Measuring device and measuring method

Abstract

To provide a measuring device and a measuring method that can accurately measure the presence or absence of a metal object.SOLUTION: A measuring device includes a radio wave transmitter, a radio wave receiver, a heat map creator, and a controller. The radio wave transmitter transmits radio waves. The radio wave receiver receives radio waves. The heat map creator creates a heat map of the received power on the basis of the received power of the radio waves received by the radio wave receiver. The controller determines the presence or absence of a metal object on the basis of the presence or absence of a ghost image in the heat map.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a measurement device and a measurement method. [Background technology]

[0002] It is common to set up access points indoors to build wireless networks. However, radio wave interference indoors tends to be greater than outdoors. Therefore, if the access point is not installed in an appropriate location, it can be difficult to achieve stable wireless communication.

[0003] In recent years, radio wave propagation simulators have been proposed that simulate the state of radio wave propagation radiated from a radio wave source. By using such radio wave propagation simulators to identify radio wave interference sources, it is possible to determine the optimal installation locations of access points, etc.

[0004] To obtain accurate results using a radio wave propagation simulator, it is necessary to measure information about the space being simulated sufficiently. In particular, indoors, there is a lot of radio wave interference not only from visible areas but also from invisible areas, so it is important to be able to measure information about these invisible areas sufficiently in order to obtain accurate simulation results. Radio wave interference from such invisible areas is often caused by radio waves reflected from metal objects installed in invisible places. Therefore, when measuring radio waves for radio wave propagation simulation, it is necessary to be able to accurately measure the presence or absence of metal objects, which greatly affect the state of radio waves. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3263191 Summary of the Invention [Problem to be solved by the invention]

[0006] The present disclosure provides a measurement device and a measurement method that can accurately measure the presence or absence of a metal object. [Means for solving the problem]

[0007] A measurement device according to one embodiment includes a radio wave transmitter, a radio wave receiver, a heat map creator, and a controller. The radio wave transmitter transmits radio waves. The radio wave receiver receives radio waves. The heat map creator creates a heat map of the received power based on the received power of the radio waves received by the radio wave receiver. The controller determines the presence or absence of a metal object based on the presence or absence of a ghost image in the heat map. [Effects of the Invention]

[0008] According to the present disclosure, a measurement device and a measurement method are provided that can accurately measure the presence or absence of a metal object. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a functional block diagram showing the configuration of a measurement device according to an embodiment. [Figure 2A] FIG. 2A is a diagram illustrating a hardware configuration of an example measurement device. [Figure 2B] FIG. 2B is a diagram showing the measurement device with the orientation of the antenna and measurement equipment changed. [Figure 3] FIG. 3 is a diagram illustrating a hardware configuration of an example control circuit. [Figure 4] FIG. 4 is a flowchart showing the operation of the measurement device. [Figure 5] FIG. 5 shows an example of an experimental setup for measuring the relationship between the material of an object and the distance to the object and the received strength of radio waves. [Figure 6A] FIG. 6A is a diagram showing the reception strength at each distance when radio waves are transmitted to a stainless steel plate. [Figure 6B] FIG. 6B is a diagram showing the reception strength at each distance when radio waves are transmitted to an aluminum plate. [Figure 6C]FIG. 6C is a diagram showing the reception strength at each distance when radio waves are transmitted to a plaster board. [Figure 6D] FIG. 6D is a diagram showing the reception strength at each distance when radio waves are transmitted to a concrete slab. [Figure 7] FIG. 7 is a diagram showing a comparison of heat maps based on the received intensity measured for each object using the experimental apparatus of FIG. [Figure 8] FIG. 8 is a diagram showing an example of an experimental setup for measuring the received strength of radio waves when a target object is placed behind an obstacle. [Figure 9] FIG. 9 is a diagram showing a heat map based on the received signal strength measured by the experimental apparatus of FIG. [Figure 10] FIG. 10 is a diagram showing a heat map based on the reception intensity when radio waves are transmitted with the millimeter-wave radar tilted at 10 degrees. [Figure 11] FIG. 11 is a flowchart showing the operation of the measurement device of the first modification. [Figure 12] FIG. 12 is a conceptual diagram of a machine learning model according to the second modification. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment will be described with reference to the drawings. FIG. 1 is a functional block diagram showing the configuration of a measurement device according to an embodiment. The measurement device 10 is a device that automatically measures information for radio wave propagation simulation while self-propelled indoors. The measurement device 10 measures information related to indoor 3D modeling as information for radio wave propagation simulation. The information related to indoor 3D modeling includes shape information of each point indoors. The shape information of each point is, for example, point cloud information representing the three-dimensional structure of each point. The point cloud information of each point may be, for example, information about the distance from the measurement point.

[0011] The measuring device 10 transmits radio waves and receives the reflected radio waves to acquire radio wave shape information about objects that act as obstacles to radio waves. Objects that act as obstacles to radio waves are objects that have the property of reflecting radio waves, such as metal objects. In other words, the radio wave shape information does not include shape information about objects that do not act as obstacles to radio waves, i.e., objects that are transparent to radio waves, such as wood.

[0012] Furthermore, the measuring device 10 in the embodiment can also acquire visible light shape information about an object that can be seen by the human eye by projecting and receiving infrared light.

[0013] Furthermore, the measuring device 10 measures information related to indoor radio wave propagation. The information related to radio wave propagation includes, for example, information related to KPI (Key Performance Indicator) and information related to QoE (Quality of Experience). The information related to KPI includes received power (RSRP), received signal strength (RSSI), etc. The information related to QoE includes communication speed, delay, etc.

[0014] As shown in Figure 1, the measuring device 10 has a radio wave transmitting unit 11, a radio wave receiving unit 12, a radio wave propagation measuring unit 13, an imaging unit 14, a heat map creating unit 15, a rear-end collision detecting unit 16, a moving mechanism 17, a communication unit 18, and a control unit 19.

[0015] The radio wave transmitter 11 includes a transmission circuit and emits radio waves from an antenna. The transmission circuit includes, for example, an oscillator and a modulation circuit. The radio wave transmitter 11 according to the embodiment may include multiple transmission circuits corresponding to multiple frequency bands so as to be able to transmit radio waves in multiple frequency bands. For example, the radio wave transmitter 11 may include a 24 GHz band transmission circuit and a 79 GHz band transmission circuit so as to be able to transmit radio waves in the 24 GHz band, which is a frequency band close to the 28 GHz band, which is one of the frequency bands usable in local 5G communication, and the 79 GHz band, which is a higher frequency band than the 28 GHz band.

[0016] The radio wave receiving unit 12 includes a receiving circuit and receives radio waves via an antenna. The receiving circuit includes, for example, a demodulation circuit. The radio wave receiving unit 12 according to the embodiment may include multiple receiving circuits corresponding to multiple frequency bands so as to receive radio waves in multiple frequency bands. For example, the radio wave receiving unit 12 may include a receiving circuit for the 24 GHz band and a receiving circuit for the 79 GHz band.

[0017] The radio wave propagation measurement unit 13 measures information related to KPIs as information on indoor radio wave propagation and information related to QoE. The radio wave propagation measurement unit 13 measures propagation loss (received power) and the like as KPIs using measurement equipment such as an area tester or a spectrum analyzer. The radio wave propagation measurement unit 13 also measures communication speed, delay, and the like as QoE using equipment such as a network tester or a wireless router. The radio wave propagation measurement unit 13 may include various measurement equipment according to the indices required as KPIs and QoE.

[0018] The imaging unit 14 captures an image of the object scene and generates an image of the object scene. The imaging unit 14 is, for example, a camera that captures an RGB color image. The imaging unit 14 may be an RGB-D camera that includes a light projecting and receiving unit for infrared light or the like and can also acquire point cloud information of the object by projecting and receiving infrared light.

[0019] The heat map creation unit 15 creates a heat map that graphically represents indoor radio wave intensity. Propagation loss may be used as the reception intensity. The heat map creation unit 15, for example, converts the reception intensity of radio waves received by the radio wave receiving unit 12 into pixel values ​​corresponding to the magnitude of the reception intensity value, and generates a two-dimensional heat map in which the pixel values ​​represent the reception intensity by arranging the pixel values ​​at positions corresponding to the distance from the measurement device 10 to an obstacle. The distance from the measurement device 10 to an obstacle may be calculated, for example, from the time difference between the transmission and reception of radio waves. The heat map creation unit 15 may also create a heat map by overlaying a heat map of radio wave intensity on a map of the indoor area. For example, the map may be created by setting the starting position of the movement of the measurement device 10 as the initial position and following the trajectory of the movement of the measurement device 10 from the initial position.

[0020] The rear-end collision detection unit 16 detects a rear-end collision of the measuring device 10 with an obstacle. The rear-end collision detection unit 16 includes, for example, an infrared light projector and receiver, and detects the distance to the obstacle by projecting and receiving infrared light. The rear-end collision detection unit 16 then detects a rear-end collision by determining whether the distance to the obstacle is equal to or less than a predetermined distance. When the rear-end collision detection unit 16 detects a rear-end collision, it notifies the control unit 19 of this.

[0021] The movement mechanism 17 includes a mechanism for self-propelling the measurement device 10 and a mechanism for adjusting the orientation of the antenna, etc. The mechanism for self-propelling the measurement device 10 may be a two-wheel drive mechanism, a four-wheel drive mechanism, a caterpillar mechanism, etc. The mechanism for adjusting the orientation of the antenna, etc. may be a lifting mechanism, a robot arm, etc.

[0022] The communication unit 18 includes a communication device and communicates with, for example, a server that performs radio wave propagation simulation via a network. The communication may be wireless or wired. The radio wave propagation simulation may be performed using any method. For example, radio wave propagation simulation using a ray tracing method may be used. In the ray tracing method, various types of radio wave propagation information such as received power and delay are calculated by searching for radio wave propagation paths taking into account reflection, transmission, and diffraction in a 3D-modeled space. For example, shape information measured by the measurement device 10 may be used for 3D modeling in the ray tracing method.

[0023] The control unit 19 controls the overall operation of the measurement device 10. Based on the radio waves received by the radio wave receiving unit 12, the control unit 19 acquires radio wave shape information of the location where the radio waves were transmitted by the radio wave transmitting unit 11. Based on the infrared light detected by the infrared light receiving unit of the imaging unit 14, the control unit 19 acquires visible light shape information of the location where the infrared light was projected. For example, distance as shape information can be calculated from the time difference between the transmission and reception of the radio waves and the time difference between the projection and reception of the infrared light. In addition, the control unit 19 sets the frequency of the radio waves transmitted by the radio wave transmitting unit 11. The control unit 19 also stores the information measured by the radio wave propagation measuring unit 13 and the image obtained by the imaging unit 14 in a storage device, correlating them with the position of the measurement device 10. The control unit 19 also determines whether or not a rear-end collision with an obstacle has occurred based on the detection result of the rear-end collision detection unit 16. If a rear-end collision with an obstacle has occurred, the control unit 19 controls the movement mechanism 17 to change the movement direction of the measurement device 10. Furthermore, in the embodiment, the control unit 19 performs processing to identify a metal object from the heat map created by the heat map creating unit 15.

[0024] 2A is a diagram showing the hardware configuration of an example measurement device 10. The measurement device 10 has a housing 101. The housing 101 is a metal box made of aluminum or the like, and is configured to prevent radio waves from radiating from the inside of the housing 101 to the outside and vice versa. The housing 101 is also provided with an infrared light projector / receiver 101a. This infrared light projector / receiver 101a can operate as a rear-end collision detector 16.

[0025] For example, four wheels 102 are attached to the underside of the housing 101. The wheels 102 function as a moving mechanism 17 and are driven by a motor (not shown). In addition, a sensor such as an encoder is attached to the wheels 102 to detect the rotation speed and direction of the wheels 102. The movement distance and movement direction of the measuring device 10 can be measured based on the rotation speed and direction of the wheels 102.

[0026] A control circuit 103 is housed inside the housing 101. The control circuit 103 is equipped with, for example, a processor and memory as a control unit 19, a communication device as a communication unit 18, and the like.

[0027] For example, two low dielectric struts 104 are provided on the top surface of the housing 101, and a bellows member 105 is provided between the low dielectric struts 104. The two low dielectric struts 104 and the bellows member 105 are attached to a low dielectric rail 106. An antenna 107 and a measuring instrument 108 are installed on the low dielectric rail 106.

[0028] The low-dielectric support pillar 104 is a support pillar made of a low-dielectric material. The low-dielectric support pillar 104 is configured so that its height can be adjusted by moving it up and down in the direction indicated by A in FIG. 2A using a motor (not shown). The bellows member 105 is a hollow bellows made of a low-dielectric material. The bellows member 105 is configured so that it can expand and contract as the low-dielectric support pillar 104 moves up and down. The low-dielectric rail 106 is a rail made of a low-dielectric material. An opening is formed in the attachment portion of the low-dielectric rail 106 to the bellows member 105. The low-dielectric rail 106 supports the antenna 107 and the measuring instrument 108 so that the antenna 107 and the measuring instrument 108 can be moved to any position on the low-dielectric rail 106 in the direction indicated by B in FIG. 2A. The movement of the antenna 107 and the measuring instrument 108 may be controlled by a motor or the like.

[0029] The antenna 107 is a directional antenna such as a horn antenna, and is used to transmit and receive radio waves. The antenna 107 is connected to a transmitting circuit and a receiving circuit (not shown). The measuring device 108 is a measuring device such as an area tester and a network tester serving as the radio wave propagation measuring unit 13, and a camera serving as the imaging unit 14. The transmitting circuit, the receiving circuit, and the measuring device 108 are connected to the control circuit 103 via a cable 109 attached to the bellows member 105. Here, an omnidirectional antenna such as an omni-directional antenna may be used as the antenna 107. An omnidirectional antenna can measure the power distribution over a wide area within the target space, allowing radio wave propagation simulation data to be measured in a short time. On the other hand, a directional antenna can also measure the direction of arrival of radio waves, allowing radio wave propagation simulation data to be measured with high accuracy.

[0030] In the measuring device 10 according to the embodiment, the orientations of the antenna 107 and the measuring device 108 can be changed as shown in Fig. 2B by adjusting the height of the low dielectric support pillar 104 and the positions of the antenna 107 and the measuring device 108 on the low dielectric rail 106. This allows the measuring device 10 to transmit and receive radio waves in various directions in space and to perform measurements in various directions.

[0031] 3 is a diagram showing the hardware configuration of an example of the control circuit 103. The control circuit 103 may be a computer having, as hardware, a processor 1031, a memory 1032, a storage 1033, an interface 1034, an input device 1035, a display device 1036, and a communication device 1037. The processor 1031, the memory 1032, the storage 1033, the interface 1034, the input device 1035, the display device 1036, and the communication device 1037 are connected to a bus 1038.

[0032] The processor 1031 is a processor that controls the overall operation of the measuring device 10. The processor 1031 operates as the heat map creation unit 15 and the control unit 19 by executing, for example, a measurement control program 1033a stored in the storage 1033. The processor 1031 is, for example, a CPU. The processor 1031 may be an MPU, a GPU, an ASIC, an FPGA, or the like. The processor 1031 may be a single CPU or the like, or may be multiple CPUs or the like.

[0033] The memory 1032 includes a ROM and a RAM. The ROM is a non-volatile memory. The ROM stores the operating system (OS), setting values, etc. of the measuring device 10. The RAM is a volatile memory. The RAM is used as a working memory during processing in the processor 1031, for example.

[0034] The storage 1033 is a storage such as a flash memory, for example, and stores various programs, such as a measurement control program 1033a, that are executed by the processor 1031. The storage 1033 can also store measurement results.

[0035] The interface 1034 is an interface for transmitting and receiving signals between the light emitting and receiving unit 101 a, the wheels 102, the antenna 107, and the measuring instrument 108.

[0036] The input device 1035 is an input device such as a touch panel or buttons. When the input device 1035 is operated, a signal corresponding to the operation is input to the processor 1031 via the bus 1038. The processor 1031 performs various processes in response to this signal. The input device 1035 can be used to set a frequency, etc.

[0037] The display device 1036 is a display device such as a liquid crystal display, an organic EL display, an LED, etc. The display device 1036 displays various types of information.

[0038] The communication device 1037 is a communication device for the measuring device 10 to communicate with a server etc. The communication device 1037 is, for example, a communication device for wireless communication, but may also be a communication device for wired communication.

[0039] Next, a description will be given of the operation of the measuring device 10. Fig. 4 is a flowchart showing the operation of the measuring device 10. The operation of Fig. 4 can be controlled by the processor 1031 of the measuring device 10.

[0040] In step S1, the processor 1031 sets the frequency of the transmission radio wave. For example, the processor 1031 sets the frequency band of the transmission radio wave to, for example, the 79 GHz band. The frequency of the transmission radio wave may be fixed. In this case, the processing of step S1 may be omitted.

[0041] In step S2, the processor 1031 controls the driving of the wheels 102 to start moving. The processor 1031 also starts creating a map. The map is created according to the trajectory of movement from the initial position, with the point where the movement started as the initial position.

[0042] In step S3, processor 1031 determines whether movement of a predetermined distance, for example, 1 meter, has been completed. The movement distance can be measured, for example, by the rotational speed of wheel 102. If it is determined in step S3 that movement of the predetermined distance has been completed, the process proceeds to step S4. If it is determined in step S3 that movement of the predetermined distance has not been completed, the process proceeds to step S8.

[0043] In step S4, processor 1031 determines whether measurement at the current measurement point is complete. In step S4, when measurement in all pre-set directions is complete, it is determined that measurement at the current measurement point is complete. All directions are, for example, 0 degree direction ±10 degree direction. The 0 degree direction is the front of measurement device 10. If it is determined in step S4 that measurement at the current measurement point is not complete, processing proceeds to step S5. If it is determined in step S4 that measurement at the current measurement point is complete, processing proceeds to step S10.

[0044] In step S5, the processor 1031 controls the height of the low dielectric support pillar 104 and the positions of the antenna 107 and the measuring instrument 108 on the low dielectric rail 106 to set the measurement orientation of the antenna 107 and the measuring instrument 108. For example, in the first measurement, the processor 1031 sets the measurement orientation of the antenna 107 and the measuring instrument 108 to a 0 degree orientation. In the second measurement, the processor 1031 sets the measurement orientation of the antenna 107 and the measuring instrument 108 to, for example, a 10 degree orientation. In the third measurement, the processor 1031 sets the measurement orientation of the antenna 107 and the measuring instrument 108 to, for example, a -10 degree orientation. The intervals and ranges of the measurement orientations are not limited to those exemplified here.

[0045] In step S6, the processor 1031 starts measurement. Specifically, the processor 1031 controls the transmission circuit to transmit radio waves of the frequency set in step S1 from the antenna 107, and receives the reflected radio waves from the reception circuit. The processor 1031 then calculates radio wave shape information from the results of the radio wave transmission and reception. For example, if the shape information is distance, the distance can be calculated from the time difference between the transmission and reception of the radio waves. The processor 1031 also captures an image of the subject scene using a camera as the measuring device 108, and calculates visible light shape information from the results of receiving infrared light. Furthermore, the processor 1031 measures propagation loss and the like using an area tester as the measuring device 108, and measures delay and the like using a network tester.

[0046] In step S7, the processor 1031 associates the measured radio wave shape information, visible light shape information, and radio wave propagation information with the coordinates on the map and the measurement direction, and stores them in, for example, the storage 1033. After that, the process returns to step S4.

[0047] In step S8, if it is determined in step S3 that movement of the predetermined distance has not been completed, processor 1031 determines whether a rear-end collision has been detected based on the result of light reception by infrared light projecting and receiving unit 101a. If it is determined in step S8 that a rear-end collision has been detected, the process proceeds to step S9. If it is determined in step S8 that a rear-end collision has not been detected, the process returns to step S3.

[0048] In step S9, the processor 1031 controls the driving of the wheels 102 to change the moving direction. Then, the process returns to step S3. The processor 1031 may determine the moving direction to be, for example, a random direction excluding the current moving direction in which a rear-end collision may occur. Alternatively, the processor 1031 may change the moving direction so as to preferentially move to a point for which a map has not yet been created.

[0049] In step S10, if it is determined in step S4 that measurement at the current measurement point has been completed, the processor 1031 determines whether the measurement has been completed. For example, if map creation has been completed and measurements at required measurement points on the map have been completed, the measurement is determined to be completed. If it is determined in step S10 that measurement has not been completed, the process returns to step S3. In this case, the processor 1031 may change the movement direction so as to preferentially move to a point for which a map has not yet been created. If it is determined in step S10 that measurement has been completed, the process proceeds to step S11.

[0050] In step S11, the processor 1031 creates a heat map of the radio wave intensity in the space measured from the propagation loss (reception intensity) measured as radio wave propagation information.

[0051] In step S12, the processor 1031 measures the presence, position, and shape of a metal object in the space from the heat map. The method for measuring a metal object will be described in detail later. After the metal object detection process, the process proceeds to step S13.

[0052] In step S13, the processor 1031 creates a file including information associating the measured radio wave shape information, visible light shape information, and radio wave propagation information with coordinates on a map, and a heat map. Then, the processor 1031 transmits the data of the created file to the server 20 using the communication device 1037. Thereafter, the processing of FIG. 4 ends.

[0053] Next, we will explain a method for detecting metal objects from a heat map of radio wave intensity. Figure 5 shows an example of an experimental device for measuring the relationship between the material and distance of an object and the received radio wave intensity.

[0054] In the experiment, a millimeter-wave radar R was installed in the experimental space. The millimeter-wave radar R used in the experiment was configured to transmit and receive radio waves in the 79 GHz band and measure the received signal strength (RSSI) of radio waves in the space.

[0055] Furthermore, in the experiment, an object O was placed at 0 degrees azimuth, which is the front direction of the millimeter-wave radar R, as indicated by arrow D. Metallic objects such as stainless steel and aluminum plates, and non-metallic objects such as gypsum and concrete plates were used as the objects O. The stainless steel plate was a flat plate measuring 500 mm horizontally, 500 mm vertically, and less than 1 mm thick. The aluminum plate was a flat plate measuring 900 mm horizontally, 450 mm vertically, and 3 mm thick. The gypsum plate was a flat plate measuring 300 mm horizontally, 210 mm vertically, and 15 mm thick. The concrete plate was a flat plate measuring 300 mm horizontally, 350 mm vertically, and 60 mm thick. In the experiment, the distance between the millimeter-wave radar R and the object O was adjusted to 0.5 m, 1.0 m, 2.0 m, 3.0 m, and 4.0 m, and radio waves W were transmitted in the direction directly in front of the millimeter-wave radar R. The millimeter-wave radar R then received the radio waves reflected from the object O, and the received power of the reflected radio waves was measured.

[0056] Figures 6A, 6B, 6C, and 6D show the reception strength at each distance when radio waves are transmitted to a stainless steel plate, an aluminum plate, a gypsum plate, and a concrete plate, respectively. The unit of reception strength is decibels (dB).

[0057] As shown in Figures 6A and 6B, the reception strength generally tends to decrease as the distance between the millimeter-wave radar R and the target object O increases. This is because radio wave reflection from a distance tends to increase radio wave attenuation. Furthermore, when comparing metal bodies, i.e., a stainless steel plate and an aluminum plate, and when comparing non-metal bodies, i.e., a gypsum plate and a concrete plate, there is no significant difference in reception strength at each distance, even if there is a difference in thickness. On the other hand, when comparing metal bodies and non-metal bodies, the reception strength for metal bodies is greater than the reception strength for non-metal bodies at all distances. This indicates that metal bodies are more likely to reflect radio waves than non-metal bodies.

[0058] As described above, there is a large difference in reception strength between when radio waves are transmitted to a metal object and when they are transmitted to a non-metal object. Therefore, the presence or absence of a metal object in space can be determined simply from the reception strength. For example, a threshold value for reception strength is set according to the distance from the measuring device 10, and if the reception strength is greater than the threshold value, it can be determined that a metal object is present within that distance.

[0059] Figure 7 is a comparison of heat maps based on the reception strength measured for each object using the experimental equipment in Figure 5. Figure 7 shows heat maps of reception strength when a stainless steel plate, an aluminum plate, a plaster plate, and a concrete plate are placed at distances of 0.5 m, 1.0 m, and 3.0 m, respectively.

[0060] As shown in Figure 7, for each of the stainless steel plate, aluminum plate, gypsum plate, and concrete plate, a real image I appears at the distance where the object is placed. This is because radio waves are reflected at the position where each object is placed, causing a change in the received intensity in the millimeter-wave radar.

[0061] Here, in addition to real image I, ghost image G appears on the stainless steel plate and aluminum plate. This is because the millimeter-wave radar also receives radio waves resulting from multipath caused by multiple reflections of radio waves between the millimeter-wave radar and the metal object. As shown in Figure 7, the closer the distance between the millimeter-wave radar and the metal object, the more ghost images appear. This indicates that the closer the distance, the more multiple reflections occur. On the other hand, ghost image G hardly appears on the gypsum plate and concrete plate. This indicates that almost no multiple reflections of radio waves occur between the millimeter-wave radar and non-metallic objects.

[0062] As described above, there is a significant difference between metallic and non-metallic objects in the presence or absence of ghost images in the heat map of reception intensity when radio waves are transmitted from the millimeter-wave radar R toward the target O. Therefore, the presence or absence of a metallic object can be determined from the presence or absence of ghost images.

[0063] FIG. 8 is a diagram showing an example of an experimental setup for measuring the received strength of radio waves when a target object is placed behind an obstacle.

[0064] In the experiment, a millimeter-wave radar R was installed in the experimental space. The millimeter-wave radar used in the experiment was configured to transmit and receive radio waves in the 79 GHz band and measure the received signal strength indicator (RSSI).

[0065] Furthermore, in the experiment, objects O1 and O2 were placed at an azimuth of 0 degrees, which is the front direction of the millimeter-wave radar R, as indicated by arrows D1 and D2. Object O1 was a stainless steel plate that served as the object of measurement for the millimeter-wave radar R. The stainless steel plate was a flat plate that was 500 mm horizontally, 500 mm vertically, and 1 mm thick or less. Object O2 was a plaster board that served as an obstacle and was placed closer to the millimeter-wave radar R than object O1. The plaster board was a flat plate that was 300 mm horizontally, 210 mm vertically, and 15 mm thick. In the experiment, the distance D2 between the millimeter-wave radar R and the object O2 was adjusted to 0.3 m, and the distance D1 between the object O2 and the object O1 was adjusted to 0.7 m, i.e., the distance D between the millimeter-wave radar R and the object O was adjusted to 1.0 m. Then, radio waves W were transmitted in the direction directly in front of the millimeter-wave radar R, and the millimeter-wave radar R received the radio waves reflected from the objects O1 and O2, and the received power of the reflected radio waves was measured.

[0066] Fig. 9 is a diagram showing a heat map based on the received signal strength measured by the experimental apparatus of Fig. 8. In Fig. 9, the heat map is shown with the top side being the 0 degree azimuth.

[0067] As shown in Figure 9, even when a plaster plate is placed in front of the stainless steel plate, real images appear at the positions where each object is placed. Specifically, real image I2 appears at a position 0.3 m from the 0-degree azimuth, where the plaster plate is placed, and real image I1 appears at a position 1.0 m from the 0-degree azimuth, where the stainless steel plate is placed. This means that even if a plaster plate is placed in front of the stainless steel plate, radio waves can penetrate the plaster plate and reach the stainless steel plate. Since the walls of houses and other buildings are often made of plaster or similar material, it can be seen that objects that may obstruct radio waves, such as metal ducts located deep inside the wall, can be measured by transmitting and receiving radio waves.

[0068] Furthermore, as mentioned above, when radio waves are transmitted to a target, ghost images appear due to multipath propagation caused by multiple reflections. Furthermore, the appearance of these ghost images differs depending on whether the target is a metal or non-metallic object. Figure 9 shows ghost images G1, G2, G3, and G4. Ghost images G1 and G2 are ghost images caused by reflections from a plasterboard. On the other hand, ghost images G3 and G4 are ghost images caused by reflections from a stainless steel plate. Even if a plasterboard is placed in front of the stainless steel plate, ghost images caused by reflections from the stainless steel plate also appear in the heat map. Therefore, the appearance of ghost images indicates that objects that may obstruct radio waves, such as metal ducts located deep inside a wall, can be measured. Note that even plasterboard can produce ghost images when the millimeter-wave radar R is close. However, as mentioned above, there is a significant difference in reception intensity between radio waves transmitted to a metal object and those transmitted to a non-metallic object. Therefore, the density of ghost images caused by reflections from non-metallic objects is lower than that of ghost images caused by reflections from metallic objects.

[0069] Fig. 10 is a diagram showing a heat map based on the reception intensity when radio waves are transmitted with the millimeter-wave radar R tilted at 10 degrees. In Fig. 10, the heat map is also shown with the top side being the 0 degree azimuth. Therefore, the front direction of the millimeter-wave radar R is a direction tilted at 10 degrees from the top direction in Fig. 10.

[0070] As shown in Figure 10, real images appear at the positions where each object is placed, even when the direction of the millimeter-wave radar R is changed. Specifically, real image I2 appears at a position 0.3 m away, which is the distance where the plaster board is placed, and real image I1 appears at a position 1.0 m away, which is the distance where the stainless steel plate is placed.

[0071] On the other hand, changing the direction of the millimeter-wave radar R changes the reflection conditions of radio waves from each object, and therefore the ghost images that appear in the heat map also change. In the example of FIG. 10, ghost images G1, G2, and G4 have almost completely disappeared, and ghost image G3 remains. Ghost image G3 is a ghost image caused by reflection from a stainless steel plate. In this way, by creating multiple heat maps by changing the direction of the millimeter-wave radar R and identifying images whose positions have not changed between the heat maps for each direction, the real images in the heat map can be identified. By identifying the real images, the position and shape of each object can be identified with high accuracy. The change in image position can be calculated from the difference in each position between the heat maps.

[0072] Furthermore, by comparing the reception strength of the real image and the ghost image surrounding the real image with the threshold value according to the distance described above, it is possible to more accurately determine whether the real image and ghost image are caused by a metal object or a non-metal object.

[0073] As described above, according to the embodiment, the measurement device transmits millimeter-wave radio waves to an object, receives the radio waves reflected from the object, and creates a heat map of reception intensity based on the reception intensity. The measurement device then determines whether the object is a metal or non-metallic object based on the presence or absence of ghost images in the heat map. Thus, according to the embodiment, the presence or absence of a metal object in a space can be determined with a simple configuration. Furthermore, by considering the reception intensity values ​​of the real image and ghost images surrounding the real image in addition to the presence or absence of a real image and ghost images, it is also possible to identify metal and non-metallic objects in a space.

[0074] According to an embodiment, the measurement device transmits radio waves in multiple directions at each measurement point, creates heat maps of the area around the object in multiple directions, and identifies the real image of the object from changes in ghost images between the created heat maps in multiple directions. As a result, according to an embodiment, the position and shape of the object in space can be identified with a simple configuration.

[0075] In this way, the measurement device according to the embodiment can acquire radio wave shape information, which is shape information of objects that act as obstacles to radio waves. By performing a radio wave propagation simulation using the radio wave shape information, it is expected that the accuracy of the radio wave propagation simulation will be improved. In other words, according to the embodiment, the measurement device can acquire necessary and sufficient information that is useful for improving the accuracy of the radio wave propagation simulation. Here, radio signals in high-frequency bands such as the millimeter wave band and the terahertz band tend to propagate in a straight line and are easily affected by obstacles. Therefore, the technology of the embodiment is particularly suitable for improving the accuracy of radio wave propagation simulations for radio signals in high-frequency bands. Good too.

[0076] In the embodiment, the creation of the heat map and the identification of the presence, position, and shape of a metal body are all performed by the measurement device 10. However, the creation of the heat map and the identification of the presence, position, and shape of a metal body may also be performed by, for example, a server that performs a radio wave propagation simulation.

[0077] (Variation 1) Modifications of the embodiment are described below. In the embodiment, the measurement device initially sets a frequency and then transmits radio waves in that frequency band. Here, when measuring millimeter-wave radio waves, because 24 GHz radio waves are close to the frequency band of radio waves used for communication, measurement can be performed under radio wave conditions similar to those during actual communication. Furthermore, because 24 GHz radio waves have a longer wavelength than 79 GHz radio waves, they easily penetrate objects. This makes them suitable for measuring metal ducts located deep inside walls. However, because 24 GHz radio waves have a longer wavelength than 79 GHz radio waves, the resolution of the image obtained in the heat map tends to be lower. In contrast, when measuring using 79 GHz radio waves, although the frequency band is different from the radio waves used for communication, the resolution of the image obtained in the heat map tends to be higher. For this reason, radio waves in both the 24 GHz band and the 79 GHz band may be used for measurement, rather than using only one frequency band.

[0078] 11 is a flowchart showing the operation of the measurement apparatus 10 of Modification 1. The operation of FIG. 11 is performed in place of, for example, step S1 of FIG.

[0079] In step S101, the processor 1031 sets the frequency of the transmission radio waves to the 24 GHz band, which is a frequency band closer to the actual communication conditions, and performs measurement at an arbitrary measurement point. The processor 1031 then determines whether sufficient shape information in space has been acquired from the radio wave shape information and the heat map. For example, if point cloud information with sufficient density has been acquired or if an image with sufficient resolution has been acquired in the heat map, it is determined that sufficient shape information has been acquired. If it is determined in step S101 that sufficient shape information has been acquired, the processing of FIG. 11 ends. Then, the processing proceeds to step S2 of FIG. 4. Thereafter, measurement continues using radio waves in the 24 GHz band. If it is determined in step S101 that sufficient shape information has not been acquired, the processing proceeds to step S102.

[0080] In step S102, the processor 1031 changes the frequency of the transmission radio wave to the 79 GHz band. Then, the processing in Fig. 11 ends. Then, the processing proceeds to step S2 in Fig. 4. After this, measurement continues using radio waves in the 79 GHz band.

[0081] As described above, in Modification 1, if sufficient shape information can be obtained in the 24 GHz band, measurement continues in the 24 GHz band, and if sufficient shape information cannot be obtained in the 24 GHz band, measurement is continued by switching to the 79 GHz band. This allows measurements to take advantage of the advantages of both the 24 GHz band and the 79 GHz band.

[0082] Here, in one example, the process of Fig. 11 is performed in place of step S1 of Fig. 4, but this is not limiting. For example, the process of Fig. 11 may be performed each time a measurement is made at each measurement point.

[0083] 11, the frequency bands of the transmitted radio waves are the 24 GHz band and the 79 GHz band. However, the frequency bands of the transmitted radio waves are not limited to the 24 GHz band and the 79 GHz band. Switching may be performed between three or more frequency bands, or one or both of the 24 GHz band and the 79 GHz band may be changed to another frequency band.

[0084] Alternatively, instead of switching between them, measurements may be performed using radio waves in the 24 GHz band and radio waves in the 79 GHz band at each measurement point. In this case, for example, if sufficient shape information is obtained from the 24 GHz band measurement results at each measurement point, the 24 GHz band measurement results may be adopted, and if sufficient shape information is not obtained, the 79 GHz band measurement results may be adopted. Furthermore, processing may be performed to calculate measurement results for a frequency band between two frequency bands or measurement results near two frequency bands by interpolation or extrapolation using the measurement results for the 24 GHz band and the 79 GHz band.

[0085] Furthermore, the measurement result calculation model is configured to add the measurement results for the 24 GHz band and the 79 GHz band at a predetermined ratio to output the measurement result for a frequency band between or around the 24 GHz band and the 79 GHz band. The measurement results for the 24 GHz band and the 79 GHz band are input as training data to the measurement result calculation model, and the measurement results for a desired frequency band are also provided as teaching data. The measurement result for the desired frequency band may be calculated from the measurement results for the 24 GHz band and the 79 GHz band using a machine learning model that learns the ratio value for obtaining the desired measurement result by backpropagation based on the difference between the calculated measurement result and the measurement data as teaching data.

[0086] (Variation 2) In the embodiment, a method of calculating the difference between heat maps in multiple directions is exemplified as a method of identifying real images of metallic objects and non-metallic objects from a heat map. However, the method of identifying real images of metallic objects and non-metallic objects is not limited to this. For example, real images of metallic objects and non-metallic objects may be identified from a heat map using a machine learning model.

[0087] FIG. 12 is a conceptual diagram of a machine learning model of Modification 2. In Modification 2, the machine learning model receives a heat map as input and outputs the positions of objects, such as metal objects and non-metal objects, in the heat map. An image recognition model such as a convolutional neural network (CNN) is used as a learning device for generating the machine learning model. This learning device extracts image features from the input heat map and estimates the position of the object from the extracted image features. By providing information on the position of the object in the heat map as training data, the learning device learns the relationship between the image features and the position of the object.

[0088] (Other variations) In the above-described embodiment, the measuring device 10 is a device that automatically measures information for radio wave propagation simulation while self-propelled indoors. However, the measuring device 10 does not necessarily have to be self-propelled indoors. In other words, the measuring device 10 may be fixed to a certain measurement point.

[0089] The present invention is not limited to the above-described embodiments, and various modifications can be made in the implementation stage without departing from the spirit of the invention. Furthermore, the embodiments may be implemented in appropriate combinations, in which case the combined effects can be obtained. Furthermore, the above-described embodiments include various inventions, and various inventions can be extracted by combining selected elements from the disclosed elements. For example, if the problem can be solved and the desired effect can be obtained even if some elements are deleted from all elements shown in the embodiments, the configuration from which these elements are deleted can be extracted as an invention. [Explanation of symbols]

[0090] 10 measuring device, 11 radio wave transmitting unit, 12 radio wave receiving unit, 13 radio wave propagation measuring unit, 14 imaging unit, 15 map creating unit, 16 rear-end collision detection unit, 17 moving mechanism, 18 communication unit, 19 control unit, 101 housing, 101a light emitting / receiving unit, 102 wheels, 103 control circuit, 104 low dielectric support, 105 bellows member, 106 low dielectric rail, 107 antenna, 108 measuring equipment, 109 cable, 1031 processor, 1032 memory, 1033 storage, 1034 interface, 1035 input device, 1036 display device, 1037 communication device, 1038 bus.

Claims

1. a radio wave transmitting unit that transmits radio waves; a radio wave receiving unit for receiving radio waves; a heat map creation unit that creates a heat map of the received power based on the received power of the radio waves received by the radio wave receiving unit; a control unit that determines the presence or absence of a metal object based on the presence or absence of a ghost image in the heat map; A measuring device comprising:

2. the radio wave transmitter transmits the radio waves in a plurality of directions; The control unit determines that an image whose position does not change in the heat maps created for each of the plurality of orientations is the image of the metal body. The measurement device according to claim 1 .

3. The control unit determines whether the real image and the ghost image are caused by the reflection of radio waves by a metal object or by the reflection of radio waves by a non-metal object based on the reception strength of each of the real image and the ghost image in the heat map. The measurement device according to claim 2 .

4. the control unit determines the position of the image of the metal body using a machine learning model created by providing the position of the image of the metal body in the heat map as teaching data to a learning device that estimates the position of the image of the metal body using the heat map as input. The measurement device according to claim 1 .

5. the radio wave transmitter is configured to be able to transmit the radio waves in two or more different frequency bands, The control unit determines a frequency band of the radio waves to be transmitted from the radio wave transmitting unit based on a resolution of the image in the heat map. The measurement device according to claim 1 .

6. The frequency band includes the 24 GHz band and the 79 GHz band. The measurement device according to claim 5 .

7. Further provided with a self-propelled mechanism for self-propelling indoors, The measuring device according to claim 1 , wherein the control unit discriminates an image of a metal object indoors.

8. Transmitting radio waves from a measurement device; receiving radio waves in the measuring device; creating a heat map of the received power based on the received power of the radio waves; determining whether or not a metal object is present based on whether or not a ghost image is present in the heat map; A measurement method comprising:

Images