Transport vehicle system
Patent Information
- Application Number
- JP2024549775
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-07-18
- Filing Date
- 2023-07-18
- Publication Date
- 2025-05-22
- Estimated Expiration
- 2043-07-18
AI Technical Summary
In guided vehicle systems, the waiting time of rear vehicles due to the transfer operations of front vehicles reduces transport efficiency, as they often have to wait until the front vehicle completes its transfer operation at a station before they can proceed to their destination, leading to inefficiencies and potential bottlenecks.
Implementing a control unit that allocates transport commands to optimize vehicle routes by exchanging destinations between first and second vehicles if the second vehicle is upstream, allowing them to perform transfer operations simultaneously and reducing waiting times, thereby improving overall system efficiency.
This approach significantly reduces waiting times for rear vehicles, shortens the vehicle queue, and enhances transport efficiency by allowing multiple vehicles to transfer to stations almost simultaneously, thus improving the overall performance of the guided vehicle system.
Abstract
Description
Transport vehicle system
[0001] The present invention relates to a guided vehicle system.
[0002] A known guided vehicle system (see, for example, Patent Document 1) includes a plurality of guided vehicles traveling along a track, carrying containers such as front-opening unified pods (FOUPs) or reticle pods containing semiconductor wafers, glass substrates, or other objects. The guided vehicle system includes a plurality of guided vehicles traveling along a track with a unidirectional travel direction. Each of the plurality of guided vehicles is configured to move based on a transfer command assigned by a controller. The transfer command includes destination information regarding a station for which a loading request is made. In such a guided vehicle system, each time a transfer request is made at a station, a transfer command including the station as destination information is generally assigned to a guided vehicle that can arrive at the station earliest.
[0003] International Publication No. WO2017 / 029873
[0004] However, in the above-described general control, as shown in state 5A of FIG. 5 , if a transport command for the first station STa as a destination is assigned to the first transport vehicle 105A traveling on the track 111, and a transport command for the second station STb located downstream of the first station STa is assigned to the second transport vehicle 105B as a destination, and the first transport vehicle 105A ends up traveling upstream of the second transport vehicle 105B, the following problem may occur. That is, as shown in state 5B of FIG. 5 , while the first transport vehicle 105A performs a transfer operation to receive an item from the first station STa, the second transport vehicle 105B must wait behind (upstream of) the first transport vehicle 105A until the first transport vehicle 105A's transfer operation is completed. After this waiting period, the second transport vehicle 105B performs a transfer operation at the second station STb as a destination, as shown in state 5C of FIG. 5 . This waiting time of the rear transport vehicle (second transport vehicle 105B) reduces the transport efficiency of the transport vehicle system.
[0005] Therefore, an object of one aspect of the present invention is to provide a transport vehicle system that can improve the transport efficiency in the transport vehicle system by reducing the waiting time of a rear transport vehicle due to the transfer operation of a front transport vehicle.
[0006] A transport vehicle system according to one aspect of the present invention comprises a plurality of transport vehicles that travel in one direction along a predetermined route and transport items, a plurality of stations arranged along the route that are the source of requests to load items, and a control unit that, each time a request to load an item is made, assigns a transport command to the transport vehicle that can arrive at the station for which the loading request was made the earliest, with the transport vehicle having the loading request as its destination.The control unit performs a swapping determination to determine whether a second transport vehicle, another than the first transport vehicle, is assigned a transport command with the second station, a station located downstream of the first station, as its destination, upstream of the first transport vehicle, one of the plurality of stations, to which the transport command with the first station, one of the plurality of stations, is assigned.If the control unit determines that the second transport vehicle is present upstream of the first transport vehicle, it performs swapping control to swap the destinations of the transport commands assigned before the swapping determination between the first transport vehicle and the second transport vehicle.
[0007] In a guided vehicle system with this configuration, switching the transport command reduces the time that would occur if the transport command were not switched, i.e., the time that the second guided vehicle waits behind (upstream of) the first station while the first guided vehicle is performing a transfer operation to receive an item from the first station. Furthermore, if there is another guided vehicle behind the rear guided vehicle, the number of times that the second guided vehicle waits is reduced by one, shortening the waiting time and thereby shortening the length of the waiting vehicle queue, thereby further improving the transport efficiency of the entire guided vehicle system. For example, if there is a branch point upstream of the station, shortening the waiting queue reduces the possibility of the branching vehicle being caught in the queue. As a result, the transport efficiency of the guided vehicle system can be improved.
[0008] In a transport vehicle system according to one aspect of the present invention, the control unit may determine whether a second transport vehicle is present upstream of the first transport vehicle and will wait until the first transport vehicle completes its work when the first transport vehicle executes a transport command specifying the first station as its destination. This configuration reliably eliminates the waiting time for the second transport vehicle when the first transport vehicle located ahead receives an item from the station. Furthermore, the second transport vehicle executes the transport command specifying the first station as its destination without a significant delay from the originally scheduled time when the first transport vehicle was to complete its work.
[0009] In a transport vehicle system according to one aspect of the present invention, the control unit may determine whether a second transport vehicle is available to begin a transfer operation at the first station while the first transport vehicle is performing a transfer operation at the second station when the destinations of the transport commands assigned before the transfer determination are swapped. This configuration allows the first transport vehicle and the second transport vehicle to perform transfers to each station almost simultaneously. This improves the transport efficiency of the entire system.
[0010] In a guided vehicle system according to one aspect of the present invention, when the control unit determines that the second guided vehicle is located upstream of the first guided vehicle through the replacement determination, the control unit may execute replacement control even if another guided vehicle is located between the first and second guided vehicles. In this configuration, the replacement control can be executed even if the second guided vehicle is not located immediately behind the first guided vehicle, so that the search range for guided vehicles to be replaced can be widened, making it easier to find the guided vehicle to be replaced.
[0011] In a guided vehicle system according to one aspect of the present invention, the control unit executes a swap determination when a first guided vehicle assigned a transport command with the first station as its destination reaches a predetermined position upstream of the first station, and the predetermined position may be a deceleration start position for the first guided vehicle to stop at the first station. In this configuration, if there is no second guided vehicle to be swapped behind the first guided vehicle, the first guided vehicle can be stopped at the first station. Furthermore, the execution of the determination control can be delayed until the very last possible time for the first guided vehicle to stop at the first station, making it easier to find the second guided vehicle. Furthermore, the burden on the control unit can be reduced compared to when constantly determining whether or not a second guided vehicle is present.
[0012] According to one aspect of the present invention, the waiting time of a rear transport vehicle due to the transfer operation of a front transport vehicle can be reduced, thereby improving the transport efficiency in a transport vehicle system.
[0013] Fig. 1 is a configuration diagram showing the configuration of a guided vehicle system according to one embodiment. Fig. 2 is a functional block diagram showing the functional configuration of the guided vehicle system. Fig. 3 is a diagram for explaining replacement determination and replacement control in the guided vehicle system. Fig. 4 is a diagram for explaining replacement determination and replacement control in the guided vehicle system. Fig. 5 is a diagram for explaining problems that arise in conventional guided vehicle systems.
[0014] An embodiment will be described below with reference to the drawings. In the description of the drawings, identical elements are designated by the same reference numerals, and duplicated descriptions will be omitted. The dimensional ratios of the drawings do not necessarily match those in the description. Furthermore, when describing an embodiment, upstream and downstream refer to upstream and downstream in the travel direction (the direction of the arrow shown on the track 11 in FIG. 1: one direction) of a preset overhead transport vehicle (transport vehicle) 5 (hereinafter simply referred to as "transport vehicle 5").
[0015] The guided vehicle system 1 is a system for transporting FOUPs using a guided vehicle 5 that can move along a track 11. The guided vehicle 5 is an unmanned guided vehicle, such as a ceiling guided vehicle or a track-guided vehicle. Here, the guided vehicle system 1 will be described as an example in which the guided vehicle 5 travels along a one-way track 11 installed on the ceiling or the like of a building such as a factory. As shown in FIG. 1 , the guided vehicle system 1 mainly includes the track 11, a plurality of stations ST, a plurality of guided vehicles 5, and a guided vehicle controller (control unit) 3.
[0016] The track 11 is a member on which the transport vehicles 5 travel, and is suspended from the ceiling. Fig. 1 shows an example of a portion of the layout of the track 11 in this embodiment. The track 11 in this embodiment is set up so that the transport vehicles 5 travel in one direction, in the direction of the arrow shown in Fig. 1. The track 11 is provided with a branch point BP where the track 11 branches off and a junction point CP where the track 11 merges.
[0017] The stations ST are provided along the track 11 so as to face the track 11. In this embodiment, a plurality of stations ST are provided. The stations ST are locations where FOUPs are transferred to and from the transport vehicles 5. For example, examples of stations ST in a semiconductor processing factory include load ports that transfer FOUPs (items) between semiconductor processing equipment and the transport vehicles 5, and buffers where the transport vehicles 5 can temporarily store FOUPs. The stations ST are the sources of requests to load FOUPs.
[0018] As shown in Fig. 2, the transport vehicle controller 3 includes an input unit 31, a display unit 32, a communication unit 33, and a transport vehicle control unit 40. The input unit 31 is, for example, a keyboard, a mouse, or the like, and is a unit through which the user inputs various operations and various setting values. In this embodiment, information regarding the predetermined position P, which will be described in detail later, is input and set from the input unit 31. The display unit 32 is, for example, a liquid crystal display, or the like, and is a unit that displays various setting screens and input screens for input via the input unit 31, or the like. The input unit 31 and the display unit 32 do not need to be provided integrally with the transport vehicle controller 3, and can be replaced by terminal devices that can communicate with each other.
[0019] The communication unit 33 is a part that communicates with other devices, and for example, transmits a transport command to the transport vehicle 5 and receives information (position data) related to the current position of the transport vehicle 5 via a wireless communication network. The communication unit 33 also receives a transport instruction including information about the destination station ST from a higher-level controller via a LAN (Local Area Network), for example. That is, the higher-level controller transmits information related to the station ST for which a transport request has been made to the transport vehicle controller 3.
[0020] The guided vehicle control unit 40 is a part that executes various control processes in the guided vehicle system 1, which will be described in detail later, and is composed of, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). As shown in Fig. 2, the guided vehicle control unit 40 can be configured as software in which a program stored in the ROM is loaded onto the RAM and executed by the CPU. Note that the guided vehicle control unit 40 may also be configured as hardware such as an electronic circuit.
[0021] The transport vehicle control unit 40 assigns a transport command to a transport vehicle 5 based on information about the station ST for which a loading request has been made, transmitted from, for example, a higher-level controller (not shown). More specifically, each time a request to load a FOUP is made, the transport vehicle control unit 40 assigns a transport command to the transport vehicle 5 that can arrive at the station ST for which a loading request has been made the earliest and that has not been assigned any other transport command (including transport commands other than loading requests), with the destination being the station ST for which a loading request has been made. In addition, the transport vehicle controller 3 grasps the position of the transport vehicle 5 based on position information (described in detail below) transmitted periodically or continuously from each transport vehicle 5. Unless otherwise specified, when simply referred to as a "transport command" hereinafter, it refers to a transport command with the station ST for which a loading request has been made as the destination.
[0022] The guided vehicle control unit 40 executes a replacement determination and a replacement control as shown in state 3A in FIG. 3 . When a first guided vehicle 5A, one of the multiple guided vehicles 5, assigned a transport command with a first station STa, one of the multiple stations ST, as its destination, reaches a predetermined position P upstream of the first station STa, the replacement determination determines whether a second guided vehicle 5B, another guided vehicle 5 assigned a transport command with a second station STb, a station ST located downstream of the first station STa, as its destination, is present upstream of the first guided vehicle 5A. Note that the "a" in the guided vehicle 5 shown in FIGS. 3 to 5 indicates that the first station STa is assigned as its destination, and the "b" in the guided vehicle 5 indicates that the second station STb is assigned as its destination.
[0023] Here, the predetermined position P is a position that is a distance D away from the first station STa on the upstream side. More specifically, the predetermined position P is the position where the first transport vehicle 5A starts deceleration when stopping at the first station STa. In other words, the first transport vehicle 5A can stop at the first station STa if it starts deceleration from the predetermined position P.
[0024] The swap control is a control in which, when it is determined that the second transport vehicle 5B is present upstream of the first transport vehicle 5A, the destinations of the transport commands assigned before the swap determination are swapped between the first transport vehicle 5A and the second transport vehicle 5B. For example, as shown in state 3A in FIG. 3 , when a transport command with the first station STa as the destination is assigned to the first transport vehicle 5A and a transport command with the second station STb as the destination is assigned to the second transport vehicle 5B, if the swap control is executed, the transport command with the second station STb as the destination is reassigned to the first transport vehicle 5A, and the transport command with the first station STa as the destination is reassigned to the second transport vehicle 5B, as shown in state 3B in FIG.
[0025] The replacement determination by the transport vehicle control unit 40 determines whether, in state 3A shown in FIG. 3 , there is a second transport vehicle 5B that can reach the first station STa by the time the first transport vehicle 5A completes the transport command specifying the first station STa as its destination. In other words, the replacement determination determines whether there is a second transport vehicle 5B that will wait upstream of the first transport vehicle 5A until the first transport vehicle 5A completes its work when the first transport vehicle 5A executes the transport command specifying the first station STa as its destination. If the transport vehicle control unit 40 determines that such a second transport vehicle 5B exists, it executes the replacement control described above. If it determines that the second transport vehicle 5B does not exist, it does not execute the replacement control described above.
[0026] In addition, the replacement judgment by the transport vehicle control unit 40 may determine whether there is a second transport vehicle 5B that can begin a transfer operation at the first station STa while the first transport vehicle 5A is performing a transfer operation at the second station STb when the destinations of the transport commands assigned before the replacement judgment are swapped.
[0027] In this determination, when the above-described replacement control is executed, as shown in state 4B in FIG. 4, it is possible to overlap a portion of the time during which the first transport vehicle 5A is performing the transfer operation at the second station STb with a portion of the time during which the second transport vehicle 5B is performing the transfer operation at the second station STb. This eliminates the waiting time when the first transport vehicle 5A, which is located in front of the second transport vehicle 5B, receives a FOUP from the station STb. Note that the time during which the first transport vehicle 5A is performing the transfer operation at the second station STb and the time during which the second transport vehicle 5B is performing the transfer operation at the second station STb may completely coincide.
[0028] When the transport vehicle control unit 40 determines that the second transport vehicle 5B is present upstream of the first transport vehicle 5A through the above-described replacement determination, it executes replacement control even when there are other transport vehicles 5 (two in this embodiment) between the first transport vehicle 5A and the second transport vehicle 5B, as in state 3A shown in Fig. 3. The other transport vehicles 5 here refer to, for example, transport vehicles to which no transport command is assigned, transport vehicles to which transport commands to a station other than the station (second station STb) that is the target of the replacement determination, transport vehicles that are not holding a FOUP, etc.
[0029] The transport vehicle 5 is configured to be able to transfer FOUPs. In addition to a mechanism for traveling along the track 11 and a known mechanism for transferring FOUPs, the transport vehicle 5 also includes a position acquisition unit 51 and a travel control unit 53, as shown in FIG.
[0030] The position acquisition unit 51 is a part that acquires position information of the vehicle on the track 11. The position acquisition unit 51 may be composed of, for example, a reading unit that reads a barcode or the like that is affixed to the track 11 and displays position information, an encoder, etc. The position acquisition unit 51 transmits, as position information, to the guided vehicle controller 3, point information obtained by the reading unit and the distance traveled since passing the point, which is obtained from the encoder. The information acquired by the position acquisition unit 51 is transmitted to the guided vehicle controller 3 in response to periodic or continuous inquiries from the guided vehicle controller 3.
[0031] The travel control unit 53 is a part that controls the travel of the transport vehicle 5, and is an electronic control unit including, for example, a CPU, ROM, RAM, etc. The travel control unit 53 controls the travel of the transport vehicle 5 based on a transport command sent from the transport vehicle controller 3. The transport command sent from a higher-level controller (not shown) contains information about a destination station ST that has a loading request. The travel control unit 53 controls each mechanism to move to the destination station ST that has a loading request and is included in the transport command, and to receive the FOUP.
[0032] The transport command transmitted from the transport vehicle controller 3 may include information regarding the station ST to which the FOUP is to be transported. The travel control unit 53 controls each mechanism to move the FOUP to the station ST to which the FOUP is to be transported.
[0033] Next, the operation of the guided vehicle system 1 when the above-described replacement determination and replacement control are executed will be described.
[0034] As shown in state 3A of FIG. 3 , the transport vehicle controller 3 (transport vehicle control unit 40) executes the swapping determination when a first transport vehicle 5A assigned a transport command with a destination of the first station STa, which has a loading request, reaches the predetermined position P upstream of the first station STa. Here, if the transport vehicle controller 3 determines that a second transport vehicle 5B assigned a transport command with a destination of the second station STb is located upstream of the first transport vehicle 5A assigned a transport command with a destination of the first station STa, the transport vehicle controller 3 swaps the destinations of the transport commands assigned before the swapping determination between the first transport vehicle 5A and the second transport vehicle 5B, as shown in state 3B of FIG. 3 . That is, the transport vehicle controller 3 reassigns a transport command with a destination of the second station STb to the first transport vehicle 5A, and reassigns a transport command with a destination of the first station STa to the second transport vehicle 5B.
[0035] The first transport vehicle 5A, which has been reassigned a transport command with the second station STb as its destination, passes through the first station STa and stops at the second station STb, as shown in states 4A and 4B in FIG. 4 . The first transport vehicle 5A performs a transfer operation to receive a FOUP from the second station STb. The second transport vehicle 5B, which has been reassigned a transport command with the first station STa as its destination, stops at the first station STa. The second transport vehicle 5B performs a transfer operation to receive a FOUP from the first station STa.
[0036] In addition, in state 3A of Figure 3, if the transport vehicle controller 3 determines that there is no second transport vehicle 5B assigned a transport command with the second station STb as its destination upstream of the first transport vehicle 5A assigned a transport command with the first station STa as its destination, the first transport vehicle 5A stops at the first station STa based on the transport command and performs a transfer operation to receive the FOUP from the first station STa.
[0037] The effects of the transport vehicle system 1 of the above embodiment will be described. In the transport vehicle system 1 of the above embodiment, by switching the transport command between the first transport vehicle 5A and the second transport vehicle 5B, the waiting time of the second transport vehicle 5B that would occur if the above-mentioned replacement control were not executed (i.e., the time the second transport vehicle 5B waits behind the first station STa while the first transport vehicle 5A performs a transfer operation to receive a FOUP from the first station STa) can be reduced. Furthermore, if there is another transport vehicle 5 behind the second transport vehicle 5B, the number of waiting times of that transport vehicle 5 is reduced by one, further improving the transport efficiency of the entire transport vehicle system 1. As a result, the transport efficiency of the transport vehicle system 1 can be improved.
[0038] In the transport vehicle system 1 of the above embodiment, the transport vehicle control unit 40 performs a replacement determination by determining whether or not there is a second transport vehicle 5B that will wait upstream of the first transport vehicle 5A until the first transport vehicle 5A completes its work when the first transport vehicle 5A executes a transport command specifying the first station STa as its destination. This eliminates the waiting time during the transfer operation when the first transport vehicle 5A, which is located ahead of the second transport vehicle 5B, receives a FOUP from station ST.
[0039] In the transport vehicle system 1 of the above embodiment, when the transport vehicle control unit 40 determines through the replacement determination that the second transport vehicle 5B is located upstream of the first transport vehicle 5A, it executes the replacement control even if another transport vehicle 5 is located between the first transport vehicle 5A and the second transport vehicle 5B. This makes it possible to execute the replacement control even if the second transport vehicle 5B is not located immediately behind the first transport vehicle 5A, thereby widening the search range for the transport vehicle 5 to be replaced and making it easier to find the transport vehicle 5 to be replaced.
[0040] In the transport vehicle system 1 of the above embodiment, the predetermined position P is set to be the deceleration start position when the first transport vehicle 5A stops at the first station STa. As a result, if there is no second transport vehicle 5B to be replaced behind the first transport vehicle 5A, the first transport vehicle 5A can be stopped at the first station STa as is. Furthermore, since the execution time of the determination control can be delayed until the very last possible time for the first transport vehicle 5A to stop at the first station STa, it becomes easier to find the second transport vehicle 5B. Furthermore, the processing load on the transport vehicle control unit 40 can be reduced compared to when the presence or absence of the second transport vehicle 5B is constantly determined.
[0041] Although one embodiment has been described above, one aspect of the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the invention.
[0042] In the above embodiment, the second transport vehicle 5B is arranged behind the first transport vehicle 5A as an example, but this is not limiting. For example, if the junction point CP is located upstream (rear) of the first transport vehicle 5A, the transport vehicle control unit 40 searches all tracks 11 upstream of the junction point CP to determine whether there is a transport vehicle 5 that will become the second transport vehicle 5B.
[0043] 3 and 4, which illustrate the above embodiment and the above modified example, the track 11 leading to the first station STa does not have a branch point BP or the like, but this is not limited to this. There may be a junction point CP before or after the predetermined position P, or there may be a branch point BP not shown.
[0044] 3 and 4, which explain the above embodiment and the above modified example, an example in which two transport vehicles 5 are present between the first transport vehicle 5A and the second transport vehicle 5B has been described, but this is not limiting. For example, one transport vehicle 5 or no transport vehicle 5 may be present between the first transport vehicle 5A and the second transport vehicle 5B.
[0045] In the above embodiment and modified example, the transport vehicle control unit 40 has been described as performing the replacement determination when the first transport vehicle 5A reaches the predetermined position P. However, the replacement determination may be performed periodically, for example, every T seconds. In this case, when the transport vehicle 5 that will become the first transport vehicle 5A reaches the predetermined position P within T seconds, the transport vehicle control unit 40 performs a replacement determination to determine whether the second transport vehicle 5B is present.
[0046] In the above embodiment and modified example, the predetermined position P is set only for the first station STa, which is the most upstream station in the row of stations ST, but this is not limited to this. For example, if another station ST exists downstream of the second station STb and it is desired to exchange loading requests between the second station STb and the other station ST, the predetermined position P for the second station STb is also set for the second station STb.
[0047] In the above embodiment and modified examples, a FOUP has been described as an example of an article, but the article may be a container such as a reticle pod for storing glass substrates, a general part, or the like.
[0048] In the above embodiment and modified example of the transport vehicle system 1, a ceiling transport vehicle 5 has been described as an example of a transport vehicle, but other examples of transport vehicles include unmanned transport vehicles that run on tracks installed on the ground or on a platform.
[0049] The technical subject matter of one aspect of the present invention can be described as follows: [1] A guided vehicle system comprising: a plurality of guided vehicles that travel in one direction along a predetermined route and transport articles; a plurality of stations that are provided along the route and serve as sources of requests to load the articles; and a control unit that, each time a request to load the articles is made, assigns a transport command to the guided vehicle that can arrive at the station for which the loading request was made earliest as a destination, wherein the control unit performs a swapping determination to determine whether a second guided vehicle, which is another guided vehicle than the first guided vehicle and which is assigned a transport command to a second station that is located downstream of the first station as a destination, is present upstream of a first guided vehicle, which is one of the plurality of stations and which is assigned a transport command to a second station that is one of the plurality of stations; and, when it is determined that the second guided vehicle is present upstream of the first guided vehicle, performs swapping control to swap the destinations of the transport commands assigned before the swapping determination between the first guided vehicle and the second guided vehicle. [2] The guided vehicle system according to [1], wherein the replacement determination by the control unit determines whether a second guided vehicle exists upstream of the first guided vehicle and will wait until the first guided vehicle completes its work when the first guided vehicle executes a transport command specifying the first station as its destination. [3] The guided vehicle system according to [1] or [2], wherein the replacement determination by the control unit determines whether a second guided vehicle exists that can start a transfer operation at the first station while the first guided vehicle is performing a transfer operation at the second station when the destinations of the transport commands assigned before the replacement determination are swapped. [4] The guided vehicle system according to any one of [1] to [3], wherein the control unit performs the replacement control when it determines that the second guided vehicle exists upstream of the first guided vehicle and will perform the replacement control even if another guided vehicle exists between the first guided vehicle and the second guided vehicle.[5] The control unit executes the replacement judgment when the first transport vehicle, to which a transport command with the first station as its destination is assigned, reaches a predetermined position upstream of the first station, and the predetermined position is a deceleration start position when the first transport vehicle stops at the first station. [6] A transport vehicle system described in any one of [1] to [4].
[0050] 1...transport vehicle system, 3...transport vehicle controller (control unit), 5...transport vehicle, 5A...first transport vehicle, 5B...second transport vehicle, 11...track, 40...transport vehicle control unit, P...predetermined position, ST...station, STa...first station, STb...second station.
Claims
1. A transport vehicle system comprising: a plurality of transport vehicles that travel in one direction along a predetermined route and transport items; a plurality of stations that are arranged along the route and serve as sources of requests to load the items; and a control unit that, each time a request to load the items is made, assigns a transport command to the transport vehicle that can arrive at the station where the loading request was made the earliest, with the transport vehicle having the station where the loading request was made as its destination, wherein the control unit performs a swapping determination to determine whether a second transport vehicle, which is another transport vehicle than the first transport vehicle and has been assigned a transport command with the second station, which is one of the plurality of stations, as its destination, is located upstream of a first transport vehicle, which is one of the plurality of transport vehicles and has been assigned a transport command with the second station, which is one of the plurality of stations, as its destination; and, when it is determined that the second transport vehicle is located upstream of the first transport vehicle, performs swapping control to swap the destinations of the transport commands assigned before the swapping determination between the first transport vehicle and the second transport vehicle.
2. A transport vehicle system as described in claim 1, wherein the control unit determines whether or not there is a second transport vehicle that will wait upstream of the first transport vehicle until the first transport vehicle completes its work when the first transport vehicle executes a transport command specifying the first station as its destination.
3. The transport vehicle system of claim 1, wherein the control unit makes the replacement determination by determining whether there is a second transport vehicle that can begin a transfer operation at the first station while the first transport vehicle is performing a transfer operation at the second station when the destinations of the transport commands assigned before the replacement determination are swapped.
4. A transport vehicle system as described in any one of claims 1 to 3, wherein the control unit executes the replacement control when the replacement determination determines that the second transport vehicle is present upstream of the first transport vehicle, even if another transport vehicle is present between the first transport vehicle and the second transport vehicle.
5. A transport vehicle system as claimed in any one of claims 1 to 3, wherein the control unit executes the replacement judgment when the first transport vehicle, to which a transport command with the first station as its destination is assigned, reaches a predetermined position upstream of the first station, and the predetermined position is a position at which the first transport vehicle starts to decelerate when stopping at the first station.