Radar mounting angle estimation device and target detection device

Abstract

To accurately estimate a vertical mounting angle of a radar.SOLUTION: A radar mounting angle estimation device 10 for estimating a vertical mounting angle of a radar 2 mounted on a moving body 1 comprises: a range characteristics identification unit 110 that identifies range characteristics, which are characteristics of reception intensities corresponding to distances to reflection points that are sources of reflected waves, by using reception intensities when reflected waves Rw of radiation waves Ew from the radar are received; a local minimum point identification unit 120 that identifies, in a characteristic curve indicating the range characteristics, a local minimum point having a local minimum value of reception intensity generated by weakening in mutual strengthening and weakening of directly reflected waves Rw1 and indirectly reflected waves Rw2 via a road surface, which constitute the reflected waves; and an angle estimation unit 130 that estimates the vertical mounting angle using a distance at the identified local minimum point.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a radar mounting angle estimation device and a target detection device. [Background technology]

[0002] Conventionally, radars such as millimeter-wave radars, which detect the position and relative velocity of a target by emitting a transmission signal of a predetermined wavelength as an electromagnetic wave from an antenna and receiving the reflected wave, have been mounted on vehicles and used in mobile objects. Radars are generally mounted on mobile objects so that they radiate a transmission signal directly in the vehicle's direction of travel. However, the vertical mounting angle of the radar may shift over time. In passenger cars and trucks, if the vertical mounting angle of the radar is shifted, it may erroneously recognize fallen objects on the road surface or signs located above the road as a preceding vehicle. Patent Document 1 discloses a technology that detects that the radar is shifted downward from its expected angle when the received intensity of reflected waves from nearby asphalt is high. Patent Document 2 detects the vertical axis deviation angle of the radar using the received intensity of reflected light (clutter reflection) from nearby asphalt. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-014593 [Patent Document 2] U.S. Patent No. 8,344,940 Summary of the Invention [Problem to be solved by the invention]

[0004] However, while the technology of Patent Document 1 can detect deviations in the radar's vertical mounting angle, it cannot determine the extent of the deviation. Furthermore, the technology of Patent Document 2 cannot accurately determine the radar's vertical mounting angle because the received strength of the reflected waves varies depending on the type of microstructure on the asphalt surface. Given these issues, a technology that can accurately estimate the radar's vertical mounting angle is desired. [Means for solving the problem]

[0005] According to one aspect of the present disclosure, there is provided a radar mounting angle estimation device (10) that estimates the vertical mounting angle of a radar (2) mounted on a moving object (1). The radar mounting angle estimation device includes: a distance characteristic specification unit (110) that specifies, using the reception intensity when a reflected wave (Rw) of a radiation wave (Ew) from the radar is received, a distance characteristic that is a characteristic of the reception intensity according to the distance to a reflection point that is a source of the reflected wave; a minimum point specification unit (120) that specifies a minimum point in a characteristic curve that indicates the distance characteristic, the minimum point having a minimum value of the reception intensity that occurs due to destructive interaction between a direct reflected wave (Rw1) and an indirect reflected wave (Rw2) that travels via a road surface and that constitutes the reflected wave; and an angle estimation unit (130) that estimates the vertical mounting angle using the distance at the specified minimum point.

[0006] According to the radar mounting angle estimation device of this embodiment, the reception strength vs. distance characteristic is determined using the reception strength when a reflected wave from a preceding vehicle is received and the distance between the host vehicle and the preceding vehicle, and a minimum point on a characteristic curve indicating the distance characteristic, where the minimum point has a minimum value of reception strength caused by interference between a direct reflected wave and an indirect reflected wave that constitute the reflected wave, is identified, and the vertical mounting angle is estimated using the distance at the identified minimum point, thereby enabling accurate estimation of the radar's vertical mounting angle. The applicant has found that there is a correlation between the distance of the minimum point on the characteristic curve indicating the distance characteristic and the radar's vertical mounting angle. Specifically, the applicant has found that because the path length difference between a direct reflected wave and an indirect reflected wave depends on the radar's vertical mounting angle, the distance to the minimum value of reception strength caused by interference between a direct reflected wave and an indirect reflected wave can change due to this path length difference. Therefore, as described above, the radar mounting angle estimation device of this embodiment enables accurate estimation of the radar's vertical mounting angle. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a block diagram showing a schematic configuration of a moving body to which a radar mounting angle estimation device and a target detection device according to an embodiment of the present disclosure are applied. [Figure 2] FIG. 1 is a block diagram showing a schematic configuration of a radar mounting angle estimation device. [Figure 3] 5 is a flowchart showing the procedure of radar installation angle estimation processing according to the first embodiment. [Figure 4] 10 is a flowchart showing the detailed procedure of S105. [Figure 5] FIG. 10 is an explanatory diagram illustrating a first conversion process. [Figure 6] FIG. 3 is an explanatory diagram schematically showing a first signal obtained by a first conversion. [Figure 7] FIG. 10 is an explanatory diagram schematically showing a second signal obtained by a second conversion. [Figure 8] FIG. 2 is an explanatory diagram showing an example of an RV map. [Figure 9] FIG. 10 is an explanatory diagram showing an example of a reception intensity-distance graph. [Figure 10] FIG. 2 is an explanatory diagram showing an example of an RV map. [Figure 11] FIG. 10 is an explanatory diagram showing an example of the settings of a vertical mounting angle table. [Figure 12] FIG. 10 is an explanatory diagram showing an example of changes in a reception intensity-distance graph according to an axis shift. [Figure 13] 10 is a flowchart showing the procedure of radar installation angle estimation processing in the second embodiment. [Figure 14] 10 is an explanatory diagram schematically showing the relationship between the direction of a preceding moving body and the reception status of reflected waves at four antennas. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0008] A. First embodiment: A1. Overall structure: The vehicle 1 shown in FIG. 1 includes a radar 2 and a target detection device 3. The vehicle 1 corresponds to a moving body in the present disclosure. The radar 2 is a so-called millimeter wave radar, and emits a radiated wave as an electromagnetic wave consisting of a chirp signal ahead of the vehicle 1 and receives a reflected wave from a target. In this embodiment, the radar 2 is configured to radiate a radiated wave ahead of the vehicle 1 at the time of completion of manufacturing the vehicle 1. The radar 2 is attached to the vehicle 1. Therefore, the traveling direction of the radiated wave (the axial direction during propagation) is approximately parallel to the horizontal direction. In this embodiment, the vertical mounting angle of the radar 2 at the time of completion of manufacturing is "0 degrees." That is, when the vertical mounting angle is "0 degrees," the traveling direction of the radiated wave is parallel to the horizontal direction. The target detection device 3 uses the reception intensity of the reflected wave received by the radar 2 to detect the distance to the target, the relative speed of the target to the vehicle 1, and the direction of the target.

[0009] As shown in the upper right of FIG. 1, the radar 2 includes a signal generating unit 21, a signal transmitting unit 22, an antenna 23, and a beat signal generating unit 24 having a quadrature mixer 25.

[0010] The signal generating unit 21 is configured by, for example, a PLL (Phase Locked Loop) circuit, and generates a transmission signal TX. The signal generating unit 21 in this embodiment continuously generates, as the transmission signal TX, a chirp signal whose frequency is linear with respect to time.

[0011] The signal transmitter 22 is configured as an antenna that radiates a transmission signal TX into space as electromagnetic waves Ew, and radiates the transmission signal TX amplified by a power amplifier PA as electromagnetic waves Ew. The antenna 23 is configured as an antenna that receives electromagnetic waves Rw reflected by a target object OB as a reception signal Dw. Hereinafter, the electromagnetic waves Ew radiated by the transmission signal TX will also be referred to as radiated waves Ew. Furthermore, the electromagnetic waves Rw reflected by the target object OB will also be referred to as reflected waves Rw.

[0012] The beat signal generating unit 24 generates a beat signal RX. The beat signal RX represents a time-domain complex signal generated by mixing the received signal Dw and the transmitted signal TX in the quadrature mixer 25. In addition to the quadrature mixer 25, the beat signal generating unit 24 has a filter unit 26 configured by a low-pass filter, and an analog-to-digital converter 27 configured by an analog-to-digital converter (ADC).

[0013] In this embodiment, the beat signal generator 24 generates signals RX_I and RX_Q. The signal RX_I is a signal based on a signal obtained by mixing a local oscillation signal LO, which is in phase with the transmission signal TX, with a reception signal Dw amplified by a low-noise amplifier LNA. The signal RX_Q is a signal based on a signal obtained by mixing a local oscillation signal LO, which is delayed in phase by 90° relative to the transmission signal TX, with a reception signal Dw amplified in the same manner. The filter unit 26 attenuates high-frequency components from the output signal of the quadrature mixer 25 to suppress aliasing in the analog-to-digital converter 27. The analog-to-digital converter 27 converts the signal processed by the filter unit 26 into a time-domain digital signal and outputs it. In this way, the signal RX_I output by the beat signal generator 24 corresponds to the real part of the beat signal RX, and the signal RX_Q corresponds to the imaginary part of the beat signal RX.

[0014] The target detection device 3 includes a position identification unit 30, a radar mounting angle estimation device 10, and a position information correction unit .

[0015] The position identifying unit 30 uses the beat signal RX output from the radar 2 to identify position information including the distance to the reflection point, which is the source of the reflected wave, in other words, the distance to the target OB, and the direction of the target OB relative to the vehicle 1. The distance to the target OB can be obtained using an RV map, which will be described later.

[0016] The radar mounting angle estimation device 10 estimates the vertical mounting angle of the radar 2 on the vehicle 1. As described above, the vertical mounting angle is 0 degrees when the manufacture of the vehicle 1 is completed. However, the vertical mounting angle of the radar 2 can change due to aging deterioration of the mounting members of the radar 2 and vibrations input to the radar 2 over many years. As a result, the vertical mounting angle may change to a positive value, causing the propagation direction of the radiated waves to change to an angle looking up above the horizontal, or the vertical mounting angle may change to a negative value, causing the propagation direction of the radiated waves to change to an angle looking down below the horizontal. Even when such a change in the vertical mounting angle occurs, the radar mounting angle estimation device 10 accurately estimates the vertical mounting angle of the radar 2. A detailed configuration of the radar mounting angle estimation device 10 will be described later.

[0017] Position information corrector 40 corrects the position information identified by the position identifying unit 30, using the vertical mounting angle of radar 2 estimated by radar mounting angle estimation device 10. As described above, if the traveling direction of the radiated waves becomes downward due to aging of the vertical mounting angle of radar 2, there is a risk that an object that has fallen on the road surface will be erroneously identified as a preceding vehicle located in front of vehicle 1. Furthermore, if the traveling direction of the radiated waves becomes upward due to aging of the vertical mounting angle of radar 2, there is a risk that various signs and traffic lights located above the road will be erroneously identified as a preceding vehicle located in front of vehicle 1. Therefore, position information corrector 40 corrects the position information identified by position identifying unit 30, using the vertical mounting angle of radar 2 estimated by radar mounting angle estimation device 10, thereby correcting it to position information for which the vertical mounting angle is 0 degrees.

[0018] A2. Configuration of radar installation angle estimation device 10: 2, the radar mounting angle estimation device 10 is configured as an ECU (Electronic Control Unit) in which a CPU 100, a ROM 200, and a RAM 300 are configured to be able to transmit and receive data to and from each other via a bus 400. The CPU 100 functions as a distance characteristic specifying section 110, a minimum value specifying section 120, and an angle estimation section 130 by loading a control program stored in advance in the ROM 200 into the RAM 300 and executing the program.

[0019] The distance characteristic identification unit 110 identifies the characteristics of the reception intensity (hereinafter referred to as "distance characteristics") according to the distance to the reflection point (target OB) that is the source of the reflected wave Rw, by using the reception intensity when the reflected wave Rw of the emitted wave Ew output from the radar 2 is received. The distance characteristic identification unit 110 includes a first conversion unit 111, a second conversion unit 112, an RV map generation unit 113, and a characteristic curve identification unit 114. The processing contents executed by the first conversion unit 111, the second conversion unit 112, the RV map generation unit 113, and the characteristic curve identification unit 114 will be described later.

[0020] The minimum value identifying unit 120 identifies a minimum point in the characteristic curve indicating the distance characteristic identified by the distance characteristic identifying unit 110. The angle estimating unit 130 estimates the vertical installation angle of the radar 2 by using the distance at the minimum point identified by the minimum value identifying unit 120.

[0021] In addition to the above-mentioned control program, the ROM 200 pre-stores a vertical mounting angle table 201. In the vertical mounting angle table 201, the distances of the minimum points identified by the minimum value identification unit 120 and the vertical mounting angles of the radar 2 are set in advance in correspondence with each other. Details of the processes executed by the minimum value identification unit 120 and the angle estimation unit 130 and details of the settings of the vertical mounting angle table 201 will be described later.

[0022] A3. Radar installation angle estimation process: 3 is processing for estimating the vertical mounting angle of the radar 2. The radar mounting angle estimation processing is started when the power of the target detection device 3 is turned on and the radar mounting angle estimation device 10 receives a beat signal RX from the radar 2.

[0023] In step S105, RV map generation is executed. Hereinafter, "step S" may be simply referred to as "S." As shown in Fig. 4, S105 includes S205, S210, and S215.

[0024] In S205, the first conversion unit 111 performs a Fourier transform on the beat signal RX received from the radar 2 to generate a first signal. The first signal refers to a signal in which frequency components obtained by the Fourier transform are represented for each distance bin. The Fourier transform to generate the first signal in S205 is also referred to as a first transform.

[0025] In Fig. 5, the horizontal axis indicates the chirp number, the vertical axis indicates time, and the vertical axis indicates the reception strength of the reception signal Dw. As shown in Fig. 5, the reception strength of the reception signal Dw, indicated by the black rectangles, is obtained as a discrete waveform (value). These reception strength values ​​are Fourier transformed (discrete Fourier transformed) for each chirp number. An FFT (Fast Fourier Transform) may be used as this Fourier transform.

[0026] In FIG. 6, the horizontal axis represents time (chirp number), and the vertical axis represents frequency (range bin). Specifically, the horizontal axis lists, from left to right, the first chirp #1, the second chirp #2, the third chirp #3, and so on. The vertical axis lists the first range bin Dbin1, the second range bin Dbin2, the third range bin Dbin3, the fourth range bin Dbin4, and the fifth range bin Dbin5, and so on. In FIG. 6, range bins where the magnitude of the complex number obtained as a result of the Fourier transform is equal to or greater than thermal noise are hatched. Note that the hatched range bins are range bins where a target is present at that range. The example in FIG. 6 shows that, across all chirp numbers, the magnitude of the complex number obtained as a result of the Fourier transform at the fifth range bin Dbin5 is equal to or greater than thermal noise.

[0027] As shown in FIG. 4, in S210, the second conversion unit 112 performs a Fourier transform on the values ​​at the same distance bin in the multiple first signals obtained for each chirp number at predetermined time intervals to convert them into second signals whose frequency components are represented by relative velocity bins. The Fourier transform on the second signals in S210 is also referred to as a second transform. For example, for the first signal shown in FIG. 6, the values ​​of each chirp number #1, #2, #3, ... for the first distance bin Dbin1 are treated as a single waveform and subjected to a Fourier transform (discrete Fourier transform). Similarly, the values ​​of each chirp frequency #1, #2, #3, ... for the second distance bin Dbin2 are treated as a single waveform and subjected to a Fourier transform. This process is then performed sequentially for the fourth distance bin Dbin4, the fifth distance bin Dbin5, ..., and so on.

[0028] In FIG. 7, the horizontal axis represents relative velocity (relative velocity bin), and the vertical axis represents distance (distance bin). The left end represents relative velocity -100 km / h, and the right end represents relative velocity +100 km / h. The vertical axis in FIG. 7 is the same as the vertical axis in FIG. 6. When the first signal shown in FIG. 6 is Fourier transformed for each distance bin, in the first signal, only the fifth distance bin Dbin5 contains a value whose complex number is greater than or equal to thermal noise. Therefore, in the second signal, only the fifth distance bin Dbin5 contains a value whose complex number is greater than or equal to thermal noise. In the example of FIG. 7, a value whose complex number is greater than or equal to thermal noise exists at a position where the distance bin is the fifth distance bin Dbin5 and the relative velocity bin is the relative velocity bin corresponding to +12 km / h.

[0029] 4, in S215, the RV map generating unit 113 generates an RV map based on the second signal obtained in S210. The RV map represents the reception strength for each distance bin and each relative velocity bin.

[0030] In FIG. 8, the horizontal axis represents relative velocity (relative velocity bin), the vertical axis represents distance (distance bin), and the vertical axis represents reception strength. Note that FIG. 8 shows the reception signal strength from the thermal floor noise, in other words, the SNR (signal-to-noise ratio). The reception strength can be calculated from the real and imaginary parts of the second signal as the magnitude of a complex number. Specifically, it can be calculated by subtracting the thermal floor noise from the square root of the sum of the squares of the real part and the imaginary part. Based on the second signal shown in FIG. 7, an RV map is generated, as shown in FIG. 8, in which a reception strength peak s0 appears at the position where the distance bin is the fifth distance bin Dbin5 and the relative velocity bin is the relative velocity bin corresponding to +12 km / h.

[0031] As shown in FIG. 3, in S110, the characteristic curve identification unit 114 determines whether or not a peak exists in a specific RV region in the RV map generated in S105. The specific RV region refers to a region that includes a range of predetermined distance bins that corresponds to a specific distance range and a range of predetermined relative speed bins. In FIG. 8, the specific RV region ArS is represented by a thick solid line. The "specific distance range" refers to a distance range that includes an estimated distance along the traveling direction to another vehicle ahead of the vehicle 1. In this embodiment, the specific distance range is 30 m (meters) or more and 50 m or less, and refers to the distance range Ar1 from the fifth distance bin Dbin5 to the tenth distance bin Dbin10, as shown in FIG. 8. The above-mentioned "predetermined relative speed bin range" refers to a relative speed range that includes 0 km / h and is equal to or greater than -24 km / h and equal to or less than +24 km / h. In summary, in this embodiment, the specific RV region ArS is a region consisting of relative speed bins corresponding to relative speed bins of -24 km / h or more and +24 km / h or less, and distance bins corresponding to distance bins of 30 m or more and 50 m or less. Such a specific RV region ArS can be said to be a region where peaks due to reflected waves from other moving objects traveling in front of the vehicle 1 are expected to appear while the vehicle 1 is traveling. In the example of Fig. 8, peak s0 appears within the specific RV region ArS.

[0032] 3, if it is determined that no peak exists in the specific RV region (S110: NO), the process returns to S105. On the other hand, if it is determined that a peak exists in the specific RV region (S110: YES), the characteristic curve determination unit 114 plots the reception strength and distance of the peak determined to exist in the specific RV region in S110 on a reception strength-distance graph (S115).

[0033] In the reception strength-distance graph shown in Fig. 9, the horizontal axis represents distance and the vertical axis represents reception strength. When peak s0 exists in the specific RV region ArS as shown in Fig. 8, point Ps0 corresponding to the distance and reception strength of peak s0 is plotted as shown in Fig. 9. Note that in Fig. 9, many points other than point Ps0 have already been plotted, and a characteristic curve L0 has been obtained. The characteristic curve L0 is a curve that indicates the distance characteristic, which is the characteristic of reception strength according to the distance to the reflection point (target).

[0034] Here, as shown in Fig. 9, the characteristic curve L0 has a plurality of minimum points p1, p2, p3, p4, p5, .... Such minimum points p1 and so on are generated because, as shown in Fig. 1, due to the difference in path between a direct reflected wave Rw1, which is a reflected wave that reaches the antenna 23 directly from the target, and an indirect reflected wave Rw2 that is reflected from the target and further reaches the antenna 23 via the road surface, there is a 180-degree phase difference between the direct reflected wave Rw1 and the indirect reflected wave Rw2, which causes the direct reflected wave Rw1 and the indirect reflected wave Rw2 to weaken each other's signal strength.

[0035] As shown in FIG. 3, after completion of S115, in S120, the characteristic curve identification unit 114 determines whether the number (total number) of plotted points in any distance bin of the specific RV region ArS is equal to or greater than a predetermined threshold.

[0036] In the example of the RV map shown in FIG. 10, more peaks appear in the specific RV region ArS than in the example of FIG. 8. Note that FIG. 10 shows a collection of multiple RV maps generated in S105. In the example of FIG. 10, a peak group pg3 appears, each consisting of one peak, in the region where the relative velocity is the relative speed bin of +12 km / h and the distance bins are the fifth distance bin Dbin5 to the tenth distance bin Dbin10. In peak group pg3, the reception strength of the peak becomes minimum at a distance bin of approximately 43 m, and the reception strength increases with increasing distance from this distance bin. The peak at the distance bin of 43 m corresponds to a minimum point such as minimum point p1 shown in FIG. 9.

[0037] Two peaks s1 and s2 appear outside the specific RV region ArS and within the distance range Ar1. Peak s1 appears at a relative speed bin of approximately -84 km / h and a distance bin of approximately 40 m, and is a peak based on, for example, a reflected wave from an oncoming vehicle traveling in the opposite lane of the reflection point (target). Peak s2 appears at a relative speed bin of approximately -48 km / h and a distance bin of 40 m, and is a peak based on, for example, a reflected wave from a guardrail (stationary object) near the reflection point (target).

[0038] As shown in Fig. 3, if it is determined that the total number of plotted points is not equal to or greater than the predetermined threshold in any distance bin in the specific RV region ArS (S120: NO), the process returns to S105. Therefore, S105 to S120 are executed again, and it is highly likely that new points will be plotted on the reception intensity-distance graph. In this embodiment, the threshold in S120 is set so that a sufficient number of points are plotted to clearly show minimum points on the characteristic curve L0 shown in Fig. 9. Such a threshold can be determined, for example, by experiment, simulation, or the like.

[0039] 3, if it is determined that the total number of plotted points is equal to or greater than a predetermined threshold in any distance bin in the specific RV region ArS (S120: YES), the minimum value identification unit 120 identifies a minimum point in the characteristic curve (S125). In this embodiment, the minimum point identified in S125 is a minimum point in the specific distance range Ar1. Therefore, in the example of FIG. 9, only minimum point p1 is identified.

[0040] 3, the angle estimation unit 130 estimates the vertical mounting angle of the radar 2 by using the distance of the minimum point identified in S125 (S130). Specifically, the angle estimation unit 130 refers to the vertical mounting angle table 201 and estimates the vertical mounting angle based on the distance at the minimum point.

[0041] In Fig. 11, the horizontal axis indicates the distance to the minimum point, and the vertical axis indicates the vertical mounting angle of the radar 2. As shown in Fig. 11, in the vertical mounting angle table 201 of this embodiment, the vertical mounting angle is 0 degrees at distance D0. In addition, in the vertical mounting angle table 201, as the distance to the minimum point increases from distance D0, the vertical mounting angle becomes a larger value on the positive side. In addition, in the vertical mounting angle table 201, as the distance to the minimum point decreases from distance D0, the vertical mounting angle becomes a smaller value on the negative side. The reason why the vertical mounting angle table 201 is set in this manner will be explained using Fig. 12.

[0042] In FIG. 12, the top row shows characteristic curve L2 when the deviation of the vertical mounting angle of radar 2 is +b degrees. The second row shows characteristic curve L1 when the deviation of the vertical mounting angle of radar 2 is +a degrees. The third row shows characteristic curve L0 when the deviation of the vertical mounting angle of radar 2 is 0 degrees, i.e., when there is no deviation of the vertical mounting angle. Note that this characteristic curve L0 is the same as the characteristic curve L0 shown in FIG. 9. In FIG. 12, the fourth row shows characteristic curve L11 when the deviation of the vertical mounting angle of radar 2 is -c degrees. The bottom row shows characteristic curve L12 when the deviation of the vertical mounting angle of radar 2 is -d degrees. Note that the portion corresponding to the specific distance range Ar1 is surrounded by a dashed rectangle across each of characteristic curves L0, L1, L2, L11, and L12.

[0043] As shown in Figure 12, as the deviation of the vertical mounting angle gradually decreases toward the negative side, in other words, as the radiation direction of the radiated wave from the radar 2 deviates significantly downward, the distance to the minimum point p1 gradually decreases. This is for the following reason. As the deviation of the vertical mounting angle gradually decreases toward the negative side, in other words, as the radiation direction of the radiated wave from the radar 2 deviates significantly downward, the path difference between the direct reflected wave Rw1 and the indirect reflected wave Rw2 gradually increases. For this reason, a point where the reception strength of the direct reflected wave Rw1 and the indirect reflected wave Rw2 weakens each other, i.e., a minimum point p1, occurs at a position where the preceding vehicle is closer. Therefore, as described above, as the deviation of the vertical mounting angle gradually decreases toward the negative side, the distance to the minimum point p1 gradually decreases within the specific RV region ArS. In this embodiment, the vertical mounting angle of the radar 2 is shifted many times through experiments and simulations to identify the distance to the minimum point, and the vertical mounting angle table 201 is set by associating the vertical mounting angle with the distance to the minimum point.

[0044] 3, after completion of S130, the process returns to S105. When the vertical mounting angle of the radar 2 is estimated in S130, the position information correction unit 40 corrects the position information identified by the position identification unit 30 using the estimated vertical mounting angle. Specifically, the vertical position of the target OB identified by the position identification unit 30 is corrected so as to cancel the deviation of the vertical mounting angle from the initial vertical mounting angle (0 degrees).

[0045] According to the radar mounting angle estimation device 10 of the first embodiment described above, the reception strength when a reflected wave from a preceding vehicle is received and the distance between the host vehicle (vehicle 1) and the preceding vehicle are used to identify the characteristics (distance characteristics) of the reception strength according to the distance to the reflection point (target OB), and the distance at the identified minimum point is used to estimate the vertical mounting angle of the radar 2, thereby making it possible to accurately estimate the vertical mounting angle of the radar 2. The applicants have found that there is a correlation between the distance to the minimum point in the characteristic curve indicating the distance characteristics and the vertical mounting angle of the radar 2. Specifically, it was found that because the path length difference between the direct reflected wave Rw1 and the indirect reflected wave Rw2 depends on the vertical mounting angle of the radar 2, the distance to the minimum value of the received intensity, which occurs when the direct reflected wave Rw1 and the indirect reflected wave Rw2 weaken each other, can change due to this path length difference. For this reason, as described above, the radar mounting angle estimation device 10 of the first embodiment can accurately estimate the vertical mounting angle of the radar 2. Furthermore, compared to a configuration that specifies the vertical mounting angle using the magnitude of the received intensity of clutter reflected from the asphalt surface, the vertical mounting angle of the radar 2 can be estimated without depending on the type of microstructure of the asphalt surface, and therefore estimation can be performed with greater accuracy.

[0046] Furthermore, since the minimum point is identified from the characteristic curve in the specific distance range ArS, which is a predetermined distance range in which only one minimum point is identified, it is possible to prevent the erroneous identification of a change in the distance of the minimum point due to the presence of multiple minimum points.

[0047] In addition, the beat signal is Fourier transformed into a first signal, and the value at the same distance bin in the first signal is Fourier transformed into a second signal in which the frequency components are represented for each relative velocity bin. An RV map is generated based on the second signal, and the peaks in each generated RV map are plotted on a reception strength-distance graph to identify the characteristic curve, thereby making it possible to obtain an appropriate characteristic curve.

[0048] In addition, since the specific distance range Ar1 is a distance range that includes the distance assumed to be the distance along the traveling direction to the preceding moving body, the distance of the minimum value of the reception strength generated by the interference of the direct reflected wave Rw1 and the indirect reflected wave Rw2 from the preceding moving body can be used to estimate the vertical mounting angle. Therefore, the reflected wave that occurs with high frequency can be used to estimate the vertical mounting angle, so the vertical mounting angle can be estimated with high frequency. In addition, since the reflected wave from the target located in front of the vehicle 1 can be used to estimate the vertical mounting angle, the vertical mounting angle can be estimated with higher accuracy.

[0049] Further, when a peak exists within a specific RV region ArS, which is an area in the RV map consisting of a relative speed bin corresponding to a predetermined relative speed range including zero speed and a distance bin corresponding to a specific distance range, the reception intensity of the peak and the distance indicated by the distance bin of the peak are plotted on the reception intensity-distance graph, so that reflected waves from targets that are relatively close to the vehicle 1 and have a relatively small relative speed, that is, reflected waves obtained in a situation where direct reflected waves Rw1 and indirect reflected waves Rw2 can be stably obtained, can be used to estimate the vertical installation angle of the radar 2, and the vertical installation angle can be estimated more accurately. On the other hand, when a peak does not exist within the specific RV region, the reception intensity of the peak and the distance indicated by the distance bin of the peak are not plotted on the reception intensity-distance graph, so that reflected waves from targets that are relatively far from the vehicle 1 or have a relatively large relative speed, that is, reflected waves obtained in a situation where direct reflected waves and indirect reflected waves cannot be stably obtained, can be prevented from being used to estimate the vertical installation angle, and a decrease in the estimation accuracy of the vertical installation angle can be suppressed.

[0050] Furthermore, if the number of peaks in each distance bin corresponding to the number of points plotted on the reception strength-distance graph is smaller than a predetermined threshold, a minimum point is not identified, but if it is equal to or greater than the threshold, a minimum point is identified, thereby enabling the minimum point to be identified with high accuracy.

[0051] Furthermore, the angle estimation unit 130 refers to the vertical mounting angle table 201 in which the distances of the minimum points and the vertical mounting angles of the radar 2 are previously associated with each other, and estimates the vertical mounting angle based on the distance at the identified minimum point, so that the estimation accuracy of the vertical mounting angle can be improved.

[0052] Furthermore, the position information correction unit 40 uses the vertical mounting angle estimated by the radar mounting angle estimation device 10 to correct the position information identified by the position identification unit 30 to position information when the vertical mounting angle is a predetermined angle. Therefore, the target detection device 3 of this embodiment can identify position information with high accuracy.

[0053] B. Second embodiment: The configuration of the target detection device 3 of the second embodiment is the same as the configuration of the target detection device 3 of the first embodiment, so the same components are given the same reference numerals and detailed description thereof will be omitted. The radar 2 of the second embodiment differs from the radar 2 of the first embodiment in that it includes four sets, each of which includes an antenna 23, a beat signal generating unit 24, and a low-noise amplifier LNA. These sets are provided so that the four antennas 23, that is, antennas 23a to 23d, are arranged side by side in the vertical direction, as shown in Fig. 14.

[0054] The radar installation angle estimation process of the second embodiment shown in FIG. 13 differs from the radar installation angle estimation process of the first embodiment shown in FIG. 3 only in that S112 is added and executed, and the other steps are the same.

[0055] If it is determined in the above-mentioned S110 that a peak exists in the specific RV region (S110: YES), the characteristic curve identification unit 114 determines whether or not the target exists only in front (S112). Specifically, the characteristic curve identification unit 114 determines whether or not all of the multiple second signals are expressed as the same complex number. If it is determined that all of the multiple second signals are expressed as the same complex number, the characteristic curve identification unit 114 determines that the target exists only in front. If it is determined that the target exists only in front (S112: YES), the above-mentioned S115 is executed. Therefore, in this case, the reception strength and distance of the peak are plotted on the reception strength-distance graph. On the other hand, if it is determined that the multiple second signals are expressed as different complex numbers from each other, the characteristic curve identification unit 114 determines that the target does not exist only in front. If it is determined that the target does not exist only in front (S112: NO), the processing returns to S105. Therefore, in this case, the peak reception strength and distance are not plotted on the reception strength-distance graph. For example, as shown in FIG. 14, the reflected wave from the preceding vehicle V1 located in the forward direction D1 overlaps with the reflected wave from the preceding vehicle V2 located in a direction D2 different from the forward direction, so the second signals based on the signals received by the multiple antennas 23a-23d are different from each other. On the other hand, if the preceding vehicle V1 is present only in the forward direction D1 and the preceding vehicle V2 is not present, the second signals based on the signals received by the multiple antennas 23a-23d are the same. Note that in the example of FIG. 14, a path difference d1 occurs between the path of the direct reflected wave Rw1 received by the antenna 23a and the path of the direct reflected wave Rw1 received by the antenna 23b. Similarly, a path difference d2 occurs between the path of the direct reflected wave Rw1 received by the antenna 23a and the path of the direct reflected wave Rw1 received by the antenna 23c. Similarly, a path difference d3 occurs between the path of the direct reflected wave Rw1 received by the antenna 23a and the path of the direct reflected wave Rw1 received by the antenna 23d.

[0056] The radar mount angle estimation device 10 and target detection device 3 of the second embodiment described above achieve the same effects as the radar mount angle estimation device 10 and target detection device 3 of the first embodiment. In addition, the radar mount angle estimation device 10 of the second embodiment determines whether or not a target exists only directly ahead, and if it is determined that a target exists only directly ahead, plots the reception intensity of the peak and the distance indicated by the distance bin of that peak on a reception intensity vs. distance graph, but does not plot them if it is determined that the target does not exist only directly ahead. Therefore, if the target exists in a location other than directly ahead and there is a risk that the estimation accuracy of the vertical mount angle of the radar 2 will decrease, plotting on the reception intensity vs. distance graph can be suppressed. This makes it possible to suppress a decrease in the estimation accuracy of the vertical mount angle of the radar 2. Furthermore, if the complex numbers representing a plurality of second signals are all expressed as the same complex number, it is determined that a target exists only directly ahead, and if the complex numbers representing a plurality of second signals are different from each other, it is determined that a target does not exist only directly ahead, so it is possible to accurately determine whether or not a target exists only directly ahead.

[0057] C. Other Embodiments: (C1) In each embodiment, the specific RV region ArS is a region consisting of relative speed bins corresponding to a relative speed bin range of -24 km / h to +24 km / h and distance bins corresponding to a distance bin range of 30 m to 50 m. However, the present disclosure is not limited to this. The range of relative speed bins in the specific RV region ArS is not limited to relative speed bins corresponding to a relative speed bin range of -24 km / h to +24 km / h, but may be a range of relative speed bins corresponding to any speed range including 0 km / h. Furthermore, the range of distance bins in the specific RV region ArS, i.e., the specific distance range Ar1, is not limited to 30 m to 50 m, but may be, for example, any distance range assumed as the distance along the traveling direction to another moving object preceding the vehicle 1. Furthermore, for example, the range may be any distance range in which only one minimum point is identified through experiments, simulations, or the like.

[0058] (C2) In the radar mounting angle estimation process of each embodiment, in S115, the reception strength and distance of a peak determined to exist in the specific RV region ArS are plotted on a reception strength-distance graph, and in S125, a minimum point in the specific distance range Ar1 is identified. However, the present disclosure is not limited to this. For example, the reception strength and distance of a peak existing in a distance range wider than the specific RV region ArS, in which two or more minimum points can be identified, may be plotted on a reception strength-distance graph, and the minimum point may be identified in such a range. Even in such a configuration, the reception strength range at the minimum point may be specified in advance, and a point whose reception strength falls within the previously specified reception strength range may be identified in S125 from among the two or more identified minimum points. This is because, as shown in FIGS. 9 and 12, the reception strengths at multiple minimum points are different from one another. Therefore, by specifying a reception strength range in which only one minimum point can be identified, the same effects as those of each embodiment can be achieved.

[0059] (C3) In S120 of the radar mounting angle estimation process in each embodiment, it is determined whether the total number of plotted points in all distance bins in the specific RV region ArS is equal to or greater than a predetermined threshold value. However, the present disclosure is not limited to this. In S120, it may be determined whether the elapsed time since S105 was first started exceeds a predetermined threshold time. Then, S125 may be executed if it is determined that the elapsed time has exceeded the threshold time, and the process may return to S105 if it is determined that the elapsed time has not exceeded the threshold time. Even with this configuration, the same effects as those of each embodiment are achieved.

[0060] (C4) In S130 of the radar mounting angle estimation process in each embodiment, the vertical mounting angle is estimated based on the distance at the minimum point by referring to the vertical mounting angle table 201. However, the present disclosure is not limited to this. An arithmetic expression showing the relationship between the distance at the minimum point and the vertical mounting angle, such as the vertical mounting angle table 201 shown in Fig. 11, may be specified in advance, and the vertical mounting angle may be estimated using this arithmetic expression.

[0061] (C5) In each embodiment, the vertical mounting angle of the radar 2 estimated by the radar mounting angle estimation device 10 is used to correct the position information identified by the position identifying unit 30, but the present disclosure is not limited to this. For example, the estimated vertical mounting angle may be used in a process of storing the estimated vertical mounting angle in ROM 200. Alternatively, the estimated vertical mounting angle may be used in a process of displaying the estimated vertical mounting angle on a monitor screen (not shown) or in a process of notifying a predetermined destination by e-mail or the like. In these usage scenarios, the position information correcting unit 40 may be omitted.

[0062] (C6) The target detection device 3, radar mounting angle estimation device 10, and the methods described herein may be realized by a special-purpose computer provided by configuring a processor and memory programmed to execute one or more functions embodied in a computer program. Alternatively, the target detection device 3, radar mounting angle estimation device 10, and the methods described herein may be realized by a special-purpose computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the target detection device 3, radar mounting angle estimation device 10, and the methods described herein may be realized by one or more special-purpose computers configured by combining a processor and memory programmed to execute one or more functions with a processor configured with one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by a computer on a computer-readable non-transitory tangible recording medium.

[0063] The present disclosure may be realized in various forms, such as a target detection method, a target detection device, a computer program for realizing the target detection method, a non-transitory recording medium on which such a computer program is recorded, and the like.

[0064] The present disclosure is not limited to the above-described embodiments and can be realized in various configurations without departing from the spirit thereof. For example, technical features in each embodiment corresponding to technical features in the embodiments described in the Summary of the Invention section can be appropriately replaced or combined to solve some or all of the above-described problems or achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate. The present disclosure can be realized in the form of, for example, a control method for a collision damage mitigation function, a computer program for implementing such a method, a non-transitory recording medium on which such a computer program is recorded, etc. [Explanation of symbols]

[0065] 1...mobile body, 2...radar, 10...radar mounting angle estimation device, Ew...radiated wave, Rw...reflected wave, 110...distance characteristic determination unit, Rw1...direct reflected wave, Rw2...indirect reflected wave, 120...minimum point determination unit, 130...angle estimation unit

Claims

1. A radar mounting angle estimation device (10) for estimating the vertical mounting angle of a radar (2) mounted on a moving object (1), comprising: a distance characteristic specifying unit (110) that uses a reception intensity when a reflected wave (Rw) of a radiation wave (Ew) from the radar is received to specify a distance characteristic that is a characteristic of the reception intensity according to a distance to a reflection point that is a source of the reflected wave; a minimum point identifying unit (120) that identifies a minimum point on a characteristic curve that indicates the distance characteristics, the minimum point having a minimum value of the reception intensity that occurs due to destructive interference between a direct reflected wave (Rw1) and an indirect reflected wave (Rw2) that travels via a road surface, which constitute the reflected wave; an angle estimation unit (130) that estimates the vertical mounting angle by using the distance at the identified minimum point; A radar installation angle estimation device comprising:

2. 2. The radar mounting angle estimation device according to claim 1, the minimum point identifying unit identifies the minimum point from the characteristic curve in a specific distance range (Ar1), which is a predetermined distance range as the distance range in which only one minimum point is identified.

3. 3. The radar mounting angle estimation device according to claim 2, The distance characteristic determination unit a first transforming unit (111) that performs a Fourier transform on a beat signal (Rx) generated by mixing the emitted wave consisting of a chirp signal and a received signal (Dw) of the reflected wave by an orthogonal mixer (25) into a first signal whose frequency components are represented for each distance bin, for each chirp number; a second transform unit (112) that performs a Fourier transform on the values ​​at the same distance bin in the plurality of first signals obtained for each chirp number, at predetermined time intervals, to convert the values ​​into second signals whose frequency components are represented for each relative velocity bin; an RV map generating unit (113) that generates an RV map representing the reception intensity for each of the distance bins and the relative velocity bins based on the second signal obtained by the second conversion unit; a characteristic curve specifying unit (114) that specifies the characteristic curve by plotting the reception intensity of each peak and the distance indicated by the distance bin of each peak on a reception intensity-distance graph for each peak in the generated RV map; A radar installation angle estimation device having the above.

4. 4. The radar mounting angle estimation device according to claim 3, A radar mounting angle estimation device, wherein the specific distance range is a distance range that includes an estimated distance along the traveling direction to a preceding moving body that is another moving body that is ahead of the moving body.

5. The radar mounting angle estimation device according to claim 3, The characteristic curve specifying unit determining, based on the second signal, whether or not the target indicated by the second signal is present only in front of the moving body; When it is determined that the target is present only in front of the vehicle, the reception strength of the peak of the second signal and the distance indicated by the distance bin of the peak are plotted on the reception strength-distance graph; a radar mounting angle estimation device that, when it is determined that the target is not present only in front of the radar, does not plot the reception strength of the peak of the second signal and the distance indicated by the distance bin of the peak on the reception strength-distance graph.

6. 4. The radar mounting angle estimation device according to claim 3, The characteristic curve specifying unit If the peak exists within a specific RV area (ArS), which is an area in the RV map that is made up of the relative velocity bin corresponding to a predetermined relative velocity range including zero and the distance bin corresponding to the specific distance range, the reception intensity of the peak and the distance indicated by the distance bin of the peak are plotted on the reception intensity-distance graph; If the peak does not exist within the specific RV region, the reception strength of the peak and the distance indicated by the distance bin of the peak are not plotted on the reception strength-distance graph.

7. 7. The radar mounting angle estimation device according to claim 6, The minimum point identification unit If the number of peaks in each distance bin corresponding to the number of points plotted on the reception strength-distance graph is less than a predetermined threshold, the minimum point is not identified; The radar mounting angle estimation device identifies the minimum point when the number of peaks in each distance bin corresponding to the number of points plotted on the reception strength vs. distance graph is equal to or greater than the threshold value.

8. 2. The radar mounting angle estimation device according to claim 1, the angle estimation unit refers to a vertical mounting angle table (201) in which the distances to the minimum points and the vertical mounting angles are associated in advance, and estimates the vertical mounting angle based on the distances at the specified minimum points.

9. A target detection device (3), The radar mounting angle estimation device according to any one of claims 1 to 6, a position specifying unit (30) that uses the reception intensity to specify position information of the target including the distance and the direction of the target including the reflection point; a position information correction unit (40) that uses the vertical mounting angle estimated by the radar mounting angle estimation device to correct the position information identified by the position identification unit to position information when the vertical mounting angle is a predetermined angle; A target detection device comprising:

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