Radar signal processing device, radar system, radar signal processing method, and radar signal processing program

Abstract

This radar signal processing device comprises: a target detection unit (121) that receives a plurality of radar signals detected by a radar sensor and detects, from the received radar signals, a first velocity and a first angle from a first propagation path constituting a reference, and a second velocity and a second angle from a second propagation path which is different from the first propagation path; an identical target determination unit (122) that determines whether first data including the detected first velocity and the detected first angle from the first propagation path and second data including the detected second angle and the detected second velocity from the second propagation path are data for an identical target; and a velocity vector estimation unit (123) that, in a case where the first data and the second data are determined to be data from an identical target, estimates the movement direction and the velocity of the identical target.

Description

Radar signal processing device, radar system, radar signal processing method, and radar signal processing program

[0001] The present disclosure relates to radar signal processing techniques.

[0002] Patent Document 1 discloses a technology relating to an object position detection device that includes a detection unit that detects a detection angle, which is the angle of the object to be detected relative to the receiving unit, based on radio waves that are emitted from a transmitting unit, reflected by the object to be detected, and incident on a receiving unit; a determination unit that determines whether the radio waves that incident on the receiving unit have been reflected by a road surface; and a calculation unit that, when the determination unit determines that the radio waves have been reflected by the road surface, calculates relative relationship information that indicates the positional relationship of the object to be detected relative to the receiving unit, based on the angle of the receiving unit with respect to the road surface and the detection angle. Patent Document 1 also discloses a technology relating to an object position detection device that includes a detection unit that detects the "velocity of the object to be detected T relative to the receiving unit 112 (hereinafter referred to as the detection velocity v ｄｅｔ ) can be detected” (paragraph 0041 of Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2022-60722

[0004] The technology of Patent Document 1 can detect the position of an object outside the line of sight and can also detect the speed of the object in the line of sight of the radar. However, the technology of Patent Document 1 has a problem in that it cannot detect the speed of the object in directions other than the line of sight of the radar.

[0005] The present disclosure has been made to solve such problems, and aims to provide a radar signal processing technique that can detect the velocity of an object in a direction other than the radar's line of sight.

[0006] One aspect of a radar signal processing device according to an embodiment of the present disclosure includes: a target detection unit that receives a plurality of radar signals detected by a radar sensor and detects, from the received radar signals, a first velocity and a first angle from a first propagation path serving as a reference, and a second velocity and a second angle from a second propagation path different from the first propagation path; a same target determination unit that determines whether first data including the detected first velocity and first angle from the first propagation path and second data including the detected second velocity and second angle from the second propagation path are data about the same target; and a velocity vector estimation unit that, when it is determined that the first data and the second data are data about the same target, estimates a moving direction and a velocity of the same target.

[0007] A radar signal processing device according to an embodiment of the present disclosure can detect the velocity of an object in a direction other than the line of sight of the radar.

[0008] Fig. 1 is a configuration diagram showing a radar signal processing device and a radar system according to embodiment 1. Fig. 2 is an explanatory diagram of a radar system and a target signal according to embodiment 1. Fig. 3 is a diagram showing an example of a hardware configuration of a radar signal processing device. Fig. 4 is a diagram showing an example of a hardware configuration of a radar signal processing device. Fig. 5 is a flowchart showing an outline of an operation executed by the radar signal processing device according to embodiment 1. Fig. 6 is an explanatory diagram of a radar system and a target signal according to embodiment 2.

[0009] Various embodiments of the present disclosure will be described in detail below with reference to the drawings. In the drawings, identical or similar parts are designated by identical or similar reference numerals, and redundant explanations of such parts will be omitted. In addition, in this disclosure, the term "or" is used to mean an inclusive logical OR unless otherwise specified.

[0010] First Embodiment <Configuration> A radar signal processing device and a radar system according to a first embodiment of the present disclosure will be described with reference to Figures 1 and 2. As shown in Figure 1, the radar system 1 includes a radar sensor 11 having an antenna, and a radar signal processing device 12 that performs signal processing on a radar signal detected by the radar sensor 11.

[0011] (Radar Sensor) The radar sensor 11 is a general sensor that performs sensing using electromagnetic waves and is disposed, for example, on a vehicle bumper. The radar sensor 11 performs sensing by, for example, emitting radio waves and receiving reflected waves. As a sensing method, known methods such as an FMCW (frequency modulated continuous wave) method, a Fast-Chirp method, and a pulse Doppler method can be used. The radar sensor 11 outputs a signal of the detected reflected wave as a radar signal to the radar signal processing device 12. When detecting multiple reflected waves due to multipath, the radar sensor 11 outputs multiple radar signals due to multipath to the radar signal processing device 12.

[0012] (Radar Signal Processing Device) The radar signal processing device 12 is a device that performs signal processing on the radar signal output from the radar sensor 11 to determine the velocity of a detected target in any direction. In other words, the radar signal processing device 12 is a device that can not only determine the velocity of a target along the line of sight, as in the prior art, but also determine the velocity along a direction other than the line of sight. Note that velocity is a vector quantity that includes direction and speed. In this disclosure, when emphasizing the meaning of vector, the term "velocity vector" may be used interchangeably with "velocity." To determine the velocity of a detected target in any direction, the radar signal processing device 12 includes a target detection unit 121, a same target determination unit 122, and a velocity vector estimation unit 123, as shown in FIG. 1 . The velocity vector estimation unit 123 includes a target movement direction estimation unit 1231 and a velocity estimation unit 1232. Note that the radar signal processing device 12 also includes a control unit that controls the entire device.

[0013] The target detection unit 121 is a functional unit that receives a plurality of radar signals detected by the radar sensor 11 and detects, from the received radar signals, a first distance, a first velocity, and a first angle from a first propagation path as a reference, and a second distance, a second velocity, and a second angle from a second propagation path different from the first propagation path. The velocity is obtained by differentiating the distance with respect to time.

[0014] (Same target determination unit) The same target determination unit 122 is a functional unit that determines whether first data including a first velocity and a first angle from a first propagation path detected by the target detection unit 121 and second data including a second velocity and a second angle from a second propagation path detected by the target detection unit 121 are data about the same target.

[0015] (Velocity Vector Estimation Unit) The velocity vector estimation unit 123 is a functional unit that estimates the moving direction and velocity of the same target when the same target determination unit 122 determines that the first data and the second data are data about the same target. The velocity vector estimation unit 123 outputs the estimated moving direction and velocity of the same target as a velocity vector. In order to achieve this function, the velocity vector estimation unit 123 includes a target moving direction estimation unit 1231 and a velocity estimation unit 1232.

[0016] (Target Moving Direction Estimation Unit) The target moving direction estimation unit 1231 is a functional unit that estimates the moving direction of the same target from the first speed, the first angle, the second speed, and the second angle.

[0017] (Speed ​​Estimation Unit) The speed estimation unit 1232 is a functional unit that estimates the speed of the same target from the first speed and the moving direction estimated by the target moving direction estimation unit 1231.

[0018] The principles of the functions realized by these functional units will be described in detail below.

[0019] FIG. 2 is an explanatory diagram schematically illustrating the relationship between the radar system 1 according to the first embodiment of the present invention and a target signal, which is a signal reflected from a target. A signal emitted from the radar system 1 shown in FIG. 2 is reflected by a target 22, and the reflected signal reflected by the target 22 is observed by the radar system 1. The reflected signal reflected by the target 22 includes a target signal propagating through a direct propagation path 23 connecting the target 22 and the radar system 1 in a straight line, and a target signal propagating through a propagation path 24 via a fixed object such as a wall. The target signal propagating through the propagation path 23 is detected by the radar system 1 at a velocity v1 and an arrival angle θ1. Similarly, the target signal propagating through the propagation path 24 is detected by the radar system 1 at a velocity v2 and an arrival angle θ2. The target's line-of-sight velocities (the direction of the arrival angle θ1 and the direction of the arrival angle θ2) in the propagation paths 23 and 24 are observed, but the target's true velocity vector v is unknown. 2, for convenience, the target movement direction is defined as θv in the counterclockwise direction with propagation path 23 as the reference, and the angle between propagation path 23 and propagation path 24 at target 22 is defined as Δθ. Any of the multiple propagation paths may be used as the reference, and similar results can be obtained by appropriately setting the target movement direction and the positive or negative sign of the angle depending on the reference used.

[0020] 2, there may be objects or fixed objects other than the target in the environment of the radar system 1, and reflected signals from such objects or fixed objects are present. In this disclosure, the method for estimating the velocity vector v of the target 22 will be described, and therefore, the description of reflected signals from objects or fixed objects other than the target 22 will be omitted.

[0021] When estimating the velocity vectors of two or more targets simultaneously, it is possible to estimate the velocity vectors of the other targets by sequentially applying the same process as that for estimating the velocity vector of the target 22 to one or more other targets. Therefore, the process for estimating the velocity vector of the target 22 will be described below.

[0022] (Hardware Configuration) Next, an example of the hardware configuration of the radar signal processing device 12 will be described with reference to Figures 3A and 3B. Each function of the radar signal processing device 12 is realized by a processing circuit. The processing circuit may be a dedicated processing circuit 100a as shown in Figure 3A, or a processor 100b that executes a program stored in a memory 100c as shown in Figure 3B.

[0023] When the processing circuitry is a dedicated processing circuit 100a, the dedicated processing circuit 100a may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or a combination thereof. The functions of the radar signal processing device 12 may be realized by multiple separate processing circuits, or the functions of the radar signal processing device 12 may be realized together by a single processing circuit.

[0024] When the processing circuitry is the processor 100b as a computer, the functions of the radar signal processing device 12 are realized by software, firmware, or a combination of software and firmware. The software and firmware are written as programs and stored in the memory 100c. The processor 100b realizes the functions of the radar signal processing device 12 by reading and executing the programs stored in the memory 100c. Here, examples of memory 100c include non-volatile or volatile semiconductor memories such as RAM (random access memory), ROM (read-only memory), flash memory, EPROM (erasable programmable read-only memory), and EEPROM (electrically erasable programmable read-only memory), as well as magnetic disks, flexible disks, optical disks, compact disks, minidisks, and DVDs.

[0025] It is also possible to implement some of the functions of the radar signal processing device 12 using dedicated hardware, and other functions using software or firmware. In this way, the processing circuit can implement the functions of the radar signal processing device 12 using hardware, software, firmware, or a combination of these.

[0026] <Operation> (Outline of Operation) Next, an outline of the operation executed by the radar signal processing device 12 will be described with reference to FIG.

[0027] (Step ST31) In step ST31, the target detection unit 121 receives, from the radar sensor 11, a received signal that is transmitted from the radar sensor 11, reflected by a target, and received by the radar sensor 11 as a radar signal, and converts the received radar signal into information about the detection point. That is, the target detection unit 121 acquires a target signal (distance, direction, speed) from the received radar signal. Note that in the present disclosure, the target signal may also be referred to as a detection signal. At this time, one or more detection points other than the target 22 may appear as a detection result. That is, multiple detection signals may be detected. If detection signals related to multiple detection points are detected, the next step ST32 is processed for the detection signals related to all of the detected detection points.

[0028] (Step ST32) In step ST32, the same target determination unit 122 determines, from among the detected multiple detection signals, signals that are related to the same target but have propagated through different propagation paths. For example, the same target determination unit 122 selects a combination of the speed and direction of the detection points that results in the same relative speed. As another example, the same target determination unit 122 may calculate the relative position of the target from the propagation path, and consider detection points whose calculated relative positions match or are located nearby to be the same. In this way, the same target determination unit 122 extracts signals that are related to the same target but have different propagation paths.

[0029] (Step ST33) In step ST33, the target movement direction estimation unit 1231 acquires the target movement direction θv, which is the direction in which the target is moving, using multiple signals determined in step ST32 to be signals from different propagation paths related to the same target. That is, the target movement direction estimation unit 1231 acquires the target movement direction θv from multiple detected velocities v1 and v2 and detected angles θ1 and θ2 for the same target. When different propagation paths from the same target exist, the movement direction of the target can be estimated by using speed and angle information of two or more signals. For simplicity, the case where there are two multipaths will be described. However, even when there are three or more multipaths, the target movement direction θv can be obtained by extracting signals from two multipaths. When there are three or more multipaths and multiple target movement directions θv are obtained, a single value may be determined, for example, by calculating the average value of the obtained target movement directions θv.

[0030] (Step ST34) In step ST34, the speed estimation unit 1232 acquires a target speed v from the detected speed v1 or v2 and the target movement direction θv acquired in step ST34. The target speed v can be calculated from the speed of the propagation path used as a reference when calculating the target movement direction θv and the target movement direction θv. Through the above processing, the speed vector (speed v and movement direction θv) of the target can be obtained by using signals from the same target through different propagation paths.

[0031] (Details of Operation) Next, the details of the operation executed by the radar signal processing device 12 will be described using mathematical expressions.

[0032] First, in the radar signal processing device 12, a received signal is input to the target detection unit 121 at each predetermined observation period, and the target detection unit 121 calculates the relative distance, relative speed, and angle of the detected target. This information is calculated using a typical radar method for calculating relative distance, relative speed, and angle, so a detailed description will be omitted. The information on the detected target is input to the same target determination unit 122. Additional information on each detected target, such as a signal strength value, may also be input to the same target determination unit 122. This processing by the target detection unit 121 corresponds to step ST31 of acquiring the target signal (distance, direction, speed) in FIG. 4 .

[0033] Next, the same target determination unit 122 determines whether the detected target is a signal from the same target that has traveled through different propagation paths. The same target determination process by the same target determination unit 122 can be performed using various methods. For example, 1) a method of selecting multipath signals with the same corrected relative velocity by utilizing the fact that relative velocities obtained from the same target via different propagation paths become the same value when corrected by the detection angle; 2) a method of calculating a relative position from the relative distance and propagation path and selecting multipath signals with the same or close relative positions; 3) a method of selecting multipath signals related to the same target based on signal strength, signal propagation distance, and antenna characteristics; or 4) a combination of the above methods. The method of determining the same target is not limited to the above methods; any method may be used as long as it can determine that the signals are from the same target. For example, an image of the environment may be acquired and the identity of the target may be determined by image processing. Here, as shown in FIG. 2, it is assumed that a relative velocity v1 and angle θ1 are obtained from propagation path 23, and a relative velocity v2 and angle θ2 are obtained from propagation path 24. It should be noted that, as long as it can be determined that the signals are from the same target, the walls or fixed objects in the propagation path 24 in FIG. 2 do not need to be known.

[0034] Next, the target movement direction estimation unit 1231 calculates the movement direction θv of the target from the relative velocity v1, angle θ1, relative velocity v2, and angle θ2. As shown in FIG. 2 , the movement direction θv of the target is defined based on the angle θ1 of the propagation path 23. That is, the movement direction θv of the target is defined as a counterclockwise rotation angle direction with the arrival angle θ1 as the reference line and the detected target 22 located on the reference line as the origin. Also, the angle formed by the propagation path 23 and the propagation path 24 at the target 22 is defined as Δθ. In this case, using the unknown target velocity v, the observed relative velocities v1 and v2 can be expressed as follows: v1 = v cos(θv) v2 = v cos(θv + Δθ) Transforming these equations gives us v = v1 / cos(θv) v = v2 / cos(θv+Δθ) and v1 / cos(θv) = v2 / cos(θv+Δθ). Here, according to the addition theorem of trigonometric functions, cos(θv+Δθ) = cos(θv) · cos(Δθ) - sin(θv) · sin(Δθ), so we get v1 · cos(θv) · cos(Δθ) - v1 · sin(θv) · sin(Δθ) = v2 · cos(θv). Since velocities perpendicular to the radar's line of sight are not observed, cos(θv)≠0. Therefore, by dividing both sides of the equation directly above by cos(θv) and continuing to rearrange the equation, we obtain v1·cos(Δθ)-v1·sin(θv)·sin(Δθ) / cos(θv) = v2 v1·tan(θv)·sin(Δθ)=v1·cos(Δθ)-v2 Here, since propagation path 23 and propagation path 24 are different, the angle between the propagation paths Δθ≠0, and since the range of Δθ is 0<Δθ<π, sin(Δθ)≠0. Note that Δθ=|θ1-θ2|. Therefore, the equation can be rearranged as follows: tan(θv)=1 / tan(Δθ)-v2 / (v1·sin(Δθ)). From this equation, the desired moving direction θv can be obtained as follows: θv=π / 2−Δθ−arctan(v2 / (v1·sin(Δθ))) (1)

[0035] Note that even when the reference propagation path is changed and v1=v·cos(θv) and v2=v·cos(θv-Δθ) are defined, the target moving direction θv can be obtained by similarly transforming the equation as follows: θv=π / 2+Δθ-arctan(v2 / (v1·sin(Δθ))) ...equation (2) The only difference between equation (1) and equation (2) is the different standard of definition, and the moving direction of the target for any geometry obtained from the target moving direction θv for the reference propagation path is the same.

[0036] Next, the speed v of the target is estimated by the speed estimation unit 1232. From the relationship between the target movement direction θv obtained by the target movement direction estimation unit 1231 and the observed target speed v1, the target speed v can be calculated as v = v1 / cos(θv). As a result, the true speed vector of the target can be estimated from the information observed by the radar sensor 11.

[0037] As described above, the radar signal processing device 12 according to the first embodiment can obtain the velocity vector (velocity v and moving direction θv) of a target by using the information on the velocity and angle of the same target observed by the radar sensor 11 via different propagation paths. Furthermore, by adding the processing of the radar signal processing device 12 to a conventional radar system, it is possible to add functions.

[0038] The velocity (velocity vector) including the direction of movement of a target is important as information for safety judgment in, for example, safe driving assistance or autonomous driving of an automobile or a personal mobility vehicle (PMV). Conventional techniques include a method of obtaining the velocity (velocity vector) including the direction of movement of a target by tracking processing from time-series acquired changes in the target's position and relative velocity. However, estimation from time-series information requires a certain observation time, and tracking processing estimates based on relative changes, which makes it difficult to estimate velocity instantaneously. According to the radar signal processing device 12 disclosed herein, the velocity vector can be obtained if there is an observation time long enough to obtain the target's relative velocity, thereby achieving the effect of enabling quick measurement with a shorter observation time than tracking processing.

[0039] Embodiment 2. The above-described embodiment 1 is an embodiment that makes it possible to estimate the velocity vector of a target by utilizing information on the velocity and angle observed via different propagation paths from the same target. Next, embodiment 2 will be described, which is an embodiment that estimates the velocity vector of a target when all the different propagation paths are outside the line of sight.

[0040] 5 is an explanatory diagram schematically illustrating the relationship between the radar system 1 and a target signal according to embodiment 2. In Fig. 5, a radio wave transmitted from the radar system 1 is reflected by a target 42, and the signal reflected by the target 42 is received by the radar system 1 from outside the line of sight via different propagation paths 43 and 44. In embodiment 2, the processes from acquiring the target signal (step ST31) to determining whether the target signals are identical (step ST32) are the same as those in embodiment 1.

[0041] Even when the target 42 is outside the line of sight, as shown in Fig. 5, by defining the angle (= the moving direction θv of the target) of the velocity vector of the target 42 with respect to the propagation path 43 and taking the angle Δθ between the propagation path 43 and the propagation path 44 at the position of the target 42, the moving direction θv of the target 42 and the velocity v of the target 42 can be obtained using the same procedure as in embodiment 1. At this time, it should be noted that when determining the angle Δθ between different propagation paths, the angle of incidence on the target 42 differs depending on the propagation path, and therefore the relationship may not be a simple one of the difference between the estimated angles θ1 and θ2.

[0042] As described above, even if a target is outside the line of sight, when the same target is observed on different propagation paths, the target's velocity vector (velocity v and moving direction θv) can be obtained from the observed velocity and angle information.Furthermore, by adding similar processing to a conventional radar system, it is possible to add functionality.

[0043] Furthermore, in the above embodiment, the propagation path for a signal transmitted from a radar system, reflected by a target, and received by the radar system is the same for both transmission and reception. However, in the case of multipath, the transmission and reception paths may be different. When the transmission and reception paths are different, the range, velocity, and angle of the target observed by the radar system contain a mixture of information from the different transmission and reception paths. In this case, the correct information for the range or angle can be estimated using a technique for estimating the angle for each of the transmission and reception. For example, in a MIMO radar, the correct information can be estimated using a technique such as beamforming using steering vectors for each of the transmission and reception. Furthermore, the target's velocity vector can be calculated by calculating the angle between the composite vector of the transmission and reception propagation paths and the target's velocity vector, as in the above embodiment.

[0044] It is possible to combine the embodiments, and to modify or omit each embodiment as appropriate.

[0045] The radar signal processing device of the present disclosure can be mounted on, for example, an automobile or a PMV and used as a device constituting a safe driving support system or an autonomous driving system.

[0046] REFERENCE SIGNS LIST 1 radar system, 11 radar sensor, 12 radar signal processing device, 100a processing circuit, 100b processor, 100c memory, 121 target detection unit, 122 same target determination unit, 123 velocity vector estimation unit, 1231 target movement direction estimation unit, 1232 velocity estimation unit.

Claims

1. A radar signal processing device comprising: a target detection unit that receives a plurality of radar signals detected by a radar sensor and detects, from the received radar signals, a first velocity and a first angle from a first propagation path used as a reference, and a second velocity and a second angle from a second propagation path different from the first propagation path; a same target determination unit that determines whether first data including the detected first velocity and first angle from the first propagation path and second data including the detected second velocity and second angle from the second propagation path are data about the same target; and a velocity vector estimation unit that, when it is determined that the first data and the second data are data about the same target, estimates the moving direction and velocity of the same target.

2. A radar signal processing device as described in claim 1, wherein the velocity vector estimation unit comprises: a target movement direction estimation unit that estimates the movement direction of the same target from the first velocity, the first angle, the second velocity, and the second angle; and a velocity estimation unit that estimates the velocity of the same target from the first velocity and the estimated movement direction.

3. A radar system comprising: the radar signal processing device according to claim 1 or 2; and the radar sensor.

4. A radar signal processing method performed by a radar signal processing device having a target detection unit, a same target determination unit, and a velocity vector estimation unit, comprising: a step in which the target detection unit receives a plurality of radar signals detected by a radar sensor and detects, from the received radar signals, a first velocity and a first angle from a first propagation path as a reference, and a second velocity and a second angle from a second propagation path different from the first propagation path; a step in which the same target determination unit determines whether first data including the detected first velocity and first angle from the first propagation path and second data including the detected second velocity and second angle from the second propagation path are data for the same target; and a step in which the velocity vector estimation unit estimates the moving direction and velocity of the same target when it is determined that the first data and the second data are data from the same target.

5. A radar signal processing program that causes a computer to execute the following steps: receiving a plurality of radar signals detected by a radar sensor, and detecting from the received radar signals a first velocity and a first angle from a first propagation path used as a reference, and a second velocity and a second angle from a second propagation path different from the first propagation path; determining whether first data including the detected first velocity and first angle from the first propagation path and second data including the detected second velocity and second angle from the second propagation path are data about the same target; and estimating the moving direction and velocity of the same target when it is determined that the first data and the second data are data about the same target.

Images