Control signal transmission system and reflect array

Abstract

To provide a control signal transmission system which can more surely transmit a control signal to a link mechanism.SOLUTION: A control signal transmission system 1 includes a base side transmission part 10 for transmitting radio waves to one or more links 41 in a link mechanism 40 having the plurality of links 41 connected to each other by a joint 42 driven by driving means through a base side antenna, a control part 20 for transmitting a control signal for instructing the one or more links 41 to change of the angle of the joint 42, through the base side transmission part 10, and a reflect array 30 for reflecting the radio waves transmitted from the base side transmission part 10, where the base side antenna and the reflect array 30 are arranged so that the link mechanism 40 is positioned between the base side antenna and the reflect array 30.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a reflectarray that reflects incident radio waves, and a control signal transmission system that uses the reflectarray. [Background technology]

[0002] Conventionally, in a link mechanism in which multiple links, such as a robot arm, are connected by joints, the joints of the link mechanism are driven by wirelessly transmitting and receiving control signals in order to reduce the amount of control wiring (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-151675 Summary of the Invention [Problem to be solved by the invention]

[0004] When using low-latency wireless communication such as millimeter wave bands to wirelessly transmit a control signal to a link in a link mechanism, radio waves have the characteristic of being highly directional and difficult to diffract. Therefore, when a link or the like exists between a transmitting antenna that transmits the control signal and a receiving antenna of the link mechanism that receives the control signal, line-of-sight communication cannot be performed between the two antennas, which can cause a problem that a control signal cannot be transmitted to the link mechanism.

[0005] The present invention has been made to solve the above-mentioned problems, and has an object to provide a control signal transmission system that can more reliably transmit a control signal to a link mechanism, and a reflectarray that can be used in the control signal transmission system. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, a control signal transmission system according to one embodiment of the present invention comprises a base-side transmitter that transmits radio waves via a base-side antenna to one or more links in a link mechanism having a plurality of links connected by joints driven by a drive means, a control unit that transmits control signals via the base-side transmitter to the one or more links instructing them to change the angle of the joint, and a reflectarray that reflects the radio waves transmitted from the base-side transmitter, and the base-side antenna and the reflectarray are arranged so that the link mechanism is located between the base-side antenna and the reflectarray. With this configuration, even if line-of-sight communication is not possible between the base station antenna that transmits the control signal and the receiving antenna of the link mechanism that receives the control signal, the reflectarray can reflect radio waves, making it possible to more reliably transmit the control signal to the link mechanism via non-line-of-sight communication.

[0007] In addition, in a control signal transmission system according to one aspect of the present invention, the reflectarray may be arranged in a link side communication unit provided in the link so as to perform non-line-of-sight communication even when line-of-sight communication is blocked due to operation of the link. With this configuration, even if line-of-sight communication between the base station antenna and the link antenna becomes impossible due to the drive of the joint of the link mechanism, non-line-of-sight communication can be performed between the two antennas via the reflectarray.

[0008] In addition, in a control signal transmission system according to one embodiment of the present invention, the base station antenna has a directivity set so that radio waves are radiated toward the link mechanism, the reflectarray has a plurality of reflective elements arranged in a planar manner and is arranged so that the radio waves radiated from the base station antenna are incident on the reflectarray from a direction approximately normal to the reflectarray, and the plurality of reflective elements may be arranged so as to satisfy an endfire condition. With this configuration, the reflectarray can diffuse the incident radio waves in multiple directions, allowing the control signal transmitted from the base station antenna to be more reliably received by the receiving antenna of the link mechanism.

[0009] Furthermore, a reflectarray according to one embodiment of the present invention is a reflectarray that reflects incident radio waves, and has a plurality of reflective elements arranged in a plane, the plurality of reflective elements being arranged so as to satisfy an endfire condition, the plurality of reflective elements being arranged at intervals of half the wavelength of the radio waves in a first direction and a second direction perpendicular to the first direction, the reflection phases of two adjacent reflective elements in the first and second directions are substantially 180 degrees different, and in each of first and second reflective element rows that are two adjacent rows of reflective elements along the first direction, the phase difference between the reflection phases of the reflective elements at the first and second positions in the first direction may be the same. With this configuration, the reflectarray can diffuse radio waves, thereby expanding the range in which radio waves can be received in non-line-of-sight communications, for example. Effect of the Invention

[0010] According to the control signal transmission system of one aspect of the present invention, even if line-of-sight communication is not possible between the antenna on the control signal transmission side and the antenna on the receiving side of the link mechanism, the reflectarray can reflect radio waves, making it possible to more reliably transmit the control signal to the link mechanism by non-line-of-sight communication. Furthermore, the reflectarray of one aspect of the present invention can diffuse incident radio waves in many directions, thereby making it possible to expand the range in which radio waves can be received by non-line-of-sight communication, for example. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing a configuration of a link mechanism control device according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a schematic diagram showing an overview of a reflectarray according to the embodiment; [Diagram 3] FIG. 4 is an enlarged perspective view showing a reflecting element in the embodiment; [Figure 4] Graph showing the relationship between the diameter of a patch element and the reflection phase in the embodiment. [Diagram 5] FIG. 13 is a diagram showing a propagation space of radio waves used in a simulation in the embodiment; [Figure 6A] FIG. 13 is a diagram showing an electric field distribution obtained as a result of a simulation in the embodiment; [Figure 6B] FIG. 13 is a diagram showing an electric field distribution obtained as a result of a simulation in the embodiment; [Figure 7] FIG. 13 shows a reflection pattern that is a simulation result in the embodiment. [Figure 8A] FIG. 4 is an enlarged perspective view showing a reflecting element in the embodiment; [Figure 8B] FIG. 4 is an enlarged front view showing a reflecting element in the embodiment; [Figure 9] Graph showing the relationship between the length of a patch element and the reflection phase in the embodiment. [Figure 10] FIG. 2 is a plan view showing the configuration of a reflectarray according to the embodiment; [Figure 11A] FIG. 13 shows a reflection pattern that is a simulation result according to the embodiment. [Figure 11B] FIG. 13 shows a reflection pattern that is a simulation result according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The control signal transmission system and reflectarray according to the present invention will be described below using embodiments. Note that in the following embodiments, components with the same reference numerals are the same or equivalent, and repeated description may be omitted. In the control signal transmission system according to this embodiment, the base station antenna that transmits the control signal and the reflectarray are arranged with a link mechanism located between them, so that the control signal can be reliably transmitted by the receiving antenna of the link mechanism by line-of-sight communication or non-line-of-sight communication via the reflectarray.

[0013] FIG. 1 is a block diagram showing a configuration of a link mechanism control system 100 according to this embodiment. The link mechanism control system 100 according to this embodiment includes a control signal transmission system 1 for transmitting a control signal to a link mechanism 40, and a link mechanism 40 having a plurality of links 41a to 41e connected by joints 42a to 42d. When the links 41a to 41e and the joints 42a to 42d are not particularly distinguished from each other, they may be referred to as links 41 and joints 42. The same applies to the other components. The control signal transmission system 1 includes a base station side transmitter 10 for transmitting radio waves to the link mechanism 40, a control unit 20 for transmitting a control signal via the base station side transmitter 10, and a reflectarray 30 for reflecting the radio waves of the incident control signal.

[0014] The radio waves used for transmitting and receiving the control signal may be, for example, millimeter waves, submillimeter waves, terahertz waves, or other radio waves with a wavelength of 10 mm or less. In this embodiment, the case where the control signal is transmitted and received by millimeter waves will be mainly described.

[0015] The base-side transmitter 10 transmits radio waves to one or more links 41 in the link mechanism 40 via a base-side antenna. A link-side communication unit 51, which will be described later, changes position in response to changes in the angle of each joint 42 of the link mechanism 40, whereas the base-side transmitter 10 is a fixed communication unit whose position does not change. For example, the base-side transmitter 10 may be considered to correspond to an access point whose position is fixed, and the link-side communication unit 51 to correspond to a mobile terminal (STA: station) whose position may change. The base-side transmitter 10 may have, for example, a base-side antenna and a communication circuit for transmitting and receiving wireless signals via the base-side antenna.

[0016] In this embodiment, the case where the base station side transmitting unit 10 only transmits radio waves will be mainly described, but the base station side transmitting unit 10 may receive radio waves transmitted from the link mechanism 40. In this case, the base station side transmitting unit 10 may be a communication unit that transmits and receives radio waves to and from the link mechanism 40. Also, in this embodiment, the case where the control signal transmission system 1 includes only one base station side transmitting unit 10 will mainly be described, but this is not necessarily the case. The control signal transmission system 1 may include two or more base station side transmitting units 10. In this case, the control unit 20 may transmit the control signal by appropriately switching the base station side transmitting unit 10 used to transmit the control signal.

[0017] The base-side antenna may be, for example, a highly directional antenna. The highly directional antenna is not particularly limited, and may be, for example, an array antenna such as a phased array antenna. The directivity of the base-side antenna may be set so that radio waves are emitted toward the link mechanism 40. That is, the main beam emitted from the base-side antenna may be set so as to face the link mechanism 40. In addition, in the base-side transmitter 10, for example, the base-side antenna and the communication circuit may be provided integrally. This is because, when transmitting and receiving radio waves with short wavelengths such as millimeter waves, the cost of the cable connecting the antenna and the communication circuit becomes high. In addition, for example, an antenna cover may be provided to protect the base-side antenna. A material with high radio wave transmittance is usually used for the antenna cover.

[0018] The control unit 20 transmits a control signal to one or more links 41 via the base-side transmitter 10 to instruct the change of the angle of the joint 42. As an example, the control signal may include information identifying the joint 42 to be changed. The control signal may also include, for example, the absolute angle of the joint 42 after the change, or the difference in the angle of the joint 42, i.e., the relative angle. As an example, when changing the angle of the joint 42b, the control unit 20 may transmit a control signal including information identifying the joint 42b and an instruction to change the angle of the joint 42b. In addition, when the base-side transmitter 10 also receives radio waves transmitted from the link mechanism 40, the control unit 20 may receive, for example, the changed angle of each joint 42 via the base-side transmitter 10.

[0019] The reflectarray 30 reflects radio waves transmitted from the base station transmitter 10. As shown in FIG. 2, the reflectarray 30 may include, for example, a plurality of reflecting elements 31 arranged in a plane. The plurality of reflecting elements 31 may be arranged, for example, at intervals of half the wavelength (λ / 2) of the incident radio waves in a first direction and in a second direction perpendicular to the first direction. The plurality of reflecting elements 31 may include, for example, a plurality of types of reflecting elements 31. As an example, the plurality of types of reflecting elements 31 may be three types of reflecting elements 31a, 31b, and 31c as shown in FIG. 2. The plurality of reflecting elements 31 may be arranged so as to satisfy the end-fire condition. The arrangement of the plurality of reflecting elements 31 so as to satisfy the end-fire condition means that the positions of the plurality of reflecting elements 31 and the phase difference of the reflection phase are set so that the radio waves incident from the normal direction of the reflectarray 30 are theoretically reflected in the surface direction of the reflectarray 30, i.e., in the end-fire direction. In the reflectarray 30 in which the reflecting elements 31 are arranged to satisfy the endfire condition, in theory, the radio waves incident from the normal direction are reflected in the plane direction of the reflectarray 30. However, in reality, as shown in the simulation results described later, the radio waves incident from the normal direction are also reflected in other directions, for example, in directions having angles within a predetermined range with respect to the plane direction of the reflectarray 30. In addition, it is preferable that the reflectarray 30 is arranged, for example, in the link side communication unit 51 provided in the link 41 so as to perform non-line-of-sight communication even when line-of-sight communication is blocked by the operation of the link 41. As an example of such an arrangement, the reflectarray 30 may be arranged so that the direction of the main beam of the radio waves radiated from the base station side antenna is perpendicular to the plane direction of the reflectarray 30. The detailed configuration of the reflectarray 30 will be described later.

[0020] Here, the arrangement of the base-side antenna of the base-side transmitter 10, the reflectarray 30, and the link mechanism 40 will be described. It is preferable that the base-side antenna and the reflectarray 30 are arranged such that the link mechanism 40 is located between the base-side antenna and the reflectarray 30. As an example, as shown in Fig. 1, the base-side antenna of the base-side transmitter 10 may be arranged on the ceiling 5 of the environment in which the link mechanism 40 is installed, and the reflectarray 30 may be arranged on the floor surface 4 facing the ceiling 5, with the link mechanism 40 located between them.

[0021] The arrangement shown in FIG. 1 is an example, and the base-side antenna and the reflectarray 30 may be arranged at other positions. For example, the base-side antenna may be arranged on the floor surface 4 of the environment in which the link mechanism 40 is installed, and the reflectarray 30 may be arranged on the ceiling 5 facing the floor surface 4, or the base-side antenna may be arranged on a first wall surface, and the reflectarray 30 may be arranged on a second wall surface facing the first wall surface. In either case, it is preferable that the link mechanism 40 exists between the base-side antenna of the base-side transmitter 10 and the reflectarray 30. It is also preferable that the directivity of the base-side antenna of the base-side transmitter 10 is set so that radio waves are radiated toward the link mechanism 40. It is also preferable that the reflectarray 30 is arranged so that radio waves radiated from the base-side antenna of the base-side transmitter 10 are incident from a substantially normal direction. The normal direction here means to include a direction slightly deviated from the strict normal direction, and the range of this deviation is preferably such that, for example, the radio waves incident on the reflectarray 30 from the normal direction are suitably diffused by the reflectarray 30. Note that the radio waves radiated from the base station antenna incident on the reflectarray 30 from a substantially normal direction may mean that the direction of the main beam of the radio waves radiated from the base station antenna is the normal direction of the reflectarray 30. For ease of explanation, the control signal transmission system 1 shown in Figure 1 shows a case where some of the radio waves radiated from the base station antenna are incident on the reflectarray 30 from a direction other than the normal. However, at the site where the link mechanism 40 is installed, the distance between the floor 4 and the ceiling 5 is often large, and in such a site, the radio waves radiated from the base station antenna will be incident on the reflectarray 30 in an approximately normal direction. Also, in a case like Figure 1 where the distance between the floor 4 and the ceiling 5 is small, the base station antenna can be shaped to extend in the plane direction of the ceiling 5, allowing the radio waves to be incident in an approximately normal direction.

[0022] The link mechanism 40 has a plurality of links 41a to 41e connected by joints 42a to 42d driven by a driving means. In the link mechanism 40, the two connected links 41 are rotatable at the joint 42 by the driving means. In this embodiment, the link mechanism 40 is mainly described as having motors 43a to 43d as driving means for driving the joints 42a to 42d, respectively. In addition, each joint 42 of the link mechanism 40 may be provided with a sensor such as an encoder for acquiring the angle of the joint 42. In addition, of the plurality of links 41, the link 41a on the base end side may be fixed to a base 45, for example.

[0023] The link mechanism 40 may be, for example, a vertical multi-joint robot, a horizontal multi-joint robot, or another robot arm in which a plurality of links 41 are connected by joints 42. The link mechanism 40 may be, for example, something other than a robot arm. There is no particular limitation on the link mechanism 40 other than a robot arm, but examples of the link mechanism 40 include the legs of a quadruped robot, and the arms and legs of a humanoid robot.

[0024] In addition, in this embodiment, the link mechanism 40 will be mainly described as having five links 41, but the number of links 41 that the link mechanism 40 has is not limited. For example, the link mechanism 40 may have two, three, or four links 41, or may have six or more links 41. The multiple links 41 are usually connected in series. In addition, in this embodiment, for convenience of explanation, the hand unit (end effector) at the tip of the link mechanism 40 will be described as one link 41. The hand unit may, for example, hold a transport object or the like, perform work such as assembly or welding, or may be used for other purposes. Power may be supplied to each link 41 by, for example, a wired wiring, or may be supplied wirelessly at a joint portion as in Patent Document 1. In addition, when the link 41a on the base end side is fixed to the base 45, the supply of power to the motor 43a of the link 41a and the transmission of a control signal may be performed by a wired wiring. In this embodiment, a case will be mainly described in which the control signal to the link 41a is also transmitted wirelessly.

[0025] The links 41a to 41d may be provided with link side control units 50a to 50d, respectively. The link side control unit 50 may have a link side communication unit 51 for receiving radio waves, and a joint control unit 52 for changing the angle of the joint 42 in response to a control signal received via the link side communication unit 51. Note that, for example, when transmitting the changed angle of the joint 42 to the control unit 20, the link side communication unit 51 may also transmit radio waves, and the joint control unit 52 may transmit the changed angle of the joint 42 to the control unit 20 via the link side communication unit 51.

[0026] In this embodiment, the link mechanism 40 has a plurality of links 41a-41e, and four of the links 41a-41d are provided with link side control units 50a-50d, respectively. However, it is sufficient that one or more link side control units 50 are provided for each of the plurality of links 41 in the link mechanism 40, and the number of links 41 provided with link side control units 50 is not important. In addition, for example, when the link 41e, which is a hand unit, also has a control target such as a drive means, the link 41e may also be provided with the link side control unit 50.

[0027] The link side communication unit 51 may have, for example, an antenna for receiving radio waves and a communication circuit for receiving a wireless signal via the antenna. The antenna is preferably disposed outside the housing of the link 41. Also, for example, the antenna and the communication circuit may be provided integrally.

[0028] The joint control unit 52 may, for example, control the angle of the joint 42 on the tip side of the link 41 to which the joint control unit 52 is provided, or may control the angle of the joint 42 on the base end side of the link 41, or may do both. In this embodiment, a case will be mainly described in which the joint control unit 52 controls the angle of the joint 42 on the tip side of the link 41, that is, a case in which the joint control units 52a to 52d control the angles of the joints 42a to 42d by controlling the motors 43a to 43d, respectively.

[0029] When the joint control unit 52 receives a control signal via the link side communication unit 51, it drives the motor 43 in response to the control signal to change the angle of the joint 42. When the control signal includes an absolute angle of the joint 42 after the change, the joint control unit 52 may control the motor 43 so that the angle of the joint 42 becomes the absolute angle. When the control signal includes a relative angle of the joint 42, the joint control unit 52 may control the motor 43 so that the angle of the joint 42 changes by the amount of the relative angle.

[0030] The joint control unit 52 may transmit, for example, the changed angle of the joint 42 to the control unit 20 via the link side communication unit 51. The angle to be transmitted may also be, for example, an absolute angle or a relative angle. The changed angle of the joint 42 may be acquired by a sensor such as an encoder. Furthermore, the joint control unit 52 may be disposed inside the housing of the link 41, for example.

[0031] Next, the transmission of radio waves from the base-side transmitter 10 to the link-side communication unit 51 will be described. The control unit 20 may transmit, for example, a control signal including information for identifying a certain joint 42 and an instruction to change the angle of the joint 42 via the base-side transmitter 10. This control signal is transmitted by line-of-sight communication when the base-side antenna of the base-side transmitter 10 and the antenna of the link-side communication unit 51 of the link mechanism 40 are in line of sight, and when both antennas are not in line of sight, the control signal is transmitted by non-line-of-sight communication via diffusion of radio waves by the reflectarray 30. For example, as shown in FIG. 1, a control signal may be transmitted to the link-side communication units 51c and 51d by line-of-sight communication, and a control signal may be transmitted to the link-side communication units 51a and 51b by non-line-of-sight communication via the reflectarray 30.

[0032] The transmitted control signal is received by each link side communication unit 51 of the link mechanism 40 and passed to the joint control unit 52. If the control signal includes information identifying the joint 42 to be controlled, the joint control unit 52 performs control according to an instruction to change the angle of the joint 42 included in the control signal, and if not, the joint control unit 52 may discard the control signal. Note that the discarding of the control signal may be performed by, for example, the link side communication unit 51. Furthermore, if necessary, the angle of the joint 42 after the change may be transmitted from the joint control unit 52 to the control unit 20 via the link side communication unit 51.

[0033] Next, the configuration of the reflectarray 30 will be described. First, a one-dimensional reflectarray in which the reflecting elements 31 are arranged in a row at intervals of a half wavelength of the incident radio wave will be described with reference to FIG. 2. Here, the row direction is the x-axis direction. In this one-dimensional reflectarray, in order for the reflected waves of the reflecting elements 31 of the plane waves incident from a direction perpendicular to the x-axis direction to be constructive with each other in the positive direction of the x-axis, the phase difference between the reflected waves of the adjacent reflecting elements 31 needs to be 180 degrees. Also, in order for the reflected waves of the reflecting elements 31 to be constructive with each other in the negative direction of the x-axis, the phase difference between the adjacent reflecting elements 31 needs to be -180 degrees. Therefore, by making the reflection phases, which are the phases of the reflected waves of the adjacent reflecting elements 31, different by 180 degrees in the multiple reflecting elements 31 arranged at intervals of a half wavelength in the x-axis direction, the radio wave incident from a direction perpendicular to the x-axis is theoretically reflected along the x-axis direction, thereby satisfying the endfire condition.

[0034] For example, FIG. 3 shows an enlarged view of a reflecting element 31. The reflection phase of the reflecting element 31 having a circular patch element 32 arranged on a dielectric substrate 33 shown in FIG. 3 changes according to the diameter of the patch element 32 as shown in FIG. 4. As shown in FIG. 4, a sudden change in the reflection phase is caused by resonance in the TM11 mode (fundamental mode). The dielectric substrate 33 has a relative dielectric constant of 2.2 and a thickness of 0.508 mm. In addition, a GND conductor is provided on the entire surface of the dielectric substrate 33 opposite to the surface on which the patch element 32 is provided. The frequency of the radio wave is 60 GHz. An infinite periodic boundary condition is set by setting the side of the analysis space as an electric wall (Perfect Electric Conductor) and a magnetic wall (Perfect Magnetic Conductor). In this case, as shown in the graph of Fig. 4, by arranging multiple reflecting elements 31 in a row at intervals of half a wavelength (=2.5 mm) so that a reflecting element 31 having a patch element 32 with a diameter of 1.1 mm is adjacent to a reflecting element 31 having a patch element 32 with a diameter of 1.8 mm, it becomes possible, in theory, to reflect radio waves incident from a direction perpendicular to the row direction in the row direction, thereby satisfying the endfire condition. In such a one-dimensional reflectarray, two types of reflecting elements 31, reflecting elements 31 with the same reflection phase and reflecting elements 31 with the opposite reflection phase, are arranged alternately at half-wavelength intervals.

[0035] A simulation was performed to confirm the effect of this one-dimensional reflectarray. In this simulation, as shown in Fig. 5, a space with a height and width of 50 mm and a depth of 2.5 mm was set as the space through which 60 GHz millimeter waves propagate. The height and width correspond to 10 wavelengths, and the depth corresponds to a half wavelength. As for the boundary conditions, an infinite periodic boundary condition was set by making the 50 mm x 50 mm surface an electric wall. The 50 mm x 2.5 mm surface was set as a radiation boundary. In addition, as shown by the downward arrow in Fig. 5, it was set so that a plane wave was incident from above to below. In addition, a conductive screen 61 with a width of 20 mm and a depth of 2.5 mm was placed in the middle of the millimeter wave propagation space. This screen 61 blocks part of the incident plane wave.

[0036] The one-dimensional reflectarray is configured by arranging reflecting elements 31a having patch elements with a diameter of 1.8 mm and reflecting elements 31b having patch elements with a diameter of 1.1 mm in a line at intervals of half a wavelength (2.5 mm). In this case, as described above, the endfire condition is satisfied in the arrangement direction of reflecting elements 31, i.e., the endfire direction, in which the reflected waves reinforce each other.

[0037] 6A and 6B are diagrams showing the electric field distribution of the incident wave and the reflected wave, which are the results of the simulation. FIG. 6A shows the simulation result in the case where the reflectarray is not present, and FIG. 6B shows the simulation result in the case where the reflectarray is present. When the reflectarray is not present, the simulation was performed assuming that a conductor is present at the position of the reflectarray. When the reflectarray is not present, as shown in FIG. 6A, a part of the incident plane wave is blocked by the screen 61, and a blind zone is formed below the screen 61. On the other hand, when the reflectarray is present, as shown in FIG. 6B, the radio waves are diffused below the screen 61 by the reflectarray, and no blind zone is formed below the screen 61.

[0038] FIG. 7 is a diagram showing the results of a simulation showing the relationship between the angle with respect to the normal direction of the reflectarray and the directivity of the reflected wave. FIG. 7 shows the reflection pattern of the H-plane when linearly polarized waves are incident. In addition, FIG. 7 shows the simulation results with the reflectarray in solid lines and the simulation results without the reflectarray in dashed lines. As shown in FIG. 7, it can be seen that the presence of the reflectarray greatly increases the reflected wave in directions close to ±90 degrees, that is, in directions close to the arrangement direction of the reflecting elements 31 in the reflectarray. From FIG. 6B and FIG. 7, it can be seen that the one-dimensional reflectarray satisfies the endfire condition, and thus the reflected wave is diffused in many directions, and as a result, blind zones are eliminated.

[0039] To extend a one-dimensional reflectarray to a two-dimensional reflectarray, it seems that one-dimensional reflectarrays should be arranged at intervals of half the wavelength of radio waves and adjacent one-dimensional reflectarrays should be shifted by half the wavelength in the one-dimensional direction. That is, it seems that two reflecting elements 31a and 31b with reflection phases differing by 180 degrees should be arranged in a staggered pattern. However, with such an arrangement of the reflecting elements 31, the phase difference between the reflected waves of adjacent one-dimensional reflectarrays will be of opposite signs, and the signals will be offset, making it impossible to form a desired beam. Therefore, as will be described later, in a two-dimensional reflectarray that satisfies the endfire condition, for example, three types of reflecting elements 31 with phase differences of the reflected waves of 180 degrees and 360 degrees may be arranged in a plane.

[0040] First, three types of reflecting elements 31 will be described. In this case, in order to change the reflection phase by 360 degrees or more, reflecting element 31 has two layers of patch elements 32a and 32b, for example, as shown in FIG. 8A and FIG. 8B. FIG. 8A is a perspective view showing reflecting element 31, and FIG. 8B is a front view of reflecting element 31. Patch elements 32a and 32b are each square-shaped and arranged so that their centers of gravity overlap in a plan view. In addition, the thickness h1 of upper dielectric substrate 33a and the thickness h2 of lower dielectric substrate 33b are the same, 0.508 mm. In addition, the relative dielectric constants of upper and lower substrates 33a and 33b are the same, 2.2. In addition, the frequency of the radio wave is set to 60 GHz, and the element spacing p of reflecting element 31 is set to 2.5 mm, which is a half wavelength. The ratio a of the length L1 of one side of upper patch element 32a to the length L2 of one side of lower patch element 32b is fixed at 0.7. Also, a GND conductor is provided on the entire back surface of lower substrate 33b, i.e., the surface opposite to the surface on which patch element 32b is provided. An infinite periodic boundary condition is set by treating the sides of the analysis space as electric and magnetic walls. In this case, the reflection phase of reflecting element 31 changes according to the length L2 of one side of patch element 32b as shown in FIG. 9. Therefore, reflecting element 31 with L2=0.95 mm is used as an in-phase (0) reflecting element, reflecting element 31 with L2=1.6 mm is used as an anti-phase (π) reflecting element, and reflecting element 31 with L2=2.1 mm is used as an in-phase (2π) reflecting element.

[0041] The two-dimensional reflectarray 30 that reflects the incident radio wave is composed of 256 (=16×16) reflecting elements 31 arranged in a plane as shown in the plan view of FIG. 10. In this case, the overall dimensions of the reflectarray 30 are 40 mm square. Here, the first direction is the x-axis direction in FIG. 10, and the second direction perpendicular to the first direction is the y-axis direction in FIG. 10. In the two-dimensional reflectarray 30, the multiple reflecting elements 31 are arranged at intervals of half the wavelength (=2.5 mm) of the incident radio wave in the first and second directions. In the two-dimensional reflectarray 30, an in-phase (0) reflecting element 31a, an out-of-phase (π) reflecting element 31b, and an in-phase (2π) reflecting element 31c are arranged as shown in the enlarged portion on the right side of FIG. 10, and the arrangement is repeated throughout the reflectarray 30.

[0042] As shown in the enlarged portion of FIG. 10, the reflection phases of two adjacent reflecting elements 31 in the first and second directions of the two-dimensional reflectarray 30 are different by 180 degrees. In addition, in each of the first and second reflecting element rows, which are two adjacent rows of reflecting elements 31 along the first direction, the phase difference between the reflection phases of the reflecting elements 31 at the first and second positions in the first direction is the same. More specifically, in the four reflecting elements 31 included in the enlarged portion on the right side of FIG. 10, the two reflecting elements 31 on the left side are included in the first reflecting element row, and the two reflecting elements 31 on the right side are included in the second reflecting element row. In addition, the reflecting elements 31 at the first position in the first direction are the upper two reflecting elements 31, and the reflecting elements at the second position are the lower two reflecting elements 31. In this case, the phase difference between the reflection phases of the reflection elements 31 at the first and second positions in the first direction in the first reflection element row is 180 degrees (π), and the phase difference between the reflection phases of the reflection elements 31 at the first and second positions in the first direction in the second reflection element row is also 180 degrees (π). Furthermore, by arranging the reflection elements 31 in this manner, the phase difference between the reflection phases of the reflection elements 31 at the first and second positions in the second direction in each of the first and second reflection element rows, which are two adjacent rows of the reflection elements 31 along the second direction, is the same. As a result, in the two-dimensional reflectarray 30 shown in FIG. 10, in-phase and out-of-phase reflection elements 31 are alternately arranged at half-wavelength intervals in each row in the first and second directions, and the phase difference between two adjacent reflection element rows in the first and second directions does not have an inverse sign, so that signals are not cancelled out. 10 are theoretically arranged so as to reflect radio waves incident from the normal direction of the reflectarray 30 in the plane direction of the reflectarray 30, i.e., in the endfire direction. In this way, in the two-dimensional reflectarray 30 shown in FIG 10, the multiple reflecting elements 31 are arranged so as to satisfy the endfire condition.In the above description, the reflection phases of two adjacent reflecting elements 31 in the first and second directions of the reflectarray 30 differ by 180 degrees, but this is not necessary. The reflection phases of two adjacent reflecting elements 31 in the first and second directions of the reflectarray 30 may differ by substantially 180 degrees. This is because even if the reflection phases of two adjacent reflecting elements 31 are close to 180 degrees, it is considered that the incident radio waves can be diffused by such a reflectarray 30. The range of deviation from 180 degrees may be, for example, to the extent that the radio waves incident on the reflectarray 30 are suitably diffused by the reflectarray 30.

[0043] 11A and 11B are diagrams showing the results of a simulation of a reflection pattern when a linearly polarized wave is incident from the normal direction of the two-dimensional reflectarray 30 shown in FIG. 10. FIG. 11A shows the reflection pattern of the E plane, and FIG. 11B shows the reflection pattern of the H plane. Also, FIG. 11A and FIG. 11B are diagrams showing the relationship between the angle with respect to the normal direction of the reflectarray 30 and the directivity of the reflected wave. As shown in FIG. 11A and FIG. 11B, by using the two-dimensional reflectarray 30 of FIG. 10, the reflected wave at a wide angle of ±60 degrees to ±90 degrees is greatly increased, and it can be seen that the reflected wave is diffused in the plane direction of the reflectarray 30. Therefore, as shown in FIG. 1, when transmitting radio waves from the base antenna of the base transmission unit 10 to the link mechanism 40, the use of this reflectarray 30 can eliminate blind zones, and each link side communication unit 51 can reliably transmit a control signal. In addition, when the multiple reflective elements 31 of the reflectarray 30 satisfy the endfire condition, in theory, radio waves will be reflected in directions of ±90 degrees. In reality, however, as shown in Figures 11A and 11B, the reflected waves are large in the range of ±60 degrees to ±90 degrees.

[0044] 11A and 11B, it can be seen that strong physical reflection in the 0 degree direction remains. This is believed to be caused by the apparent impedance of the reflectarray 30 not being matched with the space. Therefore, it is believed that the physical reflection in the 0 degree direction can be improved by adjusting the dimensions and shape of the patch element 32.

[0045] As described above, according to the link mechanism control system 100 of this embodiment, even if line-of-sight communication cannot be performed between the base-side antenna of the base-side transmitter 10 and the antenna of the link-side communication unit 51, the radio waves can be reflected by the reflectarray 30, and the control signal can be more reliably transmitted to the link mechanism 40 by non-line-of-sight communication. Furthermore, according to the reflectarray 30 of this embodiment, by satisfying the end-fire condition, the incident radio waves can be diffused in multiple directions, and blind zones can be eliminated. As a result, the control signal transmitted from the base-side antenna can be more reliably received by the antenna of the link-side communication unit 51.

[0046] In the control signal transmission system 1 according to this embodiment, a reflectarray other than the reflectarray 30 that satisfies the endfire condition may be used. Even in this case, it is preferable that the reflectarray be one that can reduce a blind zone when a control signal is transmitted from the base station transmitter 10 to the link mechanism 40.

[0047] Although the present embodiment has been described mainly with reference to the case where the reflectarray 30 is used to reliably transmit the control signal sent from the base station transmitter 10 by the antenna of the link side communication unit 51 of the link mechanism 40, the reflectarray 30 may be used for other purposes as well. For example, the reflectarray 30 may be used to reduce blind zones in indoor communications using radio waves with short wavelengths such as millimeter waves.

[0048] In addition, in this embodiment, the case where the multiple reflecting elements 31 of the reflectarray 30 are composed of square-shaped patch elements 32 has been mainly described, but this is not essential. The reflecting elements 31 of the reflectarray 30 may be composed of something other than patch elements, such as slots or dipole antennas. Even when the reflecting elements 31 of the reflectarray 30 are composed of patch elements 32, a reflecting element composed of patch elements different from those described above, for example, patch elements with different sizes, shapes, number of layers, thickness of the dielectric substrate, etc., may be used.

[0049] In the present embodiment, each component may be configured by dedicated hardware, or a component that can be realized by software may be realized by executing a program. For example, each component may be realized by a program execution unit such as a CPU reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory.

[0050] The above-mentioned embodiments are merely examples for specifically implementing the present invention, and are not intended to limit the technical scope of the present invention. The technical scope of the present invention is indicated by the claims, not by the description of the embodiments, and is intended to include modifications within the literal scope of the claims and the scope of equivalent meanings. [Explanation of symbols]

[0051] 1. Control signal transmission system 10 Base station transmitter 20 Control section 30 Reflect Array 31, 31a, 31b, 31c Reflective elements

Claims

1. a base station side transmitter that transmits radio waves via a base station side antenna to one or more links in a link mechanism having a plurality of links connected by joints driven by a drive means; a control unit that transmits a control signal to the one or more links via the base station side transmitting unit, the control signal instructing the one or more links to change an angle of the joint; a reflectarray that reflects the radio wave transmitted from the base station side transmitter, a base station antenna and a reflectarray arranged such that the link mechanism is located between the base station antenna and the reflectarray.

2. 2. The control signal transmission system according to claim 1, wherein the reflectarray is arranged in a link side communication unit provided in the link so as to perform non-line-of-sight communication even when line-of-sight communication is blocked by operation of the link.

3. The base station antenna has a directivity set so that radio waves are radiated toward the link mechanism, the reflectarray has a plurality of reflecting elements arranged in a plane, and is arranged such that radio waves radiated from the base station antenna are incident on the reflectarray from a direction substantially normal to the reflectarray; 3. The control signal transmission system according to claim 1, wherein the plurality of reflective elements are arranged so as to satisfy an endfire condition.

4. A reflectarray that reflects incident radio waves, The reflector has a plurality of reflecting elements arranged in a plane, the plurality of reflective elements are arranged at intervals of a half wavelength of the radio wave in a first direction and in a second direction perpendicular to the first direction, The reflection phases of two adjacent reflection elements in the first and second directions are substantially 180 degrees different from each other, A reflectarray, in which in each of first and second reflective element rows, which are two adjacent rows of reflective elements along the first direction, the phase difference between the reflection phases of the reflective elements at first and second positions in the first direction is the same.

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