Azimuth estimation device and azimuth estimation method

Abstract

To provide an azimuth estimation device and an azimuth estimation method capable of improving an azimuth-dependent error.SOLUTION: An azimuth estimation device estimates an arrival angle of a transmission wave, which has passed through a protective member B of a transmission antenna 13 and has been reflected by a target, to a radar device 1 as an azimuth of the target. The azimuth estimation device includes: a power profile storage section 322 that stores a power profile; a power calculation section 313 that obtains reception power; a distance calculation section 314 that obtains the distance between protective members; and an azimuth estimation section 316 that estimates an azimuth on the basis of the distance between protective members. The power profile storage section stores, for each azimuth, the power profile in which the reception power corresponding to superimposed reflected waves from two or more azimuths different from each other is associated with the distance between protective members. The power calculation section obtains the first reception power and the second reception power. The distance calculation section obtains the distance between protective members on the basis of the first reception power, the second reception power, and the power profile.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to an azimuth estimation device and an azimuth estimation method.

Background Art

[0002] Conventionally, a radar device including an array antenna, a receiving analog circuit including a receiving circuit, and a memory storing a plurality of calibration data for calibrating errors occurring in the array antenna and the receiving analog circuit has been known (see, for example, Patent Document 1). This radar device roughly estimates and extracts the arrival angle from a target, selects calibration data from a plurality of calibration data according to the extracted arrival angle, performs calibration processing using the selected calibration data, and calculates the arrival angle of the target.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, Patent Document 1 describes an embodiment in which a radar device is attached to a vehicle. When the radar device is attached to a vehicle, generally, the radar device is attached inside the bumper of the vehicle. In this case, a bumper of the vehicle exists between the radar device and the target.

[0005] When there is a protective member such as a bumper that protects the radar device between such a radar device and a target, the protective member becomes a factor that causes an error in the arrival angle measured by the radar device. Specifically, the transmitted wave from the radar device and the reflected wave reflected by the target are affected by refraction and reflection by the protective member, resulting in errors in the amplitude and phase of the received signal at some arrival angles, and mutual coupling errors between the antennas. Such an error that depends on the arrival angle is hereinafter also referred to as an azimuth-dependent error.

[0006] As a result of intensive studies by the inventors, it has been found that the azimuth-dependent error depends on the distance between the radar device and the protective member. Therefore, when there is a protective member between the radar device and the target, in order to correct the error, it is necessary to obtain the distance between the radar device and the protective member, and correct the arrival angle of the target based on the obtained distance between the radar device and the protective member.

[0007] However, the radar device described in Patent Document 1 does not consider the azimuth-dependent error caused by the protective member when correcting the arrival angle, and cannot improve the above-mentioned azimuth-dependent error caused by the protective member.

[0008] An object of the present disclosure is to provide an azimuth estimation device and an azimuth estimation method capable of improving the azimuth-dependent error.

Means for Solving the Problems

[0009] According to one aspect of the present disclosure, An azimuth estimation device that estimates the arrival angle of a transmitted wave transmitted from a transmission antenna (13), passing through a protective member (B) of the transmission antenna, and reflected by a target to the radar device (1) as the azimuth of the target, A power profile storage unit (322) that stores a power profile in which the distance between the transmission antenna and the protective member, which is the distance between the protective members, is associated with the received power corresponding to the superimposed reflected wave in which the reflected wave reflected by the target and the reflected wave reflected by the protective member overlap; A power calculation unit (313) that obtains the received power corresponding to the superimposed reflected wave; A distance calculation unit (314) that obtains the distance between protection members based on the received power required by the power calculation unit, and an azimuth estimation unit (316) that estimates the azimuth based on the distance between the protection members obtained by the distance calculation unit. In the power profile storage unit, a power profile in which the received power corresponding to the superimposed reflected waves from two or more different azimuths and the distance between the protection members are associated is stored for each azimuth. The power calculation unit obtains a first received power corresponding to the superimposed reflected wave received from at least a first azimuth among two or more azimuths, and a second received power corresponding to the superimposed reflected wave received from a second azimuth different from the first azimuth among two or more azimuths. The distance calculation unit obtains the distance between the protection members based on the first received power, the second received power, and the power profile.

[0010] Also, according to another aspect of the present disclosure, An azimuth estimation method for estimating the arrival angle of a transmitted wave transmitted from a transmission antenna (13), passing through the protection member (B) of the transmission antenna, and reflected by a target to the radar device (1) as the azimuth of the target is as follows: A power profile acquisition step (S24) of acquiring a power profile in which the distance between the protection members, which is the distance between the transmission antenna and the protection member, and the received power corresponding to the superimposed reflected wave in which the reflected wave reflected by the target and the reflected wave reflected by the protection member overlap are associated; A power calculation step (S33, S36) of obtaining the received power corresponding to the superimposed reflected wave; A distance calculation step (S38) of obtaining the distance between the protection members based on the received power obtained in the power calculation step; An azimuth estimation step (S14) of estimating the azimuth based on the distance between the protection members obtained in the distance calculation step, and includes: In the power profile acquisition step, a power profile in which the received power corresponding to the reflected waves from two or more different azimuths and the distance between the protection members are associated is acquired for each azimuth. In the power calculation step, a first received power corresponding to the superimposed reflected wave received from at least the first direction among two or more directions is obtained, and a second received power corresponding to the superimposed reflected wave received from a second direction different from the first direction among two or more directions is obtained. In the distance calculation step, the distance between the protection members is obtained based on the first received power, the second received power, and the power profile.

[0011] In this way, if the configuration is such that the distance between the protection members is obtained and the direction is estimated based on the obtained distance between the protection members, the direction-dependent error can be suppressed as compared with the case where the direction is estimated without considering the distance between the protection members.

[0012] Note that the reference numerals in parentheses attached to each component etc. indicate an example of the correspondence relationship between the component etc. and the specific components etc. described in the embodiments described later.

Brief Description of Drawings

[0013]

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Mode for Carrying Out the Invention

[0014] An embodiment of the present disclosure will be described with reference to FIGS. 1 to 17. In the present embodiment, an example in which the azimuth estimation device and the azimuth estimation method of the present disclosure are applied to a radar device 1 mounted on a vehicle to detect various targets existing around the vehicle will be described.

[0015] The radar device 1 is disposed, for example, inside the front part components of a vehicle, emits radio waves toward the front of the vehicle, and receives radio waves reflected by a target in front of the vehicle, thereby obtaining the distance to the target, the relative speed with respect to the host vehicle, the azimuth with respect to the host vehicle, and the like. In the present embodiment, an example will be described in which the radar device 1 is disposed inside a bumper B described later so as not to be directly exposed to the outside and is protected by the bumper B. The bumper B corresponds to a protective member. Note that the protective member is not limited to the bumper B, and may be a member different from the bumper B, such as a grille.

[0016] The FMCW method is adopted as the signal modulation method of the radar device 1. The operating frequency of the radio waves of the radar device 1 is set to a frequency band corresponding to millimeter waves (for example, 76.5 GHz). Note that the operating frequency of the radio waves transmitted and received by the radar device 1 is not limited to the frequency corresponding to millimeter waves, and may be a frequency other than millimeter waves.

[0017] As shown in FIG. 1, the radar device 1 includes a transmission unit 10, a reception unit 20, and a control unit 30. The transmission unit 10 includes an oscillation unit 11 and a modulation unit 12, and causes a transmission wave to be transmitted from a transmission antenna 13. The reception unit 20 uses a plurality of reception antennas 21 to receive a reflected wave obtained by reflecting the transmission wave by a target after passing through the bumper B. The reception unit 20 converts the signal received by the reception antenna 21 into a reception signal X in a desired form by processing the signal with an MMIC 22. Note that “MMIC” is an abbreviation for Monolithic Microwave Integrated Circuit.

[0018] The control unit 30 constitutes the electronic control unit in the radar device 1. The radar device 1 is a microcomputer including a processor 31 and a storage unit 32. The storage unit 32 includes, for example, ROM, RAM, and EEPROM. Various functions of the microcomputer are realized by executing a computer program stored in the storage unit 32. In this example, the storage unit 32 corresponds to a non-transitory tangible recording medium storing the computer program. Part or all of the functions executed by the processor 31 may be realized by a hardware circuit.

[0019] The processor 31 of this embodiment includes an FFT processing unit 311, a peak extraction unit 312, a power calculation unit 313, a bumper-to-bumper distance calculation unit 314, an array correction unit 315, and a direction estimation unit 316 shown in FIG. 2. Further, the storage unit 32 of this embodiment includes a calibration matrix storage unit 321 and a power profile storage unit 322 shown in FIG. 2.

[0020] When receiving a reflected wave, the FFT processing unit 311 performs frequency analysis on the received signal X corresponding to the reflected wave by FFT. The peak extraction unit 312 obtains the peak of the frequency of the received signal X from the result of the frequency analysis performed by the FFT processing unit 311 on the received signal X. The power calculation unit 313 calculates the received power corresponding to the received signal X from the peak of the frequency obtained by the peak extraction unit 312. The power profile storage unit 322 stores information on a power profile, which will be described later, that associates the received power calculated by the power calculation unit 313 with the positional relationship between the radar device 1.

[0021] The bumper distance calculation unit 314 calculates the bumper distance d, which is the distance between the radar device 1 and the bumper B, based on the received power calculated by the power calculation unit 313 and the power profile stored in the power profile storage unit 322. The calibration matrix storage unit 321 stores the calibration matrix Q corresponding to the bumper distance d calculated by the bumper distance calculation unit 314. The array correction unit 315 corrects the mode vector based on the calibration matrix Q stored in the calibration matrix storage unit 321 to obtain a corrected mode vector. The azimuth estimation unit 316 estimates the azimuth of the target reflecting the reflected wave with respect to the host vehicle using the corrected mode vector obtained by the array correction unit 315 and the received signal X corresponding to the reflected wave. The bumper distance d corresponds to the distance between the protection members. Further, the bumper distance calculation unit 314 corresponds to the distance calculation unit.

[0022] In the present embodiment, the processor 31 functions as the FFT processing unit 311, the peak extraction unit 312, the power calculation unit 313, the bumper distance calculation unit 314, the array correction unit 315, and the azimuth estimation unit 316 by executing the computer program stored in the storage unit 32. Alternatively, the processor 31 may include a plurality of circuit modules corresponding to the FFT processing unit 311, the peak extraction unit 312, the power calculation unit 313, the bumper distance calculation unit 314, the array correction unit 315, and the azimuth estimation unit 316, respectively. Further, the storage unit 32 functions as the calibration matrix storage unit 321 and the power profile storage unit 322.

[0023] Hereinafter, the processes executed by the FFT processing unit 311, the peak extraction unit 312, the power calculation unit 313, the bumper distance calculation unit 314, the array correction unit 315, the azimuth estimation unit 316, the power profile storage unit 322, and the calibration matrix storage unit 321 will be described as processes executed by the control unit 30.

[0024] The control unit 30 of the present embodiment corrects the mode vector indicating the phase corresponding to the arrival angle of the reflected wave by the processor 31, and estimates the azimuth using the corrected mode vector, which is the correction result of the mode vector, and the received signal X corresponding to the reflected wave.

[0025] The radar device 1 of this embodiment is configured as a SIMO radar having one transmitting antenna 13. Note that the radar device 1 may be configured as a MIMO radar or a MISO radar having a plurality of transmitting antennas 13. Note that SIMO is an abbreviation for Single Input Multiple Output. MIMO is an abbreviation for Multiple Input Single Output. MISO is an abbreviation for Single Input Multiple Output. Note that a MIMO radar having m transmitting antennas 13 and n receiving antennas 21 can be treated as an equivalent array antenna to a SIMO radar having m×n receiving antennas 21. Also, a MISO radar having m transmitting antennas 13 and one receiving antenna 21 can be treated as an equivalent array antenna to a SIMO radar having m receiving antennas 21.

[0026] Based on the reception result of the signal in the receiving unit 20, the radar device 1 executes a target detection process for estimating the distance to the target, the speed of the target, and the azimuth of the target by the control unit 30. Hereinafter, the target detection process executed by the control unit 30 will be described with reference to FIG. 3. The process shown in FIG. 3 is executed periodically or irregularly by the control unit 30 when a chirp signal is transmitted from the transmitting antenna 13 at a predetermined transmission cycle.

[0027] As shown in FIG. 3, when the reflected waves from the target are received by the plurality of receiving antennas 21, the control unit 30 acquires, in step S10, the received signal X when the reflected waves from the target are received by the plurality of receiving antennas 21 from the receiving unit 20.

[0028] For example, as shown in FIG. 4, the receiving unit 20 of the radar device 1 has a linear array having L receiving antennas 21 (element positions d 1、 d2, ··· d L) is assumed to be composed of. In this case, the received signal X at each receiving antenna 21 is not an ideal signal, and may include various array errors such as inter-element mutual coupling, errors due to variations in characteristics (amplitude, phase) for each antenna element, and errors due to the position of the antenna element. The received signal X including such array errors can be modeled, for example, by the mathematical formula F10 in FIG. 5. Note that in the mathematical formula F10, the received signal X is denoted as "X(t)".

[0029] Here, "T" in the mathematical formulas F10 to F13, F15 indicates transpose. "s(t)" in the mathematical formula F12 is a signal vector indicating the complex amplitudes of each of the K incoming waves. "n(t)" in the mathematical formulas F11, F13 is a noise vector composed of noise components with an average of "0" and a variance of thermal noise power at each antenna element. "a(θ K )" is an ideal mode vector corresponding to the K-th incoming wave, and "A" is a mode matrix with "a(θ K )" as columns. The mode vector is a vector indicating the phase corresponding to the arrival angle of the reflected wave. Note that "λ" is the wavelength.

[0030] Also, "Q" in the mathematical formulas F11, F16 is a matrix indicating an error model in the case of including various array errors. In the present embodiment, the matrix indicating the error model is used as a calibration matrix Q for correcting the ideal mode vector.

[0031] When the received signal X is acquired from the receiving unit 20, the control unit 30 performs FFT processing in step S11. The control unit 30 obtains the distance to the target by performing frequency analysis on the received signal X by FFT. Also, the control unit 30 performs FFT for each beat frequency component by FFT to obtain the Doppler frequency and obtains the relative speed of the target based on the Doppler frequency. Note that FFT is an abbreviation for Fast Fourier Transform.

[0032] Subsequently, the control unit 30 performs FFT peak processing in step S12. For example, the control unit 30 detects a frequency bin where a peak occurs in an RV map composed of the distance and speed obtained by the FFT processing.

[0033] Subsequently, the control unit 30 performs array correction processing in step S13. The array correction processing is a process of correcting an ideal mode vector to obtain a corrected mode vector that takes into account various array errors and the like. In the array correction processing, the ideal mode vector "a(θ)" is corrected using a calibration matrix Q to obtain a corrected mode vector "am(θ)".

[0034] Subsequently, the control unit 30 performs azimuth estimation processing in step S14. In the present embodiment, the azimuth estimation processing corresponds to an "azimuth estimation step" of estimating the azimuth using the corrected mode vector and the received signal X.

[0035] Specifically, in the azimuth estimation processing, based on the received signal X, a correlation matrix R shown by Equation F17 in FIG. 5 XX is obtained. Then, the control unit 30 obtains a noise subspace U shown by Equation F18 in FIG. 5 from the eigenvalue decomposition of the correlation matrix R XX . Note that "T" in Equation F17 is not a transpose but the number of snapshots. N After that, the control unit 30 estimates the azimuth by the MUSIC method shown by Equation F19 in FIG. 5 using the relationship that the noise subspace U

[0036] is orthogonal to the corrected mode vector "am(θk)" corrected by the calibration matrix Q (i.e., am(θk) ⊥ U N : k = 1, 2, ··· K). In this MUSIC method, when θ = θk, the denominator of Equation F19 approaches zero, so it becomes a very large value. By detecting this peak value, the arrival angle of the reflected wave is estimated as the azimuth of the target. Note that in the present embodiment, the azimuth is estimated by the MUSIC method, but the azimuth estimation is not limited to the MUSIC method and may be realized by other methods such as DBF, Capon, and MODE. N

[0037] ​ Here, an example of a measurement system for obtaining the calibration matrix Q will be described with reference to FIG. 6. In the measurement system for obtaining the calibration matrix Q, for example, as shown in FIG. 6, a calibration device 40, a rotator 50 for rotating the calibration device 40, and a corner reflector 60 serving as a target are used.

[0038] The calibration device 40 is a device having the same functions as the radar device 1. Note that as the calibration device 40, a device having the same functions as another radar device 1 different from the radar device 1 may be employed, or the radar device 1 itself may be employed.

[0039] In the measurement system for obtaining the calibration matrix Q, by rotating the calibration device 40 to a predetermined angle using the rotator 50, the arrival angle θ of the reflected wave from the corner reflector 60 is set, and the received signal X at that time can be measured by the calibration device 40. When obtaining the calibration matrix Q using such a measurement system, within the field angle range of the receiving unit 20, the calibration device 40 is rotated at a predetermined angle step, and the received signal X measured each time is stored as received data in the memory of the calibration device 40. Then, the calibration device 40 obtains the calibration matrix Q based on the received data stored in the memory.

[0040] There are various methods for obtaining the calibration matrix Q. For example, there is a method of obtaining the calibration matrix Q using the received signal Xmeans received from a known arrival angle, which is a known arrival angle, or the signal subspace U obtained from the eigenvalue decomposition of the received signal Xmeans S and the ideal mode vector determined by the known arrival angle. Also, there is a method of obtaining the calibration matrix Q using the noise subspace U obtained from the eigenvalue decomposition of the received signal Xmeans received from a known arrival angle, which is a known arrival angle N and the ideal mode vector determined by the known arrival angle. Note that the received signal Xmeans is the average of the actual received signal X over a predetermined number of snapshots.

[0041] Incidentally, when the radar device 1 is installed inside the bumper B of a vehicle, which is a protective member, as in the present embodiment, the transmitted wave from the radar device 1 and the reflected wave reflected by the target may be refracted or reflected by the bumper B shown in FIG. 7. Further, a part of the reflected wave reflected by the target may not be received by the radar device 1 but be reflected by the radar device 1 and then reflected by the inner surface of the bumper B. In this case, the radar device 1 receives a reflected wave in which the reflected wave reflected by the target and the reflected wave reflected by the bumper B overlap. Due to these effects, azimuth-dependent errors such as errors in the amplitude and phase of the received signal X and mutual coupling errors between antennas may occur.

[0042] As a result of intensive studies by the inventors, it has been found that the azimuth-dependent error due to the presence of the bumper B between the radar device 1 and the target changes according to the bumper-to-bumper distance d. Therefore, when performing array correction processing using the calibration matrix Q as in the present embodiment, it is desirable to use a calibration matrix Q that takes into account the bumper-to-bumper distance d.

[0043] However, when installing the radar device 1 inside the bumper B, the installation position of the radar device 1 may deviate from the designed position due to manufacturing errors or the like. Then, this bumper-to-bumper distance d will be different from the designed value. Therefore, in order to use the calibration matrix Q that takes into account the bumper-to-bumper distance d, it is necessary to accurately measure the actual measured value of the bumper-to-bumper distance d after the radar device 1 is actually installed inside the bumper B. And it is desirable to perform array correction processing using the calibration matrix Q based on the actually measured value of the bumper-to-bumper distance d.

[0044] Therefore, the inventors considered calculating the received power corresponding to the received signal X according to the reflected wave when the radar device 1 receives a reflected wave in which the reflected wave reflected by the target and the reflected wave reflected by the bumper B overlap, and obtaining the actual measured value of the bumper-to-bumper distance d based on the calculated power. And they considered performing array correction processing using the calibration matrix Q based on the actually measured value of the bumper-to-bumper distance d obtained in this way. Hereinafter, a reflected wave in which the reflected wave reflected by the target and the reflected wave reflected by the bumper B overlap is referred to as a superimposed reflected wave.

[0045] However, as a result of the inventors' intensive studies, it has been found that the received power corresponding to the received signal X of the superimposed reflected wave periodically changes its power value according to the bumper-to-bumper distance d. And it has been found that the received power corresponding to the received signal X of the superimposed reflected wave that changes periodically has a changing period length, that is, the interval until the power values become equal when the power values repeatedly increase and decrease. Also, it has been found that the received power corresponding to the received signal X of the superimposed reflected wave changes its power value according to the direction in which this superimposed reflected wave is received. For this reason, it is difficult to accurately measure the actually measured value of the bumper-to-bumper distance d after the radar device 1 is actually attached to the vehicle only by obtaining the power value of the received power corresponding to the received signal X of the superimposed reflected wave. Hereinafter, the period length of the received power corresponding to the received signal X of the superimposed reflected wave that changes periodically is also referred to as the wavelength of the received power value.

[0046] Here, as shown in FIG. 7, an example of the calculation result of the received power corresponding to the received signal X when the radar device 1 receives the superimposed reflected wave is shown in FIG. 8. The bumper B when obtaining the calculation result shown in FIG. 8 has a bent portion B10 formed by bending at a portion facing the front of the transmission antenna 13 of the radar device 1, as shown in FIG. 9. In the present embodiment, the radar device 1 is arranged so that the transmitted wave transmitted from the radar device 1 passes through the bent portion B10.

[0047] The curvature of the bent portion B10 of the present embodiment is formed to be smaller than the value obtained by dividing the integer "1" by the bumper-to-bumper distance d. That is, as shown in FIG. 9, when a circle having a radius R of the same length as the bumper-to-bumper distance d is defined as a virtual circle C, the curvature of the cross section of the bent portion B10 is larger than "1 / R". Also, the bumper B is positioned at a position where the error between the designed value of the bumper-to-bumper distance d and the actual bumper-to-bumper distance d is 1 / 4 or less of the wavelength of the reflected wave. Note that the wavelength of the reflected wave is the wavelength of the transmitted wave transmitted from the transmission antenna 13.

[0048] Figure 7 is a plan view, and the arrival angle θ is an angle in the horizontal direction. Also, the arrival angle θ of the reflected wave in the direction orthogonal to the front of the radar device 1 is set to zero. And the distance between the radar device 1 and the bumper B in the direction orthogonal to the front of the radar device 1 when the arrival angle θ is zero is the bumper-to-bumper distance d. Also, the distance between the radar device 1 and the bumper B when the radar device 1 is rotated by the rotor 50 to change the arrival angle θ is obtained by d(θ)=d / cosθ.

[0049] In addition, in FIG. 7, in order to make the positional relationship between the radar device 1 and the corner reflector 60 easier to understand, the arrival angle θ is illustrated by changing the position of the corner reflector 60, but the arrival angle θ is set according to the rotational position of the rotor 50.

[0050] Also, in FIG. 8, the change in the received power when the arrival angle θ is 0° is indicated by a circle, the change in the received power when the arrival angle θ is 30° is indicated by a triangle, and the change in the received power when the arrival angle θ is 45° is indicated by a square.

[0051] As shown in FIG. 8, the wavelength of the received power when the arrival angle θ is set to 0° becomes the smallest, and as the arrival angle θ increases, the wavelength of the received power becomes longer. Specifically, the wavelength of the received power when the arrival angle θ was set to 0° was 1.96 mm. Also, the wavelength of the received power when the arrival angle θ was set to 30° was 2.26 mm. And the wavelength of the received power when the arrival angle θ was set to 45° was 2.77 mm.

[0052] Thus, the received power corresponding to the received signal X of the superimposed reflected wave changes periodically in power value according to the bumper-to-bumper distance d, and the wavelength of the periodically changing received power also changes. Also, the received power corresponding to the received signal X of the superimposed reflected wave has different power values according to the arrival angle θ.

[0053] Hereinafter, information in which the bumper distance d as shown in FIG. 8 and the received power of the received signal X corresponding to the arrival angle θ of the overlapping reflected wave when the radar device 1 receives the overlapping reflected wave are associated is called a power profile. The power profile varies depending on the characteristics of each linear array of the receiving antenna 21 of the radar device 1, and indicates the unique characteristics of each radar device 1. That is, the power profiles may be different for each radar device 1 attached to the bumper B.

[0054] By the way, as shown in FIG. 8, the larger the arrival angle θ, the smaller the received power tends to be. However, since the received power changes periodically, even when the arrival angles θ are different, the received powers may be equal depending on the bumper distance d. Therefore, it is difficult to accurately obtain the measured value of the bumper distance d after the radar device 1 is attached to the bumper B only from the power value of the received power.

[0055] Therefore, in the measurement system and the like for obtaining the calibration matrix Q of the present embodiment, the radar device 1 is arranged inside the bumper B so that the bumper distance d is a known distance, and the calibration matrix Q and the power profile are obtained based on the received signal X of the overlapping reflected wave. Then, the azimuth estimation device obtains the measured value of the bumper distance d when the radar device 1 is actually attached to the vehicle based on the obtained power profile, and performs array correction based on the obtained bumper distance d.

[0056] Hereinafter, the calibration process for obtaining the calibration matrix Q and the power profile of the present embodiment will be described with reference to FIG. 10. This calibration process uses the radar device 1, the rotator 50, and the corner reflector 60. Then, using these radar device 1, rotator 50, and corner reflector 60, the calibration process shown in FIG. 10 is performed. The calibration process is performed before the radar device 1 is actually attached to the vehicle.

[0057] The radar device 1 used for calibration processing employs the actual radar device 1 mounted on the vehicle itself. This is because there may be differences in the respective unique characteristics of the radar devices 1. However, when having characteristics equivalent to those of the radar device 1 actually mounted on the vehicle, the radar device 1 used for calibration processing may employ a radar device 1 different from the radar device 1 actually mounted on the vehicle. Alternatively, as the radar device 1 used for calibration processing, a calibration device having functions and characteristics equivalent to those of the radar device 1 actually mounted on the vehicle may be employed.

[0058] In the calibration process, as shown in FIG. 10, in the first step S20, the radar device 1 is arranged inside the bumper B so that the bumper-to-bumper distance d becomes a known distance. Specifically, the radar device 1 is arranged so that the bumper-to-bumper distance d becomes the minimum distance d min This minimum distance d min is set to a value that is assumed to be the smallest bumper-to-bumper distance d when the radar device 1 is installed inside the bumper B, for example. Suppose the design value of the bumper-to-bumper distance d when the radar device 1 is attached to the bumper B is 15 mm, and there is a possibility that the bumper-to-bumper distance d deviates within the range of 10 mm to 20 mm due to factors such as manufacturing errors. In this case, the minimum distance d min is 10 mm.

[0059] Then, in step S21, the corner reflector 60 is arranged outside the bumper B so that the reflector distance, which is the distance between the radar device 1 and the corner reflector 60, becomes a predetermined design distance Y. This design distance Y is set to, for example, 5 m based on the radar cross-section (i.e., RCS), which indicates characteristics such as the reflection intensity when the corner reflector 60 reflects the transmitted wave from the radar device 1. The design distance Y is set so that when the radar device 1 receives the reflected wave from the corner reflector 60, the received power becomes a relatively large value.

[0060] Next, in step S22, from the perspective of the corner reflector 60, the angle of the corner reflector 60 is set so that the angle with respect to the front of the radar device 1 is a known angle. Specifically, the arrival angle θ is the minimum angle θ min and the angle of the corner reflector 60 is set accordingly. The minimum angle θ min is set, for example, to the smallest angle in the target viewing angle of the radar device 1. If the target viewing angle of the radar device 1 is -70° to +70°, the minimum angle θ min is -70°.

[0061] Next, in step S23, the radar device 1 transmits a transmission wave from the transmission antenna 13 toward the corner reflector 60 and measures the received power when the superimposed reflected wave is received. Specifically, the control unit 30 causes the transmission antenna 13 to transmit a chirp signal at a predetermined transmission period. Then, the radar device 1 receives, with the plurality of reception antennas 21, the superimposed reflected wave in which the reflected wave reflected by the corner reflector 60 and the reflected wave that has been reflected by the surface of the radar device 1 after being reflected by the corner reflector 60 and then further reflected by the inner surface of the bumper B overlap. The control unit 30 acquires the reception signal X when the superimposed reflected wave is received by the plurality of reception antennas 21 from the reception unit 20.

[0062] When the reception signal X is acquired from the reception unit 20, the FFT processing unit 311 of the control unit 30 performs FFT processing. Then, the peak extraction unit 312 of the control unit 30 performs FFT peak processing to detect the frequency at which a peak occurs. When the frequency at which a peak occurs is acquired, the power calculation unit 313 of the control unit 30 calculates the received power from the signal at the peak frequency and transmits information on the calculated power value of the received power to the calibration matrix storage unit 321 and the power profile storage unit 322.

[0063] In step S24, the calibration matrix storage unit 321 stores the information on the power value received from the power calculation unit 313, which is the measurement result, as calibration matrix data by associating it with the bumper distance d set in step S20 and the arrival angle θ set in step S22.

[0064] The power profile storage unit 322 associates the information on the power value received from the power calculation unit 313, which is the measurement result, with the bumper-to-bumper distance d set in step S20, the reflector distance set in step S21, and the arrival angle θ set in step S22, and stores it as power profile data. In the present embodiment, the process of step S24 corresponds to the "power profile acquisition step".

[0065] Then, in step S25, the control unit 30 determines whether or not the arrival angle θ is greater than or equal to the maximum angle θ max . The maximum angle θ max is set to the largest value in the target viewing angle of the radar device 1 described above. That is, when the target viewing angle of the radar device 1 is -70° to +70°, the maximum angle θ max is +70°.

[0066] When it is determined that the arrival angle θ is greater than or equal to the maximum angle θ max , the control unit 30 proceeds to the process of step S27. On the other hand, when it is not determined that the arrival angle θ is greater than or equal to the maximum angle θ max , in step S26, the rotor 50 is rotated to increase the arrival angle θ by a change angle Δθ, which is a known angle predetermined from the arrival angle θ set in step S22. Here, the process of step S26 is a process necessary for obtaining the calibration matrix Q when the array correction unit 315 performs array correction. The smaller the change angle Δθ, the smaller the azimuth error of each azimuth estimated by the azimuth estimation unit 316 using the calibration matrix Q can be. For this reason, this change angle Δθ is set to an angle, such as 1°, that can further suppress the azimuth error of each azimuth estimated by the azimuth estimation unit 316.

[0067] Then, the control unit 30 re-executes the processes of steps S23 to S25 in a state where the arrival angle θ is increased by the change angle Δθ from the arrival angle θ set in step S22. The control unit 30 repeatedly executes the processes of steps S23 to S26 until the arrival angle θ becomes greater than or equal to the maximum angle θ max . The arrival angle θ is set to the minimum angle θmin from the maximum angle θ max change it by the change angle Δθ up to, and each time store the calibration matrix data based on the received signal X received at that time in the calibration matrix storage unit 321. Also, change the arrival angle θ by the change angle Δθ from the minimum angle θ min to the maximum angle θ max and each time store the power profile data based on the received signal X received at that time in the power profile storage unit 322.

[0068] When the arrival angle θ becomes the maximum angle θ max or more, in step S27, the control unit 30 determines whether or not the bumper - to - bumper distance d is the maximum distance d max or more. The maximum distance d max is set to a value assumed to be the maximum bumper - to - bumper distance d when the radar device 1 is installed inside the bumper B. As described above, when there is a position where the bumper - to - bumper distance d deviates within the range of 10 mm to 20 mm due to factors such as manufacturing errors, the maximum distance d max is 20 mm.

[0069] When it is determined that the bumper - to - bumper distance d is not the maximum distance d max or more, in step S28, increase the bumper - to - bumper distance d by a change distance Δd which is a known distance predetermined from the bumper - to - bumper distance d set in step S20. This change distance Δd is set to a distance such as 0.5 mm that can accurately measure the bumper - to - bumper distance d.

[0070] Then, in the state where the control unit 30 has increased the bumper - to - bumper distance d by the change distance Δd from the minimum distance d min execute the processes of steps S22 to S27 again. The control unit 30 repeatedly executes the processes of steps S22 to S28 until the bumper - to - bumper distance d becomes the maximum distance d max or more. And, from the minimum distance d min to the maximum distance d maxThe change distance Δd is changed step by step, and the calibration matrix data based on the received signal X received each time is stored in the calibration matrix storage unit 321. Also, the bumper-to-bumper distance d is changed from the minimum distance d min to the maximum distance d max step by step by the change distance Δd, and the power profile data based on the received signal X received each time is stored in the power profile storage unit 322. When the bumper-to-bumper distance d becomes the maximum distance d max or more, the control unit 30 ends the calibration process.

[0071] The calibration matrix Q of this embodiment is obtained based on the calibration matrix data obtained by changing the bumper-to-bumper distance d from the minimum distance d min to the maximum distance d max in this way. And the obtained calibration matrix Q is based on the bumper-to-bumper distance d. Hereinafter, the calibration matrix obtained according to the bumper-to-bumper distance d is denoted as the calibration matrix (Q, θ). The calibration matrix (Q, θ) is stored in the calibration matrix storage unit 321.

[0072] Also, by this calibration process, information on the power profile indicating the characteristics of the radar device 1 as shown in FIG. 8 is stored in the power profile storage unit 322. The power profile is information in which information on the bumper-to-bumper distance d before the radar device 1 is actually mounted on the vehicle, information on the arrival angle θ, and information on the power value of the received power of the overlapping reflected wave are linked. And the power profile is information indicating the change in the power value of the received signal X when the bumper-to-bumper distance d and the arrival angle θ are changed.

[0073] Also, by this calibration process, in the power profile storage unit 322, power profiles in which the received power corresponding to the received waves from a plurality of arrival angles θ that are two or more different azimuths are linked to the bumper-to-bumper distance d are stored for each arrival angle θ. Also, in the power profile storage unit 322, a power profile in which the received power of the overlapping reflected wave including the reflected wave reflected by the bent portion B10 of the bumper B positioned at a position where the error between the designed value of the bumper-to-bumper distance d and the actual bumper-to-bumper distance d is 1 / 4 or less of the wavelength of the transmitted wave is linked to the bumper-to-bumper distance d is stored.

[0074] Subsequently, measurement processing for measuring the bumper-to-bumper distance d after the radar device 1 and the bumper B are actually attached to the vehicle will be described with reference to FIG. 11. In the measurement processing, as shown in FIG. 11, in the first step S30, the radar device 1 is arranged inside the bumper B so that the bumper-to-bumper distance d becomes the design value d s . The mounting position when arranging the radar device 1 includes errors such as manufacturing errors when the radar device 1 is mounted inside the bumper B.

[0075] Then, in step S31, the corner reflector 60 is arranged outside the bumper B so that the reflector distance becomes the predetermined design distance Y. This design distance Y is set to the same value as the design distance Y in step S21 in the calibration process, for example. Thereby, in step S38 described later, it becomes easier to compare the power value of the received signal X calculated in the calibration process with the power value of the received signal X calculated in the measurement process.

[0076] Note that if it is possible to compare the power value of the received signal X calculated in the calibration process with the power value of the received signal X calculated in the measurement process using the radar cross-sectional area, the design distance Y in the measurement process may be set to a value different from the design distance Y in the calibration process.

[0077] Subsequently, in step S32, the corner reflector 60 is arranged at a position where the arrival angle θ becomes the first measurement angle θ1. That is, the corner reflector 60 is arranged so that the angle with respect to the front of the radar device 1 as viewed from the corner reflector 60 becomes the first measurement angle θ1.

[0078] The first measurement angle θ1 is set to the same value as any one of the arrival angles θ set in the process of step S22 repeatedly executed in the calibration process. That is, the first measurement angle θ1 is set to the same value as any one of the target viewing angles of the radar device 1 set in the calibration process. In the process of step S32, for example, the corner reflector 60 is arranged in front of the radar device 1 attached to the vehicle, and the corner reflector 60 is arranged so that the first measurement angle θ1 becomes 0°.

[0079] Note that the first measurement angle θ1 is not limited to 0°, and the corner reflector 60 may be arranged so as to have an angle different from 0°. The first measurement angle θ1 set in step S32 corresponds to the first azimuth.

[0080] Subsequently, in step S33, the radar device 1 transmits a transmission wave from the transmission antenna 13 toward the corner reflector 60 and measures the received power when the superimposed reflected wave is received. Specifically, the control unit 30 executes the same process as step S23 in the calibration process, and the power calculation unit 313 calculates the power value of the received signal X corresponding to the superimposed reflected wave. The control unit 30 transmits the information on the power value of the received power calculated by the power calculation unit 313 to the bumper-to-bumper distance calculation unit 314. The received power measured in step S33 corresponds to the first received power.

[0081] In step S34, the bumper-to-bumper distance calculation unit 314 stores the received power value information in association with the bumper-to-bumper distance d set in step S30, the reflector distance set in step S31, and the first measurement angle θ1 set in step S32.

[0082] Subsequently, in step S35, the corner reflector 60 is arranged at a position where the arrival angle θ becomes the second measurement angle θ2. That is, the corner reflector 60 is arranged so that the angle with respect to the front of the radar device 1 as viewed from the corner reflector 60 becomes the second measurement angle θ2.

[0083] The second measurement angle θ2 is set to any one value different from the first measurement angle θ1 among the arrival angles θ set in the process of step S22 repeatedly executed in the calibration process. That is, the second measurement angle θ2 is set to the same value as any one value different from the first measurement angle θ1 among the viewing angles of the target of the radar device 1 set in the calibration process. In the process of step S35, for example, the corner reflector 60 is arranged so that the arrival angle θ becomes the second measurement angle θ2 by changing the position of the corner reflector 60 with respect to the vehicle to which the radar device 1 is attached. The second measurement angle θ2 set in step S35 corresponds to the second azimuth.

[0084] Subsequently, in step S36, the radar device 1 calculates the power value of the received signal X corresponding to the superimposed reflected wave by executing the same process as in step S33. That is, the radar device 1 calculates the power value of the received signal X corresponding to the superimposed reflected wave when the arrival angle θ is set to the second measurement angle θ2 by the power calculation unit 313. The control unit 30 transmits the information on the power value of the received power calculated by the power calculation unit 313 to the bumper-to-bumper distance calculation unit 314. The received power measured in step S36 corresponds to the second received power. Also, in the present embodiment, the processes of step S33 and step S36 correspond to the "power calculation step".

[0085] In step S37, the bumper-to-bumper distance calculation unit 314 stores the received power value information in association with the bumper-to-bumper distance d set in step S30, the reflector distance set in step S31, and the second measurement angle θ2 set in step S35.

[0086] Subsequently, in step S38, the control unit 30 calculates the bumper-to-bumper distance d based on the power profile stored in the power profile storage unit 322 by the bumper-to-bumper distance calculation unit 314 and the power values of the received power calculated in steps S34 and S37, respectively. Specifically, the control unit 30 calculates the bumper-to-bumper distance d based on the power profile stored in the power profile storage unit 322, the received power corresponding to the superimposed reflected wave when the arrival angle θ is set to the first measurement angle θ1, and the received power corresponding to the superimposed reflected wave when the arrival angle θ is set to the second measurement angle θ2.

[0087] The method for calculating the bumper-to-bumper distance d calculated based on the power profile and the received power will be described with reference to FIGS. 12 and 13. FIG. 12 shows the simulation results of the waveforms of the normalized bumper-to-bumper distance d and the normalized received power when the arrival angle θ is set to 0°, 30°, 45°, 60°, and 75°, respectively. Also, in FIG. 12, the simulation results of the bumper-to-bumper distance d and the received power when the arrival angle θ is set to 0° are shown by a solid line, and the simulation results of the bumper-to-bumper distance d and the received power when the arrival angle θ is set to 30° are shown by a dashed line. Further, the simulation results of the bumper-to-bumper distance d and the received power when the arrival angle θ is set to 45° are shown by a dashed line with a larger interval than when the arrival angle θ is set to 30°. Then, the simulation results of the bumper-to-bumper distance d and the received power when the arrival angle θ is set to 60° are shown by a one-dot chain line, and the simulation results of the bumper-to-bumper distance d and the received power when the arrival angle θ is set to 75° are shown by a two-dot chain line.

[0088] As described above, the received power corresponding to the received signal X of the superimposed reflected wave changes periodically according to the bumper-to-bumper distance d. For this reason, as shown in FIG. 12, for example, when the arrival angle θ is set to 0°, if the received power is the power value E1, there are two candidates for the bumper-to-bumper distance d, which are the distance D1 and the distance D2. Also, when the arrival angle θ is set to 0°, if the received power is the power value E2, there are two candidates for the bumper-to-bumper distance d, which are the distance D3 and the distance D4. Thus, when there are two candidates for the bumper-to-bumper distance d, the bumper-to-bumper distance calculation unit 314 cannot accurately obtain the bumper-to-bumper distance d based on only the information of one power profile calculated with the arrival angle θ set to 0°.

[0089] However, while the received power corresponding to the received signal X of the superimposed reflected wave has its power value changing periodically depending on the arrival angle θ, according to the inventors' intensive studies, the wavelength of this periodically changing received power changes according to the arrival angle θ. For example, as in this embodiment, when the curvature of the cross section of the bent portion B10 of the bumper B is greater than 1 / R, the wavelength of the periodically changing received power increases as the arrival angle θ increases. Specifically, when the curvature of the cross section of the bent portion B10 of the bumper B is greater than 1 / R, the wavelength of the received power increases as the arrival angle θ moves away from 0°. For this reason, the power profiles obtained by setting the arrival angle θ to different values from each other will be shifted from each other without the waveforms of their respective power values overlapping.

[0090] For this reason, even when there are two candidates for the bumper-to-bumper distance d obtained from the power values of the power profile obtained by setting the arrival angle θ to a certain angle, the bumper-to-bumper distance calculation unit 314 can narrow down the two candidates for the bumper-to-bumper distance d to one candidate based on the power values of the power profile obtained from the arrival angle θ set to an angle different from the set angle.

[0091] For example, as shown in FIG. 13, when the reception power corresponding to the reception signal X of the superimposed reflected wave received with the arrival angle θ set to 0° is the power value E1, there are two bumper distances d obtained from the power profile, namely the distance D1 and the distance D2. In such a case, when the reception power corresponding to the reception signal X of the superimposed reflected wave received with the arrival angle θ set to 45° is the power value E3, or approximates the power value E3, the bumper distance calculation unit 314 determines that the bumper distance d is the distance D2. On the other hand, when the reception power corresponding to the reception signal X of the superimposed reflected wave received with the arrival angle θ set to 45° is the power value E4, or approximates the power value E4, the bumper distance calculation unit 314 determines that the bumper distance d is the distance D1.

[0092] Therefore, the bumper distance calculation unit 314 can accurately measure the bumper distance d based on the power profile obtained by setting a plurality of arrival angles θ. Then, array correction processing can be performed using the calibration matrix Q based on the accurately measured bumper distance d.

[0093] Incidentally, the relationship between the wavelength of the reception power that periodically changes in the power profile and the arrival angle θ changes according to the curvature of the cross section of the bent portion B10 of the bumper B.

[0094] For example, as shown in FIG. 14, assume that the curvature of the cross section of the bent portion B10 is the same as 1 / R. In this case, the wavelength of the reception power is constant regardless of the arrival angle θ.

[0095] Also, as shown in FIG. 15, assume that the curvature of the cross section of the bent portion B10 is smaller than 1 / R. In this case, as shown in FIG. 16, the wavelength of the reception power becomes smaller as the arrival angle θ deviates from 0°.

[0096] FIG. 16 shows the simulation results of the normalized bumper distance d and the normalized received power waveforms when the arrival angle θ is set to 0°, two angles different from 0°. In FIG. 16, the simulation results of the bumper distance d and the received power when the arrival angle θ is set to 0° are shown by a solid line. Also, the simulation results of the bumper distance d and the received power when the arrival angle θ is set to a first angle greater than 0° are shown by a dashed-dotted line. And the simulation results of the bumper distance d and the received power when the arrival angle θ is set to a second angle greater than the first angle are shown by a double-dashed-dotted line.

[0097] As shown in FIG. 16, for example, when the arrival angle θ is set to 0° and the received power is the power value E5, there are two candidates for the bumper distance d, which are the distance D5 and the distance D6. And when the curvature of the cross-section of the bent portion B10 is smaller than 1 / R, even when the arrival angle θ is set to a second angle different from 0°, when the bumper distance d is set to the distance D5 and the distance D6, the received power becomes the power value E5 or an approximate value of the power value E5.

[0098] Also, for example, when the arrival angle θ is set to 0° and the received power is the power value E6, there are two candidates for the bumper distance d, which are the distance D7 and the distance D8. And when the curvature of the cross-section of the bent portion B10 is smaller than 1 / R, even when the arrival angle θ is set to a second angle different from 0°, when the bumper distance d is set to the distance D7 and the distance D8, the received power becomes the power value E6 or an approximate value of the power value E6.

[0099] Thus, when the curvature of the cross-section of the bent portion B10 is smaller than 1 / R, there is a possibility that two power profiles in the case where the arrival angles θ are different from each other overlap at power values where there are two candidates for the bumper interval d. In such a case, it is difficult for the bumper interval calculation unit 314 to narrow down to one candidate from the two candidates for the bumper interval d based only on the two power profiles in the case where the arrival angles θ are different from each other. And, in order to narrow down to one candidate from the two candidates for the bumper interval d, a power profile of the superimposed reflected wave set at an angle different from each of the first angle and the second angle of the arrival angle θ is further required. In this case, since the number of required power profiles increases, it is not preferable.

[0100] Therefore, it is desirable that the radar device 1 be arranged so that the curvature of the cross-section of the bent portion B10 is larger than 1 / R as in the present embodiment. By arranging the radar device 1 so that the curvature of the cross-section of the bent portion B10 is larger than 1 / R, even when there are two candidates for the bumper interval d obtained from the power values of the power profiles, the bumper interval calculation unit 314 can narrow down to one bumper interval d from the two power profiles.

[0101] Also, the bumper B is positioned at a position where the error between the design value d s of the bumper interval d and the actual bumper interval d is equal to or less than 1 / 4 of the wavelength of the transmitted wave. For this reason, the power profile storage unit 322 stores a power profile in which the received power of the superimposed reflected wave including the reflected wave reflected by the bumper B positioned at a position where the error between the design value d s of the bumper interval d and the bumper interval d is equal to or less than 1 / 4 of the wavelength of the transmitted wave is associated with the bumper interval d.

[0102] Incidentally, the power value of the power profile changes periodically as shown in FIG. 12 and the like. Here, if it is assumed that the radar device 1 is attached to the inside of the bumper B with an error between the design value d s of the bumper interval d and the actual bumper interval d shifted by 1 / 4 of the wavelength of the transmitted wave. In this case, the actual bumper interval d is the design value d sThe waveform of the power profile in the case where it is, and the actual bumper-to-bumper distance d and the design value d s When it is attached with a deviation of 1 / 4 of the wavelength of the transmitted wave from the design value d

[0103] Also, if the error between the design value d s of the bumper-to-bumper distance d and the actual bumper-to-bumper distance d is greater than 1 / 4 of the wavelength of the transmitted wave and the radar device 1 is attached inside the bumper B. In this case, the bumper-to-bumper distance calculation unit 314 s There is a possibility that the error between the design value d

[0104] On the other hand, in the power profile storage unit 322, the received power of the superimposed reflected wave including the reflected wave reflected by the bumper B positioned at a position where the error between the design value d s and the bumper-to-bumper distance d is 1 / 4 or less of the wavelength of the transmitted wave is associated with the bumper-to-bumper distance d, and the power profile is stored. Therefore, the bumper-to-bumper distance calculation unit 314 can accurately calculate the bumper-to-bumper distance d based on the power profile stored in the power profile storage unit 322. In the present embodiment, the process of step S38 corresponds to the "distance calculation step".

[0105] Subsequently, the calibration matrix Q and the power profile obtained in the calibration process, and the array correction based on the bumper-to-bumper distance d calculated in the measurement process will be described with reference to FIG. 17.

[0106] First, in step S40, the bumper-to-bumper distance calculation unit 314 transmits the information on the bumper-to-bumper distance d obtained in the measurement process to the calibration matrix storage unit 321.

[0107] When the calibration matrix storage unit 321 acquires the information on the bumper-to-bumper distance d from the bumper-to-bumper distance calculation unit 314, in step S41, it extracts the calibration matrix Q(θ, d) corresponding to the acquired bumper-to-bumper distance d from the calibration matrix Q(θ, d) obtained by the calibration process. Then, the calibration matrix storage unit 321 outputs the information on the extracted calibration matrix (Q, d) to the array correction unit 315.

[0108] Then, in step S42, the array correction unit 315 performs array correction processing using the calibration matrix Q(θ, d) based on the bumper-to-bumper distance d acquired from the calibration matrix storage unit 321. Specifically, in step S13 shown in FIG. 3, the array correction unit 315 corrects the ideal mode vector "a(θ)" using the calibration matrix Q to obtain the corrected mode vector "am(θ)". By performing such array correction processing, it is possible to suppress the azimuth-dependent error that varies according to the bumper-to-bumper distance d of the bumper B existing between the radar device 1 and the target.

[0109] The radar device 1 described above functions as an azimuth estimation device for estimating the azimuth of a target. Also, the method for estimating the azimuth of the target described above corresponds to the azimuth estimation method of the present disclosure.

[0110] The control unit 30 of the radar device 1 according to this embodiment includes a power profile storage unit 322 that stores a power profile in which the bumper-to-bumper distance d and the received power corresponding to the superimposed reflected wave are associated, and a power calculation unit 313 that obtains the received power. Further, the control unit 30 includes a bumper-to-bumper distance calculation unit 314 that obtains the bumper-to-bumper distance d, and a direction estimation unit 316 that estimates the direction based on the bumper-to-bumper distance d. In the power profile storage unit 322, a power profile in which the received power corresponding to the superimposed reflected wave from two or more different arrival angles θ and the bumper-to-bumper distance d are associated is stored for each arrival angle θ. The power calculation unit 313 obtains the received power corresponding to the superimposed reflected wave received from the first measurement angle θ1 among two or more arrival angles θ, and also obtains the received power corresponding to the superimposed reflected wave received from a second measurement angle θ2 different from the first measurement angle θ1 among two or more arrival angles θ. The bumper-to-bumper distance calculation unit 314 obtains the bumper-to-bumper distance d based on the first received power, the second received power, and the power profile.

[0111] In this way, if the configuration is such that the bumper-to-bumper distance d is obtained and the direction is estimated based on the obtained bumper-to-bumper distance d, the direction-dependent error can be suppressed as compared with the case where the direction is estimated without considering the bumper-to-bumper distance d.

[0112] Further, according to the above embodiment, the following effects can be obtained.

[0113] (1) In the above embodiment, the first measurement angle θ1 is a direction orthogonal to the front of the transmission antenna 13. The power calculation unit 313 obtains, as the first received power, the received power corresponding to the superimposed reflected wave received from the first measurement angle θ1, which is a direction orthogonal to the front of the transmission antenna 13.

[0114] According to this, the received power is easier to obtain as compared with the case where neither the first measurement angle θ1 nor the second measurement angle θ2 is in the direction orthogonal to the front of the transmission antenna 13.

[0115] (2) In the above embodiment, in the power profile storage unit 322, the design value d of the bumper-to-bumper distance ds A power profile in which the received power corresponding to the superimposed reflected wave including the reflected wave reflected by the bumper B positioned at a position where the error from the design value d of the bumper distance d is 1 / 4 or less of the wavelength of the transmitted wave is associated with the bumper distance d is stored.

[0116] As described above, when the error between the design value d of the bumper distance d s and the actual bumper distance d deviates by more than 1 / 4 of the wavelength of the transmitted wave and the radar device 1 is mounted inside the bumper B, it is difficult for the bumper distance calculation unit 314 to accurately calculate the bumper distance d.

[0117] On the other hand, in the power profile storage unit 322, a power profile in which the received power corresponding to the superimposed reflected wave including the reflected wave reflected by the bumper B positioned at a position where the error from the design value d s is 1 / 4 or less of the wavelength of the transmitted wave is associated with the bumper distance d is stored. Therefore, the bumper distance calculation unit 314 can accurately calculate the bumper distance d based on the power profile stored in the power profile storage unit 322.

[0118] (3) In the above embodiment, the bumper B has a bent portion B10 formed by bending at a portion facing the transmission antenna 13. The curvature of the bent portion B10 is formed to be smaller than the value obtained by dividing the integer "1" by the bumper distance d. That is, the curvature of the cross section of the bent portion B10 is formed to be larger than 1 / R when a circle having a radius R of the same length as the bumper distance d is defined as the virtual circle C. In the power profile storage unit 322, a power profile in which the received power corresponding to the superimposed reflected wave including the reflected wave reflected by the bent portion B10 is associated with the bumper distance d is stored.

[0119] When the curvature of the cross-section of the bent portion B10 is 1 / R or less, there is a possibility that two power profiles when the arrival angles θ are different overlap at the power value where there are two candidates for the bumper distance d. In such a case, it is difficult for the bumper distance calculation unit 314 to narrow down to one candidate from the two candidates for the bumper distance d based only on the two power profiles when the arrival angles θ are different.

[0120] On the other hand, when the curvature of the cross-section of the bent portion B10 is greater than 1 / R, the two power profiles when the arrival angles θ are different do not overlap at the power value where there are two candidates for the bumper distance d. Therefore, the bumper distance calculation unit 314 can narrow down to one candidate from the two candidates for the bumper distance d based only on the two power profiles when the arrival angles θ are different.

[0121] (Other Embodiments) As described above, the representative embodiments of the present disclosure have been described. However, the present disclosure is not limited to the above-described embodiments and can be variously modified, for example, as follows.

[0122] In the above-described embodiment, an example has been described in which the control unit 30 calculates the bumper distance d based on the power profile stored in the power profile storage unit 322, the received power corresponding to the superimposed reflected wave when the arrival angle θ is set to the first measurement angle θ1, and the received power corresponding to the superimposed reflected wave when the arrival angle θ is set to the second measurement angle θ2. However, the present disclosure is not limited to this.

[0123] For example, in addition to the power profile stored in the power profile storage unit 322, the received power corresponding to the superimposed reflected wave when the arrival angle θ is set to the first measurement angle θ1, and the received power corresponding to the superimposed reflected wave when the arrival angle θ is set to the second measurement angle θ2, the control unit 30 may calculate the bumper distance d based on the received power corresponding to the superimposed reflected wave when the arrival angle θ is set to an angle different from the first measurement angle θ1 and the second measurement angle θ2. That is, the bumper distance d may be calculated based on the received power corresponding to the superimposed reflected waves from three or more arrival angles θ.

[0124] In the above-described embodiment, an example in which the orientation estimation apparatus and the orientation estimation method of the present disclosure are applied to the radar device 1 mounted on a vehicle to detect various targets existing around the vehicle has been described, but the present disclosure is not limited thereto. The orientation estimation apparatus and the orientation estimation method of the present disclosure are also applicable to the radar device 1 installed in devices or objects other than vehicles.

[0125] In the above-described embodiment, it goes without saying that the elements constituting the embodiment are not necessarily essential, except when it is explicitly stated that they are particularly essential and when they are considered to be clearly essential in principle.

[0126] In the above-described embodiment, when numerical values such as the number, numerical value, quantity, range, etc. of the components of the embodiment are mentioned, they are not limited to the specific number, except when it is explicitly stated that they are particularly essential and when they are clearly limited to a specific number in principle.

[0127] In the above-described embodiment, when referring to the shape, positional relationship, etc. of the components, etc., they are not limited to the shape, positional relationship, etc., except when it is explicitly stated and when they are clearly limited to a specific shape, positional relationship, etc. in principle.

[0128] The control unit 30 of the present disclosure and its method may be implemented by a dedicated computer provided by configuring a processor and a memory programmed to execute one or more functions embodied by a computer program. The control unit 30 of the present disclosure and its method may be implemented by a dedicated computer provided by configuring a processor with one or more dedicated hardware logic circuits. The control unit 30 of the present disclosure and its method may be implemented by one or more dedicated computers configured by a combination of a processor and a memory programmed to execute one or more functions and a processor configured by one or more hardware logic circuits. Further, the computer program may be stored in a computer-readable non-transitory tangible recording medium as instructions to be executed by a computer.

Explanation of Signs

[0129] 1 Radar device 13 Transmission antenna 313 Power calculation unit 314 Distance calculation unit 316 Azimuth estimation unit 322 Power profile storage unit B Protection member

Claims

1. An azimuth estimation device that estimates, as the azimuth of a target, the arrival angle of a transmission wave transmitted from a transmission antenna (13), passing through a protective member (B) of the transmission antenna, and reflected by the target, to a radar device (1), comprising: a power profile storage unit (322) that stores a power profile in which a protective member distance, which is the distance between the transmission antenna and the protective member, and received power corresponding to a superimposed reflected wave in which a reflected wave reflected by the target and a reflected wave reflected by the protective member overlap are associated; a power calculation unit (313) that obtains the received power corresponding to the superimposed reflected wave; a distance calculation unit (314) that obtains the protective member distance based on the received power obtained by the power calculation unit; an azimuth estimation unit (316) that estimates the azimuth based on the protective member distance obtained by the distance calculation unit, wherein the power profile storage unit stores, for each azimuth, the power profile in which the received power corresponding to the superimposed reflected wave from two or more different azimuths and the protective member distance are associated; the power calculation unit obtains a first received power corresponding to the superimposed reflected wave received from at least a first azimuth among the two or more azimuths, and obtains a second received power corresponding to the superimposed reflected wave received from a second azimuth different from the first azimuth among the two or more azimuths; the distance calculation unit obtains the protective member distance based on the first received power, the second received power, and the power profile.

2. The first azimuth is a direction orthogonal to the front of the transmission antenna, and the power calculation unit obtains, as the first received power, the received power corresponding to the superimposed reflected wave received from the orthogonal direction. The azimuth estimation device according to claim 1.

3. The power profile storage unit stores the power profile in which the received power corresponding to the superimposed reflected wave including the reflected wave reflected by the protective member positioned at a position where the error between the design value of the protective member distance and the protective member distance is 1 / 4 or less of the wavelength of the transmission wave and the protective member distance are associated. The azimuth estimation device according to claim 1.

4. The protective member has a bent portion (B10) formed by bending at a portion facing the transmission antenna. The curvature of the bent portion is formed to be smaller than the value obtained by dividing 1 by the distance between the protection members. The azimuth estimation device according to claim 1, wherein the power profile storage unit stores the power profile in which the received power corresponding to the superimposed reflected wave including the reflected wave reflected by the bent portion is associated with the distance between the protection members.

5. An array correction unit (315) that corrects a mode vector indicating a phase corresponding to the arrival angle of the superimposed reflected wave using a correction matrix is provided. The array correction unit corrects the mode vector using the correction matrix based on the distance between the protection members obtained by the distance calculation unit. The azimuth estimation unit estimates the azimuth using the corrected mode vector that is the correction result of the mode vector in the array correction unit and the received signal corresponding to the transmitted wave reflected by the target, according to claim 1. The azimuth estimation device described.

6. An azimuth estimation method for estimating the arrival angle of a transmitted wave transmitted from a transmission antenna (13), passing through a protection member (B) of the transmission antenna, and reflected by a target to a radar device (1) as the azimuth of the target. A power profile acquisition step (S24) of acquiring a power profile in which the distance between the protection members, which is the distance between the transmission antenna and the protection member, and the received power corresponding to the superimposed reflected wave in which the reflected wave reflected by the target and the reflected wave reflected by the protection member overlap are associated; A power calculation step (S33, S36) of obtaining the received power corresponding to the superimposed reflected wave; A distance calculation step (S38) of obtaining the distance between the protection members based on the received power obtained in the power calculation step; An azimuth estimation step (S14) of estimating the azimuth based on the distance between the protection members obtained in the distance calculation step, comprising: In the power profile acquisition step, the power profile in which the received power corresponding to the reflected waves from two or more different azimuths and the distance between the protection members are associated is acquired for each azimuth. In the power calculation step, a first received power corresponding to the superimposed reflected wave received from at least a first azimuth among the two or more azimuths is obtained, and a second received power corresponding to the superimposed reflected wave received from a second azimuth different from the first azimuth among the two or more azimuths is obtained. In the distance calculation step, a direction estimation method for obtaining the distance between the protection members based on the first received power, the second received power, and the power profile. **Claim 7** The first direction is a direction orthogonal to the front of the transmission antenna, and In the power calculation step, the direction estimation method according to claim 6, wherein the first received power is the received power corresponding to the superimposed reflected wave received from the orthogonal direction. **Claim 8** In the power profile acquisition step, the power profile in which the received power corresponding to the superimposed reflected wave including the reflected wave reflected by the protection member positioned at a position where the error between the designed value of the distance between the protection members and the distance between the protection members is 1 / 4 or less of the wavelength of the transmission wave is associated with the distance between the protection members is acquired. The direction estimation method according to claim 6. **Claim 9** The protection member has a bent portion (B10) formed by bending at a portion facing the transmission antenna, The curvature of the bent portion is formed to be smaller than a value obtained by dividing 1 by the distance between the protection members, In the power profile acquisition step, the power profile in which the received power corresponding to the superimposed reflected wave including the reflected wave reflected by the bent portion is associated with the distance between the protection members is acquired. The direction estimation method according to claim 6.

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