Guided vehicle system and guided vehicle control method

Abstract

[Problem] To inhibit reduction in conveyance efficiency of a system as a whole. [Solution] A controller 20 comprises a charging instruction unit 21 that instructs each conveyor vehicle 10 to start charging. The charging instruction unit 21: carries out a first determination process of determining whether a charging rate of a plurality of conveyor vehicles 10 as a whole is less than a first threshold value and, when the charging rate of the plurality of conveyor vehicles 10 as a whole is determined to be less than the first threshold value, instructs at least any one of the conveyor vehicles 10 to start charging; and carries out a second determination process of determining whether a charging rate of each conveyor vehicle 10 is less than a second threshold value less than the first threshold value and, when the charging rate of the conveyor vehicle 10 is determined to be less than the second threshold value, instructs the conveyor vehicle 10 to start charging.

Description

[Technical Field]

[0001] The present invention relates to a guided vehicle system and a method for controlling a guided vehicle. [Background technology]

[0002] Conventionally, a guided vehicle system that transports articles based on a transport command has been known in factories and the like. In the guided vehicle system, a battery for driving the vehicle that transports the articles based on the transport command is mounted on the vehicle, and a charging facility is provided to charge the battery while the vehicle is stopped. Patent Document 1 discloses a technology in which, when a guided vehicle whose battery voltage has dropped to a level requiring charging is driven to a charging facility to be charged, a guided vehicle that has taken the longest time to charge among those being charged at each charging facility is started, thereby ensuring a certain number of guided vehicles on a main route. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4539887 Summary of the Invention [Problem to be solved by the invention]

[0004] In the conventional technology, the battery voltage of each transport vehicle is checked individually, and when a transport vehicle drops to a level requiring charging, it is sent to a charging facility to be charged, and one of the transport vehicles that is already charging at the charging facility is returned to the main route while it is still charging. In other words, in the conventional technology, when multiple transport vehicles drop to a level requiring charging at the same time, the multiple transport vehicles that are already charging at the charging facility are returned to the main route at the same time. As a result, in the conventional technology, multiple transport vehicles that are not sufficiently charged exist in the system, and as a whole, transport vehicles that require charging occur within a short period of time, which reduces the transport efficiency of the entire system.

[0005] The present invention provides a guided vehicle system and a method for controlling a guided vehicle that can suppress a decrease in the transport efficiency of the entire system. [Means for solving the problem]

[0006] A transport vehicle system according to one embodiment of the present invention is a transport vehicle system having a plurality of transport vehicles that transport items, a controller that assigns transport commands to one of the plurality of transport vehicles, and a charging device located on a route along which the plurality of transport vehicles can move and that supplies power to the transport vehicles, wherein the controller is equipped with a charging instruction unit that instructs each transport vehicle to start charging, and the charging instruction unit performs a first determination process to determine whether the charging rate of all of the plurality of transport vehicles is less than a first threshold, and if it determines that the charging rate of all of the plurality of transport vehicles is less than the first threshold, instructs at least one of the transport vehicles to start charging, and performs a second determination process to determine whether the charging rate of each transport vehicle is less than a second threshold that is smaller than the first threshold, and if it determines that the charging rate of a transport vehicle is less than the second threshold, instructs the transport vehicle to start charging.

[0007] A transport vehicle control method according to an embodiment of the present invention is a transport vehicle control method in a transport vehicle system having a plurality of transport vehicles that transport items, a controller that assigns transport commands to any of the plurality of transport vehicles, and a charging device located on a route along which the plurality of transport vehicles can move and that supplies power to the transport vehicles, and includes the steps of: having the controller perform a first determination process to determine whether the charging rate of all of the plurality of transport vehicles is less than a first threshold; and if it is determined that the charging rate of all of the plurality of transport vehicles is less than the first threshold, instructing at least one of the transport vehicles to start charging; and performing a second determination process to determine whether the charging rate of each transport vehicle is less than a second threshold that is smaller than the first threshold; and if it is determined that the charging rate of a transport vehicle is less than the second threshold, instructing the transport vehicle to start charging. [Effects of the Invention]

[0008] According to the transport vehicle system and transport vehicle control method of the present invention, when the charging rate of all multiple transport vehicles is less than a first threshold, one of the transport vehicles is instructed to start charging, and transport vehicles whose charging rates are less than a second threshold that is smaller than the first threshold are instructed to start charging.Therefore, compared to conventional technology that instructs the start of charging using only the individual charging rates of each transport vehicle, it is possible to prevent multiple transport vehicles from being instructed to start charging at the same time, and to prevent a decrease in transport efficiency throughout the system.

[0009] In the transport vehicle system of the above aspect, the charge instructing unit may check a system margin rate, which indicates the degree of margin for all of the multiple transport vehicles in processing a transport command, at a predetermined timing. If the charge instructing unit determines that the degree of margin indicated by the system margin rate is equal to or greater than a predetermined value and that the charging rates of all of the multiple transport vehicles are less than a first threshold, the charge instructing unit instructs at least one of the transport vehicles to start charging. If the charge instructing unit determines that the degree of margin indicated by the system margin rate is equal to or greater than a predetermined value and that the charging rates of the multiple transport vehicles are less than a second threshold, the charge instructing unit instructs the transport vehicle to start charging. According to this aspect, the charge instructing unit instructs the transport vehicles to start charging while taking the system margin rate into consideration, thereby preventing a situation in which no transport vehicle is available to be assigned a transport command. Furthermore, in the transport vehicle system of the above aspect, the charge instructing unit may check the system margin rate periodically at a predetermined timing. According to this aspect, the charge instructing unit instructs the transport vehicles to charge while periodically checking the system margin rate, thereby preventing the occurrence of a transport vehicle that is unable to execute a transport command due to a decrease in charging rate. In the guided vehicle system of the above aspect, the charging instructing unit may check whether at least one of the following is satisfied as the system margin rate: an effective vehicle ratio, which indicates the ratio of standby vehicles to the total number of guided vehicles, is equal to or greater than a predetermined ratio; the total transport volume of the multiple guided vehicles is less than a predetermined transport volume; and the operating rate of the multiple guided vehicles is less than a predetermined operating rate. According to this aspect, the guided vehicle system calculates the system margin rate using various information related to transport efficiency, thereby effectively suppressing a decrease in transport efficiency throughout the system. In the guided vehicle system of the above aspect, the charging instructing unit may instruct two or more guided vehicles to start charging at different times when there are multiple guided vehicles with charge rates less than a first threshold. According to this aspect, multiple guided vehicles are not directed to charge at the same time, thereby suppressing a decrease in transport efficiency throughout the system. In the guided vehicle system of the above aspect, the charging instructing unit may instruct the start of charging of guided vehicles in order, starting with the vehicle closest to the charging device. According to this aspect, charging efficiency can be improved when multiple guided vehicles require charging.In the guided vehicle system of the above aspect, the charging instruction unit may instruct the start of charging in order of the guided vehicle with the lowest charging rate. According to this aspect, it is possible to prevent an increase in the number of guided vehicles that cannot execute a transportation command due to a decrease in charging rate. In the guided vehicle system of the above aspect, the controller may acquire status information of the plurality of guided vehicles by periodically communicating with the plurality of guided vehicles. According to this aspect, it is possible to identify a guided vehicle that is suitable for instructing charging. In the guided vehicle system of the above aspect, the plurality of guided vehicles may be movable in a first direction or a second direction along a lattice-like track extending in a first direction and a second direction intersecting the first direction, respectively, and the charging device may be provided corresponding to one square of the lattice-like track. According to this aspect, the system can be applied to a guided vehicle system arranged on a lattice-like track. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 10 is a diagram illustrating an example of processing of the guided vehicle system according to the embodiment. [Figure 2] 1 is a perspective view illustrating an example of a guided vehicle system according to an embodiment. [Figure 3] FIG. 1 is a perspective view illustrating an example of a transport vehicle according to an embodiment. [Figure 4] FIG. 2 is a front view illustrating an example of a transport vehicle according to the embodiment. [Figure 5] 10A and 10B are diagrams illustrating an example of transmission and reception of state information according to an embodiment. [Figure 6] 10 is a flowchart illustrating an example of a processing flow by a controller according to the embodiment. [Figure 7] 10A and 10B are diagrams illustrating another example of processing by the charge instruction unit according to the embodiment. [Figure 8] 10A and 10B are diagrams illustrating another example of processing by the charge instruction unit according to the embodiment. [Figure 9] FIG. 10 is a diagram illustrating an example of an image of a charging instruction process according to the embodiment. [Figure 10] FIG. 10 is a diagram illustrating an example of an image of a charging instruction process according to the prior art. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments will be described with reference to the drawings. The present invention is not limited to the embodiments described below. In the drawings, the scale may be appropriately changed, such as by enlarging, reducing, or emphasizing portions, in order to explain the embodiments. Furthermore, directions in the drawings may be described using an XYZ Cartesian coordinate system. In the XYZ Cartesian coordinate system, the horizontal direction is defined as the X direction and the Y direction, and the vertical direction is defined as the Z direction. Note that the traveling direction of the transport vehicle can be changed to another direction from the state shown in the drawings, and for example, the transport vehicle may travel along a curved direction. In the following description, the X direction, Y direction, and Z direction will be described assuming that the direction indicated by the arrow in the drawing is the + direction and the direction opposite to the arrow is the - direction. Furthermore, the direction of rotation around the Z axis is referred to as the θZ direction.

[0012] FIG. 1 is a diagram illustrating an example of processing by a transport vehicle system according to an embodiment. The transport vehicle system 100 is a system that transports an item 1 (see FIG. 3, etc.), such as a FOUP (Front-Opening Unified Pod) that stores semiconductor wafers or a reticle pod that stores reticles, in a clean room of a semiconductor manufacturing factory, for example. In the embodiment, a transport vehicle 10 that travels on a lattice-shaped track R suspended from the ceiling will be described as an example. Note that the transport vehicle 10 may be a rail-guided vehicle or a trackless vehicle that travels on the ground.

[0013] As shown in FIG. 1, the transport vehicle system 100 includes a plurality of transport vehicles 10 that transport articles 1, a controller 20 that assigns transport commands to any of the plurality of transport vehicles 10, and a charging device 30 that is located on a path (e.g., a lattice track R) along which the plurality of transport vehicles 10 can move and that supplies power to the transport vehicles 10. Each transport vehicle 10 can move in a first direction D1 or a second direction D2 along the lattice track R, which extends in a first direction D1 and a second direction D2 intersecting the first direction D1. The lattice track R is a type of track and is installed near the ceiling of a clean room. The charging device 30 is provided corresponding to one of the squares of the lattice track R. The charging device 30 supplies power to a battery 116 (see FIG. 4) of the transport vehicle 10. The lattice track R has a first track R1 arranged along the X direction (e.g., first direction D1), a second track R2 arranged along the Y direction (e.g., second direction D2), and a partial track R3 arranged at the intersection of the first track R1 and the second track R2. In FIG. 1, the four transport vehicles 10 are represented as transport vehicle 10A, transport vehicle 10B, transport vehicle 10C, and transport vehicle 10D, respectively. When transport vehicles 10A, transport vehicle 10B, transport vehicle 10C, and transport vehicle 10D are not particularly distinguished from one another, they are simply referred to as "transport vehicles 10." However, the number of transport vehicles 10 is not limited to four.

[0014] Furthermore, each guided vehicle 10 transmits its own status information to the controller 20 in response to a request (periodic request) from the controller 20. The controller 20 acquires status information of the multiple guided vehicles 10 through periodic communication with the multiple guided vehicles 10, and assigns a transport command to one of the guided vehicles 10 based on the acquired status information. The status information includes, for example, identification information for identifying the guided vehicle 10, as well as information on the current location, destination, traveling status (e.g., waiting, charging, traveling to grab a load, traveling to unload a load, etc.), charging rate (remaining battery capacity), etc. The guided vehicle 10 travels on the lattice track R upon receiving a transport command from the controller 20. The transport command includes information on the planned transport route along which the guided vehicle 10 transporting the item 1 is to travel. The transport route information is information that specifies at least a portion of the travel route from the departure point (from) of the guided vehicle 10 to the destination (to).

[0015] In the above-described configuration, the controller 20 includes a charging instruction unit 21 that instructs each guided vehicle 10 to start charging. The charging instruction unit 21 performs a first determination process to determine whether the charging rates of all the multiple guided vehicles 10 are less than a first threshold, and when it is determined that the charging rates of all the multiple guided vehicles 10 are less than the first threshold, it instructs at least one of the guided vehicles 10 to start charging. Specifically, the charging instruction unit 21 calculates the charging rates of all the multiple guided vehicles 10 present on the lattice track R based on information about the charging rates (remaining battery capacity) included in the status information received from each guided vehicle 10. Then, the charging instruction unit 21 performs a first determination process to determine whether the calculated charging rates of all the multiple guided vehicles 10 are less than the first threshold. At this time, when it is determined in the first determination process that the charging rates of all the multiple guided vehicles 10 are less than the first threshold, the charging instruction unit 21 instructs at least one of the guided vehicles 10 to start charging. Here, the number of transport vehicles 10 to be instructed to start charging may be set in advance based on the scale of the transport vehicle system 100, the number of transport vehicles 10 to be introduced, etc. Note that when the charge instructing unit 21 determines in the first determination process that the charge rates of all of the multiple transport vehicles 10 are less than the first threshold, the charge instructing unit 21 may identify transport vehicles 10 whose charge rates are less than the first threshold based on information about the charge rates (remaining battery capacity) included in the status information of each transport vehicle 10, and instruct the identified transport vehicles 10 to start charging. At this time, the charge instructing unit 21 may instruct at least one of the transport vehicles 10 whose charge rates are less than the first threshold to start charging.

[0016] Furthermore, the charge instruction unit 21 performs a second determination process to determine whether the charging rate of each transport vehicle 10 is less than a second threshold value that is smaller than the first threshold value, and when it determines that the charging rate of the transport vehicle 10 is less than the second threshold value, it instructs the transport vehicle 10 to start charging. Specifically, the charge instruction unit 21 performs the second determination process to determine whether the charging rate of each transport vehicle 10 is less than a second threshold value that is smaller than the first threshold value, based on information about the charging rate (remaining battery capacity) included in the status information received from each transport vehicle 10. At this time, the charge instruction unit 21 identifies transport vehicles 10 whose charging rates are less than the second threshold value in the second determination process, and instructs the identified transport vehicles 10 to start charging. Here, the second threshold value is, for example, a charging requirement level for the charging rate of the battery 116. That is, the controller 20 sets a first threshold value, which is greater than the second threshold value indicating the required charging level, as the threshold value for the charging rate of all the multiple guided vehicles 10, and when the charging rate has decreased to a certain level relative to the overall system, the controller 20 charges at least one of the guided vehicles 10. This allows the timing of issuing an instruction to start charging to be delayed, thereby suppressing a decrease in the transportation efficiency of the entire guided vehicle system 100. In other words, the controller 20 compares the charging rate of the entire system with the threshold value to determine which guided vehicles 10 should start charging, and normally directs guided vehicles 10 that do not yet require charging to the charging device 30. This allows the timing of issuing an instruction to start charging to be delayed, thereby suppressing a decrease in the transportation efficiency of the entire guided vehicle system 100. Furthermore, when issuing an instruction to start charging to a guided vehicle 10 whose charging rate is less than the first threshold value in the first determination process, the controller 20 charges a guided vehicle 10 that has a low charging rate relative to the overall system with ample time to charge, even if it does not normally require charging. This prevents a guided vehicle 10 that requires charging (has a required charging level) from occurring in a short period of time, thereby suppressing a decrease in the transportation efficiency of the entire guided vehicle system 100.

[0017] Furthermore, the charging instruction unit 21 may check a system margin rate, which indicates the degree of margin of all of the multiple guided vehicles 10 with respect to processing of a transportation command, at a predetermined timing, and when it is determined that the degree of margin indicated by the system margin rate is equal to or greater than a predetermined value and the charging rate of all of the multiple guided vehicles 10 is less than a first threshold, instruct at least one of the guided vehicles 10 to start charging. Furthermore, when it is determined that the degree of margin indicated by the system margin rate is equal to or greater than a predetermined value and the charging rate of a guided vehicle 10 is less than a second threshold, the charging instruction unit 21 may instruct that guided vehicle 10 (the guided vehicle 10 whose charging rate is less than the second threshold) to start charging. Specifically, the charging instruction unit 21 checks whether at least one of the following is satisfied: an available vehicle ratio, which indicates the ratio of waiting guided vehicles 10 to all of the multiple guided vehicles 10, is equal to or greater than a predetermined ratio; the total transport volume of the multiple guided vehicles 10 is less than a predetermined transport volume; and the operating rate of all of the multiple guided vehicles 10 is less than a predetermined operating rate. If at least one of these is satisfied, it is determined that there is margin as the system margin rate.

[0018] The effective vehicle ratio corresponds to the ratio of the guided vehicles 10 that can execute a transport command (can be used to execute a transport command). For example, this ratio can be calculated by calculating the ratio of waiting guided vehicles 10 to the total number of guided vehicles 10 based on the driving status included in the status information. The transport volume corresponds to the number of transport commands per unit time, or a value weighted toward transport commands with long transport distances, in addition to the number of transport commands per unit time. The operation rate corresponds to the ratio of the guided vehicles 10 that are operating in the entire guided vehicle system 100. For example, this ratio can be calculated by calculating the ratio of the guided vehicles 10 that are currently grabbing or unloading cargo to the total number of the guided vehicles 10 based on the driving status included in the status information. The threshold values ​​for each item of the system margin rate can be appropriately set depending on the layout, transport pattern, etc. of the guided vehicle system 100. For example, the predetermined transport volume can be set smaller than the limit value of the transport volume that can process transport commands across the entire group of the guided vehicles 10, thereby allowing for a margin in the execution of transport. For example, the predetermined operation rate can be set smaller than the limit value of the operation rate across the entire group of the guided vehicles 10, thereby allowing for a margin in the number of guided vehicles 10 that are in operation. The charge instruction unit 21 periodically checks the system margin rate at a predetermined timing. For example, the period for checking the system margin rate is longer than the period for transmitting status information from each transport vehicle 10. In one embodiment, the period for checking the system margin rate is about once per minute, whereas the period for transmitting status information is once every few seconds. After checking the system margin rate as described above, or prior to checking the system margin rate, the charge instruction unit 21 executes a first determination process and a second determination process.

[0019] FIG. 2 is a perspective view showing an example of a guided vehicle system according to an embodiment. As described above, the guided vehicle system 100 is a system that transports an article 1, such as a FOUP that stores semiconductor wafers or a reticle pod that stores reticles, in a clean room of a semiconductor manufacturing factory. A guided vehicle 10 and a charging device 30 are arranged on a lattice track R. The lattice track R is suspended from the ceiling of a clean room or the like via a hanging member H. A plurality of first tracks R1 are arranged along the X direction (e.g., first direction D1). A plurality of second tracks R2 are arranged along the Y direction (e.g., second direction D2). In this embodiment, the first direction D1 along which the first track R1 runs is perpendicular to the second direction D2 along which the second track R2 runs. The partial track R3 is arranged at the intersection of the first track R1 and the second track R2. A gap is provided between the first track R1 and the partial track R3, and between the second track R2 and the partial track R3. The gap is a portion through which a connecting portion 130 (see FIG. 3), which is a part of the guided vehicle 10, passes when the guided vehicle 10 travels on the first track R1 and crosses the second track R2, or when the guided vehicle travels on the second track R2 and crosses the first track R1. Therefore, the gap is provided with a width that allows the connecting portion 130 to pass through. The first track R1, the second track R2, and the partial track R3 are arranged along the same or substantially the same horizontal plane. In the lattice-shaped track R, the first track R1 and the second track R2 are orthogonal to each other, so that multiple cells C are adjacent to each other in a planar view. One cell C is an area or space surrounded by two first tracks R1 adjacent to each other in the Y direction and two second tracks R2 adjacent to each other in the X direction.

[0020] FIG. 3 is a perspective view showing an example of a transport vehicle according to an embodiment. FIG. 4 is a front view showing an example of a transport vehicle according to an embodiment. As shown in FIGS. 3 and 4, the transport vehicle 10 has a main body 110, a traveling unit 120, a connecting unit 130, and a control unit 140. The transport vehicle 10 moves along a lattice track R and transports an item 1 such as a FOUP or a reticle pod. A plurality of transport vehicles 10 may be arranged on the lattice track R. By transporting the item 1 using a plurality of transport vehicles 10, it is possible to improve the efficiency of transporting the item 1.

[0021] The main body 110 is disposed below (on the -Z side of) the lattice track R. The main body 110 is formed, for example, in a rectangular shape in a plan view. Therefore, the top surface 110a of the main body 110 is rectangular and has four corners. The main body 110 is formed to have dimensions that fit within one cell C of the lattice track R in a plan view. Therefore, transport vehicles 10 traveling next to each other on the lattice track R do not interfere with each other. The main body 110 has an elevation drive unit 114 that vertically raises and lowers the article holder 113 that holds the article 1, and a lateral ejection mechanism 111 that moves the elevation drive unit 114. The article holder 113 holds the article 1 by suspending it by gripping a flange 1a provided on the top of the article 1. The article holding unit 113 is, for example, a chuck having claws 113a that are movable in the horizontal direction, and hangs and holds the article 1 by inserting the claws 113a below the flange 1a of the article 1 and raising the article holding unit 113. The article holding unit 113 is connected to the lower end of a hanging member 113b such as a wire or a belt.

[0022] The lifting / lowering drive unit 114 is, for example, a hoist, and lowers the article holding unit 113 by letting out the hanging member 113b, and raises the article holding unit 113 by reeling in the hanging member 113b. The lifting / lowering drive unit 114 is controlled by the control unit 140 to lower or raise the article holding unit 113 at a predetermined speed. The lifting / lowering drive unit 114 is also controlled by the control unit 140 to hold the article holding unit 113 at a target height. The lateral delivery mechanism 111 has, for example, multiple movable plates arranged in a stacked manner in the Z direction. The movable plates are movable in the Y direction. The lifting / lowering drive unit 114 is attached to the lowest movable plate. The lateral delivery mechanism 111 moves the movable plate using a drive device (not shown), and can laterally deliver the lifting / lowering drive unit 114 and the article holding unit 113 attached to the lowest movable plate in the traveling direction.

[0023] The rotating unit 112 has a rotating member 112a and a rotation drive unit 112b. The rotating member 112a is rotatable around the Z-axis. The rotating member 112a supports the lateral dispensing mechanism 111. The rotation drive unit 112b uses an electric motor or the like and rotates the rotating member 112a around the Z-axis. The rotating unit 112 rotates the rotating member 112a by the driving force from the rotation drive unit 112b, and can rotate the lateral dispensing mechanism 111 (the lifting / lowering drive unit 114 and the article holding unit 113) around the Z-axis. In addition to the rotating unit 112 that controls the direction in which the lifting / lowering drive unit 114 and the article holding unit 113 are laterally dispensed, a rotating unit that controls the attitude of the lifting / lowering drive unit 114 and the article holding unit 113 in a horizontal plane may be further provided between the lateral dispensing mechanism 111 and the lifting / lowering drive unit 114.

[0024] The main body 110 includes a battery 116 and a charging electrode 117. The battery 116 is disposed inside the main body 110. The battery 116 stores power to be supplied to the traveling unit 120, the rotation drive unit 112b, the lift drive unit 114, and the like of the transport vehicle 10. A secondary battery such as a lithium-ion battery is used as the battery 116. The capacity of the battery 116 is determined by the power used by the transport vehicle 10, the operating time, and the like. The charging electrode 117 is held by a holder 118 and disposed on the upper surface 110a of the main body 110. The charging electrodes 117 are provided side by side at two locations on the upper surface of the holder 118. One of the two charging electrodes 117 is electrically connected to the positive terminal of the battery 116. The other charging electrode 117 is electrically connected to the negative terminal of the battery 116. The battery 116 is supplied with power from the charging device 30 (terminal 31 of the charging device 30) via the charging electrode 117.

[0025] The traveling unit 120 has traveling wheels 121 and auxiliary wheels 122. The traveling wheels 121 are respectively arranged at the four corners of the upper surface 110a of the main body unit 110. Each traveling wheel 121 is rotatably supported by the connecting unit 130 via a rotation shaft (not shown). This rotation shaft is arranged parallel or approximately parallel to the XY plane (horizontal plane). Therefore, the traveling wheels 121 are rotatable around the axis of the rotation shaft along the horizontal direction. Each traveling wheel 121 is rotationally driven by the driving force of the traveling drive unit 133. Furthermore, each traveling wheel 121 rolls on the traveling surfaces of the first track R1, the second track R2, and the partial track R3 of the lattice-shaped track R, causing the transport vehicle 10 to travel. Furthermore, each traveling wheel 121 is arranged to be rotatable in the θZ direction around a rotation axis AX1 along the Z direction. The traveling wheels 121 can change their traveling direction from the first direction D1 to the second direction D2 or from the second direction D2 to the first direction D1 by turning in the θZ direction. Note that the configuration is not limited to one in which all four traveling wheels 121 are rotationally driven by the driving force of the traveling drive unit 133, and it may be one in which only some of the four traveling wheels 121 are rotationally driven.

[0026] The auxiliary wheels 122 are arranged one in front of and one behind the running wheel 121 in the traveling direction. Like the running wheel 121, each of the auxiliary wheels 122 is rotatable around a rotation axis that is parallel or nearly parallel to the XY plane. The lower ends of the auxiliary wheels 122 are arranged higher than the lower ends of the running wheels 121. Therefore, when the running wheel 121 is running on the traveling surface, the auxiliary wheels 122 do not come into contact with the traveling surface. Furthermore, when the running wheel 121 passes through a gap, the auxiliary wheels 122 come into contact with the traveling surface, preventing the running wheel 121 from sinking. Note that the present invention is not limited to providing two auxiliary wheels 122 per running wheel 121. For example, one auxiliary wheel 122 may be provided per running wheel 121, or no auxiliary wheel 122 may be provided.

[0027] The coupling parts 130 couple the main body part 110 and the running part 120. The coupling parts 130 are provided at the four corner parts of the top surface 110a of the main body part 110. The main body part 110 is suspended by the coupling parts 130 and is disposed below the lattice track R. The coupling parts 130 have a support member 131 and a connection member 132. The support member 131 rotatably supports the rotation shaft of the running wheel 121 and the rotation shaft of the auxiliary wheel 122. The support member 131 maintains the relative positions of the running wheel 121 and the auxiliary wheel 122.

[0028] The connecting member 132 extends downward from the support member 131 and is connected to the upper surface 110a of the main body 110, thereby holding the main body 110. The connecting member 132 includes an internal transmission mechanism that transmits the driving force of the traveling drive unit 133 to the traveling wheels 121. The transmission mechanism may be configured to use a chain or a belt, or may be configured to use a gear train. The connecting member 132 is provided so as to be rotatable in the θZ direction around a pivot axis AX1. By rotating the connecting member 132 around the pivot axis AX1, the traveling wheels 121 can be rotated in the θZ direction.

[0029] The coupling unit 130 is provided with a travel drive unit 133 and a steering mechanism 134. The travel drive unit 133 is attached to the connection member 132. The travel drive unit 133 is a drive source that drives the travel wheels 121, and an electric motor or the like is used for example. The four travel wheels 121 are each driven by the travel drive unit 133 to serve as drive wheels. The four travel wheels 121 are controlled by the control unit 140 so that they rotate at the same or nearly the same speed.

[0030] The steering mechanism 134 rotates the connecting member 132 of the coupling part 130 about the rotation axis AX1, thereby turning the traveling wheels 121 in the θZ direction. By turning the traveling wheels 121 in the θZ direction, the traveling direction of the transport vehicle 10 can be changed from the first direction D1 to the second direction D2, or from the second direction D2 to the first direction D1.

[0031] The steering mechanism 134 includes a drive source 135, a pinion gear (not shown), and a rack 137. The drive source 135 is attached to a side of the traveling drive unit 133 away from the rotation axis AX1. The drive source 135 may be, for example, an electric motor. The pinion gear is attached to the underside of the drive source 135 and is driven to rotate in the θZ direction by the driving force generated by the drive source 135. The pinion gear is circular in plan view and has multiple teeth arranged circumferentially on its outer periphery. The rack 137 is fixed to the upper surface 110a of the main body 110. The racks 137 are provided at the four corners of the upper surface 110a of the main body 110, respectively, and are arranged in an arc shape centered on the rotation axis AX1 of the traveling wheel 121. The rack 137 has multiple teeth arranged circumferentially on its outer periphery that mesh with the teeth of the pinion gear.

[0032] The pinion gear and rack 137 are each arranged with multiple teeth meshing with each other. As the pinion gear rotates in the θZ direction, the pinion gear moves in a circumferential direction about the rotation axis AX1 so as to follow the outer periphery of the rack 137. As the pinion gear moves, the traveling drive unit 133 and the steering mechanism 134 rotate together with the pinion gear in the circumferential direction about the rotation axis AX1.

[0033] FIG. 5 is a diagram showing an example of transmission and reception of status information according to the embodiment. As shown in FIG. 5, the controller 20 transmits a request for status information to each of the guided vehicles 10 (e.g., guided vehicles 10A, 10B, 10C, and 10D) through periodic communication. As a result, each of the guided vehicles 10 transmits its own status information to the controller 20. Specifically, the guided vehicle 10A transmits its own status information S1 (status information S1A) to the controller 20. Similarly, the guided vehicle 10B transmits its own status information S2 (status information S2A) to the controller 20. Similarly, the guided vehicle 10C transmits its own status information S3 (status information S3A) to the controller 20. Similarly, the guided vehicle 10D transmits its own status information S4 (status information S4A) to the controller 20.

[0034] FIG. 6 is a flowchart illustrating an example of a process flow by a controller according to an embodiment. Note that FIG. 6 illustrates an example in which a system margin is confirmed prior to the execution of the first determination process and the second determination process. As illustrated in FIG. 6, the charging instruction unit 21 confirms the system margin (step S01). Specifically, the charging instruction unit 21 confirms whether at least one of the following conditions is satisfied: the ratio of available guided vehicles is equal to or greater than a predetermined ratio; the transport volume is less than a predetermined transport volume; and the utilization rate is less than a predetermined utilization rate. If there is a margin for the system margin (step S02: YES), the charging instruction unit 21 executes the first determination process (step S03). Specifically, if the charging instruction unit 21 determines that there is a margin by checking the system margin, it calculates the charging rates of all of the guided vehicles 10 on the lattice track R based on information about the charging rates included in the status information received from each guided vehicle 10.

[0035] Next, when the charging rate calculated by the first determination process is less than the first threshold (step S04: YES), the charge instructing unit 21 determines the guided vehicle 10 to be charged (step S05) and instructs the determined guided vehicle 10 to be charged to charge (step S06). Specifically, when the charge instructing unit 21 determines that the calculated charging rates of all of the multiple guided vehicles 10 are less than the first threshold, the charge instructing unit 21 determines at least one of the guided vehicles 10 to be charged and instructs the guided vehicle 10 determined to be the target of charging to start charging. In other words, when there is a margin in the system margin rate and the charging rate of the entire system is less than the first threshold, the controller 20 prompts at least one of the guided vehicles 10 to charge early. Note that, as described above, the charge instructing unit 21 may determine, as the target of charging, a guided vehicle 10 whose charging rate is less than the first threshold (at least one of the guided vehicles 10 whose charging rate is less than the first threshold) based on information about the charging rate included in the status information of each guided vehicle 10.

[0036] Furthermore, if there is no margin for the system margin rate (step S02: NO), the charging instructing unit 21 executes a second determination process (step S07). Specifically, if it is determined that there is no margin by checking the system margin rate, the charging instructing unit 21 determines whether the charging rate of each guided vehicle 10 is less than a second threshold value that is smaller than the first threshold value, based on information about the charging rate included in the status information received from each guided vehicle 10. Then, if the charging rate is less than the second threshold value based on the second determination process (step S08: YES), the charging instructing unit 21 instructs the guided vehicles 10 to charge (step S09). Specifically, if there is a guided vehicle 10 whose charging rate is less than the second threshold value based on the second determination process, the charging instructing unit 21 instructs the corresponding guided vehicle 10 to charge. On the other hand, if the charging rate is not less than the second threshold value based on the second determination process (step S08: NO), the charging instructing unit 21 ends the process. Specifically, if there is no transport vehicle 10 whose charging rate is less than the second threshold value in the second determination process, the charge instruction unit 21 terminates the process because there is no transport vehicle 10 that currently needs charging. In other words, if there is no margin in the system margin rate, the controller 20 prompts the transport vehicles 10 that are at a level requiring charging to charge, without prompting them to charge at a timing different from normal.

[0037] Furthermore, if the charging rate calculated by the first determination process is not less than the first threshold (step S04: NO), the charge instructing unit 21 executes the second determination process (step S07). Specifically, if the charge instructing unit 21 determines that the calculated charging rate of all of the multiple guided vehicles 10 is not less than the first threshold, the charge instructing unit 21 determines whether the charging rate of each guided vehicle 10 is less than a second threshold that is smaller than the first threshold, based on the information about the charging rate included in the status information received from each guided vehicle 10. That is, if there is a margin in the system margin rate and the charging rate of the entire system is not less than the first threshold, the controller 20 checks whether there is a guided vehicle 10 that needs to be charged. In other words, if the charging rate of the entire system is relatively high but there is a guided vehicle 10 that needs to be charged, the controller 20 prompts the corresponding guided vehicle 10 to charge.

[0038] 7 is a diagram illustrating another example of processing by the charging instruction unit according to the embodiment. In addition to what has been described in the above embodiment, the charging instruction unit 21 may instruct two or more transport vehicles to start charging at different times. Specifically, when instructing two or more transport vehicles to start charging, the charging instruction unit 21 may instruct the transport vehicles 10 to start charging in order, starting with the transport vehicle 10 closest to the charging device 30.

[0039] 7, when the charging rate calculated by the first determination process is less than the first threshold (step S04: YES), the charge instructing unit 21 determines the guided vehicle 10 closest to the charging device 30 as the one to be charged (step S21), and instructs the guided vehicle 10 determined to be the one to be charged to charge (step S22). Specifically, when the charge instructing unit 21 determines that the calculated charging rates of all of the multiple guided vehicles 10 are less than the first threshold, the charge instructing unit 21 determines the guided vehicle 10 closest to the charging device 30 as the one to be charged, based on information about the current position included in the status information of each guided vehicle 10. Thereafter, the charge instructing unit 21 instructs the guided vehicle 10 determined to be the one to be charged to charge.

[0040] Furthermore, if other guided vehicles 10 are also to be charged (step S23: YES), the charging instructing unit 21 executes the processing in step S21 again. On the other hand, if other guided vehicles 10 are not to be charged (step S23: NO), the charging instructing unit 21 terminates the processing. Specifically, after instructing the guided vehicle 10 determined as the target to be charged to charge, if other guided vehicles 10 are also to be charged, the charging instructing unit 21 determines the guided vehicle 10 closest to the charging device 30 as the target to be charged and instructs the guided vehicle 10 determined as the target to be charged to charge. Furthermore, after instructing the guided vehicle 10 determined as the target to be charged to charge, if other guided vehicles 10 are not to be charged, the charging instructing unit 21 terminates the processing.

[0041] Note that, when there is no available charging device 30, the controller 20 may issue a charging instruction to successive transport vehicles 10 after a certain time interval. In other words, the controller 20 issues a charging instruction to the transport vehicles 10 closest to the charging device 30 (in order from the transport vehicles 10 closest to the charging device 30) after a certain time interval, since it is undesirable to have multiple transport vehicles 10 headed for charging at the same time, as this would result in a situation where the vehicles have to wait for charging, thereby reducing transport efficiency. Furthermore, when a transport vehicle 10 with a charging rate less than the first threshold is to be charged, if multiple transport vehicles 10 are to be charged, the charge instruction unit 21 may issue a charging instruction to the transport vehicles 10 closest to the charging device 30 after a certain time interval, in order from the transport vehicles 10 closest to the charging device 30.

[0042] 8 is a diagram illustrating another example of processing by the charge instruction unit according to the embodiment. In addition to what has been described in the above embodiment, the charge instruction unit 21 may instruct two or more transport vehicles to start charging at different times. Specifically, when instructing two or more transport vehicles to start charging, the charge instruction unit 21 may instruct the transport vehicles 10 to start charging in order starting from the transport vehicle 10 with the lowest charging rate.

[0043] 8, when the charging rate calculated by the first determination process is less than the first threshold (step S04: YES), the charge instructing unit 21 determines the guided vehicle 10 with the lower charging rate as the one to be charged (step S31) and instructs the guided vehicle 10 determined to be the one to be charged to charge (step S32). Specifically, when the charge instructing unit 21 determines that the calculated charging rates of all of the multiple guided vehicles 10 are less than the first threshold, the charge instructing unit 21 determines the guided vehicle 10 with the lower charging rate as the one to be charged based on the charging rate included in the status information of each guided vehicle 10. Then, the charge instructing unit 21 instructs the guided vehicle 10 determined to be the one to be charged to charge.

[0044] Furthermore, if other guided vehicles 10 are also to be charged (step S33: YES), the charging instructing unit 21 executes the process in step S31 again. On the other hand, if other guided vehicles 10 are not to be charged (step S33: NO), the charging instructing unit 21 terminates the process. Specifically, after instructing the guided vehicle 10 determined as the target to be charged to charge, if other guided vehicles 10 are also to be charged, the charging instructing unit 21 determines the guided vehicle 10 with the lower charging rate as the target to be charged and instructs the guided vehicle 10 determined as the target to be charged to charge. Furthermore, after instructing the guided vehicle 10 determined as the target to be charged to charge, if other guided vehicles 10 are not to be charged, the charging instructing unit 21 terminates the process. Note that the controller 20 may issue charging instructions to successive guided vehicles 10 after a certain time has elapsed if there is no available charging device 30. That is, since it is undesirable to have multiple transport vehicles 10 heading for charging at the same time, which would result in a situation where they have to wait for charging and reduce transport efficiency, the controller 20 instructs the transport vehicles 10 with lower charging rates to charge (in order from the transport vehicle 10 with the lowest charging rate) after a certain time interval. Also, when the transport vehicles 10 with charging rates less than the first threshold are to be charged, if multiple transport vehicles 10 are to be charged, the charge instruction unit 21 may instruct the transport vehicles 10 with the lowest charging rates to be charged after a certain time interval, in order.

[0045] FIG. 9 is a diagram illustrating an example of the charging instruction process according to the embodiment. In FIG. 9, the explanation is based on the premise that three charging devices 30 are installed, the battery 116 decreases by 1 percent per minute, the travel time for charging is 1 minute, and the charging time is 4 minutes. Also, in FIG. 9, an example is given in which the first threshold (corresponding to the charging rate of the entire system) is 30 percent, and the second threshold (corresponding to the charging rate of each guided vehicle 10) is 20 percent. In addition, in FIG. 9, the effective guided vehicle ratio is used as an example of the system margin rate, and the threshold is 60 percent.

[0046] As shown in FIG. 9 , the controller 20 calculates the overall charge rate of multiple guided vehicles 10 every minute, and recognizes that the overall charge rate has reached 29.2 percent after four minutes have elapsed, thereby falling below the first threshold of 30 percent. Here, the controller 20 designates guided vehicles V1, V2, V3, and V4 as targets for charging instructions. The controller 20 then issues a charging instruction to any of the guided vehicles 10, the guided vehicle 10 closest to the charging device 30, or the guided vehicle 10 with the lowest charging rate among the guided vehicles V1, V2, V3, and V4. In the example shown in FIG. 9 , since the charging rates of the guided vehicles V1, V2, V3, and V4 are the same, it is sufficient to instruct any of the guided vehicles 10 or the guided vehicle 10 closest to the charging device 30 to charge. For example, the controller 20 instructs the guided vehicle V1 to charge. Furthermore, since there is available charge in the charging device 30 and there is also a margin in the system margin rate (here, the effective guided vehicle ratio), the controller 20 instructs the guided vehicle V2 to charge. The charging instructions to the guided vehicles V1 and V2 are issued at different times, but may be issued at the same time. In this case, if the controller 20 instructs either the guided vehicles V3 or V4 to charge, the system margin rate (here, the ratio of effective guided vehicles) will fall below the threshold value of 60 percent, so the controller 20 does not instruct the guided vehicles V3 and V4 to charge.

[0047] Thereafter, at time "11" minutes elapsed, the controller 20 recognizes that charging of the guided vehicles V1 and V2 has been completed. At this time, the controller 20 does not instruct the guided vehicles V3 and V4 to charge because there is a margin in the system margin (here, the effective guided vehicle ratio), the charging rate of the entire system is not less than the first threshold "30" percent, and the individual charging rates are not less than the second threshold "20" percent. Furthermore, at time "12" minutes elapsed, the controller 20 recognizes that the individual charging rates of the guided vehicles V1 and V2 have become less than the second threshold "20" percent. Then, the controller 20 instructs the guided vehicles V3 and V4 to charge. Thereafter, at time "18" minutes elapsed, the controller 20 recognizes that charging of the guided vehicles V3 and V4 has been completed. Furthermore, at the time "19" minutes have elapsed, the controller 20 determines that there is a margin in the system margin and the charging rate of the entire system is not below the first threshold, but the individual charging rate of the transport vehicle V5 may be below "20" percent, and may instruct the transport vehicle V5 to charge.

[0048] FIG. 10 is a diagram showing an example of a charging instruction process according to the prior art. As shown in FIG. 10, in the prior art, when "12" minutes have passed, the individual charging rates of guided vehicles V1, V2, V3, and V4 fall below a threshold (the second threshold in this embodiment), and charging becomes necessary. However, since there are three charging devices, guided vehicles V1, V2, and V3 are directed to the charging devices, and guided vehicle V4 enters a state of waiting for charging. At this time, the number of guided vehicles that can operate in the entire system is "1" (guided vehicle V5), and transportation efficiency decreases.

[0049] As described above, the guided vehicle system 100 according to the embodiment instructs one of the guided vehicles 10 to start charging when the charging rates of all the guided vehicles 10 are below a first threshold, and instructs the guided vehicles 10 whose charging rates are below a second threshold, which is lower than the first threshold, to start charging. This prevents multiple guided vehicles 10 from being instructed to start charging at the same time, thereby preventing a decrease in the transport efficiency of the entire system. Furthermore, the guided vehicle system 100 according to the embodiment instructs the guided vehicles 10 to charge while taking the system margin rate into consideration, thereby preventing a situation in which there is no guided vehicle 10 to which a transport command can be assigned. Furthermore, the guided vehicle system 100 according to the embodiment periodically checks the system margin rate and instructs the guided vehicles 10 to charge, thereby preventing the occurrence of a guided vehicle 10 that is unable to execute a transport command due to a decrease in its charging rate. Furthermore, the guided vehicle system 100 according to the embodiment calculates the system margin rate using various information related to transport efficiency, thereby effectively preventing a decrease in the transport efficiency of the entire system. Furthermore, according to the guided vehicle system 100 of the embodiment, since multiple guided vehicles 10 are not simultaneously directed to charge, a decrease in the transport efficiency of the entire system can be suppressed. Furthermore, according to the guided vehicle system 100 of the embodiment, since the guided vehicle 10 is instructed to start charging in order starting with the guided vehicle 10 closest to the charging device 30, charging efficiency can be improved when multiple guided vehicles 10 require charging. Furthermore, according to the guided vehicle system 100 of the embodiment, since the guided vehicle 10 is instructed to start charging in order starting with the guided vehicle 10 with the lowest charging rate, an increase in the number of guided vehicles 10 that cannot execute a transport command due to a decrease in charging rate can be suppressed. Furthermore, according to the guided vehicle system 100 of the embodiment, status information is acquired through periodic communication between the multiple guided vehicles 10 and the controller 20, so that a guided vehicle 10 suitable for instructing charging can be identified. Furthermore, according to the guided vehicle system 100 of the embodiment, multiple guided vehicles 10 can move in the first direction D1 or the second direction D2 along the lattice track R, and a charging device 30 is provided corresponding to one square of the lattice track R. Therefore, the guided vehicle system 100 can be applied to a guided vehicle system 100 arranged on the lattice track R.

[0050] In addition, the following supplementary notes are disclosed in relation to the above-described embodiment. (Supplementary Note 1) A transport vehicle system including a plurality of transport vehicles for transporting articles, a controller for allocating a transport command to any of the plurality of transport vehicles, and a charging device located on a route along which the plurality of transport vehicles can travel and for supplying power to the transport vehicles, the controller includes a charge instruction unit that instructs each transport vehicle to start charging; The charging instruction unit performing a first determination process to determine whether the charging rates of all of the plurality of transporting vehicles are less than a first threshold value, and when it is determined that the charging rates of all of the plurality of transporting vehicles are less than the first threshold value, instructing at least one of the transporting vehicles to start charging; A transport vehicle system that performs a second determination process to determine whether the charging rate of each transport vehicle is less than a second threshold value that is smaller than the first threshold value, and instructs the transport vehicle to start charging if it is determined that the charging rate of the transport vehicle is less than the second threshold value. (Supplementary Note 2) The charging instruction unit confirming, at a predetermined timing, a system margin rate indicating a degree of margin for the entire plurality of transport vehicles with respect to the processing of the transport command; instructing at least one of the transporting vehicles to start charging when it is determined that the degree of margin indicated by the system margin rate is equal to or greater than a predetermined value and that the charging rates of all of the plurality of transporting vehicles are less than the first threshold value; A transport vehicle system as described in Appendix 1, which instructs the transport vehicle to start charging when it is determined that the degree of margin indicated by the system margin rate is equal to or greater than the predetermined value and the charging rate of the transport vehicle is less than the second threshold value. (Supplementary Note 3) The transport vehicle system according to Supplementary Note 2, wherein the charge instruction unit periodically checks the system margin rate as the predetermined timing. (Appendix 4) A transport vehicle system as described in Appendix 2 or Appendix 3, wherein the charging instruction unit checks whether the system margin rate satisfies at least one of the following: an effective transport vehicle ratio, which indicates the ratio of waiting transport vehicles to the entire plurality of transport vehicles, is a predetermined ratio or more; the transport volume of the entire plurality of transport vehicles is less than a predetermined transport volume; and the operating rate of the entire plurality of transport vehicles is less than a predetermined operating rate. (Supplementary Note 5) The transport vehicle system according to any one of Supplementary Note 1 to Supplementary Note 4, wherein the charging instruction unit issues instructions to start charging to two or more of the transport vehicles at different times. (Supplementary Note 6) The transported vehicle system according to Supplementary Note 5, wherein the charging instruction unit instructs the transported vehicles to start charging in order starting from the transported vehicle closest to the charging device. (Supplementary Note 7) The transport vehicle system according to Supplementary Note 5, wherein the charge instruction unit instructs the transport vehicles to start charging in order starting from the transport vehicle with the lowest charging rate. (Supplementary Note 8) The transport vehicle system according to any one of Supplementary Note 1 to Supplementary Note 7, wherein the controller acquires status information of the plurality of transport vehicles by periodically communicating with the plurality of transport vehicles. (Supplementary Note 9) The plurality of transport vehicles are movable in a first direction or a second direction along a lattice-shaped track extending in a first direction and a second direction intersecting the first direction, 9. The transport vehicle system according to any one of claims 1 to 8, wherein the charging device is provided corresponding to one square of the grid-like track. (Supplementary Note 10) A method for controlling a transport vehicle in a transport vehicle system including a plurality of transport vehicles for transporting articles, a controller for allocating a transport command to any of the plurality of transport vehicles, and a charging device located on a route along which the plurality of transport vehicles can travel and for supplying power to the transport vehicles, the method comprising: The controller performing a first determination process for determining whether the charging rates of all of the plurality of transporting vehicles are less than a first threshold value, and when it is determined that the charging rates of all of the plurality of transporting vehicles are less than the first threshold value, instructing at least any of the transporting vehicles to start charging; A method for controlling a transport vehicle, comprising: performing a second determination process to determine whether the charging rate of each transport vehicle is less than a second threshold value that is smaller than the first threshold value; and instructing the transport vehicle to start charging when it is determined that the charging rate of the transport vehicle is less than the second threshold value.

[0051] Although the embodiments of the present invention have been described above, the technical scope of the present invention is not limited to the above-described embodiments. It will be apparent to those skilled in the art that various modifications or improvements can be made to the above-described embodiments. Furthermore, forms incorporating such modifications or improvements are also included within the technical scope of the present invention. One or more of the requirements described in the above-described embodiments may be omitted. Furthermore, the requirements described in the above-described embodiments may be combined as appropriate. Furthermore, to the extent permitted by law, the disclosures of all documents cited in the above-described embodiments are incorporated by reference into this description.

[0052] The technical scope of the present invention is not limited to the aspects described in the above-mentioned embodiments. One or more of the requirements described in the above-mentioned embodiments may be omitted. The requirements described in the above-mentioned embodiments may be combined as appropriate. Furthermore, to the extent permitted by law, the disclosures of Japanese Patent Application No. 2022-078653 and all documents cited in the above-mentioned embodiments are incorporated by reference and are included as part of the description of this text. [Explanation of symbols]

[0053] 10. Transport vehicle 20 Controller 21...Charging instruction section 30...Charging device 100...Transport vehicle system

Claims

1. A transport vehicle system including a plurality of transport vehicles that transport articles, a controller that assigns a transport command to any one of the plurality of transport vehicles, and a charging device that is located on a route along which the plurality of transport vehicles can travel and that supplies power to the transport vehicles, the controller includes a charge instruction unit that instructs each transport vehicle to start charging; The charging instruction unit performing a first determination process to determine whether the charging rates of all of the plurality of transporting vehicles are less than a first threshold value, and when it is determined that the charging rates of all of the plurality of transporting vehicles are less than the first threshold value, instructing at least one of the transporting vehicles to start charging; A transport vehicle system performs a second determination process to determine whether the charging rate of each transport vehicle is less than a second threshold value that is smaller than the first threshold value, and if it is determined that the charging rate of a transport vehicle is less than the second threshold value, instructs the transport vehicle to start charging.

2. The charging instruction unit confirming, at a predetermined timing, a system margin rate indicating a degree of margin for the entire plurality of transport vehicles with respect to the processing of the transport command; instructing at least one of the transporting vehicles to start charging when it is determined that the degree of margin indicated by the system margin rate is equal to or greater than a predetermined value and that the charging rates of all of the plurality of transporting vehicles are less than the first threshold value; 2. The transport vehicle system according to claim 1, wherein when it is determined that the degree of margin indicated by the system margin rate is equal to or greater than the predetermined value and that the charging rate of the transport vehicle is less than the second threshold value, the transport vehicle is instructed to start charging.

3. The guided vehicle system according to claim 2 , wherein the charge instruction unit periodically checks the system margin rate as the predetermined timing.

4. The transport vehicle system described in claim 2 or 3, wherein the charging instruction unit checks whether the system margin rate satisfies at least one of the following: an effective transport vehicle ratio, which indicates the ratio of waiting transport vehicles to the total number of transport vehicles, is a predetermined ratio or more; the total transport volume of the total number of transport vehicles is less than a predetermined transport volume; and the operating rate of the total number of transport vehicles is less than a predetermined operating rate.

5. The transport vehicle system according to claim 1 , wherein the charge instruction unit issues instructions to start charging to two or more of the transport vehicles at different times.

6. The guided vehicle system according to claim 5 , wherein the charging instruction unit instructs the start of charging in order from the guided vehicle closest to the charging device.

7. The guided vehicle system according to claim 5 , wherein the charge instruction unit instructs the guided vehicle to start charging in order of the lowest charge rate.

8. The guided vehicle system according to claim 1 , wherein the controller acquires status information of the plurality of guided vehicles through periodic communication with the plurality of guided vehicles.

9. the plurality of transport vehicles are movable in a first direction or a second direction along a lattice-shaped track extending in a first direction and a second direction intersecting the first direction, The guided vehicle system according to claim 1 , wherein the charging device is provided in correspondence with one square of the grid-like track.

10. A method for controlling a transport vehicle in a transport vehicle system including a plurality of transport vehicles that transport articles, a controller that assigns a transport command to any of the plurality of transport vehicles, and a charging device that is located on a route along which the plurality of transport vehicles can travel and that supplies power to the transport vehicles, comprising: The controller performing a first determination process for determining whether the charging rates of all of the plurality of transporting vehicles are less than a first threshold value, and when it is determined that the charging rates of all of the plurality of transporting vehicles are less than the first threshold value, instructing at least any of the transporting vehicles to start charging; A method for controlling a transport vehicle, comprising: performing a second determination process to determine whether the charging rate of each transport vehicle is less than a second threshold value that is smaller than the first threshold value; and instructing the transport vehicle to start charging if it is determined that the charging rate of the transport vehicle is less than the second threshold value.

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