JP2018174412A - Tracking antenna system and tracking antenna device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tracking antenna system capable of executing efficient and stable handover in tracking a plurality of aircrafts by a plurality of ground stations.SOLUTION: The tracking antenna system dynamically controls a direction in which a plurality of ground station antennas 10 and a ground station 200 to which each unmanned aircraft 100 connects by using position and attitude information of the moving unmanned aircraft 100, signal strength information, antenna directivity information and such. The tracking antenna system predicts reception power intensity at a plurality of times after a start of a current control cycle is started from prediction of a movement route of an unmanned aircraft and determines an unmanned aircraft 100 to be tracked by each ground station 200 in accordance with a prediction result at a time when the reception power intensity becomes the minimum.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a tracking antenna device and a tracking antenna system for tracking a flying object.

  In the event of a disaster such as an earthquake or fire, as a first response by a private news agency or government agency, the site was shot with a camera mounted on an unmanned aerial vehicle (UAV) or unmanned helicopter (photographing helicopter) There is a case where a technique is adopted in which captured video information is quickly transmitted to the ground station in real time. Since such video information is important information that becomes a determination source for initial response, it is required to transmit the video information without interruption at any time.

  In particular, the operation of multiple aircraft is indispensable for observing a wide area in real time with high accuracy. Broadband transmission of not only flight status and avionics equipment but also mission equipment information to the ground in real time and necessary commands on the ground. A more transmitting communication system is essential. Since such a system needs to be able to operate even when a public communication system such as a mobile phone cannot be used due to a large-scale disaster or the like, the communication system is inevitably a self-supporting system. In addition, due to the scale of the building to be inspected and monitored, the communicable area needs to cover about 1 km square.

  In Patent Document 1, the position of an unmanned aerial vehicle is detected by GPS every fixed time, and the directional antenna is an unmanned aerial vehicle based on information on two positions of the unmanned aircraft at two points in time and the positional information of the directional antenna. A configuration is disclosed in which the amount of rotation of the antenna motor necessary for tracking is calculated by a notebook personal computer, and the antenna motor is controlled by the antenna controller in accordance with the calculated amount of rotation.

  In the technique disclosed in Patent Document 1, when one UAV tracks one UAV, the tracking direction of the antenna is determined from the latest position information of the UAV and the tracking antenna.

  On the other hand, in Non-Patent Document 1, in order to apply the millimeter wave band to the radio communication of a high-speed moving body such as an aircraft, the performance of the antenna that realizes the long-distance millimeter wave band communication is increased. Have disclosed an antenna control technique for controlling the radiation direction of radio waves at high speed following the attitude of an aircraft, and a network technique suitable for mobile communication using the millimeter wave band.

  The technique of Non-Patent Document 1 is configured such that handover is executed based on the route prediction of one aircraft, and the movement of the aircraft is predicted and the tracking antenna of the handover source and the handover destination track.

JP 2001-267829 A

http://www.nict.go.jp/press/2010/06/23-1.html, “Development of Aircraft-Ground Wireless Communication System Using Millimeter Wave”, Information and Communications Research, Incorporated Administrative Agency Organization Press Release June 23, 2010

  At present, a frequency band of 6 MHz per channel in the 1.2 GHz band is allocated to a wireless communication system for image transmission for industrial unmanned aerial vehicles and unmanned helicopter television relays (Heli Tele). However, there is insufficient bandwidth to perform broadband real-time moving image transmission having a bit rate of about 8 to 10 Mb / s per stream using a plurality of UAVs.

  For this reason, a wireless LAN (Local Area Network) represented by IEEE802.11g / n is the most promising for realizing such transmission in a private system. However, the transmission distance of a general wireless LAN device is about 100 m at most. Therefore, a large number of ground stations (BS) are required to stably secure sufficient received power for a plurality of UAVs that circulate around a large building.

  As a method of covering the flight area of the UAV in a small number of ground stations, it is conceivable to extend the transmittable distance by tracking the UAV using a high-gain tracking antenna. However, if the relationship between each UAV and the ground station tracking antenna that tracks it is fixed one-to-one, the action range of the UAV is greatly restricted by the distance from the ground station and the line-of-sight range, and the same channel interference with other ground stations The degree of freedom of the workaround when this occurs is also limited.

  For this reason, it is necessary to track a plurality of UAVs with a plurality of tracking antennas that are distant from each other. At this time, a plurality of UAVs moving at several tens to 100 km / h are captured by the tracking antenna of the ground station so that the required received power can be secured.

  However, the techniques disclosed in Patent Document 1 and Non-Patent Document 1 do not assume tracking of a plurality of UAVs existing in the same area.

  Also, if there is a sudden change in the tracking direction at the time of handover, the time during which the required received power cannot be secured may become longer.

  In addition, it is necessary to take measures against dead spots caused by the buildings to be monitored. In addition to securing a communicable range by arranging a plurality of ground stations apart from each other, depending on the flight position of the UAV It is necessary to appropriately switch (handover) the communication destination ground station. In particular, it is necessary to cope with the overtaking and difference of UAV.

  In addition, if the UAV position fluctuation is so large that it cannot be ignored during the control interval, there is a problem that the desired reception power cannot be obtained because the beam range from the ground station is not obtained and the control may become unstable. Alternatively, when the beam pattern has irregularities, there is a problem that the received power fluctuates by passing through the irregularities due to the movement of the UAV, and the desired received power may not be obtained.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a plurality of flight by a plurality of ground stations in a configuration in which a signal from a flying object is received while being tracked by the ground station. To provide a tracking antenna system and a tracking antenna device capable of performing an efficient and stable handover in tracking of a body.

  According to one aspect of the present invention, a tracking antenna system includes a plurality of flying bodies, and each of the plurality of flying bodies transmits and receives radio signals to and from positioning means for grasping its own position, speed, and posture. A plurality of ground stations for performing wireless communication with a plurality of flying bodies, each of the plurality of ground stations includes a tracking antenna capable of changing communication directivity, and tracking control In response to the instruction, directivity control means for driving the communication directivity of the tracking antenna in the direction of the corresponding flying object among the plurality of flying objects, and signal strength measuring means for measuring the received signal intensity from the flying object. The tracking antenna is capable of setting the first and second tracking targets from among a plurality of flying objects, selecting a flying object to which each of the plurality of ground stations is connected, and a plurality of ground stations Controls communication directivity A control station for generating a tracking control instruction for the vehicle, and the control station estimates the position of the flying object at a plurality of times based on information on the position, speed, and posture of each flying object. Based on the means, information on the estimated position of the flying object and the received signal strength, each ground station estimates the propagation loss at each time for the flying object, and based on the estimated propagation loss, A reception power prediction unit that predicts reception power at a plurality of times; a tracking direction control unit that determines a tracking direction according to a case where the reception situation is predicted to be worst based on the predicted reception power at a plurality of times; In a ground station that is communicating for a specific set of bodies, if the flying object is approaching a ground station other than the currently communicating ground station that is not performing communication or handover processing, A second tracking target upper station, to apply a projectile which substitution is predicted, and a ground station alternation control means for outputting a tracking control signal to the ground station.

  Preferably, the handover process is executed at a predetermined time interval, and the plurality of times are a first time after a process delay of the current handover control and a second time after a process delay of the next handover control. Including.

  Preferably, the plurality of times includes a third time between the first time and the second time.

According to another aspect of the present invention, there is a tracking antenna device for tracking a plurality of flying objects for wireless communication, and each of the plurality of flying objects grasps its own position, speed, and posture. A tracking antenna capable of changing communication directivity, a signal strength measuring means for measuring the received signal strength from the flying object, and a plurality of flying objects. Directivity control means for driving communication directivity in the direction of the corresponding flying object, and the tracking antenna can set the first and second tracking targets from among the plurality of flying objects. The directivity control means includes a flying object position estimating means for estimating the position of the flying object at a plurality of times based on the information on the position, speed, and posture of each flying object, and the reception and reception of the estimated positions of the flying object. Signal strength information and Each ground station estimates the propagation loss at each time for the flying object, and based on the estimated propagation loss, the received power prediction means for predicting the received power at multiple times, and at the predicted multiple times Based on the received power, the flying object is currently communicating with the tracking direction control means that determines the tracking direction according to the case where the reception situation is predicted to be the worst, and the ground station that is communicating with a specific set of flying objects. When a ground station other than the above ground station is approaching a ground station that is not performing communication or handover processing, a projectile predicted to be replaced is added to the second tracking target of the replacement ground station. Ground station switching control means for outputting a tracking control signal to the ground station.

  According to the tracking antenna system and the tracking antenna apparatus of the present invention, it is possible to execute an efficient and stable handover in tracking a plurality of flying objects by a plurality of ground stations.

It is a conceptual diagram which shows the structure of the radio | wireless communications system containing the tracking antenna apparatus of this Embodiment. It is a functional block diagram for demonstrating the structure of the unmanned aircraft 100 of this Embodiment. 3 is a functional block diagram for explaining a configuration of a system server 300. FIG. It is a figure for demonstrating the concept of the process of the ground station 200 and the system server 300 at the time of tracking the unmanned aircraft 100.1 and 100.2. It is a conceptual diagram for demonstrating the 1st subject in the case of performing the tracking process with respect to the unmanned aircraft 100 based on the estimation of the position of the unmanned aircraft. It is a conceptual diagram for demonstrating the 2nd subject in the case of performing the tracking process with respect to the unmanned aircraft 100 based on the estimation of the position of the unmanned aircraft. It is a conceptual diagram for demonstrating several time used as the object of a prediction process in this Embodiment. 4 is a flowchart for explaining a processing flow of the wireless aircraft 100, the ground station 200, and the system server 300. 10 is a flowchart for explaining tracking object update processing and antenna tracking direction update processing for UAV by system server 300. It is a flowchart for demonstrating the process which estimates the position and propagation loss of each UAV. 6 is a conceptual diagram for explaining a state of condition 1. FIG. It is a flowchart for demonstrating the algorithm which performs tracking direction control with respect to two UAV. FIG. 6 is a conceptual diagram showing expected received power in case A. FIG. 6 is a conceptual diagram showing expected received power in case B. FIG. 6 is a conceptual diagram showing expected received power in case C.

  Hereinafter, a radio communication system including a tracking antenna apparatus according to an embodiment of the present invention will be described with reference to the drawings. In the following embodiments, components and processing steps given the same reference numerals are the same or equivalent, and the description thereof will not be repeated unless necessary.

  In the following description, although not particularly limited, for example, a mobile station that is a flying object will be described as an unmanned aerial vehicle (UAV). However, for example, an unmanned helicopter or a drone may be used.

  As will be described below, the wireless communication system according to the present embodiment is a broadband wireless communication system that enables simultaneous observation by a plurality of UAVs. More specifically, using the position / velocity / attitude information, signal strength information, antenna directivity information, etc. of the moving UAV, the tracking direction of the plurality of ground station antennas, the ground station to which each UAV is connected, and each Dynamically control the channel used for the communication link.

To achieve a stable handover, each tracking antenna tracks a plurality of, for example, two UAVs (referred to as “first tracking target” and “second tracking target”) as much as possible. At this time, by suppressing the fluctuation in the tracking direction, the time during which the desired received power falls below the predetermined value is reduced. As a result, efficient handover is realized, and stable reception power required for each UAV is realized.
[Embodiment]
FIG. 1 is a conceptual diagram showing a configuration of a wireless communication system including a tracking antenna device of the present embodiment.

  The system includes a plurality of ground stations 200.1 to 200. M (hereinafter collectively referred to as “ground station 200”), and a plurality of unmanned aircraft 100.1 to 100.2 (hereinafter collectively referred to as “unmanned”) that transmits application data to the ground station 200. And the system server 300 that performs antenna control of each ground station / UAV in a centralized manner.

  When a large-scale disaster or accident occurs, it is necessary to capture and obtain information on the area as widely as possible in real time. In this case, it is necessary to receive images taken by a plurality of unmanned aerial vehicles 100.1 to 100.2 on the ground. For this reason, a transmission necessary for high-speed transmission using a plurality of tracking antennas for one unmanned aerial vehicle. A wireless communication link capable of securing the speed is secured.

  As will be described later, each unmanned aerial vehicle 100.1-100.2 is equipped with a GPS (global positioning system) hybrid inertial navigation device, and the position, speed, attitude angle of unmanned aircraft 100.1-100.2, and Measure telemetry data such as posture speeds. Here, each measured telemetry data is transmitted to the ground station 200 using a radio communication device for telemetry data transmission. Moreover, although it does not specifically limit to unmanned aerial vehicle 100.1-100.2, For example, a some directional antenna is mounted. In that case, an antenna to be used is selected based on a command from the system server 300.

  In the following, for the sake of simplicity of explanation, it is assumed that there are two unmanned aircraft, but the number may be larger.

  In FIG. 1, the ground stations 200.1 to 200. M has a tracking antenna device and can direct the antenna in the direction of unmanned aerial vehicles 100.1 to 100.2. Ground stations 200.1-200. M is the corresponding directional antenna 10.1-10. It is assumed that wireless communication is performed with a mobile station by M (M: natural number, hereinafter referred to as “directional antenna 10” when collectively referred to).

  As will be described later, the system server 300 calculates the position of the unmanned aircraft at a plurality of times as described later from the position and speed of the unmanned aircraft based on the received telemetry data and the received intensity by linear prediction. The system server 300 calculates the propagation loss (distance attenuation + shadowing amount) on the assumption that the shadowing amount is the same at the predicted position, and when the received power becomes the minimum among a plurality of times when the prediction is executed. The tracking direction is determined based on the information. Unless otherwise specified, the unmanned aircraft to be tracked by each ground station is determined according to the following criteria.

    i) An unmanned aerial vehicle with which the ground station is communicating is set as a first tracking target.

    ii) An unmanned aerial vehicle that is determined to be handed over to the ground station from the predicted flight path is set as the second tracking target.

  In this case, typically, when a plurality of unmanned aircrafts 100 are operated, the unmanned aircraft 100 (first tracking target) located in the vicinity of the ground station is tracked by the side lobe while approaching from a distance. The unmanned aerial vehicle 100 (second tracking target) is captured by the main lobe.

  In a state where a plurality of unmanned aircrafts 100 are simultaneously in the range of the main lobe, only the main lobe is used to track the unmanned aircraft on the near side and the unmanned aircraft on the far side at the same time.

  In FIG. 1, the directional antennas 10.1-10. M directivity main lobe range is defined as beam direction BM. 11-BM. M1 as the range of the side lobe, the beam direction BM. 12-BM. Shown as M2.

  Each ground station 200 receives telemetry data from the unmanned aerial vehicle 100 and application data (for example, image data) transmitted by the wireless LAN. At that time, in any of the wireless interfaces, the received power measuring units 22.1 to 22. M (referred to collectively as “reception power measurement unit 22”) measures the reception power of the signal transmitted by each unmanned aerial vehicle 100 and transmits the information to the system server 300. Then, the tracking direction of the tracking antenna and the use frequency channel of the wireless LAN are changed based on an instruction from the system server 300, and information on the use frequency channel, the connection destination ground station of the wireless LAN and the use directional antenna is transmitted to the unmanned aircraft 100. To do.

  The system server 300 includes unmanned aircraft 100.1 to 100.2 to ground stations 200.1 to 200. Position / attitude information of unmanned aerial vehicles 100.1 to 100.2 transmitted via M, and ground stations 200.1 to 200.200. Based on the signal strength information of the unmanned aerial vehicles 100.1 to 100.2 received at M, the wireless communication link capable of ensuring the transmission speed necessary for the intended communication is monitored, and as described later, the unmanned aircraft The ground stations that connect and track wireless communication with 100.1 to 100.2 are ground stations 200.1 to 200.200. M from time to time, and select the selected ground station, eg, ground stations 200.1 and 200. The tracking direction of M is controlled.

That is, the system server 30
In 0, the propagation loss (distance attenuation and distance between the unmanned aircraft 100 and the ground station 200 is calculated from the telemetry data transmitted from the unmanned aircraft 100, the received power measured by the ground station, the ground station position, and the directivity pattern of each antenna. (Shadowing) is calculated. Further, as will be described later, the position of each unmanned aircraft 100 at a plurality of times is predicted, and a ground station antenna is obtained so that a desired communication opportunity is obtained based on information when the minimum reception power is obtained among the plurality of times. The tracking direction, the antenna used by the unmanned aircraft 100, the frequency channel used for the wireless LAN in each ground station, and the connection destination ground station of each unmanned aircraft 100 are determined.

Ground stations 200.1 and 200. M, tracking antenna control units 20.1 and 20.. M according to the tracking direction control signal from the system server 300, respectively. M is the drive unit 30.1 and 30. M are respectively controlled and driven to control the directional antennas 10.1 and 10. Control the direction of M. As a directivity driving method, for example, it may be configured to be driven by a gimbal mechanism having two or more axes, or the directivity may be controlled electronically as an array antenna.
(Configuration of unmanned aerial vehicle 100)
FIG. 2 is a functional block diagram for explaining the configuration of unmanned aerial vehicle 100 of the present embodiment.

  Unmanned aerial vehicle 100 includes a plurality of directional antennas 120, a switching device 124 for selecting an antenna to be used for a wireless link among the antennas of directional antenna 120, and a wireless unit for performing communication using the selected antenna. 122, an onboard computer 128 for controlling the flight and communication of the unmanned aircraft 100, a hybrid navigation device 126 including a GPS and a gyro for measuring the position and orientation of the unmanned aircraft 100, and an image from above And an imaging device 130 for capturing (still images, moving images).

  Information on the position, speed, attitude angle (yaw angle, roll angle, pitch angle) and attitude angular velocity of the unmanned aircraft 100 measured by the hybrid navigation device 126 is transmitted from the selected antenna to the ground station as telemetry data. For example, it is transmitted at regular time intervals. Information on the received radio wave intensity from the selected antenna 120 is measured by the ground station 200. Similarly, image data captured by the imaging device 130 in accordance with an instruction from the ground station is also transmitted to the ground station 200 from the selected antenna.

  As a method of selecting a specific antenna among the antennas 120 by the switching device 124, for example, an antenna having the largest gain can be selected at any time.

  Here, a plurality of directional antennas 120 of unmanned aircraft 100 may be provided as described above, but the number of antennas is one, and an antenna that can change the directivity by an instruction from the ground station is provided, and a switching device The directivity may be switched by 124.

  In the following description, for the sake of simplicity, the directivity of antenna 120 of unmanned aerial vehicle 100 is assumed to be isotropic in principle. In the case of having directivity, the gain of the directional antenna set at that time in the signal from the unmanned airplane 100 may be taken into consideration.

  FIG. 3 is a functional block diagram for explaining the configuration of the system server 300.

  The system server 300 is configured in the same manner as a known computer system, and an arithmetic device such as a CPU (Central Processing Unit) performs arithmetic processing based on a program stored in a storage device, as shown in FIG. Each function shall be executed.

  The system server 300 includes a communication interface (hereinafter, communication I / F) 302 for communicating with the ground station 200 (in FIG. 3, the ground stations 200.m-1 and 200.m are illustrated). A position / attitude information acquisition unit 304 that acquires information on the position, velocity, attitude angle, and attitude angular velocity of the unmanned aircraft 100 transmitted from the unmanned aircraft 100 and received and transmitted by the ground station 200; Each of the ground stations 200 includes a tracking direction control unit 306 that generates a tracking direction control signal for controlling the direction in which the unmanned aircraft 100 is tracked based on information from the unit 304. The tracking direction control unit 306 uses information such as the position, speed, posture angle, posture angular velocity, and the like of the unmanned aircraft 100 transmitted from the unmanned aircraft 100 side in order to select the antenna 120 having a high gain in the unmanned aircraft 100. Thus, an instruction to select the antenna having the maximum gain is generated as a tracking direction control signal from the relative attitude angle with the ground tracking antenna 10 in charge of tracking. Alternatively, if the antenna 120 of the unmanned aerial vehicle 100 is configured to change the directivity, a signal for changing the directivity may be generated as the tracking direction control signal so that the gain is maximized. Each tracking direction control signal is transmitted to the corresponding ground station 200. Hereinafter, for the sake of convenience, description will be made assuming that selection is performed from a plurality of antennas.

  The system server 300 further includes a signal strength information acquisition unit 310 that acquires information on the received signal strength from the unmanned aircraft 100 received by the ground station 200, and information of the unmanned aircraft 100 based on information from the signal strength information acquisition unit 310. And a connection station control unit 312 that generates a connection station instruction signal for controlling selection of a ground station provided with a tracking antenna in charge of tracking. Each connection station instruction signal is transmitted to the corresponding ground station 200.

  As will be described later, the connecting station control unit 312 predicts the position of each unmanned aircraft 100 at a plurality of times, so that a desired communication opportunity can be obtained based on information when the minimum reception power is obtained among the plurality of times. A process for determining the frequency channel used for the wireless LAN in each ground station and the ground station to which each unmanned aircraft 100 is connected is executed, and a connection station instruction signal for instructing the preparation for the handover and the execution of the handover is performed. Output. The tracking direction control unit 306 determines the tracking direction of the ground station antenna and the antenna used by the unmanned aircraft 100 based on the information from the position / posture information acquisition unit 304 and the information from the connection station control unit 312 as described later. Thus, a tracking direction control signal is generated.

  The system server 300 further includes an imaging data acquisition unit 320 that receives imaging information from the unmanned aerial vehicle 100 via the ground station 200, and a storage device 322 for storing the acquired imaging data.

  System server 300 may be installed as a single server for centrally managing a combination of a plurality of unmanned aircraft 100 and a plurality of tracking antennas 10, or may be configured by a plurality of servers arranged in a distributed manner. Good.

  In particular, in the present embodiment, system processing for the following problems during handover will be described.

  Since the ground station antenna has a sharp directivity, simultaneous tracking becomes difficult when a plurality of unmanned aircraft 100 approaches the same ground station from different directions. Therefore, in order to realize good tracking of the unmanned aircraft 100, it is necessary to appropriately determine which ground station tracks which unmanned aircraft 100. For this purpose, not only the propagation loss and position information as described above, but also the positional relationship between the unmanned aircraft such as overtaking and passing of the unmanned aircraft 100 is determined based on the prediction of the position of the unmanned aircraft at a plurality of times. It is necessary to consider whether it is expected to become.

  FIG. 4 is a diagram for explaining a concept of processing of the ground station 200 and the system server 300 when the system server 300 tracks the unmanned aircraft 100.1 and 100.2.

  For example, in the configuration shown in FIG. 4, the tracking antenna 10. m and 10. m-1 is used to estimate the state of time t = t1 + τ after a certain time τ from the state in which the unmanned aircraft 100.1 is being tracked, that is, the state of the wireless aircraft at one time, and the tracking antenna 10. m and 10. Although a configuration in which the tracking of the unmanned aircraft 100.1 and 100.2 is continued by m−1 is considered, in that case, there is a problem as described below.

  FIG. 5 is a conceptual diagram for explaining a first problem in the case where the tracking process for the unmanned aircraft 100 is performed based on the prediction of the position of the unmanned aircraft.

  FIG. 6 is a conceptual diagram for explaining a second problem in the case where the tracking process for the unmanned aircraft 100 is performed based on the prediction of the position of the unmanned aircraft.

  First, the first problem will be described with reference to FIG.

  Here, it is assumed that the tracking process and the handover process between the ground stations are controlled in a cycle of a predetermined time interval Th. The tracking process and the handover process between the ground stations are assumed to be completed in one cycle within the processing delay τ after the start.

  In the example shown in FIG. 5, the ground station is tracking two UAV1 and UAV2 at the current time.

  Then, it is assumed that the prediction process is executed only for the state at one future time t = t1 + τ. Here, for example, τ is a predetermined time shorter than Th. In this case, at the predicted position, the two UAV1 and UAV2 still can be tracked by one beam of the ground station, and it is determined that the handover is unnecessary. However, at t = t1 + 2 × Th, which is the next control point, both UAV1 and UAV2 are out of the beam range of the ground station, and thereafter, the desired received power can be obtained from any UAV. Otherwise, the control becomes unstable.

  Next, the second problem will be described with reference to FIG.

  In the example shown in FIG. 6, there are irregularities in the beam intensity distribution of the ground station.

  As a result, assuming that the prediction process is executed only for the state of one future time t = t1 + τ, if UAV1 happens to be in the middle position at the handover control timing, the gain is larger than expected. May become small and reception power may be insufficient.

  FIG. 7 is a conceptual diagram for explaining a plurality of times that are targets of prediction processing in the present embodiment.

  In the present embodiment, prediction processing is executed for at least two or more times among the following times.

1) Time of (control start time t1) + (processing delay τ): t1 + τ
In other words, this is the time from which the handover process should be covered by the control currently performed from the time when the tracking process cycle is started.

2) Time of (next control start time t2) + (processing delay τ): t2 + τ
That is, this is the time that is the end point of the time that should be covered by the control of the handover process that is currently performed.

3) Time t3 between time (t1 + τ) and time (t2 + τ)
This is the time between the above 1) and 2). For example, at least one time in this period can be set in advance. If prediction at this time is taken in, it is possible to cope with the above-described unevenness of the beam shape.

4) Time t4 between the present time and time (t1 + τ), or between the time (t2 + τ) and a predetermined time has elapsed.
Again, at least one time of this period can be set in advance. If prediction at this time is also taken in, it is possible to cope with a case where there is an error in the estimation of the velocity vector and the angle variation is larger than expected.

  In the present embodiment, the prediction at the time (t1 + τ) and the time (t2 + τ) is performed in preference to the prediction at other times among the plurality of times described above in order to reliably perform the handover process. It is desirable to do.

  The prediction at the time t3 and the time t4 may be further executed on the assumption that the prediction at the time (t1 + τ) and the time (t2 + τ) is performed.

  FIG. 8 is a flowchart for explaining the processing flow of unmanned aerial vehicle 100, ground station 200, and system server 300 for executing the concept shown in FIG.

  4 and 8, first, in system server 300, telemetry data received from unmanned aerial vehicle 100 and transferred from a ground station in step S300 and step S200, and information on received signal strength from unmanned aerial vehicle 100 are shown. The first communication ground station is determined based on (S100). As such initial setting, for example, the system server 300 can calculate the tracking direction control signal and the connection station instruction signal based on information from all the ground stations 200.

  Such determination of the first communication ground station is performed by the tracking direction control unit 306 if there is a ground station whose current received power is equal to or higher than the communication start threshold value Pcomm for a moment or for a certain period of time. The initial communication destination is determined as follows.

a) Among the ground stations that have not performed communication or handover processing, the predicted propagation loss after a certain time is the minimum. b) When there is no ground station that satisfies the condition a), it is in communication with another unmanned aircraft. If there is a ground station that satisfies the above a) and an unmanned aircraft among the ground stations that have not been handed over, the predicted propagation loss after a certain time is minimum. Is set as the first tracking target.

  In the case of b), the unmanned aircraft is set as the second tracking target of the initial communication destination ground station.

  Subsequently, the tracking direction control unit 306 generates a tracking direction control signal and transmits the tracking direction control signal to the ground station 200 (S101), and the connected station control unit 312 performs tracking of the tracking antenna (connected ground station). It is determined whether it is necessary to change or determine or change the use frequency channel of the wireless LAN (Y in S102), and transmit to the ground station 200 as a connection station instruction (S104).

  The ground station 200 receives the tracking direction control signal and the control signal of the connection station instruction signal from the system server 300 (S200), and the connection station instruction instructs to prepare for handover or change the connection ground station (handover). In some cases (S202), an instruction for handover is generated (S204), and the direction of the tracking antenna is controlled in accordance with the tracking direction control signal (S206).

  The ground station 200 further instructs the unmanned aircraft 100 to select an antenna to be used for transmission / reception from among the antennas 120, instructs a handover, and transmits imaging information as necessary. A control signal to be instructed is transmitted (S208).

  In the unmanned aircraft 100, the onboard computer 128 acquires information such as position and attitude from the hybrid completed navigation device (S300), and receives the control signal transmitted from the ground station 200 in S208 (S302).

  In the unmanned aerial vehicle 100, when the switching device 124 instructs the selection of one of the antennas 120 or the handover by the control of the onboard computer 128 based on the instruction from the ground station 200, Processing for selecting a ground station is performed (S304).

  Subsequently, the unmanned aerial vehicle 100 transmits information on its own position, posture, and the like to the ground station 200 (S306), and transmits imaging information to the ground station 200 in response to an instruction from the ground station 200. (S308).

  On the other hand, the ground station 200 receives information on the position, posture, and the like from the unmanned aerial vehicle 100 (S210), and acquires information on the signal reception strength of the unmanned aircraft 100 from the ground station 200 (S212). The imaging information from the unmanned aircraft 100 is received (S214), and the information received from the unmanned aircraft 100 is transmitted to the system server 300 (S216).

The system server 300 receives the signal transmitted from the ground station 200 in step S216 (S106), and calculates a tracking direction control signal and a connection station instruction signal for the ground station 200 (S108).
[Tracking target update process and antenna tracking direction update process for UAV]
In the following, a process in which the system server 300 performs tracking direction control and connection station control (handover) in step S108 in FIG. 8 will be described.

  In the following, for the sake of simplicity, the unmanned aircraft is simply referred to as “UAV”.

  FIG. 9 is a flowchart for explaining the tracking target update process and the antenna tracking direction update process for the UAV executed by the system server 300 as step S108.

  Referring to FIG. 9, when the process of step S108 is started (S400), the connecting station control unit 312 of the system server 300 uses the telemetry data and the received intensity data acquired from the ground station to execute the above-described plural of UAVs. The position and propagation loss at the time are predicted (S402).

  Here, FIG. 10 is a flowchart for explaining processing for predicting the position and propagation loss of each UAV at a plurality of times.

  Referring to FIG. 10, first, connected station control section 312 performs the following “estimation of propagation loss between ground station antenna and UAV” after the start of processing (S500), so that the connection between ground station antenna and UAV is performed. Is estimated (S502).

[Estimation of propagation loss between ground station antenna and UAV]
In the m-th ground station (m = 1,..., M), the received power pm _{, n} [dBm] of the signal transmitted by the n-th UAV (n = 1,..., N) is measured and transmitted to the system server 300. . When the received power is small and demodulation of the signal fails, the received power is set to a predetermined set value p _fail [dBm].

Next, the connecting station control unit 312 calculates the distance attenuation L _{m, n} [dB] assuming free space propagation based on the distance dm _{, n} between the mth ground station and the nUAV.

Subsequently, the connecting station control unit 312 calculates the direction in which the n-th UAV is located when viewed from the m-th ground station based on the position information of the n-th UAV, and the angle difference from the direction currently being tracked by the ground-station antenna. (θ _{m, n} , φ _{m, n} ) (θ _{m, n} is in the horizontal direction, φ _{m, n} is in the vertical direction), and the directivity gain g _bs (θ _{m, n} , φ _{m, n} in the ground station antenna) is obtained. ) [DB] is calculated.

Finally, the connecting station control unit 312 uses the n-th UAV transmission power P [dBm] to set the shadowing level S _{m, n} [dB] between the m-th ground station and the n-th UAV as follows: Ask more. The transmission power P may be a predetermined value, or may be transmitted from the n-th UAV to the ground station 200 at a predetermined timing, for example.

If the UAV antenna has directivity or can be controlled, the connecting station control unit 312 determines whether the m-th ground station is located in the direction of the n-th UAV and the attitude direction of the n-th UAV. Directional gain g _UAV (θ _m on the UAV side) from the angle difference between them (θ _{m, n} bar, φ _{m, n} bar) (the one with the letter X attached to the head is called the X bar). _{, N} bar, φ _{m, n} bar) [dB] may be obtained and added to the above equation (1).

[UAV position prediction at multiple times]
Next, the connecting station control unit 312 calculates the UAV position at a plurality of times described in FIG. 7 by linear prediction from the position information and speed information of each UAV (S504).

[Prediction of propagation loss]
The connecting station control unit 312 then sets the distance “dm _{, n} hat (Tn)” between the m-th ground station and the predicted position of the _n- th UAV at a plurality of times (on the head of the letter Y representing the predicted amount). The one with ^ is called a Y hat.) (Tn is a distance attenuation L _{m, n} hat (Tn) at a plurality of times based on at least two of t1 + τ, t2 + τ, t3, and t4). .

    Subsequently, the connecting station control unit 312 derives a predicted propagation loss Hmn hat (Tn) from the following equation, assuming that the occurrence state of shadowing does not change between a plurality of times (S506).

Here, when the antenna has directivity or can be controlled on the UAV side, the connecting station control unit 312 determines the direction in which the m-th ground station is located from the n-th UAV and the attitude direction of the n-th UAV after τ has elapsed. The angle difference (θ _{m, n} hat, φ _{m, n} hat) is calculated, and the directivity gain g _UAV (θ _{m, n} hat, φ _{m, n} hat) on the UAV side is calculated based on this difference. In the Hmn hat (Tn), this gain g _UAV (θ _{m, n} hat, φ _{m, n} hat) may be subtracted.
[Prediction of received power]
Subsequently, the tracking direction control unit 306 predicts the received power at a plurality of times in the antenna tracking possible range for each UAV in each ground station 200 based on the estimated propagation loss Hmn hat (Tn) (S508).

  Subsequently, the tracking direction control unit 306 returns the process to step S404 in FIG. 9 (S510).

  Referring back to FIG. 9 again, the connecting station control unit 312 determines whether a handover (hereinafter abbreviated as HO) processing is currently being performed between ground stations for a certain UAV, and the HO processing is in progress. If HO is successful (Y in S404) (Y in S406), the tracking target in each ground station is updated to the target after HO (S408), and the process proceeds to step S420.

  On the other hand, if the HO process is not successful (N in S406), the connected station control unit 312 cancels the HO process (S412) if a predetermined time elapses and a timeout occurs (Y in S410). The process proceeds to step S420, or if the timeout has not occurred (N in S410), the process proceeds to step S420.

  Subsequently, the connecting station control unit 312 determines whether or not a UA is currently being prepared for a certain UAV between ground stations, and is preparing for HO (Y in S420). Is determined (Y in S422), the HO process is started in the HO target ground station 100 (S424), and the process proceeds to step S440.

  On the other hand, if the HO destination has not been determined (N in S422), the connected station control unit 312 cancels the HO preparation if a predetermined time has elapsed and timed out (Y in S426) (S428). The process proceeds to step S440, or if the timeout has not occurred (N in S426), the process proceeds to step S440.

  Subsequently, the connecting station control unit 312 determines whether the ground station 100 is communicating with all tracking target UAVs. If the ground station 100 is communicating (Y in S440), It is determined whether such a HO preparation start condition is satisfied (S442).

  If any one of the following conditions 1) to 4) is satisfied (Y in S442), the UAV scheduled for handover is set as the second tracking target of the ground station to which the handover is scheduled, The tracking target of the upper station is updated (S444), and an instruction to start handover preparation is given (S446). At this time, if the second tracking target is already set for the ground station scheduled for handover, it is determined that an appropriate handover destination could not be selected (N in S422).

  Here, FIG. 11 is a conceptual diagram for explaining the state of Condition 1 below.

  Condition 1) Exchange (swapping) of UAV during communication between adjacent ground stations is possible.

  For that purpose, the following needs to be satisfied.

1-1) Assuming that adjacent ground stations BSa and BSb are communicating with different UAVA and UAVb, respectively,
1-2) Whether both UAVa and UAVb are approaching to the ground station that is not communicating with each other (for example, UAVa is approaching to ground station BSb and UAVb is approaching to ground station BSa) (Fig. 11 (a)) or
1-3) When both UAVa and UAVb are approaching the same ground station (for example, BSb), and UAVb in communication with the ground station BSb is overtaken by UAVa (FIG. 11 (b)).
1-4) When the minimum value Ppred of predicted reception power at a plurality of times is equal to or greater than the communication start threshold value Pcomm.

  In addition, although it is not always necessary for 1-4) to be an indispensable condition, it is desirable that such a condition is satisfied.

  Condition 2) The UAV is approaching to a ground station that is not communicating or performing a handover process other than the currently communicating ground station, and the minimum value Ppred of predicted reception power at a plurality of times is equal to or greater than the communication start threshold value Pcomm. If it is.

  This condition 2 is for performing handover earlier with the ground station at the destination and allowing another UAV to be handed over to the currently communicating ground station.

  Condition 3) The current received power Pcbs of the ground station with which the UAV is currently communicating is below the threshold Pho.

  This condition 3 is for handover before the received power Pcbs becomes smaller than the required received power Preq (<Pho). Usually, communication start threshold value Pcomm ≧ required received power Preq.

  Condition 4) When there is at least one ground station having a maximum predicted propagation loss at a plurality of times of UAV that is smaller than the ground station currently communicating.

  This condition 4 is because reception power is expected to increase due to handover.

  When any of these conditions is satisfied, the ground station corresponding to the condition updates the tracking target of the ground station in order to perform HO (S444), and instructs the start of HO preparation.

  That is, when it is determined that the handover preparation start condition is satisfied, the system server 300 passes the hand after a certain period of time (the time required until tracking is performed after changing the antenna tracking target of the ground station). It is confirmed whether the required received power can be obtained at the over destination (S406), and when the required received power is obtained, the corresponding ground station starts the handover process (S408).

  When the handover preparation is started according to the above conditions 3 and 4, the handover destination is determined in the following manner (S444). When no corresponding candidate is found, the HO process is pending (S412).

      i) A ground station other than the currently communicating ground station that is not performing communication or handover processing and that has the smallest predicted propagation loss is selected as the handover destination.

      ii) If there is no ground station corresponding to the above i), if there is a ground station that is communicating with another UAV1 unit and is not performing the handover process, this is selected.

  Then, if the handover is successful, the connecting station control unit 312 deletes the UAV that has succeeded in the handover from the tracking target of the communication ground station before the handover (S408).

  Further, as described above, the connection station control unit 312 determines that the handover process has not been successful within the timeout period (Y in S410), or if an appropriate handover destination cannot be selected (N in S422). The HO process is canceled (S412), or the HO preparation is canceled (S428).

  Returning to FIG. 9 again, subsequently, the connecting station control unit 312 determines whether there is any UAV that is not communicating with any of the ground stations (S460).

  When there is a UAV that is not communicating with any ground station (Y in S460), the connecting station control unit 312 is, for example, in the same manner as in S444, “a ground station that is not performing communication or handover processing, If the communication destination can be determined by selecting the “ground station with the smallest predicted propagation loss” or “the ground station that is communicating with another UAV1 and has not been handed over” (Y in S462) The tracking target of the ground station to be updated is updated (S464), and the start of communication between the UAV that has not communicated and the determined ground station is instructed (S466).

  Furthermore, when there is a ground station that is not performing any communication or handover processing among the ground stations (Y in S480), the connecting station control unit 312 determines whether or not any UAV has an estimated propagation loss. For a ground station whose predicted received power Ppred after a certain time is equal to or greater than a predetermined value, the UAV is added to the tracking target of this ground station. However, the actual communication is started after it is determined that the HO condition is satisfied.

When the process by the connected station control unit 312 results in N in step S480, or when the process in step S482 ends, the tracking direction control unit 306 tracks the antenna of each ground station as described later. A direction control process is executed (S484), and the process returns to step S101 in FIG.
(Tracking direction control to UAV)
Hereinafter, processing in which the tracking direction control unit 306 of the system server 300 performs tracking direction control and connection station control in step S484 in FIG. 9 will be described.

  Telemetry data measured by the hybrid inertial navigation device 126 is transmitted to the ground station 200 through a wireless interface, and then collected in the system server 300.

  For this reason, the telemetry data collected by the system server 300 has been a little over time since the measurement was completed. In addition, it takes a time of several hundreds of milliseconds from the determination of the tracking direction of the ground station antenna to the stabilization of the pointing direction after the control is reflected. It is also necessary to ensure control stability at the next timing of the control cycle. Therefore, as described above, in the UAV tracking process, the position of each UAV at a plurality of times is linearly predicted, and a desired communication opportunity is obtained based on information when the minimum reception power is obtained at a plurality of times. Thus, the tracking direction of the ground station antenna is determined.

  As described below, in the present embodiment, it is assumed that each ground station mainly tracks up to two UAVs depending on the situation. Note that UAVs that track simultaneously may simultaneously track more aircraft depending on the tracking capability of the ground station.

When a plurality of UAVs are tracked by a plurality of ground station antennas in a wide area, it is appropriate that each ground station basically tracks a UAV located in the vicinity of itself.
[Direction control for simultaneous tracking of two UAVs]
FIG. 12 is a flowchart for explaining an algorithm for performing tracking direction control for two UAVs.

  As described above, the connected station control unit 312 basically sets the connected ground station so that the UAV satisfying the condition is tracked based on the predicted propagation loss and the predicted received power. The tracking direction control unit 306 selects the direction in which the UAV is located as the tracking direction.

  Hereinafter, as a premise of FIG. 9, the connecting station control unit 312 performs the predicted propagation loss Hmn hat (Tn) for the UAVs of the first tracking target and the second tracking target in each ground station 200 as shown in FIG. ) Is used to predict received power at a plurality of times within the antenna tracking range (S508).

Therefore, in FIG. 12, the tracking direction control unit 306 first initializes a variable PL for counting a plurality of times to 1 (S520), and then in step S522, the tracking direction control unit 306 determines each tracking direction. The predicted received power at is compared with the received power threshold p _thre [dBm] expressed by the following equation.

Here, p _req [dBm] is a required received power, and p _mrgn [dB] is a margin amount for the required received power.

  In this algorithm, assuming that there are the following three cases, the tracking direction control unit 306 determines the tracking direction.

  FIG. 13 is a conceptual diagram showing the expected received power in case A.

  FIG. 14 is a conceptual diagram showing the expected received power in case B.

  FIG. 15 is a conceptual diagram showing the expected received power in case C.

  With reference to FIGS. 12 and 13 to 15, the tracking direction control unit 306 classifies cases as follows.

Case A: When there is no tracking direction in which the predicted received power of the first tracking target UAV is greater than or equal to the received power threshold (N in S522)
Case B: Although there is a tracking direction in which the predicted received power of the first tracking target UAV is equal to or greater than the received power threshold, the predicted received power of the second tracking target UAV is less than the received power threshold ( (In the case of one aircraft in S524)
Case C: When there is a tracking direction in which the received power of both tracking target UAVs simultaneously exceeds the received power threshold (in the case of two aircraft in S524)
The tracking direction control unit 306 determines which case the predicted position of the current process target corresponds to (S526), and stores the case that is the worst condition for the predicted position of the process target so far. Specifically, if the case corresponding to case A is included in the predicted position of the current processing target or the current processing target, it is determined as case A, and the case where the current processing target corresponds to case A If it is not included and the predicted position of the current processing target corresponds to Case B, it is determined as Case B, and the processing target so far does not include the case corresponding to Case A or Case B. If the predicted position to be processed corresponds to case C, it is determined as case C (S528).

  The tracking direction control unit 306 returns the process to step S522 if the process of the predicted position corresponding to a plurality of times has not been completed (N in S530), and if the process has been completed (Y in S530). It is finally determined which case is the worst condition for the target ground station (S534).

  In case A, the direction in which the predicted received power of the first tracking target UAV is maximized is set as the tracking direction (S540).

In case B, the direction in which the predicted received power of the second tracking target UAV is the largest in the tracking direction in which the predicted received power of the first tracking target UAV is equal to or greater than the received power threshold p _thre is the tracking direction. Set (S542).

In case C, the predicted received power of the first tracking target UAV and the predicted received power of the second tracking target UAV in the tracking direction in which the predicted received powers of both tracking target UAVs simultaneously _{exceed the} received power threshold p _thre. The direction in which the value with the smaller power is maximized is set as the tracking direction (S544).

  By controlling as described above, it is possible to realize a state in which each ground station 200 tracks two unmanned aircraft 100 at the same time as much as possible. Therefore, when a handover is necessary, The probability that the unmanned aircraft 100 being tracked by the ground station is also being tracked by the ground station as the handover destination can be increased, and efficient handover can be realized. In addition, since the probability that the received power is maintained at a predetermined threshold value or higher at the handover source and the handover destination can be increased, the time during which the required received power cannot be ensured can be kept small.

  As described above, according to the tracking antenna system and the tracking antenna apparatus of the present embodiment, it is possible to execute an efficient and stable handover in tracking a plurality of flying objects by a plurality of ground stations.

  Embodiment disclosed this time is an illustration of the structure for implementing this invention concretely, Comprising: The technical scope of this invention is not restrict | limited. The technical scope of the present invention is shown not by the description of the embodiment but by the scope of the claims, and includes modifications within the wording and equivalent meanings of the scope of the claims. Is intended.

  10.1-10. M directional antenna, 30.1-30. M drive unit, 100.1, 100.2 unmanned aircraft, 120 antenna, 200.1-200. M ground station, 122 radio unit, 124 switching device, 126 hybrid inertial navigation device, 128 on-board computer, 130 imaging device, 300 system server, 302 communication I / F, 304 position / attitude information acquisition unit, 306 tracking direction control unit, 310 signal strength information acquisition unit, 312 connection station control unit, 320 imaging data acquisition unit, 322 storage device.

Claims (4)

A tracking antenna system,
With multiple flying objects,
Each of the plurality of projectiles is
A positioning means for grasping its own position, speed and posture;
A fuselage antenna capable of transmitting and receiving wireless signals,
A plurality of ground stations for performing wireless communication with the plurality of flying objects,
Each of the plurality of ground stations is
A tracking antenna that can change communication directivity,
In response to the tracking control instruction, directivity control means for driving the communication directivity of the tracking antenna in the direction of the corresponding flying object among the plurality of flying objects;
Signal strength measuring means for measuring the received signal strength from the flying object,
The tracking antenna can set first and second tracking targets from the plurality of flying objects,
A control station for selecting a flying object to which each of the plurality of ground stations is connected, and for generating a tracking control instruction for controlling communication directivity of the plurality of ground stations;
The control station
Flying object position estimating means for estimating the position of the flying object at a plurality of times based on the information on the position, speed, and posture of each of the flying objects;
Based on the estimated plurality of positions of the flying object and the received signal strength information, each ground station estimates a propagation loss at each time for the flying object, and based on the estimated propagation loss. Receiving power prediction means for predicting received power at the plurality of times,
Based on the predicted received power at the plurality of times, tracking direction control means for determining the tracking direction according to the case where the reception situation is predicted to be worst,
In the ground station in communication with respect to the specific set of flying objects, when the flying object is approaching a ground station other than the currently communicating ground station that is not performing communication or handover processing, A tracking antenna system including ground station replacement control means for outputting the tracking control signal to the ground station so as to add a projectile whose replacement is predicted to the second tracking target of the previous ground station. . In the handover process, a control process is executed at predetermined time intervals,
2. The tracking antenna system according to claim 1, wherein the plurality of times include a first time after a processing delay of a current handover control and a second time after a processing delay of a next handover control.   The tracking antenna system according to claim 2, wherein the plurality of times includes a third time between the first time and the second time. A tracking antenna apparatus for tracking a plurality of flying objects for wireless communication, wherein each of the plurality of flying objects includes positioning means for grasping its own position, velocity, and attitude, and a radio signal Including a fuselage antenna capable of transmitting and receiving,
A tracking antenna that can change communication directivity,
Signal strength measuring means for measuring the received signal strength from the flying object;
Directivity control means for driving communication directivity in the direction of the corresponding flying object among the plurality of flying objects,
The tracking antenna can set first and second tracking targets from the plurality of flying objects,
The directivity control means includes
Flying object position estimating means for estimating the position of the flying object at a plurality of times based on the information on the position, speed, and posture of each of the flying objects;
Based on the estimated plurality of positions of the flying object and the received signal strength information, each ground station estimates a propagation loss at each time for the flying object, and based on the estimated propagation loss. Receiving power prediction means for predicting received power at the plurality of times,
Based on the predicted received power at the plurality of times, tracking direction control means for determining the tracking direction according to the case where the reception situation is predicted to be worst,
In the ground station in communication with respect to the specific set of flying objects, when the flying object is approaching a ground station other than the currently communicating ground station that is not performing communication or handover processing, A tracking antenna apparatus including ground station replacement control means for outputting the tracking control signal to the ground station so as to add a projectile whose replacement is predicted to the second tracking target of the previous ground station. .