Perception radar imaging method and perception radar system suitable for unmanned vehicles

Abstract

The present application relates to a perception radar imaging method and a perception radar system suitable for unmanned vehicles. The method comprises: using a rotating scanning synthetic aperture radar set on the unmanned vehicle to detect the 360° range around the unmanned vehicle while the unmanned vehicle is moving, and then obtaining an intermediate frequency echo signal, and performing one-dimensional distance imaging and one-dimensional direction imaging on the intermediate frequency echo signal to obtain a 360° panoramic two-dimensional imaging, and then using the coordinate system at the current moment to perform image registration on the 360° panoramic two-dimensional imaging obtained at the previous moment to obtain a high-resolution panoramic image. In this method, an imaging method with a synthetic aperture in the shape of a long cycloid is proposed, so that when performing panoramic imaging, only one radar is needed, and the resolution of the panoramic image does not change with the azimuth.

Description

Technical Field

[0001] The present application relates to the technical field of environment perception of unmanned vehicles, and in particular to a perception radar imaging method and a perception radar system suitable for unmanned vehicles. Background Art

[0002] Autonomous driving is a new technology that revolutionizes transportation. It has broad application prospects in many fields such as smart travel, transportation, logistics, mining, ports, and other civil and military fields. After more than 50 years of technological development, autonomous driving is very close to our real life. However, due to the complexity of road conditions and high dynamic changes, environmental perception is still the key technology that restricts the effective application of autonomous vehicles and has not been completely solved.

[0003] Environmental perception is the process of identifying the surrounding environment and status of a vehicle through a variety of on-board sensors, such as cameras, lidar, microwave radar, GPS, inertial sensors, etc. It is the basis for autonomous analysis, judgment and decision-making of unmanned vehicles. Although optical, infrared and lidar sensors have been widely studied in the environmental perception of unmanned vehicles, and have achieved good obstacle detection results in structured and favorable climate and meteorological environments; however, on unstructured roads, especially in the wild, it is impossible to effectively detect raised and sunken obstacles such as tree stumps, earth slopes, and potholes. Microwave radar is becoming a hot spot in the research of environmental perception of unmanned vehicles due to its advantages such as high resolution, wide viewing angle, fast scanning, vegetation penetration, and range measurement.

[0004] Microwave radar is an important environmental perception sensor widely used in ground unmanned systems. During its development, its mission has gradually extended from vehicle collision avoidance to obstacle detection, moving target identification, terrain mapping, etc. At present, the radars used in ground unmanned systems mainly include collision avoidance radar, one-dimensional imaging radar, two-dimensional imaging radar, three-dimensional imaging radar and four-dimensional radar. Among them, two-dimensional imaging radar is the most widely used. Two-dimensional imaging radar can effectively detect static and moving targets by measuring the distance and azimuth information of the target. However, conventional two-dimensional imaging radar has the following application limitations:

[0005] 1. The detection angle is limited. In order to achieve 360° panoramic imaging, a single vehicle needs to be equipped with multiple radars. Two-dimensional imaging radars usually use broadband signals to achieve multi-target resolution along the distance direction, and use array antennas to achieve multi-target resolution along the azimuth direction. According to the array signal principle, when the target deviates from the array normal, the azimuth resolution of the radar decreases. Therefore, the effective viewing angle of a single conventional two-dimensional imaging radar is 120°. In practical applications, in order to ensure measurement accuracy, the detection viewing angle is generally 60°. Therefore, in order to achieve 360° panoramic imaging, a single unmanned vehicle usually needs to be installed with 6 to 8 two-dimensional imaging radars.

[0006] 2. Conventional two-dimensional imaging radar systems have a fixed structure and are adapted to the needs of high-performance applications. The array length and number of channels of two-dimensional imaging radars are fixed. In order to compromise between cost and performance, the array size is generally small, making it difficult to obtain high azimuth resolution, especially as the resolution deteriorates as the viewing angle deviates from the array normal direction. Therefore, it is difficult to meet the needs of long-distance high-resolution imaging. For example, the ACC adaptive cruise function of unmanned driving places extremely high demands on commonly used corner radars.

[0007] 3. Multiple radars interfere with each other, which will cause performance degradation and cost increase. Multiple radars share the same operating frequency band. If conventional radar signal systems are used, there will be serious mutual interference. In order to suppress this interference, complex technologies such as time division multiplexing, frequency division multiplexing, and code division multiplexing are required, which will result in reduced detection performance and a significant increase in system costs. Summary of the invention

[0008] Based on this, it is necessary to provide a perception radar imaging method and a perception radar system suitable for unmanned vehicles that can perform panoramic imaging using only one radar to address the above technical problems.

[0009] A perception radar imaging method applicable to an unmanned vehicle, the method comprising:

[0010] Acquire an intermediate frequency echo signal, where the intermediate frequency echo signal is a radar echo signal received by a rotating scanning synthetic aperture radar disposed on the unmanned vehicle after detecting a 360° range around the unmanned vehicle while the unmanned vehicle is moving;

[0011] Performing an inverse Fourier transform on the intermediate frequency echo signal to obtain a one-dimensional range image, then processing the one-dimensional range image to obtain a one-dimensional azimuth image, and obtaining a frame of 360° panoramic two-dimensional imaging based on the one-dimensional range image and the one-dimensional azimuth image;

[0012] The intermediate frequency echo signal is imaged and processed in sequence according to the receiving time to obtain multiple frames of 360° panoramic two-dimensional imaging. When the intermediate frequency echo signal received at the current moment is imaged and processed, the coordinate system at the current moment is also used to perform image registration on the 360° panoramic two-dimensional imaging at the previous moment to obtain a high-resolution panoramic image.

[0013] In one embodiment, the intermediate frequency echo signal is related to a polar coordinate system constructed between a target point within a detection range of a rotating scanning synthetic aperture radar at a current moment and a rotation axis of a radar rotary arm.

[0014] In one embodiment, the one-dimensional distance image is processed to obtain a one-dimensional azimuth image using the following formula:

[0015]

[0016] In the above formula, S RC (n,t a ) represents the corresponding one-dimensional distance image, Indicates the moment when the radar beam is facing the target point. The beam width is θ B The time that the antenna continues to illuminate the target point, t a It represents the time to obtain the intermediate frequency echo signal, and τ represents the round-trip transmission delay of the electromagnetic wave from the sky, after it irradiates the target, and finally is received.

[0017] In one embodiment, when performing one-dimensional azimuth imaging, the time when the radar beam is facing the target point is determined. Solve the following transcendental equation:

[0018]

[0019] In the above formula, v represents the speed of the unmanned vehicle, L represents the length of the rotating arm of the rotating scanning synthetic aperture radar, and θ p Represents the angle of the target point in polar coordinates.

[0020] In one embodiment, the step of performing image registration on the 360° panoramic two-dimensional imaging at the previous moment using the coordinate system at the current moment to obtain a high-resolution panoramic image includes:

[0021] Obtaining the angular deviation of the movement direction of one circle of scanning of the rotary scanning synthetic aperture radar at the previous moment relative to the movement direction of one circle of scanning at the current moment, and the average movement speed of one circle of scanning at the previous moment;

[0022] Convert the polar coordinate system in the 360° panoramic two-dimensional imaging at the previous moment into a rectangular coordinate system;

[0023] Calculate the coordinate value of the registered image in the rectangular coordinate system according to the angle deviation, the average value of the movement speed and the time for the rotary scanning synthetic aperture radar to scan one circle;

[0024] The coordinate values ​​in the registered rectangular coordinate system are converted into the polar coordinate system to obtain a registered high-resolution panoramic image.

[0025] In one embodiment, when the length between the front end of the rotating scanning synthetic aperture radar and the rotation axis is shortened, the angular interval between adjacent pixels of the high-resolution panoramic image should satisfy:

[0026]

[0027] In the above formula, It is expressed as the length between the front end of the radar and the rotation axis. It is the angular interval between adjacent pixels of the high-resolution panoramic image after adjustment. L0 represents the reference length between the front end of the radar and the rotation axis. L now It indicates the length between the front end of the radar and the rotation axis after adjustment. It indicates the angular interval between adjacent pixels of the high-resolution panoramic image when the length between the front end of the radar and the rotation axis is taken as the reference length.

[0028] In one embodiment, when the length between the front end of the radar and the rotation axis is the reference length, the angular interval between adjacent pixels of the high-resolution panoramic image should satisfy:

[0029]

[0030] In the above formula, λ represents the electromagnetic wave length of the radar system's operating center frequency, θ B Indicates the radar beam width.

[0031] A sensing radar system comprises: a radar rotating support, a communication unit, a signal processing device and a radar front end, wherein the radar rotating support comprises: a base and a rotating arm;

[0032] A rotating motor and a communication unit are installed inside the base;

[0033] The rotary arm is fixed to the base through a conductive slip ring, the radar front end is installed at one end of the rotary arm along the length direction and away from the base, and the signal processing device is installed at the other end, and the rotary arm rotates under the drive of the rotary motor;

[0034] The signal processing device and the rotating motor receive a scanning command and a rotation command sent by the drone system respectively through the communication unit;

[0035] The rotary motor controls the rotary arm to drive the radar front end to rotate according to the rotation command;

[0036] The signal processing device controls the radar front end to scan around the unmanned vehicle according to the scanning command, and the radar front end sends the radar echo signal received after scanning to the signal processing device;

[0037] The signal processing device processes the radar echo signal according to the above-mentioned perception radar imaging method applicable to unmanned vehicles to obtain a high-resolution panoramic image.

[0038] In one embodiment, the length of the spiral arm is adjustable.

[0039] In one embodiment, the sensing radar system further includes a radome that encloses the radar rotating support.

[0040] A computer device comprises a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the following steps are implemented:

[0041] Acquire an intermediate frequency echo signal, where the intermediate frequency echo signal is a radar echo signal received by a rotating scanning synthetic aperture radar disposed on the unmanned vehicle after detecting a 360° range around the unmanned vehicle while the unmanned vehicle is moving;

[0042] Performing an inverse Fourier transform on the intermediate frequency echo signal to obtain a one-dimensional range image, then processing the one-dimensional range image to obtain a one-dimensional azimuth image, and obtaining a frame of 360° panoramic two-dimensional imaging based on the one-dimensional range image and the one-dimensional azimuth image;

[0043] The intermediate frequency echo signal is imaged and processed in sequence according to the receiving time to obtain multiple frames of 360° panoramic two-dimensional imaging. When the intermediate frequency echo signal received at the current moment is imaged and processed, the coordinate system at the current moment is also used to perform image registration on the 360° panoramic two-dimensional imaging at the previous moment to obtain a high-resolution panoramic image.

[0044] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the following steps:

[0045] Acquire an intermediate frequency echo signal, where the intermediate frequency echo signal is a radar echo signal received by a rotating scanning synthetic aperture radar disposed on the unmanned vehicle after detecting a 360° range around the unmanned vehicle while the unmanned vehicle is moving;

[0046] Performing an inverse Fourier transform on the intermediate frequency echo signal to obtain a one-dimensional range image, then processing the one-dimensional range image to obtain a one-dimensional azimuth image, and obtaining a frame of 360° panoramic two-dimensional imaging based on the one-dimensional range image and the one-dimensional azimuth image;

[0047] The intermediate frequency echo signal is imaged and processed in sequence according to the receiving time to obtain multiple frames of 360° panoramic two-dimensional imaging. When the intermediate frequency echo signal received at the current moment is imaged and processed, the coordinate system at the current moment is also used to perform image registration on the 360° panoramic two-dimensional imaging at the previous moment to obtain a high-resolution panoramic image.

[0048] The above perception radar imaging method and perception radar system applicable to unmanned vehicles, through the rotating scanning synthetic aperture radar set on the unmanned vehicle, detects the 360° range around the unmanned vehicle while the unmanned vehicle is moving, and obtains the intermediate frequency echo signal, and performs one-dimensional distance imaging and one-dimensional direction imaging on the intermediate frequency echo signal to obtain a 360° panoramic two-dimensional imaging, and then uses the coordinate system of the current moment to perform image registration on the 360° panoramic two-dimensional imaging obtained at the previous moment to obtain a high-resolution panoramic image. In this method, an imaging method with a synthetic aperture in the shape of a long cycloid is proposed, so that when performing panoramic imaging, only one radar is needed, and the resolution of the panoramic image does not change with the azimuth. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 A schematic diagram of a flow chart of a perception radar imaging method applicable to an unmanned vehicle in one embodiment;

[0050] Figure 2 A schematic diagram of the observation geometry of a rotating synthetic aperture radar in one embodiment;

[0051] Figure 3 It is a structural diagram of the perception radar system;

[0052] Figure 4 is a structural block diagram of a radar signal sensing imaging device in one embodiment;

[0053] Figure 5 FIG. 4 is a diagram showing the internal structure of a computer device in one embodiment. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0055] like Figure 1 As shown, a perception radar imaging method suitable for unmanned vehicles is provided, comprising the following steps:

[0056] Step S100, obtaining an intermediate frequency echo signal, which is a radar echo signal received by a rotating scanning synthetic aperture radar installed on the unmanned vehicle after detecting a 360° range around the unmanned vehicle while the unmanned vehicle is moving;

[0057] Step S110, performing inverse Fourier transform on the intermediate frequency echo signal to obtain a one-dimensional range image, then processing the one-dimensional range image to obtain a one-dimensional azimuth image, and obtaining a frame of 360° panoramic two-dimensional imaging based on the one-dimensional range image and the one-dimensional azimuth image;

[0058] Step S120, after imaging processing is performed on the intermediate frequency echo signal in sequence according to the receiving time, multiple frames of 360° panoramic two-dimensional imaging are obtained. When imaging processing is performed on the intermediate frequency echo signal received at the current moment, the coordinate system at the current moment is also used to perform image registration on the 360° panoramic two-dimensional imaging at the previous moment to obtain a high-resolution panoramic image.

[0059] In this embodiment, in order to achieve 360° panoramic imaging in the prior art, multiple radars need to be installed on a single vehicle. A panoramic image acquisition method that only needs to use one rotating scanning synthetic aperture radar is proposed, and the unmanned vehicle is always in motion while the radar is scanning the surroundings of the vehicle, so that more image information can be acquired in a shorter time.

[0060] Furthermore, the intermediate frequency echo signal is related to the polar coordinate system constructed by the target point within the detection range of the rotating scanning synthetic aperture radar at the current moment and the rotation axis of the radar arm.

[0061] Specifically, when using the polar coordinate system, a plane rectangular coordinate system is established with the rotation axis of the spiral arm as the origin. The y-axis of the coordinate system is the forward direction of the unmanned vehicle, and the x-axis and y-axis of the coordinate system form a right-handed spiral coordinate system, such as Figure 2 As shown. Let the effective length of the spiral arm be L and the beam width of the radar antenna be θ B , the arm rotates counterclockwise at a constant speed, with an angular velocity of ω (° / s), and the vehicle moves forward at a constant speed of v (m / s). Assuming that at the start time, the x-axis of the arm coincides with the positive direction, the angular interval of the rotation scan is Δθ. There is a target P in the scene, whose coordinates are (r p cosθ p ,r p sinθ p ), r p and θ p are the polar coordinate distance and angle of the target respectively.

[0062] from Figure 2 As can be seen from the figure, when the unmanned vehicle moves forward, within a complete rotation cycle (360°), the synthetic aperture of the radar will no longer be a closed circle ( Figure 2 The radar antenna position is the slow time t a The specific expression of the function is: At (t a )=Lcos(ωt a );y At (t a )=Lcos(ωt a )+vt a .

[0063] When the speed v = 0, the rotating synthetic aperture is a conventional circular aperture (such as Figure 2 Assume that the broadband signal transmitted by the radar is a linear frequency modulation (LFM) signal, and the radar uses de-FM reception to reduce system cost. The expression of the LFM signal transmitted by the radar is:

[0064]

[0065] In formula (1), t is the fast sampling time within the pulse, f0 is the starting frequency, T p is the LFM signal sweep period, K f is the frequency modulation slope, j is an imaginary unit, and A is the amplitude of the transmitted signal, which has little effect on the deformation estimation and is omitted in the subsequent expressions. The radar received echo is the transmitted signal after delay and attenuation. r (t) = s t (t-τ), where τ represents the round-trip transmission delay of the electromagnetic wave from the sky, irradiation to the target P, and finally reception, specifically:

[0066]

[0067] Unmanned vehicle environment perception radar usually adopts a de-FM receiving system to reduce the requirements for AD acquisition, that is, the received echo is multiplied by the transmitted waveform and then low-pass filtered. a , the intermediate frequency echo signal obtained by using the FM receiving system is:

[0068]

[0069] In formula (3), θ(t a ) is related to the arm speed and the forward speed of the unmanned vehicle, and the specific value is:

[0070]

[0071] Therefore, the present application proposes a SAR imaging algorithm for the radar synthetic aperture presenting a long cycloid.

[0072] In step S100, the intermediate frequency echo signal is a multi-circle radar echo signal obtained by the rotating scanning synthetic aperture radar when the unmanned vehicle is moving. The intermediate frequency echo signal corresponding to each circle can obtain a frame of panoramic image. The next step is to process each circle of the intermediate frequency echo signal.

[0073] Specifically, in step S110, the intermediate frequency echo signal is first subjected to an inverse Fourier transform to obtain a one-dimensional range image. Pulse compression can be achieved through an inverse Fourier transform (IFFT) to obtain a high-resolution one-dimensional range image, which is expressed as:

[0074]

[0075] In formula (5), N FFT Indicates the length of the IFFT transform, f s It represents the sampling frequency of the radar echo simulation signal in the fast time domain, n represents the data subscript of the one-dimensional range image, and the target point in the scene is n=round(N FFT K f τ(t a ) / f s ) appears as a wave peak at the subscript position.

[0076] Next, the one-dimensional range image is processed to obtain a one-dimensional azimuth image. Since the PARSAR aperture is not a straight line or an ideal circle, the conventional frequency domain imaging algorithm cannot achieve effective focusing. In this application, based on the time domain back-projection algorithm and according to the characteristics of the long cycloid trajectory, a new type of PCSARIA processing is designed, specifically:

[0077]

[0078] In formula (6), S RC (n,t a ) represents the corresponding one-dimensional distance image, Indicates the moment when the radar beam is facing the target point. The beam width is θ B The time that the antenna continues to illuminate the target point, t a It represents the time to obtain the intermediate frequency echo signal, and τ represents the round-trip transmission delay of the electromagnetic wave from the sky, after it irradiates the target, and finally is received.

[0079] When performing one-dimensional azimuth imaging, determine the moment when the radar beam is facing the target point Solve the following transcendental equation:

[0080]

[0081] In formula (7), v represents the speed of the unmanned vehicle, L represents the length of the rotating arm of the rotating scanning synthetic aperture radar, and θ p Represents the angle of the target point in polar coordinates.

[0082] When solving formula (7), an iterative method can be used to numerically solve it. The initial value of the iteration is the time value assuming that the forward speed of the unmanned vehicle v = 0, that is:

[0083] In this embodiment, since the unmanned vehicle is moving during radar scanning, the relative position of the target point and the radar in the current coordinate system will change during each radar scan. Therefore, in order to improve the imaging quality, the coordinates at the current moment are used to match the panoramic image obtained at the previous moment.

[0084] Specifically, as the unmanned vehicle moves forward, the center position corresponding to the long cycloid constantly changes, and the reference origin position and local coordinate axis direction of the panoramic imaging must be adjusted in time, and the panoramic imaging results obtained from historical data are aligned according to the current coordinate system. Under the assumption that the arm rotates rapidly, the unmanned vehicle can be approximately considered to be in piecewise linear motion, that is, the motion speed of the most recent scan is where θ -1 Indicates the angular deviation of the motion direction of the most recent scan relative to the motion direction of the current scan, v -1 It represents the average value of the movement speed of the most recent scanning circle. Both parameters can be measured by the position sensor installed on the chassis of the unmanned vehicle.

[0085] Assume that the time for the radar to rotate and scan one circle is T ω , then the image of the latest scan circle has translation and rotation in the current coordinate system, and the image of the latest circle is calculated as The most recent image after registration Where p and p′ are the image subscript numbers respectively. The registration process includes obtaining the angle deviation of the motion direction of the previous moment's rotational scanning synthetic aperture radar one circle scan relative to the motion direction of the current moment's one circle scan, and the average motion speed of the previous moment's one circle scan; converting the polar coordinate system in the 360° panoramic two-dimensional imaging at the previous moment into a rectangular coordinate system; calculating the coordinate value of the registered image in the rectangular coordinate system according to the angle deviation, the average motion speed and the time of the rotational scanning synthetic aperture radar scanning one circle; converting the coordinate value in the registered rectangular coordinate system into the polar coordinate system to obtain the registered high-resolution panoramic image.

[0086] Specifically, the polar coordinate image is converted into rectangular coordinates, and the calculation formula is as follows:

[0087]

[0088] In formula (8), are the image points before registration The coordinate values ​​on the x-axis and y-axis.

[0089] Next, according to the unmanned vehicle motion parameters and the radar scanning time T ω , calculate the x-axis and y-axis coordinate values ​​of the registered image The calculation formula is:

[0090]

[0091] Recently, the rotated rectangular coordinates are transformed into polar coordinates, and the calculation formula is:

[0092]

[0093] After registration, both images use the current coordinate system, so that more complex sequence image processing can be carried out, such as: extracting information about moving targets in the scene.

[0094] In this embodiment, when scanning is performed, when the length between the front end of the rotary scanning synthetic aperture radar and the rotation axis can be changed (that is, when the length of the radar rotary arm can be adjusted, refer to Figure 3 ), if the arm is shortened, on the one hand, the moment of inertia of the system can be reduced, thereby increasing the rotation speed of the turntable; on the other hand, it will cause a decrease in imaging resolution, and the signal processor can reduce the pixel density without causing image distortion, thereby increasing the imaging speed. Combining these two factors, the time required for panoramic scanning can be reduced and the detection efficiency can be improved. If the reference arm length of the radar system is L0, this parameter is generally designed to be half of the maximum arm length L, then under the reference arm length, the angular interval between adjacent pixels of the image is The conditions that should be met are:

[0095]

[0096] In formula (11), It is expressed as the angular interval between adjacent pixels of the high-resolution panoramic image after adjusting the spiral arm length. L0 represents the reference length of the spiral arm, which is half of the maximum arm length. now Indicates the adjusted arm length, Indicates the angular interval between adjacent pixels of a high-resolution panoramic image when the spiral arm is the reference length.

[0097] When the spiral arm is the reference length, the angular interval between adjacent pixels of the high-resolution panoramic image should satisfy:

[0098]

[0099] In formula (12), λ represents the electromagnetic wave length of the radar system's operating center frequency, θ B Indicates the radar beam width.

[0100] On the contrary, if the arm is lengthened, although the time required for panoramic scanning will increase, the imaging resolution will be better, thereby improving detection performance.

[0101] like Figure 3As shown, the present application also provides a perception radar system suitable for the above-mentioned perception radar imaging processing method, including: a radar rotating support 1, a signal processing device 2, a radar front end 3 and a communication unit 4, wherein the radar rotating support 1 includes: a base 11 and a swing arm 12. Among them, a rotating motor and a communication unit 4 are installed inside the base 11. The swing arm is fixed to the base 11 through a conductive slip ring 5, and the radar front end 3 is installed at one end of the swing arm 12 away from the base 11 along the length direction, and the signal processing device 2 is installed at the other end, and the swing arm 12 rotates under the drive of the rotating motor. The signal processing device 2 and the rotating motor receive the scanning command and the rotation command sent by the unmanned aerial vehicle system through the communication unit 4 respectively, and the rotating motor controls the swing arm 12 to drive the radar front end to rotate according to the rotation command. The signal processing device 2 controls the radar front end 3 to scan around the unmanned vehicle according to the scanning command, and the radar front end 3 sends the radar echo signal received after scanning to the signal processing device 2. The signal processing device 2 processes the radar echo signal according to the above-mentioned perception radar imaging method suitable for unmanned vehicles to obtain a high-resolution panoramic image.

[0102] In this embodiment, according to the requirements of the application scenario, the length of the swing arm 12 can be adjusted through command control. By lengthening the swing arm 12, the resolution of the perception radar system can be improved. By shortening the swing arm, the rotational inertia of the perception radar system can be reduced, thereby shortening the time required for panoramic scanning.

[0103] In this embodiment, the communication unit 4 is a communication interface disposed on the outer wall of the base, and the communication interface is also a power interface.

[0104] Specifically, the radar front end 3 is located at the outer end of the rotary arm 12, and a larger synthetic aperture can be formed under the rotation of the rotary arm. The radar front end 3 realizes functions such as broadband signal generation, up-conversion, power amplification, transmission, echo reception, down-conversion and AD acquisition. It is usually required that the volume and weight of the radar front end 3 are as small as possible to reduce the moment of inertia when the rotary arm rotates at high speed. In one embodiment, the radar front end 3 adopts a single-chip radar or a single-board radar.

[0105] Specifically, the signal processing device 2 is located at the other end of the swing arm 12, and is used to balance the rotational inertia of the radar front end. The signal processing device 2 is connected to the radar front end 3 through a communication bus (such as USB, Ethernet), realizes the configuration of the radar parameters (such as operating frequency, transmission power) of the radar front end 3, and receives the radar echo collected by the radar front end 3 and performs imaging processing. The signal processing device 2 communicates with the unmanned vehicle system through the communication unit 4, receives and executes the instructions of the unmanned vehicle system, and returns the radar image and target measurement parameters to the unmanned vehicle system.

[0106] Specifically, the arm 12 is adjusted under the command of the unmanned vehicle system, and the position of the rotating axis on the arm 12 is adjusted by the motor on the arm 12 to change the length of the arm, so that the panoramic imaging angular resolution and image refresh frequency of the radar system are adjusted according to application requirements.

[0107] Specifically, the conductive slip ring 5 is used to provide a reliable electrical connection between the fixed base 11 and the moving arm 12, to provide an external power supply to the signal processing device 2 and the radar front end 3, and to provide a physical communication link between the signal processing device 2 and the communication unit 4.

[0108] Specifically, the rotary motor (not shown in the figure) is fixed inside the base 11, has a large rotation torque, and drives the rotary arm to rotate quickly. The rotary motor can be configured through the communication unit 4 according to application requirements to achieve rotation at different speeds.

[0109] In this embodiment, the sensing radar system further includes a radome 6 that encloses the radar rotating support 1 to protect the entire system from interference from the external environment.

[0110] In the above-mentioned perception radar imaging method suitable for unmanned vehicles, by installing a rotating scanning synthetic aperture radar on the roof of the unmanned vehicle, using the swing arm to form an arc-shaped synthetic aperture, the arc (unmanned vehicle) is detected, and the effective viewing angle is 360°. For each detection direction, the radar has the same synthetic aperture accumulation angle, so the azimuth resolution is consistent, and there is no problem of resolution space variation. The radar detection capability can be flexibly configured by adjusting the swing arm length, which can adapt to a variety of unmanned driving application requirements. In this application, the swing arm length can be adjusted by command control, the system resolution can be improved by increasing the swing arm, and the system's rotational inertia can be reduced by shortening the swing arm, shortening the time required for panoramic scanning. This application adopts a mature mechanical and electronic structure, which is low in cost and suitable for large-scale application and promotion. The hardware structure of this application consists of a mechanical swing arm and a low-power radar. The swing arm can be implemented by a stepping turntable. There are many shelf products for low-power radars, such as 24GHz radars, MMW radars, etc., so the overall cost of the system is low, which is suitable for large-scale promotion and application in the fields of unmanned driving and intelligent transportation.

[0111] It should be understood that although Figure 1 The steps in the flowchart are shown in sequence as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, Figure 1At least part of the steps may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least part of the sub-steps or stages of other steps.

[0112] In one embodiment, Figure 4 As shown, a perception radar imaging device suitable for an unmanned vehicle is provided, comprising: an echo signal acquisition module 400, a panoramic imaging module 410 and an image matching module 420, wherein:

[0113] The echo signal acquisition module 400 is used to acquire an intermediate frequency echo signal, where the intermediate frequency echo signal is a radar echo signal received by a rotating scanning synthetic aperture radar arranged on the unmanned vehicle after detecting a 360° range around the unmanned vehicle while the unmanned vehicle is moving;

[0114] The panoramic imaging module 410 is used to perform inverse Fourier transform on the intermediate frequency echo signal to obtain a one-dimensional range image, and then process the one-dimensional range image to obtain a one-dimensional azimuth image, and obtain a frame of 360° panoramic two-dimensional imaging according to the one-dimensional range image and the one-dimensional azimuth image;

[0115] The image matching module 420 is used to perform imaging processing on the intermediate frequency echo signal in sequence according to the receiving time to obtain multiple frames of 360° panoramic two-dimensional imaging. When imaging the intermediate frequency echo signal received at the current moment, the coordinate system at the current moment is also used to perform image registration on the 360° panoramic two-dimensional imaging at the previous moment to obtain a high-resolution panoramic image.

[0116] For the specific limitations of the perception radar imaging device suitable for unmanned vehicles, please refer to the limitations of the perception radar imaging method suitable for unmanned vehicles mentioned above, which will not be repeated here. Each module in the above-mentioned perception radar imaging device suitable for unmanned vehicles can be implemented in whole or in part through software, hardware and a combination thereof. The above-mentioned modules can be embedded in or independent of the processor in the computer device in the form of hardware, or can be stored in the memory of the computer device in the form of software, so that the processor can call and execute the operations corresponding to the above modules.

[0117] In one embodiment, a computer device is provided. The computer device may be a terminal, and its internal structure diagram may be as follows: Figure 5As shown. The computer device includes a processor, a memory, a network interface, a display screen and an input device connected through a system bus. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The network interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, a perception radar imaging method suitable for an unmanned vehicle is implemented. The display screen of the computer device can be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer device can be a touch layer covering the display screen, or a button, trackball or touchpad set on the computer device housing, or an external keyboard, touchpad or mouse, etc.

[0118] Those skilled in the art will understand that Figure 5 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0119] In one embodiment, a computer device is provided, including a memory and a processor, wherein a computer program is stored in the memory, and when the processor executes the computer program, the following steps are implemented:

[0120] Acquire an intermediate frequency echo signal, where the intermediate frequency echo signal is a radar echo signal received by a rotating scanning synthetic aperture radar disposed on the unmanned vehicle after detecting a 360° range around the unmanned vehicle while the unmanned vehicle is moving;

[0121] Performing an inverse Fourier transform on the intermediate frequency echo signal to obtain a one-dimensional range image, then processing the one-dimensional range image to obtain a one-dimensional azimuth image, and obtaining a frame of 360° panoramic two-dimensional imaging based on the one-dimensional range image and the one-dimensional azimuth image;

[0122] The intermediate frequency echo signal is imaged and processed in sequence according to the receiving time to obtain multiple frames of 360° panoramic two-dimensional imaging. When the intermediate frequency echo signal received at the current moment is imaged and processed, the coordinate system at the current moment is also used to perform image registration on the 360° panoramic two-dimensional imaging at the previous moment to obtain a high-resolution panoramic image.

[0123] In one embodiment, a computer readable storage medium is provided, on which a computer program is stored, and when the computer program is executed by a processor, the following steps are implemented:

[0124] Acquire an intermediate frequency echo signal, where the intermediate frequency echo signal is a radar echo signal received by a rotating scanning synthetic aperture radar disposed on the unmanned vehicle after detecting a 360° range around the unmanned vehicle while the unmanned vehicle is moving;

[0125] Performing an inverse Fourier transform on the intermediate frequency echo signal to obtain a one-dimensional range image, then processing the one-dimensional range image to obtain a one-dimensional azimuth image, and obtaining a frame of 360° panoramic two-dimensional imaging based on the one-dimensional range image and the one-dimensional azimuth image;

[0126] The intermediate frequency echo signal is imaged and processed in sequence according to the receiving time to obtain multiple frames of 360° panoramic two-dimensional imaging. When the intermediate frequency echo signal received at the current moment is imaged and processed, the coordinate system at the current moment is also used to perform image registration on the 360° panoramic two-dimensional imaging at the previous moment to obtain a high-resolution panoramic image.

[0127] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM is available in many forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

[0128] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0129] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A perception radar imaging method suitable for unmanned vehicles, characterized in that: The method comprises: Acquire an intermediate frequency echo signal, wherein the intermediate frequency echo signal is a radar echo signal received by a rotating scanning synthetic aperture radar disposed on the unmanned vehicle after detecting a 360° range around the unmanned vehicle while the unmanned vehicle is moving, wherein the intermediate frequency echo signal is related to a polar coordinate system constructed by a target point within the detection range of the rotating scanning synthetic aperture radar at a current moment and a rotation axis of the radar rotary arm; The intermediate frequency echo signal is subjected to inverse Fourier transform to obtain a one-dimensional range image, and then the one-dimensional range image is processed to obtain a one-dimensional azimuth image, and a frame of 360° panoramic two-dimensional imaging is obtained according to the one-dimensional range image and the one-dimensional directional image, wherein the one-dimensional azimuth image is obtained by processing the one-dimensional range image using the following formula: In the above formula, S RC (n,t a ) represents the corresponding one-dimensional distance image, Indicates the moment when the radar beam is facing the target point. The beam width is θ B The time that the antenna continues to illuminate the target point, t a It indicates the time to obtain the intermediate frequency echo signal, τ indicates the two-way transmission delay of the electromagnetic wave from the sky to the target and finally received. At the same time, when performing one-dimensional azimuth imaging, it determines the moment when the radar beam is facing the target point. Solve the following transcendental equation: In the above formula, v represents the speed of the unmanned vehicle, L represents the length of the rotating arm of the rotating scanning synthetic aperture radar, and θ p Represents the angle of the target point in polar coordinates; The intermediate frequency echo signal is imaged and processed in sequence according to the receiving time to obtain multiple frames of 360° panoramic two-dimensional imaging. When the intermediate frequency echo signal received at the current moment is imaged and processed, the coordinate system at the current moment is also used to perform image registration on the 360° panoramic two-dimensional imaging at the previous moment to obtain a high-resolution panoramic image.

2. The perception radar imaging method according to claim 1, characterized in that: The method of using the coordinate system at the current moment to perform image registration on the 360° panoramic two-dimensional imaging at the previous moment to obtain a high-resolution panoramic image includes: Obtaining the angular deviation of the movement direction of one circle of scanning of the rotary scanning synthetic aperture radar at the previous moment relative to the movement direction of one circle of scanning at the current moment, and the average movement speed of one circle of scanning at the previous moment; Convert the polar coordinate system in the 360° panoramic two-dimensional imaging at the previous moment into a rectangular coordinate system; Calculate the coordinate value of the registered image in the rectangular coordinate system according to the angle deviation, the average value of the movement speed and the time for the rotary scanning synthetic aperture radar to scan one circle; The coordinate values ​​in the registered rectangular coordinate system are converted into the polar coordinate system to obtain a registered high-resolution panoramic image.

3. The perception radar imaging method according to claim 1 or 2, characterized in that: When the length between the front end of the rotating scanning synthetic aperture radar and the rotation axis is shortened, the angular interval between adjacent pixels of the high-resolution panoramic image should satisfy: In the above formula, It is expressed as the length between the front end of the radar and the rotation axis. It is the angular interval between adjacent pixels of the high-resolution panoramic image after adjustment. L0 represents the reference length between the front end of the radar and the rotation axis. L now It indicates the length between the front end of the radar and the rotation axis after adjustment. It indicates the angular interval between adjacent pixels of the high-resolution panoramic image when the length between the front end of the radar and the rotation axis is taken as the reference length.

4. The perception radar imaging method according to claim 3, characterized in that: When the length between the front end of the radar and the rotation axis is the reference length, the angular interval between adjacent pixels of the high-resolution panoramic image should satisfy: In the above formula, λ represents the electromagnetic wave length of the radar system's operating center frequency, θ B Indicates the radar beam width.

5. A perception radar system, characterized in that: include: A radar rotating support, a communication unit, a signal processing device and a radar front end, wherein the radar rotating support comprises: a base and a rotating arm; A rotating motor and a communication unit are installed inside the base; The rotary arm is fixed to the base through a conductive slip ring, the radar front end is installed at one end of the rotary arm along the length direction and away from the base, and the signal processing device is installed at the other end, and the rotary arm rotates under the drive of the rotary motor; The signal processing device and the rotating motor receive a scanning command and a rotation command sent by the drone system respectively through the communication unit; The rotary motor controls the rotary arm to drive the radar front end to rotate according to the rotation command; The signal processing device controls the radar front end to scan around the unmanned vehicle according to the scanning command, and the radar front end sends the radar echo signal received after scanning to the signal processing device; The signal processing device processes the radar echo signal according to the perception radar imaging method applicable to unmanned vehicles according to any one of claims 3-4 to obtain a high-resolution panoramic image.

6. The perception radar system according to claim 5, characterized in that: The length of the rotary arm is adjustable.

7. The perception radar system according to claim 6, characterized in that: The sensing radar system also includes a radome that encloses the radar rotating support.

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