Radio wave sensor and method for supporting setting of radio wave sensor

Abstract

This radio wave sensor detects an object in a detection area at least partially including a road by irradiating the detection area with radio waves. The radio wave sensor comprises: a transmission antenna that irradiates the detection area with radio waves; a reception antenna that receives a reflected wave of the radio waves, which have been radiated from the transmission antenna and reflected by the object; an identification unit that identifies a reflection point at which the radio waves have been reflected, on the basis of the received reflected wave; a determination unit that determines whether the identified reflection point is a multiple reflection point resulting from multiple reflection; and a detection unit that detects an object in the detection area on the basis of the reflection point. The determination unit determines whether a determination condition for determining that the reflection point is the multiple reflection point is satisfied, and determines that the reflection point is the multiple reflection point if the determination condition is satisfied.

Description

Radio Wave Sensor and Method for Assisting in Setting Radio Wave Sensor

[0001] The present disclosure relates to a radio wave sensor and a method for assisting in setting a radio wave sensor. This application claims priority based on Japanese Application No. 2024-205526 filed on November 26, 2024, and incorporates all the descriptions described in the above Japanese application.

[0002] A radio wave sensor is installed at a position where it can detect objects such as vehicles and pedestrians on a road (including intersections) for the purpose of traffic monitoring. Such a radio wave sensor for infrastructure (road facilities) (hereinafter also referred to as an "infrastructure radio wave sensor") is used, for example, to measure the traffic volume of vehicles traveling on a road and to detect pedestrians on a crosswalk. In order to use a radio wave sensor for traffic monitoring, it is necessary to set an area to be detected (hereinafter referred to as a "detection area") such as a lane, a traffic lane, a crosswalk, and a sidewalk in the coordinate system of the radio wave sensor.

[0003] Patent Document 1 discloses a setting support device for assisting a user in setting a detection area of a radio wave sensor.

[0004] International Publication No. 2024 / 122371

[0005] The radio wave sensor according to an embodiment of the present disclosure irradiates a detection area including at least a part of a road with radio waves to detect an object in the detection area. The radio wave sensor includes a transmission antenna that irradiates the detection area with radio waves, a reception antenna that receives a reflected wave of the radio waves irradiated from the transmission antenna by the object, a specifying unit that specifies a reflection point that reflects the radio waves based on the received reflected wave, a determination unit that determines whether the specified reflection point is a multiple reflection point that is a reflection point due to multiple reflections, and a detection unit that detects an object in the detection area based on the reflection point. The determination unit determines whether a determination condition for the reflection point being the multiple reflection point is satisfied, and when the determination condition is satisfied, determines that the reflection point is the multiple reflection point.

[0006] Figure 1 is a diagram showing an example of the use of the infrastructure radio wave sensor according to the first embodiment. Figure 2 is a perspective view showing an example of the external configuration of the infrastructure radio wave sensor according to the first embodiment. Figure 3 is a diagram illustrating an example of setting the detection area in the sensor coordinate system. Figure 4 is a block diagram showing an example of the hardware configuration of the infrastructure radio wave sensor according to the first embodiment. Figure 5 is a functional block diagram showing an example of the functions of the infrastructure radio wave sensor according to the first embodiment. Figure 6 is a diagram illustrating the principle of multiple reflection. Figure 7 is a diagram illustrating the first principle of determining multiple reflection points by the infrastructure radio wave sensor according to the first embodiment. Figure 8 is a diagram illustrating the second principle of determining multiple reflection points by the infrastructure radio wave sensor according to the first embodiment. Figure 9 is a flowchart illustrating an example of the operation of the infrastructure radio wave sensor according to the first embodiment. Figure 10 is a block diagram showing an example of the hardware configuration of the setting support device according to the second embodiment. Figure 11 is a functional block diagram showing an example of the functions of the setting support device according to the second embodiment. Figure 12 is a diagram illustrating an example of determining a candidate area. Figure 13 is a flowchart illustrating an example of the setting support operation of the infrastructure radio wave sensor by the setting support device according to the second embodiment. Figure 14 is a functional block diagram showing an example of the functions of the setting support device according to the third embodiment. Figure 15 is a functional block diagram showing an example of the functions of the setting support device according to the fourth embodiment. Figure 16 is a flowchart showing an example of the setting support operation of an infrastructure radio wave sensor by the setting support device according to the fourth embodiment. Figure 17 is a functional block diagram showing an example of the functions of the setting support device according to the fifth embodiment. Figure 18 is a diagram illustrating an example of determining the type of object. Figure 19 is a diagram illustrating an example of displaying the type of object. Figure 20 is a flowchart showing an example of the setting support operation of an infrastructure radio wave sensor by the setting support device according to the fifth embodiment.

[0007] Infrastructure radio wave sensors are installed several meters above the road surface to detect a large area. In such infrastructure radio wave sensors, if highly reflective objects such as vehicles or guardrails (hereinafter also referred to as "highly reflective objects") are present within or near the detection area, reflection points due to multiple reflections via highly reflective objects may appear as noise.

[0008] According to this disclosure, the influence of noise due to multiple reflections on the detection results of infrastructure radio wave sensors can be reduced.

[0009] An overview of the embodiments of this disclosure will be described.

[0010] (1) The radio wave sensor according to the embodiment of the present disclosure detects an object in a detection area by irradiating the detection area, which includes at least a portion of a road, with radio waves. The radio wave sensor comprises a transmitting antenna that irradiates the detection area with radio waves, a receiving antenna that receives reflected waves from the object of the radio waves irradiated from the transmitting antenna, a identification unit that identifies a reflection point that reflects the radio waves based on the received reflected waves, a determination unit that determines whether the identified reflection point is a multiple reflection point that is a reflection point due to multiple reflection, and a detection unit that detects an object in the detection area based on the reflection point. The determination unit determines whether the determination condition for the reflection point being a multiple reflection point is met, and if the determination condition is met, it determines that the reflection point is a multiple reflection point. This makes it possible to identify multiple reflection points that cause noise among the reflection points measured by the radio wave sensor. Therefore, the influence of noise due to multiple reflection on the detection result of the radio wave sensor can be reduced.

[0011] (2) In (1) above, the determination condition is that there exists a second reflection point between the radio wave sensor and the first reflection point whose reflection intensity is higher than the first reference value, and the determination unit may determine that the first reflection point is the multiple reflection point when the determination condition is met. This makes it possible to identify the multiple reflection point from the reflection point measured by the radio wave sensor.

[0012] (3) In (1) above, the determination condition is that a second reflection point exists between the radio wave sensor and the first reflection point, and the size of the group of reflection points composed of a plurality of reflection points including the second reflection point is greater than the second reference value, and the determination unit may determine that the first reflection point is the multiple reflection point when the determination condition is met. This makes it possible to identify the multiple reflection point from the reflection point measured by the radio wave sensor.

[0013] (4) In any one of (1) to (3) above, the radio wave sensor may further include a determination unit that determines the multiple reflection points to be excluded from the reflection points used for detecting the object by the detection unit, based on the position of the multiple reflection points in the detection area. This reduces the influence of noise due to multiple reflections on the detection result of the radio wave sensor.

[0014] (5) In (4) above, the detection area includes a first area for detecting objects moving on the road and a second area for detecting objects waiting to move on the road, and the determination unit may determine the multiple reflection points included in the first area as the reflection points to be excluded. This reduces the influence of noise due to multiple reflections on the detection results in the first area.

[0015] (6) In (5) above, the determination unit does not have to determine the multiple reflection points included in the second area as the reflection points to be excluded. This reduces the decrease in detection accuracy due to misjudgment in the detection results in the second area, where there is a high possibility that a reflection point will be misjudged as a multiple reflection point.

[0016] (7) In (5) or (6) above, if an object detected is within a specific distance range from the multiple reflection point included in the first area, the determination unit does not have to determine the multiple reflection point as the reflection point to be excluded. An object located near the detected object may be mistakenly identified as a multiple reflection point. With the above configuration, the decrease in detection accuracy due to such misidentification can be reduced for the detection results in the first area.

[0017] (8) In any one of (4) to (7) above, the determination unit may determine the reflection point to be the excluded reflection point if the occurrence rate of the multiple reflection point at the position of the reflection point identified by the identification unit exceeds the third reference value. By estimating a position where multiple reflection points have appeared frequently in the past as a position where multiple reflection points repeatedly appear, and excluding the reflection point that appears at this position from the reflection points used for object detection, the influence of noise due to multiple reflections on the detection results of the radio wave sensor can be reduced.

[0018] (9) A radio wave sensor setting support method according to the embodiment of the present disclosure includes the steps of: acquiring reflection point information indicating the position on the road of a reflection point that reflects radio waves irradiated from the radio wave sensor toward the road; determining whether the reflection point is a multiple reflection point, which is a reflection point due to multiple reflection, based on the acquired reflection point information; and generating setting information for setting the radio wave sensor based on the determination result of the multiple reflection point. In the determination step, the setting support method determines whether the determination condition for the reflection point being a multiple reflection point is met, and if the determination condition is met, it is determined that the reflection point is a multiple reflection point. This makes it possible to identify multiple reflection points that cause noise among the reflection points measured by the radio wave sensor set by the setting support method. By using the determination result of such multiple reflection points for detection by the radio wave sensor, the influence of noise due to multiple reflection on the detection result of the radio wave sensor can be reduced.

[0019] (10) A radio wave sensor setting support method according to the embodiment of the present disclosure includes the steps of: acquiring multiple reflection point information indicating the position on the road of multiple reflection points resulting from multiple reflections of radio waves irradiated from the radio wave sensor toward the road; and generating setting information for setting the radio wave sensor based on the acquired multiple reflection point information. As a result, the radio wave sensor setting support method can utilize the determination result of multiple reflection points by the radio wave sensor for detection by the radio wave sensor, and can reduce the influence of noise due to multiple reflections on the detection result of the radio wave sensor.

[0020] (11) In (9) or (10) above, the radio wave sensor setting support method may further include the steps of: determining candidate areas which are candidates for exclusion areas to be excluded from the detection target of the radio wave sensor based on the multiple reflection points in the coordinate space set for the radio wave sensor; displaying the determined candidate areas on a display device; determining the candidate areas displayed on the display device as the exclusion areas, and generating the setting information in which the exclusion areas are specified. As a result, the radio wave sensor setting support method can determine areas in which multiple reflection points appear as exclusion areas, and can reduce the influence of noise due to multiple reflections on the detection results of the radio wave sensor.

[0021] (12) In (11) above, the radio wave sensor setting support method may include the step of determining an area in the coordinate space that includes a position in which the occurrence rate of the multiple reflection point exceeds a fourth reference value as the candidate area. The radio wave sensor setting support method estimates a position in which multiple reflection points have appeared frequently in the past as a position in which multiple reflection points appear repeatedly, and determines an exclusion area at this position, thereby reducing the influence of noise due to multiple reflections on the detection results of the radio wave sensor.

[0022] (13) In (9) or (10) above, the radio wave sensor setting support method may further include the step of determining an exclusion area to be excluded from the detection target of the radio wave sensor based on the multiple reflection points in the coordinate space set for the radio wave sensor, and generating the setting information in which the exclusion area is specified. As a result, the radio wave sensor setting support method can determine an area in which multiple reflection points appear as an exclusion area, and can reduce the influence of noise due to multiple reflections on the detection results of the radio wave sensor.

[0023] (14) In (13) above, the radio wave sensor setting support method may include the step of determining an area in the coordinate space that includes a position in which the occurrence rate of the multiple reflection point exceeds a fifth reference value as the exclusion area. The radio wave sensor setting support method estimates a position in which multiple reflection points have appeared frequently in the past as a position in which multiple reflection points appear repeatedly, and determines an exclusion area at this position, thereby reducing the influence of noise due to multiple reflections on the detection results of the radio wave sensor.

[0024] (15) In (13) above, the radio wave sensor setting support method further comprises the step of clustering the multiple multiple reflection points in the coordinate space set for the radio wave sensor based on the positions of the multiple multiple reflection points, and may also include the step of determining the exclusion area in the coordinate space based on the cluster of the multiple reflection points which is the result of the clustering. The radio wave sensor setting support method estimates areas where multiple reflection points have appeared frequently in the past as areas where multiple reflection points appear repeatedly, and determines an exclusion area in this area, thereby reducing the influence of noise due to multiple reflections on the detection results of the radio wave sensor.

[0025] (16) In (15) above, the radio wave sensor setting support method may further include the step of determining the type of object causing the multiple reflection points based on the location of the cluster in the detection area which includes at least a part of the road. For example, vehicles are present on roadways, trees are present on sidewalks, and guardrails are set up in median strips, and the types of objects present differ depending on the location on the road. With the above configuration, the radio wave sensor setting support method can set exclusion areas according to the type of object by determining the type of object causing the multiple reflections.

[0026] (17) In (16) above, the method for assisting the setting of the radio wave sensor may further include the step of displaying the determined type of object on a display device for each cluster. This allows the user to understand the type of object for each cluster and to consider the validity of the exclusion area.

[0027] This disclosure is implemented in the form of a radio wave sensor having the characteristic configuration described above, and a radio wave sensor setting support method with characteristic processing as steps, but is not limited to these. This disclosure may also be implemented in the form of an object detection method for a radio wave sensor with characteristic processing as steps, a setting support device having the characteristic configuration, a computer program for causing a radio wave sensor to perform characteristic processing, or a computer program for causing a setting support device to perform characteristic processing. This disclosure may be implemented in the form of a semiconductor integrated circuit in part or all of the control device for the radio wave sensor, or in part or all of the setting support device, or in a system that includes the radio wave sensor setting support device as part.

[0028] The embodiments of this disclosure will be described in detail below with reference to the drawings. At least some of the embodiments described below may be combined in any way.

[0029] [1. First Embodiment] [1-1. Infrastructure Radio Wave Sensor] Figure 1 shows an example of the use of the infrastructure radio wave sensor according to the first embodiment. The infrastructure radio wave sensor 10 according to the first embodiment is, for example, a radio wave radar for traffic monitoring and detects pedestrians at a crosswalk 20. The infrastructure radio wave sensor 10 is, for example, a millimeter-wave radar.

[0030] The pedestrian crossing 20 is provided on the roadway 60 near the intersection 61. Sidewalks 63a and 63b are provided adjacent to the roadway 60. The roadway 60 includes an inbound lane 62a for vehicles entering the intersection 61 and an outbound lane 62b for vehicles exiting the intersection 61. Sidewalk 63a is adjacent to the inbound lane 62a. Sidewalk 63b is adjacent to the outbound lane 62b.

[0031] The infrastructure radio wave sensor 10 is attached to a structure 50 provided on the sidewalk 63b. The structure 50 is several meters high, and the infrastructure radio wave sensor 10 is installed several meters above the ground. The structure 50 includes, for example, a pole 51 and an arm 52 provided near the upper end of the pole 51, to which the infrastructure radio wave sensor 10 is attached.

[0032] The infrastructure radio wave sensor 10 detects objects on the crosswalk 20 (e.g., pedestrians, cyclists) by irradiating radio waves (millimeter waves) onto the crosswalk 20 and receiving the reflected waves. Figure 2 is a perspective view showing an example of the external configuration of the infrastructure radio wave sensor 10 according to the first embodiment. As shown in Figure 2, the infrastructure radio wave sensor 10 includes a housing 18 having at least one transmitting / receiving surface 18a for transmitting and receiving radio waves. The housing 18 houses a transmitting / receiving unit 14 and a detection circuit 17. The transmitting / receiving unit 14 includes a transmitting antenna 15a and a plurality (e.g., four) receiving antennas 16a. The infrastructure radio wave sensor 10 transmits a modulated wave, which is a radio wave, from the transmitting antenna 15a through the transmitting / receiving surface 18a. The modulated wave hits an object and is reflected, and the receiving antennas 16a receive the reflected wave. The transmitting / receiving unit 14 and the detection circuit 17 perform signal processing on the transmitted wave signal and the received wave signal to detect the distance to the object, the speed of the object, and the azimuth angle in which the object is located.

[0033] Specifically, the infrastructure radio wave sensor 10 is positioned such that a straight line (hereinafter also referred to as the "projection center axis") is projected vertically onto the ground surface from the center of the transmitting and receiving surface 18a, which transmits and receives radio waves, and passes through the pedestrian crossing 20. The infrastructure radio wave sensor 10 can detect the distance from the infrastructure radio wave sensor 10 to the object, the velocity of the object (velocity in the straight line connecting the infrastructure radio wave sensor 10 and the object; hereinafter also referred to as the "line of sight velocity"), and the horizontal angle (azimuth angle) of the position where the object is located relative to the projection center axis.

[0034] [1-2. Detection Area] The infrastructure radio wave sensor 10 sets up a virtual detection area that corresponds to the detection area on the road for detecting objects. In Figure 1, the detection area 30 is shown as if the detection area exists in real space.

[0035] The detection area 30 is not limited to including only the area of ​​the pedestrian crossing. For example, an infrastructure radio wave sensor 10 used to control a traffic signal installed near a pedestrian crossing 20 is required not only to detect the amount of pedestrians or cyclists (including riders; hereinafter, pedestrians and cyclists are simply referred to as "pedestrians") passing through the pedestrian crossing 20, but also to detect pedestrians waiting to cross (an example of movement) on the sidewalk adjacent to the pedestrian crossing 20. In this case, the detection area 30 includes not only the area of ​​the pedestrian crossing 20, but also the area on the sidewalk where pedestrians wait to cross. That is, the detection area 30 may be an area extended from the pedestrian crossing 20 to the waiting areas on both sides in the longitudinal direction of the pedestrian crossing 20 (the direction in which pedestrians pass over the pedestrian crossing).

[0036] In the infrastructure radio wave sensor 10, a virtual coordinate space is set up to determine the position of an object. Hereinafter, the coordinate space set up in the infrastructure radio wave sensor 10 will also be referred to as the "sensor coordinate space".

[0037] In the infrastructure radio wave sensor 10, a virtual detection area corresponding to the detection area 30 in real space is set in the sensor coordinate space in order to detect objects on the pedestrian crossing 20. Hereinafter, the detection area set by the infrastructure radio wave sensor 10 is indicated by reference numeral 300.

[0038] Figure 3 is a diagram illustrating an example of setting the detection area 300 in the sensor coordinate system.

[0039] In Figure 3, the point indicated by reference numeral 31O is a point on the ground surface projected vertically downward from the installation position of the infrastructure radio wave sensor 10. The line indicated by reference numeral 31Y is the projection center axis, and the line indicated by reference numeral 31X is a line on the ground surface that intersects the projection center axis 31Y at point 31O.

[0040] For example, the sensor coordinate space is a two-dimensional coordinate space corresponding to the Earth's surface. The sensor coordinate space is defined by the X and Y axes. The origin O of the sensor coordinate space corresponds to a real-world point 31O. The Y axis of the sensor coordinate space corresponds to the real-world projection center axis 31Y. The X axis of the sensor coordinate space corresponds to the real-world line 31X.

[0041] The sensor coordinate space can be expressed not only as an XY orthogonal coordinate system but also as a polar coordinate system with the origin O as the pole and the Y-axis as the initial line.

[0042] In the infrastructure radio wave sensor 10, a virtual detection area 300 corresponding to the detection area 30 in the real space is set in the sensor coordinate space. The detection area 30 includes, for example, the crosswalk 20.

[0043] For example, the detection area 30 is divided into zebra areas 30_1A and 30_1B that are areas of the crosswalk 20, a median strip area 30_3 provided between the zebra area 30_1A and the zebra area 30_1B, a standby area 30_2A adjacent to the zebra area 30_1A, and a standby area 30_2B adjacent to the zebra area 30_1B. In the present embodiment, a zebra area is given as an example of the crosswalk 20, but it is not limited thereto. Crosswalks without stripes like a zebra are also included in the crosswalk 20.

[0044] The zebra area 30_1A is located closer to the point 31O (that is, the infrastructure radio wave sensor 10) than the zebra area 30_1B. Each of the zebra areas 30_1A and 30_1B is rectangular. The standby area 30_2A is in contact with the first side of the zebra area 30_1A close to the point 31O. The median strip area 30_3 is in contact with the second side of the zebra area 30_1A far from the point 31O, and the median strip area 30_3 is in contact with the first side of the zebra area 30_1B close to the point 31O. That is, the median strip area 30_3 is sandwiched by the zebra areas 30_1A and 30_1B. The standby area 30_2B is in contact with the second side of the zebra area 30_1B far from the point 31O.

[0045] The detection area 300 in the sensor coordinate space is divided into zebra areas 300_1A and 300_1B, standby areas 300_2A and 300_2B, and median strip area 300_3. Zebra area 300_1A corresponds to zebra area 30_1A in real space, and zebra area 300_1B corresponds to zebra area 30_1B in real space. Standby area 300_2A corresponds to standby area 30_2A in real space, and standby area 300_2B corresponds to standby area 30_2B in real space. Median strip area 300_3 corresponds to median strip area 30_3 in real space.

[0046] [1-3. Hardware Configuration of Infrastructure Radio Wave Sensor] Figure 4 is a block diagram showing an example of the hardware configuration of an infrastructure radio wave sensor according to the first embodiment. The infrastructure radio wave sensor 10 includes a processor 101, a non-volatile memory 102, a volatile memory 103, a transmitting / receiving unit 14, and a communication interface (communication I / F) 107.

[0047] The volatile memory 103 is a semiconductor memory such as SRAM (Static Random Access Memory) or DRAM (Dynamic Random Access Memory). The non-volatile memory 102 is a flash memory, hard disk, ROM (Read Only Memory), etc. The non-volatile memory 102 stores the control program 110, which is a computer program, and the data used to execute the control program 110. Each function of the infrastructure radio wave sensor 10 is performed when the control program 110 is executed by the processor 101. The control program 110 can be stored in a recording medium such as flash memory, ROM, or CD-ROM. The processor 101 can detect the position (distance and azimuth) and velocity of an object using the control program 110.

[0048] The processor 101 is, for example, a CPU (Central Processing Unit). However, the processor 101 is not limited to the CPU. The processor 101 may be a GPU (Graphics Processing Unit). The processor 101 may be, for example, an ASIC (Application Specific Integrated Circuit), or a programmable logic device such as an FPGA (Field Programmable Gate Array) or a CPLD (Complex Programmable Logic Device). In this case, the ASIC or the programmable logic device is configured to be able to execute the same processing as the control program 110.

[0049] The transceiver unit 14 includes a transmission circuit 15 and a reception circuit 16.

[0050] The transmission circuit 15 includes a transmission antenna 15a. The number of the transmission antennas 15a is not limited to one and may be plural. The transmission circuit 15 generates a modulated wave and transmits the generated modulated wave from the transmission antenna 15a. The transmitted modulated wave hits an object (e.g., a pedestrian, a bicycle, a vehicle) and is reflected.

[0051] The reception circuit 16 includes a reception antenna 16a. A plurality (four in FIG. 4) of reception antennas 16a are provided to detect the azimuth angle of an object. The reception circuit 16 performs signal processing on the received reflected wave. The reflected wave data generated by the signal processing is provided to the processor 101. The processor 101 analyzes the reflected wave data and detects the position (distance and azimuth angle) and speed of the object.

[0052] The communication I / F 107 can communicate with an external device. The communication I / F 107 is connected to the setting support device 200 (see FIG. 10) via a cable and can transmit the detection result data to the setting support device 200. The communication I / F 107 is a wireless communication interface and may communicate with the setting support device 200 wirelessly.

[0053] The non-volatile memory 102 stores the configuration information 111. The configuration information 111 includes the position information of the detection area 300 in the sensor coordinate space, and the position information of the mask area, which will be described later.

[0054] [1-4. Functions of the Infrastructure Radio Wave Sensor] Figure 5 is a functional block diagram showing an example of the functions of the infrastructure radio wave sensor according to the first embodiment. When the processor 101 executes the control program 110, the infrastructure radio wave sensor 10 functions as a specific unit 121, a determination unit 122, a decision unit 123, a detection unit 124, a tracking unit 125, and an output unit 126.

[0055] The transmitting circuit 15 included in the transmitting / receiving unit 14 transmits a transmission signal, which is a modulated wave, from the transmitting antenna 15a. The transmission signal from the transmitting antenna 15a is reflected when it hits an object. The receiving antenna 16a receives the reflected wave from the object. The identification unit 121 combines the modulated wave signal output from the transmitting circuit 15 and the reflected wave signal output from the receiving circuit 16 to generate an intermediate frequency signal (hereinafter referred to as the "IF signal"). The identification unit 121 applies a Fast Fourier Transform (FFT) to the IF signal to obtain distance, velocity, and azimuth angle information. The identification unit 121 generates reflected wave data based on the obtained distance and azimuth angle information.

[0056] Each peak point in the reflected wave data is a reflection point. That is, the reflected wave data contains one or more reflection points. The identification unit 121 identifies the reflection points that reflect radio waves. Specifically, the identification unit 121 identifies the position of the reflection point, i.e., the distance between the reflection point and the infrastructure radio wave sensor 10, and the azimuth angle of the position where the reflection point exists. The position of the reflection point is expressed as coordinate values ​​in polar coordinates.

[0057] The identification unit 121 extracts reflection points, which are peak points included in the reflected wave data. The reflected wave data includes data showing the waveform of the reflected wave with respect to distance and data showing the waveform of the reflected wave with respect to angle. The identification unit 121 extracts peak points from both the waveform of the reflected wave with respect to distance and the waveform of the reflected wave with respect to angle. The identification unit 121 identifies the reflection points by associating the peak points in the reflected wave with respect to distance with the peak points in the reflected wave with respect to angle.

[0058] The identification unit 121 further identifies the reflection intensity at the reflection point. For example, the identification unit 121 identifies the signal-to-noise ratio (SNR) of the reflection point. The SNR is the ratio of the signal level to the noise level, and the higher the SNR, the smaller the influence of noise on the signal. The SNR is one example of reflection intensity.

[0059] The determination unit 122 determines whether the reflection point identified by the identification unit 121 is a multiple reflection point, which is a reflection point due to multiple reflections.

[0060] Figure 6 is a diagram illustrating the principle of multiple reflection. Radio waves emitted from the infrastructure radio wave sensor 10 travel toward the object to be detected (a vehicle in the example of Figure 6), are reflected by the object, and the reflected waves are received by the infrastructure radio wave sensor 10. The infrastructure radio wave sensor 10 measures the reflection point, which is a real image Ri, at the position of the object.

[0061] For example, if an object RO (a guardrail in the example of Figure 6) with a highly reflective surface exists between the object to be detected and the infrastructure radio wave sensor 10, a portion of the radio waves emitted from the infrastructure radio wave sensor 10 will be reflected by object RO, and then those reflected waves will be reflected again by the object to be detected. The path of radio waves due to such multiple reflections is longer than the path of radio waves due to normal reflection. Therefore, the infrastructure radio wave sensor 10 measures multiple reflection points due to the virtual image Vi at a position farther away than the reflection points due to the real image Ri.

[0062] Figure 7 is a diagram illustrating the first principle of determining multiple reflection points using an infrastructure radio wave sensor according to the first embodiment. The determination unit 122 determines that the first reflection point is a multiple reflection point if there is a second reflection point between the infrastructure radio wave sensor 10 and the first reflection point whose reflection intensity is higher than a first reference value. The first reference value may be the reflection intensity of the first reflection point. The first reference value may be a reference value calculated based on the reflection intensity of the first reflection point. For example, the first reference value is (reflection intensity of the first reflection point + α), where α may be negative. Figure 7 shows a first example of the position of the measured reflection point in the sensor coordinate space. In the example of Figure 7, two reflection points, reflection point RP1 and reflection point RP2, are measured by the infrastructure radio wave sensor 10. Reflection point RP1 is measured at a distance D1 and azimuth angle θ1. Reflection point RP2 is measured at a distance D2 and azimuth angle θ2.

[0063] In the example shown in Figure 7, reflection point RP1 is located closer to the infrastructure radio wave sensor 10 than reflection point RP2. The azimuth angle θ1 of reflection point RP1 is close to the azimuth angle θ2 of reflection point RP2. That is, reflection point RP1 is located between the infrastructure radio wave sensor 10 and reflection point RP2. In the example shown in Figure 7, reflection point RP2 corresponds to the "first reflection point," and reflection point RP1 corresponds to the "second reflection point."

[0064] Objects that cause multiple reflections (a vehicle in the example in Figure 6) are objects with a surface that has high reflectivity. Reflectivity depends on surface roughness. That is, if the surface of an object is smooth, the reflectivity is high, and if the surface is rough, the reflectivity is low. Since multiple reflection is a phenomenon in which radio waves are repeatedly reflected, multiple reflections are more likely to occur in objects with high reflectivity. In objects with low reflectivity, radio waves are attenuated, and multiple reflections are less likely to occur.

[0065] The determination unit 122 determines, for example, whether a reflection point is a multiple reflection point according to the first determination conditions for multiple reflections. The first determination conditions include, for example, the following conditions (1-1) and (1-2): (1-1) The difference between the azimuth angles θ1 and θ2 of the two reflection points RP1 and RP2 is less than a threshold. (1-2) The signal-to-noise ratio of the reflection point RP1, which is closer to the infrastructure radio wave sensor 10 of the two reflection points RP1 and RP2, is greater than a first reference value.

[0066] The determination unit 122 determines that the reflection point RP2 is a multiple reflection point if the first determination condition is met, that is, if both conditions (1-1) and (1-2) are met. The determination unit 122 determines that the reflection point RP2 is not a multiple reflection point if the first condition is not met, that is, if at least one of conditions (1-1) and (1-2) is not met. In Figure 7, a normal reflection point (a reflection point that is not a multiple reflection point) is shown with a circular mark, and a multiple reflection point is shown with a square mark.

[0067] Figure 8 is a diagram illustrating the second principle of determining multiple reflection points by an infrastructure radio wave sensor according to the first embodiment. The determination unit 122 determines that the first reflection point is a multiple reflection point if a second reflection point exists between the infrastructure radio wave sensor 10 and the first reflection point, and the size of the reflection point group composed of multiple reflection points including the second reflection point is greater than the second reference value. The second reference value may be the reflection area of ​​a typical vehicle. The second reference value may be a reference value calculated based on the reflection area of ​​a typical vehicle. The second reference value may be the number of reflection points reflected from a typical vehicle. The second reference value may be a reference value calculated based on the number of reflection points reflected from a typical vehicle. Figure 8 shows a second example of the position of the measured reflection points in the sensor coordinate space. In the example of Figure 8, the infrastructure radio wave sensor 10 measures multiple reflection points, including reflection point RP1 and reflection point RP2. Reflection point RP1 is measured at a distance D1 and azimuth angle θ1. Reflection point RP2 is measured at a distance D2 and azimuth angle θ2.

[0068] In the example shown in Figure 8, multiple reflection points exist in the vicinity of reflection point RP1. For example, the determination unit 122 can cluster multiple reflection points. For example, clustering is performed based on the distance between each reflection point. That is, the determination unit 122 includes multiple points that exist within a certain distance range into one cluster (group of reflection points). For example, in addition to the distance between reflection points, clustering may also use the signal-to-noise ratio of each reflection point. In the example shown in Figure 8, cluster CL is composed of multiple reflection points, including reflection point RP1.

[0069] In the example shown in Figure 8, reflection point RP1 is located closer to the infrastructure radio wave sensor 10 than reflection point RP2. The azimuth angle θ1 of reflection point RP1 is close to the azimuth angle θ2 of reflection point RP2. That is, reflection point RP1 is located between the infrastructure radio wave sensor 10 and reflection point RP2. In the example shown in Figure 8, reflection point RP2 corresponds to the "first reflection point," and reflection point RP1 corresponds to the "second reflection point."

[0070] Objects that cause multiple reflections (a vehicle in the example in Figure 6) are objects with a surface area above a certain size. The number of reflection points measured from a single object depends on the object's surface area. That is, if the surface area of ​​an object is large, there will be more locations where reflection intensity peaks appear, and if the surface area of ​​an object is small, there will be fewer locations where reflection intensity peaks appear. Objects with a large surface area are likely to cause multiple reflections because radio waves are reflected in various directions. On the other hand, objects with a small surface area are less likely to cause multiple reflections.

[0071] The determination unit 122 determines, for example, whether a reflection point is a multiple reflection point according to the second determination condition for multiple reflections. The second determination condition includes, for example, the following conditions (2-1) and (2-2): (2-1) The difference between the azimuth angles θ1 and θ2 of two reflection points RP1 and RP2 is less than a threshold. (2-2) The size of a cluster formed by multiple reflection points, including the reflection point RP1 that is closer to the infrastructure radio wave sensor 10 among the two reflection points RP1 and RP2, is greater than the second reference value.

[0072] For example, the cluster size in condition (2-2) is the area of ​​the cluster. In another example, the cluster size in condition (2-2) is the number of reflection points in the cluster.

[0073] The determination unit 122 determines that the reflection point RP2 is a multiple reflection point if the second determination condition is met, that is, if both conditions (2-1) and (2-2) are met. The determination unit 122 determines that the reflection point RP2 is not a multiple reflection point if the second condition is not met, that is, if at least one of conditions (2-1) and (2-2) is not met.

[0074] The determination unit 122 determines whether a reflection point is a multiple reflection point using at least one of the first determination condition and the second determination condition. In the first embodiment, the determination unit 122 determines whether a reflection point is a multiple reflection point using both the first determination condition and the second determination condition.

[0075] Returning to Figure 5, the detection unit 124 detects an object in the detection area 300 based on the reflection point identified by the identification unit 121.

[0076] The radio waves emitted from the infrastructure radio wave sensor 10 may be reflected simultaneously by multiple objects. The detection unit 124 clusters the reflection points on the same object. The clustering by the detection unit 124 may be the same as the clustering by the determination unit 122, or it may be different from the clustering by the determination unit 122. In one example, the detection unit 124 determines a representative value for the reflection points belonging to the same cluster and sets the determined representative value to the position of the object. For example, the representative value is the centroid. However, the position of the object may be a representative value other than the centroid of the multiple reflection points. For example, the representative value may be the average value of the reflection points, or the median value of the reflection points.

[0077] A transmitting signal (chirp) is transmitted from the transmitting antenna 15a at regular intervals. A moving object reflects the transmitting signal at two different points, and the receiving antenna 16a receives each reflected wave. The detection unit 124 detects the line-of-sight velocity of the object from the phase difference of multiple IF signals obtained from the moving object.

[0078] Based on the positions of the multiple reflection points in the detection area 300, the determination unit 123 determines the multiple reflection points to be excluded from the reflection points used for object detection by the detection unit 124.

[0079] For example, the determination unit 123 determines that multiple reflection points included in zebra areas 300_1A and 300_1B, which are areas for detecting moving objects in the detection area 300, are to be excluded reflection points. This reduces the misidentification of pedestrians crossing the crosswalk 20 as noise due to multiple reflections. Zebra areas 300_1A and 300_1B are examples of the "first area".

[0080] For example, if an object is detected within a specific distance range from a multiple reflection point included in zebra areas 300_1A and 300_1B, the determination unit 123 will not determine the multiple reflection point as an excluded reflection point. A group of pedestrians in close proximity to each other may move across the crosswalk 20 in the same direction. In such a case, it is conceivable that reflection points from multiple pedestrians may meet the first or second determination condition described above and be incorrectly determined as a multiple reflection point. Therefore, in zebra areas 300_1A and 300_1B, if an object is detected within a circle with a specific distance radius centered on the multiple reflection point (hereinafter also referred to as the "exception range"), the above-mentioned misdetermination can be reduced by not determining the multiple reflection point as an excluded reflection point.

[0081] For example, the determination unit 123 does not determine multiple reflection points included in the waiting areas 300_2A, 300_2B and the median strip area 300_3 as reflection points to be excluded. This reduces the possibility of misidentifying multiple reflection points caused by objects such as guardrails, trees, utility poles, traffic signals, and signs present in the waiting areas 300_2A, 300_2B and the median strip area 300_3 as stationary pedestrians. The waiting areas 300_2A, 300_2B and the median strip area 300_3 are examples of the "second area".

[0082] The tracking unit 125 tracks the detected objects. Specifically, the tracking unit 125 assigns an ID to each object detected by the detection unit 124. The detection unit 124 outputs detection results of the object's position and line-of-sight velocity at regular time intervals. The tracking unit 125 identifies objects that are the same as previously detected objects from among the objects detected this time. For example, the tracking unit 125 estimates the current position of object a based on the previous movement direction and velocity of object a. The tracking unit 125 identifies the object closest to the position estimated from the previous movement direction and velocity of object a as object a from among the objects detected this time. An object identified as identical to the previously detected object inherits the ID of the previously detected object.

[0083] The output unit 126 outputs the object detection results from the infrastructure radio wave sensor 10. The detection results include the object's position (distance and azimuth), velocity, ID, and time information indicating the detection time. The output unit 126 outputs the object detection results at regular time intervals.

[0084] [1-5. Operation of the Infrastructure Radio Wave Sensor] The operation of the infrastructure radio wave sensor 10 according to the first embodiment will be described below.

[0085] Figure 9 is a flowchart showing an example of the operation of an infrastructure radio wave sensor according to the first embodiment.

[0086] When the processor 101 starts the control program 110, the infrastructure radio wave sensor 10 executes the process described below. The process shown in Figure 9 is executed once in the repeated control cycle. In other words, the process shown in Figure 9 is executed repeatedly.

[0087] The transmitting circuit 15 generates a modulated wave and transmits the generated modulated wave from the transmitting antenna 15a. The transmitted modulated wave strikes an object (pedestrian, bicycle, vehicle), and the receiving antenna 16a receives the reflected wave from the object. The receiving circuit 16 processes the reflected wave signal and generates reflected wave data. The processor 101 receives the reflected wave data (step S101).

[0088] The processor 101 analyzes the reflected wave data and identifies the reflection point (step S102).

[0089] The processor 101 clusters the reflection points based on the distance between them (step S103).

[0090] The processor 101 selects one of the identified reflection points (step S104). In step S104, the processor 101 does not select a reflection point that has already been selected in one control cycle.

[0091] The processor 101 determines whether at least one of the first and second determination conditions described above is met based on the identified reflection point (step S105).

[0092] If at least one of the first and second determination conditions is met (YES in step S105), the processor 101 determines that the reflection point is a multiple reflection point (step S106). If neither the first nor the second determination condition is met (NO in step S105), the processor 101 proceeds to step S110.

[0093] The processor 101 determines whether or not multiple reflection points exist in zebra areas 300_1A and 300_1B (step S107). If multiple reflection points exist in zebra areas 300_1A and 300_1B (YES in step S107), the processor 101 determines, for example, whether or not the object detected in the previous control cycle is included in the exception range (step S108). If the detected object is not included in the exception range (NO in step S108), the processor 101 determines that the multiple reflection points are to be excluded reflection points (step S109).

[0094] If the multiple reflection point is located in the waiting area 300_2A, 300_2B, or the median strip area 300_3 (NO in step S107), the processor 101 does not determine the multiple reflection point to be excluded. Similarly, if the detected object is located within the exception range (YES in step S108), the processor 101 also does not determine the multiple reflection point to be excluded.

[0095] The processor 101 determines whether all reflection points identified in the current control cycle have been selected (step S110). If there are any reflection points that have not been selected (NO in step S110), the processor 101 returns to step S104.

[0096] If all reflection points are selected (YES in step S110), the processor 101 clusters the reflection points on the same object and detects the position and velocity of the object (step S111).

[0097] The processor 101 identifies objects detected in the current control cycle that are the same as those detected in the previous control cycle (step S112). Objects identified as identical to those detected in the previous control cycle inherit the ID of the object detected in the previous control cycle.

[0098] The processor 101 outputs the detection result, including the object's position, velocity, and ID (step S113), and returns to step S101. As a result, the infrastructure radio wave sensor 10 outputs the detection result at a constant control cycle.

[0099] Each of the above-described processes (functions) in the infrastructure radio wave sensor 10 of this embodiment may be executed by a processing circuit (Circuitry) that includes at least one processor. In addition to the processor, the processing circuit may consist of a circuit such as an integrated circuit that combines at least one memory, various analog circuits, and various digital circuits.

[0100] [2. Second Embodiment] [2-1. Setting Support Device] The infrastructure radio wave sensor 10 is set using the setting support device. Specifically, the setting support device is used to set the detection area 300 and the mask area of ​​the infrastructure radio wave sensor 10. For example, after the user attaches the infrastructure radio wave sensor 10 to the structure 50, the user connects the setting support device to the infrastructure radio wave sensor 10 and sets the infrastructure radio wave sensor 10. The configuration of the infrastructure radio wave sensor 10 is the same as the configuration of the infrastructure radio wave sensor 10 described in the first embodiment, so the same reference numerals are used for the same components and their descriptions are omitted.

[0101] [2-2. Hardware Configuration of the Setting Support Device] Figure 10 is a block diagram showing an example of the hardware configuration of the setting support device according to the second embodiment. The setting support device 200 according to the second embodiment includes a processor 201, a non-volatile memory 202, a volatile memory 203, an input / output interface (I / O) 204, a graphics controller 205, and a communication interface (communication I / F) 206. The setting support device 200 further includes an input device 211 and a display device 212. At least one of the input device 211 and the display device 212 may be an external device connected to the setting support device 200.

[0102] The volatile memory 203 is, for example, a semiconductor memory such as SRAM or DRAM. The non-volatile memory 202 is, for example, flash memory, a hard disk, or ROM. The non-volatile memory 202 stores the setting support program 210, which is a computer program, and the data used to execute the setting support program 210. Each function of the setting support device 200 is performed when the setting support program 210 is executed by the processor 201. The setting support program 210 can be stored in a recording medium such as flash memory, ROM, or CD-ROM. The processor 201 determines the mask area of ​​the infrastructure radio wave sensor 10 based on the setting support program 210.

[0103] The processor 201 is, for example, a CPU. However, the processor 201 is not limited to a CPU. The processor 201 may be a GPU. The processor 201 may be, for example, an ASIC, or a programmable logic device such as an FPGA or CPLD. In this case, the ASIC or programmable logic device is configured to perform the same processing as the setting support program 210.

[0104] For example, the input device 211 includes a keyboard and a pointing device such as a mouse. The input device 211 may also be a capacitive or pressure-sensitive touchpad superimposed on the screen of the display device 212. The input device 211 is used to input data to the setting support device 200. The input / output interface 204 is connected to the input device 211. The input / output interface 204 receives input data from the input device 211 and provides the received data to the processor 201.

[0105] The display device 212 includes, for example, a liquid crystal panel or an OEL (organic electroluminescent) panel. The display device 212 can display character or graphic information. The graphics controller 205 is connected to the display device 212 and controls the display on the display device 212. The graphics controller 205 includes, for example, a GPU and VRAM (Video RAM), and stores data to be displayed on the display device 212 in VRAM, periodically reads one frame of video data from VRAM, and generates a video signal. The generated video signal is output to the display device 212, and the video is displayed on the display device 212. The functions of the graphics controller 205 may be included in the processor 201. A portion of the volatile memory 203 may be used as VRAM.

[0106] The communication interface 206 can communicate with external devices. For example, the communication interface 206 can be connected to the infrastructure radio wave sensor 10 by a communication cable and communicate with the infrastructure radio wave sensor 10. The communication interface 206 is a wireless communication interface and may communicate with the infrastructure radio wave sensor 10 wirelessly.

[0107] [2-3. Functions of the Setting Support Device] Figure 11 is a functional block diagram showing an example of the functions of the setting support device according to the second embodiment. When the processor 201 executes the setting support program 210, the setting support device 200 functions as a first acquisition unit 221, a determination unit 222, a first decision unit 223, a display control unit 224, a second decision unit 225, and a generation unit 226.

[0108] The infrastructure radio wave sensor 10 can be set to two operating modes: a setting mode and an operation mode. The setting mode is the operating mode for setting a mask area on the infrastructure radio wave sensor 10. The operation mode is the operating mode for detecting objects for traffic monitoring after the mask area has been set.

[0109] When setting the mask area, the infrastructure radio wave sensor 10 is started in setting mode. The setting support device 200 communicates with the infrastructure radio wave sensor 10, which is operating in setting mode, and sets the mask area.

[0110] In setting mode, the infrastructure radio wave sensor 10 detects objects to set the mask area. In object detection by the infrastructure radio wave sensor 10 in setting mode, for example, the identification of multiple reflection points and the determination of reflection points to be excluded are not performed. Other object detection operations by the infrastructure radio wave sensor 10 are the same as those described in the first embodiment.

[0111] The first acquisition unit 221 acquires detection data 213, which includes the detection results from the infrastructure radio wave sensor 10. In one example, the infrastructure radio wave sensor 10 in setting mode detects objects on the road for a certain detection period. For example, the detection period is a period of 1 second or more and 1 hour or less. For example, the detection period is a period that includes multiple control cycles. The infrastructure radio wave sensor 10 continuously detects the position of objects during the detection period. The detection data 213 output from the infrastructure radio wave sensor 10 includes reflection point information for all reflection points detected during the detection period. The reflection point information includes the sensor coordinates, velocity, and signal-to-noise ratio of the reflection point.

[0112] The determination unit 222 determines whether a reflection point is a multiple reflection point based on the reflection point information acquired by the first acquisition unit 221. The determination by the determination unit 222 as to whether a reflection point is a multiple reflection point is the same as the determination by the determination unit 122 as described in the first embodiment, so the explanation is omitted.

[0113] The first decision unit 223 determines candidate areas in the sensor coordinate space that are candidates for mask areas to be excluded from detection by the infrastructure radio wave sensor 10, based on the multiple reflection points. A mask area is an example of an "exclusion area".

[0114] In one example, the first determination unit 223 determines an area in the sensor coordinate space that includes a position where the occurrence rate of multiple reflection points exceeds a fourth reference value as a candidate area. The fourth reference value can be set appropriately. The fourth reference value may be set to three times in 15 minutes. In this case, the first determination unit 223 determines cells that appear at a rate exceeding three times in 15 minutes as a candidate area.

[0115] Figure 12 illustrates an example of determining a candidate area. Figure 12 shows the sensor coordinate space. For example, the sensor coordinate space is divided into multiple cells. In the example in Figure 12, the cells are divided according to a polar coordinate system defined by the pole O and the initial line Y. That is, multiple half-lines extending radially from pole O are defined at equal angular intervals, and semicircles centered on pole O are defined to spread out from pole O at equal intervals, and a single figure enclosed by adjacent half-lines and adjacent semicircles is a cell. In other words, in the example in Figure 12, each cell has a sector shape with its tip missing in an arc shape.

[0116] The first determination unit 223 counts the number of multiple reflection points contained in each cell. Furthermore, the first determination unit 223 calculates the occurrence rate of multiple reflection points for each cell. For example, the occurrence rate of multiple reflection points is the result of dividing the number of multiple reflection points contained in one cell of interest by the number of control cycles included in the detection period.

[0117] The first determination unit 223 calculates the occurrence rate of multiple reflection points for all cells and identifies cells in which the occurrence rate of multiple reflection points exceeds the fourth reference value. In the example in Figure 12, it is assumed that the occurrence rate of multiple reflection points exceeds the fourth reference value in each of cells CE1, CE2, CE3, CE4, CE5, and CE6, while the occurrence rate of multiple reflection points does not exceed the fourth reference value in the other cells.

[0118] The first determination unit 223 determines which cells from among the multiple cells are to be excluded, which are cells that will not be used for object detection. In one example, the first determination unit 223 determines cells CE1, CE2, CE3, CE4, CE5, and CE6, in which the occurrence rate of multiple reflection points exceeds the fourth criterion value, as cells to be excluded.

[0119] The first decision unit 223 clusters the cells to be excluded. For example, if two or more adjacent cells are all cells to be excluded, these excluded cells form a single cluster. In the example in Figure 12, cluster CL1 is composed of cells CE1, CE2, CE3, CE4, CE5, and CE6.

[0120] The first decision unit 223 determines each cluster formed by clustering as a candidate area. In the example in Figure 12, cluster CL1 is determined as a candidate area. The first decision unit 223 is an example of a "clustering unit".

[0121] Returning to Figure 11, the display control unit 224 causes the candidate area determined by the first determination unit 223 to be displayed on the display device 212. In one example, the display control unit 224 causes the candidate area in the sensor coordinate space to be displayed on the display device 212. The display control unit 224 may also superimpose the detection area 300 and the candidate area on the display device 212.

[0122] The display device 212 displays a mask area setting screen in which candidate areas are placed in the sensor coordinate space. The display control unit 224 displays the candidate areas together with the detection area 300 on the display device 212. That is, in the mask area setting screen, the detection area 300 and the candidate areas are displayed simultaneously in the sensor coordinate space defined by the X and Y axes.

[0123] Because the detection area 300 and the candidate areas are displayed simultaneously, the user can understand the positional relationship between each candidate area and the detection area 300. For example, by comparing the positional relationship between each candidate area and the detection area 300 with the positional relationship between each object in real space and the detection area 30 (or crosswalk 20), the user can recognize which object each candidate area corresponds to.

[0124] The second determination unit 225 determines the candidate area displayed on the display device 212 as the mask area. For example, the user can specify a candidate area to be used as the mask area using the input device 211. The second determination unit 225 determines the candidate area specified by the user as the mask area.

[0125] The generation unit 226 generates setting information 111 for setting the infrastructure radio wave sensor 10 based on the determination result of the multiple reflection point determination by the determination unit 222. The setting information 111 includes mask area information in which the position, size, and shape of the mask area are specified.

[0126] For example, the setting support device 200 sets up the infrastructure radio wave sensor 10 by transmitting the generated setting information 111 to the infrastructure radio wave sensor 10. The infrastructure radio wave sensor 10 can set a mask area by storing the received setting information 111 in the non-volatile memory 102. In the operating mode, the infrastructure radio wave sensor 10 with the mask area set detects objects without using reflection points that appear in the mask area.

[0127] [2-4. Operation of the setting support device (setting support method)] Figure 13 is a flowchart showing an example of the setting support operation (setting support method) of an infrastructure radio wave sensor by the setting support device according to the second embodiment.

[0128] The processor 201 of the setting support device 200 starts the infrastructure radio wave sensor 10 in setting mode (step S201).

[0129] When the infrastructure radio wave sensor 10 is started in setting mode, the infrastructure radio wave sensor 10 detects an object (its position and velocity). The infrastructure radio wave sensor 10 transmits detection data 213. The processor 201 acquires the detection data 213 transmitted from the infrastructure radio wave sensor 10 by receiving it (step S202).

[0130] The processor 201 selects one of the reflection points specified in the acquired detection data 213 (step S203). In step S203, the processor 201 does not select a reflection point that has already been selected.

[0131] The processor 201 determines whether at least one of the first and second determination conditions described above is met based on the selected reflection point (step S204).

[0132] If at least one of the first and second determination conditions is met (YES in step S204), the processor 201 determines that the reflection point is a multiple reflection point (step S205). If neither the first nor the second determination condition is met (NO in step S204), the processor 201 proceeds to step S206.

[0133] The processor 201 determines whether all reflection points specified in the detection data 213 have been selected (step S206). If there are reflection points that have not been selected (NO in step S206), the processor 201 returns to step S203.

[0134] If all reflection points are selected (YES in step S206), the processor 201 calculates the occurrence rate of multiple reflection points for each cell (step S207).

[0135] The processor 201 compares the occurrence rate calculated for each cell with a third reference value and determines cells whose occurrence rate is greater than the third reference value to be excluded (step S208). Excluded cells are an example of "excluded reflection points". The third reference value can be set appropriately. The third reference value may be set to three times in 15 minutes. In this case, when multiple reflections are determined, the processor 201 determines cells that appear three or more times in 15 minutes to be excluded.

[0136] The processor 201 clusters the cells to be excluded and determines the formed clusters to be candidate areas (step S209).

[0137] The processor 201 causes the display device 212 to display the detection area and the candidate area (step S210).

[0138] The user specifies a candidate area to be used as the mask area using the input device 211. The processor 201 accepts the specification of the candidate area to be used as the mask area (step S211).

[0139] The processor 201 determines the candidate area specified by the user as the mask area (step S212).

[0140] The processor 201 generates setting information 111 specifying the position, size, and shape of each determined mask area (step S213). The processor 201 transmits the generated setting information 111 to the infrastructure radio wave sensor 10, thereby setting the mask area on the infrastructure radio wave sensor 10 (step S214). This completes the setting support operation.

[0141] [3. Third Embodiment] The configuration of the setting support device according to the third embodiment is the same as the configuration of the setting support device 200 according to the second embodiment, so the same reference numerals are used for the same components and their descriptions are omitted.

[0142] Figure 14 is a functional block diagram showing an example of the functions of the setting support device according to the third embodiment. The setting support device 200 according to the third embodiment does not have a determination function to determine whether or not a reflection point is a multiple reflection point. When the processor 201 executes the setting support program 210, the setting support device 200 functions as a second acquisition unit 321, a first determination unit 223, a display control unit 224, a second determination unit 225, and a generation unit 226.

[0143] The second acquisition unit 321 acquires detection data 213 from the infrastructure radio wave sensor 10, which has a determination function for determining whether or not a reflection point is a multiple reflection point, including multiple reflection point information in addition to the reflection point information mentioned above.

[0144] The first determination unit 223, display control unit 224, second determination unit 225, and generation unit 226 in the third embodiment are the same as the first determination unit 223, display control unit 224, second determination unit 225, and generation unit 226 in the second embodiment, so their description is omitted.

[0145] [4. Fourth Embodiment] The configuration of the setting support device according to the fourth embodiment is the same as the configuration of the setting support device 200 according to the second embodiment, so the same reference numerals are used for the same components and their descriptions are omitted.

[0146] [4-1. Functions of the Setting Support Device] Figure 15 is a functional block diagram showing an example of the functions of the setting support device according to the fourth embodiment. The setting support device 200 according to the fourth embodiment does not have a function to determine candidate areas. The setting support device 200 according to the fourth embodiment determines the mask area without determining candidate areas based on multiple reflection points. When the processor 201 executes the setting support program 210, the setting support device 200 functions as a first acquisition unit 221, a determination unit 222, a third determination unit 423, a display control unit 224, and a generation unit 226.

[0147] The first acquisition unit 221 and the determination unit 222 in the fourth embodiment are the same as the first acquisition unit 221 and the determination unit 222 in the second embodiment, so their description is omitted.

[0148] The third decision unit 423 determines, based on the multiple reflection points, a mask area to be excluded from the detection target of the infrastructure radio wave sensor 10 in the sensor coordinate space.

[0149] In one example, the third determination unit 423 determines an area in the sensor coordinate space that includes a position where the occurrence rate of multiple reflection points exceeds a fifth reference value as a mask area. The fifth reference value can be set appropriately. The fifth reference value may be set to three times every 15 minutes. In this case, the area where multiple reflection points appear three or more times every 15 minutes is determined as a mask area. The third determination unit 423 calculates the occurrence rate of multiple reflection points for each cell. The method for calculating the occurrence rate is the same as the method for calculating the occurrence rate of multiple reflection points by the first determination unit 223 in the second embodiment.

[0150] The third determination unit 423 calculates the occurrence rate of multiple reflection points for all cells and identifies cells in which the occurrence rate of multiple reflection points exceeds the fifth reference value. In the example in Figure 12, it is assumed that the occurrence rate of multiple reflection points exceeds the fifth reference value in each of cells CE1, CE2, CE3, CE4, CE5, and CE6, while the occurrence rate of multiple reflection points does not exceed the fifth reference value in the other cells.

[0151] The third determination unit 423 determines which cells from among the multiple cells are to be excluded, which are cells that will not be used for object detection. In one example, the third determination unit 423 determines cells CE1, CE2, CE3, CE4, CE5, and CE6, in which the occurrence rate of multiple reflection points exceeds the fifth criterion value, as cells to be excluded.

[0152] The third decision unit 423 clusters the cells to be excluded. The clustering of the cells to be excluded is the same as the clustering of the cells to be excluded by the first decision unit 223 in the second embodiment. In the example in Figure 12, cluster CL1 is composed of cells CE1, CE2, CE3, CE4, CE5, and CE6.

[0153] The third determination unit 423 determines each cluster formed by clustering as a mask area. In the example in Figure 12, cluster CL1 is determined as the mask area. The third determination unit 423 is another example of the "clustering unit".

[0154] For example, the display control unit 224 causes the mask area determined by the third determination unit 423 to be displayed on the display device 212. In one example, the display control unit 224 causes the mask area in the sensor coordinate space to be displayed on the display device 212. The display control unit 224 may also superimpose the detection area 300 and the mask area on the display device 212.

[0155] Because the detection area 300 and the mask area are displayed simultaneously, the user can understand the positional relationship between each mask area and the detection area 300. For example, by comparing the positional relationship between each mask area and the detection area 300 with the positional relationship between each object in real space and the detection area 30 (or crosswalk 20), the user can recognize which object each mask area corresponds to.

[0156] The generation unit 226 generates setting information 111 which includes mask area information specifying the position, size, and shape of the mask area.

[0157] [4-2. Operation of the setting support device (setting support method)] Figure 16 is a flowchart showing an example of the setting support operation (setting support method) of an infrastructure radio wave sensor by the setting support device according to the fourth embodiment.

[0158] Steps S201 to S208 are the same as the processes described in steps S201 to S208 in the second embodiment, so their explanation will be omitted.

[0159] The processor 201 clusters the cells to be excluded and determines the formed clusters to be the mask area (step S401).

[0160] The processor 201 causes the display device 212 to display the detection area and the mask area (step S402).

[0161] The processor 201 generates setting information 111 specifying the position, size, and shape of each determined mask area (step S213). The processor 201 transmits the generated setting information 111 to the infrastructure radio wave sensor 10, thereby setting the mask area on the infrastructure radio wave sensor 10 (step S214). This completes the setting support operation.

[0162] [5. Fifth Embodiment] The configuration of the setting support device according to the fifth embodiment is the same as the configuration of the setting support device 200 according to the second embodiment, so the same reference numerals are used for the same components and their descriptions are omitted.

[0163] [5-1. Functions of the Setting Support Device] Figure 17 is a functional block diagram showing an example of the functions of the setting support device according to the fifth embodiment. When the processor 201 executes the setting support program 210, the setting support device 200 according to the fifth embodiment functions as a first acquisition unit 221, a determination unit 222, a first decision unit 223, a fourth decision unit 527, a display control unit 224, a second decision unit 225, and a generation unit 226.

[0164] The first acquisition unit 221, determination unit 222, first decision unit 223, second decision unit 225, and generation unit 226 in the fifth embodiment are the same as those in the second embodiment, so their description is omitted.

[0165] The fourth determination unit 527 determines the type of object causing the multiple reflection points based on the position of the cluster formed in the first determination unit 223 within the detection area. In other words, the fourth determination unit 527 determines the type of object causing the multiple reflection points based on the position of the candidate area determined in the first determination unit 223 within the detection area.

[0166] Figure 18 is a diagram illustrating an example of determining the type of object. Figure 18 shows the detection area 300 in sensor coordinate space. To clarify the positional relationship between the detection area 300 and the object on the road, Figure 18 shows a view of the pedestrian crossing 20 from directly above superimposed on the detection area 300.

[0167] For example, sidewalks have fixed objects such as trees, guardrails, utility poles, traffic signals, and signs. Roadways have vehicles. Roadways have stop lines. When a traffic signal for vehicles is lit red, vehicles are stopped at the stop line. Median strips have fixed objects such as trees and guardrails. In the example in Figure 18, there are trees 63A and utility poles 63B on sidewalk 63a, and guardrails 64A on median strip 64. Vehicles 62C and 62D are stopped at stop line 62A on lane 62a.

[0168] In Figure 18, the symbols 400A, 400B, 400C, 400D, and 400E each represent a candidate area. In the example in Figure 18, candidate area 400A is an area containing multiple reflection points due to trees 63A, candidate area 400B is an area containing multiple reflection points due to utility poles 63B, candidate area 400C is an area containing multiple reflection points due to vehicles 62C, candidate area 400D is an area containing multiple reflection points due to vehicles 62D, and candidate area 400E is an area containing multiple reflection points due to guardrails 64A.

[0169] For example, the fourth determination unit 527 determines that the type of object causing the multiple reflection points in candidate area 400A, which overlaps with the waiting area 300_2B, is a "tree". That is, since the waiting area 300_2B is the area corresponding to the sidewalk 63a, the fourth determination unit 527 can determine that the type of object causing the multiple reflection points is a "tree," which is a fixed object present on the sidewalk.

[0170] For example, the fourth determination unit 527 determines that the type of object causing the multiple reflection points in candidate area 400B, which overlaps with the waiting area 300_2B, is a "utility pole." That is, since the waiting area 300_2B is the area corresponding to the sidewalk 63a, the fourth determination unit 527 can determine that the type of object causing the multiple reflection points is a "utility pole," which is a fixed object on the sidewalk.

[0171] For example, the fourth determination unit 527 can determine the type of object corresponding to candidate area 400A as "trees" and the type of object corresponding to candidate area 400B as "utility poles" based on the positional fluctuations or speed of the reflection points in candidate areas 400A and 400B. That is, because the leaves and branches of trees sway in the wind, the position of the reflection points (including multiple reflection points) fluctuates rapidly, and a large speed is detected. Since utility poles do not move in the wind, the position of the reflection points (including multiple reflection points) hardly fluctuates over a long period of time, and the speed is hardly detected. Therefore, the fourth determination unit 527 can determine the type of object corresponding to candidate area 400A, where the positional fluctuations of the reflection points are large and the speed is high, as "trees," and determine the type of object corresponding to candidate area 400B, where the positional fluctuations of the reflection points are small and the speed is low, as "utility poles."

[0172] For example, the fourth determination unit 527 may determine the type of object causing the multiple reflections based on the shape and size of the candidate area. Specifically, for a candidate area with an elongated shape, the fourth determination unit 527 may determine the corresponding type of object to be a "guardrail".

[0173] For example, the fourth determination unit 527 determines that the type of object causing the multiple reflection points in candidate areas 400C and 400D that appear on the side of zebra area 300_1B near the inflow lane 62a is a "stop line". That is, since the side of zebra area 300_1B near the inflow lane 62a corresponds to the stop line 62A of lane 62a, the fourth determination unit 527 can determine that the "stop line" present in the roadway is the type of object causing the multiple reflection points.

[0174] For example, the fourth determination unit 527 determines that the type of object causing the multiple reflection points in the candidate area 400E that overlaps with the median strip area 300_3 is a "guardrail". That is, since the median strip area 300_3 is the area corresponding to the median strip 64, the fourth determination unit 527 can determine that the type of object causing the multiple reflection points is a "guardrail," which is a fixed object present in the median strip.

[0175] Returning to Figure 17, the display control unit 224 causes the display device 212 to display the type of object determined by the fourth determination unit 527 for each cluster.

[0176] Figure 19 is a diagram illustrating an example of how to display the type of object. In the example in Figure 19, a mask area setting screen is shown in which candidate areas are placed in the sensor coordinate space. In the mask area setting screen shown in Figure 19, both the detection area 300 and the candidate areas 400A, 400B, 400C, 400D, and 400E are displayed.

[0177] In the mask area setting screen shown in Figure 19, text information indicating the type of object is displayed near each candidate area 400A, 400B, 400C, 400D, and 400E. Specifically, near candidate area 400A, text information 401A indicating the corresponding object type "tree" is displayed, and near candidate area 400B, text information 401B indicating the corresponding object type "utility pole" is displayed. Near candidate areas 400C and 400D, text information 401C and 401D indicating the corresponding object type "stop line" are displayed respectively, and near candidate area 400E, text information 401E indicating the corresponding object type "guardrail" is displayed. This allows the user to understand the type of object corresponding to each of the candidate areas 400A, 400B, 400C, 400D, and 400E. For example, after confirming the type of object, the user can select an area to be used as a mask area from candidate areas 400A, 400B, 400C, 400D, and 400E.

[0178] [5-2. Operation of the setting support device (setting support method)] Figure 20 is a flowchart showing an example of the setting support operation (setting support method) of an infrastructure radio wave sensor by the setting support device according to the fifth embodiment.

[0179] Steps S201 to S209 are the same as the processes described in steps S201 to S209 in the second embodiment, so their explanation will be omitted.

[0180] The processor 201 determines the type of object causing multiple reflections in each candidate area based on the location of each determined candidate area (step S501).

[0181] The processor 201 displays the detection area 300 along with character information for the candidate area and the type of object (step S502). The processor 201 then proceeds to step S211. Steps S211 to S214 are the same as the processes described in steps S211 to S214 in the second embodiment, so their description is omitted.

[0182] [6. Modified Examples] In the first embodiment described above, the determination unit 123 determined multiple reflection points to be excluded reflection points based on their positions in the detection area 300, and excluded from the reflection points used for object detection by the detection unit 124. However, the determination unit 123 is not limited to this. For example, the determination unit 123 may determine a reflection point to be excluded if the occurrence rate of multiple reflection points at the position of the reflection point identified by the identification unit 121 exceeds a third reference value. That is, the determination unit 123 calculates the occurrence rate of multiple reflection points for each cell in the same way as the calculation of multiple reflection points by the first determination unit 223 described in the second embodiment. For example, the determination unit 123 may determine cells in which the occurrence rate of multiple reflection points is greater than the third reference value to be excluded reflection points.

[0183] The embodiments disclosed herein are illustrative in all respects and are not restrictive. The scope of rights in this disclosure is indicated by the claims rather than the embodiments described above, and includes the meaning of equivalents of the claims and all modifications within that scope.

[0184] 10 Infrastructure radio wave sensor 14 Transmitting / receiving unit 15 Transmitting circuit 15a Transmitting antenna 16 Receiving circuit 16a Receiving antenna 17 Detection circuit 18 Housing 18a Transmitting / receiving surface 20 Pedestrian crossing 30, 300 Detection area 30_1A, 30_1B, 300_1A, 300_1B Zebra area 30_2A, 30_2B, 300_2A, 300_2B Standby area 30_3, 300_3 Median strip area 31O Point 31Y Projection center axis 31X Straight line 50 Structure 51 Pole 52 Arm 60 Roadway 61 Intersection 62a Inbound lane 62b Outbound lane 62A Stop line 62C, 62D Vehicle 63a, 63b Sidewalk 63A Tree 63B Utility pole 64 Median strip 64A Guardrail 101 Processor 102 Non-volatile memory 103 Volatile memory 107 Communication interface (communication I / F) 110 Control program 111 Setting information 121 Identification unit 122 Judgment unit 123 Decision unit 124 Detection unit 125 Tracking unit 126 Output unit 200 Setting support device 201 Processor 202 Non-volatile memory 203 Volatile memory 204 Input / Output interface (I / O) 205 Graphics controller 206 Communication interface (communication I / F) 210 Setting support program 211 Input device 212 Display device 213 Detection data 221 First acquisition unit 222 Judgment unit 223 First decision unit 224 Display control unit 225 Second decision unit 226 Generation unit 321 Second acquisition unit 400A, 400B, 400C, 400D, 400E Candidate area 401A, 401B, 401C, 401D, 401E Text information 423 Third decision unit 527 Fourth decision unit RP1, RP2 Reflection point D1, D2 Distance θ1, θ2 Azimuth angle CE1, CE2, CE3, CE4, CE5, CE6 Cell CL, CL1 Cluster

Claims

1. A radio wave sensor for detecting an object in a detection area that includes at least a portion of a road by irradiating the detection area with radio waves, comprising: a transmitting antenna for irradiating the detection area with radio waves; a receiving antenna for receiving reflected waves from the object of the radio waves irradiated from the transmitting antenna; a identifying unit for identifying a reflection point that reflects the radio waves based on the received reflected waves; a determination unit for determining whether the identified reflection point is a multiple reflection point, which is a reflection point due to multiple reflections; and a detection unit for detecting an object in the detection area based on the reflection point, wherein the determination unit determines whether the determination condition for the reflection point being a multiple reflection point is met, and if the determination condition is met, determines that the reflection point is a multiple reflection point.

2. The radio wave sensor according to claim 1, wherein the determination condition is that there exists a second reflection point between the radio wave sensor and the first reflection point whose reflection intensity is higher than a first reference value, and the determination unit determines that the first reflection point is the multiple reflection point when the determination condition is met.

3. The determination condition is that a second reflection point exists between the radio wave sensor and the first reflection point, and the size of the reflection point group composed of a plurality of reflection points including the second reflection point is greater than a second reference value, and the determination unit determines that the first reflection point is the multiple reflection point when the determination condition is met, the radio wave sensor according to claim 1.

4. The radio wave sensor according to any one of claims 1 to 3, further comprising a determination unit that determines the multiple reflection points to be excluded from the reflection points used for detecting the object by the detection unit, based on the positions of the multiple reflection points in the detection area.

5. The radio wave sensor according to claim 4, wherein the detection area includes a first area for detecting an object moving on a road and a second area for detecting an object waiting to move on a road, and the determination unit determines the multiple reflection points included in the first area as the reflection points to be excluded.

6. The radio wave sensor according to claim 5, wherein the determination unit does not determine the multiple reflection points included in the second area as the reflection points to be excluded.

7. The radio wave sensor according to claim 5 or 6, wherein the determination unit does not determine the multiple reflection point as the excluded reflection point if an object detected is within a specific distance range from the multiple reflection point included in the first area.

8. The radio wave sensor according to any one of claims 4 to 7, wherein the determination unit determines the reflection point to be the excluded reflection point if the occurrence rate of the multiple reflection points at the position of the reflection point identified by the identification unit exceeds a third reference value.

9. A radio wave sensor setting support method comprising: acquiring reflection point information indicating the position on the road of a reflection point that reflects radio waves emitted from a radio wave sensor toward the road; determining, based on the acquired reflection point information, whether the reflection point is a multiple reflection point that is a reflection point due to multiple reflections; and generating setting information for setting the radio wave sensor based on the determination result of the multiple reflection point, wherein in the determination step, it is determined whether the determination condition for the reflection point being a multiple reflection point is met, and if the determination condition is met, it is determined that the reflection point is a multiple reflection point.

10. A method for assisting the setting of a radio wave sensor, comprising: acquiring multiple reflection point information indicating the positions on the road of multiple reflection points resulting from multiple reflections of radio waves emitted from the radio wave sensor toward the road; and generating setting information for setting the radio wave sensor based on the multiple reflection point information.

11. A method for supporting the setting of a radio wave sensor according to claim 9 or 10, further comprising the steps of: determining candidate areas which are candidates for exclusion areas to be excluded from the detection target of the radio wave sensor based on the multiple reflection points in a coordinate space set for the radio wave sensor; displaying the determined candidate areas on a display device; determining the candidate areas displayed on the display device as the exclusion areas; and generating setting information in which the exclusion areas are specified.

12. A method for assisting the setting of a radio wave sensor according to claim 11, further comprising the step of determining an area in the coordinate space that includes a position where the occurrence rate of the multiple reflection points exceeds a fourth reference value as the candidate area.

13. A method for supporting the setting of a radio wave sensor according to claim 9 or 10, further comprising the steps of: determining an exclusion area to be excluded from the detection target of the radio wave sensor based on the multiple reflection points in a coordinate space set for the radio wave sensor; and generating setting information in which the exclusion area is specified.

14. A method for assisting the setting of a radio wave sensor according to claim 13, further comprising the step of determining an area in the coordinate space that includes a position where the occurrence rate of the multiple reflection points exceeds a fifth reference value as the exclusion area.

15. A method for supporting the setting of a radio wave sensor according to claim 13, further comprising the steps of: clustering a plurality of multiple reflection points in a coordinate space set for the radio wave sensor based on the positions of the plurality of multiple reflection points; and determining the exclusion area in the coordinate space based on the cluster of the multiple reflection points which is the result of the clustering.

16. A method for assisting the setting of a radio wave sensor according to claim 15, further comprising the step of determining the type of object causing the multiple reflection points based on the location of the cluster in a detection area that includes at least a portion of the road.

17. A method for assisting the setting of a radio wave sensor according to claim 16, further comprising the step of displaying the determined type of object on a display device for each cluster.

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