Moving object group control device, moving object group control system and moving object group control method

Abstract

To provide a moving object group control device, a moving object group control system and a moving object group control method, capable of improving the overall efficiency of a moving object.SOLUTION: A moving route creating unit 615: creates tentative moving routes to the destinations of a plurality of moving objects 101 by applying a predetermined pre-movement rule to the entire area of a moving space 200 for the plurality of moving objects 101; evaluates, based on predetermined evaluation items, a movement prediction result when the plurality of moving objects 101 move along the tentative moving routes; sets, based on the evaluation result of the movement prediction result, a specific area 1201 as an area to which a special movement rule different from the pre-movement rule is applied in the moving space 200; and creates moving routes to the destinations of the plurality of moving objects 101 by applying the special movement rule to the special area 1201 and the pre-movement rule to an area in the moving space 200 other than the special area 1201.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a mobile body group control device, a mobile body group control system, and a mobile body group control method for controlling a plurality of mobile bodies.

Background Art

[0002] With the labor shortage due to the declining birthrate and aging population and the expansion of the e-commerce market, the reduction of personnel and the improvement of work efficiency in logistics warehouses and factories have become issues. To solve these issues, the introduction of a mobile body group control system that efficiently operates a plurality of mobile bodies such as automated guided vehicles (AGVs) has been promoted.

[0003] Conventional mobile body group control systems generally divide space into square grids in view of the calculation cost required for controlling all mobile bodies and collision avoidance between mobile bodies, and mobile bodies move only by going straight to the upper, lower, left, and right grids and turning on the spot. At this time, the positions of all mobile bodies are managed using a single control server (host computer), and a centralized route planning function that sequentially calculates the routes to the destinations of all mobile bodies forms the basic configuration.

[0004] The route planning function is required to optimize the overall efficiency while avoiding collisions and interferences between mobile bodies. As a specific example, in the mobile body control device of Patent Document 1, the calculation of route planning is regarded as a mixed-integer programming problem that takes the movement route and movement process as inputs and aims to minimize a predetermined evaluation value while satisfying the constraint conditions. By adding a collision prohibition condition to the constraint conditions and minimizing the evaluation value, it is possible to calculate a conveyance schedule that minimizes the movement routes of all mobile bodies while avoiding collisions between mobile bodies.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In Patent Document 1, the same rules (constraint conditions) are set throughout the moving space. More specifically, in any route of the moving space, when there is no scheduled intrusion of other moving bodies, the route is made drivable. In this case, when one moving body occupies the route, other moving bodies may be forced to make excessive detours or waits around the route. Therefore, there is room for improvement in the moving body control device of Patent Document 1 from the viewpoint of optimizing the overall efficiency.

[0007] The present invention has been made in view of the above problems, and an object thereof is to provide a moving body group control device, a moving body group control system, and a moving body group control method capable of improving the overall efficiency of moving bodies.

Means for Solving the Problems

[0008] To achieve the above object, the present invention provides a moving body group control device for controlling a plurality of moving bodies, comprising a destination determination unit for determining destinations of the plurality of moving bodies, a moving route creation unit for creating moving routes of the plurality of moving bodies to the destinations, and a communication unit for transmitting the moving routes to the plurality of moving bodies. The moving route creation unit applies a predetermined pre-movement rule to the entire area of the moving space of the plurality of moving bodies, creates tentative moving routes of the plurality of moving bodies to the destinations, evaluates a moving prediction result when the plurality of moving bodies move along the tentative moving routes based on a predetermined evaluation item, sets, based on the evaluation result of the moving prediction result, an area where a special moving rule different from the pre-movement rule is applied in the moving space as a special area, applies the special moving rule to the special area and applies the pre-movement rule to an area other than the special area in the moving space, and then creates the moving routes.

[0009] Further, the present invention provides a moving body group control system for controlling a plurality of moving bodies, comprising a plurality of moving bodies and the moving body group control device.

[0010] Further, the present invention provides a mobile body group control method for controlling a plurality of mobile bodies, comprising: a first step of determining destinations of the plurality of mobile bodies; a second step of creating tentative movement routes of the plurality of mobile bodies to the destinations after applying predetermined pre-movement rules to all regions of the movement space of the plurality of mobile bodies; a third step of evaluating movement prediction results when the plurality of mobile bodies move along the tentative movement routes based on predetermined evaluation items; a fourth step of setting, based on the evaluation results of the third step, a region where a special movement rule different from the pre-movement rule is applied in the movement space as a special region; and a fifth step of creating movement routes of the plurality of mobile bodies to the destinations after applying the special movement rule to the special region and applying the pre-movement rule to regions other than the special region in the movement space.

Advantages of the Invention

[0011] According to the present invention, since the density of mobile bodies in the movement space is equalized, it is possible to improve the overall efficiency of the mobile bodies.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

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Figure 12

Figure 13

Mode for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 to 13. In this embodiment, as an example, the description will be made for the inter-process conveyance in a warehouse and a factory.

[0014] <Operation Environment 100> FIG. 1 is a diagram showing an example of an operation environment 100 of a conveyance system in a warehouse and a factory. In the operation environment 100, mobile bodies 101 that perform conveyance work are used. Each mobile body 101 is controlled via wireless communication by a mobile body group control device 601. The mobile body group control device 601 includes a control server 601a, an input device 601b such as a keyboard and a mouse, and a display 601c. The input device 601b is a device for inputting information on an order (task) required for the entire conveyance system to the control server 601a. The display 601c is a device for displaying the operation status (scheduled path to pass, task execution status, etc.) of each mobile body 101, which is the calculation result of the control server 601a.

[0015] In the operating environment 100, an operator 105 at station 104 transfers an article 103 conveyed by conveyor 102 from another area to the mobile unit 101. The mobile unit 101 loaded with the article 103 moves to another station 106, and it is assumed that another operator 108 at station 106 loads the conveyed article 103 and places it on conveyor 109. The mobile unit 101 repeatedly travels between station 104 adjacent to conveyor 102 and station 106 for loading. When charging is required or there are no executable tasks, it operates to move towards the dock 107 installed alongside.

[0016] <Moving Space 200> Figure 2 is a diagram showing the moving space 200 of the mobile unit 101. The entire moving space 200 is divided by a quadrangular (square) grid 201. The center of the grid 201 is a node 202, and the information connecting between the nodes 202 is a link 203. A route plan is performed using the graph structure 204 composed of the nodes 202 and the links 203.

[0017] <Blocking Control> In general group control, in order to avoid collisions and interferences between mobile units, for the route to the aforementioned destination, it has a function of occupying a specific section, and the occupied section does not permit the intrusion of other mobile units. This is called blocking control or exclusive control, and it is a safety function that operates independently of the route plan. Hereinafter, in this embodiment, it is uniformly referred to as blocking control. Figure 3 is a conceptual diagram of blocking control. In Figure 3, there are two mobile units 301 and 302, and the routes to their respective destinations 303 and 304 partially overlap. Since the mobile unit 301 blocks an area 305 of four grids, the mobile unit 302 is in a situation where it is only permitted to travel in an area 306 of three grids ahead. The number of grids (length) of the above-mentioned blocked section (occupied section) greatly affects the productivity of the entire system. There is a trade-off relationship between the length of the blocked section from the viewpoints of the productivity and computational load of the entire system, and it is necessary to appropriately set according to the performance of the mobile unit group control device 601 and the in-vehicle controller 501 and the number of mobile units.

[0018] <Graph structure> In this embodiment, in order to more significantly demonstrate the effects of the present invention, instead of using a graph structure 204 (shown in FIG. 2) that enables movement in only four directions: up, down, left, and right, as shown in FIG. 4(A), a graph structure 401 that enables movement in a total of eight directions, including four diagonal directions at 45 degrees in addition to the four directions of up, down, left, and right, is used. Here, FIG. 4(B) shows an example of a movement path that utilizes only up, down, left, and right movement + in-place turning, and FIG. 4(C) shows an example of a movement path that also utilizes diagonal movement. As an advantage of diagonal movement, when the destination 403 is in the diagonal direction of the moving body 402, compared with the case of using only up, down, left, and right movement + in-place turning, the travel distance is shorter, and since a single direction change only requires a 45-degree turn, depending on the driving form and control method of the moving body, it is possible to change the moving direction without the need to decelerate and stop one by one.

[0019] On the other hand, if diagonal driving is allowed, depending on the shape of the moving body 101 and the size of the grid, the occupancy rate of the grid due to occlusion control may increase, which may become a factor hindering the progress of other moving bodies 101. As an example, as shown in the comparison between the occupied area 404 in FIG. 4(B) and the occupied area 405 in FIG. 4(C), when moving one grid diagonally forward, a total of four grids of area are occupied, so the space utilization efficiency is not good. More specifically, when diagonal driving is utilized, focusing only on a specific moving body 101 can reach the destination quickly, but for other moving bodies 101, since the already occupied area becomes large (widespread), excessive detours and waiting may occur, which may lead to a deterioration of the overall efficiency.

[0020] The above-described situation depends on the congestion status of the moving bodies 101 within a specific area, and is likely to occur because the grid occupancy increases as the moving bodies 101 become denser. Therefore, in this embodiment, a function is proposed to aggregate the planned travel routes of each moving body, predict in advance the areas where the moving bodies will become congested using the results, and separate, based on any evaluation item, the areas where diagonal movement will continue to be utilized from the areas that are limited to movement in only the left, right, up, and down directions, for example. Compared with the prior art, the novel element is that the movement rules for each area are sequentially changed according to the congestion status of the moving bodies 101. Hereinafter, the specific system configuration and details of the processing for realizing the above-described novel element will be described.

[0021] <Moving body 101> FIG. 5(A) is a conceptual diagram of the moving body 101. The moving body 101 in the present embodiment is a differential two-wheel type, but may be a moving body with other driving forms such as an omnidirectional wheel type or a mecanum wheel type. Here, x is the x coordinate value of the moving body 101, y is the y coordinate value of the moving body 101, and θ is the orientation (direction) of the moving body 101. The self-position calculation described later means acquiring the current values of (x, y, θ).

[0022] <Functional blocks included in the moving body 101 and the in-vehicle controller 501> A functional block diagram for explaining the control operation of the moving body 101 is shown in FIG. 5(B). An in-vehicle controller 501 that performs control calculations is mounted on the moving body 101. The in-vehicle controller 501 includes a target route management unit 502, an in-vehicle sensor 503, a travel map management unit 504, a control command generation unit 505, a self-position calculation unit 506, and a communication unit 509 that communicates with the moving body group control device 601. The moving body 101 also includes a drive unit 507 including drive wheels and an encoder 508 that acquires the rotation amount of the drive wheels. Hereinafter, an outline of each function will be described.

[0023] The target route management unit 502 receives the target route planned by the moving body group control device 601 via the communication unit 509. The target route is a set of the nodes and links, and receives information sequentially updated from the moving body group control device 601.

[0024] The in-vehicle sensor 503 corresponds to an external sensor mounted on the moving body 101. In this embodiment, as an example, it is equipped with LiDAR (Light Detection And Ranging). LiDAR is a sensor that measures the distance to an object existing in the irradiation range while changing the irradiation angle of laser light. Regarding the mobile body group control technology including AGV, it was common to install AR (Augmented Reality) tags and RFID (Radio Frequency Identification) on the driving road surface and use a dedicated sensor to read these tags to obtain the driving position and orientation of the mobile body. On the other hand, in recent years, position estimation technologies that utilize active sensors such as LiDAR and cameras have become possible at low cost and with high accuracy. As a result, it has become possible to accurately drive the moving body 101 even with a complex graph structure having the above-described 45-degree diagonal links.

[0025] The driving map management unit 504 manages a driving map (an image map different from FIG. 2) indicating obstacle information in the operation environment 100. The map takes as input the measurement data (point cloud set by LiDAR) during driving obtained from the in-vehicle sensor 503 (LiDAR) and the moving distance information of the moving body obtained from an encoder 508 described later, and is created in advance before the start of operation using SLAM (Simultaneous Localization and Mapping). Since the creation of a grid map by SLAM is a known technique, the description thereof is omitted.

[0026] The self-position calculation unit 506 combines the measurement results obtained from the in-vehicle sensor 503 and the encoder 508, and calculates the self-position (coordinate values x, y) and the orientation θ of the moving body 101. Specifically, map matching technology is used. Map matching is a technology that takes as input the measurement data acquired by the in-vehicle sensor 503 and the driving map, and utilizes the similarity between both the point cloud set and the driving map to estimate the position of the moving body on the driving map. For example, there is the Adaptive Montecarlo Localization method that utilizes a particle filter. Since the self-position estimation technology by map matching is also a known technique, the detailed description thereof is omitted.

[0027] The control command generation unit 505 performs calculations related to the travel control of the moving body. Here, taking the target path and the self-position as inputs, it performs calculations to determine a control command for following the target path, more specifically, the speed v and the angular velocity ω. For example, a process of setting the nearest node to the vehicle's own position that constitutes the target path as the target node and sequentially calculating the speed v and the angular velocity ω such that the target node is reached can be considered. Specifically, methods such as the forward-looking model (Pure pursuit method) can be considered. Since this method is also a known technique, a detailed description is omitted.

[0028] The drive unit 507 drives the drive wheels according to the command value input from the control command generation unit 505. The encoder 508 estimates the moving distance and the current speed of the moving body 101 from the rotation amount of the drive wheels and transmits the estimated values to the self-position calculation unit 506.

[0029] The above is an overview of the functions provided by the moving body 101 and the in-vehicle controller 501. Subsequently, an overall view of the moving body group control system and an overview of the functions of the moving body group control device 601, which is the main point of this embodiment, will be described.

[0030] <Moving Body Group Control System> FIG. 6 is a functional block diagram of the mobile body group control system 600. The mobile body group control system 600 in the present embodiment includes a mobile body group control device 601, an in-vehicle controller 501, and a mobile body 101. The mobile body group control device 601 manages the progress of orders (tasks) required for the entire system and the states of the respective mobile bodies (the progress status of the tasks given to the respective mobile bodies and the traveling positions), and executes a route plan for each mobile body. The mobile body group control device 601 includes a graph structure management unit 602, a mobile body structure management unit 603, an occlusion state management unit 604, an occlusion control unit 605, a mobile body state management unit 606, a destination determination unit 607, a route planning unit 608, a congestion degree determination unit 609, a graph structure dynamic change unit 610, a route determination unit 611, a communication unit 612, an instruction unit 613, and a display unit 614. Note that the occlusion control unit 605, the route planning unit 608, the congestion degree determination unit 609, the graph structure dynamic change unit 610, and the route determination unit 611 constitute a moving route creation unit 615. In FIG. 6, the lines with arrows represent the data flow. Hereinafter, based on the configuration example of FIG. 6, an outline of each functional block included in the mobile body group control device 601 will be described.

[0031] <Graph structure management unit 602> The graph structure management unit 602 manages a graph structure composed of node-link shapes. In this embodiment, as shown in FIG. 4(A), a graph structure is created and managed in which diagonal 45-degree direction links are added to the upper, lower, left, and right links of the nodes. Also, in a format where weights can be assigned to the links when passing through the links as needed. In this embodiment, the grid that constitutes the movement space 200 is square, and there is no difference in the movement distance in the vertical and horizontal directions. As an example, 1.0 is set for the left, right, up, and down links, and 1.4 is set for the diagonal links. Also, when it is desired to make a specific area impassable, the weights of the links that make up the area are set to a sufficiently large value (utilized by the graph structure dynamic change unit 610 described later). Also, attribute information may be set for the nodes. In this embodiment, in the layout of FIG. 2, assuming an operation of transporting the load picked up (placed manually) at the destination located in the uppermost grid to the destination located in the lowermost grid, with the nearest grid of the worker 105 (or the station 104) corresponding to the task in the uppermost and lowermost grids as the destination, the mobile body 101 repeatedly executes an operation of traveling back and forth between the destinations located in the uppermost and lowermost grids. Therefore, the nodes corresponding to the uppermost and lowermost grids are set as the destination nodes, and in the route planning processing ability described later, the route (the order of the links to pass through) to the destination nodes is determined.

[0032] <Mobile body structure management unit 603> The mobile body structure management unit 603 stores the basic information of the mobile body 101. Specifically, dimensional values related to the vehicle specifications such as the width, length, height, and wheelbase of the mobile body, and values related to the driving ability such as the maximum (minimum) value of the speed, the maximum (minimum) value of the angular velocity, and the maximum (minimum) value of the acceleration are managed. Also, the maximum battery capacity of the mobile body and the maximum weight of the load to be transported when transporting a load are managed. Also, the maximum occlusion section length handled by the occlusion control unit 605 described later is managed.

[0033] <Occlusion state management unit 604 · Occlusion control unit 605> The occlusion control unit 605 occupies a specific section of the route to the aforementioned destination in order to avoid collisions and interferences between moving bodies, and the occupied section does not permit the intrusion of other moving bodies. Based on the maximum occlusion section length managed (pre-set) by the moving body structure management unit 603, it calculates up to which grid the planned route can be occupied. Therefore, it does not always permit the occlusion of the grid with the maximum occlusion section length. As described with reference to FIG. 3, the travelable range varies each time depending on the occlusion state of other companies. However, in order to avoid interference with other moving bodies, the grid corresponding to the current position must always be occluded. Also, when moving diagonally in the 45-degree direction, which is a feature of the present invention, the four grids in the traveling direction are occluded (see FIG. 4(C)).

[0034] The occlusion state management unit 604 manages which grid each moving body is currently occluding (occupying). Since the occlusion area of the moving body changes every moment, here it updates the information managed internally in conjunction with the input / output information of the route planning unit 608 and the occlusion control unit 605, which will be described later.

[0035] <Moving body state management unit 606> The moving body state management unit 606 manages the state of each current moving body. Specifically, it manages the progress status of the tasks assigned to each moving body, the position information of each moving body transmitted from the in-vehicle controller 501 via the communication unit 612, the remaining battery level, and the weight of the load. Also, based on the information of the moving body structure management unit 603, it calculates the current remaining battery level and the weight of the load. As an example, when the remaining battery level falls below a specific threshold value or when an excessive weight is loaded, it sets it as an error state and transmits a status anomaly status different from that of a normal moving body to the route planning described later.

[0036] <Destination determination unit 607> The destination determination unit 607 determines the next destination of each mobile body based on the information of the order (task) to be achieved by the entire system, which is input from the instruction unit 613 described later. Although there is also a method of changing the order of destinations so that the productivity within an arbitrary time becomes maximum according to the content of the order, since it is not the core part of the present invention, in the present embodiment, the list within the order is sequentially given to the mobile bodies in the task waiting state from the top. However, regarding the mobile bodies in which a status abnormality status due to battery shortage or overloading has occurred in the mobile body status management unit 606, the dock area 205 (shown in FIG. 2) composed of the grid associated with the dock 107 is set as the destination.

[0037] The series of processes of the route planning unit 608, the congestion degree determination unit 609, the graph structure dynamic change unit 610, and the route determination unit 611 are the main points of the present invention. Therefore, only the outline of the process is described here, and the actual process flow will be described later according to the flowchart shown in FIG. 10.

[0038] <Route planning unit 608> The route planning unit 608 takes as input the graph structure managed by the graph structure management unit 602, the current position and status of each mobile body output from the mobile body status management unit 606, and the destination (grid) output from the destination determination unit 607, and performs a global route plan from the self-position to the destination. The global route is generated based on the graph structure. Since there are many existing methods such as Dijkstra's method and A* (A star) method for the global route planning method, the detailed description is omitted. In the present embodiment, an algorithm based on the A* method is used. The generated global route is represented by a set of links to be passed through, and reaching the destination is guaranteed by traveling in the order of these links. The route 206 shown in FIG. 2 shows an example of the generated global route. In the present embodiment, since diagonal movement is also permitted, the global route is generated by combining routes in a maximum of eight directions.

[0039] In this embodiment, in order to use the output of the route planning unit 608 in the congestion degree determination unit 609 described later, the spatio-temporal A* algorithm is used as a specific algorithm for route planning. The spatio-temporal A* algorithm is an A* algorithm with the addition of a time axis, and can calculate the shortest path considering the existence of dynamic obstacles. FIG. 7 shows a conceptual diagram of the spatio-temporal A* algorithm. As shown in this figure, when the grid space on the two-dimensional plane is used as the route search area, the search space is the three-dimensional map with the depth direction as the time axis. Since the positions of dynamic obstacles are managed in grid units (discrete values), in implementation, a hash map (a data structure consisting of pairs of positions and times) is used to handle dynamic obstacles. When calculating the shortest path from point A to point B, while considering static obstacles such as walls in the same way as the normal A* algorithm, the shortest path is determined while also performing collision detection with the registered dynamic obstacles.

[0040] In this embodiment, a mechanism is used that can sequentially plan the shortest path while resolving the route competition between moving bodies by regarding the planned routes of other vehicles as dynamic obstacles using the spatio-temporal A* algorithm. Here, in many prior studies and inventions using the spatio-temporal A* algorithm, during route planning, an accurate motion model of the moving body is often not handled, and in the calculation of one step, each moving body is set to move one grid (necessarily). However, in actual moving bodies, there are a maximum speed, an angular velocity, and acceleration and deceleration. Also, in this embodiment, since omnidirectional driving including diagonal driving is actively utilized, for example, the moving distance and time are different between the case of moving one grid in the left-right, up-down directions and the case of moving one grid in the 45-degree diagonal direction. Furthermore, even when changing direction by turning in place, the required time is different compared to normal forward movement.

[0041] Therefore, in this embodiment, the required time (cost) required for each operation of the moving body is set in consideration of the driving form and running ability of the moving body to be used. Here, as shown in FIG. 8, the time when the moving body moves one grid in the left-right, up-down directions without changing direction is set to 1.0, and the relative time (cost) required for turning and diagonal movement is set. FIG. 9 is a conceptual diagram showing the movement prediction results of a plurality of moving bodies, and illustrates the movement operations of four moving bodies every 0.5 seconds as an example.

[0042] The upper table shows the motion changes of the moving object, and the drawing (filling) pattern of each cell indicates the motion of the moving object at each time (forward movement, diagonal forward movement, spinning in place, etc.). The lower table shows the changes in the position (coordinate values) of the moving object at each time when the motion changes in the upper part occur.

[0043] In the conventional method, it is assumed that the vehicle moves one grid every one step (one second in the figure) or spins in place, and the travel time is estimated. In contrast, in this embodiment, the travel time is estimated based on the time required for each motion of the moving object. As a result, although there is a difference in accuracy depending on the control cycle of the moving object group control device 601, the difference in travel time between the planned and actual operations of each moving object becomes smaller, enabling accurate congestion prediction.

[0044] In the general A* method, regarding the calculation of the movement cost during path search, the sum of the actual cost g(n) to move to the target grid and the heuristic cost h(n) (in many cases, the distance between two points of the target grid and the destination) is used as the movement cost f(n). In this embodiment, when calculating the actual cost g(n), the sum of the pre-set link cost (passing weight) and the cost according to the movement of the moving object is used.

[0045] As described above, in this embodiment, when performing path search in the spatio-temporal A* method, the calculation is performed taking into account the direction of movement and the change in posture. At this time, regarding other moving objects (dynamic obstacles for the moving object), by inputting the path planning results of each moving object, the movement scheduled time in the time direction can be handled.

[0046] <Congestion determination unit 609> The congestion determination unit 609 sequentially changes the area where diagonal driving is allowed according to the congestion level of the moving object, and equalizes the congestion level of the moving object, thereby suppressing the productivity decrease caused by the blockage control when diagonal driving is utilized. Specifically, the planned paths of each moving object planned by the path planning unit 608 are once aggregated, and as a result, nodes where congestion is predicted are specified. The specific processing content will be described later.

[0047] <Graph structure dynamic change part 610> The graph structure dynamic change part 610 invalidates the diagonal links around the congestion prediction nodes for which the results are calculated by the congestion determination part 609 (the details of the processing will be described later). As a result, the mobile body 101 can actively utilize diagonal travel in sparse areas and adopt, for example, the conventional left - right - up - down direction + in - place turning movement method in dense areas, making it possible to realize a more efficient movement control system.

[0048] <Route determination part 611> The route determination part 611 transmits the routes of all mobile bodies output after going through the processes of the route planning part 608, the congestion determination part 609, and the graph structure dynamic change part 610 to the target route management part 502 of each mobile body 101 via the communication part 612.

[0049] <Instruction part 613 · Display part 614> The instruction part 613 is composed of the input device 601b and transmits information on the order (task) required for the entire transport system to the destination determination part 607. The display part 614 is composed of the display 601c and displays the shape of the entire movement space 200, the graph structure, the current planned routes of all mobile bodies, the mobile body states, etc., as shown in FIG. 2.

[0050] Hereinafter, based on the flowchart shown in FIG. 10 and using the screenshots of FIGS. 9, 11 to 13, the flow of the route planning process for a plurality of mobile bodies will be described.

[0051] <Flow of route planning process for a plurality of mobile bodies> The flowchart shown in FIG. 10 shows a series of processes executed by the mobile body group control device 601.

[0052] When the mobile body group control device 601 starts the process, it acquires the self - position of each mobile body (process 1001). Here, the current position and azimuth angle of each mobile body, which are the calculation results of the self - position calculation part 506 provided in each mobile body, are acquired via the communication parts 509, 612.

[0053] Following process 1001, the mobile state of each mobile object is acquired (process 1002). In this embodiment, as the mobile state, the current remaining battery level and the weight of the load are acquired. Then, mobile objects with overloading or low battery remaining are detected from the acquired information, and the current position and status (normal, low battery, overloaded state) of each mobile object are sent to the subsequent process 1003. Note that processes 1001 and 1002 are executed by the mobile state management unit 606.

[0054] Following process 1002, the destination of each mobile object is determined (process 1003). The destination is the grid 201 associated with stations 104 and 106, and as described above, it is the grid 201 near the stations 104 and 106 corresponding to the task among the uppermost and lowermost grids 201. However, if a mobile object with overloading or low battery remaining is detected in process 1002, the destination is changed to the dock area 205 respectively.

[0055] Following process 1003, the search priority is determined (process 1004). This process determines which mobile object to plan a route from in the route planning process described later. In the route planning process, each target mobile object is picked up one by one, a route search is performed taking into account the moving states of other mobile objects, after performing occlusion control, the local target position (sub-goal) of each mobile object is determined. Therefore, basically, the earlier the order of route planning, the more likely it is to obtain a route that can reach the destination preferentially. There are various guidelines for determining the order of mobile objects for which route planning is performed. Here, as an example, a guideline is adopted in which route planning is performed starting from the mobile object with the shortest distance between the current position and the destination of each mobile object. However, if there are mobile objects in an overloaded or low battery state, the search priority of those mobile objects is set to the last.

[0056] Following process 1004, route planning parameters are set (process 1005). Specifically, the route planning parameters may include, for example, the length of the blocked section in the traffic control, and the weight coefficient of the search cost (heuristic cost) inside the spatio-temporal A* algorithm, which is the base algorithm of the route planning method. Regarding the length of the blocked section, in this embodiment, a pre-set fixed value is continuously used. Here, as an example, the length of the blocked section is set to 3 grids in the normal status and 2 grids in the overloaded or low battery remaining state. The shorter the blocked section, the more limited the movable range may be depending on the blocked status of other moving bodies, and the arrival time to the destination may become longer (slower). Therefore, in this embodiment, in order to preferentially let the moving bodies in the normal state reach the destination, different lengths of the blocked section are set according to the status of each moving body.

[0057] Note that processes 1003, 1004, and 1005 are executed by the destination determination unit 607. Also, the above are the pre-processes performed before the actual route planning process. Details of the route planning process will be described hereinafter.

[0058] First, a moving body to be subject to route planning is determined (process 1006). Here, following the search order of the moving body determined in process 1004, the subsequent processes are executed.

[0059] Following process 1006, for the route planning of the target moving body, the previous planned route and the blocked area of other moving bodies (moving bodies that are not subject to route planning in process 1006) are acquired (process 1007). Here, as described in the explanation of the route planning unit 608, a three-dimensional vector obtained by adding the grid where other moving bodies move and the predicted time to reach the grid is input. Note that if this is the first step after the start of control, since there is no planned route for other moving bodies, only a three-dimensional vector combining the initial position and the current time of other moving bodies is input.

[0060] Following process 1007, a route planning process is executed (process 1008). Here, in addition to the planned routes of other vehicles and the closed area acquired in process 1007, the current graph structure is input and the route planning is executed. The route planning is carried out in accordance with the above-described spatio-temporal A* method. Note that processes 1006 to 1008 are executed by the route planning unit 608.

[0061] Following process 1008, the closed area is updated (process 1009). Note that process 1009 is executed by the occlusion control unit 605. Here, in accordance with the maximum occlusion section length set in process 1006, as described in the explanation of the occlusion control unit 605, the area where the target moving body can be occluded (occupied) is obtained. Thereafter, the area (grid) where the target moving body can be occluded is updated in the occlusion state management unit 604, and if there is a grid that was occluded in the previous step but has already completed traveling, the occlusion state of the target grid is released.

[0062] Process 1010 checks whether the route planning and closed area update (processes 1006 to 1009) for all moving bodies are completed. If completed, the process proceeds to the subsequent process 1011. If not completed, the process returns to process 1006 to execute the route planning for the remaining moving bodies. Note that the movement routes created in processes 1006 to 1010 are temporary movement routes (provisional movement routes) and do not necessarily match the movement routes transmitted to the moving body 101.

[0063] In process 1011, the degree of mixing is determined from the result of the route plan. Note that process 1011 is executed by the congestion determination unit 609. Here, the planned routes of each moving body obtained in the previous processes are aggregated, and as a result, the grids where congestion is expected are identified. As an example, based on the planned routes of each moving body, it is required that two or more moving bodies pass through the same grid within 3 seconds (double arrow 901 in FIG. 9). Hereinafter, the said grid is referred to as a congestion prediction grid. In the example of FIG. 9, the time (step) marked with an inverted triangle mark 902 corresponds to the timing when the congestion prediction grid occurs. In this embodiment, all the obtained congestion prediction grids are not used in the next process but are screened in advance. Specifically, in this embodiment, in view of the continuous occurrence time (number of steps) and the predicted occurrence time of the congestion prediction grid, only when those values are equal to or greater than or less than an arbitrary threshold are they input to the subsequent process. Here, only the grids where the congestion prediction grid occurs at the same position for 2 steps or more and the occurrence time (of the second step) is within 5 seconds from the current time are input to process 1011 which continues.

[0064] Following process 1011, based on the result obtained in process 1011, movement direction restrictions are given so that the links around the congestion grid in the pre-created graph structure cannot be passed through (process 1012). However, as for the embodiment of the movement direction restriction, a combination of a plurality of processes can be considered, such as a process that permits only specific moving bodies to drive diagonally or a process that makes specific moving bodies wait on the spot. Therefore, in this embodiment, a combination of movement direction restrictions that minimizes an arbitrary evaluation function is obtained.

[0065] Hereinafter, the specific processing content will be described with reference to FIGS. 11 to 13. FIG. 11(A) shows a cutout area 1102 cut out from the movement space 200 centered on the congestion prediction grid 1101 obtained in process 1011. The cutout area 1102 in the present embodiment is seven grids square, but the shape and size of the cutout area 1102 are not limited to this. For example, when the generation position of the congestion prediction grid 1101 occurs near the outer periphery of the entire travel area and a square area of a predetermined size cannot be cut out, the shape or size of the cutout area 1102 may be changed each time. However, as the cutout size (total number of grids) increases, the computational load of the optimization operation described later increases, so an appropriate upper limit cutout size is set based on the performance of the mobile body group control device 601.

[0066] In FIG. 11(A), four mobile bodies 101a to 101d are moving toward their respective sub-goals 201a to 201d. The sub-goals 201a to 201d are grids located on the outer periphery of the cutout area 1102 among the grids constituting the path to the original destination obtained in process 1008. Each of the mobile bodies 101a to 101d is given a path that actively utilizes diagonal movement with respect to its respective sub-goal 201a to 201d. Therefore, in FIG. 11(B) showing the state three seconds after FIG. 11(A), the mobile bodies 101a to 101d try to block each other's traveling directions, and as a result, a congestion state occurs where a specific mobile body or all mobile bodies stay in place. This is a result along the congestion prediction shown in FIG. 9. Thus, the application of a movement rule (pre-movement rule) that does not restrict the movement of each link in the graph structure can cause a congestion state of the mobile bodies.

[0067] In order to improve the above-described situation, in this embodiment, a movement rule (special movement rule) that makes it impossible to pass through diagonal links is applied to vary the paths of the moving bodies and prevent a dense state in advance. Here, as an example, for each preset constraint link pattern shown in FIG. 12(B), the sum of the movement costs to the sub-goals of all moving bodies is calculated, and the pattern (special movement rule) that minimizes the cost is identified. The constraint link sequence in FIG. 12(B) shows a combination of links that cannot be passed through, and the characters in parentheses correspond to the graph structure of the special area 1201 (a part of the cut-out area 1102) that is 5 grids square shown in FIG. 12(A). Note that the listed links are non-passable in both directions. There are many combinations of diagonal links even only within the 5-grid square special area 1201. Therefore, the example in FIG. 12(B) is a part of them, and the patterns may be further increased. However, it should be noted that increasing the patterns will increase the computational load of this process. Also, although not implemented in this embodiment, the cost of a pattern that allows only specific moving bodies to move diagonally may also be calculated. However, when different movement constraints are given for each moving body, it is necessary to prepare different graph structures for each moving body in the subsequent process, so care must be taken because the management and processing become complicated.

[0068] Here, according to the listed patterns, in the cut-out area 1102, a path planning by the spatio-temporal A* method with the sub-goal of each moving body as the destination is executed, and the movement cost to the sub-goal is calculated. More specifically, processes 1006 to 1010 are executed again for each moving body. Then, the sum of the movement costs of all moving bodies to the sub-goals is calculated, and the pattern that minimizes the cost is identified. As a result of the above process, here, as an example, it is assumed that the cost (C12) of the pattern #12 shown in FIG. 12(B) is the best result, and the subsequent process proceeds.

[0069] Following process 1012, based on the result of process 1012, a change to the graph structure is made (process 1013). For links determined not to permit diagonal movement, for a certain period of time, by sufficiently increasing the weight (passing cost) assigned to the link, a path that does not pass through the link is intentionally generated. In FIG. 13(A), the link 1301 shown as a solid line is the target, and for a certain period of time, all moving objects are made unable to pass through link 1301. Also, in the congestion determination process in process 1011, after a predetermined time (for example, 3 seconds) has elapsed from the time when congestion is predicted to occur, the weight of link 1301 is returned to its original state. Note that processes 1012 and 1013 are executed by the graph structure dynamic change unit 610. FIG. 13(B) shows the result of the path planning process in the next control cycle based on the set movement constraints. By temporarily making the diagonal links in the area five grids square in the center impassable, a path is generated such that all moving objects bypass the vicinity of the center respectively. As a result, the density of the moving objects is leveled, and the overall efficiency is improved.

[0070] The above is the flow of the path planning process for a plurality of moving objects. In this embodiment, the above processes are repeatedly executed until all moving objects reach their destinations (process 1014). More precisely, even after an arbitrary moving object reaches its destination, until the list of the above order is completed, since the system continues to operate, the above processes are repeatedly executed until all tasks (travel to the destination) sequentially given to each moving object are completed.

[0071] The above is the content of the moving object group control device 601, the moving object group control system 600, and the moving object group control method in this embodiment.

[0072] (Summary) In this embodiment, in a mobile body group control device 601 that controls a plurality of mobile bodies 101, a destination determination unit 607 that determines destinations of the plurality of mobile bodies 101, a movement route creation unit 615 that creates movement routes of the plurality of mobile bodies 101 to the destinations, and a communication unit 612 that transmits the movement routes to the plurality of mobile bodies 101 are provided. The movement route creation unit 615 applies a predetermined pre-movement rule to the entire area of the movement space 200 of the plurality of mobile bodies 101, creates a tentative movement route of the plurality of mobile bodies 101 to the destinations, evaluates a movement prediction result when the plurality of mobile bodies 101 move along the tentative movement route based on a predetermined evaluation item, sets, based on the evaluation result of the movement prediction result, an area where a special movement rule different from the pre-movement rule is applied in the movement space 200 as a special area 1201, applies the special movement rule to the special area 1201 and applies the pre-movement rule to areas other than the special area 1201 in the movement space 200, and then creates the movement route.

[0073] Also, the mobile body group control system 600 in this embodiment includes a mobile body group control device 601 and a plurality of mobile bodies 101.

[0074] Also, in this embodiment, in a mobile body group control method for controlling a plurality of mobile bodies 101, a first step (process 1003) of determining destinations of the plurality of mobile bodies 101, a second step (processes 1006 to 1010) of applying a predetermined pre-movement rule to the entire area of the movement space 200 of the plurality of mobile bodies 101 and creating a tentative movement route of the plurality of mobile bodies 101, a third step (process 1011) of evaluating a movement prediction result when the plurality of mobile bodies 101 move along the tentative movement route based on a predetermined evaluation item, a fourth step (process 1012) of setting, based on the evaluation result of the third step, an area where a special movement rule different from the pre-movement rule is applied in the movement space 200 as a special area 1201, and a fifth step (process 1013) of applying the special movement rule to the special area 1201 and applying the pre-movement rule to areas other than the special area 1201 in the movement space 200 and then creating a movement route of the plurality of mobile bodies 101 to the destinations are provided.

[0075] According to the present embodiment configured as described above, a special movement rule different from the pre-movement rule is applied to the special area 1201 set based on the evaluation result of the movement prediction result of the provisional movement route created under the application of the pre-movement rule, and then the movement route of the moving body 101 is created. As a result, the density of the moving body 101 in the movement space 200 is leveled, so that it is possible to improve the overall efficiency by preventing excessive detours and waiting of the moving body 101.

[0076] In addition, the movement route creation unit 615 in the present embodiment extracts a congestion prediction point (congestion prediction grid 1101) where two or more of the plurality of moving bodies 101 are expected to pass within a predetermined time frame based on the evaluation result of the movement prediction result, and sets a predicted congestion area 1201 including the congestion prediction point as the special area 1201. Thereby, it becomes possible to avoid congestion of the moving body 101 in the predicted congestion area 1201.

[0077] In addition, in the present embodiment, the special movement rule includes setting a movement direction restriction that makes it impossible to pass through a route (link 1301) in a specific direction in the predicted congestion area 1201. Thereby, it becomes possible to avoid congestion of the moving body 101 in the predicted congestion area 1201 while allowing passage through routes in directions other than the specific direction in the predicted congestion area 1201.

[0078] In addition, the movement route creation unit 615 in the present embodiment sets the movement direction restriction only for a specific moving body 101 among the plurality of moving bodies 101. Thereby, it becomes possible to avoid congestion of the moving body 101 in the predicted congestion area 1201 without restricting the travel of the moving body 101 other than the specific moving body 101 in the predicted congestion area 1201.

[0079] In addition, the movement route creation unit 615 in the present embodiment releases the setting of the movement direction restriction after a predetermined time has elapsed from the predicted occurrence time of the predicted congestion area 1201. Thereby, it becomes possible to prevent the travel of the moving body 101 in the predicted congestion area 1201 from being excessively restricted.

[0080] Also, in the present embodiment, the predetermined evaluation item is the movement cost of a plurality of moving bodies 101. The movement route creation unit 615 creates a plurality of movement route candidates while changing the special movement rule, and selects, as the movement route, the movement route candidate with the minimum movement cost among the plurality of movement route candidates. Thereby, it becomes possible to optimize the overall efficiency of the plurality of moving bodies 101.

[0081] In addition, the moving body group control device 601 in the present embodiment includes a display unit 601c that displays the operation status of a plurality of moving bodies 101. Thereby, since the administrator of the moving body group control system 600 can grasp the operation status of the plurality of moving bodies 101, it becomes possible to promptly perform maintenance of the moving body group control system 600 as needed.

[0082] In addition, the movement route creation unit 615 in the present embodiment calculates the movement cost by summing up the time required for each operation when the plurality of moving bodies 101 move along the provisional movement route. Thereby, it becomes possible to accurately calculate the movement cost when the moving body 101 moves along the provisional movement route.

[0083] Note that the present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments are shown for explaining the present invention in an easy-to-understand manner and are not necessarily limited to those having all the configurations described.

Description of Reference Numerals

[0084] 100…Operating environment, 101, 101a~101d…Moving bodies, 102…Conveyor, 103…Article, 104…Station, 105…Worker, 106…Station, 107…Dock, 108…Worker, 109…Conveyor, 200…Moving space, 201…Grid, 201a~201d…Sub-goals, 202…Node, 203…Link, 204…Graph structure, 205…Dock area, 206…Route, 301, 302…Moving bodies, 303, 304…Destinations, 305, 306…Areas, 401…Graph structure, 402…Moving body, 403…Destination, 404, 405…Occupied areas, 501…On-vehicle controller, 502…Target route management unit, 503…On-vehicle sensor, 504…Travel map management unit, 505…Control command generation unit, 506…Self-position calculation unit, 507…Drive unit, 508…Encoder, 509…Communication unit, 600…Moving body group control system, 601…Moving body group control device, 601a…Control server, 601b…Input device, 601c…Display (display unit), 602…Graph structure management unit, 603…Moving body structure management unit, 604…Obstruction state management unit, 605…Obstruction control unit, 606…Moving body state management unit, 607…Destination determination unit, 608…Route planning unit, 609…Congestion degree determination unit, 610…Graph structure dynamic change unit, 611…Route determination unit, 612…Communication unit, 613…Instruction unit, 614…Display unit, 615…Moving route creation unit, 901…Double arrow, 902…Inverted triangle mark, 1001~1014…Processes, 1101…Congestion prediction grid (congestion prediction point), 1102…Cut-off area, 1201…Predicted congestion area (special area), 1301…Link.

Claims

1. In a mobile body group control device for controlling a plurality of mobile bodies, a destination determination unit that determines destinations of the plurality of mobile bodies; a movement route creation unit that creates movement routes of the plurality of mobile bodies to the destinations; and a communication unit that transmits the movement routes to the plurality of mobile bodies, wherein the movement route creation unit applies a predetermined pre-movement rule to the entire area of the movement space of the plurality of mobile bodies, creates a tentative movement route of the plurality of mobile bodies to the destinations, evaluates a movement prediction result when the plurality of mobile bodies move along the tentative movement route based on a predetermined evaluation item, sets, based on the evaluation result of the movement prediction result, an area where a special movement rule different from the pre-movement rule is applied in the movement space as a special area, applies the special movement rule to the special area and applies the pre-movement rule to areas other than the special area in the movement space, and then creates the movement route A mobile body group control device characterized by the above.

2. In the mobile body group control device according to Claim 1, wherein the movement route creation unit extracts, based on the evaluation result of the movement prediction result, a congestion prediction point where two or more of the plurality of mobile bodies are expected to pass within a predetermined time frame, and sets a predicted congestion area including the congestion prediction point as the special area A mobile body group control device characterized by the above.

3. In the mobile body group control device according to Claim 2, the special movement rule includes setting a movement direction constraint that makes it impossible to pass through a route in a specific direction in the predicted congestion area A mobile body group control device characterized by the above.

4. In the mobile body group control device according to Claim 3, The movement path creation unit sets the movement direction constraint only for a specific moving body among the plurality of moving bodies. A moving body group control device characterized by this.

5. In the moving body group control device according to claim 3, The movement path creation unit releases the setting of the movement direction constraint after a predetermined time has elapsed from the predicted occurrence time of the predicted congestion area. A moving body group control device characterized by this.

6. In the moving body group control device according to claim 1, The predetermined evaluation item is the movement cost of the plurality of moving bodies, The movement path creation unit, creates a plurality of movement path candidates while changing the special movement rule, and selects, as the movement path, the movement path candidate with the minimum movement cost among the plurality of movement path candidates. A moving body group control device characterized by this.

7. In the moving body group control device according to claim 6, The movement path creation unit calculates the movement cost by summing up the time required for each operation when the plurality of moving bodies move along the tentative movement path. A moving body group control device characterized by this.

8. In the moving body group control device according to claim 1, It includes a display unit for displaying the operation status of the plurality of moving bodies. A moving body group control device characterized by this.

9. The moving body group control device according to claim 1, and It includes the plurality of moving bodies. A moving body group control system characterized by this.

10. In a moving body group control method for controlling a plurality of moving bodies, A first procedure for determining destinations of the plurality of mobile objects; A second procedure for creating tentative movement routes to the destinations of the plurality of mobile objects after applying predetermined pre-movement rules to all areas of the movement space of the plurality of mobile objects; A third procedure for evaluating movement prediction results when the plurality of mobile objects move along the tentative movement routes based on predetermined evaluation items; A fourth procedure for setting, as a special area, an area in the movement space to which a special movement rule different from the pre-movement rule is applied based on the evaluation result of the third procedure; A fifth procedure for creating movement routes to the destinations of the plurality of mobile objects after applying the special movement rule to the special area and applying the pre-movement rule to areas other than the special area in the movement space. A method for controlling a group of mobile objects, characterized by the above.

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