Patent Publication Number: US-9904285-B2

Title: Movement control method for autonomous mobile robot

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a movement control method and a movement control device, and particularly relates to a movement control method and a movement control device in a robot system made up of a plurality of autonomous mobile robots that execute tasks while moving autonomously. 
     2. Description of the Related Art 
     Techniques have been proposed in relation to an autonomous mobile robot (hereinafter referred to as an autonomous robot) that executes tasks assigned thereto while cooperating with other autonomous robots (for example, see Japanese Unexamined Patent Application Publication No. 2014-054335 and Japanese Patent No. 4713846). 
     Japanese Unexamined Patent Application Publication No. 2014-054335 discloses a technique in which a server assigns coverage regions to each of a plurality of cleaning robots, and causes the plurality of cleaning robots to perform cleaning. Japanese Patent No. 4713846 discloses a technique in which, in a system configured from a server and a plurality of autonomous robots, the plurality of autonomous robots receive instructions from the server and thereafter exchange information of one another to execute tasks while cooperating. 
     SUMMARY 
     The aforementioned conventional techniques do not take into consideration the case where other autonomous robots with which communication is possible dynamically change due to the autonomous robots moving. 
     One non-limiting and exemplary embodiment provides a movement control method and a movement control device with which it is possible for an autonomous robot to cooperate with a greater number of other autonomous robots to execute tasks even in the case where the other autonomous robots with which communication is possible dynamically change. 
     In one general aspect, the techniques disclosed here feature a movement control method in a robot system made up of a plurality of autonomous mobile robots that execute tasks with respect to coverage regions assigned respectively thereto, the movement control method including: selecting, when having completed a task with respect to a first coverage region assigned to a first robot from among the plurality of robots, a second robot as a support-target robot from within a robot group, which is made up of a plurality of robots other than the first robot that are within a communication range of the first robot from among the plurality of robots; starting to cause the first robot to move toward a second coverage region assigned to the selected second robot; determining, when a third robot from among the plurality of robots is newly within the communication range of the first robot while the first robot moving toward the second coverage region, whether to alter the support-target robot from the second robot to the third robot; and starting to cause the first robot, when having determined to alter the support-target robot from the second robot to the third robot, to move toward a third coverage region assigned to the third robot. 
     According to the present disclosure, it is possible to realize a movement control method and a movement control device with which it is possible for an autonomous robot to cooperate with a greater number of other autonomous robots to execute tasks even in the case where the other autonomous robots with which communication is possible dynamically change. 
     It should be noted that these comprehensive or specific aspects may be realized by a system, a method, an integrated circuit, a computer program, or a recording medium, and may be realized by an arbitrary combination of a system, a method, an integrated circuit, a computer program, and a recording medium. 
     Additional benefits and advantages of the disclosed embodiments will become apparent from the specification and drawings. The benefits and/or advantages may be individually obtained by the various embodiments and features of the specification and drawings, which need not all be provided in order to obtain one or more of such benefits and/or advantages. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a drawing conceptually depicting an overall view of a robot system in embodiment 1; 
         FIG. 2  is a block diagram depicting an example of the functional configuration of an autonomous robot in embodiment 1; 
         FIG. 3  is a block diagram depicting an example of the detailed configuration of a control unit depicted in  FIG. 2 ; 
         FIG. 4  is a drawing conceptually depicting information stored in a storage unit of an autonomous robot in embodiment 1; 
         FIG. 5  is a drawing depicting an example of other robot information depicted in  FIG. 4 ; 
         FIG. 6  is a flowchart for describing an operation of an autonomous robot in embodiment 1; 
         FIG. 7  is a flowchart for describing a detailed example of selection processing of an autonomous robot in embodiment 1; 
         FIG. 8  is a drawing conceptually depicting a situation in which an autonomous robot in embodiment 1 has newly detected an autonomous robot while moving toward a support-target autonomous robot; 
         FIG. 9  is a flowchart for describing a detailed example of alteration processing performed by an autonomous robot in embodiment 1; 
         FIG. 10  is a block diagram depicting an example of the functional configuration of an autonomous robot in embodiment 2; 
         FIG. 11  is a block diagram depicting an example of the detailed configuration of a control unit depicted in  FIG. 10 ; 
         FIG. 12  is a drawing conceptually depicting information stored in a storage unit of an autonomous robot in embodiment 2; 
         FIG. 13  is a drawing depicting an example of other robot information depicted in  FIG. 12 ; 
         FIG. 14A  is a drawing conceptually depicting a situation for autonomous robots that make up a robot system in embodiment 2; 
         FIG. 14B  is a drawing conceptually depicting a situation for autonomous robots that make up a robot system in embodiment 2; 
         FIG. 15  is a flowchart for describing a detailed example of selection processing of an autonomous robot in embodiment 2; 
         FIG. 16  is a block diagram depicting an example of the functional configuration of an autonomous robot in embodiment 3; 
         FIG. 17  is a block diagram depicting an example of the detailed configuration of a control unit depicted in  FIG. 16 ; 
         FIG. 18  is a drawing conceptually depicting information stored in a storage unit of an autonomous robot in embodiment 3; 
         FIG. 19  is a drawing depicting an example of other robot information depicted in  FIG. 18 ; 
         FIG. 20A  is a drawing conceptually depicting a situation for autonomous robots that make up a robot system in embodiment 3; 
         FIG. 20B  is a drawing conceptually depicting a situation for autonomous robots that make up a robot system in embodiment 3; 
         FIG. 21  is a flowchart for describing a detailed example of selection processing of an autonomous robot in embodiment 3; 
         FIG. 22  is a block diagram depicting an example of the functional configuration of an autonomous robot in embodiment 4; 
         FIG. 23  is a block diagram depicting an example of the detailed configuration of a control unit depicted in  FIG. 22 ; 
         FIG. 24A  is a drawing conceptually depicting a situation for autonomous robots that make up a robot system in embodiment 4; 
         FIG. 24B  is a drawing conceptually depicting a situation for autonomous robots that make up a robot system in embodiment 4; and 
         FIG. 25  is a drawing depicting an example of a movement direction for when movement is performed to outside of a coverage region of an autonomous robot in modified example 1 of embodiment 4. 
     
    
    
     DETAILED DESCRIPTION 
     (Findings Forming the Basis for the Present Disclosure) 
     Japanese Unexamined Patent Application Publication No. 2014-054335 discloses a technique in which a server controls a plurality of cleaning robots and causes the plurality of cleaning robots to perform cleaning while cooperating. More specifically, in the technique disclosed in Japanese Unexamined Patent Application Publication No. 2014-054335, the server assigns coverage regions to each of the plurality of cleaning robots and causes the plurality of cleaning robots to perform cleaning. The cleaning robots notify the progress status of the cleaning to the server while cleaning the coverage regions assigned from the server. The server receives notifications from the cleaning robots and thereby comprehends the task progress status of the cleaning robots. In the case where a notification that cleaning has been completed is received from one cleaning robot, the server performs a reassignment in which an uncleaned region from within the coverage region of another robot that has not yet completed cleaning is assigned to the aforementioned one robot. 
     However, the technique disclosed in Japanese Unexamined Patent Application Publication No. 2014-054335 is a configuration in which a server is used to allow cleaning robots to cooperate. Therefore, it is necessary to construct a server for allowing the plurality of cleaning robots to cooperate, and there are costs for constructing a server. In addition, in the case where the server becomes inoperative due to a malfunction or the like, there is a problem in that reassignment or the like cannot be performed with respect to the cleaning robots, and the plurality of cleaning robots cannot be made to cooperate appropriately. Furthermore, in the case where the communication between the server and a cleaning robot has been interrupted, the server is no longer able to comprehend the task progress status of the cleaning robot with which communication has been interrupted. Therefore, the server is no longer able to make the plurality of cleaning robots cooperate appropriately. 
     In light of the above, a method is required in which a plurality of cleaning robots, namely autonomous robots, are made to cooperate without employing central control in which a central device such as a server is used. In other words, a method is required in which the entirety of a system made up of a plurality of autonomous robots is made to cooperate by each autonomous robot cooperating with surrounding autonomous robots while mutually exchanging information with the surrounding autonomous robots. 
     Then, if such a configuration can be realized, a central device to comprehend the entirety of the system does not have to be employed, and it is therefore not necessary to construct the central device and costs for constructing the central device can be limited. In addition, even if one autonomous robot becomes inoperative due to a malfunction or the like, there is no effect whatsoever on the cooperation among the other autonomous robots, and therefore there are no cases where cooperative operations no longer function across the entirety of the system. Naturally, in the case where a cooperative operation was being performed with the autonomous robot that has malfunctioned, there is an effect on the autonomous robot that was performing the cooperative operation and the like. However, that effect is a local effect when viewed from the entirety of the system, and the entirety of the system is not affected. 
     Japanese Patent No. 4713846 discloses a system configuration in which it is not necessary to construct a central device. Japanese Patent No. 4713846 discloses a method in which the entirety of a system is made to cooperate by each autonomous robot cooperating with surrounding autonomous robots while mutually exchanging information with the surrounding autonomous robots, rather than cooperation by means of central control in which a server or the like is used. Japanese Patent No. 4713846 discloses a system configured from a server and a plurality of autonomous robots; however, the plurality of autonomous robots merely receive instructions from the server, and after having received the instructions from the server, the plurality of autonomous robots exchange information of one another to execute tasks while cooperating. When cooperating with other autonomous robots to execute tasks, the plurality of autonomous robots in Japanese Patent No. 4713846 communicate with other autonomous robots within a communication range, exchange location information, task progress information, and the like with each other, and cooperate with each other to execute tasks on the basis of that information. 
     However, when an autonomous robot such as a cleaning robot moves, the communication range of the cleaning robot changes. Therefore, there are cases where the other autonomous robots with which the autonomous robot can communicate change due to the movement of the autonomous robot. In these cases, due to the autonomous robot moving, the information of the other autonomous robots that can be acquired by the autonomous robot changes. 
     For example, although communication had been possible with a certain autonomous robot A before the movement, due to the movement of the autonomous robot, there are cases where communication is no longer possible after the movement. In these cases, the autonomous robot cannot acquire the information of the autonomous robot A. Furthermore, for example, although communication was not possible with another autonomous robot B before the movement, due to the movement of the autonomous robot, there are also cases where communication becomes possible after the movement. In these cases, the autonomous robot becomes able to newly acquire the information of the autonomous robot B. 
     In the case of a method in which each autonomous robot cooperates with surrounding autonomous robots while exchanging information of one another, each autonomous robot uses only the information of surrounding autonomous robots to perform cooperation. That is, each autonomous robot is not able to use the information of all of the autonomous robots making up the system, and uses only the information of surrounding autonomous robots to perform cooperation. Therefore, the autonomous robots are not always able to perform optimum cooperation when viewed from the entirety of the system. In order to perform more suitable cooperation, it is desirable that each autonomous robot use the information of a greater number of autonomous robots to perform cooperation. In particular, in the case where an autonomous robot moves in the manner of a cleaning robot, due to the movement of the autonomous robot, the information of other autonomous robots that can be acquired by the autonomous robot dynamically changes, and therefore, taking this into consideration, it is desirable that the information of a greater number of other autonomous robots be used to perform more suitable cooperation. 
     However, in Japanese Patent No. 4713846, there is no suggestion whatsoever regarding dynamic changes in the information of other autonomous robots that can be acquired by an autonomous robot, caused by the movement of the autonomous robot. In Japanese Patent No. 4713846, it is assumed that all of the autonomous robots are able to communicate with each other, and it is thought that no consideration whatsoever is given to the communication range of an autonomous robot changing and the information of other autonomous robots that can be acquired by the autonomous robot changing due to the movement of the autonomous robot. 
     Thus, hereinafter, a proposal is given regarding a movement control method and a movement control device with which it is possible for an autonomous robot to cooperate with a greater number of other autonomous robots to execute tasks even in the case where the other autonomous robots with which communication is possible dynamically change. 
     A movement control method according to a mode of the present disclosure is a movement control method in a robot system made up of a plurality of autonomous mobile robots that execute tasks with respect to coverage regions assigned respectively thereto, the movement control method including: selecting, when having completed a task with respect to a first coverage region assigned to a first robot from among the plurality of robots, a second robot as a support-target robot from within a robot group, which is made up of a plurality of robots other than the first robot that are within a communication range of the first robot from among the plurality of robots; starting to cause the first robot to move toward a second coverage region assigned to the selected second robot; determining, when a third robot from among the plurality of robots is newly within the communication range of the first robot while the first robot moving toward the second coverage region, whether to alter the support-target robot from the second robot to the third robot; and starting to cause the first robot, when having determined to alter the support-target robot from the second robot to the third robot, to move toward a third coverage region assigned to the third robot. 
     Thus, the first robot, which has completed a task with respect to an assigned coverage region, is able to perform support-target alteration processing on the basis of information from the third robot, with which communication has become newly possible when moving toward the second robot that is a support target, namely a task-support target, and therefore the first robot is able to select a more appropriate robot as a support target. That is, it is possible for an autonomous robot to cooperate with a greater number of autonomous robots to execute tasks even in the case where the other autonomous robots with which communication is possible dynamically change. In this way, it is possible to realize a movement control method with which it is possible to coordinate with other autonomous robots to execute tasks more efficiently. 
     Here, the first robot may acquire third robot information that includes location information indicating the current location of the third robot and task information indicating a task progress status of the third robot, and, in the determining, the first robot may use the acquired third robot information to determine whether to alter the support-target robot from the second robot to the third robot. 
     Furthermore, in the determining, the first robot may determine to alter the support-target robot from the second robot to the third robot when the time at which the third robot will complete a task with respect to the third coverage region is later than the time at which the second robot will complete a task with respect to the second coverage region and there will be a remaining task for the third robot at the point in time at which the first robot will have moved from the current location thereof to the current location of the third robot. 
     Furthermore, when the first robot starts moving toward the second coverage region, the first robot may notify the second robot of information indicating that the first robot is moving thereto to provide support for completing the task for the second coverage region, and, when the first robot starts moving toward the third coverage region, the first robot may notify the third robot of information indicating that support for completing the task for the third coverage region is to be provided, and also notify the second robot of information indicating that the first robot is not moving thereto to provide support for the second robot. 
     The first robot is thereby able to notify the second robot, with which communication is possible with the first robot, that the first robot is no longer moving thereto to provide task support. 
     It thereby becomes possible for the second robot, when having completed its own tasks and performing selection processing for a support-target robot, to take into consideration that the first robot is no longer coming to provide support. 
     Furthermore, the first robot, when it has become newly possible to communicate with an M th  robot (M being a natural number of 3 or more) from among the plurality of robots while moving toward an N th  coverage region (N being a natural number of 3 or more) that includes the third coverage region but not the first coverage region, may determine whether to alter the support-target robot to the M th  robot, and the first robot, when having determined to alter the support-target robot to the M th  robot, may start to move toward an M th  coverage region assigned to the M th  robot. 
     Here, the first robot may have a memory that stores frequency information indicating a frequency limit that is the number of times that the support-target robot can be altered, and, in the alteration determination step, the first robot may determine not to alter the support-target robot to the M th  robot when the number of times that the support-target robot has been altered has exceeded the frequency limit indicated in the frequency information stored in the memory. 
     It thereby becomes possible to limit an increase in the time taken for the first robot to arrive at the coverage region of the support-target robot and there being less time for supporting the support-target robot due to the support-target robot being altered numerous times. 
     Furthermore, the first robot may receive robot information, which includes location information indicating a current location and task information indicating a task progress status, from each robot of the robot group, the first robot may use the current location of the first robot and the received robot information of each robot of the robot group to acquire the remaining tasks of each robot for a point in time at which the first robot will have moved to the current location of each robot of the robot group; and, in the selecting, the first robot may select the second robot as the support-target robot from within the robot group on the basis of the acquired remaining tasks. 
     The first robot is thereby able to acquire the remaining tasks of each robot of the robot group, and is therefore able to select the support-target robot on the basis of the acquired remaining tasks. It is thereby possible to prevent the tasks of the support-target robot being completed while the first robot is moving toward the support-target robot, and the movement being rendered unnecessary. 
     Furthermore, the first robot may have a memory for storing the robot information of each robot of the robot group received while executing the task with respect to the first coverage region, the robot information of each robot of the robot group may further include time information indicating the time at which the robot information has been received by the first robot, the first robot may move within the first coverage region when the first robot has received at least one item of robot information from among the robot information of each robot of the robot group stored in the memory, outside of a prescribed period that is based on the point in time at which the task with respect to the first coverage region has been completed, in the receiving, in addition, the first robot may once again receive the robot information from the robot corresponding to the at least one item of robot information when it has become possible for the first robot to communicate with the robot corresponding to the at least one item of robot information while moving within the first coverage region, and, in the acquiring of the remaining tasks, the remaining tasks of each robot of the robot group may be acquired based on the robot information that has been received once again. 
     The first robot is thereby able to select a support-target robot using robot information that is received immediately before or immediately after completing the task for the coverage region thereof, and therefore becomes able to appropriately select a support-target robot. 
     Furthermore, the memory may have additionally stored therein reception location information indicating the location of the first robot when the first robot received the robot information of each robot of the robot group received while executing the task with respect to the first coverage region, and the first robot may move within the first coverage region toward the location indicated by the reception location information corresponding to the at least one item of robot information. 
     The first robot is thereby able to acquire even more robot information by moving within the coverage region thereof, and therefore becomes able to appropriately select a support-target robot. 
     More specifically, the first robot, when moving within the coverage region to newly acquire robot information, moves toward a location at which corresponding robot information has been previously received. The first robot is thereby able to communicate with the robot of said robot information more quickly, and therefore becomes able to select a support-target robot more quickly. 
     Furthermore, the first robot may have a memory for storing the robot information of each robot of the robot group received while executing the task with respect to the first coverage region, the robot information of each robot of the robot group may further include time information indicating the time at which the robot information has been received by the first robot, in the selecting, the support-target robot may be selected from within a robot group, which is a plurality of robots other than the first robot with which communication is currently possible and has been possible in the past with the first robot from among the plurality of robots, and, in the acquiring of the remaining tasks, in addition, the robot information and time information, stored in the memory, of at least one robot from among the plurality of robots with which communication has been possible in the past with the first robot and the current location of the first robot may be used to estimate the remaining tasks of the at least one robot for a point in time at which the first robot will have moved to the at least one robot, thereby acquiring the remaining tasks of each robot of the robot group including the at least one robot. 
     The first robot is thereby able to accurately estimate the remaining tasks of each robot of the robot group, and is therefore able to appropriately select a support-target robot. 
     Furthermore, when the first robot has completed the task with respect to the first coverage region and is not able to select the support-target robot from within the robot group while present within the first coverage region, the first robot may move to outside of the first coverage region, when it has become possible for the first robot to communicate with a robot not included in the robot group, from among the plurality of robots while moving to outside of the first coverage region, the first robot may receive robot information, which includes location information indicating a current location and task information indicating a task progress status, from the robot not included in the robot group, the first robot may use the current location of the first robot and the received robot information of the robot not included in the robot group to acquire the remaining tasks for the point in time at which the first robot will have moved to the current location of the robot not included in the robot group, and the first robot may select the robot not included in the robot group as the support-target robot on the basis of the remaining tasks acquired in the remaining task acquisition step. 
     Thus, by moving to outside of the coverage region, the first robot is able to establish, as a communication range, a new region that up to that point in time had been outside of the communication range, and becomes able to communicate with new other robots with which communication had not been possible up to that point in time. The first robot is thereby able to acquire robot information from the new other robot, and therefore becomes able to select a support-target robot. 
     Furthermore, in the acquiring of the remaining tasks, the first robot may use the current location of the first robot and the received location information of each robot of the robot group to calculate movement times to the current locations of each robot of the robot group, and may use the calculated movement times and the received task information of each robot of the robot group to estimate the amount of remaining tasks of each robot, thereby acquiring the remaining tasks of each robot. 
     Furthermore, in the selecting, the first robot may select the second robot having the largest amount of remaining tasks acquired in the remaining task acquisition step, from within the robot group, as the support-target robot. 
     It is thereby possible for the second robot having, as a selection standard, the largest amount of estimated remaining tasks to be selected as the support-target robot, and it therefore becomes possible to select the robot that requires the most support. 
     Furthermore, a movement control device according to the present disclosure is a movement control device of a first robot in a robot system made up of a plurality of autonomous mobile robots that execute tasks with respect to coverage regions assigned respectively thereto, the movement control device including: one or more memories; and circuitry which, in operation, when a task with respect to a first coverage region assigned to the first robot has been completed, selects a second robot as a support-target robot from within a robot group, which is a plurality of robots other than the first robot that are within a communication range of the first robot, from among the plurality of robots, performs control that causes the first robot to start moving toward a second coverage region assigned to the selected second robot, when a third robot from among the plurality of robots is newly within the communication range of the first robot while the first robot moving toward the second coverage region, determines whether to alter the support-target robot from the second robot to the third robot, and, when having determined to alter the support-target robot from the second robot to the third robot, performs control that causes the first robot to start moving toward a third coverage region assigned to the third robot. 
     It should be noted that these comprehensive or specific aspects may be realized by a system, a method, an integrated circuit, a computer program, or a recording medium such as a computer-readable CD-ROM, and may be realized by an arbitrary combination of a system, a method, an integrated circuit, a computer program, or a recording medium. 
     Hereinafter, a movement control method and the like according to an aspect of the present disclosure will be described with reference to the drawings. 
     It should be noted that the embodiments described hereinafter all represent a specific example of the present disclosure. The numerical values, the shapes, the materials, the constituent elements, and the arrangement positions of the constituent elements and the like given in the following embodiments are examples and are not intended to restrict the present disclosure. Furthermore, constituent elements that are not described in the independent claims indicating the most significant concepts from among the constituent elements in the following embodiments are described as optional constituent elements. 
     Hereinafter, a description will be given with task coverage regions having been assigned in advance to each of a plurality of autonomous robots. 
     (Embodiment 1) 
     In the present embodiment, a description is given regarding a movement control method and the like implemented such that, in a situation in which a plurality of autonomous robots autonomously move within respective coverage regions to execute tasks, an autonomous robot that has completed tasks with respect to the assigned coverage region cooperates with another autonomous robot to execute tasks. 
     It should be noted that an autonomous robot cooperating with another autonomous robot to execute tasks means the autonomous robot, after having completed the tasks for the coverage region assigned thereto, provides support for the tasks of another autonomous robot that has not yet completed said tasks. Furthermore, support for the tasks means the autonomous robot executes a portion of the tasks of the other autonomous robot. This portion of the tasks is assigned to the autonomous robot from the other autonomous robot. 
     The autonomous robot is a cleaning robot, a search robot, an inspection robot, or the like. The tasks executed by the autonomous robot are the suction processing of garbage and dust in the case where the autonomous robot is a cleaning robot, sensing for searching for a target object such as a land mine in the case where the autonomous robot is a search robot, and sensing for confirming abnormalities of an inspection target such as a bridge or a building in the case where the autonomous robot is an inspection robot. 
     [Robot System Overview] 
       FIG. 1  is a drawing conceptually depicting an overall view of a robot system in embodiment 1. 
     A robot system  1  depicted in  FIG. 1  is made up of a plurality of autonomous mobile robots that execute tasks for respectively assigned coverage regions. In the present embodiment, the robot system  1  is made up of autonomous robots  11  to  19 . 
     Task coverage regions  21  to  29  are assigned in advance to the autonomous robots  11  to  19 , respectively. Each of the autonomous robots  11  to  19  moves autonomously within the preassigned coverage regions  21  to  29  to execute tasks. 
     Furthermore, each of the autonomous robots  11  to  19  has a communication function. In the present embodiment, the region in which communication is possible for each of the autonomous robots  11  to  19  is limited. Autonomous robots within a region in which communication is possible are able to exchange information with each other. For example, in  FIG. 1 , a communication range  311  is depicted as a region in which communication is possible for the autonomous robot  11 , and it is depicted that the autonomous robot  11  is able to communicate with the other autonomous robots  12 ,  13 , and  14  that are within the communication range  311 . 
     In the robot system  1  configured as described above, each autonomous robot executes tasks for a preassigned coverage region and also communicates with other neighboring autonomous robots that are within a communication range to exchange information with each other. 
     It should be noted that, as a method for allocating a coverage region for an autonomous robot, for example, a coverage region may be allocated to an autonomous robot before the autonomous robot starts a task. Furthermore, an autonomous robot to which a coverage region has not yet been assigned may issue a request to another autonomous robot to which a coverage region has already been assigned, for a portion of the coverage region of the other autonomous robot to be assigned to said autonomous robot. Furthermore, an autonomous robot may perform environment confirmation before starting a task, for the autonomous robot to set a coverage region itself. The assignment method is not restricted to the aforementioned methods as long as the autonomous robot has a coverage region before executing a task. 
     [Functional Configuration of Autonomous Robot] 
     The autonomous robots  11  to  19  are of the same type or are provided with at least the functional configuration depicted in  FIG. 2 . Hereinafter, the functional configuration of the autonomous robot  11  will be representatively described. 
       FIG. 2  is a block diagram depicting an example of the functional configuration of the autonomous robot  11  in embodiment 1. 
     As depicted in  FIG. 2 , the autonomous robot  11  is provided with at least a communication unit  111 , a control unit  112 , a task execution unit  113 , a driving unit  114 , a storage unit  115 , a time measurement unit  116 , and a location measurement unit  117 . 
     The communication unit  111  is an interface that uses a short-distance wireless communication technology such as Wi-Fi for communicating with other autonomous robots. The communication unit  111  transmits, to other autonomous robots, specific information relating thereto (the autonomous robot  11 ), task information relating to tasks thereof (the autonomous robot  11 ), and location information thereof, for example. Furthermore, the communication unit  111  receives information transmitted from other autonomous robots. It should be noted that the communication unit  111  is driven by a battery or the like in the autonomous robot  11 , and the region in which communication is possible is limited as described above. 
     The task execution unit  113  executes a task upon receiving an instruction from the control unit  112 . Here, in the case where the autonomous robot  11  is a cleaning robot for example, the task execution unit  113  is a garbage suction device for sucking up garbage. Furthermore, in the case where the autonomous robot  11  is a land mine search robot for example, the task execution unit  113  is a land mine sensing device for sensing land mines underground, and in the case where the autonomous robot  11  is an inspection robot for example, the task execution unit  113  is a sensor information collection device for sequentially acquiring information of sensors provided in advance in an inspection-target building. 
     The driving unit  114  is configured from a motor and wheels, and when an instruction is received from the control unit  112 , the motor is driven and the wheels are rotated, thereby driving the autonomous robot  11 . 
     The storage unit  115  stores local robot information made up of specific information relating to the autonomous robot  11  and task information relating to tasks of the autonomous robot  11 , and other robot information that is based on information transmitted from other robots. For example, the storage unit  115  stores frequency information indicating a frequency limit that is the number of times that a support-target robot can be altered. The storage unit  115  stores other information; however, the details thereof are described later on and a description thereof is therefore omitted here. 
     When time information is required, the time measurement unit  116  receives an instruction from the control unit  112  to perform a time measurement. For example, the time measurement unit  116  measures a task start time when the execution of a task of the autonomous robot  11  is started, and measures a task completion time when the execution of the task of the autonomous robot  11  is completed. 
     The location measurement unit  117  acquires location information for the autonomous robot  11 . For example, the location measurement unit  117  measures location information by means of a GPS. 
     The control unit  112  performs control for the aforementioned communication unit  111 , the task execution unit  113 , the driving unit  114 , the storage unit  115 , the time measurement unit  116 , and the location measurement unit  117 . 
     [Control Unit  112 ] 
     Here, an example of the detailed configuration of the control unit  112  will be described. 
       FIG. 3  is a block diagram depicting an example of the detailed configuration of the control unit depicted in  FIG. 2 . 
     As depicted in  FIG. 3 , the control unit  112  is provided with a selection processing unit  1121 , a movement control unit  1122 , an alteration determination unit  1123 , and a notification control unit  1124 . 
     In the case where a task with respect to a coverage region  21  (first coverage region) assigned to the autonomous robot  11  (first robot) has been completed, the selection processing unit  1121  selects a support-target robot from within a robot group, which is a plurality of autonomous robots other than the autonomous robot  11  (first robot) that are able to communicate with the autonomous robot  11  (first robot) from among the plurality of autonomous robots. 
     For example, first, the selection processing unit  1121  causes robot information, which includes location information indicating a current location and task information indicating a task progress status, to be received by the communication unit  111  from each robot of the robot group. Next, the selection processing unit  1121  uses the current location of the autonomous robot  11  (first robot) measured by the location measurement unit  117  and the plurality of items of robot information acquired by the communication unit  111  to acquire the remaining tasks of each robot of the robot group for a point in time at which the autonomous robot  11  (first robot) will have moved to the current location of each robot. The selection processing unit  1121  then selects a support-target robot (second robot) from within the robot group on the basis of the acquired remaining tasks. Here, for example, the selection processing unit  1121  may select the robot having the largest amount of remaining tasks acquired, from within the robot group, as the support-target robot. 
     In the case where it has become newly possible for the autonomous robot  11  (first robot) to communicate with a third robot from among the plurality of autonomous robots while moving to a second coverage region assigned to the support-target robot (second robot), the alteration determination unit  1123  performs processing to determine whether to alter the support-target robot from the second robot to the third robot. For example, the alteration determination unit  1123  causes the communication unit  111  to acquire third robot information, which includes location information indicating the current location of the third robot and task information indicating the task progress status of the third robot, and uses the acquired third robot information to determine whether to alter the support-target robot from the second robot to the third robot. 
     In addition, in the case where it has become newly possible for the autonomous robot  11  (first robot) to communicate with an M th  robot (M being a natural number of 3 or more) from among the plurality of autonomous robots while moving to an N th  coverage region (N being a natural number of 3 or more) that includes a third coverage region but not the coverage region  21  (first coverage region), the alteration determination unit  1123  determines whether to alter the support-target robot to the M th  robot. It should be noted that the alteration determination unit  1123  determines not to alter the support-target robot to the M th  robot in the case where the number of times that the support-target robot has been altered has exceeded the frequency limit indicated in the frequency information stored in the storage unit  115 . 
     The movement control unit  1122  performs control that causes the autonomous robot  11  (first robot) to start moving toward the second coverage region assigned to the support-target robot (second robot) selected by the selection processing unit  1121 . Furthermore, in the case where it is determined by the alteration determination unit  1123  that the support-target robot is to be altered from the second robot to the third robot, the movement control unit  1122  performs control that causes the first robot (autonomous robot  11 ) to start moving toward the third coverage region assigned to the third robot. Furthermore, in the case where the alteration determination unit  1123  has determined that the support-target robot is to be altered to the M th  robot, the movement control unit  1122  performs control that causes movement to be started toward an M th  coverage region assigned to the M th  robot. 
     When the first robot (autonomous robot  11 ) starts moving toward the second coverage region due to the movement control unit  1122 , the notification control unit  1124  performs control to notify the second robot with information indicating that the first robot is moving thereto to provide support for completing the tasks for the second coverage region. Furthermore, in the case where the alteration determination unit  1123  has determined that the support-target robot is to be altered to the third robot, when the first robot (autonomous robot  11 ) is made to start moving toward the third coverage region by the movement control unit  1122 , the notification control unit  1124  performs control to notify the third robot with information indicating that the first robot will provide support for completing the tasks for the third coverage region, and also notifies the second robot with information indicating that the first robot will not move thereto to support the second robot. 
     [Storage Unit  115 ] 
     Next, the information stored in the storage unit  115  of the autonomous robot  11  will be described in detail using the drawings. 
       FIG. 4  is a drawing conceptually depicting the information stored in the storage unit  115  of the autonomous robot  11  according to embodiment 1. 
     The storage unit  115  is provided with local robot information  1151 , other robot information  1152 , and a selection standard  1153 . 
     (Details of the Local Robot Information) 
     The local robot information  1151  is information relating to the autonomous robot  11  itself, and is made up of robot-specific information and task information. 
     The robot-specific information is made up of robot identification information for uniquely identifying the autonomous robot  11 , and specification information indicating the specifications of the autonomous robot  11 . Here, the information indicating the specifications of the autonomous robot  11  is, for example, information such as a movement speed for when the autonomous robot  11  moves and a task processing capability indicating a task processing amount per unit time. 
     The task information is information relating to tasks for the coverage region  21  assigned to the autonomous robot  11 . This task information is made up of region information, route information, a task start time, an expected task end time, task-complete region information, task-incomplete region information, and a task execution amount per unit time. 
     The region information is information indicating, for example, a map or the area of the task coverage region  21  assigned to the autonomous robot  11 . Here, the region information may be set in advance from the user, for example. Furthermore, the region information may be set by, for example, the autonomous robot  11  issuing a request to another autonomous robot to which a coverage region has already been assigned, for a portion of the coverage region of the other autonomous robot to be assigned to the autonomous robot  11 . Furthermore, for example, the region information may be set by the autonomous robot  11  itself by acquiring environment information before starting a task. 
     The route information is information indicating the kind of route along which the autonomous robot  11  is to move within the coverage region  21 . More specifically, the route information is information indicating the kind of route along which the autonomous robot  11  is to move with respect to the coverage region  21  or the like indicated in the region information. Here, the route information may be set in advance from the user, for example. Furthermore, the route information may be set, for example, when the autonomous robot  11  issues a request to another autonomous robot to which a coverage region has already been assigned, for a portion of the coverage region of the other autonomous robot to be assigned to the autonomous robot  11 . Furthermore, the route information may be generated by the autonomous robot  11  itself, for example. 
     The task-complete region information is information indicating, for example, a map or the area of the coverage region  21  that has been completed up to that point in time. More specifically, the task-complete region information indicates information relating to the regions of tasks that have already been executed by the autonomous robot  11  from within the coverage region  21  assigned to the autonomous robot  11 . Here, the task-complete region information is generated as follows. Specifically, while the autonomous robot  11  is executing tasks, the control unit  112  instructs the location measurement unit  117  such that location information of the autonomous robot  11  is periodically tracked and a movement locus of the autonomous robot  11  is acquired. The control unit  112  then deems the acquired movement locus to constitute regions of tasks that have been executed by the autonomous robot  11 , thereby generating task-complete region information. 
     The task-incomplete region information is information indicating, for example, a map or the area of the coverage region  21  that has not yet been completed. More specifically, the task-incomplete region information indicates information relating to the regions of tasks that have not yet been executed by the autonomous robot  11  from within the coverage region  21  assigned to the autonomous robot  11 . Here, the task-incomplete region information is generated by task-complete regions indicated in the task-complete region information being differentiated from the coverage region  21  assigned to the autonomous robot  11 , for example. 
     The task start time is information indicating the time at which the autonomous robot  11  started a task. The task start time is acquired by the time measurement unit  116 , which is instructed by the control unit  112 , immediately before the autonomous robot  11  starts the execution of a task. 
     The expected task end time is information indicating the time at which the autonomous robot  11  will complete a task. More specifically, the expected task end time is information indicating the expected time at which the autonomous robot  11  will complete a task assigned thereto. The expected task end time changes dynamically according to the progress of the tasks of the autonomous robot. 
     For example, the expected task end time for the point in time at which the autonomous robot  11  started a task is calculated as follows by the control unit  112 . First, the control unit  112  calculates the required time necessary for task execution on the basis of the area of the coverage region  21  included in the region information and the specification information of the local robot information  1151  stored in the storage unit  115 . Furthermore, the control unit  112  instructs the time measurement unit  116  to acquire a task start time. The control unit  112  then uses the acquired task start time and the calculated required time necessary for task execution to calculate the time at which the required time will have elapsed from the task start, as the expected task end time. 
     Furthermore, for example, the expected task end time for any point in time at which the autonomous robot  11  is executing a task is calculated as follows. First, the control unit  112  instructs the time measurement unit  116  to acquire time information, and uses the task start time of the local robot information  1151  stored in the storage unit  115  to calculate the required task time up to that point in time. The control unit  112  calculates a task processing amount per unit time for the execution of tasks up to that point in time, in accordance with the area of the task-complete region included in the task-complete region information of the local robot information  1151  stored in the storage unit  115  and the calculated required task time. Next, the control unit  112  calculates the required task time for executing the tasks of the task-incomplete region from that point in time, in accordance with the area of the task-incomplete region included in the task-incomplete region information of the local robot information  1151  stored in the storage unit  115 , and the calculated task processing amount per unit time. The control unit  112  then uses the acquired time information and the calculated required task time for the task-incomplete region to calculate the time at which the required task time will have elapsed from the acquired time information, as the expected task end time. 
     The task execution amount per unit time is information indicating a task processing amount or the like per unit time that represents the average amount of tasks executed per unit time by the autonomous robot  11 . The task processing amount per unit time is the average task processing amount per unit time for when the autonomous robot  11  executes the tasks for the coverage region  21 . 
     Here, the task processing amount per unit time for when a task is actually executed is calculated as follows, for example. First, the control unit  112  instructs the time measurement unit  116  to acquire time information at any point in time at which the autonomous robot  11  is executing a task. The control unit  112  calculates the required task time up to that point in time in accordance with the acquired time information and the task start time of the local robot information  1151  stored in the storage unit  115 . The control unit  112  then calculates an actual task execution amount per unit time by dividing the area of the task-complete region included in the task-complete region information of the local robot information  1151  stored in the storage unit  115 , by the calculated required task time. 
     It should be noted that the task execution amount per unit time is different from the aforementioned specification information. The task processing amount per unit time included in the specification information is preset information that indicates a task processing amount per unit time for when the autonomous robot  11  carries out a task with respect to a region in which there are no obstacles whatsoever. However, the actual task processing amount per unit time indicates a task processing amount per unit time for when the autonomous robot  11  has actually executed a task for the coverage region  21 . In the coverage region  21  in which the autonomous robot  11  actually executes tasks, there are objects and it is necessary for the autonomous robot  11  to make detours to execute the tasks, and therefore it is assumed that the task cannot be executed at the task processing amount per unit time included in the specification information. Furthermore, there are individual differences in autonomous robots, and, even in the case where there are no objects in the coverage region  21 , it is assumed that the task cannot be executed at the task processing amount per unit time included in the specification information. Therefore, the task processing amount per unit time for when the task is actually executed is a different value from the task processing amount per unit time of the specification information. 
     (Details of the Other Robot Information) 
     The other robot information  1152  includes information relating to other autonomous robots, and includes information stored in the storage unit  115  on the basis of information received from other autonomous robots by the autonomous robot  11 . 
     For example, as depicted in  FIG. 4 , the other robot information  1152  includes, for each of the other autonomous robots, robot-specific information, location information, an expected task end time, task-incomplete region information, and a task execution amount per unit time for the other autonomous robot in question. In the present embodiment, the other robot information  1152  includes robot-specific information, location information, an expected task end time, task-incomplete region information, and a task execution amount per unit time for each of the other autonomous robots  12 ,  13 , and  14 . 
     It should be noted that the information included in the other robot information  1152  is not restricted to the aforementioned examples. Distance information regarding the distance between the autonomous robot  11  and another autonomous robot and information relating to the progress of the tasks of the other autonomous robot may be included as information required for the autonomous robot  11  to cooperate with the other autonomous robot. For example, the other robot information  1152  may include robot-specific information, location information, and an expected task end time for each of the other autonomous robots. Furthermore, distance information indicating the distance from the autonomous robot  11  to another autonomous robot may be included instead of location information. The distance information can be calculated using the location information of the autonomous robot  11  and the location information of the other autonomous robot. 
     Furthermore, even in the case where the task execution amount per unit time is not able to be included as information forming part of the other robot information  1152 , a task start time, the required time for a task up to a certain point in time, and task-complete region information may be included. In the case where the task execution amount per unit time of another autonomous robot is required, the task execution amount per unit time can be calculated using the aforementioned information. 
     (Details of the Selection Standard) 
     The selection standard  1153  is stored in the storage unit  115  and indicates information (a selection standard) indicating which other autonomous robot is to be selected as a support-target candidate in the case where information of a plurality of other autonomous robots is included in the other robot information  1152 . For example, the selection standard  1153  may indicate that the other autonomous robot (second robot) having the largest amount of remaining tasks acquired by the control unit  112  from within a robot group, which is a plurality of other autonomous robots with which it is possible for the autonomous robot  11  (first robot) to communicate, is to be selected as the support-target robot. Furthermore, the selection standard  1153  may include frequency information indicating a frequency limit that is the number of times that the support-target robot can be altered. 
     In the present embodiment, a description is given in which the selection standard  1153  indicates that the autonomous robot having the latest expected task end time is to be selected as a support-target candidate (selection standard). According to this election standard, the autonomous robot  11 , which has completed the tasks therefor, is able to support the other autonomous robot having the latest expected task end time from among the information of the plurality of other autonomous robots stored in the storage unit  115 . It is thereby possible to advance the expected task end time of the entirety of the robot system  1 . 
     It should be noted that the selection standard  1153  differs according to the content required for the robot system  1 , and therefore may be set dynamically. Accordingly, it becomes possible to alter the information included in the selection standard  1153  in accordance with the requirements necessary for the robot system  1 , and it therefore becomes possible for the autonomous robot  11  to cooperate with the other autonomous robots to a greater extent to execute tasks. 
     Furthermore, the selection standard  1153  is not restricted to the aforementioned example. 
     For example, in the case where priority levels are given to tasks to which autonomous robots are assigned, the selection standard  1153  may indicate that the other autonomous robot having the task of the highest priority level is to be prioritized and selected as a support-target candidate. The autonomous robot  11  is thereby able to preferentially support the other autonomous robot having the task of the highest priority level, and it therefore becomes possible for the task of the highest priority level to be quickly completed. 
     Furthermore, for example, the selection standard  1153  may indicate that the other autonomous robot having the shortest distance to the autonomous robot  11  is to be selected as a support-target candidate. The autonomous robot  11  is thereby able to minimize the movement time required to travel to provide support, and it therefore becomes possible to increase the task execution operation rate of the autonomous robot  11 . 
     Furthermore, for example, the selection standard  1153  may indicate that the other autonomous robot for which tasks will be completed the quickest due to the autonomous robot  11  providing support is to be selected. Thus, the autonomous robot  11  selects the other autonomous robot for which tasks will be completed the quickest if the autonomous robot  11  provides support, from among the other autonomous robots included in the other robot information of the storage unit  115 , and it therefore becomes possible to increase the number of other autonomous robots for which tasks will be completed at an earlier time. That is, according to this selection standard, it becomes possible to more quickly increase the number of autonomous robots which can provide support. 
       FIG. 5  is a drawing depicting an example of the other robot information  1152  depicted in  FIG. 4 . 
       FIG. 5  depicts an example of the other robot information  1152  stored in the storage unit  115  on the basis of information received from each of the other autonomous robots  12 ,  13 , and  14 , which are within the communication range  311 , due to the autonomous robot  11  communicating with the other autonomous robots  12 ,  13 , and  14  in the situation depicted in  FIG. 1 . It should be noted that  FIG. 1  depicts, as an example, the situation when the autonomous robot  11  has completed the tasks assigned thereto as described above. Here, the time when the autonomous robot  11  has completed the tasks assigned thereto is taken as 13:30:00, and the location information of the autonomous robot  11  at such time is taken as a starting point, namely (0, 0). 
     [Operation of Autonomous Robot] 
     Next, an overview of the operation of the autonomous robot  11  configured as described above will be described. 
       FIG. 6  is a flowchart for describing the operation of the autonomous robot  11  according to embodiment 1. 
     First, the autonomous robot  11 , when the tasks assigned thereto have been completed (S 1 ), performs selection processing for a support-target robot (S 2 ). More specifically, in the case where the autonomous robot  11 , which is a first robot from among a plurality of autonomous robots, has completed tasks with respect to the coverage region  21  (first coverage region) assigned to the autonomous robot  11  (first robot), the autonomous robot  11  performs selection processing to select a support-target robot from within a robot group, which is a plurality of autonomous robots other than the first robot that are able to communicate with the autonomous robot  11  (first robot) from among the plurality of autonomous robots. 
     Next, the autonomous robot  11  starts moving toward the coverage region of the selected support-target robot (S 3 ). More specifically, the autonomous robot  11  (first robot) starts moving toward a second coverage region assigned to a second robot, which is the support-target robot selected by means of the selection processing of S 2 . 
     Next, the autonomous robot  11  determines whether to alter the support-target robot (S 4 ). More specifically, in the case where it has become newly possible to communicate with a third robot from among the plurality of autonomous robots while moving toward the second coverage region, the autonomous robot  11  (first robot) determines whether to alter the support-target robot to the third robot. 
     In the case where it is determined in S 4  that the support-target robot is to be altered (yes in S 4 ), the autonomous robot  11  alters the support-target robot (S 5 ), and starts moving toward the coverage region of the altered support-target robot (S 6 ). More specifically, in the case where it is determined that the support-target robot is to be altered from the second robot to the third robot, the autonomous robot  11  (first robot) starts moving toward a third coverage region assigned to the third robot. The autonomous robot  11  then performs the processing of S 4  once again. 
     However, in S 4 , in the case where it is determined that the support-target robot is not to be altered (no in S 4 ), the autonomous robot  11  continues to move toward the coverage region (second coverage region) of the support-target robot, and the present processing ends upon arriving at said coverage region (S 7 ). The autonomous robot  11  then supports the support-target robot with the tasks with respect to the coverage region at which the autonomous robot  11  has arrived. 
     (Details of the Selection Processing) 
     Next, the details of the selection processing of S 2  will be described using the drawings. 
       FIG. 7  is a flowchart for describing a detailed example of the selection processing of the autonomous robot  11  in embodiment 1.  FIG. 7  depicts an example of the selection processing of S 2  in which the autonomous robot  11  selects a support-target autonomous robot. 
     Hereinafter, a description will be given regarding a specific example of the selection processing in which the autonomous robot  11  selects a cooperation partner therefor, namely another autonomous robot to be a support target for the autonomous robot  11 , on the basis of the other robot information  1152  when having completed the tasks assigned thereto. 
     Here, the autonomous robot  11  has completed tasks in the situation depicted in  FIG. 1 , the time at which the autonomous robot  11  completed the tasks assigned thereto is taken as 13:30:00, and the location information of the autonomous robot  11  is taken as (0, 0). Furthermore, it is assumed that the other robot information depicted in  FIG. 4  is stored in the storage unit  115 , and that a movement speed of 10 m/min. for the autonomous robot  11  is included in the specification information of the autonomous robot  11 . The autonomous robot  11  starts the selection processing to select a support-target robot when having completed the tasks for the coverage region  21  assigned thereto. 
     First, the autonomous robot  11  acquires other robot information from other autonomous robots with which communication is possible (S 201 ). In the present embodiment, the autonomous robot  11  communicates with each of the other autonomous robots  12 ,  13 , and  14  that are present in the communication range  311  thereof as depicted in  FIG. 1 , and receives robot-specific information that includes robot identification information and specification information, task information that is information relating to tasks, and location information of the autonomous robots, from each of the other autonomous robots  12 ,  13 , and  14 . On the basis of the information received from the other autonomous robots, the autonomous robot  11  stores the other robot information  1152 , which includes robot-specific information, location information, an expected task end time, task-incomplete region information, and a task execution amount per unit time as depicted in  FIG. 4 , for example, in the storage unit  115 . 
     In the present embodiment, the autonomous robot  11  acquires the information of other autonomous robots themselves from the other autonomous robots; however, it should be noted that the present disclosure is not restricted thereto. The autonomous robot  11  may also additionally acquire the information of different autonomous robots possessed by the other autonomous robots. In this case, the autonomous robot  11  is able to acquire the information of a greater number of other autonomous robots, and it therefore becomes possible to select a support-target robot in a more appropriate manner. 
     Next, the autonomous robot  11  determines whether the information of another autonomous robot is present in the storage unit  115  (S 202 ). It should be noted that, in this processing, the autonomous robot  11  determines whether information from another autonomous robot has been acquired. 
     In S 202 , in the case where the information of another autonomous robot is not present in the storage unit  115  (no in S 202 ), it is determined that there is no other autonomous robot to be a support-target robot (S 203 ), and processing ends. Here, the case where the information of another autonomous robot is not present in the storage unit  115  corresponds to the case where, in the processing of S 201 , the autonomous robot  11  has not been able to acquire information from another autonomous robot, and does not possess the information of another autonomous robot. 
     However, in S 202 , in the case where the information of another autonomous robot is present in the storage unit  115  (yes in S 202 ), processing advances to S 204 . In the present embodiment, in S 201 , the autonomous robot  11  acquires information from the other autonomous robots, and, in the case where the information of the other autonomous robots is stored in the storage unit  115 , determines that there are autonomous robots to be support-target candidates. 
     Then, in S 201  to S 213 , the autonomous robot  11  starts processing for choosing another autonomous robot to be a support-target candidate, and determining whether the other autonomous robot is appropriate as a support target. In the present embodiment, as depicted in  FIG. 4 , the autonomous robot  11  possesses the information of the other autonomous robots  12 ,  13 , and  14 , and therefore starts processing for choosing an autonomous robot to be a support-target candidate from thereamong and determining whether that autonomous robot that is to be a support-target candidate is appropriate as a support target. 
     First, in S 204 , the autonomous robot  11  uses the location measurement unit  117  to acquire current location information of the autonomous robot  11 . In the present embodiment, the location information of the autonomous robot  11  at the point in time of having completed the tasks is (0, 0), and therefore the location information (0, 0) of the autonomous robot  11  is acquired using the location measurement unit  117 . 
     Next, in S 205 , the autonomous robot  11  extracts, from the storage unit  115 , the robot having the latest expected task end time that conforms with the selection standard  1153 . In the present embodiment, first, the autonomous robot  11  acquires information of another autonomous robot to be a support-target candidate from the other robot information  1152  in the storage unit  115 . Next, since information of a plurality of other autonomous robots is included in the other robot information  1152  in the storage unit  115 , the autonomous robot  11  extracts another autonomous robot to be a support-target candidate in accordance with the selection standard  1153 . Here, as described above, the selection standard  1153  indicates that the other autonomous robot having the latest expected task end time is to be selected as a support-target candidate. Therefore, in accordance with this selection standard  1153 , the autonomous robot  11  extracts information of the autonomous robot  14 , which is the other autonomous robot having the latest expected task end time, from the other robot information  1152  in the storage unit  115  depicted in  FIG. 4 . 
     Next, in S 206 , the autonomous robot  11  acquires the location information of the other autonomous robot extracted. In the present embodiment, the autonomous robot  11  acquires location information (30, 40) of the autonomous robot  14  such as that depicted in  FIG. 5 , from the other robot information of the autonomous robot  14  extracted in S 205 . 
     Next, in S 207 , the autonomous robot  11  calculates the distance to the other autonomous robot extracted, and calculates a movement time. In the present embodiment, the autonomous robot  11  uses the Pythagorean theorem to calculate a movement distance of 50 m in accordance with the location information (0, 0) of the autonomous robot  11  acquired in S 204  and the location information (30, 40) of the autonomous robot  14  extracted in S 206 . The autonomous robot  11  then divides the calculated movement distance of 50 m by the movement speed of 10 m/min. included in the specification information of the autonomous robot  11  to thereby calculate a movement time of 5 min. 
     Next, in S 208 , the autonomous robot  11  acquires the tasks of the extracted other autonomous robot that will be remaining after having moved. In the present embodiment, first, the autonomous robot  11  calculates a movement time task amount that will be executed by the autonomous robot  14  during the movement time required for the autonomous robot  11  to move to the autonomous robot  14  extracted in S 205  or the coverage region of the autonomous robot  14 . Here, the task processing amount per unit time of the autonomous robot  14  is 1/min. according to  FIG. 5  and the movement time calculated in S 207  is 5 min., and therefore the autonomous robot  11  multiplies those values to calculate a movement time task amount of 5. Next, the autonomous robot  11  calculates the amount of tasks of the autonomous robot  14  that will be remaining after the movement time. Here, the amount of remaining tasks of the autonomous robot  14  before the autonomous robot  11  moves, namely the task-incomplete region, is 36 according to  FIG. 5 . Furthermore, the movement time task amount of the autonomous robot  14  is 5. Consequently, the autonomous robot  11  is able to calculate that the amount of remaining tasks of the autonomous robot  14  for when the autonomous robot  11  will have finished moving is 31, by subtracting the movement time task amount of 5, which is the amount of tasks executed by the autonomous robot  14  while the autonomous robot  11  is moving, from the amount of remaining tasks of  36  of the autonomous robot  14  from prior to the autonomous robot  11  moving. 
     Next, in S 209 , the autonomous robot  11  determines whether there will be remaining tasks. In the present embodiment, the autonomous robot  11  determines whether there will be more than 0 tasks remaining for the autonomous robot  14  after moving. This determination processing is a determination as to whether the tasks of the autonomous robot  14  will be completed during the movement in which the autonomous robot  11  moves toward the autonomous robot  14  to provide support. 
     In S 209 , in the case where the amount of remaining tasks is 0 or less, namely that there are no remaining tasks (no in S 209 ), the autonomous robot  11  determines whether the information of yet other autonomous robots is present in the other robot information  1152  in the storage unit  115  (S 210 ). Here, the case where the amount of remaining tasks is 0 or less corresponds to the case where the tasks of the support-target autonomous robot will have been completed while the autonomous robot  11  is moving thereto to provide support, and therefore the autonomous robot  11  determines that support for the support-target autonomous robots is not required. It should be noted that, in S 210 , in the case where the information of yet other autonomous robots is not present in the other robot information  1152  in the storage unit  115  (no in S 210 ), the autonomous robot  11  determines that there is no other autonomous robot to be a support target (S 212 ), and processing ends. However, in S 210 , in the case where the information of yet other autonomous robots is present in the other robot information  1152  in the storage unit  115  (yes in S 210 ), the autonomous robot having the latest expected task end time is extracted from among the information of the yet other autonomous robots (S 211 ), and processing advances to S 206 . 
     However, in S 209 , in the case where the amount of remaining tasks is greater than 0 (yes in S 209 ), the autonomous robot  11  determines the extracted other autonomous robot as a support target (S 213 ). In the present embodiment, the amount of remaining tasks of the autonomous robot  14  is 31, which is greater than 0, and therefore the autonomous robot  11  determines that a task-incomplete region will be present at the autonomous robot  14  when having arrived at the autonomous robot  14  or the like (after having completed moving). In this way, the autonomous robot  11  is able to determine that the autonomous robot  14  is appropriate as another support-target autonomous robot. 
     Next, the autonomous robot  11  notifies the other autonomous robot selected as a support target that the other autonomous robot has been selected as a support target (S 214 ). 
     In the present embodiment, upon selecting the support-target autonomous robot  14 , the autonomous robot  11  starts moving toward the autonomous robot  14  in order to cooperate with the autonomous robot  14  to execute the tasks of the autonomous robot  14 . At such time, the autonomous robot  11  notifies the autonomous robot  14  with information indicating that the autonomous robot  11  is coming to provide support. 
     The autonomous robot  14  is thereby able to confirm that the autonomous robot  11  is coming to provide support, and is able to complete tasks earlier than the current expected task end time. Furthermore, when information relating to tasks is requested from another autonomous robot, the autonomous robot  14  is able to provide the other autonomous robot with information including the point that its tasks will be completed earlier than expected due to the autonomous robot  11  coming to provide support. Accordingly, the other autonomous robot is able to select a support-target autonomous robot with consideration being given to the information received from the autonomous robot  14 . In other words, the other autonomous robot is able to select a support-target autonomous robot in a more appropriate manner on the basis of the information received from the autonomous robot  14 , and therefore the cooperation between autonomous robots is able to function in a more appropriate manner across the entirety of the robot system  1 . 
     Furthermore, in the case where the autonomous robot  11  notifies the autonomous robot  14  with information indicating that the autonomous robot  11  is coming to provide support, the autonomous robot  14  may, in addition, determine a coverage region for which support is to be received and notify such to the autonomous robot  11  while the autonomous robot  11  is moving toward the autonomous robot  14 . It thereby becomes possible for the autonomous robot  11  to move directly to the coverage region of the autonomous robot  14  to be handled by the autonomous robot  11  instead of moving to the current location of the autonomous robot  14 . Furthermore, it becomes possible for the autonomous robot  11  to generate, in advance, which kind of route is to be taken through the coverage region of the autonomous robot  14  to be handled thereby. 
     It is assumed that S 214  is performed when the autonomous robot  11  is moving; however, it should be noted that the present disclosure is not restricted thereto, and S 214  may be performed when an autonomous robot has determined another autonomous robot as a support target. Furthermore, the autonomous robot  11  may not perform S 214 . 
     Furthermore, the information notified by the autonomous robot  11  in S 214  may include the expected task end time for when the autonomous robot  11  has provided support. The expected task end time for when the autonomous robot  11  has provided support can be calculated by, for example, using the required time for when the amount of remaining tasks calculated in S 208  is to be carried out by both the autonomous robot  11  and the autonomous robot  14 , and the expected time for the autonomous robot  11  to arrive at the autonomous robot  14  or the like, to calculate the time at which the required time will have elapsed from the expected time. 
     Furthermore, the present disclosure is not restricted to the case where the autonomous robot  11  calculates the expected task end time, and the autonomous robot  14  may calculate the expected task end time. 
     Furthermore, the autonomous robot  11  may execute tasks for a coverage region of another autonomous robot while moving toward the support-target autonomous robot  14 . For example, in the case where there is a task-incomplete region of another autonomous robot in the movement route along which the autonomous robot  11  will move toward the support-target autonomous robot  14 , the autonomous robot  11  may move while executing the tasks for said task-incomplete region. Thus, the tasks for the task-incomplete region of the other autonomous robot are executed, and therefore the amount of tasks of the other autonomous robot decrease, and the other autonomous robot is able to complete its tasks earlier. 
     Due to the aforementioned selection processing, the autonomous robot  11 , after having completed the tasks for the coverage region  21  assigned thereto, is able to select any of the other autonomous robots  12 ,  13 , and  14  as a support-target autonomous robot on the basis of information obtained by communicating with the autonomous robots  12 ,  13 , and  14 . It thereby becomes possible for the autonomous robot  11  to provide support for a portion of the tasks of the support-target autonomous robot selected by means of the selection processing. 
     (Details of the Alteration Processing) 
     Next, the details of the alteration processing indicated in S 4  of  FIG. 6  will be described using the drawings. 
       FIG. 8  is a drawing conceptually depicting a situation in which the autonomous robot  11  according to embodiment 1 has newly detected another autonomous robot while moving toward a support-target autonomous robot.  FIG. 8  depicts a situation in which, as an example, the autonomous robot  11  has newly detected an autonomous robot  16  while moving toward the autonomous robot  14 . 
     As described above, the autonomous robot  11 , after having completed the tasks for the coverage region  21  assigned thereto, performs selection processing in which an autonomous robot to be a support target is selected on the basis of information received from each of the autonomous robots  12 ,  13 , and  14  that are within a communication range  312 . The autonomous robot  11  then starts moving in order to support the other autonomous robot selected by means of the selection processing. Due to this movement, the communication range of the autonomous robot  11  also moves, and therefore the autonomous robot  11  becomes unable to communicate with other autonomous robots with which communication had been possible up to that point in time, and becomes able to communicate with other new autonomous robots. 
     Hereinafter, the autonomous robot  11  performs alteration processing in which a determination is made as to whether the support-target autonomous robot is to be altered, with consideration being given also to information acquired from the autonomous robot  16  with which communication has become newly possible due to the movement as depicted in  FIG. 8 ; this is described hereinafter. 
       FIG. 9  is a flowchart for describing a detailed example of the alteration processing performed by the autonomous robot  11  in embodiment 1.  FIG. 9  depicts an example of the case where the autonomous robot  11  newly detects another autonomous robot while moving toward the support-target autonomous robot, and performs the alteration processing of S 4 . 
     First, the autonomous robot  11  acquires other robot information from the new autonomous robot detected (S 401 ). In the present embodiment, the autonomous robot  11  newly detects the autonomous robot  16  while moving to provide support to the autonomous robot  14 . Thereupon, the autonomous robot  11  communicates with the autonomous robot  16  to acquire the other robot information, in other words, robot-specific information that includes robot identification information and specification information of the autonomous robot  16 , task information that is information relating to tasks, and location information of the autonomous robot  16 . 
     Next, the autonomous robot  11  compares the expected task end time of the new autonomous robot (time  1 ) and the expected task end time of the support-target autonomous robot (time  2 ) (S 402 ). In the present embodiment, the autonomous robot  11  compares the acquired expected task end time of the autonomous robot  16  and the expected task end time of the support-target autonomous robot  14  stored in the other robot information  1152  in the storage unit  115 . 
     It should be noted that there is also a possibility of the task progress status of the autonomous robot  14  having changed while the autonomous robot  11  has been moving toward the support-target autonomous robot  14 . Therefore, in the case where communication with the autonomous robot  14  is possible, the autonomous robot  11  may communicate with the autonomous robot  14  to acquire other robot information that is the most up-to-date. It thereby becomes possible for the autonomous robot  11  to perform support-target alteration processing in a more appropriate manner. 
     Furthermore, in embodiment 1, the selection standard  1153  indicates that the autonomous robot having the latest expected task end time is to be selected as a support target, and therefore a comparison is performed using the expected task end time parameter. It should be noted that the parameter used in S 402  is different if the content of the selection standard indicated in the selection standard  1153  is different. For example, in the case where the selection standard  1153  indicates that the autonomous robot carrying out the task having the highest priority level is to be selected as a support target, a task priority level may be used as the parameter. Furthermore, for example, in the case where the selection standard  1153  indicates that the autonomous robot having the shortest distance to an autonomous robot is to be selected as a support target, the distance to the autonomous robot may be used as the parameter. 
     In the case where time  1  comes temporally before time  2  in S 402 , the autonomous robot  11  determines that it is not necessary to alter the support target (S 403 ), and processing ends. In the present embodiment, if the expected task end time of the newly detected autonomous robot  16  (time  1 ) comes temporally before the expected task end time of the autonomous robot  14  (time  2 ), the autonomous robot  11  determines that the autonomous robot  14  is more appropriate as the support target and it is not necessary to alter the support target, and processing ends. The autonomous robot  11  then resumes or continues moving toward the support-target autonomous robot  14  as planned. 
     However, in the case where time  1  comes temporally after time  2  in S 402 , the autonomous robot  11  determines that it is necessary to alter the support target, and processing proceeds to S 404 . 
     In the present embodiment, if the expected task end time of the newly detected autonomous robot  16  (time  1 ) comes temporally after the expected task end time of the support-target autonomous robot  14  (time  2 ), the autonomous robot  11  determines that there is a possibility of the autonomous robot  16  being more appropriate as the support target. Then, in S 404  to S 409 , the autonomous robot  11  performs processing (verification processing) for determining whether the autonomous robot  16  is more appropriate as the support target. In this verification processing, in the case where it is assumed that the autonomous robot  11  is to move to the autonomous robot  16 , a determination is made as to whether the task of the autonomous robot  16  will have been completed at the point in time at which the autonomous robot  11  will have arrived at the autonomous robot  16  or a coverage region  26  of the autonomous robot  16 . Then, in the case where the task of the autonomous robot  16  will have been completed at said arrival time, it is determined that support for the autonomous robot  16  is not necessary. However, in the case where the task of the autonomous robot  16  will not have been completed at said arrival time, it is determined that the autonomous robot  16  is appropriate as a support target; this is described in detail hereinafter. 
     First, in S 404 , the autonomous robot  11  uses the location measurement unit  117  to acquire current location information of the autonomous robot  11 . 
     Next, in S 405 , the autonomous robot  11  calculates the distance to the new autonomous robot, and calculates a movement time. In the present embodiment, the autonomous robot  11  calculates the movement distance between the autonomous robot  11  and the autonomous robot  16  according to the location information of the autonomous robot  16  acquired in S 401  and the location information of the autonomous robot  11  acquired in S 404 . The autonomous robot  11  then calculates the movement time for the case where the autonomous robot  11  has moved to the autonomous robot  16 , by dividing the calculated movement distance by the movement speed included in the specification information thereof. This processing is the same as that described in S 207 , and therefore a detailed description thereof is omitted. 
     Next, in S 406 , the autonomous robot  11  acquires the tasks of the new autonomous robot that will be remaining after the movement time. In the present embodiment, first, the autonomous robot  11  calculates the movement time task amount that will be executed by the autonomous robot  16  during the movement time calculated in S 405 . Next, the autonomous robot  11  calculates the amount of tasks of the autonomous robot  16  that will be remaining after the movement time. This processing is the same as that described in S 208 , and therefore a detailed description thereof is omitted. 
     Next, in S 407 , the autonomous robot  11  determines whether there will be tasks remaining for the new autonomous robot. In the present embodiment, the autonomous robot  11  determines whether there will be more than 0 tasks remaining for the autonomous robot  16  after the movement time. 
     In S 407 , in the case where the amount of remaining tasks of the new autonomous robot is 0 or less (no in S 407 ), the autonomous robot  11  determines that it is not necessary to alter the support target (S 408 ). In the present embodiment, in the case where the amount of remaining tasks is 0 or less, the autonomous robot  11  is able to determine that the tasks of the autonomous robot  16  will be completed while the autonomous robot  11  is moving toward the autonomous robot  16 , and therefore determines that support for the autonomous robot  16  is not necessary. The autonomous robot  11  then resumes or continues moving toward the autonomous robot  14  as planned without altering the support-target autonomous robot. 
     However, in S 407 , in the case where the amount of remaining tasks is greater than 0 (yes in S 407 ), the autonomous robot  11  alters the support target to the new autonomous robot (S 409 ). In the present embodiment, in the case where the amount of remaining tasks of the autonomous robot  16  is greater than 0, the autonomous robot  11  determines that a task-incomplete region will be present at the autonomous robot  16  when the autonomous robot  11  has arrived at the autonomous robot  16  or the like (after having completed moving). In this way, the autonomous robot  11  determines that the autonomous robot  16  is more appropriate as the support target. The autonomous robot  11  then alters the support target from the autonomous robot  14  to the autonomous robot  16 . 
     Next, the autonomous robot  11  notifies the pre-alteration support-target autonomous robot and the post-alteration support-target autonomous robot that the support target has been altered (S 410 ). 
     In the present embodiment, when the support-target autonomous robot is altered to the autonomous robot  16  in S 409 , the autonomous robot  11  starts moving toward the altered support-target autonomous robot  16 . At such time, the autonomous robot  11  notifies the autonomous robot  16  that has become the support target with information indicating that the autonomous robot  11  is coming to provide support, and notifies the autonomous robot  14  with information indicating that the autonomous robot  11  is not coming to provide support. 
     It is assumed that S 410  is performed when the autonomous robot  11  is moving; however, it should be noted that the present disclosure is not restricted thereto, and S 410  may be performed when an autonomous robot has altered a support target. Furthermore, the autonomous robot  11  may not perform S 410 . 
     According to the aforementioned alteration processing, in the case where there is an autonomous robot with which communication has become newly possible while the autonomous robot  11  is moving toward the support target selected in the selection processing, the autonomous robot  11  is able to perform support-target alteration processing on the basis of information from said autonomous robot. It thereby becomes possible for the autonomous robot  11  to select a more appropriate autonomous robot as a support target in the robot system  1 , and it therefore becomes possible for the autonomous robot  11  to coordinate with other autonomous robots to execute tasks more efficiently. 
     [Effects, Etc.] 
     As described above, according to the present embodiment, a first robot that has completed a task with respect to an assigned coverage region is able to perform support-target alteration processing on the basis of information from a third robot with which communication has become newly possible when moving toward a second robot that is a support target, and is therefore able to select a more appropriate robot as a support target. It is thereby possible to realize a movement control method and a movement control device with which it is possible for an autonomous robot to cooperate with a greater number of other autonomous robots to execute tasks even in the case where the other autonomous robots with which communication is possible dynamically change. 
     In this way, according to the movement control method and the like of the present embodiment, an autonomous robot, after completing its own tasks, selects a support-target autonomous robot on the basis of information of other autonomous robots within a communication range, and, on the basis of information from an autonomous robot with which communication has newly become possible when moving toward the selected support-target autonomous robot, is able to perform a review of the support target and select a more appropriate support-target autonomous robot. It is thereby possible for the autonomous robot to coordinate with other autonomous robots to execute tasks more efficiently in the robot system. 
     Furthermore, according to the present embodiment, after the selection processing (in S 214 ), the autonomous robot  11  notifies the selected support-target autonomous robot of having been selected as a support target. The support-target autonomous robot is thereby able to receive notification from the autonomous robot  11  that the autonomous robot  11  is coming to provide support, and issues a transmission to surrounding autonomous robots indicating that the task of the support-target autonomous robot will be completed quickly due to the support from the autonomous robot  11 . Therefore, the autonomous robots surrounding the support-target autonomous robot are able to select support-target autonomous robots with consideration being given to the information transmitted by the aforementioned support-target autonomous robot, and it is therefore possible for the autonomous robots to coordinate to execute tasks more efficiently in the robot system  1 . 
     Furthermore, according to the present embodiment, after the alteration processing (in S 410 ), the autonomous robot  11  notifies the pre-alteration support-target autonomous robot and the post-alteration support-target autonomous robot that the support target has been altered. The pre-alteration support-target autonomous robot is thereby able to transmit accurate information to surrounding autonomous robots, and therefore the surrounding autonomous robots are able to select support-target autonomous robots on the basis of the accurate information. 
     Hypothetically, in the case where the autonomous robot  11  did not notify the pre-alteration support-target autonomous robot that the support target has been altered, a state would be entered in which the pre-alteration support-target autonomous robot does not know that the autonomous robot  11  is no longer coming to provide support. Therefore, the pre-alteration support-target autonomous robot would not be able to transmit information to the surrounding autonomous robots indicating that the autonomous robot  11  is no longer coming to provide support, and therefore the surrounding autonomous robots would select support-target autonomous robots under the mistaken perception that the autonomous robot  11  is coming to provide support to the autonomous robot  14 . In this case, a state would entered in which the pre-alteration support-target autonomous robot does not receive support from not only the autonomous robot  11  but also the surrounding autonomous robots, and there is a possibility of the task of the pre-alteration support-target autonomous robot being completed late. 
     Furthermore, according to the present embodiment, it is possible to control the number of times that the alteration processing of the autonomous robot  11  is performed, and it is therefore possible to limit the autonomous robot  11  requiring a large amount of time to arrive at a support-target autonomous robot or the like and there being less time for actually supporting tasks due the support-target autonomous robot being altered numerous times. 
     (Embodiment 2) 
     In embodiment 1, a description was given regarding the case where, during selection processing, a support-target autonomous robot is selected from among a plurality of other autonomous robots with which communication is possible; however, the present disclosure is not restricted thereto. In embodiment 2, a description is given regarding an example of the case where an autonomous robot  11 B selects a support-target autonomous robot from among other autonomous robots with which communication has been possible, while executing or after executing a task of the autonomous robot  11 B. 
     [Functional Configuration of Autonomous Robot] 
     Hereinafter, as with embodiment 1, the functional configuration of the autonomous robot  11 B will be representatively described. 
       FIG. 10  is a block diagram depicting an example of the functional configuration of the autonomous robot  11 B in embodiment 2. The same elements as in  FIG. 2  are denoted by the same reference numbers, and a detailed description thereof is omitted. 
     The autonomous robot  11 B depicted in  FIG. 10  is different from the autonomous robot  11  depicted in  FIG. 2  with regard to the configurations of a control unit  112 B and a storage unit  115 B. 
     [Control Unit  112 B] 
       FIG. 11  is a block diagram depicting an example of the detailed configuration of the control unit depicted in  FIG. 10 . The same elements as in  FIG. 3  are denoted by the same reference numbers, and a detailed description thereof is omitted. 
     As depicted in  FIG. 11 , the control unit  112 B is provided with a selection processing unit  1121 B, a movement control unit  1122 B, an alteration determination unit  1123 , and a notification control unit  1124 . The control unit  112 B is different from the control unit  112  depicted in  FIG. 3  with regard to the configurations of the selection processing unit  1121 B and the movement control unit  1122 B. 
     The selection processing unit  1121 B is provided with the functions of the selection processing unit  1121 . In addition, in the case where at least one item of information relating to a plurality of other autonomous robots stored in the storage unit  115 B is received outside of a prescribed period that is based on the point in time at which tasks with respect to a coverage region  21  (first coverage region) have been completed, the selection processing unit  1121 B instructs the movement control unit  1122 B for the autonomous robot  11 B (first robot) to be made to move within the coverage region  21  (within the first coverage region). 
     Furthermore, when it has become possible for the autonomous robot  11 B (first robot) to communicate with another autonomous robot that corresponds to said at least one item of information while moving within the coverage region  21  (within the first coverage region), the selection processing unit  1121 B receives other robot information of the other autonomous robot, and acquires the remaining tasks of each robot of a robot group that includes the other autonomous robot. 
     The movement control unit  1122 B is provided with the functions of the movement control unit  1122 . The movement control unit  1122 B, in addition, causes the autonomous robot  11 B (first robot) to move within the coverage region  21  (within the first coverage region) in accordance with the instruction from the selection processing unit  1121 B. In the present embodiment, the movement control unit  1122 B causes the autonomous robot  11 B (first robot) to move within the coverage region  21  (with the first coverage region) toward a location indicated by reception location information of the autonomous robot  11 B (first robot) from when having received the other robot information of the other autonomous robot. 
     [Storage Unit  115 B] 
     Next,  FIG. 12  will be used to describe the information stored in the storage unit  115 B of the autonomous robot  11 B. 
       FIG. 12  is a drawing conceptually depicting the information stored in the storage unit of an autonomous robot in embodiment 2. The same elements as in  FIG. 4  are denoted by the same reference numbers, and a detailed description thereof is omitted. 
     As in embodiment 1, the storage unit  115 B stores local robot information  1151 , a selection standard  1153 , and other robot information  1152 B that is based on information transmitted from other autonomous robots. 
     The storage unit  115 B is different from the storage unit  115  depicted in  FIG. 4  with regard to the information that includes the other robot information  1152 B. Furthermore, the storage unit  115 B is different from the storage unit  115  depicted in  FIG. 4  with regard to the autonomous robot  11 B (first robot) storing the other robot information of other autonomous robots received while executing tasks with respect to the coverage region  21  (first coverage region). That is, in the present embodiment, the autonomous robot  11 B, while executing tasks for the coverage region  21  thereof, periodically communicates with other autonomous robots within a communication range, and stores acquired other robot information of the other autonomous robots. 
     (Details of the Other Robot Information) 
     As depicted in  FIG. 12 , the other robot information  1152 B includes information indicating a local robot reception location and a communication status in addition to the information included in the other robot information  1152  depicted in  FIG. 4 . 
     The local robot reception location is information that indicates the location (reception location) from when the autonomous robot  11 B (first robot) has received other robot information from each of the other autonomous robots while executing tasks with respect to the coverage region  21  (first coverage region). In the present embodiment, the local robot reception location is the location information of the autonomous robot  11 B acquired by the location measurement unit  117  when having received information from another autonomous robot, and is included in the other robot information. In this way, the local robot reception location and the other robot information corresponding thereto are associated. The communication status is information indicating the current communication status of each of the other autonomous robots. 
     It should be noted that although the other robot information  1152 B does not include a task execution amount per unit time, this may be included. Furthermore, the other robot information  1152 B may also include time information that indicates the time at which the autonomous robot  11 B (first robot) has received the other robot information of each of the other autonomous robots. 
       FIG. 13  is a drawing depicting an example of the other robot information  1152 B depicted in  FIG. 12 . The same elements as in  FIG. 5  are denoted by the same reference numbers, and a detailed description thereof is omitted. 
       FIG. 13  depicts that the information of autonomous robots  12 B,  13 B, and  14 B is stored as the other robot information  1152 B in the storage unit  115 B. Furthermore,  FIG. 13  depicts that, at present, the autonomous robot  11 B is able to communicate with the autonomous robots  13 B and  14 B but is unable to communicate with the autonomous robot  12 B. It should be noted that the other robot information of the autonomous robot  12 B was received when the autonomous robot  11 B was previously able to communicate with the autonomous robot  12 B. 
     The autonomous robot  11 B configured as described above, when having completed the tasks therefor, selects another autonomous robot to be a support target, on the basis of the other robot information of other autonomous robots with which communication is currently possible, and other robot information acquired by once again communicating with other autonomous robots with which communication is currently not possible, from among the information of other autonomous robots stored while executing tasks. 
     [Operation of Autonomous Robot] 
     Next, an overview of the operation of the autonomous robot  11 B configured as described above will be described. 
       FIGS. 14A and 14B  are drawings conceptually depicting a situation for the autonomous robots that make up the robot system in embodiment 2.  FIG. 14A  depicts an example of a situation in which the autonomous robots  11 B to  14 B are executing tasks for coverage regions  21  to  24  assigned thereto.  FIG. 14B  depicts an example of the situation when the autonomous robot  11 B has completed its tasks. The same constituent elements as in  FIG. 1  are denoted by the same reference numbers, and a description thereof is omitted. It should be noted that a communication range  313 B of  FIG. 14A  and a communication range  314 B of  FIG. 14B  indicate communication ranges in which the autonomous robot  11 B is able to communicate. 
     The autonomous robot  11 B that is executing tasks as depicted in  FIG. 14A  is able to communicate with the autonomous robots  12 B and  13 B that are within the communication range  313 B. However, as depicted in  FIG. 14B , the autonomous robot  11 B when having completed the tasks is able to communicate with the autonomous robots  13 B and  14 B that are within the communication range  314 B but is not able to communicate with the autonomous robot  12 B with which communication had been possible in  FIG. 14A . 
     The autonomous robot  11 B may use only the other robot information of the autonomous robots  13 B and  14 B with which communication is currently possible to select another autonomous robot to be a support target, but it is more desirable to use the other robot information of as many other autonomous robots as possible to more appropriately select another autonomous robot to be a support target. Therefore, in the present embodiment, in the selection processing indicated in S 2 , the autonomous robot  11 B once again attempts to communicate also with other autonomous robots with which communication is currently not possible, to acquire other robot information to select another autonomous robot for a support target. 
     (Details of the Selection Processing) 
     Next, the details of the selection processing in the present embodiment will be described using  FIG. 15 . 
       FIG. 15  is a flowchart for describing a detailed example of the selection processing of an autonomous robot in embodiment 2.  FIG. 15  depicts an example of selection processing in which the autonomous robot  11 B selects another autonomous robot for a support target when having completed tasks. 
     First, the autonomous robot  11 B, when having completed the tasks assigned thereto, communicates with each of the other autonomous robots with which communication is currently possible, and acquires the other robot information thereof (S 2011 ). 
     In the present embodiment, the autonomous robot  11 B communicates with each of the autonomous robots  13 B and  14 B, acquires the other robot information  1152 B, and stores this in the storage unit  115 B. The other robot information  1152 B that is acquired is, for example, robot-specific information that includes robot identification information and specification information of the autonomous robots  13 B and  14 B, task information that is information relating to tasks, a local robot reception location, and the like. It should be noted that, in the case where the autonomous robot  11 B communicates with another autonomous robot with which communication is possible and the other robot information of the other autonomous robot is already stored, the other robot information that is stored is updated. 
     Next, the autonomous robot  11 B confirms with the storage unit  115 B to determine whether there is other robot information of other autonomous robots with which communication is currently not possible (S 2012 ). 
     In S 2012 , in the case where there is no other robot information of other autonomous robots with which communication is currently not possible (no in S 2012 ), an autonomous robot to be a support target is selected on the basis of the other robot information of other autonomous robots with which communication is currently possible (S 2019 ). It should be noted that, in S 2019 , the same processing as that of S 202  to S 214  described in  FIG. 7  is performed. Since S 202  to S 214  have been described above, a description thereof is omitted here. 
     However, in S 2012 , in the case where there is other robot information of another autonomous robot with which communication is currently not possible (yes in S 2012 ), the local robot reception location from which communication was last performed with the other autonomous robot with which communication is currently not possible is acquired (S 2013 ). In the present embodiment, the autonomous robot  11 B extracts the local robot reception location included in (associated with) the other robot information of the other autonomous robot with which communication is currently not possible, in order to attempt to communicate once again with the other autonomous robot with which communication is currently not possible. In the examples depicted in  FIGS. 13 and 14B , the autonomous robot  11 B extracts the local robot reception location in the other robot information of the autonomous robot  12 B with which communication is currently not possible. 
     The autonomous robot  11 B starts moving toward the local robot reception location acquired in S 2013  (S 2014 ). In the present embodiment, the autonomous robot  11 B starts moving toward the local robot reception location, which is the location from which communication was previously performed with the autonomous robot  12 B with which communication is currently not possible, extracted in S 2013 . 
     Next, while moving, the autonomous robot  11 B determines whether another autonomous robot with which communication is currently not possible has been detected (S 2015 ). In the present embodiment, the autonomous robot  11 B, from starting to move until arriving at the local robot reception location acquired in S 2013  that is the destination, periodically determines whether the autonomous robot  12 B with which communication is currently not possible has been detected. 
     In the case where another autonomous robot with which communication is currently not possible is detected in S 2015  (yes in S 2015 ), the autonomous robot  11 B acquires other robot information from the other autonomous robot detected (S 2016 ). In the present embodiment, upon detecting the autonomous robot  12 B, the autonomous robot  11 B communicates with the detected autonomous robot  12 B to acquire the other robot information of the autonomous robot  12 B. 
     The autonomous robot  11 B then selects an autonomous robot to be a support target according to the other robot information of the other autonomous robots with which communication is currently possible (S 2017 ). In the present embodiment, the autonomous robot  11 B selects an autonomous robot to be a support target, on the basis of the other robot information acquired in S 2016 , and the other robot information of the autonomous robot  12 B with which communication is currently possible, acquired in S 2011 . It should be noted that, in S 2017 , the same processing as that of S 202  to S 214  described in  FIG. 7  is performed. Since S 202  to S 214  have been described above, a description thereof is omitted here. 
     However, in S 2015  and S 2018 , in the case of having arrived at the location (destination) indicated by the local robot reception location without having detected another autonomous robot with which communication is currently not possible (yes in S 2018 ), the autonomous robot  11 B abandons communication with other robots with which communication is currently not possible, and selects an autonomous robot to be a support target, on the basis of the other robot information of the other autonomous robots with which communication is currently possible, acquired in S 2011  (S 2019 ). 
     As described above, the autonomous robot  11 B, when having completed the tasks therefor, performs processing to select an autonomous robot to be a support target, on the basis of other robot information of other autonomous robots with which communication is currently possible, and other robot information acquired by once again communicating with other autonomous robots with which communication is currently not possible, from among other robot information stored while executing tasks. 
     In S 2011 , in the case where the autonomous robot  11 B communicates with another autonomous robot with which communication is possible and the other robot information of the other autonomous robot is already stored, it has been described that the other robot information that is stored is updated; however, it should be noted that the present disclosure is not restricted thereto. The autonomous robot  11 B may sequentially accumulate acquired other robot information in the other robot information that is stored. In this case, location information (local robot reception location) from which it has been possible to communicate with another autonomous robot can be sequentially accumulated. Thus, in the case where the autonomous robot  11 B attempts communication with another autonomous robot with which communication is currently not possible, using location information (local robot reception location) from when communication was last possible, but said communication is not successful, in addition, it becomes possible for the autonomous robot  11 B to once again attempt communication with the other autonomous robot with which communication is currently not possible, using location information (local robot reception location) from when communication was next possible following on from said last time. 
     Furthermore, in S 2013 , in the case where there is a plurality of other autonomous robots with which communication is currently not possible, the autonomous robot  11 B may extract the local robot location information associated with the other robot information of each of the plurality of other autonomous robots, to generate a route such that it is possible to move to all of the plurality of other autonomous robots in an efficient manner. The autonomous robot  11 B is thereby able to shorten the movement time, and is therefore able to speed up the resumption of communication with autonomous robots with which communication is currently not possible. 
     Furthermore, in S 2013 , in the case where there is a large number of other autonomous robots with which communication is currently not possible, the autonomous robot  11 B may select a portion of other autonomous robots from thereamong and move thereto. In the case where there is a large number of other autonomous robots with which communication is currently not possible, a lot of movement time is required for movement in order to communicate with all of the autonomous robots, and time is taken up for matters other than the original objective of supporting other autonomous robots. In this case, the autonomous robot  11 B, for example, may select only the other autonomous robots having a local robot reception location within a prescribed distance from the current location of the autonomous robot  11 B. Furthermore, the autonomous robot  11 B may select only the other autonomous robots having a local robot reception location to which movement is possible within a prescribed period from the current location of the autonomous robot  11 B. Furthermore, other autonomous robots with which the total movement distance or total movement time of the autonomous robot  11 B is within a prescribed range may be selected, or other autonomous robots with which the time during which communication with the autonomous robot  11 B has been interrupted is within a prescribed period may be selected. 
     By adopting this kind of configuration, it is not necessary to spend more than the necessary time for the autonomous robot  11 B to once again communicate with other robots with which communication is currently not possible in order to acquire information from the other autonomous robots, and it becomes possible to spend a considerable amount of time supporting autonomous robots, which is the original objective. 
     Furthermore, it is also feasible for the autonomous robot  11 B to detect a new autonomous robot that is different from the intended other autonomous robot during movement between S 2014  and S 2015 . In this case, the autonomous robot  11 B may acquire other robot information from the detected new autonomous robot, store the other robot information in the storage unit  115 B, and perform processing to select a support-target autonomous robot in S 2017  or S 2019 . It is thereby possible for a support-target autonomous robot to be selected using a greater amount of other robot information. 
     [Effects, Etc.] 
     As described above, according to the present embodiment, it is possible to acquire not only the other robot information of other autonomous robots with which communication is currently possible, but also other robot information acquired by communication being attempted once again with other autonomous robots with which communication is currently not possible, from among the other robot information of other autonomous robots stored while executing tasks, and to perform processing to select an autonomous robot to be a support target. 
     It is thereby possible to realize a movement control method and a movement control device with which it is possible for an autonomous robot to cooperate with a greater number of other autonomous robots to execute tasks even in the case where the other autonomous robots with which communication is possible dynamically change. 
     Specifically, in the present embodiment, in order to once again acquire the information of other autonomous robots with which communication is currently not possible, the autonomous robot  11 B moves in such a way that it becomes possible to communicate once again with other autonomous robots with which communication is currently not possible. In other words, the autonomous robot  11 B, upon receiving other robot information from another autonomous robot while executing tasks of the autonomous robot  11 B, acquires location information for the autonomous robot  11 B, and associates and stores the received other robot information and the acquired location information for the autonomous robot  11 B (local robot reception location). The autonomous robot is thereby able to leave location information (local robot reception location) from when it had been possible to communicate with the other autonomous robot. In the case where it is desired for communication to once again be performed with another autonomous robot with which communication is currently not possible, the autonomous robot  11 B extracts the location information (local robot reception location) from when it had been previously possible to communicate with the other autonomous robot with which communication is currently not possible, and moves toward that location, and by doing so is able to attempt communication once again with the other autonomous robot with which communication had not been possible. 
     It should be noted that, since the other autonomous robots are also moving, it is also feasible for communication to not be possible even when the autonomous robot  11 B has moved to the extracted location information (local robot reception location). That is, in the case where a long time has elapsed from an interruption in communication with another autonomous robot with which communication is currently not possible, there is a possibility of the other autonomous robot with which communication is currently not possible having moved a considerable extent. Therefore, there is a high possibility of the autonomous robot  11 B not being able to communicate with the other autonomous robot even when having moved to the extracted location information (local robot reception location). 
     However, in the case where not much time has elapsed from communication with the other autonomous robot with which communication is currently not possible having been interrupted, it is feasible for the other autonomous robot to have not moved very far, and therefore there is a high possibility of the autonomous robot  11 B being able to communicate upon having moved to the extracted location information (local robot reception location). 
     Consequently, it is thought that the movement control method and the like of the present embodiment are particularly effective in the case where not much time has elapsed from communication between the autonomous robot  11 B and another autonomous robot with which communication is currently not possible having been interrupted. 
     (Modified Example 1) 
     In the present embodiment, a description has been given in which the autonomous robot  11 B requests other autonomous robots for other robot information of the other autonomous robots; however, the present disclosure is not necessarily restricted to this configuration. 
     For example, each of the other autonomous robots may periodically transmit other robot information thereof, and receive other robot information from each of the other autonomous robots within the communication range of the autonomous robot  11 B. 
     (Modified Example 2) 
     In the present embodiment, a description has been given in which the autonomous robot  11 B periodically communicates with other autonomous robots within a communication range while executing tasks thereof and receives other robot information; however, the present disclosure is not restricted thereto. 
     For example, the autonomous robot  11 B may communicate with another autonomous robot to acquire the other robot information thereof only when having newly detected the other autonomous robot. The autonomous robot  11 B may have any kind of configuration as long as it is possible to acquire other robot information from other autonomous robots within the communication range while executing tasks for the coverage region  21  thereof. 
     (Modified Example 3) 
     In the present embodiment, when the autonomous robot  11 B has acquired other robot information from another autonomous robot when having completed tasks, the location of the autonomous robot  11 B at that time has been included; however, said location does not have to be included. 
     This is because, although it is invariably necessary for the autonomous robot  11 B to associate other robot information and location information thereof when having received information from another autonomous robot while executing tasks, it is not necessary for the location thereof (local robot reception location) to be associated with other robot information acquired from another autonomous robot when the tasks have been completed. 
     (Modified Example 4) 
     In the present embodiment, a description has been given in which the autonomous robot  11 B, upon receiving other robot information from another autonomous robot while executing tasks of the autonomous robot  11 B, acquires location information of the autonomous robot  11 B, and associates and stores the received information of the other autonomous robot and the acquired location information of the autonomous robot  11 B; however, the present disclosure is not restricted thereto. 
     The configuration is inconsequential as long as the autonomous robot  11 B is able to retain and refer to location information from the point in time at which it had been possible to communicate with another autonomous robot. 
     (Modified Example 5) 
     In the present embodiment, a description has been given in which the autonomous robot  11 B periodically communicates with other autonomous robots within a communication range while executing tasks for the coverage region  21  of the autonomous robot  11 B, and acquires and stores information of the other autonomous robots; however, the present disclosure is not restricted thereto. 
     For example, there are cases where the autonomous robot  11 B, when selecting another autonomous robot for a support target after having completed tasks, possesses other robot information received from another autonomous robot that was within the communication range of the autonomous robot  11 B immediately before completing the tasks thereof. In these cases, the autonomous robot  11 B does not have to newly acquire other robot information from the other autonomous robot after having completed the tasks. The autonomous robot  11 B may then deem the other robot information received immediately before completing the tasks as the most up-to-date information, and perform selection processing for a support-target autonomous robot on the basis of that other robot information. 
     It is thereby possible to limit the autonomous robot  11 B acquiring other robot information from the other autonomous robot twice, namely immediately before and immediately after completing the tasks. Since the period between immediately before and immediately after task completion is short, it is thought that there is a low possibility of there being a considerable difference between the information received from the other autonomous robot immediately before the task completion and the other robot information received from the other autonomous robot immediately after the task completion. Consequently, even in this manner, it is thought that it is possible for the autonomous robot  11 B to appropriately select a support-target autonomous robot. 
     (Modified Example 6) 
     In the present embodiment, a description has been given in which, if other robot information of another autonomous robot with which communication is currently not possible is present in the storage unit  115 B, the autonomous robot  11 B moves to the local robot reception location associated with that other robot information; however, the present disclosure is not restricted thereto. 
     In the case where other robot information of another autonomous robot with which communication is currently not possible is present, the autonomous robot  11 B may perform determination processing with regard to performing movement if the distance between the current location thereof and the local robot reception location included in the other robot information of the other autonomous robot with which communication is currently not possible is within a prescribed distance. The reason being that, in the case where the local robot reception location associated with the other robot information is far from the current location of the autonomous robot  11 B, it takes a long time for the autonomous robot  11 B to move, and there is a high possibility that the other autonomous robot with which communication is to be attempted may have moved a considerable extent while the autonomous robot  11 B is moving, and that communication may no longer be possible even when the autonomous robot  11 B has moved to the local robot reception location. 
     In this way, according to the present modified example, the autonomous robot  11 B is able to move only in the case where there is a high possibility of communicating with the other autonomous robot with which communication is currently not possible, and is therefore able to limit unnecessary movement in the case where there is a low possibility of being able to communicate with the other autonomous robot despite having moved. 
     (Modified Example 7) 
     It should be noted that, in the present embodiment, it is also feasible for the autonomous robot  11 B to become unable to communicate with the other autonomous robots  13  and  14  with which communication had been currently possible, while moving toward the location (local robot reception location) from which communication was last performed with the autonomous robot  12  with which communication is currently not possible. 
     In this case, there is a decrease in the other robot information of the autonomous robots  13  and  14  with which communication had been currently possible that is to be used when the autonomous robot  11 B selects a support-target autonomous robot. That is, the autonomous robot  11 B becomes unable to use the other robot information of the autonomous robots  13  and  14  with which communication has become not possible while moving, despite becoming able to communicate with the autonomous robot  12  with which communication had been currently not possible, and it is therefore also feasible that the autonomous robot  11 B may not be able to appropriately select a support-target autonomous robot. 
     Therefore, the autonomous robot  11 B may, at the point in time at which the autonomous robot  11 B completes its tasks, use only the other robot information of the other autonomous robots  13  and  14  with which communication is currently possible, to temporarily determine a support-target autonomous robot. The autonomous robot  11 B may then start moving in order to communicate with the autonomous robot  12  with which communication is currently not possible, and, when it has become possible to communicate with the autonomous robot  12 , acquire other robot information from the autonomous robot  12  with which communication has become possible. 
     In this case, the autonomous robot  11 B may perform the alteration processing described in embodiment 1, at the point in time when having acquired the other robot information from the autonomous robot  12 . 
     According to this configuration, it becomes possible for the autonomous robot  11 B to select a support-target autonomous robot on the basis of the other robot information of the autonomous robots  13  and  14  with which communication had been possible at the point in time at which the autonomous robot  11 B completed its tasks, and the other robot information obtained by communicating once again with the autonomous robot  12  with which communication had not been possible. 
     (Embodiment 3) 
     In the present embodiment, a description is given regarding a different example from embodiment 2 regarding the case where an autonomous robot  110 , while executing and when having completed tasks thereof, selects a support-target autonomous robot from among other autonomous robots with which communication had been possible. 
     In embodiment 2, a description was given regarding an example of the case where the autonomous robot  11 B selects a support-target robot on the basis of other robot information of other autonomous robots with which communication is currently possible when having completed tasks for the coverage region thereof, and other robot information acquired by attempting communication once again with another autonomous robot with which communication is currently not possible. 
     In the present embodiment, a description is given regarding an example of the case where the autonomous robot  110  selects a support-target robot on the basis of the task information of another autonomous robot with which communication is currently possible when having completed tasks for the coverage region thereof, and estimated task progress information obtained by estimating the current task progress information of another autonomous robot with which communication is currently not possible. 
     [Functional Configuration of Autonomous Robot] 
     Hereinafter, as with embodiments 1 and 2, the functional configuration of the autonomous robot  11 C will be representatively described. 
       FIG. 16  is a block diagram depicting an example of the functional configuration of an autonomous robot in embodiment 3. The same elements as in  FIGS. 2 and 10  are denoted by the same reference numbers, and a detailed description thereof is omitted. 
     The autonomous robot  11 C depicted in  FIG. 16  is different from the autonomous robot  11  depicted in  FIG. 2  with regard to the configurations of a control unit  112 C and a storage unit  115 C. 
     [Control Unit  112 C] 
       FIG. 17  is a block diagram depicting an example of the detailed configuration of the control unit depicted in  FIG. 16 . The same elements as in  FIG. 3  are denoted by the same reference numbers, and a detailed description thereof is omitted. 
     As depicted in  FIG. 17 , the control unit  112 C is provided with a selection processing unit  1121 C, a movement control unit  1122 , an alteration determination unit  1123 , and a notification control unit  1124 . The control unit  112 C is different from the control unit  112  depicted in  FIG. 3  with regard to the configuration of the selection processing unit  1121 C. 
     The selection processing unit  1121 C is provided with the functions of the selection processing unit  1121 . The selection processing unit  1121 C, in addition, selects a support-target robot from within a robot group, which is a plurality of robots other than the autonomous robot  11 C (first robot) with which communication is currently possible and has been possible in the past with the autonomous robot  11 C (first robot). 
     In the present embodiment, the selection processing unit  1121 C uses at least one item of other robot information of a plurality of autonomous robots with which communication has been possible in the past with the autonomous robot  11 C (first robot), and the current location of the autonomous robot  11 C (first robot), to estimate the remaining tasks for a point in time at which the autonomous robot  11 C (first robot) will have moved to the at least one other autonomous robot. In this way, the selection processing unit  1121 C acquires the remaining tasks of each robot of a robot group that includes the at least one autonomous robot. Here, the aforementioned other robot information is stored in the storage unit  115 C. 
     It should be noted that, in order to estimate the current tasks and remaining tasks of the information of another autonomous robot with which communication is currently not possible, it is sufficient to have the other robot information last received from the other autonomous robot with which communication is currently not possible and the reception time at which that information was last received. The reason being that, with these items of information, it is possible to use the other robot information last received from the other autonomous robot with which communication is currently not possible, to estimate the amount of tasks executed by the other autonomous robot with which communication is currently not possible in the time that has elapsed from the reception time at which the other robot information was last received to the current time. In this way, the autonomous robot  110  is able to estimate the current task progress of the other autonomous robot with which communication is currently not possible. 
     [Storage Unit  1150 ] 
     Next,  FIG. 18  will be used to describe the information stored in the storage unit  115 C of the autonomous robot  110 . 
       FIG. 18  is a drawing conceptually depicting the information stored in the storage unit of an autonomous robot in embodiment 3. The same elements as in  FIG. 4  are denoted by the same reference numbers, and a detailed description thereof is omitted. 
     As in embodiment 1, the storage unit  115 C stores local robot information  1151 , a selection standard  1153 , and other robot information  1152 C that is based on information transmitted from other autonomous robots. 
     The storage unit  115 C is different from the storage unit  115  depicted in  FIG. 4  in that the information included in the other robot information  1152 C is different, and that other robot information of other autonomous robots received while the autonomous robot  110  (first robot) is executing tasks with respect to the coverage region  21  (first coverage region) is stored. In the present embodiment, the autonomous robot  110 , while executing tasks for the coverage region  21  thereof, periodically communicates with other autonomous robots within a communication range, and stores acquired other robot information of the other autonomous robots. 
     (Details of the Other Robot Information) 
     As depicted in  FIG. 18 , the other robot information  1152 C includes information indicating a reception time and a communication status in addition to the information included in the other robot information  1152  depicted in  FIG. 4 . The communication status is information indicating the current communication status of each of the other autonomous robots. The reception time is information indicating the time at which the autonomous robot  110  has received other robot information from another autonomous robot, and is acquired by the time measurement unit  116 . The reception time is associated with other robot information and stored, such as being included in other robot information. 
       FIG. 19  is a drawing depicting an example of the other robot information depicted in  FIG. 18 . The same elements as in  FIG. 5  are denoted by the same reference numbers, and a detailed description thereof is omitted. 
       FIG. 19  depicts that the information of autonomous robots  12 C,  13 C, and  14 C is stored as the other robot information  1152 C in the storage unit  115 C. Furthermore,  FIG. 19  depicts that, at present, the autonomous robot  110  is able to communicate with the autonomous robots  13 C and  14 C but is unable to communicate with the autonomous robot  12 C. Here, the other robot information of the autonomous robot  12 C depicted in  FIG. 19  was received when the autonomous robot  110  was previously able to communicate with the autonomous robot  12 C. 
     The autonomous robot  110  configured as described above selects another autonomous robot to be a support target with consideration being given not only to the other robot information of autonomous robots with which communication is currently possible, but also to the current task progress estimated on the basis of the other robot information of another autonomous robot with which communication is currently not possible, from among the other robot information of other autonomous robots stored while executing tasks. 
     [Operation of Autonomous Robot] 
     Next, an overview of the operation of the autonomous robot  110  configured as described above will be described. 
       FIGS. 20A and 20B  are drawings conceptually depicting a situation for autonomous robots that make up the robot system in embodiment 3.  FIG. 20A  depicts an example of a situation in which the autonomous robots  110  to  14 C are executing tasks for coverage regions thereof.  FIG. 20B  depicts an example of the situation when the autonomous robot  110  has completed its tasks. The same constituent elements as in  FIG. 1  are denoted by the same reference numbers, and a description thereof is omitted. 
     A communication range  313 C of  FIG. 20A  and a communication range  314 C of  FIG. 20B  indicate communication ranges in which the autonomous robot  110  is able to communicate. As depicted in  FIG. 20A , the autonomous robot  110  while executing tasks is able to communicate with the other autonomous robots  12 C and  13 C that are within the communication range  313 C. However, as depicted in  FIG. 20B , the autonomous robot  110  when having completed the tasks is able to communicate with the autonomous robots  13 C and  14 C that are within the communication range  314 C but is not able to communicate with the autonomous robot  12 C with which communication had been possible in  FIG. 20A . 
     Therefore, the autonomous robot  110  depicted in  FIG. 20B , upon completing the tasks for the coverage region  21  assigned thereto, selects an autonomous robot to be a support target on the basis of the other robot information of the autonomous robots  13 C and  14 C with which communication is currently possible, and the other robot information of the autonomous robot  12 C that is another autonomous robot with which communication is currently not possible, from among the information of other autonomous robots stored while executing the tasks. 
     (Details of the Selection Processing) 
     Next, the details of the selection processing in the present embodiment will be described using  FIG. 21 . 
       FIG. 21  is a flowchart for describing a detailed example of the selection processing of an autonomous robot in embodiment 3.  FIG. 21  depicts an example of selection processing in which the autonomous robot  110 , when having completed its tasks, selects another autonomous robot for a support target. 
     First, the autonomous robot  110 , when having completed the tasks assigned thereto, communicates with each of the other autonomous robots with which communication is currently possible, and acquires the other robot information thereof (S 2021 ). 
     In the present embodiment, the autonomous robot  110  communicates with the autonomous robots  13 C and  14 C, acquires the other robot information  1152 C, and stores this in the storage unit  115 C. The other robot information  1152 C acquired by the autonomous robot  110  is, for example, robot-specific information that includes identification information and specification information of the autonomous robots  13 C and  14 C, task information that is information relating to tasks, a reception time, and the like. It should be noted that the autonomous robot  110 , when having completed its tasks, does not have to acquire the reception time as the other robot information  1152 C. This is because it is sufficient as long as the association between the reception time and the robot-specific information or task information received from another autonomous robot is implemented while tasks are being executed, and therefore the reception time from when the tasks have been completed is not absolutely necessary. 
     Next, the autonomous robot  110  confirms with the storage unit  115 C to determine whether there is other robot information of other autonomous robots with which communication is currently not possible in the storage unit  115 C (S 2022 ). 
     In S 2022 , in the case where there is no other robot information of other autonomous robots with which communication is currently not possible in the storage unit  115 C (no in S 2022 ), a support-target robot is selected on the basis of the other robot information of the other autonomous robots with which communication is currently possible (S 2023 ). It should be noted that, in S 2022 , the same processing as that of S 202  to S 214  described in  FIG. 7  is performed. Since S 202  to S 214  have been described above, a description thereof is omitted here. 
     However, in S 2022 , in the case where there is other robot information of another autonomous robot with which communication is currently not possible in the storage unit  115 C (yes in S 2022 ), the reception time at which communication was last performed with the other autonomous robot with which communication is currently not possible is acquired (S 2024 ). In the present embodiment, the autonomous robot  110  extracts the reception time included in the other robot information of the autonomous robot  12 C with which communication is currently not possible, from the storage unit  115 C. 
     Next, the autonomous robot  110  acquires the current time (S 2025 ). In the present embodiment, the autonomous robot  110  acquires current time information from the time measurement unit  116 . 
     Next, the autonomous robot  110  performs processing to estimate the current task progress information of the other autonomous robot with which communication is currently not possible in S 2026  to S 2027 . 
     In S 2026 , the task processing amount from the last reception time of the other autonomous robot with which communication is currently not possible to the current time is estimated (S 2026 ). In the present embodiment, first, the autonomous robot  110  uses the reception time extracted in S 2024  and the current time information acquired in S 2025  to calculate the time from said reception time to the current time. Next, the autonomous robot  110  extracts information on the task processing amount per unit time of the autonomous robot  12 C with which communication is currently not possible, from the other robot information  1152 C in the storage unit  115 C. The autonomous robot  110  then multiplies the extracted task processing amount per unit time and the aforementioned calculated time to thereby estimate the task processing amount in the aforementioned time of the autonomous robot  12 C with which communication is currently not possible. 
     Then, in S 2027 , the autonomous robot  110  estimates the current amount of remaining tasks of the other autonomous robot with which communication is currently not possible. It should be noted that, in the case where there is a plurality of other robot information of other autonomous robots with which communication is currently not possible, the current amount of remaining tasks is estimated for each of the other autonomous robots. In the present embodiment, first, the autonomous robot  110  extracts task-incomplete region information from the other robot information of the autonomous robot  12 C with which communication is currently not possible. Next, the autonomous robot  110  uses the extracted task-incomplete region information and the task processing amount in the aforementioned time estimated in S 2026  to estimate the current amount of remaining tasks. 
     Next, the autonomous robot  110  determines whether there are remaining tasks for the other autonomous robot with which communication is currently not possible (S 2028 ). In the present embodiment, the autonomous robot  110  determines whether there are remaining tasks for the autonomous robot  12 C with which communication is currently not possible, from the current amount of remaining tasks of the autonomous robot  12 C, estimated in S 2027 . 
     In S 2028 , in the case where there are no remaining tasks (no in S 2028 ), an autonomous robot to be a support target is selected on the basis of the other robot information of the other autonomous robots with which communication is currently possible, acquired in S 2021  (S 2029 ). In the present embodiment, in the case where the current amount of remaining tasks estimated in S 2027  is less than 0, the autonomous robot  110  deems that the autonomous robot  12 C with which communication is currently not possible has completed the tasks for the coverage region, and processing advances to S 2029 . It should be noted that, in S 2029 , the same processing as that of S 202  to S 214  described in  FIG. 7  is performed. Since S 202  to S 214  have been described above, a description thereof is omitted here. 
     However, in S 2028 , in the case where there are remaining tasks (yes in S 2028 ), a support-target autonomous robot is selected according to the task information of the other autonomous robots with which communication is currently possible and the task information estimated for the other autonomous robot with which communication is currently not possible (S 2030 ). In the present embodiment, in the case where the current amount of remaining tasks estimated S 2027  is greater than 0, the autonomous robot  110  deems that there is a task-incomplete region remaining for the autonomous robot  12 C with which communication is currently not possible, and uses task-related information such as the task-incomplete region information of the autonomous robots  13 C and  14 C with which communication is currently possible, and the current amount of remaining tasks estimated for the autonomous robot  12 C with which communication is currently not possible, to select a support-target autonomous robot. It should be noted that, in S 2030 , the same processing as that of S 202  to S 214  described in  FIG. 7  is performed. Since S 202  to S 214  have been described above, a description thereof is omitted here. 
     As described above, after having completed the tasks for the coverage region thereof, the autonomous robot  110  selects an autonomous robot to be a support target, on the basis of the other robot information of other autonomous robots with which communication is currently possible, and estimated task progress information for other autonomous robots with which communication is currently not possible. As described above, this estimated task progress information is the current task progress information of another autonomous robot with which communication is currently not possible, estimated using the other robot information of the other autonomous robot with which communication is currently not possible that has been stored while the autonomous robot  110  has been executing tasks. 
     [Effects, Etc.] 
     As described above, according to the present embodiment, in order to estimate the task progress of another autonomous robot when communication is not possible, the autonomous robot  110 , when having received information from the other autonomous robot while executing its own tasks, stores other robot information that includes time information relating to said reception. Specifically, the autonomous robot  110 , upon receiving other robot information from the other autonomous robot while executing its own tasks, stores the other robot information with a reception time indicating a time acquired by the time measurement unit  116  being included therein. 
     The autonomous robot  110  is thereby able to select an autonomous robot to be a support target with consideration being given not only to the other robot information of other autonomous robots with which communication is currently possible, but also to estimated task progress information for another autonomous robot with which communication is currently not possible, estimated using the other robot information of the other autonomous robot stored while executing tasks. 
     The autonomous robot  110  is thereby able to use a greater amount of other robot information to select an autonomous robot to be a support target, and is therefore able to select a more appropriate autonomous robot to be a support target. 
     (Modified Example 1) 
     In the present embodiment, a description has been given in which the autonomous robot  110  estimates task progress information for another autonomous robot with which communication is not possible; however, the present disclosure is not restricted thereto. For example, the autonomous robot  110  may estimate the location information of another autonomous robot with which communication is not possible. Regarding a method for estimating location information, for example, the autonomous robot  110  may, when acquiring other robot information from another autonomous robot, also acquire and store route information relating to the execution of tasks for the coverage region of the other autonomous robot. The autonomous robot  110 , when having completed its own tasks, is thereby able to estimate the location of the other autonomous robot with which communication is not possible, on the basis of the acquired route information. For example, the autonomous robot  110  is able to calculate the distance from the reception time at which information was last acquired from the other autonomous robot with which communication is not possible, to the present time, on the basis of a movement speed indicated in the specification information of the other autonomous robot. The autonomous robot  110  is then able to estimate the current location of the other autonomous robot as being a location to which movement has been made by the calculated distance, on the basis of the route information, from the location information of the other autonomous robot from when information was last acquired from the other autonomous robot. 
     In this way, according to the present modified example, the autonomous robot  110  is able to estimate location information and task progress information of another autonomous robot with which communication is not possible, and is therefore able to more appropriately select an autonomous robot to be a support target. 
     (Modified Example 2) 
     In the present embodiment, a description has been given in which the autonomous robot  110  estimates the current task progress of another autonomous robot with which communication is currently not possible. However, the accuracy of this estimated task progress changes depending on the time from the last reception time with the autonomous robot with which communication is currently not possible to the current time. 
     That is, if there is a short length of time from the last reception time with the other autonomous robot with which the autonomous robot  110  currently cannot communicate to the current time, it is thought that the estimated task progress is accurate with there being no considerable difference with the actual task progress. On the other hand, if there is a long length of time from the last reception time with the other autonomous robot with which the autonomous robot  110  currently cannot communicate to the current time, it is thought that the estimated task progress is low in accuracy with there possibly being a considerable difference with the actual task progress. Therefore, when using a task progress estimated when the aforementioned time is long, to perform selection processing for a support-target autonomous robot, it is feasible that the autonomous robot  110  may select an autonomous robot that is inappropriate as a support target. 
     Therefore, the autonomous robot  110  may estimate the task progress for another autonomous robot with which communication is currently not possible, when the aforementioned time is short and it is possible to estimate that the accuracy of the estimated task progress will be high. Specifically, the autonomous robot  110  may estimate the current task progress for another autonomous robot with which communication is currently not possible, only in the case where the aforementioned time is within a prescribed period. 
     Thus, this method can be used by the autonomous robot  110  only when there is a high possibility of the estimated task progress being accurate, and it therefore becomes possible to suppress the development of a situation in which the support-target autonomous robot selected by the autonomous robot  110  is actually inappropriate as a support target. 
     (Modified Example 3) 
     It should be noted that there is no restriction to the case of the aforementioned modified example 2, and the autonomous robot  110  may, with regard to the time from the reception time at which reception was last performed with another autonomous robot with which communication is not possible to the current time, assign priority levels such that the priority level increases as the time becomes shorter, and select support-target autonomous robots in order from other autonomous robots that have reception times of a high priority time. 
     Modified example 2 is used only when there is a high possibility of the estimated task progress being accurate. However, in the present modified example, even in the case where the possibility of the estimated task progress being accurate is not high, this method can be used as long as support-target autonomous robots are in descending order of priority level. 
     That is, in the case where the autonomous robot  110  has not been able to select another autonomous robot to be a support target with the method of modified example 2, there is risk of an idle state being entered. However, the method of the present modified example can be used by the autonomous robot  110  even in the case where the possibility of the estimated task progress being accurate is not high, and it is therefore possible to reduce the possibility of entering an idle state. 
     (Modified Example 4) 
     Furthermore in the present embodiment, a description has been given in which, after having completed the tasks for the coverage region thereof, the autonomous robot  110  selects an autonomous robot to be a support target on the basis of the other robot information of other autonomous robots with which communication is currently possible, and estimated task progress information for other autonomous robots with which communication is currently not possible; however, the present disclosure is not restricted thereto. This method may be used in combination with the method described in embodiment 2. In this case, the autonomous robot  110  may, while executing tasks thereof, additionally include and store location information thereof in other robot information received from another autonomous robot. 
     It should be noted that numerous methods are feasible according to system specifications regarding determining the situations in which to use processing for once again acquiring other robot information of another autonomous robot with which communication with the autonomous robot  110  is currently not possible, and processing for estimating the current task progress. 
     For example, the autonomous robot  110  may determine whether the time from the task completion time thereof to the last reception time with an autonomous robot with which communication is currently not possible is within a prescribed period. If within the prescribed period, the autonomous robot  110  may move to the location (place) where it was last possible to communicate with the autonomous robot with which communication is currently not possible in order to communicate with said autonomous robot with which communication is currently not possible, and if outside of the prescribed period, the autonomous robot  110  may estimate the current task status of the autonomous robot with which communication is currently not possible. 
     The reason being that, in the case where a considerable length of time has elapsed from the interruption in communication between the autonomous robot  110  and the other autonomous robot with which communication is currently not possible, it is thought that the other autonomous robot with which communication is currently not possible will have moved a considerable extent during that elapsed time. That is, in the case where the elapsed time is considerable, it is thought that there is a high possibility of not being able to communicate with the other robot even if the autonomous robot  110  moves to attempt communication. 
     In this way, the autonomous robot  110  is not only able to limit movement in the case where the elapsed time is considerable but is also able to, instead of simply not moving, use the estimated current task progress of the other autonomous robot with which communication is currently not possible, in the processing to select an autonomous robot to be a support target. 
     In the present modified example, a determination is made as to whether the aforementioned time is within a prescribed period; however, it should be noted that the present disclosure is not restricted thereto. The autonomous robot  110  may determine whether the distance from the location thereof when having completed its tasks to the location from which communication had last been possible with the other autonomous robot with which communication is currently not possible is within a prescribed distance. The same effect can be obtained also in this case. 
     Furthermore, in the present modified example, the autonomous robot  110 , when having completed its own tasks, may estimate the current task progress of another autonomous robot with which communication is currently not possible, and only move to another autonomous robot estimated to still have remaining tasks on the basis of the estimated task progress. This is because it is thought that other autonomous robots that have completed their tasks will be moving to provide support to other autonomous robots. 
     It is thereby possible for the autonomous robot  110  to limit movement to other autonomous robots estimated to have already completed their tasks. 
     Furthermore, in the present modified example, the autonomous robot  110 , when having completed its own tasks, may move to communicate with another autonomous robot with which communication is currently not possible, in a range within which it is possible to maintain communication with all of the other autonomous robots with which communication is currently possible. In this case, when it is no longer possible to maintain communication with all of the other autonomous robots with which communication is currently possible, the autonomous robot  110  may discontinue movement to the other autonomous robot with which communication is currently not possible, and estimate the current tasks. 
     The autonomous robot  110  is thereby able to reliably use the other robot information of all of the other autonomous robots with which communication is currently possible, and it is therefore possible to prevent a decrease in the information of the autonomous robots with which communication is currently possible. 
     (Embodiment 4) 
     In embodiment 4, a description is given regarding an example of the case where an autonomous robot  11 D, when having completed its own tasks, has not been able to select an autonomous robot to be a support target, from among other autonomous robots with which communication is possible. Hereinafter, a description will be given regarding an example of the case where the autonomous robot  11 D, after having completed its tasks, moves autonomously to newly acquire other robot information of other autonomous robots, and selects an autonomous robot to be a support target. 
     [Functional Configuration of Autonomous Robot] 
     Hereinafter, as with embodiments 1 to 3, the functional configuration of the autonomous robot  11 D will be representatively described. 
       FIG. 22  is a block diagram depicting an example of the functional configuration of an autonomous robot in embodiment 4. The same elements as in  FIG. 2  are denoted by the same reference numbers, and a detailed description thereof is omitted. 
     The autonomous robot  11 D depicted in  FIG. 22  is different from the autonomous robot  11  depicted in  FIG. 2  with regard to the configuration of a control unit  112 D. 
     [Control Unit  112 D] 
       FIG. 23  is a block diagram depicting an example of the detailed configuration of the control unit depicted in  FIG. 22 . The same elements as in  FIG. 3  are denoted by the same reference numbers, and a detailed description thereof is omitted. 
     As depicted in  FIG. 23 , the control unit  112 D is provided with a selection processing unit  1121 D, a movement control unit  1122 D, an alteration determination unit  1123 , and a notification control unit  1124 . The control unit  112 D is different from the control unit  112  depicted in  FIG. 3  with regard to the configurations of the selection processing unit  1121 D and the movement control unit  1122 D. 
     The selection processing unit  1121 D is provided with the functions of the selection processing unit  1121 . The selection processing unit  1121 D instructs the movement control unit  1122 D for the autonomous robot  11 D (first robot) to be made to move outside of the coverage region  21  (outside of the first coverage region) in the case where tasks for the coverage region  21  (first coverage region) have been completed and when the autonomous robot  11 D (first robot), which is within the coverage region  21  (first coverage region), is not able to select a support-target robot from within a robot group, such as in the case where there are no acquired remaining tasks for other autonomous robots and in the case where there are no other autonomous robots with which communication is possible when the autonomous robot  11 D has completed its tasks. 
     Furthermore, when it has become possible, while the autonomous robot  11 D (first robot) is moving, for the autonomous robot  11 D to communicate with another autonomous robot not included in a robot group with which communication had been possible when the autonomous robot  11 D completed its tasks, from among a plurality of other autonomous robots making up the robot system, the selection processing unit  1121 D receives other robot information that includes location information indicating a current location and task information indicating a task progress status from the other autonomous robot not included in the robot group. 
     Furthermore, the selection processing unit  1121 D uses the current location of the autonomous robot  11 D (first robot) and the received other robot information of the other autonomous robot not included in the robot group, to acquire the remaining tasks for a point in time at which the autonomous robot  11 D (first robot) will have moved to the current location of the other autonomous robot not included in the robot group. Furthermore, the selection processing unit  1121 D selects the robot not included in the robot group, as a support-target robot on the basis of the acquired remaining tasks. 
     The movement control unit  1122 D is provided with the functions of the movement control unit  1122 . The movement control unit  1122 D, in addition, causes the autonomous robot  11 D (first robot) to move outside of the coverage region  21  (first coverage region) in accordance with an instruction from the selection processing unit  1121 D. 
     [Operation of Autonomous Robot] 
     Next, an overview of the operation of the autonomous robot  11 D configured as described above will be described. 
       FIGS. 24A and 24B  are drawings conceptually depicting a situation for autonomous robots that make up the robot system in embodiment 4. The same constituent elements as in  FIG. 1  are denoted by the same reference numbers, and a description thereof is omitted. 
       FIG. 24A  depicts an example of a situation for when the autonomous robot  11 D has completed tasks for the coverage region  21  thereof. A communication range  315  indicates the communication range in which the autonomous robot  11 D is able to communicate, and the autonomous robot  11 D depicted in  FIG. 24A  is able to communicate with autonomous robots  12 D,  13 D, and  14 D that are within the communication range  315 .  FIG. 24B  conceptually depicts an example of a situation in which the autonomous robot  11 D has moved outside of the coverage region  21  thereof and newly detected another autonomous robot. The autonomous robot  11 D depicted in  FIG. 24B  is able to communicate with the autonomous robots  12 D,  13 D,  14 D, and  16 D that are within a communication range  316 . 
     In the present embodiment, the autonomous robot  11 D depicted in  FIG. 24A  communicates with the autonomous robots  12 D,  13 D, and  14 D that are within the communication range  315 , and uses received other robot information that includes robot-specific information, task information, location information, and the like, to perform selection processing to select an autonomous robot to be a support target. This selection processing is as described in embodiment 1, and a description thereof is therefore omitted here. 
     The autonomous robot  11 D depicted in  FIG. 24A  then, as a result of having performed the selection processing, deems that it is not necessary to provide support to any of the autonomous robots  12 D,  13 D, or  14 D, and is not able to select an autonomous robot to be a support target. 
     However, this is merely the result of having carried out selection processing for an autonomous robot to be a support target, using the other robot information of other autonomous robots that are within a communication region, at the location at which the autonomous robot  11 D depicted in  FIG. 24A  completed its tasks. That is, there is also a possibility that the autonomous robot  11 D, by moving to a location that is different from the aforementioned location and performing selection processing, will be able to select an appropriate autonomous robot as a support target. 
     Therefore, the autonomous robot  11 D depicted in  FIG. 24A  moves outside of the coverage region  21  thereof to obtain information of another autonomous robot. The autonomous robot  11 D depicted in  FIG. 24B  then detects another autonomous robot  16  and, upon acquiring the other robot information of the other autonomous robot  16 , once again performs selection processing. This selection processing is as described in embodiment 1, and a description thereof is therefore omitted here. 
     In this way, the autonomous robot  11 D is able to select a support-target autonomous robot by using not only the other robot information of other autonomous robots that are present within the communication range from the location where the autonomous robot  11 D completed its tasks, but also the other robot information of another autonomous robot newly acquired at a place that is different from the aforementioned location. 
     It should be noted that the case where it is not possible to select an autonomous robot to be a support target is not restricted to the aforementioned example case. In other words, feasible situations also include: 1) the case where it is has not been possible to communicate with any of the other autonomous robots, and it has therefore not been possible to acquire all of the information of the other autonomous robots and the selection processing itself has not been possible; 2) the case where it has been possible to acquire the other robot information of other autonomous robots and the selection processing has been performed, but the tasks of the other autonomous robots of the acquired other robot information have already been completed and support is not necessary; and 3) the case where it has been possible to acquire the other robot information of other autonomous robots and the selection processing has been performed, but it has been determined that, while the autonomous robot  11 D has been moving toward another autonomous robot to be a support-target candidate, the tasks of that other autonomous robot have been completed. 
     [Effects, Etc.] 
     As described above, according to the present embodiment, it is possible to realize a movement control method and a movement control device with which it is possible for an autonomous robot to cooperate with a greater number of other autonomous robots to execute tasks even in the case where the other autonomous robots with which communication is possible dynamically change. 
     More specifically, there are cases where the autonomous robot  11 D, after having completed its tasks, has performed selection processing for an autonomous robot to be a support target but is not able to select an autonomous robot to be a support target. In these cases, the autonomous robot  11 D autonomously moves to newly acquire other robot information of other autonomous robots and perform the selection processing once again. The autonomous robot  11 D is thereby able to limit cases in which it is not possible to select an autonomous robot to be a support target by means of the selection processing, and is able to limit an idle state from being entered. 
     It should be noted that, as in embodiments 2 and 3, the autonomous robot  11 D, while executing its tasks, may store the other robot information of other autonomous robots with which communication has been possible. In this case, within the coverage region  21  thereof, the autonomous robot  11 D already possesses information of other autonomous robots with which communication is possible, and therefore may move outside of the coverage region  21  thereof in order to acquire the other robot information of new other autonomous robots besides the aforementioned other autonomous robots. 
     Thus, there is a further increase in the possibility of the autonomous robot  11 D being able to communicate with a new other autonomous robot to acquire other robot information. It then becomes possible for the autonomous robot  11 D to select a support-target autonomous robot on the basis of the newly acquired other robot information. 
     Furthermore, the autonomous robot  11 D may move in the direction in which it is possible to exit to outside of the coverage region with the shortest movement distance from the coverage region  21 . Thus, the autonomous robot  11 D is able to exit to outside of the coverage region  21  more quickly, and is therefore able to acquire the other robot information of a new other autonomous robot outside of the coverage region  21  and perform selection processing once again more quickly. It should be noted that examples of a movement direction for when the autonomous robot  11 D moves outside of the coverage region  21  are not restricted hereto. These other examples will be described as modified examples. 
     (Modified Example 1) 
     The autonomous robot  11 D may use location information included in other robot information to move in a direction in which the density of other robots is low. 
     When selecting a support target, it is determined that the autonomous robots  12 D to  14 D depicted in  FIG. 24A  do not require support, and therefore it is thought that there is a low possibility of encountering a new other autonomous robot when having moved in a direction in which the autonomous robots  12 D to  14 D are present. Therefore, movement is made in a direction in which there is a coverage region that is outside of the coverage region  21  and has been determined as having no other autonomous robots present therein.  FIG. 25  will be used to describe this example. 
       FIG. 25  is a drawing depicting an example of a movement direction for when movement is performed to outside of a coverage region of an autonomous robot in modified example 1 of embodiment 4. 
     It is assumed that the autonomous robot  11 D is additionally provided with a direction sensor, for example, and four quadrants are set as depicted in  FIG. 25 . The autonomous robot  11 D then determines in which quadrant the other autonomous robots (autonomous robots  12 D to  14 D) are present, and moves toward the quadrant having the lowest number of other autonomous robots. 
     It is thereby possible for the autonomous robot  11 D to acquire the other robot information of a new other autonomous robot outside of the coverage region  21  and perform selection processing once again more quickly. 
     It should be noted that the movement direction is not restricted to the case given in the present modified example. This may be combined with an aforementioned case. In other words, the movement direction may be the direction constituting the shortest movement distance with which it is possible to exit to outside of the coverage region with the shortest movement distance from the coverage region  21 , from within the direction of the quadrant having the lowest number of other autonomous robots. 
     (Modified Example 2) 
     In the case where the autonomous robot  11 D acquires information indicating respective coverage regions from other autonomous robots, the autonomous robot  11 D may move toward a region other than the coverage regions of the other autonomous robots. The reason being that it is thought that there is a low possibility of encountering a new other autonomous robot when having moved toward the coverage region of another autonomous robot deemed to not require support during selection processing. 
     Therefore, it is desirable for movement to be made toward a region other than the coverage regions of the other autonomous robots, outside of the coverage region  21  of the autonomous robot  11 D. 
     It is thereby possible for the autonomous robot  11 D to acquire the other robot information of a new other autonomous robot outside of the coverage region  21  and perform selection processing once again more quickly. 
     It should be noted that the movement direction is not restricted to the case given in the present modified example. This may be combined with an aforementioned case. In other words, the movement direction may be the direction constituting the shortest movement distance with which it is possible to exit to outside of the coverage region with the shortest movement distance from the coverage region  21 , from among regions other than the coverage regions of the other autonomous robots. 
     (Modified Example 3) 
     In the case where the autonomous robot  11 D has not been able to select a support target by performing the selection processing once again after having moved to outside of the coverage region  21  thereof, the autonomous robot  11 D may, in addition, move in a direction having a low density of other autonomous robots that have not been selected due to not requiring support. 
     It is thereby possible for the autonomous robot  11 D to acquire the other robot information of a new other autonomous robot outside of the coverage region  21  and perform selection processing once again more quickly. 
     It should be noted that the autonomous robot  11 D, after having exited to outside of the coverage region  21  thereof, may move without passing through the coverage regions of other autonomous robots that have not been selected as support targets (by moving through regions other than said coverage regions). 
     Furthermore, the way in which the autonomous robot  11 D moves after having exited to outside of the coverage region  21  thereof is not restricted to the aforementioned case, and the autonomous robot  11 D may move with the route being decided or may move in a random manner. In other words, any manner of movement is permissible. 
     (Modified Example 4) 
     It should be noted that, in the case where the autonomous robots  11 D to  19 D are cleaning robots, it is necessary for them to return to their own coverage regions after the cleaning, namely the tasks, has been completed. This is because garbage and dust accumulate as time elapses, and it becomes necessary to perform cleaning once again. 
     In this case, for example, the autonomous robot  11 D may be provided with a movement restriction so as to not move too far away from the coverage region  21  thereof when moving outside of the coverage region to search for another autonomous robot to be a support target. As restrictions, the following are feasible: 1) the movement distance or movement time from exiting to outside of the coverage region and starting to move; 2) the distance from the coverage region boundary (any point is permissible); 3) a prescribed threshold value for the battery state; and 4) the number of other autonomous robots that are newly detected, or the like. 
     It thereby becomes possible for the autonomous robot  11 D to not move too far away from the coverage region  21  thereof even when searching for another autonomous robot to serve as a support target. 
     As described above, a movement control method and a movement control device according to one or more aspects of the present disclosure have been described on the basis of the embodiments; however, the present disclosure is not restricted to these embodiments. Modes in which various modifications conceived by a person skilled in the art have been implemented in the present embodiments, and modes constructed by combining the constituent elements in different embodiments may also be included within the scope of one or more aspects of the present disclosure provided they do not depart from the purpose of the present disclosure. 
     For example, the restriction described in modified example 4 of embodiment 4 may be applied to embodiments 1 to 3. 
     Furthermore, in the aforementioned embodiments, operations and the like have been described with the autonomous robots  11  to  11 D given as examples; however, the present disclosure is not restricted thereto. It is possible for other autonomous robots to also be provided with the same minimum configuration and to perform the same operations. 
     It should be noted that, in the aforementioned embodiments, the constituent elements may be configured by using dedicated hardware, or may be realized by executing a software program suitable for the constituent elements. The constituent elements may be realized by a program execution unit such as a CPU or a processor reading out and executing a software program recorded in a recording medium such as a hard disk or a semiconductor memory. 
     For example, some or all of the functions of an autonomous robot according to embodiments 1 to 4 may typically be realized as an LSI, which is an integrated circuit. These may be implemented separately as single chips, or may be implemented as a single chip in such a way as to include some or all of the functions. Furthermore, the circuit integration is not restricted to an LSI, and the functions may be realized using a dedicated circuit or a general-purpose processor. After an LSI is manufactured, a field-programmable gate array (FPGA) that can be programmed, or a reconfigurable processor with which the connections and settings of circuits cells within the LSI can be reconfigured, may be used. 
     Furthermore, some or all of the functions of an autonomous robot according to embodiments 1 to 4 may be realized by a processor such as a CPU executing a program. 
     Furthermore, the numerals used hereinabove are all examples for explaining the present disclosure in detail, and the present disclosure is not restricted to the numerals given as examples. 
     Furthermore, the sequences in which steps are executed, depicted in the aforementioned  FIGS. 6, 7, 9, 15, and 21 , are all examples for explaining the present disclosure in detail, and may be sequences other than the aforementioned provided the same effect is obtained. Furthermore, some of the steps may be executed at the same time as (in parallel with) other steps. 
     The present disclosure can be used in a movement control method and a movement control device for autonomous mobile robots, and in particular can be used in a movement control method and a movement control device in autonomous robots that have a wireless communication function and are able to perform tasks with respect to regions assigned thereto while moving in an autonomous manner and in a robot system that includes the autonomous robots.