Route calculation method and mobile body system

Abstract

This mobile body system comprises: a plurality of mobile bodies (20); a movement region (30) having a plurality of nodes (31) and a plurality of links (32); and a control device. This route calculation method for the mobile bodies (20) in the mobile body system comprises an assessment step, a setting step, a calculation step, and a cancellation step. In the assessment step, it is assessed whether a mobile body (20) attempting to travel in a first direction (D1) from a first node (31A) can travel in the first direction (D1). In the setting step, when it is assessed that the mobile body (20) cannot travel in the first direction (D1), passage prohibition is set for all of the plurality of mobile bodies (20) on a route traveling in the first direction (D1) from the first node (31A). In the calculation step, the movement routes of the plurality of mobile bodies (20) in the movement region (30) are calculated on the basis of the setting of the passage prohibition. In the cancellation step, the passage prohibition is cancelled when a first time elapses from the setting of the passage prohibition.

Description

Route Calculation Method and Mobile Body System

[0001] The present invention relates to a route calculation method and a mobile body system.

[0002] Conventionally, a mobile body system for moving a plurality of mobile bodies in a predetermined moving area has been known. Patent Document 1 discloses this type of mobile body system.

[0003] The mobile body system of Patent Document 1 includes a plurality of mobile bodies, a plurality of nodes and a plurality of links, a moving area along which the mobile bodies can move, and a control device for moving a plurality of mobile bodies in the moving area. When the control device receives communication of a travel route from one mobile body, it is configured to prohibit other mobile bodies from entering a node that may collide with the one mobile body moving along that travel route, that is, a collision node.

[0004] Japanese Patent No. 301,3360

[0005] By the way, when a mobile body cannot enter a travel route, for example, when a temporary traffic jam has occurred on that travel route, it is conceivable that the cause that prevents entry will be resolved over time. In the conventional mobile body system as described above, the entry of the mobile body into the target travel route is continuously prohibited until the cause that prevents the mobile body from entering is resolved, and the entry prohibition is released when the cause is resolved. However, continuously monitoring whether the cause that prevents the mobile body from entering has been resolved is a burden on the entire system. Depending on the mode of the moving area, performing such control does not necessarily lead to an improvement in the working efficiency of the entire mobile body system (that is, the amount of work per unit time), and on the contrary, there is a possibility that the working efficiency will decrease.

[0006] The present invention has been made in view of the above circumstances, and its object is to improve the working efficiency of the mobile body system. Means for Solving the Problem and Effects

[0007] The problem to be solved by the present invention is as described above. Next, the means for solving this problem and its effects will be described.

[0008] According to a first aspect of the present invention, the following path calculation method is provided. That is, the path calculation method is a method for calculating the path of a mobile body in a mobile body system comprising a plurality of mobile bodies, a mobile area, and a control device. The mobile area has a plurality of nodes and a plurality of links, and the mobile bodies can move along a plurality of paths. The control device calculates the movement paths of the plurality of mobile bodies in the mobile area. The path calculation method comprises a determination step, a setting step, a calculation step, and a release step. In the determination step, it is determined whether a mobile body intending to move from a first node in a first direction can move in the first direction. In the setting step, if it is determined in the determination step that the mobile body cannot move in the first direction, a no-go is set for all of the plurality of mobile bodies on the path from the first node in the first direction. In the calculation step, the movement paths of the plurality of mobile bodies in the mobile area are calculated based on the no-go setting in the setting step. In the release step, the no-go is released when a first time has elapsed since the no-go was set in the setting step.

[0009] As a result, if it is determined that a moving object attempting to proceed from the first node in a first direction (hereinafter also referred to as the first moving object) cannot move in that first direction, a travel ban is set on the path from the first node in the first direction (hereinafter also referred to as the first path) for all multiple moving objects. When a travel ban is set on the first path, all multiple moving objects are unable to pass through the area of ​​the first path corresponding to the travel ban (hereinafter also referred to as the prohibited area). Based on such travel ban settings, the travel paths of the multiple moving objects in the travel area are calculated, so that each of the multiple moving objects moves to its respective destination along a travel path that does not include the prohibited area. Then, when one hour has elapsed since the travel ban was set, the travel ban is lifted, and the travel path calculated thereafter may again include the area that was previously the prohibited area. This series of processes suppresses congestion in the travel area, allows multiple moving objects to move efficiently, and ultimately improves the operational efficiency of the mobile object system.

[0010] In the above-described path calculation method, it is preferable that in the determination step, if the moving body attempting to move from the first node in the first direction remains unable to move in the first direction for a second period of time, it is determined that the moving body cannot move in the first direction.

[0011] As a result, if the first moving object remains unable to move from the first node in the first direction (hereinafter also referred to as the "immobile state") for two consecutive hours, a pass ban will be set on the first path for all moving objects. By using the continuation of the immobile state for two consecutive hours as the determination condition, it is possible to avoid setting pass bans more frequently than necessary, compared to when the occurrence of the immobile state itself is the determination condition.

[0012] In the above-described route calculation method, it is preferable that the first time is shorter than the second time.

[0013] This allows us to relatively shorten the first hour, i.e., the duration of the road closure, thereby reducing the likelihood that the road closure will cause traffic congestion.

[0014] In the above-mentioned path calculation method, it is preferable to proceed as follows: That is, in the movement area, the plurality of nodes are connected in a grid pattern by the plurality of links. If it is determined in the determination step that the moving body cannot move in the first direction, in the setting step, a prohibition on passage is set for all of the plurality of moving bodies at the node located adjacent to the first node in the first direction.

[0015] This effectively suppresses congestion in the travel area compared to, for example, setting a traffic ban on a link connecting to the first node in the first direction.

[0016] In the above-described route calculation method, it is preferable that the first time is determined in accordance with the behavior of the moving object.

[0017] This effectively suppresses congestion in the moving area. Examples of the behavior of the moving object include turning and loading or unloading cargo.

[0018] In the above-mentioned path calculation method, it is preferable to proceed as follows: The moving body can select the link it intends to proceed to from the node by rotating on the node. The first time is determined in accordance with the time required for the moving body to rotate from a state where it is facing one link at the node until it is facing a link located next to the first link in the rotation direction.

[0019] This makes it possible to more effectively suppress congestion in areas of movement.

[0020] A second aspect of the present invention provides a mobile system having the following configuration: The mobile system comprises a plurality of mobile bodies, a mobile area, and a control device. The mobile area has a plurality of nodes and a plurality of links, and the mobile bodies can move along a plurality of paths. The control device calculates the movement paths of the plurality of mobile bodies in the mobile area. The control device determines whether a mobile body attempting to move from a first node in a first direction can move in the first direction. If the control device determines that the mobile body cannot move in the first direction, it sets a no-go for all of the plurality of mobile bodies on the path from the first node in the first direction. Based on the no-go setting, the control device calculates the movement paths of the plurality of mobile bodies in the mobile area. The control device releases the no-go after a first time has elapsed since the no-go was set.

[0021] As a result, if it is determined that the first mobile object cannot move from the first node in the first direction, a travel ban is set on the first route for all multiple mobile objects. When a travel ban is set on the first route, all multiple mobile objects are unable to pass through the prohibited area. Based on such travel ban settings, the travel routes of the multiple mobile objects within the travel area are calculated, so that each of the multiple mobile objects moves to its respective destination along a travel route that does not include the prohibited area. Then, when the travel ban is lifted after one hour has elapsed since the setting of the travel ban, the travel route calculated thereafter may again include the area that was previously a prohibited area. This series of processes suppresses congestion in the travel area, allows multiple mobile objects to move efficiently, and ultimately improves the operational efficiency of the mobile object system.

[0022] A block diagram showing the configuration of a mobile system according to one embodiment of the present invention. A schematic plan view showing an example of a travel path calculated by the route calculation method. A schematic plan view showing another example of a travel path calculated by the route calculation method. A flowchart showing an example of the operation of the mobile body in the route calculation method. A flowchart showing an example of the operation of the mobile body management unit in the route calculation method.

[0023] Next, embodiments of the present invention will be described with reference to the drawings. Figure 1 is a block diagram showing the configuration of a mobile system 10 according to one embodiment of the present invention. Figure 2 is a schematic plan view showing an example of a travel path calculated by the path calculation method. Figure 3 is a schematic plan view showing another example of a travel path calculated by the path calculation method.

[0024] A mobile system 10 according to one embodiment of the present invention is an automated transport system for transporting objects such as a Front Opening Unify Pod (FOUP), which is installed in, for example, a semiconductor manufacturing plant (not shown) equipped with a plurality of processing devices (e.g., plasma processing devices). As shown in Figures 1 to 3, the mobile system 10 comprises a plurality of mobile bodies 20, a mobile area 30, and a mobile body management unit 40. The mobile body management unit 40 is an example of a control device.

[0025] The mobile unit 20 is a transport device that travels within the mobile area 30 and automatically transports goods between processing devices. In this embodiment, the mobile area 30 is defined in a planar manner. The mobile unit 20 can be configured, for example, as a floor-traveling vehicle. The mobile area 30 is defined, for example, by guiding tapes such as magnetic tape attached to the floor, or by barcodes, etc. Guide parts may be provided on at least one of the mobile unit 20 side and the mobile area 30 side so that the wheels 24 of the mobile unit 20 travel along a predetermined path in the mobile area 30. The mobile unit 20 can also be configured as an overhead-traveling vehicle. In this case, the guide parts can be provided, for example, so as to be suspended from the ceiling of a factory.

[0026] The mobile unit 20 is equipped with a multi-jointed robotic arm (not shown) and can perform loading and unloading. For example, an AGV (Automated Guided Vehicle) or an OHT (Overhead Hoist Transfer) can be used as the mobile unit 20.

[0027] The mobile unit 20 performs automatic driving according to a driving plan based on a transport task assigned by the mobile unit management unit 40. Specifically, the mobile unit 20 transports the designated cargo from the designated first designated position P1 to the designated second designated position P2. Here, this automatic driving includes temporary stops to avoid collisions, etc. Note that the first designated position P1 and the second designated position P2 shown in Figures 2 and 3 are examples.

[0028] As shown in Figure 1, the mobile unit 20 comprises a control unit 21, a transmitting / receiving unit 22, and a sensor 23.

[0029] The control unit 21 is configured as a known computer having a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), HDD (Hard Disk Drive), etc. (not shown).

[0030] The control unit 21 controls the loading operation of the mobile body 20 by a loading mechanism such as a robot arm or hoist (not shown), and the automatic driving operation of the mobile body 20 by a driving mechanism (not shown).

[0031] The transmitting / receiving unit 22 is configured to communicate wirelessly with the mobile unit management unit 40. The wireless communication method is arbitrary, but for example, a wireless LAN could be used. The transmitting / receiving unit 22 can transmit the mobile unit 20's own position to the mobile unit management unit 40 via wireless communication, and receive assigned transport tasks and information related to those transport tasks from the mobile unit management unit 40. The transmitting / receiving unit 22 can also transmit information to the mobile unit management unit 40 via wireless communication regarding whether the mobile unit 20 can move in the direction it intends to move in accordance with the transport task. The wireless communication method may also be a communication method using leaky feeder lines and leaky coaxial cables.

[0032] Sensor 23 detects the presence of an obstacle (e.g., another mobile body 20) that may obstruct the movement of the mobile body 20 in the direction it intends to move (or in front of the mobile body 20). In Figures 2 and 3, the orientation of each mobile body 20 is indicated by a triangle. When the sensor 23 detects the presence of such an obstacle, the transmitting / receiving unit 22 transmits via wireless communication to the mobile body management unit 40 that the mobile body 20 cannot move in the direction it intends to move in accordance with the transport task. The type of sensor 23 is not particularly limited, and for example, an ultrasonic sensor can be used.

[0033] In this embodiment, the mobile body 20 can basically only move forward according to its current orientation. The mobile body 20 can change direction by rotating on the node 31, which will be described later, that is, by rotating clockwise or counterclockwise in Figures 2 and 3. This allows the mobile body 20 to change the link 32 (described later) that it intends to proceed through from the node 31. Note that the location where the mobile body 20 performs the rotation is not limited to the node 31. That is, the mobile body 20 can perform the rotation on the link 32 or any other location.

[0034] Within the moving area 30, a predetermined path is defined that the moving body 20 can travel along. This path can be represented by a graph, as shown in Figures 2 and 3, which has multiple (16 in this example) nodes 31 and multiple (24 in this example) links 32. Therefore, the moving area 30 can be considered to have the above-mentioned nodes 31 and links 32. The multiple nodes 31 are connected in a grid pattern by multiple links 32. That is, the multiple nodes 31 are arranged at equal intervals in the vertical and horizontal directions in Figures 2 and 3, and any pair of adjacent nodes 31 in the vertical or horizontal direction are connected by one link 32.

[0035] Links 32 represent linear path elements, and nodes 31 represent bends or branches in the path. In this embodiment, the orientation in which multiple links 32 connect to a single node 31 differs by 90° increments, indicating that multiple path elements connect to a single bend or branch while differing in orientation by 90° increments. Each link 32 is of equal length and extends in either the vertical or horizontal direction. However, the arrangement and dimensions of the multiple nodes 31 and multiple links 32 are not limited to these.

[0036] The mobile area 30 is configured so that the mobile body 20 can move along multiple paths. That is, when the mobile body 20 moves from one node 31 to another node 31, it moves through at least one link 32 connecting the two. At this time, there can be multiple combinations of at least one link 32 connecting the one node 31 and the other node 31 within the mobile area 30. The mobile body 20 can move from the one node 31 to the other node 31 by taking any one of these multiple combinations (for example, a combination that constitutes the shortest path).

[0037] The mobile device management unit 40 is configured as a known computer having a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), HDD (Hard Disk Drive), etc., for example, similar to the control unit 21 described above.

[0038] The mobile unit management unit 40 can communicate with a higher-level device (not shown) located in the factory or another location. The mobile unit management unit 40 assigns each of the multiple transport tasks given by the higher-level device to one of the multiple mobile units 20 under its management, and determines a travel plan for the mobile unit 20 corresponding to the assigned transport task. In other words, the mobile unit management unit 40 calculates the travel paths of the multiple mobile units 20 in the travel area 30. Known methods such as Dijkstra's algorithm or the A* algorithm can be used for this calculation. In Figures 2 and 3, an example of the shortest travel path from the first designated position P1 to the second designated position P2, calculated by the mobile unit management unit 40, is shown by a dashed arrow.

[0039] Here, the mobile object management unit 40 modifies the movement path from the first designated position P1 to the second designated position P2 as necessary, using the path calculation method according to this embodiment. Specifically, the mobile object management unit 40 performs a determination step, a setting step, a calculation step, and a release step as necessary. The mobile object management unit 40 includes a determination unit 41 that performs the determination step, a prohibition setting unit 42 that performs the setting step, a path calculation unit 43 that performs the calculation step, and a prohibition release unit 44 that performs the release step.

[0040] In the determination step, the mobile body management unit 40 (more specifically, the determination unit 41 of the mobile body management unit 40) determines whether a mobile body 20 attempting to move in the first direction D1 (upward in this example, in Figures 2 and 3) from the first node 31A corresponding to the first designated position P1 is able to move in the first direction D1. In the determination step, the mobile body management unit 40 determines that a mobile body 20 is unable to move in the first direction D1 if the state of being unable to move in the first direction D1 continues for a second period of time. The mobile body management unit 40 makes this determination based on information sent from each mobile body 20 regarding whether or not it is able to move in the first direction D1. The second period may be, for example, 20 seconds or more and 40 seconds or less, and is preferably 30 seconds. Examples of factors preventing the mobile body 20 from moving from the first node 31A to the first direction D1 include the presence of another mobile body 20 on the path (first path) from the first node 31A to the first direction D1, and the prohibition of passage on the first path by the mobile body management unit 40 or a higher-level device.

[0041] In the setting step, if the mobile body management unit 40 (more specifically, the prohibition setting unit 42 of the mobile body management unit 40) determines in the determination step that the mobile body 20 cannot proceed in the first direction D1, it sets a prohibition on passage for all of the multiple mobile bodies 20 on the path from the first node 31A to the first direction D1. Specifically, in the setting step of this embodiment, in such a case, the mobile body management unit 40 sets a prohibition on passage for all of the multiple mobile bodies 20 at the node 31 located next to the first direction D1 relative to the first node 31A (in the example of Figures 2 and 3, the node 31 located above the first node 31A). Note that the target for setting the prohibition on passage is not limited to the node 31, but may also be, for example, a link 32 included in the path from the first node 31A to the first direction D1, or both the node 31 and the link 32 included in the path. Furthermore, in the setting step, if the mobile body management unit 40 determines in the determination step that the mobile body 20 can proceed in the first direction D1, it does not set a prohibition on the path from the first node 31A to the first direction D1.

[0042] In Figures 2 and 3, the locations where passage is prohibited are indicated by the symbols BL1 to BL4. In Figure 2, passage prohibition BL1 is set at only one node 31, which means passage prohibition set in the setting step described above. Since the set passage prohibition applies to all moving bodies 20, in the example of Figure 2, not only the moving body 20 located at the first node 31A, but also the other moving body 20 cannot pass through the node 31 where passage prohibition BL1 is set. On the other hand, in Figure 3, in addition to passage prohibition BL1 described above, three passage prohibition BL2 to BL4 are set. The former passage prohibition BL1 means passage prohibition set in the setting step corresponding to the moving body 20 located at the first node 31A, while the latter passage prohibition BL2 to BL4 mean passage prohibition set in a different process (for example, a setting step corresponding to another moving body 20 not shown).

[0043] In the calculation step, the mobile body management unit 40 (more specifically, the route calculation unit 43 of the mobile body management unit 40) calculates the movement paths of the multiple mobile bodies 20 in the movement area 30 based on the access restriction settings in the setting step. That is, in the calculation step, the mobile body management unit 40 calculates a movement path for moving from the first node 31A to the second node 31B corresponding to the second designated position P2, bypassing at least one node 31 where access is restricted, for only the mobile bodies 20 whose own movement path is restricted (or for all of the multiple mobile bodies 20). The calculation step is performed after the execution of the setting step and before the first time has elapsed (for example, 1 second after the execution of the setting step). In Figures 2 and 3, the movement path calculated for a mobile body 20 located at the first node 31A, for moving from the first node 31A to the second node 31B without passing through the node 31 where access restriction BL1 is set, is shown by a solid arrow. Each moving body 20 moves within the movement area 30 along the calculated movement path.

[0044] In the release step, the mobile body management unit 40 (more specifically, the prohibition release unit 44 of the mobile body management unit 40) releases the traffic prohibition when the first time has elapsed since the setting of the traffic prohibition in the setting step. That is, without monitoring (confirming) whether the cause for which it was determined in the determination step that the mobile body 20 could not proceed in the first direction D1 has been resolved, the traffic prohibition is uniformly released when a predetermined time has elapsed since the setting of the traffic prohibition. The first time is shorter than the above-described second time. The first time may be, for example, 8 seconds or more and 12 seconds or less, and is preferably 10 seconds. When a plurality of traffic prohibitions are set as shown in FIG. 3, the release of the traffic prohibition is performed independently based on the timing at which each traffic prohibition was set. Therefore, when a plurality of traffic prohibitions are set at different timings from each other, the timings at which each traffic prohibition is released are also different.

[0045] The first time is determined corresponding to the behavior of the mobile body 20. More specifically, the first time is the time required for the mobile body 20 to turn from the state of facing one link 32 at the node 31 until it faces the link 32 adjacent to the one link 32 in the turning direction (that is, the clockwise direction or the counterclockwise direction in FIGS. 2 and 3) (hereinafter, also referred to as the turning time). For example, the first time may be 0.8 times or more and 1.2 times or less of the turning time, and is preferably 1.0 times the turning time. The turning time in the present embodiment is the time required for the mobile body 20 to turn 90° in a plan view, and is, for example, 10 seconds.

[0046] Next, referring to FIGS. 4 and 5, an example of each operation of the mobile body 20 and the mobile body management unit 40 when executing the route calculation method of the present embodiment will be described. FIG. 4 is a flowchart showing an example of the operation of the mobile body 20 in the route calculation method. FIG. 5 is a flowchart showing an example of the operation of the mobile body management unit 40 in the route calculation method.

[0047] First, an example of the operation of the mobile body 20 will be described with reference to FIG. 4. In step S101, the mobile body 20 determines whether it has received information about the destination and the route from the current location to the destination from the mobile body management unit 40. If the information has not been received (in the case of "No" in S101), this determination is repeated. On the other hand, if the information has been received (in the case of "Yes" in S101), the process proceeds to step S102.

[0048] In step S102, the mobile body 20 performs automatic driving according to the route information received from the mobile body management unit 40. During the driving process, the mobile body 20 continuously communicates with the mobile body management unit 40 and notifies the mobile body management unit 40 of its own position substantially in real time. The mobile body 20 performs the automatic driving while detecting whether there is an obstacle (for example, another mobile body 20) in front of it by the sensor 23. Subsequently, the process proceeds to step S103.

[0049] In step S103, the mobile body 20 determines whether it has received information about a new route from the mobile body management unit 40. This information about the new route is transmitted from the mobile body management unit 40 due to factors not directly related to the driving situation of the mobile body 20 (for example, a traffic prohibition setting related to another mobile body 20). If the information has been received (in the case of "Yes" in S103), the process returns to step S102 and performs automatic driving according to the information about the new route. On the other hand, if the information has not been received (in the case of "No" in S103), the process proceeds to step S104.

[0050] In step S104, the mobile body 20 determines whether an obstacle has been detected by the sensor 23. If an obstacle has been detected (in the case of "Yes" in S104), the process proceeds to step S105. On the other hand, if no obstacle has been detected (in the case of "No" in S104), the process proceeds to step S107.

[0051] When an obstacle is detected in step S104, the mobile body 20 usually stops at an appropriate position where it does not interfere with the obstacle. It is preferable that the mobile body 20 stops at a position corresponding to the node 31 corresponding to the branch point of the route, because it can easily cope with future route changes.

[0052] In step S105, the mobile body 20 sends a pass-not-go signal (i.e., a signal indicating that the mobile body 20 is unable to move forward along the path) to the mobile body management unit 40 via the transmitting / receiving unit 22. The process then proceeds to step S106.

[0053] In step S106, the mobile unit 20 determines whether or not it has received information about a new route from the mobile unit management unit 40. This information about a new route is transmitted from the mobile unit management unit 40 because the mobile unit 20 has sent a no-pass signal for two hours (30 seconds in this example). If the mobile unit 20 has not received this information (if the answer in S106 is "No"), the process returns to step S104. On the other hand, if the mobile unit has received this information (if the answer in S106 is "Yes"), the process returns to step S102 and the automatic driving process resumes according to the new route.

[0054] In step S107, the mobile unit 20 determines whether or not it has arrived at its destination. If the mobile unit 20 has arrived at its destination (if the answer is "Yes" in S107), the mobile unit 20 returns to step S101 and waits for instructions from the mobile unit management unit 40. On the other hand, if the mobile unit 20 has not arrived at its destination (if the answer is "No" in S107), the mobile unit 20 returns to step S102 and continues to drive automatically.

[0055] Next, an example of the operation of the mobile unit management unit 40 will be explained with reference to Figure 5.

[0056] The mobile object management unit 40 has pre-stored information on the nodes 31 and links 32 corresponding to the graph in Figure 2. The mobile object management unit 40 can also store information on whether or not a no-passing restriction is set for each node 31, and the timing of when the no-passing restriction was set. In step S201, the mobile object management unit 40, as an initial setting, removes the no-passing restriction for all nodes 31. Then, proceed to step S202.

[0057] In step S202, the mobile unit management unit 40 determines whether a movement request (or a signal related to a transport task from the said higher-level device) has been received. This movement request includes destination information. If a movement request is received (if "Yes" is answered in S202), the process proceeds to step S203. If there is no movement request (if "No" is answered in S202), steps S203 and S204, described below, are skipped.

[0058] In step S203, the mobile unit 40 lifts the traffic restriction that has been in effect for more than one hour (10 seconds in this example) since the set timing. The process then proceeds to step S204.

[0059] In step S204, the mobile unit 40 selects a mobile unit 20 suitable for the movement request in step S202, calculates a route to the destination for the selected mobile unit 20, and transmits information about the destination and the route to that destination (i.e., the calculated route). If a no-go zone is set in the movement area 30, all no-go zones are taken into consideration when calculating the route. The route instructed to the mobile unit 20 is stored in the mobile unit 40. The process then proceeds to step S205.

[0060] In step S205, the mobile unit management unit 40 determines whether any of the multiple mobile units 20 that are moving have continued to detect an obstacle for a second period of time (30 seconds in this example). This determination is made based on the information of the impassable signal sent from each mobile unit 20. If none of the mobile units 20 have detected an obstacle for a second period of time (if the answer in S205 is "No"), the process returns to step S202. On the other hand, if any of the mobile units 20 have detected an obstacle for a second period of time (if the answer in S205 is "Yes"), the process proceeds to step S206.

[0061] In step S206, the mobile object management unit 40 sets a no-passing zone at node 31 corresponding to the location where an obstacle was detected over the second hour. The process then proceeds to step S207.

[0062] In step S207, the mobile unit 40 lifts the traffic restriction that has been in effect for at least one hour (10 seconds in this example) since the set timing. The process then proceeds to step S208.

[0063] In step S208, the mobile object management unit 40 calculates a new route for the mobile object 20 from among the multiple mobile objects 20 for which a no-passing zone was added to its route in step S206. When calculating the route, all no-passing zones set in the mobile area 30 and the current position of the mobile object 20 are taken into consideration. The mobile object management unit 40 transmits the calculated new route information to the mobile object 20. Then, the process returns to step S202.

[0064] Through the above process, when a mobile object 20 detects that it cannot pass, a no-passing zone is set at the location where it became impassable, the route of that mobile object 20 is recalculated, and the routes of other mobile objects 20 are also recalculated as necessary. In this embodiment, since the no-passing zone is set precisely at one node 31, the range of route selection around the no-passing zone is not excessively narrowed. Therefore, even when there are many mobile objects 20 in the mobile area 30, the routes of mobile objects 20 that bypass the no-passing zone are less likely to overlap, and thus congestion can be expected to be alleviated.

[0065] When many mobile bodies 20 travel within the mobile area 30, a decrease in transport efficiency due to congestion becomes a problem. One method to avoid congestion is to use a method in which, when calculating the route for each mobile body 20, a random cost determined by predicting congestion is set at at least one of the nodes 31 and links 32. While this method can achieve distribution of routes for multiple mobile bodies 20, it is difficult to ensure prediction accuracy, and there is a concern that transport efficiency may actually decrease. In this embodiment, as long as no road closures are set on the graph, the shortest route can be calculated and instructed for each of the multiple mobile bodies 20. On the other hand, if it is actually detected that a mobile body 20 cannot pass, a time-limited road closure is set on the graph, and for mobile bodies 20 affected by the road closure, a detour route that avoids the road closure is required. Therefore, since inefficient routes are not set in consideration of uncertain future congestion, transport efficiency can be increased.

[0066] As described above, the path calculation method of this embodiment is a path calculation method for a mobile body 20 in a mobile body system 10 comprising a plurality of mobile bodies 20, a mobile area 30, and a mobile body management unit 40. The mobile area 30 has a plurality of nodes 31 and a plurality of links 32, and the mobile bodies 20 can move along a plurality of paths. The mobile body management unit 40 calculates the movement paths of the plurality of mobile bodies 20 in the mobile area 30. The path calculation method comprises a determination step, a setting step, a calculation step, and a release step. In the determination step, it is determined whether a mobile body 20 that intends to proceed from the first node 31A in the first direction D1 can proceed in the first direction D1. In the setting step, if it is determined in the determination step that the mobile body 20 cannot proceed in the first direction D1, a prohibition on passage is set for all of the plurality of mobile bodies 20 on the path from the first node 31A to the first direction D1. In the calculation step, the movement paths of the multiple moving objects 20 in the movement area 30 are calculated based on the no-passing setting in the setting step. In the release step, the no-passing setting is released when 1 hour has elapsed since the no-passing setting in the setting step.

[0067] As a result, if it is determined that a moving body 20 (first moving body) attempting to proceed from the first node 31A in the first direction D1 cannot move in the first direction D1, a travel ban is set for all of the multiple moving bodies 20 on the path (first path) from the first node 31A to the first direction D1. When a travel ban is set on the first path, all of the multiple moving bodies 20 are unable to pass through the area of ​​the first path corresponding to the travel ban (prohibited area). Based on such travel ban settings, the travel paths of the multiple moving bodies 20 in the travel area 30 are calculated, so that each of the multiple moving bodies 20 moves to its respective destination along a travel path that does not include the prohibited area. Then, when the travel ban is lifted after 1 hour has elapsed since the setting of the travel ban, the area that was previously the prohibited area may again be included in the travel path calculated thereafter. This series of processes suppresses congestion in the travel area 30, allows multiple moving bodies 20 to move efficiently, and ultimately improves the work efficiency of the moving body system 10.

[0068] Furthermore, in the path calculation method of this embodiment, in the determination step, if the moving body 20 that is attempting to move from the first node 31A in the first direction D1 is unable to move in the first direction D1 for a period of time, it is determined that the moving body 20 cannot move in the first direction D1.

[0069] As a result, if the first moving object remains unable to move from the first node 31A in the first direction D1 (immobile state) for two consecutive hours, a prohibition on passage is set for all of the multiple moving objects 20 on the first path. By using the continuation of the immobile state for two consecutive hours as the determination condition, it is possible to avoid setting the prohibition on passage more frequently than necessary, compared to when the occurrence of the immobile state itself is the determination condition.

[0070] Furthermore, in the route calculation method of this embodiment, the first time is shorter than the second time.

[0071] This allows us to relatively shorten the first hour, i.e., the duration of the road closure, thereby reducing the likelihood that the road closure will cause traffic congestion.

[0072] Furthermore, in the path calculation method of this embodiment, multiple nodes 31 are connected in a grid pattern by multiple links 32 in the movement area 30. If it is determined in the determination step that the moving body 20 cannot move in the first direction D1, in the setting step, a prohibition on passage is set for all of the multiple moving bodies 20 at the node 31 located adjacent to the first direction D1 with respect to the first node 31A.

[0073] This effectively suppresses congestion in the movement area 30 compared to, for example, setting a no-go rule on the link 32 connected to the first direction D1 for the first node 31A.

[0074] Furthermore, in the path calculation method of this embodiment, the first time is determined in accordance with the behavior of the moving object 20.

[0075] This effectively suppresses congestion in the moving area 30. Examples of the behavior of the moving body 20 include turning and loading or unloading cargo by the moving body 20.

[0076] Furthermore, in this embodiment, the path calculation method allows the moving body 20 to select the link 32 to proceed from the node 31 by rotating on the node 31. The first time is determined in accordance with the time required for the moving body 20 to rotate from a state where it is facing one link 32 at the node 31 to a state where it is facing a link 32 located next to the first link 32 in the rotational direction.

[0077] This makes it possible to more effectively suppress the occurrence of congestion in the movement area 30.

[0078] Furthermore, the mobile system 10 of this embodiment includes a plurality of mobile bodies 20, a mobile area 30, and a mobile body management unit 40. The mobile area 30 has a plurality of nodes 31 and a plurality of links 32, and the mobile bodies 20 can move along a plurality of paths. The mobile body management unit 40 calculates the movement paths of the plurality of mobile bodies 20 in the mobile area 30. The mobile body management unit 40 determines whether a mobile body 20 that intends to proceed from the first node 31A in a first direction D1 can proceed in the first direction D1. If the mobile body management unit 40 determines that a mobile body 20 cannot proceed in the first direction D1, it sets a no-go for all of the plurality of mobile bodies 20 on the path from the first node 31A to the first direction D1. Based on the no-go setting, the mobile body management unit 40 calculates the movement paths of the plurality of mobile bodies 20 in the mobile area 30. The mobile body management unit 40 releases the no-go when a first time has elapsed since the no-go setting was set.

[0079] As a result, if it is determined that the first mobile object cannot move from the first node 31A in the first direction D1, a travel ban is set on the first route for all of the multiple mobile objects 20. When a travel ban is set on the first route, all of the multiple mobile objects 20 are unable to pass through the prohibited area. Based on such travel ban settings, the travel routes of the multiple mobile objects 20 in the travel area 30 are calculated, so that each of the multiple mobile objects 20 moves to its respective destination along a travel route that does not include the prohibited area. Then, when the travel ban is lifted after 1 hour has elapsed since the setting of the travel ban, the travel route calculated thereafter may again include the area that was previously the prohibited area. This series of processes suppresses congestion in the travel area 30, allows multiple mobile objects 20 to move efficiently, and ultimately improves the work efficiency of the mobile object system 10.

[0080] Preferred embodiments of the present invention have been described above, but the above configuration can be modified as follows, for example. Modifications may be made individually, or multiple modifications may be made in any combination.

[0081] The lengths of the first and second hours are not limited to those exemplified above. Furthermore, the first hour may be longer than the second hour, or the same length as the second hour.

[0082] In step S205 of Figure 5, the mobile body management unit 40 may determine that the mobile body 20 cannot proceed in the first direction D1 simply by receiving the no-pass signal from the mobile body 20, instead of continuously receiving the no-pass signal from the mobile body 20 for a second period of time.

[0083] Multiple nodes 31 do not necessarily have to be connected in a grid pattern by multiple links 32 in the moving area 30. For example, multiple nodes 31 may be irregularly arranged in at least a part of the moving area 30. Also, even if multiple nodes 31 are regularly arranged, at least a part of them do not necessarily have to be regularly connected by multiple links 32.

[0084] The first time interval may be determined in accordance with the behavior of the moving body 20 that is different from turning. For example, the first time interval can be determined based on the time it takes for a stationary moving body 20 to accelerate and reach a predetermined speed, or the time it takes for a moving body 20 traveling at a predetermined speed to come to a stop.

[0085] The first time interval does not necessarily have to be determined in accordance with the behavior of the mobile body 20. For example, the first time interval may be determined experimentally, independently of the behavior of the mobile body 20, so as to maximize the work efficiency of the mobile system 10.

[0086] 10 Mobile system 20 Mobile body 30 Mobile area 31 Node 31A First node 32 Link 40 Mobile body management unit (control device) D1 First direction

Claims

1. A method for calculating the path of a mobile body in a mobile body system comprising: a plurality of mobile bodies; a mobile area having a plurality of nodes and a plurality of links, wherein the mobile bodies can move along a plurality of paths; and a control device for calculating the movement paths of the plurality of mobile bodies in the mobile area, the method comprising: a determination step of determining whether a mobile body intending to move from a first node in a first direction can move in the first direction; a setting step of setting a no-passing rule for all of the plurality of mobile bodies on the path from the first node in the first direction if the determination step determines that the mobile body cannot move in the first direction; a calculation step of calculating the movement paths of the plurality of mobile bodies in the mobile area based on the no-passing rule setting in the setting step; and a release step of releasing the no-passing rule when a first time has elapsed since the no-passing rule was set in the setting step.

2. A path calculation method according to claim 1, characterized in that, in the determination step, if the moving body attempting to move from the first node in the first direction is unable to move in the first direction for a second period of time, it is determined that the moving body is unable to move in the first direction.

3. A route calculation method according to claim 2, characterized in that the first time is shorter than the second time.

4. A path calculation method according to any one of claims 1 to 3, wherein in the moving area, the plurality of nodes are connected in a grid pattern by the plurality of links, and if it is determined in the determination step that the moving body cannot move in the first direction, the setting step is characterized in that a prohibition on passage is set for all of the plurality of moving bodies at the node located adjacent to the first node in the first direction.

5. A path calculation method according to claim 4, characterized in that the first time is determined in accordance with the behavior of the moving object.

6. A path calculation method according to claim 5, wherein the moving body can select the link to proceed from the node by rotating on the node, and the first time is determined in correspondence with the time required for the moving body to rotate from a state in which it is facing one link at the node to a state in which it is facing a link adjacent to the one link in the rotation direction.

7. A mobile body system comprising: a plurality of mobile bodies; a mobile area having a plurality of nodes and a plurality of links, wherein the mobile bodies can move along a plurality of paths; and a control device that calculates the movement paths of the plurality of mobile bodies within the mobile area, wherein the control device determines whether a mobile body attempting to move from a first node in a first direction can move in the first direction; if it determines that the mobile body cannot move in the first direction, it sets a no-go for all of the plurality of mobile bodies on the path from the first node in the first direction; calculates the movement paths of the plurality of mobile bodies within the mobile area based on the setting of the no-go; and releases the no-go when a first time has elapsed since the setting of the no-go.

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