Fixed station, mobile unit, communication system, and beam direction control method

Abstract

Provided is a fixed station that performs free space optical communication with a moving body for which a movement path is not determined in advance, the fixed station comprising: a movement control information receiving unit that receives movement control information, which is sent from a moving body steering terminal that controls operations of the moving body and which is information for causing the moving body to move to a specified position; an adjustment amount calculation unit that calculates, for every control cycle, an adjustment amount for controlling an emission direction of a beam by predicting a velocity change of the moving body on the basis of the movement control information received by the movement control information receiving unit; and a direction control unit that controls, for every control cycle, the emission direction of the beam on the basis of the adjustment amount for every control cycle calculated by the adjustment amount calculation unit.　

Description

Technical Field

[0001] The present invention relates to a fixed station, a mobile body, a communication system, and a beam direction control method.

Background Art

[0002] Conventionally, technologies related to free space optical communication (FSO) have been proposed (see, for example, Non-Patent Document 1). Free space optical communication is a technology that emits laser light into space for communication. Free space optical communication can be used not only between fixed stations but also between a fixed station and a mobile body. In the technology disclosed in Non-Patent Document 1, free space optical communication is performed between a train as a mobile body and a terrestrial station as a fixed station.

[0003] FIG. 8 is a diagram showing a configuration example of a conventional communication system 1000. The communication system 1000 includes a fixed station 150, a mobile body 250, and a mobile longitudinal terminal 350. The fixed station 150 performs free space optical communication with the mobile body 250 by controlling the irradiation direction of the beam. The mobile body 250 is, for example, a train, and performs free space optical communication with the fixed station 150 by controlling the irradiation direction of the beam. The mobile body 250 moves in response to an instruction from the mobile longitudinal terminal 350. When the mobile body 250 is a train, the mobile longitudinal terminal 350 is provided inside the train. The mobile longitudinal terminal 350 controls the mobile body 250 by transmitting movement control information including a movement instruction to the mobile body 250.

[0004] The fixed station 150 comprises a data processing unit 101, an optical signal transmission unit 102, an optical signal reception unit 103, a data acquisition unit 104, a transmit / receive coupling unit 105, a distribution unit 106, a direction control mechanism 107, an optical signal center deviation detection unit 108, a direction adjustment amount calculation unit 109, and a direction control unit 110. The mobile unit 250 comprises a data processing unit 201, an optical signal transmission unit 202, an optical signal reception unit 203, a data acquisition unit 204, a transmit / receive coupling unit 205, a distribution unit 206, a direction control mechanism 207, an optical signal center deviation detection unit 208, a direction adjustment amount calculation unit 209, a direction control unit 210, a mobile control information reception unit 211, and a mobile unit control unit 212.

[0005] The data processing unit 101 performs framing and signal processing on the data to be transmitted to the mobile body 200. The optical signal transmission unit 102 converts the output signal of the data processing unit 101 into an optical signal. The optical signal receiving unit 103 receives the optical signal transmitted from the mobile body 250 and converts the received optical signal into an electrical signal. The data acquisition unit 104 performs signal processing such as demodulation and decoding, as well as deframing, on the output of the optical signal receiving unit 103. The transmit / receive coupling unit 105 outputs the optical signal output from the optical signal transmission unit 102 and the optical signal input via the direction control mechanism 107 in the desired direction. For example, the transmit / receive coupling unit 105 outputs the optical signal output from the optical signal transmission unit 102 to the direction control mechanism 107. For example, the transmit / receive coupling unit 105 outputs the optical signal input via the direction control mechanism 107 to the distribution unit 106.

[0006] The distribution unit 106 distributes the optical signal output from the transmit / receive coupling unit 105 to the optical signal receiving unit 103 and the optical signal center deviation detection unit 108 and outputs them. The direction control mechanism 107 adjusts the direction for free-space optical communication with the mobile body 250. For example, the direction control mechanism 107 adjusts the direction of the laser so that its directivity is directed in a direction that allows optical signals to be sent and received with the mobile body 250. The optical signal center deviation detection unit 108 detects the deviation (shift) between the receiving surface and the optical signal based on the optical signal distributed by the distribution unit 106. The direction adjustment amount calculation unit 109 calculates the adjustment amount for the direction control mechanism 107 based on the detected deviation. The direction control unit 110 controls the beam irradiation direction by outputting a control command to the direction control mechanism 107 based on the calculated adjustment amount.

[0007] The data processing unit 201 performs framing and signal processing on the data to be transmitted to the fixed station 150. The optical signal transmission unit 202 converts the output signal of the data processing unit 201 into an optical signal. The optical signal receiving unit 203 receives the optical signal transmitted from the fixed station 150 and converts the received optical signal into an electrical signal. The data acquisition unit 204 performs signal processing such as demodulation and decoding, as well as deframing, on the output of the optical signal receiving unit 203. The transmit / receive coupling unit 205 outputs the optical signal output from the optical signal transmission unit 202 and the optical signal input via the direction control mechanism 207 in the desired direction. For example, the transmit / receive coupling unit 205 outputs the optical signal output from the optical signal transmission unit 202 to the direction control mechanism 207. For example, the transmit / receive coupling unit 205 outputs the optical signal input via the direction control mechanism 207 to the distribution unit 206.

[0008] The distribution unit 206 distributes the optical signal output from the transmit / receive coupling unit 205 to the optical signal receiving unit 203 and the optical signal center deviation detection unit 208 and outputs them. The direction control mechanism 207 adjusts the direction for free-space optical communication with the fixed station 150. For example, the direction control mechanism 207 adjusts the direction of the laser so that its directivity is directed in a direction that allows optical signals to be sent and received with the fixed station 150. The optical signal center deviation detection unit 208 detects the deviation (shift) between the receiving surface and the optical signal based on the optical signal distributed by the distribution unit 206. The direction adjustment amount calculation unit 209 calculates the adjustment amount for the direction control mechanism 207 based on the detected deviation. The direction control unit 210 controls the beam irradiation direction by outputting a control command to the direction control mechanism 207 based on the calculated adjustment amount. The movement control information receiving unit 211 receives movement control information output from the mobile operation terminal 350. The mobile body control unit 212 controls the mobile body 250 based on the movement control information acquired by the movement control information receiving unit 211. For example, the mobile body control unit 212 moves the mobile body 250 in a specified direction based on the movement control information. [Prior art documents] [Non-patent literature]

[0009] [Non-Patent Document 1] Kosuke MORI, “Fast Handover Mechanism for High Data Rate Ground-to-Train Free-Space Optical Communication Transceiver for Internet Streaming Applications”, IEICE TRANS. COMMUN., VOL.E99-B, NO.5 MAY 2016. [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] In conventional technology, a mobile body 250 moves, and the beam shift associated with the movement of the mobile body 250 is detected by an optical signal received by the fixed station 150, thereby controlling the beam's irradiation direction. Figures 9 and 10 show an image of the control of the beam's irradiation direction. Figures 9 and 10 show an image of the control of the beam B's irradiation direction for each control cycle Δt of the direction control mechanism 107. Figure 9 shows an image of the control when the mobile body 250 is an object whose direction of movement cannot be predicted, and Figure 10 shows an image of the control when the mobile body 250 is an object whose direction of movement can be predicted. An object whose direction of movement cannot be predicted is, for example, a remotely controlled object such as a drone whose direction of movement is not determined. An object whose direction of movement can be predicted is, for example, an object such as a train or a satellite.

[0011] In Figure 9, at time t=0, the mobile object 250 is located within the range of beam B emitted by the fixed station 150, and communication via free-space optical communication is possible. Suppose the mobile object 250 moves to the right from its position at time t=0. In this case, at time t=Δt, the mobile object 250 moves to a position slightly outside the range of beam B emitted by the fixed station 150. The fixed station 150 detects the shift by receiving beam B emitted from the mobile object 250 and controls the direction of beam B after detecting the shift. However, if the mobile object 250 moves quickly, at time t=2Δt the mobile object 250 will move further to the right, and the tracking operation may not be able to keep up. As a result, communication may be interrupted.

[0012] On the other hand, in the case of a train, as in the conventional method, the direction and speed of movement are predetermined. Therefore, the movement information of the mobile body 250 (for example, direction and speed) can be used to control the direction of beam B of the fixed station 150. As a result, as shown in Figure 10, even if the mobile body 250 moves to the right at times t=Δt,2Δt, communication can be continued by pre-controlling the direction of beam B of the fixed station 150 to the direction in which the mobile body 250 is located at times t=Δt,2Δt.

[0013] However, in the case of a mobile object 250, such as a drone, the direction and speed of movement are not predetermined, unlike trains or satellites. Furthermore, when the direction and speed of movement change, there is a transition time between the original direction and speed and the specified direction and speed, but the information used to control the mobile object 250 does not include how the direction and speed of movement change during this transition time. Therefore, conventionally, it has been difficult to use movement information to control the irradiation direction of beam B for mobile objects whose movement path is not predetermined.

[0014] In view of the above circumstances, the present invention aims to provide a technology that allows movement information to be used to control the direction of beam irradiation in a moving object whose movement path is not predetermined. [Means for solving the problem]

[0015] One aspect of the present invention is a fixed station that performs free-space optical communication with a moving object whose movement path is not predetermined, comprising: a movement control information receiving unit that receives movement control information, which is information for moving the moving object to a specified position, transmitted from a moving object control terminal that controls the movement of the moving object; an adjustment amount calculation unit that calculates an adjustment amount for controlling the irradiation direction of a beam for each control period by predicting the change in the velocity of the moving object based on the movement control information received by the movement control information receiving unit; and a direction control unit that controls the irradiation direction of the beam for each control period based on the adjustment amount for each control period calculated by the adjustment amount calculation unit.

[0016] One aspect of the present invention is a mobile body that performs free-space optical communication with a fixed station and does not have a predetermined path of movement, comprising: a mobile control information receiving unit that receives mobile control information, which is information for moving the mobile body to a designated position, transmitted from a mobile body operation terminal that controls the operation of the mobile body; a mobile body control unit that controls the operation of the mobile body based on the mobile control information received by the mobile control information receiving unit; an adjustment amount calculation unit that calculates an adjustment amount for controlling the irradiation direction of a beam for each control period by predicting the change in the speed of the mobile body based on the mobile control information received by the mobile control information receiving unit; and a direction control unit that controls the irradiation direction of the beam for each control period based on the adjustment amount for each control period calculated by the adjustment amount calculation unit.

[0017] One aspect of the present invention is a communication system comprising a mobile body, a fixed station that performs free-space optical communication with the mobile body, and a mobile body control terminal that controls the operation of the mobile body, wherein the fixed station comprises a first mobile control information receiving unit that receives mobile control information transmitted from the mobile body control terminal, which is information for moving the mobile body to a specified position; an adjustment amount calculation unit that calculates an adjustment amount for controlling the irradiation direction of a beam for each control period by predicting the change in the speed of the mobile body based on the mobile control information received by the first mobile control information receiving unit; and a direction control unit that controls the irradiation direction of the beam for each control period based on the adjustment amount for each control period calculated by the adjustment amount calculation unit, wherein the mobile body comprises a second mobile control information receiving unit that receives the mobile control information transmitted from the mobile body control terminal, and a mobile body control unit that controls its operation based on the mobile control information received by the second mobile control information receiving unit.

[0018] One aspect of the present invention is to receive movement control information, which is information for moving a moving body to a designated position and is transmitted from a moving body control terminal that controls the operation of a moving body whose movement path is not predetermined in advance, and predict the speed change of the moving body based on the received movement control information. Then, an adjustment amount for controlling the irradiation direction of the beam is calculated for each control period, and based on the calculated adjustment amount for each control period, the irradiation direction of the beam is controlled for each control period. This is a beam direction control method.

Advantages of the Invention

[0019] According to the present invention, in a moving body whose movement path is not predetermined in advance, it becomes possible to use movement information for controlling the irradiation direction of the beam.

Brief Description of the Drawings

[0020] [Figure 1] It is a diagram showing a configuration example of a communication system in an embodiment. [Figure 2A] It is a diagram showing an example of movement control information received by a movement control information receiving unit in an embodiment. [Figure 2B] It is a diagram showing an example of movement control information received by a movement control information receiving unit in an embodiment. [Figure 3A] It is a diagram showing an example of speed change information in an embodiment. [Figure 3B] It is a diagram showing an example of speed change information in an embodiment. [Figure 4] It is an explanatory diagram regarding the speed change of a moving body in an embodiment. [Figure 5] It is a sequence diagram showing the flow of processing of a communication system in an embodiment. [Figure 6] It is a diagram showing an operation image when the beam irradiation direction control method in an embodiment is used. [Figure 7] It is a diagram showing speed change information when the beam irradiation direction control method in an embodiment is used. [Figure 8] It is a diagram showing a configuration example of a conventional communication system. [Figure 9] This diagram illustrates a control system for a moving object whose direction of movement cannot be predicted. [Figure 10] This diagram illustrates a control system for a moving object whose direction of movement can be predicted. [Modes for carrying out the invention]

[0021] One embodiment of the present invention will be described below with reference to the drawings. Figure 1 shows an example configuration of a communication system 10 in an embodiment. The communication system 10 comprises a fixed station 100, a mobile unit 200, and a mobile unit control terminal 300. Figure 1 shows a case where there is one fixed station 100, one mobile unit 200, and one mobile unit control terminal 300, but the number of fixed stations 100, mobile units 200, and mobile unit control terminals 300 may be two or more. Communication between the fixed station 100 and the mobile unit 200 is performed by free-space optical communication. Communication between the mobile unit 200 and the mobile unit control terminal 300, and communication between the fixed station 100 and the mobile unit control terminal 300, is performed using radio waves or visible light including infrared light, etc.

[0022] The fixed station 100 performs free-space optical communication with the mobile body 200 by controlling the irradiation direction of beam B. The fixed station 100 transmits beam B to the mobile body 200 or receives beam B transmitted from the mobile body 200. Furthermore, the fixed station 100 receives movement control information transmitted from the mobile body control terminal 300. The movement control information is information for moving the mobile body 200 to a specified position and includes at least one piece of information such as orientation (direction) or magnitude (speed). The fixed station 100 is, for example, a communication device whose installation location is fixed in advance.

[0023] The mobile unit 200 performs free-space optical communication with the fixed station 100 by controlling the direction of beam B. The mobile unit 200 is, for example, a remotely controlled unmanned flying object such as a drone. The mobile unit 200 can freely change its direction of movement by user control and can be any object as long as its movement path is not predetermined, such as a train or satellite. The mobile unit 200 transmits beam B to the fixed station 100 or receives beam B transmitted from the fixed station 100. Furthermore, the mobile unit 200 moves in the direction specified by the movement control information transmitted from the mobile unit control terminal 300. If the movement control information includes speed information, the mobile unit 200 moves at the speed specified in the movement control information.

[0024] The mobile control terminal 300 controls the movement of the mobile unit 200. The mobile control terminal 300 transmits movement control information, including information for instructing the direction and speed of movement of the mobile unit 200, to the fixed station 100 and the mobile unit 200. The mobile control terminal 300 is operated by the user.

[0025] Next, the specific configurations of the fixed station 100 and the mobile unit 200 will be described. First, the functional configuration of the fixed station 100 will be described. The fixed station 100 comprises a data processing unit 101, an optical signal transmission unit 102, an optical signal reception unit 103, a data acquisition unit 104, a transmission / reception coupling unit 105, a distribution unit 106, a direction control mechanism 107, an optical signal center deviation detection unit 108, a direction adjustment amount calculation unit 109, a direction control unit 110, a mobile control information reception unit 111, an adjustment amount calculation unit 112, and a flight database 113.

[0026] The data processing unit 101, optical signal transmission unit 102, optical signal reception unit 103, data acquisition unit 104, transmission / reception coupling unit 105, distribution unit 106, direction control mechanism 107, optical signal center deviation detection unit 108, direction adjustment amount calculation unit 109, and direction control unit 110 of the fixed station 100 perform the same processing as the functional units of the same name that are provided in the fixed station 150 shown in Figure 8. The following explanation will focus on the differences with the fixed station 150.

[0027] The mobile control information receiving unit 111 receives mobile control information transmitted from the mobile vehicle control terminal 300. When the mobile vehicle control terminal 300 controls the mobile vehicle 200 via wireless communication, the mobile control information receiving unit 111 of the fixed station 100 has the same configuration as the mobile control information receiving unit 211 of the mobile vehicle 200 that can receive that wireless communication. The mobile control information receiving unit 111 is one embodiment of the first mobile control information receiving unit.

[0028] Figures 2A and 2B show examples of movement control information received by the movement control information receiving unit in the embodiment. In Figure 2A, it is assumed that after the mobile body control terminal 300 transmits movement control information (for example, speed -V2) once, the mobile body 200 continues to move in the instructed direction at speed -V2, and when the speed of the mobile body 200 is changed, the movement control information is transmitted again at that time.

[0029] On the other hand, Figure 2B assumes that the mobile control terminal 300 continues to transmit movement control information, and that the mobile unit 200 moves in accordance with each instruction in the movement control information.

[0030] Returning to Figure 1, the explanation continues. The adjustment amount calculation unit 112 calculates the adjustment amount based on the movement control information received by the movement control information receiving unit 111 and the past flight data of the mobile body 200 stored in the flight database 113. The adjustment amount calculated by the adjustment amount calculation unit 112 is an adjustment amount for controlling the irradiation direction of beam B. For example, the adjustment amount includes a value that indicates how much the irradiation direction of beam B will be changed by an angle.

[0031] The flight database 113 is a database in which information representing the change in speed during the transition time (hereinafter referred to as "speed change information") is registered for each pre-change speed and post-change speed. For example, the flight database 113 contains speed change information that shows how the speed changes from the first speed to the second speed during the transition time, and this information is registered for each pre-change speed and post-change speed.

[0032] Figures 3A and 3B show examples of velocity change information in the embodiment. Even with the same moving body 200, the transition time and the velocity change during the transition time are thought to depend on two factors: the moving velocity before the change and the moving velocity after the change. The moving velocity before the change can be estimated from past movement control information or the adjustment amount within the current control cycle.

[0033] The change in velocity during the transition time from the initial velocity (e.g., velocity V1) to the final velocity (e.g., velocity -V2) is considered to differ for each moving object 200, as shown in Figures 3A and 3B. One way to determine the change in velocity during the transition time based on the initial and final velocity is to acquire past flight data of the moving object 200 in advance. From the past flight data, velocity change information during the transition time is obtained for each combination of initial and final velocity, and this acquired velocity change information is registered in the flight database 113. By repeating this process, the flight database 113 is registered with velocity change information during the transition time for each combination of initial and final velocity.

[0034] When movement control information is acquired during communication between the fixed station 100 and the mobile unit 200, the adjustment amount calculation unit 112 refers to the flight database 113 and acquires speed change information within the transition time corresponding to the combination of the current movement speed of the mobile unit 200 and the movement speed instructed by the movement control information. Here, the current movement speed of the mobile unit 200 is the movement speed before the change, and the movement speed instructed by the movement control information is the movement speed after the change. The adjustment amount calculation unit 112 calculates the adjustment amount for each control period Δt by referring to the acquired speed change information.

[0035] Furthermore, if the number of velocity change information entries registered in the flight database 113 is small, it is conceivable that there may be no velocity change information within the transition time corresponding to the combination of the current movement speed of the mobile body 200 and the movement speed instructed by the movement control information. In this case, if the adjustment amount calculation unit 112 does not have velocity change information within the transition time corresponding to the combination of the current movement speed of the mobile body 200 and the movement speed instructed by the movement control information registered in the flight database 113, it should acquire velocity change information within the transition time corresponding to a combination that is close to the one in question. In this way, the adjustment amount calculation unit 112 calculates an adjustment amount for controlling the irradiation direction of beam B for each control cycle by predicting the velocity change of the mobile body 200 based on the movement control information.

[0036] The direction control unit 110 controls the irradiation direction of beam B by outputting a control command to the direction control mechanism 107 based on the adjustment amount calculated by the direction adjustment amount calculation unit 109 or the adjustment amount calculation unit 112. Specifically, when the direction control unit 110 receives movement control information transmitted from the mobile operation terminal 300, it controls the irradiation direction of beam B by outputting a control command to the direction control mechanism 107 based on the adjustment amount calculated by the adjustment amount calculation unit 112. When movement control information has not been received, the direction control unit 110 controls the irradiation direction of beam B by outputting a control command to the direction control mechanism 107 based on the adjustment amount calculated by the direction adjustment amount calculation unit 109.

[0037] Figure 4 is an explanatory diagram regarding the velocity change of the mobile body 200 in the embodiment. As shown in Figure 4, the direction of propagation of the beam B irradiated from the fixed station 100 is defined as the z direction, and the horizontal plane relative to the z direction is defined as the xy plane. Since the fixed station 100 does not need to control the direction of the mobile body 200's movement in the z direction, the movement in the z direction will not be considered from now on. The x and y directions can be considered independently. That is, the directional change of the mobile body 200 can be replaced by a combination of velocity changes in the x or y direction. For this reason, the following explanation will consider only the velocity change in the x direction.

[0038] Next, the specific operation of the adjustment amount calculation unit 112 will be explained. For each control period Δt of the direction control mechanism 107, the adjustment amount calculation unit 112 calculates the adjustment amount for the irradiation direction of beam B. As mentioned above, if only movement in the x direction is assumed, and the amount of movement of the mobile body 200 between the control period Δt of the direction control mechanism 107 is a, and the communication distance between the fixed station 100 and the mobile body 200 is z, the adjustment amount calculation unit 112 calculates the angle to be adjusted as the adjustment amount using tan(a / z).

[0039] The amount of displacement a is equal to the velocity V. t The integral of (a=∫V t This can be calculated using dt). Here, the range of integration is the period from the time the adjustment amount is calculated (hereinafter referred to as "calculation time") to calculation time + Δt. Velocity V t This represents the velocity at time t within the integration range. When the velocity change per control period Δt is small, the displacement a can be simply calculated as a = Δt × v. Here, velocity v can be either the velocity at the current time or the velocity expected after the control period Δt.

[0040] If the movement control information includes information on the movement speed, the optical signal center deviation detection unit 108 may be configured to predict the amount of movement of the moving body 200, i.e., the amount of deviation of the optical signal, based on the information on the movement speed.

[0041] Next, the functional configuration of the mobile unit 200 will be described. The mobile unit 200 comprises a data processing unit 201, an optical signal transmission unit 202, an optical signal reception unit 203, a data acquisition unit 204, a transmission / reception coupling unit 205, a distribution unit 206, a direction control mechanism 207, an optical signal center deviation detection unit 208, a direction adjustment amount calculation unit 209, a direction control unit 210, a movement control information reception unit 211, and a mobile unit control unit 212. Each functional unit of the mobile unit 200 performs the same processing as the functional units of the same name in the mobile unit 250 shown in Figure 8. Here, the movement control information reception unit 211 is one embodiment of the second movement control information reception unit.

[0042] The mobile body control unit 212 may acquire information on the mobile body 200's movement speed in real time and transmit it to the direction adjustment amount calculation unit 209. If the movement control information includes information on the movement speed, the optical signal center deviation detection unit 208 may be configured to predict the amount of movement of the mobile body 200, i.e., the amount of deviation of the optical signal, based on the information on the movement speed.

[0043] Figure 5 is a sequence diagram showing the processing flow of the communication system 10 in the embodiment. The mobile unit control terminal 300 transmits mobile control information corresponding to the instructions input by the user to the fixed station 100 and the mobile unit 200 (step S101). The mobile unit 200's mobile control information receiving unit 211 receives the mobile control information transmitted from the mobile unit control terminal 300. The mobile control information receiving unit 211 outputs the received mobile control information to the mobile unit control unit 212. The mobile unit control unit 212 controls the operation of the mobile unit 200 based on the mobile control information output from the mobile control information receiving unit 211 (step S102).

[0044] Specifically, if the direction to be moved is specified in the movement control information, the movement control unit 212 controls the movement of the mobile body 200 to move in the direction specified in the movement control information. If the movement speed is specified in the movement control information, the movement control unit 212 controls the movement of the mobile body 200 to move at the speed specified in the movement control information. If both the direction to be moved and the movement speed are specified in the movement control information, the movement control unit 212 controls the movement of the mobile body 200 to move in the direction specified in the movement control information at the specified speed. As a result, the mobile body 200 moves.

[0045] The mobile control information receiving unit 111 of the fixed station 100 receives mobile control information transmitted from the mobile piloting terminal 300 (step S103). The mobile control information receiving unit 111 outputs the received mobile control information to the adjustment amount calculation unit 112. The adjustment amount calculation unit 112 calculates the adjustment amount based on the mobile control information output from the mobile control information receiving unit 111 and the flight database 113 (step S104).

[0046] Specifically, the adjustment amount calculation unit 112 refers to the flight database 113 and obtains velocity change information corresponding to the combination of the movement speed specified in the movement control information and the current movement speed of the moving object 200. Next, the adjustment amount calculation unit 112 calculates the amount of movement a for each Δt interval in the obtained velocity change information. For example, the adjustment amount calculation unit 112 calculates the amount of movement a for each Δt interval in the velocity change information from the current movement speed of the moving object 200 to the movement speed specified in the movement control information, such as the amount of movement a1 between Δt and 2Δt, the amount of movement a2 between 2Δt and 3Δt, and so on.

[0047] The adjustment amount calculation unit 112 calculates the adjustment amount based on the calculated travel amount a and the communication distance z between the fixed station 100 and the mobile unit 200. For example, the adjustment amount calculation unit 112 calculates the adjustment amount based on the travel amount a1 and the communication distance z1. Similarly, the adjustment amount calculation unit 112 calculates the adjustment amount based on the travel amount a2 and the communication distance z2. In this way, the travel amount a and the communication distance z change every Δt. The adjustment amount calculation unit 112 calculates the adjustment amount every Δt by repeating this process.

[0048] If only the direction is specified in the movement control information, the mobile body 200 will move at the same speed as its current speed. In this case, the speed of the mobile body 200 does not change. If the speed of the mobile body 200 does not change, the amount of movement a for each Δt interval is the same. That is, the adjustment amount calculation unit 112 calculates the amount of movement a for each Δt interval based on the current speed of the mobile body 200. The adjustment amount calculation unit 112 calculates the adjustment amount based on the calculated amount of movement a and the communication distance z between the fixed station 100 and the mobile body 200.

[0049] The adjustment amount calculation unit 112 outputs the calculated adjustment amount information to the direction control unit 110. The direction control unit 110 controls the irradiation direction of beam B by outputting a control command to the direction control mechanism 107 based on the adjustment amount information output from the adjustment amount calculation unit 112 (step S105). Within the transition time, the direction control unit 110 controls the irradiation direction of beam B by outputting the adjustment amount information as a control command to the direction control mechanism 107 at each control period Δt. This enables free-space optical communication between the fixed station 100 and the mobile unit 200 (step S106).

[0050] Figure 6 shows an image of the operation when using the control method for the irradiation direction of beam B in the embodiment. Figure 7 shows velocity change information when using the control method for the irradiation direction of beam B in the embodiment. In Figure 6, at time t=0, the mobile body 200 is located within the range of beam B irradiated by the fixed station 100, and communication by free-space optical communication is possible. Assume that the mobile body 200 moves to the right from the position at time t=0 at time t=Δt according to the movement control information transmitted from the mobile body control terminal 300. In this case, the fixed station 100 also receives the movement control information transmitted from the mobile body control terminal 300. Based on the received movement control information, the fixed station 100 calculates an adjustment amount as described above, and controls the irradiation direction of beam B based on the adjustment amount, thereby irradiating beam B in the direction in which the mobile body 200 is located at time t=Δt.

[0051] Even when time t has elapsed as 2Δt, 3Δt, 4Δt, 5Δt, and 6Δt, the fixed station 100 can follow the moving body 200 by controlling the irradiation direction of beam B at each control cycle Δt based on the movement control information.

[0052] With the communication system 10 configured as described above, in the case of a mobile body whose movement path is not predetermined, movement information can be used to control the irradiation direction of beam B. Specifically, the fixed station 100 includes a movement control information receiving unit 111 that receives movement control information transmitted from the mobile body operation terminal 300, an adjustment amount calculation unit 112 that calculates an adjustment amount for controlling the irradiation direction of beam B for each control cycle by predicting the change in speed of the mobile body 200 based on the movement control information received by the movement control information receiving unit 111, and a direction control unit 110 that controls the irradiation direction of beam B for each control cycle based on the adjustment amount for each control cycle calculated by the adjustment amount calculation unit 112. The mobile body 200 includes a movement control information receiving unit 211 that receives movement control information transmitted from the mobile body operation terminal 300, and a mobile body control unit 212 that controls its operation based on the movement control information received by the movement control information receiving unit 211. This allows the fixed station 100 to understand the change in the mobile body's speed even when the mobile body's speed changes in real time based on instructions from the mobile body control terminal 300. Therefore, the fixed station 100 can control the direction of beam B based on the information it has received about the change in the mobile body's speed. Consequently, for mobile bodies whose movement path is not predetermined, the movement information can be used to control the direction of beam B.

[0053] The optical signal center deviation detection units 108 and 208 transmit information (deviation information) obtained after the moving body 200 has started moving to the direction adjustment amount calculation units 109 and 209. If the movement control information includes information on the movement speed, it is possible to predict the amount of movement of the moving body 200 in the future, i.e., the amount of deviation of the optical signal, so faster control of the irradiation direction of beam B can be expected.

[0054] (Variation 1) In the embodiment described above, a configuration was shown in which speed change information for each combination of the moving speed before the change and the moving speed after the change is pre-registered in the flight database 113. In contrast, when the moving object 200 moves with a change in speed, the speed information of the moving object 200 may be recorded, and the speed change information within the transition time registered in the flight database 113 may be updated and added. Alternatively, machine learning may be used on the fixed station 100 side to estimate the transition time and speed change.

[0055] (Modification 2) The mobile unit 200 may acquire information on its movement speed in real time via the mobile unit control unit 212 and transmit it to the direction adjustment amount calculation unit 209 for control. Alternatively, the mobile unit 200 may be configured to have an adjustment amount calculation unit with the same functionality as the adjustment amount calculation unit 112 of the fixed station 100, between the movement control information receiving unit 211 and the direction control unit 210, and to calculate the adjustment amount in the same way as the adjustment amount calculation unit 112. In this configuration, the mobile unit 200 further includes a flight database 113. The direction control unit 210 of the mobile unit 200 controls the irradiation direction of beam B by outputting a control command to the direction control mechanism 207 based on the adjustment amount calculated by the direction adjustment amount calculation unit 209 or the adjustment amount calculation unit. Specifically, when the direction control unit 210 receives movement control information transmitted from the mobile unit operation terminal 300, it controls the irradiation direction of beam B by outputting a control command to the direction control mechanism 207 based on the adjustment amount calculated by the adjustment amount calculation unit. If no movement control information is received, the direction control unit 210 controls the irradiation direction of beam B by outputting a control command to the direction control mechanism 207 based on the adjustment amount calculated by the direction adjustment amount calculation unit 209.

[0056] With this configuration, the irradiation direction of beam B can be automatically controlled even in the mobile unit 200.

[0057] In the above-described embodiment, some of the functional parts of the fixed station 100 and mobile unit 200 may be implemented using a computer. In that case, the program for implementing this function may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be loaded into a computer system and executed. The term "computer system" as used herein includes hardware such as an OS (Operating System) and peripheral devices.

[0058] Furthermore, "computer-readable recording media" refers to portable media such as flexible disks, magneto-optical disks, ROMs (Read Only Memory), and CD-ROMs, as well as storage devices such as hard disks built into computer systems. In addition, "computer-readable recording media" may also include those that dynamically hold programs for a short period of time, such as communication lines used when transmitting programs over networks such as the Internet or communication lines such as telephone lines, and those that hold programs for a certain period of time, such as volatile memory inside computer systems that act as servers or clients in such cases. Moreover, the above-mentioned programs may be for the purpose of realizing some of the functions described above, or they may be able to realize the above-mentioned functions in combination with programs already recorded in the computer system, or they may be realized using programmable logic devices such as FPGAs (Field Programmable Gate Arrays).

[0059] Although embodiments of this invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and includes designs and the like that do not depart from the spirit of this invention. [Industrial applicability]

[0060] This invention is applicable to optical spatial communication systems. [Explanation of Symbols]

[0061] 10…Communication system, 100…Fixed station, 101, 201…Data processing unit, 102, 202…Optical signal transmission unit, 103, 203…Optical signal reception unit, 104, 204…Data acquisition unit, 105, 205…Transmit / receive coupling unit, 106, 206…Distribution unit, 107, 207…Direction control mechanism, 108, 208…Optical signal center deviation detection unit, 109, 209…Direction adjustment amount calculation unit, 110, 210…Direction control unit, 111, 211…Movement control information reception unit, 112…Adjustment amount calculation unit, 113…Flight database, 212…Mobile unit control unit

Claims

1. A fixed station that performs free-space optical communication with a mobile object whose movement path is not predetermined, A movement control information receiving unit receives movement control information, which is information for moving the mobile body to a specified position, transmitted from a mobile body control terminal that controls the movement of the mobile body. An adjustment amount calculation unit predicts the change in the speed of the moving body based on the movement control information received by the movement control information receiving unit, and calculates an adjustment amount for controlling the beam irradiation direction at each control cycle using the predicted change in the speed of the moving body and the movement control information, A direction control unit controls the irradiation direction of the beam for each control cycle based on the adjustment amount for each control cycle calculated by the adjustment amount calculation unit, A fixed station equipped with this feature.

2. The aforementioned movement control information includes at least one piece of information regarding direction or velocity. If the movement control information includes information about speed, the adjustment amount calculation unit calculates the amount of movement of the moving body for each control cycle using speed change information that represents the transition of speed change during the transition time from the speed of the moving body before the change to the speed included in the movement control information, and calculates the adjustment amount for each control cycle based on the calculated amount of movement of the moving body for each control cycle and the communication distance. A fixed station according to claim 1.

3. The aforementioned movement control information includes at least one piece of information regarding direction or velocity. If the movement control information includes information about direction, the adjustment amount calculation unit calculates the amount of movement of the moving body for each control cycle based on the speed of the moving body, and calculates the adjustment amount for each control cycle based on the calculated amount of movement of the moving body for each control cycle and the communication distance. A fixed station according to claim 1.

4. A mobile entity that performs free-space optical communication with a fixed station and whose movement path is not predetermined, A movement control information receiving unit receives movement control information, which is information for moving the mobile body to a specified position, transmitted from a mobile body control terminal that controls the movement of the mobile body. A mobile body control unit controls the movement of the mobile body based on the movement control information received by the movement control information receiving unit, An adjustment amount calculation unit predicts the change in the speed of the moving body based on the movement control information received by the movement control information receiving unit, and calculates an adjustment amount for controlling the beam irradiation direction at each control cycle using the predicted change in the speed of the moving body and the movement control information, A direction control unit controls the irradiation direction of the beam for each control cycle based on the adjustment amount for each control cycle calculated by the adjustment amount calculation unit, A mobile device equipped with [the following features].

5. The aforementioned movement control information includes at least one piece of information regarding direction or velocity. If the movement control information includes information about speed, the adjustment amount calculation unit calculates the amount of movement of the moving body for each control cycle using speed change information that represents the transition of speed change during the transition time from the speed of the moving body before the change to the speed included in the movement control information, and calculates the adjustment amount for each control cycle based on the calculated amount of movement of the moving body for each control cycle and the communication distance. The mobile body according to claim 4.

6. The aforementioned movement control information includes at least one piece of information regarding direction or velocity. If the movement control information includes information about direction, the adjustment amount calculation unit calculates the amount of movement of the moving body for each control cycle based on the speed of the moving body, and calculates the adjustment amount for each control cycle based on the calculated amount of movement of the moving body for each control cycle and the communication distance. The mobile body according to claim 4.

7. A communication system comprising a mobile body whose movement path is not predetermined, a fixed station that performs free-space optical communication with the mobile body, and a mobile body control terminal that controls the movement of the mobile body, The aforementioned fixed station is A first movement control information receiving unit receives movement control information, which is information for moving the mobile object to a specified position, transmitted from the mobile object control terminal. A first motion control information receiving unit predicts the change in the velocity of the moving body based on the motion control information received by the first motion control information receiving unit, and an adjustment amount calculation unit calculates an adjustment amount for controlling the beam irradiation direction at each control cycle using the predicted change in the velocity of the moving body and the motion control information, A direction control unit controls the irradiation direction of the beam for each control cycle based on the adjustment amount for each control cycle calculated by the adjustment amount calculation unit, Equipped with, The aforementioned moving body is A second mobile control information receiving unit that receives the mobile control information transmitted from the mobile device control terminal, A mobile body control unit controls the operation based on the movement control information received by the second movement control information receiving unit, A communication system equipped with [the following features].

8. The system receives movement control information, which is information for moving a mobile object to a designated position, transmitted from a mobile object control terminal that controls the movement of a mobile object whose movement path is not predetermined. Based on the received motion control information, the change in the velocity of the moving body is predicted, and using the predicted change in the velocity of the moving body and the motion control information, an adjustment amount for controlling the beam irradiation direction is calculated for each control cycle. A beam direction control method that controls the irradiation direction of the beam at each control cycle based on the adjustment amount calculated for each control cycle.

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