Signal processing device, radar device, signal processing program, and signal processing method

Abstract

The present invention includes: a target detection unit (701) that, on the basis of a reflected wave received by a radar unit, which is a reflected wave obtained by the reflection of a radio wave transmitted by the radar unit off a target, detects a detection point derived from a mirror ghost of the target, and calculates a distance and an azimuth to the detection point from the radar unit; a target candidate point calculation unit (703) that calculates a target candidate point by estimating a propagation path of the radio wave on the basis of the distance and the azimuth calculated by the target detection unit (701) and information indicating a structure present in the vicinity of the host device; a combination detection unit (704) that detects a combination of target candidate points on the basis of the target candidate point calculated by the target candidate point calculation unit (703); and a movement direction and speed estimation unit (705) that estimates the movement direction and speed of the target on the basis of the speed of the detection point detected by the target detection unit (701) and the combination of the target candidate points detected by the combination detection unit (704).

Description

Signal processing device, radar device, signal processing program, and signal processing method

[0001] The present disclosure relates to a signal processing device, a radar device, a signal processing program, and a signal processing method.

[0002] Conventionally, for example, autonomous mobile robots or PMVs (Personal Mobility Vehicles) have used radar, lidar, or cameras to detect objects and avoid collisions between the vehicle and the object by monitoring the surroundings of the vehicle. However, optical sensors such as cameras or lidar cannot detect objects that exist outside the line of sight of the vehicle. On the other hand, radar can detect such objects that exist outside the line of sight by utilizing the reflection or diffraction of radio waves.

[0003] Furthermore, a device for estimating the moving direction and speed of a target is known (see, for example, Patent Document 1). The device disclosed in Patent Document 1 uses a radar to estimate the moving direction and speed of a target by utilizing reflected waves from walls around the radar.

[0004] Japanese Patent Application Laid-Open No. 2024-2717

[0005] On the other hand, the information on distance, direction, and speed observed by radar contains errors, as it deviates from the actual distance, direction, or speed due to various factors such as the shape and material of the target, which affect how much and in which direction the radar wave is reflected, as well as the accuracy and stability of the radar device itself, the state of calibration, etc. In contrast, the device disclosed in Patent Document 1 is effective under ideal conditions where no errors are included, but does not disclose any measures to be taken when errors are included.

[0006] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a signal processing device that can estimate the direction and speed of movement of a target even when information obtained by radar contains errors.

[0007] The signal processing device according to the present disclosure is characterized by including a target detection unit that detects detection points resulting from a mirror ghost of the target based on reflected waves of radio waves transmitted by a radar unit that are reflected by the target and received by the radar unit, and calculates the distance and direction of the detection points from the radar unit; a candidate target point calculation unit that calculates candidate target points by estimating a propagation path of the radio waves based on the distance and direction calculated by the target detection unit and information indicating structures present in the vicinity of the vehicle; a combination detection unit that detects combinations of candidate target points based on the candidate target points calculated by the candidate target point calculation unit; and a movement direction and speed estimation unit that estimates the movement direction and speed of the target based on the speed of the detection points detected by the target detection unit and the combination of candidate target points detected by the combination detection unit.

[0008] According to the present disclosure, with the above configuration, it is possible to estimate the moving direction and speed of a target even if the information obtained by the radar contains errors.

[0009] 3A is a diagram showing an example of the configuration of a radar device including a signal processing device according to embodiment 1. FIG. 3B is a flowchart showing an example of the operation of the signal processing device according to embodiment 1. FIG. 3A and FIG. 3B are diagrams showing an example of the operation of a target candidate point calculation unit according to embodiment 1, in which FIG. 3A is a diagram showing an example of observation information (distance and direction) obtained from a digital signal, and FIG. 3B is a diagram showing an example of target candidate points obtained from the observation information shown in FIG. 3A and information indicating structures. FIG. 3B is a diagram showing an example of the operation of a target candidate point selection unit according to embodiment 1. FIG. 3C is a diagram showing an example of the operation of a combination extraction unit according to embodiment 1. FIG. 3D is a diagram showing an example of the operation of a combination extraction unit according to embodiment 1. FIG. 3E is a diagram showing an example of the operation of a movement direction speed estimation unit according to embodiment 1. FIG. 8A and FIG. 8B are diagrams showing an example of the operation of the movement direction speed estimation unit according to embodiment 1. FIG. 9A and FIG. 9B are diagrams showing an example of the operation of a propagation path correction unit according to embodiment 1, in which FIG. 9A is a diagram showing an example of a propagation path from a target candidate point to a radar unit, and FIG. 9B is a diagram showing an example of a propagation path from the radar unit to a target candidate point after correction. 10A and 10B are diagrams for explaining the effects of the signal processing device according to embodiment 1, in which Fig. 10A is a diagram showing an example of a target position estimated by a conventional technique, and Fig. 10B is a diagram showing an example of a target position estimated by the signal processing device according to embodiment 1. Figs. 11A and 11B are diagrams showing an example of a hardware configuration of the signal processing device according to embodiment 1.

[0010] Hereinafter, embodiments will be described in detail with reference to the drawings. Embodiment 1. Fig. 1 is a diagram showing an example of the configuration of a radar device including a signal processing device 7 according to embodiment 1. As shown in Fig. 1, the radar device includes, for example, a transmitting antenna 1, a receiving antenna 2, a signal generator 3, a frequency converter 4, a filter 5, an AD converter 6, and the signal processing device 7.

[0011] The transmitting antenna 1 transmits to the outside the signal generated by the signal generator 3. More specifically, the transmitting antenna 1 transmits to the outside the signal generated by the signal generator 3 as radio waves.

[0012] The receiving antenna 2 receives the reflected waves that are the radio waves transmitted by the transmitting antenna 1 and reflected by an object whose position is to be estimated. Note that, here, the object whose position is to be estimated by the signal processing device 7 is also referred to as a "target."

[0013] The transmitting antenna 1 and the receiving antenna 2 constitute a radar section of the radar device. As shown in Fig. 1, the radar device is equipped with multiple transmitting antennas 1 and multiple receiving antennas 2. In other words, the radar device is a multiple input multiple output (MIMO) radar device.

[0014] The signal generator 3 generates a signal to be transmitted by the transmitting antenna 1. Here, the signal generated by the signal generator 3 is, for example, a chirp signal whose frequency changes linearly over time. The signal generated by the signal generator 3 is transmitted as a radio wave by the transmitting antenna 1.

[0015] The frequency converter 4 converts the frequency of the signal related to the reflected wave received by each of the plurality of receiving antennas 2 to an intermediate frequency. The signal converted to the intermediate frequency by the frequency converter 4 is output to the filter 5.

[0016] The filter 5 extracts a signal of a desired frequency band from the signal converted to an intermediate frequency by the frequency converter 4. The signal of the desired frequency band extracted by the filter 5 is output to the AD converter 6.

[0017] The AD converter 6 converts the signal extracted by the filter 5 from an analog signal to a digital signal. The digital signal obtained by the AD converter 6 is output to a signal processing device 7.

[0018] The signal processing device 7 estimates the position, moving direction, and speed of the target based on the digital signal obtained by the AD converter 6. In particular, the signal processing device 7 is intended to estimate the position, moving direction, and speed of a target located outside the line of sight. Outside the line of sight refers to a region that is a blind spot from the radar device due to structures such as walls that exist around the radar device.

[0019] This signal processing device 7 estimates the propagation path of the radio waves from the observation information (distance and direction (angle)) obtained from the digital signal and information indicating the above-mentioned structure, estimates the moving direction and speed of the target from the propagation path and the observed speed of the radio waves, corrects the propagation path from the observed speed of the radio waves and the speed of the target, and estimates the position of the target from the corrected propagation path.

[0020] The signal processing device 7 may estimate the position, moving direction, and speed of a target located within the line of sight by using an existing method. The line of sight is an area that is not a blind spot for the radar device due to structures such as walls around the radar device.

[0021] As shown in FIG. 1 , the signal processing device 7 includes a target detection unit 701, a model creation unit 702, a target candidate point calculation unit 703, a combination detection unit 704, a movement direction speed estimation unit 705, a propagation path correction unit 706, a target position estimation unit 707, and a speed correction unit 708.

[0022] The target detection unit 701 detects a detection point originating from the mirror ghost of the target based on the digital signal obtained by the AD converter 6, and calculates observation information for the detection point. The observation information for the detection point is the distance and azimuth (angle) of the detection point from the radar unit (radar device).

[0023] That is, first, the target detection unit 701 detects a detection point resulting from a mirror ghost of a target by analyzing the digital signal obtained by the AD converter 6. Then, the target detection unit 701 calculates the distance and direction of the detection point from the radar unit by analyzing the digital signal obtained by the AD converter 6.

[0024] For example, the target detection unit 701 performs frequency analysis of the digital signal obtained by the AD converter 6 using FFT (Fast Fourier Transform) to obtain the frequency of the differential signal between the signal transmitted by the transmitting antenna 1 and the signal received by the receiving antenna 2. Then, the target detection unit 701 calculates the distance of the detection point from the radar unit from the frequency of the differential signal.

[0025] Furthermore, for example, when the plurality of transmitting antennas 1 and receiving antennas 2 are each configured as an array antenna, the target detection unit 701 calculates the azimuth of the detection point from the radar unit using a method of spatially scanning a directional beam called a beamformer. Furthermore, for example, when the plurality of transmitting antennas 1 and receiving antennas 2 are each configured as an array antenna, the target detection unit 701 may calculate the azimuth of the detection point from the radar unit using a method such as MUSIC (Multiple Signal Classification), which utilizes eigenvalue expansion of the correlation matrix of signals related to reflected waves received by each receiving antenna 2, or ESPRIT (Estimation of Signal Parameters via Rotational Invariance Techniques). Note that the above-mentioned methods are all well-known in the art, and therefore detailed description thereof will be omitted here.

[0026] The model creation unit 702 creates information indicating structures present in the vicinity of the radar device. That is, for example, the model creation unit 702 creates a three-dimensional model of the structures present in the vicinity of the radar device.

[0027] For example, the model creation unit 702 creates a three-dimensional model of the structures existing around the radar device based on commercially available data showing structures such as buildings and walls existing around the radar device, and data that is widely available to the public showing the undulations of the roads around the radar device.

[0028] The model creation unit 702 creates a three-dimensional model of the structures present around the radar device based on data showing the results of aerial surveys previously acquired, data obtained by previously scanning structures etc. with a laser scanner, and previously generated CAD drawings, etc. The above data are previously recorded in a recording unit (not shown) provided in the signal processing device 7.

[0029] 1 shows a case where the model creation unit 702 is provided in the signal processing device 7. However, the model creation unit 702 is not an essential component of the signal processing device 7, and the model creation unit 702 does not necessarily have to be provided in the signal processing device 7.

[0030] The target candidate point calculation unit 703 calculates target candidate points by estimating the propagation path of radio waves based on the distance and direction calculated by the target detection unit 701 and information indicating structures present in the vicinity of the own vehicle. If the signal processing device 7 is provided with a model creation unit 702, the target candidate point calculation unit 703 uses the information created by the model creation unit 702 as the information indicating structures present in the vicinity of the own vehicle.

[0031] At this time, the target candidate point calculation unit 703 determines whether or not the detection point detected by the target detection unit 701 is on the back side of the structure, based on the distance and direction calculated by the target detection unit 701 and information indicating the structure existing in the vicinity of the aircraft. Note that, if the position of the detection point is corrected as described below, the target candidate point calculation unit 703 determines whether or not the corrected detection point is on the back side of the structure, based on the distance and direction calculated by the target detection unit 701 and information indicating the structure existing in the vicinity of the aircraft.

[0032] Here, if the target candidate point calculation unit 703 determines that the detected point is not on the rear side of the structure, it sets the detected point as a target candidate point.

[0033] On the other hand, if the target candidate point calculation unit 703 determines that the detection point is on the back side of the structure, it calculates the reflection point of the radio waves on the structure and the reflection direction of the radio waves at the reflection point based on the vector indicating the direction calculated by the target detection unit 701, the normal vector of the structure, and the vector of an arbitrary point on the structure.

[0034] Then, the target candidate point calculation unit 703 corrects the position of the detection point by calculating the propagation path of the radio wave based on the distance and direction calculated by the target detection unit 701 and the calculated reflection point and reflection direction. At this time, for example, the target candidate point calculation unit 703 calculates, as the propagation path, a first propagation path that is a propagation path with the same round-trip path, or a second propagation path that is a propagation path with different round-trip paths.

[0035] For example, the target candidate point calculation unit 703 may calculate a first propagation path based on the distance and direction calculated by the target detection unit 701, and the calculated reflection point and reflection direction, by folding back a path based on the distance and direction at the reflection point on the structure in the reflection direction. The first propagation path is a propagation path of radio waves from the radar unit to the detection point via the reflection point on the structure. The first propagation path starts from the position of the radar unit and ends at the detection point.

[0036] Furthermore, for example, the target candidate point calculation unit 703 may calculate a second propagation path based on the first propagation path. The second propagation path is a path different from the first propagation path and is a propagation path of radio waves in the opposite direction to the first propagation path, i.e., a path of radio waves from the detection point to the radar unit via a reflection point on the structure different from the reflection point. The second propagation path starts from the detection point and ends at the position of the radar unit.

[0037] Since the above-mentioned methods are all well-known, detailed explanations will be omitted here.

[0038] The combination detection unit 704 detects combinations of target candidate points based on the target candidate points calculated by the target candidate point calculation unit 703. The combination detection unit 704 has a target candidate point selection unit 7041 and a combination extraction unit 7042, as shown in FIG.

[0039] The target candidate point selection unit 7041 selects target candidate points based on the target candidate points calculated by the target candidate point calculation unit 703 .

[0040] In this case, for example, first, the target candidate point selection unit 7041 sets each target candidate point as a reference point based on the target candidate points calculated by the target candidate point calculation unit 703, and calculates the distance difference between all target candidate points and the reference point for each reference point. Then, the target candidate point selection unit 7041 calculates a cumulative distance difference by adding up the distance differences from N target candidate points in ascending order of distance difference for each reference point. Here, N is a number smaller than the number of detection points derived from the mirror ghost of the target. Then, the target candidate point selection unit 7041 sets the target candidate point corresponding to the reference point with the smallest cumulative distance difference as the target candidate point to be processed. In other words, the target candidate point selection unit 7041 narrows down the target candidate points based on the distance between the target candidate points.

[0041] The combination extraction unit 7042 extracts combinations of target candidate points based on at least one of the distance from the reference position and the angular difference of the propagation paths at any two target candidate points from the target candidate points selected by the target candidate point selection unit 7041. The following describes a case where the combination extraction unit 7042 extracts combinations of target candidate points based on both the distance from the reference position and the angular difference of the propagation paths at any two target candidate points.

[0042] In this case, for example, the combination extraction unit 7042 first calculates the standard deviation of the distance differences between all of the target candidate points selected by the target candidate point selection unit 7041 and the reference position. Note that the reference position is, for example, the average coordinate position of all of the target candidate points selected by the target candidate point selection unit 7041. Then, the combination extraction unit 7042 extracts target candidate points whose distance differences from the reference position are equal to or less than the standard deviation from the target candidate points selected by the target candidate point selection unit 7041. That is, the combination extraction unit 7042 uses the standard deviation as a threshold to narrow down the target candidate points. Then, from the extracted target candidate points, the combination extraction unit 7042 extracts combinations of target candidate points where the angle difference (propagation angle difference) of the propagation paths between any two target candidate points is equal to or greater than a predetermined threshold. That is, the combination extraction unit 7042 narrows down the combinations of target candidate points based on the magnitude of the propagation angle difference.

[0043] The method for calculating the propagation angle difference between any two target candidate points differs depending on whether the propagation path is the first propagation path or the second propagation path. That is, when the propagation path of the target candidate point selected by the target candidate point selection unit 7041 is the first propagation path (a propagation path with the same round-trip path), the combination extraction unit 7042 calculates the angular difference of the propagation paths using the reflection direction of the radio waves at the target candidate point. On the other hand, when the propagation path of the target candidate point selected by the target candidate point selection unit 7041 is the second propagation path (a propagation path with different round-trip paths), the combination extraction unit 7042 calculates the angular difference of the propagation paths using the intermediate direction between the incident direction of the radio waves at the target candidate point and the reflection direction of the radio waves at the target candidate point.

[0044] 1 shows a case where the target candidate point selection unit 7041 is provided in the signal processing device 7. However, the target candidate point selection unit 7041 is not an essential component of the signal processing device 7, and the target candidate point selection unit 7041 does not have to be provided in the signal processing device 7. That is, in this case, the combination extraction unit 7042 extracts combinations of target candidate points from the target candidate points calculated by the target candidate point calculation unit 703, based on at least one of the distance from the reference position and the angular difference between the propagation paths at any two target candidate points.

[0045] The movement direction and speed estimation unit 705 estimates the movement direction and speed of the target based on the speed (observed speed) of the detection point detected by the target detection unit 701 and the combination of target candidate points detected by the combination detection unit 704.

[0046] In this case, first, the movement direction and speed estimation unit 705 calculates the angular difference of the propagation paths for each combination based on the combination of target candidate points detected by the combination detection unit 704. Then, the movement direction and speed estimation unit 705 calculates the movement direction and speed of the target for each combination based on the speed of the detection points detected by the target detection unit 701 and the angular difference of the propagation paths for each combination. Thereafter, the movement direction and speed estimation unit 705 calculates the movement direction and speed of the target using statistical processing based on the movement direction and speed of the target for each combination. An example of statistical processing is averaging.

[0047] The propagation path correction unit 706 corrects the propagation path of the radio waves based on the distance calculated by the target detection unit 701 and the speed of the detected detection point, as well as the speed of the target estimated by the movement direction speed estimation unit 705.

[0048] In this case, first, the propagation path correction unit 706 calculates the emission angle of the propagation path from the target candidate point to the radar unit (radar device) for each combination based on the speed of the detection point detected by the target detection unit 701 and the speed of the target estimated by the movement direction speed estimation unit 705. Then, the propagation path correction unit 706 calculates the propagation path from the target candidate point to the radar unit for each combination based on the distance calculated by the target detection unit 701 and the emission angle of the propagation path. Then, the propagation path correction unit 706 calculates the incident angle of the propagation path with respect to the front of the radar unit for each combination. Then, the propagation path correction unit 706 corrects the propagation path from the radar unit to the target candidate point for each combination based on the propagation path and the incident angle.

[0049] The target position estimation unit 707 estimates the position of the target based on the radio wave propagation path corrected by the propagation path correction unit 706 .

[0050] In this case, for example, the target position estimation unit 707 first sets each target candidate point as a reference point based on the target candidate points that are detection points of the propagation path after correction by the propagation path correction unit 706, and calculates the distance difference between all of the target candidate points and the reference point for each reference point. Then, the target position estimation unit 707 calculates a cumulative distance difference by summing the distance differences from N target candidate points in ascending order of distance difference for each reference point. Here, N is a number smaller than the number of detection points derived from the mirror ghost of the target. Then, the target position estimation unit 707 extracts the target candidate point for the reference point with the smallest cumulative distance difference from among the reference points. Then, the target position estimation unit 707 estimates the position of the target by calculating the coordinate average position of all the extracted target candidate points.

[0051] The speed correction unit 708 corrects the speed based on the moving speed of the radar unit (radar device) and the speed of the target estimated by the moving direction speed estimation unit 705. In other words, since the speed of the target estimated by the moving direction speed estimation unit 705 is a relative speed with respect to the moving speed of the radar unit, the speed correction unit 708 calculates the absolute speed of the target from these.

[0052] 1 shows a case where the speed correction unit 708 is provided in the signal processing device 7. However, the speed correction unit 708 is not an essential component of the signal processing device 7, and the speed correction unit 708 does not necessarily have to be provided in the signal processing device 7.

[0053] 1 shows an example of a configuration in which the signal processing device 7 estimates the position, moving direction, and speed of the target based on the digital signal obtained by the AD converter 6. However, the signal processing device 7 may estimate only the position and moving direction of the target based on the digital signal obtained by the AD converter 6. In this case, the signal processing device 7 does not need the propagation path correction unit 706 and the target position estimation unit 707.

[0054] Although the above description has been given of the process assuming a case where there is one target, the signal processing device 7 can also handle a case where there are multiple targets.

[0055] That is, in this case, the combination detection unit 704 divides the target candidate points into a plurality of groups based on the density of the target candidate points calculated by the target candidate point calculation unit 703, and detects a combination of target candidate points for each group. The movement direction and speed estimation unit 705 then estimates the movement direction and speed of the target for each group based on the combination of target candidate points for each group detected by the combination detection unit 704. The propagation path correction unit 706 then corrects the radio wave propagation path for each group based on the distance calculated by the target detection unit 701 and the speed of the detected detection point, and the speed of the target for each group estimated by the movement direction and speed estimation unit 705. The target position estimation unit 707 then estimates the position of the target for each group based on the radio wave propagation path corrected for each group by the propagation path correction unit 706.

[0056] Next, an example of the operation of the signal processing device 7 according to the first embodiment shown in Fig. 1 will be described with reference to Fig. 2. In the following, it is assumed that a radar device including the signal processing device 7 is mounted on a vehicle.

[0057] In the following, a case will be described in which the signal processing device 7 estimates the position of a target that is outside the line of sight of the host vehicle. Note that the signal processing device 7 may estimate the position of a target that is within the line of sight of the host vehicle using an existing method.

[0058] 2 , the radar device is assumed to have completed the following steps: signal generation by the signal generator 3, transmission of radio waves by the transmitting antenna 1, reception of reflected waves by the receiving antenna 2, conversion of the frequency of the signal related to the reflected waves to an intermediate frequency by the frequency converter 4, extraction of a signal in a desired frequency band by the filter 5, and conversion of the extracted signal into a digital signal by the AD converter 6. The model creation unit 702 is also assumed to have created information indicating structures present around the radar device.

[0059] In an example of the operation of the signal processing device 7 according to the first embodiment shown in FIG. 1, as shown in FIG. 2, the target detection unit 701 first detects a detection point originating from a mirror ghost of a target based on the digital signal obtained by the AD converter 6, and calculates the distance and azimuth (angle) of the detection point from the radar unit (radar device) (step ST101).

[0060] Next, the target candidate point calculation unit 703 calculates the target candidate point by estimating the propagation path of the radio waves based on the distance and direction calculated by the target detection unit 701 and the information indicating the structure created by the model creation unit 702 (step ST102).

[0061] For example, as shown in Fig. 3, the target candidate point calculation unit 703 obtains target candidate points by estimating propagation paths using observation information (distance and direction of the detection point) and information indicating the structure. Fig. 3A shows an example of the observation information, and Fig. 3B shows an example of target candidate points obtained from the observation information and information indicating the structure shown in Fig. 3A. In Fig. 3, square marks indicate the position of the radar unit, diamond marks indicate the position of the target candidate points, and star marks indicate the position of the targets. The example in Fig. 3 shows a case where the structure is a T-junction.

[0062] Next, based on the target candidate points calculated by the target candidate point calculation unit 703, the target candidate point selection unit 7041 sets each target candidate point as a reference point and calculates the distance difference between all target candidate points and the reference point for each reference point (step ST103).

[0063] Next, the target candidate point selection unit 7041 calculates, for each reference point, the cumulative distance difference by adding up the distance differences from the N target candidate points in ascending order of distance difference (step ST104), where N is a number smaller than the number of detection points derived from the mirror ghost of the target.

[0064] Next, the target candidate point selection unit 7041 selects the target candidate point for the reference point with the smallest cumulative distance difference as the target candidate point to be processed (step ST105).

[0065] Next, the combination extraction unit 7042 calculates the standard deviation of the distance differences between all of the target candidate points selected by the target candidate point selection unit 7041 and the reference position (step ST106). Note that the reference position is, for example, the position of the average coordinate of all of the target candidate points selected by the target candidate point selection unit 7041.

[0066] Next, the combination extraction unit 7042 extracts target candidate points whose distance difference from the reference position is equal to or less than the standard deviation from the target candidate points selected by the target candidate point selection unit 7041 (step ST107). That is, the combination extraction unit 7042 uses the standard deviation as a threshold value to narrow down the target candidate points.

[0067] For example, as shown in Fig. 4, the combination extraction unit 7042 excludes target candidate points that are far from the reference position from among the target candidate points selected by the target candidate point selection unit 7041. This improves estimation accuracy. In Fig. 4, a triangular mark indicates the reference position. Furthermore, reference numeral 11 indicates a target candidate point whose distance difference from the reference position is equal to or less than the standard deviation. Furthermore, reference numeral 12 indicates a target candidate point whose distance difference from the reference position is greater than the standard deviation, i.e., a target candidate point to be excluded.

[0068] Next, the combination extraction unit 7042 extracts, from the extracted target candidate points, combinations of target candidate points where the angular difference between the propagation paths of any two target candidate points is equal to or greater than a predetermined threshold (step ST108). That is, the combination extraction unit 7042 narrows down the combinations of target candidate points based on the magnitude of the propagation angle difference.

[0069] The method for calculating the propagation angle difference between any two target candidate points differs depending on whether the propagation path is the first propagation path or the second propagation path. That is, when the propagation path of the target candidate point selected by the target candidate point selection unit 7041 is the first propagation path (a propagation path with the same round-trip path), the combination extraction unit 7042 calculates the angular difference of the propagation paths using the reflection direction of the radio waves at the target candidate point. On the other hand, when the propagation path of the target candidate point selected by the target candidate point selection unit 7041 is the second propagation path (a propagation path with different round-trip paths), the combination extraction unit 7042 calculates the angular difference of the propagation paths using the intermediate direction between the incident direction of the radio waves at the target candidate point and the reflection direction of the radio waves at the target candidate point.

[0070] Here, for example, FIG. 5 shows a case where the propagation path (A) of the first target candidate point and the propagation path (B) of the second target candidate point are both the first propagation path (propagation path with the same round-trip path). In this case, as indicated by reference numeral 21 in FIG. 5, the movement direction of the first target candidate point on the propagation path is the reflection direction of the radio waves at the first target candidate point. Similarly, as indicated by reference numeral 22 in FIG. 5, the movement direction of the second target candidate point on the propagation path is the reflection direction of the radio waves at the second target candidate point. Therefore, the combination extraction unit 7042 calculates the angular difference between the above two directions as the angular difference (Δθ) of the propagation paths. Note that in FIG. 5, reference numeral 23 indicates a structure.

[0071] 6, for example, shows a case where the propagation path (A) of the first target candidate point is the second propagation path (a propagation path with a different round-trip path), and the propagation path (B) of the second target candidate point is the first propagation path (a propagation path with the same round-trip path). In this case, as shown by reference numeral 33 in FIG. 6, the movement direction of the first target candidate point on the propagation path is an intermediate direction between the incident direction of the radio wave to the first target candidate point (the direction of the propagation path shown by reference numeral 31) and the reflection direction of the radio wave at the first target candidate point (the direction of the propagation path shown by reference numeral 32). Also, as shown by reference numeral 34 in FIG. 6, the movement direction of the second target candidate point on the propagation path is the reflection direction of the radio wave at the second target candidate point. Therefore, the combination extraction unit 7042 calculates the angular difference between the above two directions as the angular difference (Δθ) of the propagation paths. Note that reference numeral 35 in FIG. 6 indicates a structure.

[0072] Next, the movement direction and speed estimation unit 705 estimates the movement direction and speed of the target based on the speed (observed speed) of the detection point detected by the target detection unit 701 and the combination of target candidate points detected by the combination detection unit 704 (step ST109).

[0073] In this case, first, the movement direction and speed estimation unit 705 calculates the angular difference of the propagation paths for each combination based on the combination of target candidate points detected by the combination detection unit 704. Then, the movement direction and speed estimation unit 705 calculates the movement direction and speed of the target for each combination based on the speed of the detection points detected by the target detection unit 701 and the angular difference of the propagation paths for each combination. Thereafter, the movement direction and speed estimation unit 705 calculates the movement direction and speed of the target using statistical processing such as averaging processing based on the movement direction and speed of the target for each combination.

[0074] For example, as shown in FIGS. 5 to 7, the moving direction speed estimating unit 705 calculates the angular difference (Δθ) between the combined propagation path (A) of the first target candidate point and the propagation path (B) of the second target candidate point. Then, the moving direction speed estimating unit 705 calculates the angular difference (Δθ) between the propagation path (A) and the propagation path (B) and the observed speed (v Ａ) and the observed velocity (v Ｂ ), the target movement direction (θ Ｂ ) and velocity (v ｔ That is, Δθ is expressed by the following equation (1), and θ is the azimuth from the candidate point of the second target that indicates the moving direction of the target. Ｂ is expressed by the following equations (2) and (3), and the target velocity v ｔ is expressed by the following equation (4). The moving direction speed estimation unit 705 performs the above process for each combination. Δθ=cos －１ (A・B / |A||B|) (1) θ Ｂ =tan －１ ((v ＢＡ cosΔθ−1) / (v ＢＡ sinΔθ)) (2) v ＢＡ =v Ｂ / v Ａ　　 (3) v ｔ =v Ｂ / cosθ Ｂ　　 (4)

[0075] As a result, the moving direction and speed of the target for each combination can be obtained, as shown in Fig. 8, for example. Then, the moving direction and speed estimation unit 705 obtains the moving direction and speed of the target using statistical processing based on the moving direction and speed of the target for each combination. In the example of Fig. 8, the moving direction and speed of the target are obtained by averaging the moving direction and speed of the target for each combination, but this is not limiting, and statistical processing using weighting, for example, may also be performed.

[0076] Next, the propagation path correction unit 706 corrects the propagation path of the radio waves based on the distance calculated by the target detection unit 701 and the speed of the detected detection point, as well as the speed of the target estimated by the movement direction speed estimation unit 705 (step ST110).

[0077] In this case, first, the propagation path correction unit 706 calculates the emission angle of the propagation path from the target candidate point to the radar unit (radar device) for each combination based on the speed of the detection point detected by the target detection unit 701 and the speed of the target estimated by the movement direction speed estimation unit 705. Then, the propagation path correction unit 706 calculates the propagation path from the target candidate point to the radar unit for each combination based on the distance calculated by the target detection unit 701 and the emission angle of the propagation path. Then, the propagation path correction unit 706 calculates the incident angle of the propagation path with respect to the front of the radar unit for each combination. Then, the propagation path correction unit 706 corrects the propagation path from the radar unit to the target candidate point for each combination based on the propagation path and the incident angle.

[0078] For example, as shown in FIG. 9, the propagation path correction unit 706 calculates the observed velocity (v Ｂ ), and the target speed (v ｔ ) based on the output angle of the propagation path (θ Ｂ Then, the propagation path correction unit 706 calculates the output angle (θ Ｂ 9A, reference numeral 41 denotes the propagation path of the radio wave from the target to the radar unit calculated by the propagation path correction unit 706. The propagation path correction unit 706 then calculates the incident angle (θ Ｃ ) is calculated. The propagation path correction unit 706 calculates the propagation path indicated by the reference numeral 41 and the incident angle (θ Ｃ 9B, reference numeral 42 denotes the propagation path of the radio wave from the radar unit to the target, which has been corrected by the propagation path correction unit 706.

[0079] Next, the target position estimation unit 707 estimates the position of the target based on the radio wave propagation path corrected by the propagation path correction unit 706 (step ST111).

[0080] In this case, for example, the target position estimation unit 707 first sets each target candidate point as a reference point based on the target candidate points that are detection points of the propagation path after correction by the propagation path correction unit 706, and calculates the distance difference between all of the target candidate points and the reference point for each reference point. Then, the target position estimation unit 707 calculates a cumulative distance difference by summing the distance differences from N target candidate points in ascending order of distance difference for each reference point. Here, N is a number smaller than the number of detection points derived from the mirror ghost of the target. Then, the target position estimation unit 707 extracts the target candidate point for the reference point with the smallest cumulative distance difference from among the reference points. Then, the target position estimation unit 707 estimates the position of the target by calculating the coordinate average position of all the extracted target candidate points.

[0081] Next, the speed correction unit 708 corrects the speed based on the moving speed of the radar unit (radar device) and the speed of the target estimated by the moving direction speed estimation unit 705 (step ST112). That is, since the speed of the target estimated by the moving direction speed estimation unit 705 is a relative speed with respect to the moving speed of the radar unit, the speed correction unit 708 calculates the absolute speed of the target from these.

[0082] Fig. 10 is a diagram for explaining the effect of the signal processing device 7 according to embodiment 1. Fig. 10A shows an example of a target position estimation result (average of target candidate points) according to the conventional technology, and Fig. 10B shows an example of a target position estimation result (average of target candidate points) according to the signal processing device 7 according to embodiment 1. In Fig. 10, the coordinates of the true value are (x, y) = (7.9, 8.5), the speed of the true value is 1 m / s, and the movement direction of the true value is 180 deg (based on the X axis).

[0083] In this case, as shown in Fig. 10A, target position estimation using the conventional technology yields (x, y) = (7.7, 8.2). In contrast, as shown in Fig. 10B, target position estimation using the signal processing device 7 according to embodiment 1 yields (x, y) = (7.9, 8.7), which is closer to the true value than the conventional technology. Furthermore, target velocity estimation using the signal processing device 7 according to embodiment 1 yields 0.996 m / s, and movement direction estimation yields 180.1 deg (based on the X-axis), both of which are close to the true value.

[0084] As described above, according to this embodiment 1, the signal processing device 7 includes a target detection unit 701 that detects detection points resulting from the mirror ghost of the target based on the reflected waves of the radio waves transmitted by the radar unit that are reflected by the target and received by the radar unit, and calculates the distance and direction of the detection points from the radar unit, a candidate target point calculation unit 703 that calculates candidate target points by estimating the propagation path of the radio waves based on the distance and direction calculated by the target detection unit 701 and information indicating structures present in the vicinity of the host aircraft, a combination detection unit 704 that detects combinations of candidate target points based on the candidate target points calculated by the candidate target point calculation unit 703, and a movement direction and speed estimation unit 705 that estimates the movement direction and speed of the target based on the speed of the detection points detected by the target detection unit 701 and the combination of candidate target points detected by the combination detection unit 704. As a result, the signal processing device 7 according to embodiment 1 can estimate the movement direction and speed of the target even when the information obtained by the radar contains errors.

[0085] Moreover, according to this embodiment 1, there are provided a propagation path correction unit 706 that corrects the propagation path of radio waves based on the distance calculated by the target detection unit 701, the speed of the detected detection point, and the speed of the target estimated by the movement direction speed estimation unit 705, and a target position estimation unit 707 that estimates the position of the target based on the propagation path of radio waves corrected by the propagation path correction unit 706. As a result, the signal processing device 7 according to embodiment 1 can improve the estimation accuracy of the target position compared to conventional devices.

[0086] Furthermore, according to this embodiment 1, the combination detection unit 704 includes a combination extraction unit 7042 that extracts combinations of target candidate points based on at least one of the distance from the reference position to the target candidate point calculated by the target candidate point calculation unit 703 and the angular difference between the propagation paths at any two target candidate points. Also, according to this embodiment 1, if the propagation paths of the target candidate points calculated by the target candidate point calculation unit 703 are the same propagation paths for both round trips, the combination extraction unit 7042 calculates the angular difference between the propagation paths using the reflection direction of the radio waves at the target candidate point. Also, according to this embodiment 1, if the propagation paths of the target candidate points calculated by the target candidate point calculation unit 703 are different propagation paths for both round trips, the combination extraction unit 7042 calculates the angular difference between the propagation paths using the intermediate direction between the incident direction of the radio waves at the target candidate point and the reflection direction of the radio waves at the target candidate point. As a result, the signal processing device 7 according to this embodiment 1 can improve estimation accuracy.

[0087] Furthermore, according to this embodiment 1, the combination detection unit 704 divides the target candidate points into a plurality of groups from the density based on the target candidate points calculated by the target candidate point calculation unit 703, and detects combinations of target candidate points for each group, and the movement direction and speed estimation unit 705 estimates the movement direction and speed of the target for each group based on the combination of target candidate points for each group detected by the combination detection unit 704. This makes it possible for the signal processing device 7 according to embodiment 1 to handle cases where there are a plurality of targets.

[0088] Furthermore, according to this embodiment 1, the signal processing method includes the steps of: a target detection unit 701 detecting detection points resulting from mirror ghosts of the targets based on reflected waves of radio waves transmitted by a radar unit that are reflected by the targets and received by the radar unit, and calculating the distances and directions of the detection points from the radar unit; a target candidate point calculation unit 703 calculating target candidate points by estimating propagation paths of the radio waves based on the distances and directions calculated by the target detection unit 701 and information indicating structures present in the vicinity of the vehicle; a combination detection unit 704 detecting combinations of target candidate points based on the target candidate points calculated by the target candidate point calculation unit 703; and a movement direction and speed estimation unit 705 estimating the movement direction and speed of the targets based on the speeds of the detection points detected by the target detection unit 701 and the combinations of the target candidate points detected by the combination detection unit 704. As a result, the signal processing method according to embodiment 1 makes it possible to estimate the movement direction and speed of the targets even when information obtained by the radar includes errors.

[0089] Finally, an example of the hardware configuration of the signal processing device 7 according to the first embodiment will be described with reference to Fig. 11 . The functions of the target detection unit 701, model creation unit 702, target candidate point calculation unit 703, combination detection unit 704, movement direction speed estimation unit 705, propagation path correction unit 706, target position estimation unit 707, and speed correction unit 708 in the signal processing device 7 are realized by a processing circuit 51. The processing circuit 51 may be dedicated hardware as shown in Fig. 11A , or may be a CPU (also referred to as a central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, processor, or DSP (Digital Signal Processor)) 52 that executes a program stored in a memory 53 as shown in Fig. 11B .

[0090] When the processing circuitry 51 is dedicated hardware, the processing circuitry 51 may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof. The functions of each of the target detection unit 701, the model creation unit 702, the target candidate point calculation unit 703, the combination detection unit 704, the movement direction and speed estimation unit 705, the propagation path correction unit 706, the target position estimation unit 707, and the speed correction unit 708 may be realized individually by the processing circuitry 51, or the functions of each unit may be realized collectively by the processing circuitry 51.

[0091] When the processing circuitry 51 is a CPU 52, the functions of the target detection unit 701, model creation unit 702, target candidate point calculation unit 703, combination detection unit 704, movement direction speed estimation unit 705, propagation path correction unit 706, target position estimation unit 707, and speed correction unit 708 are realized by software, firmware, or a combination of software and firmware. The software and firmware are written as programs and stored in the memory 53. The processing circuitry 51 realizes the functions of each unit by reading and executing the programs stored in the memory 53. That is, the signal processing device 7 includes the memory 53 for storing a program that, when executed by the processing circuitry 51, results in the execution of, for example, each step shown in FIG. 2 . It can also be said that these programs cause a computer to execute the procedures and methods of a target detection unit 701, a model creation unit 702, a target candidate point calculation unit 703, a combination detection unit 704, a movement direction speed estimation unit 705, a propagation path correction unit 706, a target position estimation unit 707, and a speed correction unit 708. Here, examples of the memory 53 include non-volatile or volatile semiconductor memories such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable ROM), and EEPROM (Electrically EPROM), magnetic disks, flexible disks, optical disks, compact disks, minidisks, and DVDs (Digital Versatile Discs).

[0092] It is to be noted that the functions of the target detection unit 701, the model creation unit 702, the target point candidate calculation unit 703, the combination detection unit 704, the movement direction speed estimation unit 705, the propagation path correction unit 706, the target position estimation unit 707, and the speed correction unit 708 may be partially realized by dedicated hardware and partially realized by software or firmware. For example, the function of the target detection unit 701 may be realized by the processing circuit 51 as dedicated hardware, and the functions of the model creation unit 702, the target point candidate calculation unit 703, the combination detection unit 704, the movement direction speed estimation unit 705, the propagation path correction unit 706, the target position estimation unit 707, and the speed correction unit 708 may be realized by the processing circuit 51 reading out and executing programs stored in the memory 53.

[0093] In this way, the processing circuitry 51 can realize each of the above-described functions by hardware, software, firmware, or a combination of these.

[0094] Any of the components of the embodiments may be modified or omitted.

[0095] The signal processing device according to the present disclosure is capable of estimating the moving direction and speed of a target even when the information obtained by the radar contains errors, and is suitable for use in signal processing devices and the like.

[0096] 1 Transmitting antenna, 2 Receiving antenna, 3 Signal generator, 4 Frequency converter, 5 Filter, 6 AD converter, 7 Signal processing device, 51 Processing circuit, 52 CPU, 53 Memory, 701 Target detection unit, 702 Model creation unit, 703 Target candidate point calculation unit, 704 Combination detection unit, 705 Moving direction speed estimation unit, 706 Propagation path correction unit, 707 Target position estimation unit, 708 Speed ​​correction unit.

Claims

1. A signal processing device comprising: a target detection unit that detects detection points resulting from the mirror ghost of a target based on reflected waves of radio waves transmitted by a radar unit that are reflected by the target and received by the radar unit, and calculates the distance and direction of the detection points from the radar unit; a target candidate point calculation unit that calculates target candidate points by estimating the propagation path of the radio waves based on the distance and direction calculated by the target detection unit and information indicating structures present around the aircraft; a combination detection unit that detects combinations of target candidate points based on the target candidate points calculated by the target candidate point calculation unit; and a movement direction and speed estimation unit that estimates the movement direction and speed of the target based on the speed of the detection points detected by the target detection unit and the combination of target candidate points detected by the combination detection unit.

2. A signal processing device as claimed in claim 1, characterized in that it comprises: a propagation path correction unit that corrects the propagation path of radio waves based on the distance calculated by the target detection unit, the speed of the detected detection point, and the speed of the target estimated by the movement direction speed estimation unit; and a target position estimation unit that estimates the position of the target based on the propagation path of radio waves corrected by the propagation path correction unit.

3. A signal processing device according to claim 1 or claim 2, characterized in that the combination detection unit has a combination extraction unit that extracts combinations of target candidate points based on at least one of the distance from a reference position to the target candidate points calculated by the target candidate point calculation unit and the angular difference between the propagation paths at any two target candidate points.

4. The signal processing device according to claim 3, characterized in that, when the propagation paths of the target candidate points calculated by the target candidate point calculation unit are the same for both the outbound and return routes, the combination extraction unit calculates the angular difference of the propagation paths using the reflection direction of the radio waves at the target candidate point.

5. A signal processing device according to claim 3 or 4, characterized in that, when the propagation path of the target candidate point calculated by the target candidate point calculation unit is a propagation path with different round trip paths, the combination extraction unit calculates the angular difference of the propagation paths using an intermediate direction between the direction of incidence of the radio waves on the target candidate point and the direction of reflection of the radio waves at the target candidate point.

6. A signal processing device according to any one of claims 1 to 5, characterized in that the combination detection unit divides the target candidate points into a plurality of groups based on the density of the target candidate points calculated by the target candidate point calculation unit, and detects combinations of target candidate points for each group, and the movement direction and speed estimation unit estimates the movement direction and speed of the target for each group based on the combination of target candidate points for each group detected by the combination detection unit.

7. A radar device comprising: a radar section including a transmitting antenna for transmitting radio waves and a receiving antenna for receiving the radio waves transmitted by the transmitting antenna reflected by a target; and a signal processing device according to any one of claims 1 to 6.

8. A signal processing program for causing a computer to function as a signal processing device according to any one of claims 1 to 6.

9. A signal processing method comprising the steps of: a target detection unit detecting a detection point resulting from a mirror ghost of the target based on the reflected waves of radio waves transmitted by a radar unit that are reflected by the target and received by the radar unit, and calculating the distance and direction of the detection point from the radar unit; a target candidate point calculation unit calculating a target candidate point by estimating a propagation path of the radio waves based on the distance and direction calculated by the target detection unit and information indicating structures present in the vicinity of the aircraft; a combination detection unit detecting a combination of target candidate points based on the target candidate points calculated by the target candidate point calculation unit; and a movement direction and speed estimation unit estimating the movement direction and speed of the target based on the speed of the detection point detected by the target detection unit and the combination of target candidate points detected by the combination detection unit.

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