Method and device for calibrating radar cross section of soft target at rear end of passenger car

Abstract

This invention discloses a method and apparatus for calibrating the radar cross-section (RCS) of a rear-end software target object in a passenger vehicle, relating to the field of calibration technology for software targets used in intelligent connected vehicle testing. The method includes the following steps: fixing a corner reflector, moving a radar within a preset distance range to obtain the actual RCS of the corner reflector; determining a correction coefficient for the radar based on the difference between the actual RCS of the corner reflector and its nominal RCS; replacing the corner reflector with a rear-end software target object of the passenger vehicle, moving the radar within a preset distance range to obtain the actual RCS of the rear-end software target object; correcting the actual RCS of the rear-end software target object according to the correction coefficient to obtain a calibration result, and determining whether the calibration result is accurate based on a preset value.

Description

Technical Field

[0001] This invention relates to the field of software target calibration technology for intelligent connected vehicle testing, specifically to a method and device for calibrating the radar cross-section of software targets at the rear end of a passenger vehicle. Background Technology

[0002] The rear-end software target object for passenger vehicles is a crucial testing device for performance testing of Advanced Driver Assistance Systems (ADAS) and active safety systems. Its function is to represent the real vehicle in terms of detectability and motion, replicating its size, shape, and scattering properties. Furthermore, it must pose no safety threat to the test vehicle or test operators during testing, and the test vehicle should remain undamaged upon contact with the target. Therefore, the performance of the target object directly affects the test results and is crucial to the safety of test personnel and the test vehicle.

[0003] Currently, all passenger vehicle backend software targets used for testing in China are imported. While they undergo factory verification, most are only used for visual confirmation during use, failing to fully reflect their ability to completely replace real vehicles. Based on the current perception technologies used in intelligent connected vehicles, the targets should possess similar performance to real vehicles in terms of shape, size, radar reflectivity, and infrared reflectivity. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method and apparatus for calibrating the radar cross-section of soft targets at the rear end of passenger vehicles, which can be used for calibrating the radar reflection performance of soft targets at the rear end of passenger vehicles.

[0005] To achieve the above objectives, this application adopts the following technical solution:

[0006] Firstly, a method for calibrating the radar cross-section of a soft target object at the rear end of a passenger vehicle is provided, comprising the following steps:

[0007] A fixed corner reflector is used, and the radar is moved within a preset distance range to obtain the actual radar cross-section of the corner reflector.

[0008] The correction factor for the radar is determined based on the difference between the actual radar cross-section and the nominal radar cross-section of the corner reflector.

[0009] The corner reflector is replaced with a soft target object at the rear of a passenger vehicle. The radar is moved within a preset distance range to obtain the actual radar cross-section of the soft target object at the rear of the passenger vehicle.

[0010] The actual radar cross-section of the rear-end soft target of the passenger vehicle is corrected according to the correction coefficient to obtain the calibration result, and the accuracy of the calibration result is determined based on the preset value.

[0011] In some embodiments, the fixed corner reflector, by moving the radar within a preset distance, and obtaining the radar cross-section of the corner reflector, includes the following steps:

[0012] Set up corner reflectors and adjust the radar center position to match the corner reflector center position;

[0013] Move the radar within a preset distance range, get close to the corner reflector, and obtain the median value of the radar cross section of the corner reflector in a single radar movement RCS measurement.

[0014] The measurement was repeated multiple times, and the average value of the median radar cross-section of the multiple corner reflectors was taken as the actual radar cross-section of the corner reflector.

[0015] In some embodiments, replacing the corner reflector with a soft target object at the rear of a passenger vehicle, moving the radar within a preset distance, and obtaining the actual radar cross-section of the soft target object at the rear of the passenger vehicle includes the following steps:

[0016] Remove the corner reflector and place the target object in the same position;

[0017] The radar moves within a preset distance range, approaches the soft target object at the rear of the passenger vehicle, and divides the preset distance range into multiple segments;

[0018] Calculate the average radar cross-section of the soft target of the passenger vehicle within each distance range, and use it as the actual radar cross-section of the soft target of the passenger vehicle within that distance range.

[0019] In some embodiments, the preset distance range is 4m-60m from the angle reflector or the rear-end software target of the passenger vehicle.

[0020] In some embodiments, the preset distance range is divided into: 4m-5m as the near segment, 5m-34m as the middle segment, and 34m-60m as the far segment.

[0021] Secondly, a radar cross-section calibration device for soft targets at the rear end of a passenger vehicle is provided, comprising:

[0022] The acquisition unit is used to fix the corner reflector, move the radar within a preset distance range, and obtain the actual radar cross-section of the corner reflector.

[0023] The calculation unit is used to determine the correction coefficient of the radar based on the difference between the actual radar cross-section of the corner reflector and the nominal radar cross-section of the corner reflector.

[0024] The acquisition unit is also used to replace the corner reflector with a soft target object at the rear of a passenger vehicle, move the radar within a preset distance range, and obtain the actual radar cross-section of the soft target object at the rear of the passenger vehicle.

[0025] The calculation unit is also used to correct the actual radar cross-section of the rear-end soft target of the passenger vehicle according to the correction coefficient, obtain the calibration result, and determine whether the calibration result is accurate based on the set preset value.

[0026] In some embodiments, the acquisition unit is used for:

[0027] Set up corner reflectors and adjust the radar center position to match the corner reflector center position;

[0028] Move the radar within a preset distance range, get close to the corner reflector, and obtain the median value of the radar cross section of the corner reflector in a single radar movement RCS measurement.

[0029] The computing unit is used for:

[0030] The measurement was repeated multiple times, and the average value of the median radar cross-section of the multiple corner reflectors was taken as the actual radar cross-section of the corner reflector.

[0031] In some embodiments, the acquisition unit is used for:

[0032] Remove the corner reflector and place the target object in the same position;

[0033] The radar moves within a preset distance range, approaches the soft target object at the rear of the passenger vehicle, and divides the preset distance range into multiple segments;

[0034] The calculation unit is used to: calculate the average radar cross-section of the soft target of the passenger vehicle within each distance range, and use it as the actual radar cross-section of the soft target of the passenger vehicle within that distance range.

[0035] In some embodiments, the preset distance range is 4m-60m from the angle reflector or the rear-end software target of the passenger vehicle.

[0036] In some embodiments, the preset distance range is divided into: 4m-5m as the near segment, 5m-34m as the middle segment, and 34m-60m as the far segment.

[0037] In this invention, a fixed corner reflector is used to move the radar within a preset distance range to obtain the actual radar cross-section (RCS) of the corner reflector. A correction coefficient for the radar is determined based on the difference between the actual RCS and the nominal RCS of the corner reflector. The corner reflector is then replaced with a soft target object at the rear of a passenger vehicle, and the radar is moved within a preset distance range to obtain the actual RCS of the soft target object. The actual RCS of the soft target object at the rear of the passenger vehicle is corrected according to the correction coefficient to obtain a calibration result. Based on a preset value, the accuracy of the calibration result is determined. This method provides a good way to calibrate the radar before use. Attached Figure Description

[0038] Figure 1 This is a flowchart of a method for calibrating the radar cross section of a soft target object at the rear end of a passenger vehicle, as described in an embodiment of the present invention.

[0039] Figure 2 This is a flowchart of a method for calibrating the radar cross section of a soft target object at the rear end of a passenger vehicle according to an embodiment of the present invention;

[0040] Figure 3 This is a flowchart of S3, a method for calibrating the radar cross section of a soft target object at the rear end of a passenger vehicle, according to an embodiment of the present invention.

[0041] Figure 4 This is a schematic diagram of a radar cross section calibration device for a soft target object at the rear end of a passenger vehicle, according to an embodiment of the present invention. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0043] First, the relevant concepts involved in this invention will be explained.

[0044] RCS (Radio Cross Section) is a physical quantity that measures the intensity of the echo produced by a target under radar illumination. It is an imaginary area of ​​the target, represented by the projected area of ​​an isotropic equivalent reflector. This equivalent reflector has the same echo power as the defined target within a unit solid angle in the receiving direction. The unit is square meters, usually denoted by the symbol σ. Besides using square meters to reflect the radar cross section, another more common method is to express it as ten times the logarithm of the radar cross section, with the unit being decibels per square meter, denoted as dBsm, or σ. dBsm =10·lgσ sm Its size depends primarily on the target's parameters (such as the target's shape, size, and surface electrical properties), radar parameters (such as the polarization of the primary field, wavelength, etc.), and the target's viewing angle.

[0045] In actual field measurements, the power received by the receiver is affected by factors such as transmitter and receiver feeder losses, atmospheric losses along the ray path, measurement distance, weather conditions, and ground reflection. Therefore, a calibration body with a known cross-sectional area is typically used as the calibration reference to calibrate the radar system and eliminate the influence of radar parameters and environmental factors on the measurement results. The purpose of radar calibration is to establish a strict correspondence between the known RCS and the physical quantity output by the radar receiver, so that the unknown RCS value of the corresponding target can be obtained from the receiver measurement. This correction process is completed in software. Before each RCS calibration of the target, the radar system must be calibrated using a standard corner reflector. The RCS value of this corner reflector is close to the ideal RCS value of the target, and the centerline position of the target must be consistent with the centerline position of the corner reflector. During the calibration process, the radar path must be consistent, and the lateral offset during the movement must be less than 0.1m. This is to eliminate the influence of environmental conditions and radar parameters on the RCS measurement results.

[0046] Based on the above, the radar cross-section calibration method and apparatus for rear-end software targets in passenger vehicles provided by embodiments of the present invention are described below. See also... Figure 1 , Figure 1 This is a flowchart illustrating a method for calibrating the radar cross-section of a soft target object at the rear end of a passenger vehicle, provided in an embodiment of the present invention. Figure 1 As shown, the method includes, but is not limited to, the following steps:

[0047] S1. Fix the corner reflector, move the radar within a preset distance range, and obtain the actual radar cross-section of the corner reflector;

[0048] S2. Determine the radar correction coefficient based on the difference between the actual radar cross-section of the corner reflector and the nominal radar cross-section of the corner reflector;

[0049] S3. Replace the corner reflector with a soft target object at the rear of a passenger vehicle, move the radar within a preset distance range, and obtain the actual radar cross-section of the soft target object at the rear of the passenger vehicle.

[0050] S4. Correct the actual radar cross-section of the rear-end soft target of the passenger vehicle according to the correction coefficient to obtain the calibration result, and determine whether the calibration result is accurate based on the set preset value.

[0051] For details, see Figure 2 In step S1, the fixed corner reflector moves the radar within a preset distance to obtain the radar cross-section of the corner reflector, including the following steps:

[0052] S11. Set up the corner reflector and adjust the center position of the radar to be consistent with the center position of the corner reflector; wherein, the corner reflector is installed at a position where the center is 500mm±10mm above the ground, and the corner reflector mounting fixture is shielded with radar-absorbing material to eliminate the influence of the mounting fixture on the radar calibration; adjust the radar installation position so that its center height is consistent with the center position of the corner reflector, and the radar is close to the corner reflector so that the radar sensor is directly facing the corner reflector;

[0053] S12. Move the radar within a preset distance range, approach the corner reflector, and obtain the median value of the radar cross section of the corner reflector measured by RCS in a single radar movement.

[0054] Specifically, the vehicle is moved within a preset range, causing the radar to move within the preset range. During the movement, the radar cross-section of multiple corner reflectors measured by RCS is acquired, and the median value of the radar cross-section of the multiple corner reflectors measured by RCS is taken as the result of a single measurement.

[0055] It is worth noting that the preset range is 4m-60m from the angle reflector.

[0056] S13. Repeat the measurement multiple times, and use the average of the median values ​​of the radar cross-sections of the multiple corner reflectors as the actual radar cross-section of the corner reflector. Repeating the measurement step and obtaining multiple measurement results helps to avoid the influence of factors such as atmospheric loss along the ray path, measurement distance, weather conditions, and ground reflection during the measurement process.

[0057] In step S2, taking 5 repeated measurements as an example, according to the formula:

[0058] A = RCS B -(r1+r2+r3+r4+r5) / 5

[0059] The correction coefficient A of the radar sensor is obtained, where RCS BR1 represents the nominal radar cross-section of the standard corner reflector, and R2, R3, R4, and R5 are the median values ​​of the radar cross-section of the corner reflector measured during five calibrations.

[0060] For details, see Figure 3 In step S3, replacing the corner reflector with a soft target object at the rear of a passenger vehicle, moving the radar within a preset distance, and obtaining the actual radar cross-section of the soft target object at the rear of the passenger vehicle includes the following steps:

[0061] S31. Remove the corner reflector and place the target object in the same position;

[0062] Specifically, mark the location of the corner reflector on the ground, then remove the corner reflector and place the soft target object at the rear of the passenger vehicle in the position of the corner reflector, so that the center line of its rear surface coincides with the center of the corner reflector;

[0063] S32. Move the radar within a preset distance range, approach the soft target object at the rear of the passenger vehicle, and divide the preset distance range into multiple segments;

[0064] The vehicle is moved within a preset range, causing the radar to move within the preset range. During the movement, the radar cross-section of the rear soft target of the passenger vehicle is acquired by multiple RCS measurements. The radar cross-sections of the rear soft target of the passenger vehicle are integrated into the radar cross-section of the rear soft target of the passenger vehicle in each preset segment.

[0065] It is worth noting that the preset distance range is 4m-60m from the rear-end software target of the passenger vehicle; the preset distance range is divided into: 4m-5m as the near segment, 5m-34m as the middle segment, and 34m-60m as the far segment.

[0066] S33. Calculate the average radar cross-section of the soft-surface target of the passenger vehicle within each distance range, and use this average as the actual radar cross-section of the soft-surface target of the passenger vehicle within that distance range. Specifically, according to the formula:

[0067] rcs i =(r i1 +r i2 +r i3 +r i4 +r i5 ) / 5

[0068] The radar cross section rcs of the target measured by the radar in the i-th range segment is obtained. i , where r i1 r i2 r i3 r i4 r i5For the i-th range segment, the average value of the radar cross-section data of a single calibration of the target object in 5 calibrations.

[0069] In step S4, according to the formula:

[0070] RCS i =rcs i +A

[0071] The radar cross section (RCS) calibration result of the target in the i-th range segment is obtained. i , where rcs i Let A be the radar cross-section of the target measured by the radar in the i-th range segment, and let A be the correction coefficient of the radar sensor.

[0072] After obtaining the radar cross section calibration result of the target in the i-th range segment, it is compared with the preset value set for each segment to determine whether the calibration result is accurate.

[0073] It is worth noting that the preset values ​​are shown in Table 1.

[0074] Table 1 RCS Requirements for Each Distance Segment

[0075] Distance segment (4-5)m (5-34)m (34-60)m average value RCS 2.96±6.00 11.8±6.00 16.00±6.00 10.25±6.00

[0076] If the RCS is greater than the upper limit of the acceptable range, you can try to reduce the RCS by reducing the surface sharpness or using low reflectivity materials. If the RCS is less than the lower limit of the acceptable range, you can try to increase the RCS by adding reflectors or attaching tin foil inside.

[0077] In this invention, a fixed corner reflector is used to move the radar within a preset distance range to obtain the actual radar cross-section (RCS) of the corner reflector. A correction coefficient for the radar is determined based on the difference between the actual RCS and the nominal RCS of the corner reflector. The corner reflector is then replaced with a soft target object at the rear of a passenger vehicle, and the radar is moved within a preset distance range to obtain the actual RCS of the soft target object. The actual RCS of the soft target object at the rear of the passenger vehicle is corrected according to the correction coefficient to obtain a calibration result. Based on a preset value, the accuracy of the calibration result is determined. This method provides a good way to calibrate the radar before use.

[0078] See Figure 4 This invention also provides a radar cross section calibration device for rear-end software targets in passenger vehicles, comprising:

[0079] The acquisition unit is used to fix the corner reflector, move the radar within a preset distance range, and obtain the actual radar cross-section of the corner reflector.

[0080] The calculation unit is used to determine the correction coefficient of the radar based on the difference between the actual radar cross-section of the corner reflector and the nominal radar cross-section of the corner reflector.

[0081] The acquisition unit is also used to replace the corner reflector with a soft target object at the rear of a passenger vehicle, move the radar within a preset distance range, and obtain the actual radar cross-section of the soft target object at the rear of the passenger vehicle.

[0082] The calculation unit is also used to correct the actual radar cross-section of the rear-end soft target of the passenger vehicle according to the correction coefficient, obtain the calibration result, and determine whether the calibration result is accurate based on the set preset value.

[0083] In some embodiments, the acquisition unit is used for:

[0084] Set up corner reflectors and adjust the radar center position to match the corner reflector center position;

[0085] Move the radar within a preset distance range, approaching or moving away from the corner reflector, and obtain the median value of the radar cross section of the corner reflector measured by RCS in a single radar movement.

[0086] The computing unit is used for:

[0087] The measurement was repeated multiple times, and the average value of the median radar cross-section of the multiple corner reflectors was taken as the actual radar cross-section of the corner reflector.

[0088] In some embodiments, the acquisition unit is used for:

[0089] Remove the corner reflector and place the target object in the same position;

[0090] The radar moves within a preset distance range, approaches the soft target object at the rear of the passenger vehicle, and divides the preset distance range into multiple segments;

[0091] The calculation unit is used to: calculate the average radar cross-section of the soft target of the passenger vehicle within each distance range, and use it as the actual radar cross-section of the soft target of the passenger vehicle within that distance range.

[0092] In some embodiments, the preset distance range is 4m-60m from the angle reflector or the rear-end software target of the passenger vehicle.

[0093] In some embodiments, the preset distance range is divided into: 4m-5m as the near segment, 5m-34m as the middle segment, and 34m-60m as the far segment.

[0094] In the description of this application, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0095] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0096] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for calibrating the radar cross section of a soft target object at the rear end of a passenger vehicle, characterized in that, The method includes the following steps: A fixed corner reflector is used, and the radar is moved within a preset distance range to obtain the actual radar cross-section (RCS) of the corner reflector. Specifically, the corner reflector is set up, and the center position of the radar is adjusted to be consistent with the center position of the corner reflector. The radar is moved within a preset distance range, close to the corner reflector, and the median value of the RCS of the corner reflector in a single radar movement measurement is obtained. The measurement is repeated multiple times, and the average value of the median values ​​of the RCS of multiple corner reflectors is taken as the actual RCS of the corner reflector. The correction factor for the radar is determined based on the difference between the actual radar cross-section and the nominal radar cross-section of the corner reflector. The corner reflector is replaced with a soft target object at the rear of a passenger vehicle. The radar is moved within a preset distance range to obtain the actual radar cross-section of the soft target object at the rear of the passenger vehicle. Specifically, the corner reflector is moved away, and the target object is placed in the same position. The radar is moved within a preset distance range, close to the soft target object at the rear of the passenger vehicle, and the preset distance range is divided into multiple segments. The average value of the radar cross-section of the soft target object at the rear of the passenger vehicle within each segment is calculated as the actual radar cross-section of the soft target object at that segment. The actual radar cross-section of the rear-end soft target of the passenger vehicle is corrected according to the correction coefficient to obtain the calibration result, and the accuracy of the calibration result is determined based on the preset value.

2. The method for calibrating the radar cross section of a soft target at the rear end of a passenger vehicle as described in claim 1, characterized in that, The preset distance range is 4m-60m from the angle reflector or the rear-end software target of the passenger vehicle.

3. The method for calibrating the radar cross section of a soft target at the rear end of a passenger vehicle as described in claim 2, characterized in that, The preset distance range is divided into three segments: 4m-5m as the near segment, 5m-34m as the middle segment, and 34m-60m as the far segment.

4. A radar cross section calibration device for soft targets at the rear end of a passenger vehicle, characterized in that, include: The acquisition unit is used to fix the corner reflector, move the radar within a preset distance range, and obtain the actual radar cross-section of the corner reflector. Specifically, a corner reflector is set up, and the center position of the radar is adjusted to be consistent with the center position of the corner reflector; the radar is moved within a preset distance range, close to the corner reflector, and the median value of the radar cross section of the corner reflector measured by RCS in a single radar movement is obtained; The measurement was repeated multiple times, and the average value of the median value of the radar cross-section of the multiple corner reflectors was taken as the actual radar cross-section of the corner reflector. The calculation unit is used to determine the correction coefficient of the radar based on the difference between the actual radar cross-section of the corner reflector and the nominal radar cross-section of the corner reflector. The acquisition unit is also used to replace the corner reflector with a soft target object at the rear of a passenger vehicle, move the radar within a preset distance range, and obtain the actual radar cross-section of the soft target object at the rear of the passenger vehicle; specifically, the corner reflector is moved away, and the target object is placed in the same position; the radar is moved within a preset distance range, close to the soft target object at the rear of the passenger vehicle, and the preset distance range is divided into multiple segments; Calculate the average radar cross-section of the soft target of the passenger vehicle within each distance range, and use it as the actual radar cross-section of the soft target of the passenger vehicle within that distance range; The calculation unit is also used to correct the actual radar cross-section of the rear-end soft target of the passenger vehicle according to the correction coefficient, obtain the calibration result, and determine whether the calibration result is accurate based on the set preset value.

5. The radar cross section calibration device for soft targets at the rear end of a passenger vehicle as described in claim 4, characterized in that, The preset distance range is 4m-60m from the angle reflector or the rear-end software target of the passenger vehicle.

6. The radar cross section calibration device for a soft target at the rear end of a passenger vehicle as described in claim 5, characterized in that, The preset distance range is divided into three segments: 4m-5m as the near segment, 5m-34m as the middle segment, and 34m-60m as the far segment.

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