Patent Publication Number: US-2022227479-A1

Title: Flying body, control method, and program

Description:
TECHNICAL FIELD 
     The present disclosure relates to a flying body, a control method, and a program. 
     BACKGROUND ART 
     Recently, unmanned autonomous flying bodies called unmanned aerial vehicles (UAVs) or drones (hereinafter appropriately referred to as a drone) have been used in various situations such as various types of photographing, observation, and disaster relief. Accordingly, various control methods for drones have been proposed (refer to PTL 1, for example). 
     CITATION LIST 
     Patent Literature 
     [PTL 1]
     JP 2018-52341 A   

     SUMMARY 
     Technical Problem 
     In general, an attitude of a drone at the time of landing is affected by wind and thus easily becomes unstable. Accordingly, there is need for control of an attitude of a drone such that the drone can land in a stable attitude even in a case where the drone is affected by wind. 
     The present disclosure has been devised in view of the above-described circumstances and an objective of the present disclosure is to provide a flying body controlled to land in a stable attitude even in a case where the flying body is affected by wind, a control method, and a program. 
     Solution to Problem 
     The present disclosure is, for example, a flying body including a control unit configured to set a horizontal ground speed on the basis of wind information including information about a wind direction and a wind speed. 
     The present disclosure is, for example, a control method in a flying body, including setting, by a control unit, a horizontal ground speed on the basis of wind information including information about a wind direction and a wind speed. 
     The present disclosure is, for example, a program causing a computer to execute a control method in a flying body, including setting, by a control unit, a horizontal ground speed on the basis of wind information including information about a wind direction and a wind speed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram that will be referred to when problems to be considered in an embodiment are described. 
         FIG. 2  is a diagram that will be referred to when problems to be considered in an embodiment are described. 
         FIG. 3  is a diagram referred to when an overview of an embodiment is described. 
         FIG. 4  is a diagram referred to when an overview of an embodiment is described. 
         FIG. 5  is a diagram referred to when an overview of an embodiment is described. 
         FIG. 6A  to  FIG. 6C  are diagrams that will be referred to when an example of a wind information estimation method is described. 
         FIG. 7  is a block diagram illustrating a configuration example of a drone according to a first embodiment. 
         FIG. 8  is a flowchart illustrating a flow of processing performed in the drone according to the first embodiment. 
         FIG. 9  is a block diagram illustrating a configuration example of a drone according to a second embodiment. 
         FIG. 10  is a flowchart illustrating a flow of processing performed in the drone according to the second embodiment. 
         FIG. 11  is a flowchart illustrating a flow of processing performed in a drone according to a third embodiment. 
         FIG. 12  is a block diagram illustrating a configuration example of a drone according to a fourth embodiment. 
         FIG. 13  is a flowchart illustrating a flow of processing performed in the drone according to the fourth embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The description will be made in the following order. 
     &lt;Problems to be considered in embodiments&gt; 
     &lt;Overview of embodiments&gt; 
     &lt;First Embodiment&gt; 
     &lt;Second Embodiment&gt; 
     &lt;Third Embodiment&gt; 
     &lt;Fourth Embodiment&gt; 
     &lt;Modified examples&gt; 
     The embodiments to be described below are preferred specific examples of the present disclosure and content of the present disclosure is not limited to the embodiments. 
     Problems to be Considered in Embodiments 
     First, to facilitate understanding of the present disclosure, problems to be considered in embodiments will be described with reference to  FIG. 1  and  FIG. 2 . 
       FIG. 1  is a diagram schematically illustrating a state in which a drone  1  is landing. In the example illustrated in  FIG. 1 , the wind is blowing from the left to the right with respect to the drone  1  in the figure. For stable landing of the drone  1 , it is desirable that a horizontal ground speed of the drone  1  become 0 or a value close to 0 at the time of landing. When the drone  1  is caused to vertically descend, a method of causing the drone  1  to fly at the same speed as that of the wind in a direction reverse to the wind such that the horizontal ground speed becomes 0 near the ground surface is conceived. When such control is performed, an attitude of the drone  1  inclines to the windward side (a state represented by reference signs A 1  and A 2  in  FIG. 1 ). Then, a side of the airframe of the drone  1  close to the ground is subjected to a considerable ground effect at the time of approaching the ground surface, causing generation of rotation moment (a state represented by reference sign A 3  in  FIG. 1 ). Due to generation of the rotation moment, attitude control of the drone  1  becomes difficult. Furthermore, since the drone  1  lands in an inclined state, the drone  1  may overturn at the time of landing (a state represented by reference sign A 4  in  FIG. 1 ). 
     Accordingly, as illustrated in  FIG. 2 , control of causing the drone  1  to vertically descend (a state represented by reference signs A 5  and A 6  in  FIG. 2 ) and making the airframe horizontal in a state in which the drone  1  has approached the ground surface (a state represented by reference sign A 7  in  FIG. 2 ) is conceived. However, when the attitude of the drone  1  significantly changes near the ground surface, the attitude of the drone  1  easily becomes unstable. Furthermore, the drone  1  sways in the wind according to change in the attitude thereof, and thus landing may become unstable because the drone  1  maintains a horizontal ground speed. Based on the above description, control for landing the drone  1  in a stable state is performed in embodiments of the present disclosure. 
     Overview of Embodiments 
     Next, an overview of embodiments of the present disclosure will be described. In the present description, common matters in embodiments will also be described. 
     Overview of Embodiments 
       FIG. 3  is a diagram for describing an overview of embodiments. It is assumed that the drone  1  lands at a landing point LP illustrated in  FIG. 3 . The landing point LP may be a position of preset coordinates or a position of coordinates instructed by an appropriate apparatus on the ground (hereinafter appropriately referred to as a ground station). A transition point PA is set at an appropriate position in the space, as illustrated in  FIG. 3 . The transition point PA is a point positioned above the landing point LP and a point at which the drone starts a landing operation. The drone  1  present at a position in a certain space (above the transition point PA) determines to land. For example, the drone  1  determines to land by itself according to an instruction through a remote controller, completion of a given task, reduction in remaining capacity of a battery, malfunction of a sensor included in the drone  1 , occurrence of communication failure, and the like. 
     When landing is determined, the drone  1  acquires wind information. The wind information includes information about the wind that affects flight of the drone and includes information about a wind direction and a wind speed. Such wind information may be acquired through a sensor included in the drone  1  or may be transmitted from a ground station to the drone  1 . 
     The drone  1  determines a landing approach sequence and a grounding sequence. The landing approach sequence is control for the drone  1  performed from a current position (PB in  FIG. 3 ) of the drone  1  to the transition point PA. A specific example of the landing approach sequence is information representing chronological positions of the drone  1  from the current point PB to the transition point PA and a speed of the drone  1  at each position. Here, for stable landing of the drone  1 , it is desirable that a horizontal ground speed at the time of landing be approximately 0. Approximately 0 means that the horizontal ground speed is 0 or close enough to 0 for the drone  1  to safely land. Accordingly, at the transition point PA, control of assigning a horizontal ground speed to the drone  1  in advance such that the horizontal ground speed of the drone  1  becomes approximately 0 at the landing point LP is performed in the landing approach sequence. Specifically, rotation speeds of a plurality of motors included in the drone are controlled such that the horizontal ground speed of the drone becomes a set horizontal ground speed. A movement trajectory of the drone  1  from the current point PB to the transition point PA and a horizontal ground speed at each position are calculated such that a predetermined horizontal ground speed is assigned at the transition point PA, and the operation of the drone  1  is appropriately controlled on the basis of a calculation result. 
     The grounding sequence is control for the drone  1  performed from the transition point PA to the landing point LP. When the drone  1  detects that it has passed through the transition point PA, the drone  1  is controlled according to the grounding sequence. The grounding sequence is, for example, information representing chronological positions until landing and a vertical speed at each position. Meanwhile, control of making the attitude of the drone  1  horizontal or a horizontal ground speed at each position is defined in the grounding sequence. The drone  1  descends toward the landing point LP by being controlled on the basis of the grounding sequence, as illustrated in  FIG. 3 . Since the horizontal ground speed becomes approximately 0 at the time of landing in a state in which the airframe of the drone  1  has become horizontal, it is possible to curb inclining of the airframe of the drone  1  and cause the drone  1  to land in a stabilized attitude. 
     Common Matters in Embodiments 
     (Transition Height) 
     Next, common matters in embodiments will be described. First, a transition height H that is a height from the landing point LP to the transition point PA will be described. Meanwhile, coordinates of the landing point LP are denoted by (x, y, 0) and coordinates of the transition point PA are denoted by (x′, y′, H) (refer to  FIG. 4 ). 
     When the transition height is H, a descending speed of the drone  1  is v z (t), a time from a transition point is t, a time taken to land is t t , a downward speed of the drone  1  at the transition point PA (hereinafter appropriately referred to as a descending speed at the time of transition) is v z (0)=v zH , and a downward speed of the drone  1  at the time of landing (hereinafter appropriately referred to as a descending speed at the time of landing) is v z (t t )=v z0  (refer to  FIG. 4 ), this relation is represented by the following mathematical formula 1. 
     
       
         
           
             
               
                 
                   H 
                   = 
                   
                     
                       ∫ 
                       0 
                       
                         t 
                         t 
                       
                     
                     ⁢ 
                     
                       
                         
                           v 
                           z 
                         
                         ⁡ 
                         
                           ( 
                           t 
                           ) 
                         
                       
                       ⁢ 
                       dt 
                     
                   
                 
               
               
                 
                   [ 
                   
                     Math 
                     . 
                     
                         
                     
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                     1 
                   
                   ] 
                 
               
             
           
         
       
     
     Particularly, when the descending speed decreases at a constant rate, the aforementioned integration is analytically solved and represented by the following mathematical formula 2. 
         H= ½( v   zH   −v   z0 )· t   t   [Math. 2]
 
     A descending speed at the time of landing is set to a speed no higher than a descending speed at which a drone can safely land. When the descending speed at the time of landing is set to 0 or considerably close to 0, the drone is likely to be unable to ground in the case of large position error, and thus the descending speed at the time of landing is set to a speed within a range in which the drone can safely land. The descending speed at the time of landing may be set depending on specifications of an airframe. Furthermore, a transition height may be set to an approximate indication according to a size of an airframe (e.g., about several times the diameter of the airframe). In such a case, a height set to the transition height H may be used. As an example, the transition height H is calculated by approximately adjusting the descending speed at the transition v zH  and the time t t . 
     (Horizontal Ground Speed) 
     Next, a horizontal ground speed will be described. When the mass of the drone  1  is M and the acceleration of gravity thereof is g, the rotor thrust of the drone  1  can be represented by (Mg+F v ) (refer to  FIG. 5 ). Further, a horizontal force 
         ( {right arrow over (v)}   d   ,{right arrow over (v)}   w ) 
     which is a horizontal component of a wind pressure is received according to the wind in the horizontal direction. 
     
       
      
       
      
     
     is a horizontal ground speed vector of the drone  1 . In addition, 
     
       
      
       
      
     
     is a wind vector in the horizontal direction. 
     The horizontal ground speed vector 
     
       
      
       
      
     
     of the drone  1  is represented by the following differential equation from the equation of motion. 
         = ( {right arrow over (v)}   d   ,{right arrow over (v)}   w )/ M    
     If the aforementioned equation is solved under the condition that the horizontal ground speed of the drone  1  at the grounding time t t  is 0 and 
         {right arrow over (v)}   d ( t   t )=0, 
     the horizontal ground speed 
         {right arrow over (v)}   d (0) 
     of the drone  1  at the transition point PA can be obtained. 
     Although 
         ( {right arrow over (v)}   d   ,{right arrow over (v)}   w ) 
     needs to be clear for the aforementioned equation, it can be approximated according to the following mathematical formula 3. 
         ≅ K   1 ( − )+ K   2 | − |( − )  [Math. 3]
 
     K 1  and K 2  are primary and secondary constants of a wind pressure applied to the drone  1 . K 1  and K 2  can be obtained in advance according to experiments, simulations, or the like. When only a component parallel to the wind in speeds of the drone  1  is taken, an equation represented by the following mathematical formula 4 is acquired. 
     
       
         
           
             
               
                 
                   
                     
                       ν 
                       · 
                     
                     d 
                   
                   = 
                   
                     
                       
                         
                           K 
                           1 
                         
                         M 
                       
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                         ( 
                         
                           
                             v 
                             w 
                           
                           - 
                           
                             v 
                             d 
                           
                         
                         ) 
                       
                     
                     + 
                     
                       
                         
                           K 
                           2 
                         
                         M 
                       
                       ⁢ 
                       
                         
                           ( 
                           
                             
                               ν 
                               w 
                             
                             - 
                             
                               v 
                               d 
                             
                           
                           ) 
                         
                         2 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     Math 
                     . 
                     
                         
                     
                     ⁢ 
                     4 
                   
                   ] 
                 
               
             
           
         
       
     
     If the aforementioned mathematical formula 4 is numerically solved or analytically solved by approximating K 2  to K 2 =0, a horizontal ground speed 
         {right arrow over (v)}   d (0) 
     of the drone  1  necessary at the transition point PA can be obtained. 
     Such a horizontal ground speed is set by a control unit included in a drone according to each embodiment. Meanwhile, when the horizontal ground speed of the drone  1  is determined, horizontal coordinates (x′, y′) of the transition point PA are determined by performing integration or the like on the horizontal ground speed. Then, it is combined with the transition height H determined as described above and thus the coordinates (x′, y′, H) of the transition point PA are determined. 
     (Wind Information Estimation Method) 
     Next, a wind information estimation method will be described. In the present description, an example in which wind information is acquired by the drone  1  (multicopter) is described. 
     As a method of estimating wind information, the drone  1  is maintained horizontal and the airspeed of the drone  1  is set to 0, as schematically illustrated in  FIG. 6A . Since a ground speed 
     
       
      
       
      
     
     of the airframe at that time becomes equal to a wind vector 
         , 
     this value is set as wind information. 
     As another method of estimating wind information, a wind vector 
     
       
      
       
      
     
     is estimated by vector-subtracting a ground speed 
     
       
      
       
      
     
     of the airframe from an airspeed 
     
       
      
       
      
     
     estimated according to a speedometer mounted in the drone  1  or airframe attitude (refer to  FIG. 6B ). An estimation result is set as wind information. 
     When uncertainty of estimation of a ground speed is high, the drone  1  flies along a course returning to a start point atmospherically (refer to  FIG. 6C ) and a wind direction and a wind speed are estimated from a difference between airspeeds at the start point and an end point. Accordingly, it is possible to cancel uncertainty of an airspeed estimate value. 
     In addition to the above-described methods, wind information may also be estimated on the basis of change in a position of simultaneous localization and mapping (SLAM) performed in the drone  1 , the attitude of the drone  1 , and motor output. In addition, wind information may be estimated on the basis of differences between a Global Positioning System (GPS) position of the drone  1  and the attitude of the drone  1  and motor output. Wind information may be estimated or measured by a ground station that is an external apparatus or another drone. Then, the measured wind information may be transmitted from the ground station to the drone  1  and acquired by a wind information acquisition unit. Further, wind information may be input by a user through a user interface (UI) and the input wind information may be transmitted to the drone  1 . 
     First Embodiment 
     [Example of Internal Configuration of Drone] 
       FIG. 7  is a block diagram illustrating an example of an internal configuration of a drone (hereinafter appropriately referred to as a drone  1 A) according to a first embodiment. For example, the drone  1 A includes a control unit  101 , an airframe control unit  102 , a sensor unit  103 , an airframe information acquisition unit  104 , a wind information acquisition unit  105 , and a communication unit  106 . The control unit  101  includes a flight status management unit  101 A, a flight planner  101 B, a landing planner  101 C, and an attitude planner  101 D as functional blocks. 
     The control unit  101  integrally controls the drone  1 A. The flight status management unit  101 A integrally manages flight statuses of the drone  1 A and switches between control according to the flight planner  101 B and control according to the landing planner  101 C depending on a flight status. The flight planner  101 B generates a flight course plan of the drone  1 A. The flight course plan is information in which chronological positions through which the drone  1 A flies and speeds at the positions are defined. The flight course plan may be set in advance or set by the flight planner  101 B according to a task assigned to the drone  1 A, or the like. The flight planner  101 B outputs the flight course plan to the attitude planner  101 D. 
     The landing planner  101 C generates an approach course plan and a grounding course plan. The approach course plan is information in which chronological positions from a current position of the drone  1 A to the transition point PA and speeds at the positions are defined. In addition, the grounding course plan according to the present embodiment is information in which attitudes, chronological positions, and vertical speeds at the positions from the transition point PA to the landing point LP are defined. The landing planner  101 C outputs the approach course plan and the grounding course plan to the attitude planner  101 D. 
     The attitude planner  101 D generates airframe control information depending on the flight course plan applied from the flight planner  101 B and the approach course plan and the grounding course plan applied from the landing planner  101 C. The attitude planner  101 D generates, for example, airframe control information of the drone  1 A for causing the drone  1 A to reach positions and speeds (specifically ground speeds in all directions) at the positions defined in the flight course plan. The attitude planner  101 D determines, for example, airframe control information including attitudes, vertical accelerations, and the like in consideration of differences in positions and speeds of the airframes according to the flight course plan. 
     Further, the attitude planner  101 D generates, for example, airframe control information of the drone  1 A for causing the drone  1 A to reach positions and speeds (specifically ground speeds in all directions) at the positions defined in the approach course plan. In addition, the attitude planner  101 D generates, for example, airframe control information of the drone  1 A for causing the drone  1 A to reach positions, vertical speeds at the positions, and attitudes defined in the grounding course plan. The attitude planner  101 D outputs the airframe control information to the airframe control unit  102 . Meanwhile, the attitude planner  101 D generates, for example, airframe control information for controlling attitudes of the drone  1 A such that attitudes assigned according to the grounding course plan are realized without correcting horizontal positions and horizontal speeds of the airframe of the drone  1 A according to the grounding course plan. 
     The airframe control unit  102  performs control in response to the airframe control information supplied from the attitude planner  101 D. The airframe control unit  102  controls rotation speeds of motors included in the drone  1 A such that the drone  1 A has attitudes and speeds according to the airframe control information. 
     The sensor unit  103  is named with a generic term for a plurality of sensors for acquiring airframe information of the drone  1 A (e.g., a current position, speeds, attitudes, and the like of the drone  1 A). Sensors constituting the sensor unit  103  may include a GPS, an SLAM sensor, an acceleration sensor, a gyro sensor, an atmospheric pressure sensor, and the like. 
     The airframe information acquisition unit  104  appropriately converts sensing data input from the sensor unit  103  from analog data into digital data. Then, the airframe information acquisition unit  104  outputs the sensing data converted into the digital data to the control unit  101 . 
     The wind information acquisition unit  105  acquires wind information and outputs the acquired wind information to the control unit  101 . Since specific examples of wind information estimation methods have been described, repeated description is omitted. 
     The communication unit  106  allows the drone  1 A to communicate with other apparatuses. The communication unit  106  includes a modulation/demodulation circuit and the like according to a communication method. The communication unit  106  performs, for example, communication with a ground station GS. According to such communication, for example, wind information transmitted from the ground station GS is received by the communication unit  106 . The communication unit  106  outputs the received wind information to the control unit  101 . 
     [Flow of Processing] 
       FIG. 8  is a flowchart illustrating a flow of processing performed in the drone  1 A according to the first embodiment. 
     The flight status management unit  101 A determines landing in step ST 101 . As described above, the flight status management unit  101 A determines landing according to instruction from a remote controller, completion of an assigned task, reduction in the remaining capacity of a battery, malfunction of a sensor included in the drone  1 , occurrence of communication failure, or the like. Although not shown, the drone  1 A is flying on the basis of a flight course plan according to the flight planner  101 B before step ST 101 . Then, processing proceeds to step ST 102 . 
     The flight status management unit  101 A switches planners from the flight planner  101 B to the landing planner  101 C in step ST 102 . In addition, the flight status management unit  101 A applies coordinates of a landing point LP to the landing planner  101 C. Then, processing proceeds to step ST 103 . 
     In step ST 103 , the landing planner  101 C acquires wind information. The wind information may be estimated by the drone  1 A or transmitted from the ground station GS. Then, the landing planner  101 C generates a grounding course plan from the acquired wind information. Specifically, the landing planner  101 C sets a horizontal ground speed of the drone  1 A on the basis of the acquired wind information and determines a position of a transition point PA on the basis of the horizontal ground speed. A specific method of setting a horizontal ground speed has been described above. In addition, the landing planner  101 C generates a grounding course plan including an attitude (horizontal in the present example) at the transition point PA, chronological positions from the transition point PA to the landing point LP, vertical accelerations at the positions, and the like. Then, processing proceeds to step ST 104 . 
     In step ST 104 , the landing planner  101 C generates an approach course plan from a current position to the transition point PA such that the position of the transition point PA and a speed of the drone  1 A at the transition point PA correspond to the horizontal ground speed determined in step ST 103 . Then, processing proceeds to step ST 105 . 
     In step ST 105 , the landing planner  101 C provides the approach course plan to the attitude planner  101 D. Then, processing proceeds to step ST 106 . 
     In step ST 106 , the attitude planner  101 D generates airframe control information based on the approach course plan before the transition point PA. The drone  1 A moves to a position defined in the approach course plan according to the airframe control unit  102  operating on the basis of the generated airframe control information. Further, the motors of the drone  1 A rotates to reach a speed defined in the approach course plan according to the airframe control unit  102  operating on the basis of the generated airframe control information. Then, processing proceeds to step ST 107 . 
     In step ST 107 , it is determined that an airframe height has reached the height of the transition point PA. For example, the flight status management unit  101 A determines that the airframe height of the drone  1 A has reached the height of the transition point PA on the basis of sensing data input from the sensor unit  103 . The flight status management unit  101 A notifies the landing planner  101 C that the airframe height of the drone  1 A has reached the height of the transition point PA. The landing planner  101 C that has received the notification provides the grounding course plan generated in step ST 103  to the attitude planner  101 D. Then, processing proceeds to step ST 108 . 
     In step ST 108 , the attitude planner  101 D generates airframe control information based on the grounding course plan. The grounding course plan in the present example is information for causing an attitude to be horizontal and information about vertical accelerations. Accordingly, the attitude planner  101 D that has received the grounding course plan generates airframe control information for maintaining the attitude of the drone  1 A horizontal after passing through the transition point PA and airframe control information including vertical speeds. Then, the attitude planner  101 D outputs the generated airframe control information to the airframe control unit  102 . The drone  1 A descends at a predefined speed while maintaining the attitude thereof horizontal according to the airframe control unit  102  operating on the basis of the airframe control information. Then, processing proceeds to step ST 109 . 
     In step ST 109 , the landing planner  101 C instructs the attitude planner  101 D to cause propellers of the drone  1 A to enter an idle state while checking landing of the drone  1 A. The attitude planner  101 D generates airframe control information based on such instruction. The attitude planner  101 D outputs the generated airframe control information to the airframe control unit  102 . The propellers of the drone  1 A enter an idle state according to the airframe control unit  102  operating on the basis of the airframe control information. The idle state means a state in which the propellers of the drone  1 A are rotated at a predetermined rotation speed or less (a degree of rotation speed at which the airframe of the drone  1 A does not ascend). When the propellers of the drone  1 A enter the idle state, a user can confirm that the drone  1 A is not destroyed. Meanwhile, the propellers of the drone  1 A may stop instead of entering the idle state. 
     According to the above-described first embodiment, a horizontal ground speed is assigned to the drone  1 A in advance at the transition point PA such that a horizontal ground speed at the time of landing becomes 0 or approximately 0. Furthermore, the attitude of the drone  1 A is controlled to be horizontal after the transition point PA. Accordingly, it is possible to stably land the drone  1 A. 
     Second Embodiment 
     Next, a second embodiment will be described. In description of the second embodiment, the same reference numerals are given to the same or homogeneous components as the above-described components and repeated description will be appropriately omitted. The matters described in the first embodiment can be applied to the second embodiment unless otherwise mentioned. 
       FIG. 9  is a block diagram illustrating a configuration example of a drone (hereinafter appropriately referred to as a drone  1 B) according to a second embodiment. The drone  1 B differs from the drone  1 A in that the drone  1 B does not include the wind information acquisition unit  105  and the control unit  101  includes a wind measurement planner  101 E with respect to the configuration. 
     The wind measurement planner  101 E generates a course plan for acquiring wind information. The wind measurement planner  101 E outputs the generated course plan to the attitude planner  101 D. The attitude planner  101 D generates airframe control information for causing the drone  1 B to move along the course plan supplied from the wind measurement planner  101 E or causing the speed of the drone  1 B to become a speed according to the course plan. The attitude planner  101 D outputs the generated airframe control information to the airframe control unit  102 . The course plan generated by the wind measurement planner  101 E is realized according to the airframe control unit  102  operating on the basis of the airframe control information. 
       FIG. 10  is a flowchart illustrating a flow of processing performed in the drone  1 B. In step ST 101 , the flight status management unit  101 A determines landing as in the first embodiment. Then, processing proceeds to step ST 201 . 
     In step ST 201 , the flight status management unit  101 A switches planners from the flight planner  101 B to the wind measurement planner  101 E. Then, processing proceeds to step ST 202 . 
     In step ST 202 , the wind measurement planner  101 E measures the wind and generates a course plan for acquiring wind information. The course plan for acquiring wind information is, for example, information in which chronological positions of the drone  1 B, attitudes and speeds at the positions are defined. Then, processing proceeds to step ST 203 . 
     In step ST 203 , the wind measurement planner  101 E sends the course plan generated thereby to the attitude planner  101 D. Then, processing proceeds to step ST 204 . 
     In step ST 204 , the attitude planner  101 D generates airframe control information for realizing the course plan that is planned by the wind measurement planner  101 E, specifically, a flight position, an attitude and a speed at the flight position. Then, the attitude planner  101 D sends the airframe control information to the airframe control unit  102 . The drone  1 B flies according to the airframe control unit  102  operating on the basis of the airframe control information. Then, processing proceeds to step ST 205 . 
     In step ST 205 , the wind measurement planner  101 E estimates wind information using a known method, for example, on the basis of differences between the course plan for acquiring wind information and positions of the actual drones  1 B. 
     Subsequently to processing of step ST 205 , processing pertaining to steps ST 102  to ST 109  is performed. Since the details of processing pertaining to steps ST 102  to ST 109  have already been described, repeated descriptions will be omitted. 
     According to the above-described second embodiment, the drone  1 B can autonomously generate a course plan for acquiring wind information and acquire the wind information according to the course plan. 
     Third Embodiment 
     Next, a third embodiment will be described. In description of the third embodiment, the same reference numerals are given to the same or homogeneous components as the above-described components and repeated description will be appropriately omitted. Further, the matters described in the first and second embodiments can be applied to the second embodiment unless otherwise mentioned. 
     The same as the configuration of the drone  1 A described in the first embodiment can be applied as a configuration of a drone (hereinafter appropriately referred to as a drone  1 C) according to the third embodiment. Although an attitude (horizontal) after the transition point PA is provided as a grounding course plan in the first embodiment, the third embodiment differs from the first embodiment in that a horizontal ground speed from the transition point PA to the landing point LP is provided as a grounding course plan. 
       FIG. 11  is a flowchart illustrating a flow of processing performed in the drone  1 C. The details of processing pertaining to steps ST 101  to ST 104  have already been described, and thus repeated descriptions will be omitted. Meanwhile, a horizontal ground speed at the transition point PA and a horizontal ground speed at each position from the transition point PA to the landing point LP are defined in the grounding course plan generated in step ST 103  in the present embodiment. 
     In step ST 301  following step ST 104 , the landing planner  101 C integrates the grounding course plan and the approach course plan. Then, processing proceeds to step ST 301 . 
     In step ST 302 , the landing planner  101 C provides the integrated course plan to the attitude planner  101 D. Then, processing proceeds to step ST 303 . 
     In step ST 303 , the attitude planner  101 D generates airframe control information for realizing the course plan provided thereto from the landing planner  101 C. Then, the attitude planner  101 D outputs the generated airframe control information to the airframe control unit  102 . The drone  1 C reaches positions, attitudes at the positions, and horizontal ground speeds according to the course plan integrated by the landing planner  101 C according to the airframe control unit  102  operating in response to the airframe control information. Then, processing proceeds to step ST 109 . The details of step ST 109  have already been described, and thus repeated descriptions will be omitted. 
     As described above, according to the third embodiment, it is possible to land the drone  1 C in a stable attitude by assigning horizontal ground speeds from the transition point PA to the landing point LP to the drone  1 C. 
     Fourth Embodiment 
     Next, a fourth embodiment will be described. In description of the fourth embodiment, the same reference numerals are given to the same or homogeneous components as the above-described components and repeated description will be appropriately omitted. The matters described in the first to third embodiments can be applied to the fourth embodiment unless otherwise mentioned. 
       FIG. 12  is a block diagram illustrating a configuration example of a drone (hereinafter appropriately referred to as a drone  1 D) according to the fourth embodiment. The drone  1 D differs from the drone  1 A in that it includes a go-around planner  101 F. The go-around planner  101 F is a planner that stops landing and causes the drone  1 D to ascend to a safe height when an attitude and a horizontal ground speed of the drone  1 D at the time of landing do not fall in allowable ranges. 
       FIG. 13  is a flowchart illustrating a flow of processing performed in the drone  1 D. The details of processing pertaining to steps ST 101  to ST 104  and processing pertaining to ST 301  to ST 303  have already been described, and thus repeated descriptions will be omitted. Subsequently to processing of step ST 303 , processing proceeds to step ST 401 . 
     In step ST 401 , it is determined whether the airframe of the drone  1 D is above the transition point PA, specifically, the height of the airframe of the drone  1 D becomes the transition point PA or lower. Such determination is performed, for example, by the flight status management unit  101 A on the basis of sensing data acquired by the sensor unit  103 . When the airframe of the drone  1 D is not above the transition point PA, processing returns to step ST 303 . When the airframe of the drone  1 D is not above the transition point PA, processing proceeds to step ST 402 . 
     In step ST 402 , it is determined whether the drone  1 D has grounded. Such determination is performed, for example, by the flight status management unit  101 A on the basis of sensing data acquired by the sensor unit  103 . When the flight status management unit  101 A determines that the drone  1 D has grounded, processing proceeds to step ST 403 . 
     In step ST 403 , the flight status management unit  101 A notifies the landing planner  101 C that the airframe of the drone  1 D has grounded. The landing planner  101 C that has received notification instructs the attitude planner  101 D to cause propellers of the drone  1 A to enter an idle state. The attitude planner  101 D generates airframe control information based on such instruction. The attitude planner  101 D outputs the generated airframe control information to the airframe control unit  102 . The propellers of the drone  1 A enter an idle state according to the airframe control unit  102  operating on the basis of the airframe control information. As described above, the idle state means a state in which the propellers of the drone  1 A are rotated at a predetermined rotation speed or less (a degree of rotation speed at which the airframe of the drone  1 A does not ascend). 
     When it is determined that the drone  1 D has not grounded in determination processing of step ST 402 , processing proceeds to step ST 404 . 
     In step ST 404 , it is determined whether inclination and a horizontal ground speed of the airframe of the drone  1 D fall in allowable ranges. Such determination is performed, for example, by the flight status management unit  101 A on the basis of sensing data acquired by the sensor unit  103 . Specifically, the flight status management unit  101 A determines whether inclination of the airframe is a threshold value or less and determines that the inclination of the airframe falls in an allowable range if the inclination of the airframe is the threshold value or less. In addition, the flight status management unit  101 A determines whether a difference between a current horizontal ground speed and a horizontal ground speed defined in the course plan is a threshold value or less and determines that the current horizontal ground speed falls in an allowable range if the difference is the threshold value or less. 
     If it is determined that the inclination and the horizontal ground speed of the airframe of the drone  1 D fall in the allowable ranges, processing returns to step ST 303 . If it is determined that the inclination and the horizontal ground speed of the airframe of the drone  1 D do not fall in the allowable ranges, processing proceeds to step ST 405 . 
     In step ST 405 , the flight status management unit  101 A switches planners from the landing planner  101 C to the go-around planner  101 F. The go-around planner  101 F performs control of stopping landing because the inclination and the horizontal ground speed of the airframe of the drone  1 D do not fall in the allowable ranges. Specifically, the go-around planner  101 F generates a course plan for causing the drone  1 D to ascend to a safe height. The go-around planner  101 F outputs the generated course plan to the attitude planner  101 D. Then, processing proceeds to step ST 406 . 
     In step ST 406 , the attitude planner  101 D generates airframe control information for realizing the course plan provided from the go-around planner  101 F. Then, the attitude planner  101 D outputs the generated airframe control information to the airframe control unit  102 . The drone  1 D ascends to a safe height according to the airframe control unit  102  controlling rotation speeds of the motors and the like depending on the airframe control information. Then, processing proceeds to step ST 407 . 
     In step ST 407 , the drone  1 D that has ascended to the safe height enters a standby state. The flight status management unit  101 A of the drone  1 D performs, for example, control of resuming a landing sequence (e.g., the above-described processing of steps ST 101  to ST 104  and processing of steps ST 301  and ST 302 ) for landing the drone  1 D again. The drone  1 D may wait for an instruction from a user. 
     Meanwhile, although it is determined whether the inclination and the horizontal ground speed of the airframe of the drone  1 D fall in the allowable ranges in the present embodiment, it may be determined whether any of the inclination and the horizontal ground speed falls in an allowable range or it may be determined whether other parameters fall in allowable ranges. 
     According to the above-described fourth embodiment, it is possible to cause the drone  1 D to ascend to a safe height when the inclination and the horizontal ground speed of the airframe differ from a plan. Accordingly, it is possible to prevent the drone  1 D from failing to land when the drone  1 D performs landing operation in an inappropriate attitude. 
     Modified Examples 
     Although embodiments of the present disclosure have been described above in detail, the content of the present disclosure is not limited to the above-described embodiments and various modifications based on the technical spirit of the present disclosure can be made. Hereinafter, modified examples will be described. 
     Although a configuration in which the control unit includes a plurality of planners has been described in consideration of convenience of description in each embodiment, the present disclosure is not limited thereto. For example, the flight planner and the landing planner may be configured as a single functional block. 
     A known control method for drones can be applied to the drone in each embodiment. 
     The present disclosure can also be realized by a device, a method, a program, a system, or the like. For example, by allowing a program that has the functions described in the above-described embodiments to be downloadable and allowing a device that has no functions described in the embodiments to download and install the program, it is possible to perform the control described in the embodiment in the device. The present disclosure can also be realized by a server that distributes the program. In addition, the present disclosure can also be realized as a tool that easily creates a flight plan described in the embodiments. The matters described in each embodiment and the modification examples can be appropriately combined. 
     Note that the advantageous effect described here is not necessarily limiting, and any advantageous effects described in the present disclosure may be achieved. Further, interpretation of the content of the present disclosure should not be limited by the exemplified advantageous effect. 
     The present disclosure can also employ the following configurations. 
     (1) 
     A flying body including a control unit configured to set a horizontal ground speed on the basis of wind information including information about a wind direction and a wind speed. 
     (2) 
     The flying body according to (1), wherein the wind information includes information about wind that affects flight of the flying body. 
     (3) 
     The flying body according to (1) or (2), wherein the flying body includes a plurality of motors, and 
     wherein the control unit controls rotation speeds of the plurality of motors to become the set horizontal ground speed. 
     (4) 
     The flying body according to any one of (1) to (3), wherein the horizontal ground speed set by the control unit becomes approximately 0 at a landing point. 
     (5) 
     The flying body according to any one of (1) to (4), wherein the control unit controls the rotation speeds of the motors to become the set horizontal ground speed at a point positioned above the landing point. 
     (6) 
     The flying body according to (5), wherein the control unit controls an attitude to become approximately horizontal at the point positioned above the landing point. 
     (7) 
     The flying body according to (5) or (6), wherein the point positioned above the landing point is a point at which a landing operation starts. 
     (8) 
     The flying body according to (7), wherein the control unit performs control of causing an airframe to ascend when at least one of an inclination of the airframe and a horizontal ground speed exceeds an allowable range, during an event from the point at which the landing operation starts to the landing point. 
     (9) 
     The flying body according to any one of (5) to (8), wherein the point positioned above the landing point is determined on the basis of at least the horizontal ground speed. 
     (10) 
     The flying body according to any one of (1) to (9), including a wind information acquisition unit configured to acquire the wind information. 
     (11) 
     The flying body according to (10), wherein the flying body includes a sensor unit, and the wind information acquisition unit calculates and acquires the wind information on the basis of a difference between sensing data acquired by the sensor unit and a motor output. 
     (12) 
     The flying body according to (10), wherein the wind information acquisition unit acquires the wind information from an external apparatus. 
     (13) 
     A control method in a flying body, including setting, by a control unit, a horizontal ground speed on the basis of wind information including information about a wind direction and a wind speed. 
     (14) 
     A program causing a computer to execute a control method in a flying body, including setting, by a control unit, a horizontal ground speed on the basis of wind information including information about a wind direction and a wind speed. 
     REFERENCE SIGNS LIST 
     
         
           1 A,  1 B,  1 C,  1 D Drone 
           101  Control unit 
           101 A Flight status management unit 
           101 B Flight planner 
           101 C Landing planner 
           101 D Attitude planner 
           102  Airframe control unit 
           103  Sensor unit 
           105  Wind information acquisition unit 
           106  Communication unit