Electromagnetic wave reflection device, electromagnetic wave reflection fence, and wireless transmission system

Abstract

To provide an electromagnetic wave reflecting device, an electromagnetic wave reflecting fence, and a radio transmission system capable of improving a radio wave propagation environment and securing the strength of the electromagnetic wave reflecting device.SOLUTION: The electromagnetic-wave reflecting device includes an electromagnetic-wave reflecting panel for reflecting electromagnetic waves in a predetermined band selected from 1MHz or more and 300GHz or less, and a frame for holding the electromagnetic-wave reflecting panel, and has strength adapted to a test based on a pendulum test of ISO14120.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] The present disclosure relates to an electromagnetic wave reflecting device, an electromagnetic wave reflecting fence, and a wireless transmission system. [Background technology]

[0002] Conventionally, there has been a wireless transmission system that includes a base station that transmits and receives radio waves in a desired band selected from a frequency band of 1 GHz to 300 GHz, and an electromagnetic wave reflection device that is arranged along at least a part of a manufacturing line where production equipment that transmits and receives the radio waves is arranged, and has a reflection surface that reflects the radio waves (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 199504 Summary of the Invention [Problem to be solved by the invention]

[0004] However, depending on the environment in which the wireless transmission system is installed, there may be cases where the location of the base station is limited and it is not possible to ensure a good positional relationship between the base station and the electromagnetic wave reflecting device. In such cases, it may be impossible to reduce the dead zone, and the radio wave propagation situation may not be improved sufficiently.

[0005] In addition, there may be cases where the electromagnetic wave reflecting device of the wireless transmission system is placed along the path of the autonomous mobile robot and reflects radio waves including the autonomous mobile robot's control signals. In such cases, the realization of cooperation between the autonomous mobile robot and humans and ensuring safety are prerequisites, so the electromagnetic wave reflecting device is required to have a certain degree of strength.

[0006] Therefore, an object of the present invention is to provide an electromagnetic wave reflecting device, an electromagnetic wave reflecting fence, and a wireless transmission system that can improve the radio wave propagation environment while ensuring the strength of the electromagnetic wave reflecting device. [Means for solving the problem]

[0007] An electromagnetic wave reflection device according to an embodiment of the present disclosure includes an electromagnetic wave reflection panel that reflects electromagnetic waves in a predetermined band selected from the range of 1 MHz to 300 GHz, and a frame that holds the electromagnetic wave reflection panel, and has strength that complies with tests conforming to the ISO 14120 pendulum test. [Effects of the Invention]

[0008] It is possible to provide an electromagnetic wave reflecting device, an electromagnetic wave reflecting fence, and a wireless transmission system that achieve both an improvement in the radio wave propagation environment and ensuring the strength of the electromagnetic wave reflecting device. [Brief explanation of the drawings]

[0009] [Figure 1A] 1 is a diagram showing an example of a passageway 35 in which a wireless transmission system 1 according to an embodiment is arranged. [Figure 1B] 1 is a diagram showing an example of the configuration of a leaky coaxial cable 80. FIG. [Figure 2] 1 is a diagram showing an example of the configuration of an electromagnetic wave reflecting fence 100A. [Figure 3] 1 is a diagram showing an example of a layer structure in the thickness direction of a reflective panel 10 having a specular reflective surface. [Figure 4] 1 is a diagram showing an example of a layer structure in the thickness direction of a reflective panel 10 having a non-specular reflective surface. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the electromagnetic wave reflecting device, the electromagnetic wave reflecting fence, and the wireless transmission system according to the present disclosure will be described. In the following, the same elements will be denoted by the same reference numerals, and duplicated descriptions may be omitted.

[0011] In the following description, an XYZ coordinate system is defined. The direction parallel to the X axis (X direction), the direction parallel to the Y axis (Y direction), and the direction parallel to the Z axis (Z direction) are perpendicular to one another. For ease of explanation, the -Z direction may be referred to as the lower side or bottom, and the +Z direction may be referred to as the upper side or top. A planar view refers to a view from the XY plane. In the following description, the length, width, thickness, etc. of each part may be exaggerated to make the configuration easier to understand. Terms such as parallel, right angle, orthogonal, horizontal, vertical, top and bottom, etc., are permitted to deviate to the extent that they do not impair the effects of the embodiments.

[0012] In this embodiment, an electromagnetic wave reflector and a leaky coaxial cable are used to reduce blind zones in a wireless transmission system used indoors and outdoors. In this specification, a "blind zone" refers to an area where the reception power is reduced by 10 dB or more due to the influence of an obstruction compared to the surrounding reception environment without obstructions. Generally, electromagnetic waves below 3 THz are called radio waves, but in this specification, communication waves transmitted from a base station are referred to as "radio waves," and electromagnetic waves in general are referred to as "electromagnetic waves."

[0013] Dead zones include not only two-dimensional areas but also three-dimensional space. When production equipment, sensors, or mobile communication terminals with wireless communication capabilities are located in a dead zone, it becomes difficult to send and receive signals between them and the base station. Therefore, electromagnetic wave reflecting devices can be introduced to reduce the dead zone and improve the radio wave environment.

[0014] <Embodiment> <Wireless Transmission System 1> FIG. 1A is a diagram showing an example of a parts storage area of ​​an assembly plant in which a wireless transmission system 1 of an embodiment is installed. FIG. 1B is a diagram showing an example of the configuration of a leaky coaxial cable 80. FIG. 2 is a diagram showing an example of the configuration of an electromagnetic wave reflecting fence 100A. In FIG. 1A, the wireless transmission system 1 is installed indoors. In FIG. 1A, as an example, multiple AMRs (Autonomous Mobile Robots) 31 are installed as equipment used in the parts storage area of ​​the assembly plant. The AMRs 31 communicate wirelessly with the wireless transmission system 1 and are capable of moving along an aisle 35 in the assembly plant. The aisle 35 is a passageway that the AMRs 31 can travel by communicating wirelessly with the wireless transmission system 1, and is the operating area of ​​the AMRs 31.

[0015] 1A, as an example, the electromagnetic wave reflecting devices 60 of the wireless transmission system 1 extend in the X direction on the -Y direction side and the +Y direction side. The center in the Y direction of the area sandwiched between the electromagnetic wave reflecting devices 60 on the -Y direction side and the +Y direction side is a parts storage area of ​​the assembly plant, where a plurality of containers 34 are arranged. As an example, the plurality of containers 34 are arranged along the X direction in two rows in the Y direction. Each container 34 contains parts of a product to be assembled at the assembly plant.

[0016] The passages 35 extend in the X direction along the containers 34, on the -Y and +Y sides of the multiple containers 34. An electromagnetic wave reflecting device 60 of the wireless transmission system 1 is provided on one of the sides of each passage 35 in the traveling direction (X direction). The electromagnetic wave reflecting device 60 separates the passage 35 for the AMR 31 from an area 36 exclusively for people. People can enter the passage 35, but the AMR 31 cannot enter the area 36. The reason why the electromagnetic wave reflecting device 60 separates the passage 35 from the area 36 will be described later.

[0017] Furthermore, the products assembled at the assembly plant may be any products that are assembled from multiple parts, such as semiconductor devices, electronic devices such as PCs (Personal Computers), smartphones, and tablet computers, or products other than electronic devices such as vehicles.

[0018] The Industrial IoT (Internet of Things) improves production efficiency and ensures safety at the site by connecting industrial devices, equipment, management systems, etc. used in assembly plants to a network. As an example, we will explain a configuration in which the wireless transmission system 1 is installed in an assembly plant and the AMR 31 and the assembly plant's equipment communicate wirelessly with the wireless transmission system 1. However, the wireless transmission system 1 can also be installed in outdoor facilities other than assembly plants, such as medical facilities, event venues, and railroad tracks, as well as indoor facilities such as plants, offices, and commercial facilities.

[0019] The wireless transmission system 1 performs wireless communication with the AMR 31 and the equipment in the assembly plant, but the following mainly describes the wireless communication between the wireless transmission system 1 and the AMR 31.

[0020] The wireless transmission system 1 includes a base station 33, an electromagnetic wave reflecting device 60, and a leaky coaxial cable 80. The base station 33, for example, performs wireless communication at a frequency included in the frequency band of 1 MHz to 300 GHz. The electromagnetic wave reflecting device 60, for example, has a reflective panel that reflects radio waves at the frequency of the base station 33. The leaky coaxial cable 80, for example, is connected to an antenna terminal of the base station 33 and is installed along the passage 35, and performs wireless communication at a frequency included in the frequency band of 1 MHz to 300 GHz.

[0021] Each AMR 31 is connected to the wireless communication network of the wireless transmission system 1 by wirelessly communicating with the base station 33 and the leaky coaxial cable 80. In addition, an electromagnetic wave reflecting device 60 may be interposed between the AMR 31 and the base station 33 and the leaky coaxial cable 80 in the wireless communication. That is, radio waves emitted from the base station 33 or the leaky coaxial cable 80 may be reflected by the electromagnetic wave reflecting device 60 and then received by the AMR 31. In addition, radio waves emitted from the AMR 31 may be reflected by the electromagnetic wave reflecting device 60 and then received by the base station 33 or the leaky coaxial cable 80.

[0022] To achieve wireless communication between the AMR 31 and the base station 33 and leaky coaxial cable 80, the base station 33, electromagnetic wave reflector 60, and leaky coaxial cable 80 provide a long wireless communication area in the horizontal direction. The technical specification (TS22.104) of 3GPP (3rd Generation Partnership Project) (registered trademark), a mobile communication standardization organization, specifies as a system requirement a wireless communication area with an aspect ratio of a rectangular area in a horizontal plane of 3 to 5 times. For example, the area size for a use case called "Motion Control" is specified as 50 m x 10 m x 10 m in length x width x height.

[0023] FIG. 1A illustrates a wireless environment in which an aisle 35 is used as a communication area, as an example of an indoor environment. In the coordinate system of FIG. 1A, the length (travel direction) of the aisle 35 is the X-direction, the width is the Y-direction, and the direction perpendicular to the floor is the Z-direction. A large number of containers 34 are transported along the aisle 35 by an AMR 31. While FIG. 1A illustrates a configuration in which the aisle 35 extends along the containers 34 in a parts storage area of ​​a factory, the location of the aisle 35 is not limited to the parts storage area. The aisle 35 may be any aisle along which an autonomously traveling vehicle such as the AMR 31 can travel, such as a product storage area at a logistics center or a baggage storage area at an airport. Furthermore, the autonomously traveling vehicle is not limited to the AMR 31 and may also be, for example, an automatic guided vehicle (AGV). The autonomously traveling vehicle, such as the AMR 31 or AGV, traveling along the aisle 35 has wireless communication capabilities, and large amounts of data are transmitted and received between the AMR 31, AGV, etc. and the control and management system via the wireless communication system 1.

[0024] In order to realize wireless communication between an autonomously traveling mobile body such as the AMR 31 and a network, a base station 33 and a leaky coaxial cable 80 are arranged along a passage 35. The leaky coaxial cable 80 is connected to the base station 33 and emits radio waves supplied from the base station 33. Here, a configuration will be described in which the base station 33 directly emits radio waves from its antenna and also supplies radio waves to the leaky coaxial cable 80, which then emits radio waves, but the base station 33 may also be configured to simply output radio waves to the leaky coaxial cable 80 and not emit radio waves.

[0025] The base station 33 and the leaky coaxial cable 80 transmit and receive signals or data to and from the AMR 31 at a predetermined frequency within a frequency band of, for example, 1 MHz to 300 GHz. Furthermore, to ensure that high-frequency radio waves, which have poor linearity, reach each AMR 31 from the base station 33 and the leaky coaxial cable 80 more reliably, regardless of the three-dimensional shape of the passage 35, the surrounding environment of the passage 35, or the presence of multiple AMRs 31, a plurality of electromagnetic wave reflecting devices 60 are arranged on one side of each passage 35 along the traveling direction of the AMR 31 in the passage 35. More specifically, a plurality of electromagnetic wave reflecting devices 60 are arranged on the −Y-direction side of the passage 35 located on the −Y-direction side of the container 34 along the traveling direction of the AMR 31 in the passage 35. Furthermore, a plurality of electromagnetic wave reflecting devices 60 are arranged on the +Y-direction side of the passage 35 located on the +Y-direction side of the container 34 along the traveling direction of the AMR 31 in the passage 35. It is also possible to connect a plurality of electromagnetic wave reflecting devices 60 and install them along the passage 35 as an electromagnetic wave reflecting fence.

[0026] In order to cover an area within a factory, including the passageway 35, with the wireless communication area provided by the base station 33, the electromagnetic wave reflecting device 60, and the leaky coaxial cable 80 and realize a network connection for the AMR 31, it is effective in terms of coverage to arrange the leaky coaxial cable 80 along the electromagnetic wave reflecting device 60. Also, in FIG. 1A , a container 34 is present beside the passageway 35, and two passageways 35 exist, one on the -Y direction side and the other on the +Y direction side of the container 34. However, in sections where no containers 34 exist, there is only one passageway 35, and it is effective in terms of coverage to arrange multiple electromagnetic wave reflecting devices 60 on both sides of the single passageway 35 along the direction of travel of the passageway 35 and to arrange the leaky coaxial cable 80 along the electromagnetic wave reflecting device 60.

[0027] That is, the electromagnetic wave reflecting device 60 may be provided on at least one side of the passage 35 along the traveling direction of the AMR 31 in the passage 35. "At least one side of the passage 35" means at least one of both sides of the passage 35. Furthermore, providing the electromagnetic wave reflecting device 60 on at least one side of the passage 35 along the traveling direction of the AMR 31 in the passage 35 means that there may be a section where the electromagnetic wave reflecting device 60 is discontinued (a section where the electromagnetic wave reflecting device 60 is not provided) on at least one side of the passage 35 in the traveling direction of the AMR 31.

[0028] The radio waves transmitted and received by the base station 33 and the leaky coaxial cable 80 are preferably, for example, radio waves in the 1 GHz to 300 GHz frequency band, which includes the Sub-6 frequency band and millimeter wave band of the fifth generation mobile communication system (5G). Currently, the Sub-6 frequency band and the 28 GHz band, which includes the millimeter wave band, are used, and the next-generation 6G mobile communication standard is expected to expand to the sub-terahertz band. By using such a high-frequency band, the communication bandwidth can be significantly expanded, enabling large-volume data communication with low latency.

[0029] Furthermore, the radio waves transmitted and received by the base station 33 and the leaky coaxial cable 80 may be Long Term Evolution (LTE), LTE-Advanced (LTE-A), Ultra Mobile Broadband (UMB), or Citizens Broadband Radio Service (CBRS). Furthermore, the radio waves transmitted and received by the base station 33 and the leaky coaxial cable 80 may be IEEE802.11 (Wi-Fi (registered trademark)), IEEE802.16 (WiMAX (registered trademark)), IEEE802.20, Ultra-Wideband (UWB), Bluetooth (registered trademark), Low Power Wide Area (LPWA), or the like.

[0030] <Strength that complies with the ISO14120 pendulum test for electromagnetic wave reflection device 60> Here, it will be explained that the electromagnetic wave reflecting device 60 has a strength that complies with a test based on the pendulum test of ISO14120.

[0031] ISO3691-4 is the international standard for the safe operation of AMR31. ISO3691-4 applies not only to AMR31 but also to autonomous robots such as AGVs and other automated guided vehicles or automated guided systems, but here we will focus on AMR31.

[0032] ISO3691-4 stipulates that a clearance of 0.5m wide and 2.1m high must be provided on both sides of the AMR31 aisle as a condition for ensuring safety, but depending on the layout of the factory, it may not be possible to ensure such clearance.In addition, even if the above clearance is provided, there may be cases where safety measures are required because the probability of AMR31 failure is not below the failure probability stipulated in ISO3691-4.

[0033] Furthermore, for the AMR31 to travel autonomously, it must communicate with a base station in real time to control its travel. However, 5G radio waves tend to travel in a straight line, and if there are structures such as pillars or walls in a factory, the radio waves are not diffracted, creating blind spots where the radio waves cannot reach. Furthermore, autonomous robots such as the AMR31 and AGVs often have low profiles, with an overall height of 500 mm (0.5 m) or less, and are located in height areas where radio waves from base stations have difficulty reaching them. Therefore, it is necessary to use an electromagnetic wave reflector 60 to improve the radio wave propagation environment and eliminate blind spots in low-height areas.

[0034] The electromagnetic wave reflecting device 60 is configured with a strength that complies with tests conforming to the ISO 14120 pendulum test to improve the radio wave propagation environment while ensuring safety in environments where the safety conditions of ISO 3691-4 cannot be met, and separates the AMR 31 passageway 35 from the area 36 reserved for people. This is to achieve cooperation between the AMR 31 and people and to ensure safety. The electromagnetic wave reflecting device 60 is configured with a strength that complies with tests conforming to the ISO 14120 pendulum test to ensure human safety in environments where the conditions cannot be met.

[0035] In addition, when an electromagnetic wave reflecting device 60 is installed within a factory in an area that satisfies the safety requirements of ISO3691-4, namely, providing a clearance of 0.5 m wide and 2.1 m high on both sides of the AMR31 passage, to improve the radio wave propagation environment, the electromagnetic wave reflecting device 60 does not need to have strength that complies with the pendulum test of ISO14120.

[0036] Furthermore, even if the above-described clearance is provided, if the failure probability of the AMR 31 is not equal to or less than the failure probability specified in ISO 3691-4, an electromagnetic wave reflecting device 60 having strength conforming to the ISO 14120 pendulum test may be provided to ensure safety. Furthermore, electromagnetic wave reflecting devices 60 having strength conforming to the ISO 14120 pendulum test may be provided in both areas where the ISO 3691-4 safety conditions cannot be met and areas where the ISO 3691-4 safety conditions can be met. This allows electromagnetic wave reflecting devices 60 with sufficient strength to be installed in areas where the ISO 3691-4 safety conditions can be met, as well as areas where the ISO 3691-4 safety conditions cannot be met, thereby enabling a higher level of safety measures to be implemented. Furthermore, the number of types of electromagnetic wave reflecting devices 60 delivered to a single factory can be reduced.

[0037] <Arrangement of the electromagnetic wave reflecting device 60 and the leaky coaxial cable 80> As described above, it is sufficient that the electromagnetic wave reflecting device 60 is provided on at least one side of the passage 35 along the traveling direction of the AMR 31 in the passage 35.

[0038] Moreover, as an example, the top (upper end) of the electromagnetic wave reflecting device 60 is installed at a position higher than the base station 33. The base station 33 preferably has a directional antenna that forms a beam toward the passage 35. Furthermore, the leaky coaxial cable 80, together with the electromagnetic wave reflecting device 60, is arranged on at least one side of the passage 35 along the traveling direction of the AMR 31 in the passage 35.

[0039] 1A, a leaky coaxial cable 80 is fixed to the electromagnetic wave reflecting device 60 on the +Y direction side. The leaky coaxial cable 80 can be fixed to the electromagnetic wave reflecting device 60 using a fixture 85 as shown in FIG. 2, for example. The height position of the electromagnetic wave reflecting device 60 on the +Y direction side is, for example, lower than the height position of the upper end of the electromagnetic wave reflecting device 60. Furthermore, the height position of the base station 33 connected to the leaky coaxial cable 80 on the +Y direction side is, for example, lower than the height position of the top (upper end) of the electromagnetic wave reflecting device 60 on the +Y direction side.

[0040] 1A, the leaky coaxial cable 80 on the -Y direction side is suspended from the ceiling by a stay 90. As an example, the height position of the leaky coaxial cable 80 on the -Y direction side is higher than the height position of the upper end of the electromagnetic wave reflection device 60 on the -Y direction side. As an example, the leaky coaxial cable 80 on the -Y direction side is located on the +Y direction side of the electromagnetic wave reflection device 60 on the -Y direction side in the Y direction. This is to propagate the reflected wave in the +Y direction and to suppress leakage of radio waves in the -Y direction side of the electromagnetic wave reflection device 60 on the -Y direction side.

[0041] Also, as an example, the height position of base station 33 connected to leaky coaxial cable 80 on the -Y direction side is higher than the height position of the top (upper end) of electromagnetic wave reflecting device 60. However, for example, by further lengthening stay 90 that suspends leaky coaxial cable 80 and lowering the position of a holder (not shown) that holds base station 33, the height positions of leaky coaxial cable 80 on the -Y direction side and base station 33 may be made lower than the height position of the top (upper end) of electromagnetic wave reflecting device 60. This is advantageous for irradiating a beam from the directional antenna of base station 33 toward passageway 35.

[0042] Compared to normal coaxial cables, leaky coaxial cables 80 have a lower degree of freedom in bending and winding. For this reason, it is not practical to route the leaky coaxial cable 80 while bending it along the floor or under the floor, for example. For this reason, it is advantageous in terms of routing to arrange the leaky coaxial cable 80 along an electromagnetic wave reflecting device 60 that is arranged linearly. Furthermore, if the leaky coaxial cable 80 is arranged at too high a position, it becomes difficult to obtain sufficient strength of the radio waves radiated downward. For this reason, it is advantageous from the perspective of building a wireless communication area to attach the leaky coaxial cable 80 to an electromagnetic wave reflecting device 60 that is 2 to 3 meters high or less.

[0043] The leaky coaxial cable 80 is arranged closer to the passage 35 than the electromagnetic wave reflecting device 60. That is, the leaky coaxial cable 80 is arranged in an area surrounded by the electromagnetic wave reflecting device 60 on the -Y direction side, the electromagnetic wave reflecting device 60 on the +Y direction side, and the road surface (floor surface) of the passage 35, and is connected to an antenna terminal of the base station 33. Also, the leaky coaxial cable 80 is provided in this area, for example, at a position lower than the top (upper end) of the electromagnetic wave reflecting device 60. Note that this also applies to a section where there is no container 34 and only one passage 35 is provided.

[0044] The area surrounded by the electromagnetic wave reflection device 60 on the -Y direction side, the electromagnetic wave reflection device 60 on the +Y direction side, and the road surface (floor surface) of the passage 35 includes, in the height direction, a position higher than the top (upper end) of the electromagnetic wave reflection device 60. The leaky coaxial cable 80 only needs to be arranged within this area, so it may be provided at a position higher than the top (upper end) of the electromagnetic wave reflection device 60.

[0045] Furthermore, the area surrounded by the electromagnetic wave reflecting device 60 on the −Y direction side, the electromagnetic wave reflecting device 60 on the +Y direction side, and the road surface (floor surface) of the passage 35 also includes the area directly above the electromagnetic wave reflecting device 60. That is, the leaky coaxial cable 80 may be located directly above the electromagnetic wave reflecting device 60. For example, the leaky coaxial cable 80 may be provided along the top (upper end) of the electromagnetic wave reflecting device 60, or may be located directly above the electromagnetic wave reflecting device 60 via a fixing member or the like attached to the top (upper end) of the electromagnetic wave reflecting device 60. The leaky coaxial cable 80 being located directly above the electromagnetic wave reflecting device 60 means that there is a portion where the leaky coaxial cable 80 and the electromagnetic wave reflecting device 60 overlap in the width direction of the passage 35 when viewed from directly above. Furthermore, when the leaky coaxial cable 80 is located directly above the electromagnetic wave reflecting device 60, it is preferable that the slot 83A faces toward the center of the passage 35 in the width direction. This is because the radio waves emitted from the slot 83A can be emitted toward the passage 35.

[0046] In addition to the directional antenna of the base station 33, an electromagnetic wave reflecting device 60 and a leaky coaxial cable 80 are placed beside the passage 35, so that the radio waves emitted from the base station 33 and the leaky coaxial cable 80 are efficiently concentrated on the passage 35 and radio waves leaking outside the passage 35 are suppressed.

[0047] Even if the beam shape is controlled by the base station 33, other AMRs 31 may obstruct the LOS (Line of Sight). In such cases, radio waves are emitted from a leaky coaxial cable 80 installed beside and along the passage 35, allowing them to reach the AMR 31. Furthermore, the radio waves emitted from the base station 33 and the leaky coaxial cable 80 can be reflected by an electromagnetic wave reflecting device 60 and delivered to the AMR 31.

[0048] The size of the reflecting surface of the electromagnetic wave reflecting device 60 should be large enough to cover at least the area determined by the radius R of the first Fresnel zone. The radius R of the first Fresnel zone when radio waves radiated from the antenna of the base station 33 and reflected by the electromagnetic wave reflecting device 60 reach the AMR 31 in phase is defined by the following equation.

[0049] R=[λd1d2 / (d1+d2)] 1 / 2 Here, λ is the wavelength used, d1 is the distance from the antenna of the base station 33 to the electromagnetic wave reflecting device 60, and d2 is the distance from the electromagnetic wave reflecting device 60 to the antenna of the AMR 31.

[0050] In the 28 GHz band (wavelength approximately 10.7 mm), if the distance d1 from the antenna of the base station 33 to the electromagnetic wave reflecting device 60 is 20.0 mm and the distance d2 from the electromagnetic wave reflecting device 60 to the AMR 31 is 10.0 m, then the size of the reflecting surface of the electromagnetic wave reflecting device 60 only needs to be several tens of centimeters on one side. On the other hand, from the perspective of forming an electromagnetic wave reflecting fence that covers a wide reflection area with a small number of electromagnetic wave reflecting devices 60, the width and length of the reflecting surface of the electromagnetic wave reflecting device 60 may be approximately 2.0 m x 4.0 m. In the embodiment, the electromagnetic wave reflecting device 60 is arranged along the passage 35 so that the received power behind the reflecting surface of the electromagnetic wave reflecting device 60, i.e., in the area outside the passage 35, is lower than the average or median of the received power along the passage 35.

[0051] <Configuration of leaky coaxial cable 80> 1B, the leaky coaxial cable 80 has an inner conductor 81, an insulating layer 82, an outer conductor 83, and an insulating coating 84. The inner conductor 81 is a core wire and is made of a metal such as copper or aluminum. The insulating layer 82 is made of an insulator such as foamed polyethylene, and covers the inner conductor 81 to insulate the inner conductor 81 from the outer conductor 83.

[0052] The outer conductor 83 is a cylindrical conductor provided along the outer surface of the insulating layer 82, and is produced, for example, by winding a tape made of metal such as copper or aluminum around the outer surface of the insulating layer 82. The outer conductor 83 has a plurality of slots 83A provided along the extension direction (X direction) of the leaky coaxial cable 80. While FIG. 1B shows a configuration in which linear slots 83A are arranged in a wave-like pattern along the extension direction of the leaky coaxial cable 80, the slots 83A are not limited to being linear and may have various shapes. Furthermore, the arrangement of the multiple slots is not limited to being wave-like. The insulating coating 84 covers the outer surface of the outer conductor 83, and is made, for example, of a heat-resistant and flame-retardant resin such as polyethylene.

[0053] When one end of the inner conductor 81 of such a leaky coaxial cable 80 is connected to a signal terminal (feed terminal) among the antenna terminals of the base station 33 and one end of the outer conductor 83 is connected to a ground terminal among the antenna terminals of the base station 33, when the base station 33 transmits radio waves, a signal is supplied from the antenna terminal of the base station 33 to the leaky coaxial cable 80, and the radio waves are transmitted from the slot 83A to the periphery of the leaky coaxial cable 80. When the base station 33 receives radio waves, the radio waves around the leaky coaxial cable 80 are received by the slot 83A, transmitted by the leaky coaxial cable 80, and reach the base station 33.

[0054] Therefore, by connecting the leaky coaxial cable 80 to the antenna terminal of the base station 33, a wireless communication area can be established around the leaky coaxial cable 80 along the passage 35. The leaky coaxial cable 80 functions as both a transmission path and an antenna.

[0055] <Attachment structure of the electromagnetic wave reflecting device 60, the electromagnetic wave reflecting fence 100A, and the leaky coaxial cable 80> As shown in Fig. 2, the electromagnetic wave reflective fence 100A is formed by connecting electromagnetic wave reflecting devices 60-1, 60-2, and 60-3 (hereinafter, sometimes collectively referred to as "electromagnetic wave reflecting devices 60"), each having reflective panels 10-1, 10-2, and 10-3 (hereinafter, sometimes collectively referred to as "reflective panels 10"), via a frame 50A. That is, the electromagnetic wave reflective fence 100A includes a plurality of electromagnetic wave reflecting devices 60. The configuration of each electromagnetic wave reflecting device 60 is the same as the configuration of each electromagnetic wave reflecting device 60 shown in Fig. 1A.

[0056] The coordinate system in Fig. 2 is consistent with the coordinate system in Fig. 1A, and the electromagnetic wave reflecting device 60 shown in Fig. 2 corresponds to the electromagnetic wave reflecting device 60 on the -Y direction side in Fig. 1A. The width or lateral direction of the reflective panel 10 is the X direction, the thickness direction is the Y direction, and the height direction is the Z direction. In Fig. 2, three electromagnetic wave reflecting devices 60 are connected to form the electromagnetic wave reflective fence 100A, but the number of multiple electromagnetic wave reflecting devices 60 to be connected is determined appropriately depending on the conditions of the passageway 35.

[0057] As an example, the electromagnetic wave reflective fence 100A shown in FIG. 2 has a reflective surface on the +Y direction side, and is arranged to the side (-Y direction side) of the passage 35 in the traveling direction (X direction). The leaky coaxial cable 80 is arranged on the reflective surface of the electromagnetic wave reflective fence 100A. Since the reflective surface of the electromagnetic wave reflective fence 100A arranged to the side (-Y direction side) of the traveling direction (X direction) of the passage 35 is located on the +Y direction side, the leaky coaxial cable 80 is arranged on the +Y direction side of the electromagnetic wave reflective fence 100A. In this way, by providing the leaky coaxial cable 80 on the reflective surface of the electromagnetic wave reflective fence 100A beside the passage 35, it is possible to establish a wireless communication area along the passage 35 even at a position away from the base station 33 in the traveling direction of the passage 35.

[0058] The reflective panel 10 used in the electromagnetic wave reflecting device 60 reflects electromagnetic waves in the range of 1 MHz to 300 GHz, preferably 1 GHz to 100 GHz, and more preferably 1 GHz to 80 GHz. The reflective panel 10 has a layer containing a conductive film as a reflective film. The conductive film has a predetermined conductive pattern designed according to the desired reflection angle, frequency band, etc. The conductive pattern may include a periodic pattern, a mesh pattern, a geometric pattern, etc., and may be formed from a transparent conductive film. The reflective panel 10 has a protective layer with ultraviolet protection function as its outermost layer.

[0059] The reflective surface of the reflective panel 10 may be a specular reflective surface in which the angle of incidence and the angle of reflection of the electromagnetic wave are equal in all of the multiple electromagnetic wave reflecting devices 60. Alternatively, the reflective surface of the reflective panel 10 may be a non-specular reflective surface in which the angle of incidence and the angle of reflection of the electromagnetic wave are different in all of the multiple electromagnetic wave reflecting devices 60. Alternatively, at least some of the multiple electromagnetic wave reflecting devices 60 (e.g., one or two of ten electromagnetic wave reflecting devices 60) may have non-specular reflective surfaces, and the remaining of the multiple electromagnetic wave reflecting devices 60 (e.g., nine or eight of ten electromagnetic wave reflecting devices 60) may have specular reflective surfaces. The number of at least some of the electromagnetic wave reflecting devices 60 may be any number as long as it is a portion of the total number. Alternatively, by overlapping an electromagnetic wave reflecting device 60 having a specular reflective surface with an electromagnetic wave reflecting device 60 having a non-specular reflective surface, non-specular reflection may be generated in that section. Furthermore, there may be an electromagnetic wave reflecting device 60 having a configuration in which, within the reflecting panel 10 of one electromagnetic wave reflecting device 60, at least a portion of the area has a non-specular reflecting surface, and the remaining area has a specular reflecting surface.

[0060] The conductive pattern serving as the reflective film of the specular reflective surface can be realized, for example, by a conductive film having a mesh pattern. The conductive film having a mesh pattern is transparent, so that the opposite side of the electromagnetic wave reflecting device 60 can be easily seen. Here, transparency means that the visual transmittance is at least 40% or more, preferably 60% or more, more preferably 70% or more, and even more preferably 80% or more.

[0061] Non-specular reflective surfaces include diffusive and scattering surfaces, as well as metasurfaces, which are artificial reflective surfaces designed to reflect radio waves in a desired direction. It may be desirable for the reflective panels 10-1, 10-2, and 10-3 to be electrically connected to each other in order to maintain the continuity of the reflected potential. However, if a metasurface is included, electrical connection between adjacent reflective panels 10 is not necessary. By holding adjacent reflective panels 10 together with a frame 50A, an electromagnetic wave reflective fence 100A connected in the X direction is obtained.

[0062] The electromagnetic wave reflecting device 60 includes the reflective panel 10 and the frame 50A, as well as legs 56 supporting the frame 50A. The electromagnetic wave reflecting device 60 and the electromagnetic wave reflecting fence 100A are supported on the road surface by the legs 56. The legs 56 may be configured to be fixed to the road surface with screws, bolts, or the like. In addition to the frame 50A, the electromagnetic wave reflecting device 60 also includes a top frame 57 that holds the upper end of the reflective panel 10 and a bottom frame 58 that holds the lower end. The frame 50A, the top frame 57, and the bottom frame 58 form a frame that holds the entire periphery of the reflective panel 10. The frame 50A may be referred to as a "side frame" based on its position relative to the top frame 57 and the bottom frame 58. The top frame 57 and the bottom frame 58 ensure mechanical strength and safety during transportation and assembly of the reflective panel 10. The top frame 57 may be configured to allow a separate member, such as another reflective panel or an electromagnetic wave absorbing panel, to be connected to the upper end of the reflective panel 10. This allows greater freedom in the size and function of the electromagnetic wave reflecting fence 100A.

[0063] Furthermore, as one example, the leaky coaxial cable 80 is fixed to the frame 50A by a fixture 85. The fixture 85 may be any member that can fix the leaky coaxial cable 80 to the electromagnetic wave reflecting fence 100A. As one example, the fixture 85 may be a member that has a mounting hole formed in the frame 50A, is inserted into the mounting hole while holding the leaky coaxial cable 80, and is fixed with a bolt or the like. Such a fixture 85 may be made of metal or resin.

[0064] As an example, the leaky coaxial cable 80 may be fixed to the electromagnetic wave reflecting fence 100A as follows. The height position of the leaky coaxial cable 80 from the floor surface may be equal to or lower than the height position of the upper ends of the plurality of electromagnetic wave reflecting devices 60 from the floor surface. By setting the height position of the leaky coaxial cable 80 from the floor surface equal to or lower than the height position of the upper ends of the plurality of electromagnetic wave reflecting devices 60 from the floor surface, the radio waves radiated from the slot 83A can be reflected by the electromagnetic wave reflecting devices 60 toward the passage 35, and leakage of the radio waves to the outside of the electromagnetic wave reflecting devices 60 can be suppressed. Note that the height position of the leaky coaxial cable 80 from the floor surface may be higher than the height position of the upper ends of the plurality of electromagnetic wave reflecting devices 60 from the floor surface.

[0065] Furthermore, the multiple slots 83A of the leaky coaxial cable 80 may face the center in the width direction of the passage 35. When the slots 83A face the center in the width direction of the passage 35, radio waves emitted from the slots 83A can more easily reach the AMR 31. Note that the multiple slots 83A of the leaky coaxial cable 80 may face in a direction other than the center in the width direction of the passage 35, but facing only upward is not preferable from the viewpoint of communication efficiency.

[0066] Furthermore, the distance D between the plurality of electromagnetic wave reflecting devices 60 and the leaky coaxial cable 80 may be 0.3 m or less. If the distance D is long, the strength of the reflected wave that is reflected by the electromagnetic wave reflecting device 60 from the leaky coaxial cable 80 and propagates toward the center of the passage 35 in the width direction will be low, so it is preferable that the leaky coaxial cable 80 is suitably close to the electromagnetic wave reflecting device 60.

[0067] Furthermore, the lower end of the reflective panel 10 of each electromagnetic wave reflecting device 60 is preferably located close to the floor to eliminate blind zones in areas close to the floor of the passageway 35 where AMRs 31 having a low profile may be present (for example, areas 500 mm or less above the floor). For example, the lower end of the reflective panel 10 is preferably 150 mm or less above the floor of the passageway 35, more preferably 100 mm or less above the floor of the passageway 35, and even more preferably 50 mm or less above the floor of the passageway 35.

[0068] Furthermore, the upper end of the reflective panel 10 of each electromagnetic wave reflecting device 60 is preferably located at a height of, for example, 2 m or more to ensure safety in the vertical direction even in an environment where a clearance of 0.5 m width cannot be secured on both sides of the passage 35 of the AMR 31. The positioning of the upper end of the reflective panel 10 of the electromagnetic wave reflecting device 60 at a height of 2 m or more means that the height of the electromagnetic wave reflecting device 60 is 2 m or more.

[0069] Furthermore, the distance between each electromagnetic wave reflecting device 60 and the passage 35 is preferably 0.1 m or more to ensure safety even in an environment where a clearance of 0.5 m wide cannot be secured on both sides of the passage 35 of the AMR 31. Furthermore, the distance between each electromagnetic wave reflecting device 60 and the passage 35 may be 50 m or less, taking into consideration that the electromagnetic waves reflected by the electromagnetic wave reflecting device 60 reach the AMR 31 with a sufficient signal level. In other words, the distance between the electromagnetic wave reflecting device 60 and the passage 35 may be 0.1 m to 50 m. Note that the distance between each electromagnetic wave reflecting device 60 and the passage 35 is the distance between each electromagnetic wave reflecting device 60 and the end of the passage 35 on the electromagnetic wave reflecting device 60 side.

[0070] <Layer structure of the reflective panel 10> FIG. 3 is a diagram showing an example of a layer structure in the thickness direction (Y direction) of a reflective panel 10 having a specular reflective surface. The layer structure shown in FIG. 3 is a layer structure in an XY cross section of the reflective panel 10, with the stacking direction being the thickness direction (Y direction) of the reflective panel 10. FIG. 3 also shows a cross section of the reflective panel 10 of an electromagnetic wave reflecting device 60 arranged on the -Y direction side of the passage 35, as an example, viewed from above (+Z direction). The reflective panel 10 having a specular reflective surface includes a conductive layer 11 and a dielectric layer 14 or 15 bonded to at least one surface of the conductive layer 11 via an adhesive layer 12 or 13. In the example of FIG. 3, the conductive layer 11 is sandwiched between the dielectric layers 14 and 15 via the adhesive layers 12 and 13.

[0071] The conductive layer 11 is a surface that forms the reflective surface of the reflective panel 10 having a specular reflective surface, and is made of a metal material suitable for specular reflection. A good conductor such as Cu, Ni, SUS, Ag, or Au can be used as the material for the conductive layer 11. The conductive layer 11 has a thickness of 10 μm or more and 200 μm or less, preferably 50 μm or more and 150 μm or less, so as to function sufficiently as a reflective surface that specularly reflects electromagnetic waves of a target frequency. For example, the conductive layer 11 may be realized as a conductive layer having a mesh pattern as described above, or may be a conductive layer that does not have a mesh pattern.

[0072] The adhesive layers 12 and 13 have a transmittance of 60% or more, preferably 70% or more, and more preferably 80% or more at the operating frequency so as to guide incident electromagnetic waves to the conductive layer 11. The adhesive layers 12 and 13 may be formed from vinyl acetate resin, acrylic resin, cellulose resin, aniline resin, ethylene resin, silicone resin, or other resin materials. To provide the adhesive layers 12 and 13 with durability, moisture resistance, weather resistance, and other properties sufficient for outdoor use, ethylene-vinyl acetate (EVA) copolymer or cycloolefin polymer (COP) may be used. The thickness of the adhesive layers 12 and 13 is such that the dielectric layers 14 and 15 are securely bonded to the conductive layer 11, e.g., 10 μm to 400 μm. The adhesive layers 12 and 13 have a relative permittivity and dielectric loss tangent suitable for achieving the desired reflection characteristics of the conductive layer 11.

[0073] The dielectric layers 14 and 15 are insulating polymer films such as polycarbonate, cycloolefin polymer (COP), polyethylene terephthalate (PET), and fluororesin. To minimize the overall weight of the specular reflective panel 10 while maintaining its strength, the thicknesses of the dielectric layers 14 and 15 are selected to be greater than 1.0 mm and less than 10.0 mm. If the conductive layer 11 has a thickness of 100.0 μm, the ratio of the thickness of the dielectric layers 14 and 15 to the thickness of the conductive layer 11 is greater than 10 and less than 80. By setting the thickness ratio of the dielectric layers 14 and 15 to the conductive layer 11 within this range, the specular reflective panel 10 can have sufficient mechanical strength for outdoor use and achieve the desired reflective characteristics. In situations where mechanical strength is a priority, the ratio of the thickness of the dielectric material to the conductive layer 11 may be increased as long as the reflective characteristics are not impaired.

[0074] FIG. 4 is a diagram showing an example of a layer structure in the thickness direction (Y direction) of a reflective panel 10 having a non-specular reflective surface. The layer structure shown in FIG. 4 is a layer structure in an XY cross section of the reflective panel 10, with the stacking direction being the thickness direction (Y direction) of the reflective panel 10. FIG. 4 also shows a cross section of the reflective panel 10 of an electromagnetic wave reflecting device 60, as an example, placed on the -Y direction side of the passageway 35, viewed from above (+Z direction). The reflective panel 10 having a non-specular reflective surface includes a dielectric layer 215, a conductive layer 214 held on one surface of the dielectric layer 215 by an adhesive layer 213, and a protective layer 212 covering the conductive layer 214. The dielectric layer 215 is an insulating polymer film such as polycarbonate, cycloolefin polymer (COP), polyethylene terephthalate (PET), or fluororesin, and has a thickness of approximately 0.3 mm to 1.0 mm. The dielectric layer 215 may be made of any material having a relative permittivity and dielectric loss tangent suitable for achieving the desired reflection characteristics. A ground plane 216 is formed on the surface of the dielectric layer 215 opposite to the conductive layer 214 .

[0075] The conductive layer 214 forms a metasurface of the reflective panel 10, i.e., a surface with artificially controlled reflective properties, with a non-specular reflective surface. The conductive layer 214 has a predetermined pattern formed by metal patches 211 made of a good conductor such as Cu, Ni, Ag, or Au. The conductive layer 214 has a thickness that is thick enough to reflect incident electromagnetic waves in a designed direction with sufficient strength, for example, a thickness of 10 μm to 50 μm. The adhesive layer 213 is made of a material that can support the metal patches 211 and fix them to the dielectric layer 215, and may be made of a thermoplastic resin such as vinyl acetate resin, acrylic resin, cellulose resin, or silicone resin. The thickness of the adhesive layer 213 is approximately 5 μm to 50 μm.

[0076] The protective layer 212 covering the conductive layer 214 is preferably durable, moisture-resistant, weather-resistant, and the like, and may be made of, for example, ethylene-vinyl acetate (EVA) copolymer or cycloolefin polymer (COP). The thickness of the protective layer 212 is 10 μm to 400 μm. The protective layer 212 may be formed of an adhesive layer, and a dielectric substrate such as polycarbonate may be fixed to the surface of the protective layer 212.

[0077] The above describes a configuration in which the wireless transmission system 1 includes the base station 33, the electromagnetic wave reflecting device 60, and the leaky coaxial cable 80. That is, the above describes a configuration in which the wireless transmission system includes the leaky coaxial cable 80 as a radio wave emitting unit that radiates radio waves including control signals for the autonomous traveling robot to the passageway 35.

[0078] However, such a radio wave radiating section is not limited to the leaky coaxial cable 80, and may be, for example, a DAS (Distributed Antenna System). For example, a DAS in which a master unit, a repeater, or a slave unit are connected by an optical cable may be used to radiate radio waves from the antenna of the master unit, the repeater, or the slave unit toward the passageway 35.

[0079] <Strength of the electromagnetic wave reflecting device 60> The electromagnetic wave reflecting device 60 is configured to have a strength suitable for a test conforming to the pendulum test of ISO 14120. The electromagnetic wave reflecting device 60 may be reinforced across the entire reflecting panel 10, frame 50A, legs 56, top frame 57, and bottom frame 58 so as to have a strength suitable for a test conforming to the pendulum test of ISO 14120.

[0080] For example, for the reflective panel 10, the thickness and material of the dielectric layers 14, 15 or 215 can be set so that the dielectric layers 14, 15 or 215 have strength that complies with a test in accordance with the ISO 14120 pendulum test, or the thickness and material of the two dielectric substrates that sandwich the reflective panel 10 can be set.

[0081] Furthermore, the width (thickness in the X direction in FIG. 2A), length (length in the Z direction in FIG. 2A), thickness (thickness in the Y direction in FIG. 2A), material, etc. of the frame 50A, legs 56, top frame 57, and bottom frame 58 may be set so that the entire frame has strength that complies with a test conforming to the ISO 14120 pendulum test.

[0082] <Experimental Results> The experiment was conducted in an indoor facility with a length of 100.0 m, a width of 50.0 m, and a ceiling height of 10.0 m. In the following, the width of the electromagnetic wave reflecting device 60 refers to the width in the X direction in FIG. 2, and the height of the electromagnetic wave reflecting device 60 refers to the height in the Z direction.

[0083] The electromagnetic wave reflecting devices 60 of Examples 1 to 3 below were subjected to a test conforming to the pendulum test of ISO 14120. Here, the pendulum test of ISO 14120, more specifically, is the pendulum test shown in Figure C.1 of ISO 14120:2015, which is equivalent to the pendulum test shown in Figure C.1 of JIS B 9716:2019. Therefore, a test conforming to the pendulum test of ISO 14120, more specifically, is a test conforming to the pendulum test shown in Figure C.1 of ISO 14120:2015, which is equivalent to the pendulum test shown in Figure C.1 of JIS B 9716:2019.

[0084] The pendulum test shown in Figure C.1 of ISO14120:2015 and JIS B 9716:2019 can be used to test the resistance of a guard to impacts from outside the protected danger zone and from inside the danger zone. This guard corresponds to the electromagnetic wave reflecting device 60 in this disclosure.

[0085] The pendulum test shown in Figure C.1 of ISO14120:2015 and JIS B 9716:2019 is a test in which three electromagnetic wave reflecting devices 60 are connected in the width direction (X direction in Figure 2) and a pendulum is caused to collide with the central electromagnetic wave reflecting device 60.

[0086] The height H in Figure C.1 of ISO14120:2015 and JIS B 9716:2019 is the height H of the electromagnetic wave reflecting device 60, and is set to 2000 mm as an example.

[0087] The swing height h in Figure C.1 of ISO14120:2015 and JIS B 9716:2019 is a position that is height h higher than height H, and is set to 140 mm as an example.

[0088] The height a at which the impact is applied in Figure C.1 of ISO14120:2015 and JIS B 9716:2019 is the height position at which the pendulum collides with the electromagnetic wave reflecting device 60, which is the center of the three, and is set to 1333 mm as an example.

[0089] Under these conditions, a test was conducted in accordance with the pendulum test shown in Figure C.1 of ISO14120:2015 and JIS B 9716:2019, and measurement results were obtained for two items: (1) whether the pendulum penetrated the central electromagnetic wave reflecting device 60, and (2) whether the reflective panel 10 of any of the three electromagnetic wave reflecting devices 60 had come off the frame 50A.

[0090] Hereinafter, tests conforming to the pendulum test shown in Figure C.1 of ISO14120:2015 and JIS B 9716:2019 will be referred to as tests conforming to the pendulum test of ISO14120. Having the strength that complies with the test conforming to the pendulum test of ISO14120 means that the product complies with the conditions of the two items (1) and (2) in the test conforming to the pendulum test shown in Figure C.1 of ISO14120:2015 and JIS B 9716:2019.

[0091] <Example 1> Example 1 is Working Example 1. In an indoor facility measuring 100.0 m in length, 50.0 m in width, and 10.0 m in height, ten AMRs 31, each measuring 0.7 m in length, 0.7 m in width, and 0.5 m in height, are traveling along a passageway 35. A base station 33 antenna, transmitting and receiving radio waves in a desired frequency band selected from the 4.85 GHz frequency band, is located at a height of 5.0 m, with a maximum output of 20 dBm and a half-width of 15° vertically and 30° horizontally. A linear blind zone exists within the passageway 35 of the AMRs 31 in an area behind the structure as seen from the base station 33. In the passageway 35 where the blind zone exists, an electromagnetic wave reflective fence 100A, consisting of five connected electromagnetic wave reflecting devices 60, each 1.0 m wide and 2.0 m high (5.0 m long), is installed parallel to the passageway 35. A leaky coaxial cable 80 is connected to the five electromagnetic wave reflecting devices 60. The radio wave intensity in the blind zone changed from -110.0 dBm to -90.0 dBm before and after the electromagnetic wave reflecting device 60 and the leaky coaxial cable 80 were installed, confirming an improvement of +15.0 dB.

[0092] The electromagnetic wave reflecting device 60 was subjected to a pendulum test in accordance with ISO 14120. Three electromagnetic wave reflecting devices 60 were connected in the width direction, and a pendulum was collided with the central electromagnetic wave reflecting device 60 of the three devices with an energy of E = 115 J. As a result, it was confirmed that the pendulum did not penetrate the central electromagnetic wave reflecting device 60 in item (1). Furthermore, no damage such as deformation or breakage of the frame 50A occurred in any of the three electromagnetic wave reflecting devices 60. Furthermore, it was confirmed that the reflective panel 10 did not come off the frame 50A in any of the three electromagnetic wave reflecting devices 60. In this way, it was confirmed that the electromagnetic wave reflecting device 60 of Example 1 had strength that complied with the test in accordance with ISO 14120 pendulum test.

[0093] <Example 2> Example 2 is Example 2. In an indoor facility measuring 100.0 m in length, 50.0 m in width, and 10.0 m in height, 15 AMRs 31, each measuring 0.7 m in length, 0.7 m in width, and 0.5 m in height, are traveling. A base station 33 antenna, transmitting and receiving radio waves in a desired frequency band selected from the 4.85 GHz frequency band, is located at a height of 5.0 m. The antenna has a maximum output of 20 dBm, a half-width of 15° vertically and 30° horizontally. A linear blind zone exists in a passageway 35 of the AMRs 31 behind the structure as seen from the base station 33. In the passageway 35 where the blind zone exists, an electromagnetic wave reflective fence 100A, consisting of ten connected electromagnetic wave reflecting devices 60, each 1.0 m wide and 2.0 m high (total length: 10.0 m), is installed parallel to the passageway 35. A leaky coaxial cable 80 is attached to each of the ten electromagnetic wave reflecting devices 60. The dead zone changed from -110.0 dBm to -85.0 dBm before and after the installation of the electromagnetic wave reflecting device 60 and the leaky coaxial cable 80, confirming an improvement of +25.0 dB.

[0094] The electromagnetic wave reflecting device 60 was subjected to a pendulum test in accordance with ISO 14120. Three electromagnetic wave reflecting devices 60 were connected in the width direction, and a pendulum was collided with the central electromagnetic wave reflecting device 60 of the three devices with an energy of E = 134 J. As a result, it was confirmed that the pendulum did not penetrate the central electromagnetic wave reflecting device 60 in item (1). Furthermore, no damage such as deformation or breakage of the frame 50A occurred in any of the three electromagnetic wave reflecting devices 60. Furthermore, it was confirmed that the reflective panel 10 did not come off the frame 50A in any of the three electromagnetic wave reflecting devices 60. In this way, it was confirmed that the electromagnetic wave reflecting device 60 of Example 2 had strength that complied with the test in accordance with ISO 14120 pendulum test.

[0095] <Example 3> Example 3 is a comparative example. Ten AMRs 31, each 0.5 m high, are traveling at a location 0.7 m long, 0.7 m wide, and 5 m high in an indoor facility measuring 100 m long, 50 m wide, and 10 m high. The indoor facility includes a base station 33 antenna, which transmits and receives radio waves in a desired frequency band selected from the 4.85 GHz frequency band, has a maximum output of 20 dBm, a half-width of 15° vertically, and 30° horizontally. A linear blind zone exists within a passageway 35 of the AMRs 31, behind the structure as seen from the base station 33. In the passageway 35 where the blind zone exists, an electromagnetic wave reflective fence 100A, consisting of five connected electromagnetic wave reflecting devices 60, each 1.0 m wide and 2.0 m high (5.0 m long), is installed non-parallel to the passageway 35. A leaky coaxial cable 80 is attached to the five electromagnetic wave reflecting devices 60. The radio wave intensity in the blind zone changed from -110.0 dBm to -105.0 dBm after the electromagnetic wave reflecting device 60 and the leaky coaxial cable 80 were installed, resulting in an improvement of only +5.0 dB.

[0096] The electromagnetic wave reflecting device 60 was subjected to a pendulum test in accordance with ISO 14120. Three electromagnetic wave reflecting devices 60 were connected in the width direction, and a pendulum was collided with the central electromagnetic wave reflecting device 60 of the three devices with an energy of E = 115 J. As a result, it was confirmed that the pendulum did not penetrate the central electromagnetic wave reflecting device 60 in item (1). Furthermore, no damage such as deformation or breakage of the frame 50A occurred in any of the three electromagnetic wave reflecting devices 60. Furthermore, it was confirmed that the reflective panel 10 did not come off the frame 50A in any of the three electromagnetic wave reflecting devices 60. In this way, it was confirmed that the electromagnetic wave reflecting device 60 of Example 3 had strength that complied with the test in accordance with ISO 14120 pendulum test.

[0097] From the experimental results of Examples 1 to 3, it was confirmed that by installing the electromagnetic wave reflecting devices 60 parallel to the passage 35, it was possible to reduce the blind zone in the passage 35. Furthermore, in a test based on the pendulum test of ISO 14120 in which three electromagnetic wave reflecting devices 60 were connected in the width direction, it was confirmed that all of them had strength that complied with the test based on the pendulum test of ISO 14120. Since no breakage occurred in the test based on the pendulum test of ISO 14120 in which three electromagnetic wave reflecting devices 60 were connected in the width direction, it is believed that even if four or more electromagnetic wave reflecting devices 60 are connected in the width direction, they will have strength that complies with the test based on the pendulum test of ISO 14120.

[0098] <Effects> The electromagnetic wave reflecting device 60 includes a reflective panel 10 that reflects electromagnetic waves in a predetermined band selected from 1 MHz to 300 GHz, and a frame 50A that holds the reflective panel 10, and has strength that complies with tests that comply with the pendulum test of ISO 14120. Therefore, by reflecting radio waves with the reflective panel 10, the radio wave propagation environment can be improved, and strength for safety purposes can be ensured.

[0099] Therefore, it is possible to provide an electromagnetic wave reflecting device 60 that improves the radio wave propagation environment while ensuring the strength of the electromagnetic wave reflecting device.

[0100] Furthermore, the reflective panel 10 may have a specular reflective surface where the angle of incidence and the angle of reflection of the electromagnetic wave are equal, or a non-specular reflective surface where the angle of incidence and the angle of reflection of the electromagnetic wave are different. By using an electromagnetic wave reflecting device 60 including a reflective panel 10 with a specular reflective surface or a non-specular reflective surface depending on the environment in which it is used, it is possible to eliminate blind zones and more effectively improve the radio wave propagation environment.

[0101] The electromagnetic wave reflective fence 100A may have a configuration in which a plurality of electromagnetic wave reflecting devices 60 are connected by a frame 50A. By reflecting radio waves with a plurality of reflective panels 10 of the electromagnetic wave reflective fence 100A having a configuration in which a plurality of electromagnetic wave reflecting devices 60 are connected by a frame 50A, the radio wave propagation environment can be improved and strength for safety purposes can be ensured.

[0102] Therefore, it is possible to provide an electromagnetic wave reflecting fence 100A that improves the radio wave propagation environment while ensuring the strength of the electromagnetic wave reflecting device.

[0103] The wireless transmission system 1 includes a plurality of electromagnetic wave reflecting devices 60 installed along a passage 35 of the AMR 31 on at least one side of the passage 35, and a radio wave emitting unit (a leaky coaxial cable 80 or a DAS) connected to the base station 33 and emitting radio waves including control signals of the AMR 31 into the passage 35, the electromagnetic wave reflecting device 60 having a reflective panel 10 that reflects electromagnetic waves in a predetermined band selected from 1 MHz to 300 GHz, and a frame 50A that holds the reflective panel 10, and having strength that complies with a test compliant with the pendulum test of ISO 14120. Therefore, by reflecting radio waves with the reflective panel 10, the radio wave propagation environment can be improved and strength for safety measures can be ensured.

[0104] Therefore, it is possible to provide a wireless transmission system 1 that achieves both an improvement in the radio wave propagation environment and ensuring the strength of the electromagnetic wave reflecting device.

[0105] Furthermore, the distance between each of the plurality of electromagnetic wave reflecting devices 60 and the passage 35 may be 0.1 m to 50 m. A wireless transmission system 1 can be provided that achieves both an improved radio wave propagation environment and ensuring the strength of the electromagnetic wave reflecting devices, between a distance close enough to the passage 35 that safety must be ensured according to ISO3691-4 and a distance where the radio wave reflected by the electromagnetic wave reflecting devices 60 has sufficient radio wave strength.

[0106] The height of the electromagnetic wave reflecting device 60 may be 2 m or more. For example, even in an environment where the clearance required for ensuring safety according to ISO 3691-4 cannot be secured on both sides of the passage 35 of the AMR 31, safety in the height direction can be ensured.

[0107] Although exemplary electromagnetic wave reflecting devices, electromagnetic wave reflecting fences, and wireless transmission systems of the present disclosure have been described above, the present disclosure is not limited to the specifically disclosed embodiments, and various modifications and variations are possible without departing from the scope of the claims. [Explanation of symbols]

[0108] 1. Radio transmission system 10 Reflective panel (an example of an electromagnetic wave reflecting panel) 31 AMR (an example of an autonomous mobile robot) 33 Base station 35 Passage 60 Electromagnetic wave reflector 80 Leaky coaxial cable (an example of a radio wave radiator) 100A Electromagnetic Wave Reflection Fence

Claims

1. an electromagnetic wave reflective panel that reflects electromagnetic waves in a predetermined band selected from 1 MHz to 300 GHz; a frame for holding the electromagnetic wave reflection panel; Including, An electromagnetic wave reflecting device having strength conforming to the pendulum test of ISO 14120.

2. 2. The electromagnetic wave reflecting device according to claim 1, wherein the electromagnetic wave reflecting panel has a specular reflecting surface in which the incident angle and the reflection angle of the electromagnetic wave are equal, or a non-specular reflecting surface in which the incident angle and the reflection angle of the electromagnetic wave are different.

3. 3. An electromagnetic wave reflecting fence comprising a plurality of electromagnetic wave reflecting devices according to claim 1 or 2 connected by the frame.

4. a plurality of electromagnetic wave reflecting devices provided along a path of the autonomous mobile robot on at least one side of the path; a radio wave emitting unit connected to a base station and configured to emit radio waves including a control signal for the autonomous mobile robot to the passage; Including, The electromagnetic wave reflecting device is an electromagnetic wave reflective panel that reflects electromagnetic waves in a predetermined band selected from 1 MHz to 300 GHz; a frame for holding the electromagnetic wave reflecting panel; and A wireless transmission system having strength that complies with tests in accordance with the ISO 14120 pendulum test.

5. 5. The wireless transmission system according to claim 4, wherein the distance between each of the plurality of electromagnetic wave reflecting devices and the passage is 0.1 m to 50 m.

6. 6. The wireless transmission system according to claim 4, wherein the electromagnetic wave reflecting device has a height of 2 m or more.

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