known radar cross-section and an error not exceeding ±0.5dB, used to calibrate the transmit / receive power of the radar module at the offshore test site and verify the accuracy of the test results; The calibration reflector is deployed on a support platform or on a temporary buoy near the ship being measured.

6. The system according to claim 5, characterized in that: The communication frequency of the communication module differs from the operating frequency of the radar module by no less than 500MHz to avoid electromagnetic interference to the RCS testing operation; and / or The drone is also equipped with safety devices, including a parachute and floats. The buoyancy of the floats is not less than 1.2 times the maximum takeoff weight of the drone, in order to improve the safety of offshore operations.

7. A testing method for the system according to any one of claims 1-6, characterized in that, Includes the following steps: Distance range test step S110: Based on the radar antenna parameters and test mode, combined with the maximum size D of the tested ship in the open sea, ship Determine the distance range R between the UAV and the ship being measured. range ; The test modes include far-field testing and near-field testing. In far-field testing, the distance range R between the drone and the tested ship was... range for In the formula, max represents the maximum value, L is the protection width to ensure that the tested ship can be stably covered by the antenna beam, and θ radar This refers to the width of the main lobe of the radar antenna beam. In near-field testing, the distance range R between the drone and the tested ship was... range for In the formula denoted as the angular width of the near-field and far-field transformation, and f as the radar test frequency; Sea area determination step S120: Taking into account the effects of the Earth's curvature and atmospheric refraction in the open ocean, the flight altitude H of the UAV and the distance R between the UAV and the ship being measured were determined. M The relationship between them Flight altitude range H range The following relationship, as shown in equation (3), needs to be satisfied: Where, θ sq The maximum allowable incident angle is set between 5° and 15° to simulate the illumination scenario of offshore sea-skimming radar. Based on this relationship, offshore sea areas without reefs and with sea state level ≤ 4 are selected. Test system setup step S130: The tested ship proceeds to the starting point of the predetermined trajectory, and the carrier platform is deployed to the side and rear of the tested ship, at a distance greater than R. range To avoid interfering with radar echoes, the tethered drone is raised, its position is calibrated using the positioning module, the antenna pointing direction of the radar module is adjusted to align it with the ship being tested, and the power calibration of the radar module is completed using a calibration reflector. Tracking and testing the tested ship, procedure S140: The tested ship operates according to a predetermined trajectory and conditions. The control station's dynamic tracking module generates antenna alignment commands in real time using video tracking technology or satellite positioning guidance technology, adjusting the radar module's antenna pointing to ensure that the radar antenna beam always covers the tested ship. The radar module continuously tracks and tests, recording the radar module's transmit power P every 0.5 seconds. iM Received power P rM Each test shall last no less than 30 minutes; Calibration step S150: At least one on-site calibration should be performed during the test: the calibration reflector should be deployed in the lateral area between the UAV and the ship under test to avoid obstructing the ship's echo, and the distance R between the standard calibration reflector and the tethered UAV should be recorded. D σ, the radar cross-section of the standard calibration body D Transmit power P iD and received power P rD ; RCS calculation steps for the tested ship S160: The radar cross section σ of the tested ship is calculated using formula (4). M , Radar cross section σ of the tested ship M for And for σ within a single test duration M The arithmetic mean is calculated to remove outliers caused by wave reflection, resulting in the final RCS measurement.

8. The test method according to claim 7, characterized in that: In step S140, the design of the predetermined trajectory must meet the following requirements: the relative distance change rate between the tested ship and the carrier platform shall not exceed 5 knots, so as to ensure that the length of the active cable of the tethered UAV does not need to be frequently adjusted.

9. The test method according to claim 7, characterized in that: In step S160, outlier removal employs the 3σ criterion: calculating all σ values... M The mean μ and standard deviation σ of the data are used to remove data that are outside the range of [μ-3σ, μ+3σ], and then the remaining data are averaged.

Images