Goods handling equipment

Abstract

To realize an article carrier facility capable of facilitating a maintaining of a good communication state with a control device and a transportation vehicle.SOLUTION: A transportation vehicle is constructed so as to maintain a state of being communicable with a control device by switching an access point of a connection destination while moving in a path. In the case where a communication strength of an electric wave of the transportation vehicle and the access point becomes less than a predetermined switching threshold value, the transportation vehicle performs a switching processing for switching a communication destination to the other access point of which the communication strength is stronger. The switching threshold value is set to a different value in accordance with a movement condition of the transportation vehicle.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to an article conveying facility including a carrier that moves along a specified path to convey an article, a control device that controls the carrier, and a plurality of access points that each perform wireless communication with the carrier.

Background Art

[0002] For example, Japanese Patent Application Laid-Open No. 2014-192577 (Patent Document 1) discloses an invention related to wireless communication. Hereinafter, the reference numerals shown in parentheses in the description of the background art are those of Patent Document 1.

[0003] In the invention described in Patent Document 1, a wireless communication device mounted on a mobile terminal (2) as a moving body performs wireless communication with an access point (60). This wireless communication device includes a radio wave intensity detection unit (50) that detects the radio wave intensity (X1) in the wireless communication with the connected access point (60), and determines whether or not the radio wave intensity (X1) is lower than a roaming threshold value (Xth) at a predetermined time interval. When it is determined that the radio wave intensity (X1) is lower than the roaming threshold value (Xth), a roaming process for switching the connected access point (60) is performed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Such wireless communication technology could be applied to goods transport equipment where wireless communication between a transport vehicle and a control device is performed via an access point. However, as in the invention described in Patent Document 1, if the determination of whether the radio wave strength is below the roaming threshold is performed at predetermined time intervals, it may not be possible to perform roaming processing at the appropriate timing depending on the transport vehicle's movement conditions. For example, when a transport vehicle is moving at high speed, the distance traveled in the same amount of time is longer than when it is moving at a lower speed. If the distance to the connected access point becomes significantly longer due to the transport vehicle's high speed, a connection state with an access point with relatively weak communication strength may be maintained. Maintaining a connection state with an inappropriate access point can be a cause of communication failure.

[0006] In light of the above circumstances, there is a need for the realization of an item handling system that can easily maintain good communication between the control device and the transport vehicle. [Means for solving the problem]

[0007] A transport vehicle that moves along a predetermined route to carry goods, A control device for controlling the transport vehicle, An article transporting system comprising a plurality of access points, each of which communicates wirelessly with the transport vehicle, The transport vehicle is configured to communicate with the control device by switching the access point to which it is connected while moving along the aforementioned route. When the radio signal strength between the transport vehicle and the access point falls below a predetermined switching threshold, the transport vehicle performs a switching process to switch its connection destination to another access point with a stronger signal strength. The switching threshold is set to a different value depending on the movement conditions of the transport vehicle. 、 The aforementioned route includes at least a first area and a second area. The second area is an area where the average travel speed of the transport vehicle is higher compared to the first area. The aforementioned movement condition is that the transport vehicle moves between the first area and the second area. The switching threshold of the transport vehicle while it is moving through the second area is set to a higher value than the switching threshold of the transport vehicle while it is moving through the first area. .

[0008] According to this configuration, the switching threshold value serving as a reference for the carrier to perform switching processing (roaming processing) is set to different values according to the movement conditions of the carrier. Therefore, the switching threshold value can be set according to the movement conditions of the carrier. Accordingly, according to this configuration, it becomes easier to maintain a good communication state between the control device and the carrier. Furthermore, with this configuration, in the second area, where the average travel speed of the transport vehicle is higher than in the first area, the switching threshold is set to a relatively high value. Therefore, in the second area, the frequency of access point switching by the transport vehicle tends to increase. Consequently, with this configuration, it is difficult to maintain a connection with an access point that is far away, and the transport vehicle can be prompted to connect to an access point that is more suitable for connection.

[0009] Other goods handling equipment includes, A transport vehicle that moves along a predetermined route to carry goods, A control device for controlling the transport vehicle, An article transporting system comprising a plurality of access points, each of which communicates wirelessly with the transport vehicle, The transport vehicle is configured to communicate with the control device by switching the access point to which it is connected while moving along the aforementioned route. When the radio signal strength between the transport vehicle and the access point falls below a predetermined switching threshold, the transport vehicle performs a switching process to switch its connection destination to another access point with a stronger signal strength. The switching threshold is set to a different value depending on the movement conditions of the transport vehicle. The transport vehicle is further configured to perform the switching process at a predetermined set interval. The aforementioned setting period is changed according to the aforementioned movement conditions.

[0010] Further features and advantages of the technology according to the present disclosure will become clearer from the following description of exemplary and non-limiting embodiments described with reference to the drawings.

Brief Description of the Drawings

[0011] [Figure 1] Plan view of the article conveying facility [Figure 2] Control block diagram [Figure 3] Conceptual diagram showing the communication configuration [Figure 4] Diagram showing an example of switching of the access point [Figure 5] Diagram showing an example of a path divided into a plurality of areas [Figure 6] Diagram showing the relationship between the average moving speed of the carrier set for each area and the switching threshold value [Figure 7] Diagram showing a path divided into a plurality of areas in other embodiments [Figure 8]A diagram showing the relationship between the transport vehicle's movement speed and the switching threshold in other embodiments. [Modes for carrying out the invention]

[0012] The following describes an embodiment of the goods transport equipment with reference to the drawings.

[0013] As shown in Figure 1, the goods transport equipment 100 includes a transport vehicle 1 that transports goods (not shown) along a predetermined route 8, and a control device 2 (see Figure 2, etc.) that controls the transport vehicle 1.

[0014] As shown in Figure 3, in this embodiment, the path 8 is configured using rails 80 installed near the ceiling. The transport vehicle 1 is configured as a so-called overhead transport vehicle that travels while being supported by such rails 80. In this embodiment, the transport vehicle 1 comprises a main body 10, a running section 11 that travels along the rails 80, and a holding section 12 that holds articles. The main body 10 is configured to accommodate the holding section 12 and the articles held by the holding section 12.

[0015] As shown in Figure 1, in this embodiment, the goods transport equipment 100 includes a plurality of transfer target locations 9 provided along the path 8. The transfer target locations 9 are located below the path 8. In this example, the path 8 includes an interbay and a plurality of intrabays connected to the interbay. Each intrabay is provided with a plurality of transfer target locations 9. The interbay can be described as the movement area where the transport vehicle 1 primarily moves. The intrabay can be described as the transfer area where the transport vehicle 1 primarily performs the transfer of goods. The transport vehicle 1 is configured to transfer goods between the transfer target location 9 and the transfer target location by raising and lowering the holding section 12 (see Figure 3).

[0016] In this embodiment, the goods transport equipment 100 is equipped with multiple transport vehicles 1. Each of the multiple transport vehicles 1 is configured to receive a transport command from a control device 2 (see Figure 2, etc.) and to perform a task corresponding to the transport command. For example, the transport command includes information about the source and destination of the goods. A transport vehicle 1 that receives a transport command transports the goods from the source to the destination. The source and destination include the transfer target location 9.

[0017] Various items can be handled by the item handling equipment 100. In this example, the item handling equipment 100 is used in a semiconductor manufacturing plant. Therefore, items include substrate containers (so-called FOUPs: Front Opening Unified Pods) that house substrates (wafers, panels, etc.) and reticle containers (so-called reticle pods) that house reticles. In this case, the transport vehicle 1 transports items such as substrate containers and reticle containers along the route 8 between each process.

[0018] In this embodiment, the transfer target location 9 comprises a processing device 90 that performs processing on an article, and a mounting table 91 positioned adjacent to the processing device 90. In this specification, "processing on an article" means processing on the contents (substrates or reticles) contained in the article, which serves as a container. The transport vehicle 1 receives articles that have been processed by the processing device 90 from the mounting table 91, or hands over articles that have not yet been processed by the processing device 90 to the mounting table 91. The processing apparatus 90 performs various processes, such as thin film formation, photolithography, and etching.

[0019] As shown in Figure 2, the goods transport equipment 100 is equipped with multiple access point APs (only one access point AP is shown in Figure 2), each of which communicates wirelessly with the transport vehicle 1. An access point AP is positioned in the center of each of the multiple circular areas shown in Figure 1. These circular areas indicate the approximate communication range of each access point AP. However, this is only an estimate, and communication may be possible even outside the circular areas.

[0020] The control device 2 and the transport vehicle 1 are configured to communicate bidirectionally via one of several access points AP. As will be described in detail later, the control device 2 is configured to repeatedly transmit a confirmation signal Sc to the transport vehicle 1 at a set interval. The transport vehicle 1 is configured to transmit a receipt signal Sr to the control device 2 in response to receiving the confirmation signal Sc. With this configuration, the control device 2 can periodically check the communication status with the transport vehicle 1.

[0021] In this embodiment, the control device 2 comprises a processing unit 20 and a storage unit 21. The processing unit 20 is configured using an arithmetic processing unit such as a CPU (Central Processing Unit). The storage unit 21 is configured using a storage device that can be accessed by the arithmetic processing unit, such as RAM (Random Access Memory) or ROM (Read Only Memory). The various functions of the control device 2 are powered by software (programs) stored in the storage unit 21, hardware such as separately provided arithmetic circuits, or both. The processing unit 20 of the control device 2 operates as a computer that executes each program.

[0022] In this embodiment, the transport vehicle 1 comprises a transport vehicle control unit 13 and a wireless communication device 14. The transport vehicle control unit 13 is configured using a processing unit such as a CPU (Central Processing Unit). The wireless communication device 14 is configured to communicate with the control device 2. In this example, the wireless communication device 14 is configured to communicate wirelessly with each of the multiple access point APs. Each of the multiple access point APs is configured to communicate with the control device 2 via a wired connection. That is, the wireless communication device 14 is configured to communicate with the control device 2 via any of the multiple access point APs.

[0023] As shown in Figure 3, the control device 2 is connected to an operating terminal. Operators can input various commands to the control device 2 by operating the operating terminal, and can also refer to the control status using the operating terminal.

[0024] The access point (AP) is configured using wireless access point equipment. The access point (AP) is configured to emit radio waves. The communication strength between the access point (AP) and the transport vehicle (1) is expressed as RSSI (Received Signal Strength Indicator). The unit is, for example, decibel-milliwatt (dBm).

[0025] As shown in Figure 4, the transport vehicle 1 is configured to communicate with the control device 2 by switching the connected access point AP while moving along the path 8. In the example shown in Figure 4, the first access point AP1, the second access point AP2, and the third access point AP3 are arranged adjacent to each other along the path 8. In this case, the transport vehicle 1 switches its connection destination from the state where it is connected to the first access point AP1 to the second access point AP2. Then, the transport vehicle 1 switches its connection destination from the state where it is connected to the second access point AP2 to the third access point AP3. In this way, the transport vehicle 1 switches the connected access point AP while moving along the path 8.

[0026] When the radio signal strength between the transport vehicle 1 and the access point AP falls below a predetermined switching threshold X, the transport vehicle 1 performs a switching process to switch its connection destination to another access point AP with a stronger signal strength. As described above, the radio signal strength is represented by RSSI. The transport vehicle 1 performs a switching process when the RSSI with the currently connected access point AP falls below the switching threshold X.

[0027] Generally, the closer you are to the access point (AP), the stronger the communication signal becomes. Consider the example shown in Figure 4, where transport vehicle 1 moves along path 8 from address 1001 to address 1017. The communication strength between the transport vehicle 1 and the first access point AP1 is strongest when the transport vehicle 1 is at address 1004, which is the closest address to the first access point AP1. After passing address 1004, the transport vehicle 1 moves away from the first access point AP1, and the communication strength gradually weakens. When the communication strength falls below the switching threshold X, the transport vehicle 1 performs a switching process and switches its connection destination to another access point AP. In the illustrated example, the transport vehicle 1 switches its connection destination to the second access point AP2. Similarly, the transport vehicle 1 also switches its connection destination from the second access point AP2 to the third access point AP3.

[0028] In this embodiment, the transport vehicle 1 is equipped with a communication strength detection unit (not shown) that detects the communication strength with the access point AP. The communication strength detection unit detects the communication strength at a fixed detection interval. This detection interval may be a preset one, or it may be an interval that inevitably occurs as a result of executing a predetermined control flow.

[0029] Based on the detection results from the communication strength detection unit, the transport vehicle 1 executes a switching process when the communication strength falls below the switching threshold X. In other words, in this embodiment, the switching process is performed by the transport vehicle 1 itself.

[0030] The switching threshold X is set to different values ​​depending on the movement conditions of the transport vehicle 1. The "movement conditions" include the movement speed V of the transport vehicle 1 and conditions related to the movement speed V. For example, the "movement condition" is that the movement speed V of the transport vehicle 1 changes. In this case, the switching threshold X is set to different values ​​depending on the movement speed V of the transport vehicle 1. Another example is that the "movement condition" is that the transport vehicle 1 moves between multiple areas on the route 8. In this case, the switching threshold X should be set to different values ​​depending on the average movement speed of the transport vehicle 1 set for each of the multiple areas. In the example described later, the "movement condition" is that the transport vehicle 1 moves between the first area A1 and the second area A2.

[0031] When the "movement condition" is set to the movement speed V of the transport vehicle 1, the switching threshold X is set to increase in proportion to the increase in the movement speed V of the transport vehicle 1. The higher the movement speed V of the transport vehicle 1, the longer the distance the transport vehicle 1 moves during the above detection cycle, that is, the cycle in which the communication strength detection unit detects the communication strength. In other words, the relative distance between the transport vehicle 1 and the access point AP connected to the transport vehicle 1 increases between the time one communication strength is detected and the time until the next communication strength detection. In this case, when the communication strength is detected again, it may have become too weak to enable proper communication. However, by setting the switching threshold X to increase in proportion to the increase in movement speed V, it is possible to prompt the transport vehicle 1, which is moving at a relatively high speed, to perform a switching process. This makes it possible for the transport vehicle 1 to perform a switching process to another access point AP before the communication strength with the access point AP becomes too weak.

[0032] Although detailed illustrations are omitted, the transport vehicle 1 is equipped with a speed detection unit that detects its own movement speed V, and performs a switching process based on the detection result from the speed detection unit. The speed detection unit is configured, for example, using a rotary encoder. In this embodiment, information on the movement speed V of the transport vehicle 1 is not transmitted to the control device 2. Therefore, the control device 2 cannot ascertain the movement speed V of the transport vehicle 1, and in a configuration where the switching process is performed based on the movement speed V of the transport vehicle 1, the control device 2 cannot send a command to the transport vehicle 1 to perform the switching process.

[0033] As shown in Figure 5, in this embodiment, the path 8 is set to include at least a first area A1 and a second area A2. The second area A2 is an area where the average moving speed Va of the transport vehicle 1 is higher than that of the first area A1. In this example, the second area A2 is an area where the speed limit of the transport vehicle 1 is set higher than that of the first area A1. As a result of the higher speed limit in the second area A2, the average moving speed Va of the transport vehicle 1 moving within the second area A2 is higher.

[0034] In this embodiment, each intrabay in the route 8 is designated as the first area A1. That is, the intrabay that is the transfer area where the transport vehicle 1 mainly performs the transfer of goods is designated as the first area A1. Since the transport vehicle 1 performs the transfer of goods in the intrabay, the speed limit tends to be set relatively low. Therefore, the first average travel speed Va1, which is the average travel speed Va of the transport vehicle 1 moving in the first area A1, is lower than the second average travel speed Va2, which is the average travel speed Va of the transport vehicle 1 moving in the second area A2 (see Figure 6).

[0035] In this embodiment, the interbay in the route 8 is designated as the second area A2. That is, the interbay, which is the area where the transport vehicle 1 primarily moves, is designated as the second area A2. In principle, no transfer of goods by the transport vehicle 1 is performed in the interbay; the transport vehicle 1 primarily moves within the interbay. Therefore, a relatively high speed limit can be set in the interbay. Consequently, the second average travel speed Va2 of the transport vehicle 1 moving in the second area A2 is higher than the first average travel speed Va1 of the transport vehicle 1 moving in the first area A1 (see Figure 6).

[0036] Although detailed illustrations are omitted, there may be areas where the average movement speed Va of the transport vehicle 1 is higher than that of the second area A2 (for example, the third area A3). Such a third area A3 is an area where the speed limit for the transport vehicle 1 is set higher than that of the second area A2. Therefore, the third average movement speed Va3, which is the average movement speed Va of the transport vehicle 1 moving in the third area A3, will be higher than the second average movement speed Va2 of the transport vehicle 1 moving in the second area A2 (see Figure 6).

[0037] As shown in Figure 6, in this embodiment, the average travel speed Va (limit speed) of the transport vehicle 1 is determined in each area A1 to A3, and a switching threshold X is also determined.

[0038] In this embodiment, the second switching threshold X2 of the transport vehicle 1 while it is moving through the second area A2 is set to a higher value than the first switching threshold X1 of the transport vehicle 1 while it is moving through the first area A1. As a result, the frequency of access point AP switching by the transport vehicle 1 tends to increase in the second area A2. Furthermore, in this example, the third switching threshold X3 of the transport vehicle 1 while it is moving through the third area A3 is set to a higher value than the second switching threshold X2 of the transport vehicle 1 while it is moving through the second area A2. As a result, the frequency of access point AP switching by the transport vehicle 1 tends to increase even further in the third area A3. With the above configuration, it becomes difficult to maintain a connection with an access point AP that is far away, and the transport vehicle 1 can be prompted to connect to an access point AP that is suitable for connection.

[0039] Although detailed illustrations are omitted, the transport vehicle 1 is configured to travel while sequentially reading multiple information holders installed along the route 8. Each information holder holds the address information of the location where it is installed. Therefore, the transport vehicle 1 can determine its current position by reading the information holders. In this embodiment, based on its current position information, the transport vehicle 1 sets the switching threshold X to the first switching threshold X1 if it is in the first area A1, and sets the switching threshold X to the second switching threshold X2 if it is in the second area A2. The current position information of the transport vehicle 1 is transmitted to the control device 2. Therefore, the control device 2 can determine the current position of the transport vehicle 1. Accordingly, the control device 2 may issue a setting command to the transport vehicle 1 to set the switching threshold X based on the current position information of the transport vehicle 1. Upon receiving the setting command from the control device 2, the transport vehicle 1 sets the switching threshold X according to the content of the setting command.

[0040] In this embodiment, the transport vehicle 1 is further configured to perform switching processing at predetermined set intervals. That is, in this embodiment, the switching processing by the transport vehicle 1 is performed when the radio wave communication strength between the transport vehicle 1 and the access point AP falls below the switching threshold X, and at the set interval. Therefore, even if the communication strength is above the switching threshold X, the transport vehicle 1 will perform switching processing if the set interval has arrived. Also, even if the set interval has not arrived, the transport vehicle 1 will perform switching processing if the communication strength is below the switching threshold X. This configuration can further facilitate the switching processing by the transport vehicle 1.

[0041] In this embodiment, the set period is changed according to the movement conditions. In this example, the set period is changed to a different period depending on whether the transport vehicle 1 is in the first area A1 or the second area A2. As described above, the second area A2 is an area where the average movement speed Va of the transport vehicle 1 is higher than that of the first area A1, so it is preferable to have a higher frequency of switching processes. Therefore, in this example, the set period when the transport vehicle 1 is in the second area A2 is changed to a shorter period than the set period when the transport vehicle 1 is in the first area A1. This makes it easier to trigger the switching process in the second area A2.

[0042] In addition to or separate from the above configuration, the setting period may be changed to a shorter period in accordance with the increasing speed of the transport vehicle 1. In this case, the higher the speed of the transport vehicle 1, the more frequently the transport vehicle 1 performs the switching process. Therefore, it is easier to encourage the switching process when the transport vehicle 1 is moving at a high speed.

[0043] [Other Embodiments] Next, other embodiments will be described.

[0044] (1) In the above embodiment, an example was described in which each intrabay in the route 8 is designated as a first area A1 where the average travel speed Va of the transport vehicle 1 is relatively low, and the interbays in the route 8 are designated as a second area A2 where the average travel speed Va of the transport vehicle 1 is relatively high. In other words, an example was described in which areas are partitioned on a bay-by-bay basis. However, the example is not limited to this example, and areas may be partitioned according to the shape of each part of the route 8. For example, as shown in Figure 7, the curved path 81 in the route 8 may be designated as the first area A1, and the straight path 82 in the route 8 may be designated as the second area A2. In the curved path 81, the average travel speed Va of the transport vehicle 1 is relatively low. In the straight path 82, the average travel speed Va of the transport vehicle 1 is relatively high.

[0045] (2) In the above embodiment, an example was described in which the switching threshold X is set to increase in accordance with the increasing travel speed V of the transport vehicle 1. The switching threshold X may be set to increase continuously in accordance with the increasing travel speed V of the transport vehicle 1, or it may be set to increase in steps, as shown in Figure 8. In the example shown in Figure 8, when the travel speed V of the transport vehicle 1 is in the range from zero to the first speed V1, the switching threshold X is set to the first switching threshold X1. When the travel speed V of the transport vehicle 1 is in the range from the first speed V1 to the second speed V2 which is higher than the first speed V1, the switching threshold X is set to the second switching threshold X2 which is higher than the first switching threshold X1. When the travel speed V of the transport vehicle 1 is in the range from the second speed V2 to the third speed V3 which is higher than the second speed V2, the switching threshold X is set to the third switching threshold X3 which is higher than the second switching threshold X2.

[0046] (3) In the above embodiment, an example was described in which the switching process is performed by the transport vehicle 1 itself. However, the invention is not limited to such an example, and for example, the transport vehicle 1 may perform the switching process in response to a switching command from the control device 2. In this case, as described above, the control device 2 can issue a switching command to the transport vehicle 1 based on the transport vehicle 1's current position information.

[0047] (4) In the above embodiment, an example was described in which the route 8 is configured using rails 80 installed near the ceiling, and the transport vehicle 1 is configured as an overhead transport vehicle that travels while being supported by the rails 80. However, the transport vehicle 1 is not limited to this example and may be configured as a floor transport vehicle that travels on the floor. In this case, the route 8 may be configured using magnetic tape or the like provided along the floor, or it may be virtually set along the floor.

[0048] (5) The configurations disclosed in the embodiments described above can be applied in combination with configurations disclosed in other embodiments, as long as no inconsistencies arise. With regard to other configurations, the embodiments disclosed herein are merely illustrative in all respects. Therefore, various modifications can be made as appropriate without departing from the spirit of this disclosure.

[0049] [Summary of this embodiment] The following is a summary of this embodiment.

[0050] A transport vehicle that moves along a predetermined route to carry goods, A control device for controlling the transport vehicle, An article transporting system comprising a plurality of access points, each of which communicates wirelessly with the transport vehicle, The transport vehicle is configured to communicate with the control device by switching the access point to which it is connected while moving along the aforementioned route. When the radio signal strength between the transport vehicle and the access point falls below a predetermined switching threshold, the transport vehicle performs a switching process to switch its connection destination to another access point with a stronger signal strength. The switching threshold is set to a different value depending on the movement conditions of the transport vehicle.

[0051] In this configuration, the switching threshold, which serves as the basis for the transport vehicle to perform switching processing (roaming processing), is set to a different value depending on the transport vehicle's movement conditions. Therefore, the switching threshold can be set according to the transport vehicle's movement conditions. Consequently, this configuration makes it easier to maintain good communication between the control device and the transport vehicle.

[0052] The aforementioned route includes at least a first area and a second area. The second area is an area where the average travel speed of the transport vehicle is higher compared to the first area. The aforementioned movement condition is that the transport vehicle moves between the first area and the second area. Preferably, the switching threshold of the transport vehicle moving in the second area is set to a higher value than the switching threshold of the transport vehicle moving in the first area.

[0053] In this configuration, in the second area, where the average travel speed of the transport vehicle is higher than in the first area, the switching threshold is set to a relatively high value. Therefore, in the second area, the frequency of access point switching by the transport vehicle tends to increase. Consequently, with this configuration, it is difficult to maintain a connection with an access point that is far away, and the transport vehicle can be prompted to connect to an access point that is more suitable for connection.

[0054] The aforementioned movement condition is a change in the movement speed of the transport vehicle. It is preferable that the switching threshold is set to increase continuously or gradually in response to an increase in the moving speed of the transport vehicle.

[0055] In this configuration, the higher the transport vehicle's movement speed, the higher the switching threshold value is set. Therefore, it is difficult to maintain a connection with a distant access point, and the transport vehicle can be prompted to connect to a more suitable access point.

[0056] The transport vehicle is further configured to perform the switching process at a predetermined set interval. Preferably, the setting period is changed according to the movement conditions.

[0057] In this configuration, the transport vehicle performs a switching process not only when the radio signal strength with the access point falls below a switching threshold, but also at a set interval. The set interval is changed according to the movement conditions. Therefore, for example, depending on the movement conditions, it is possible to change the set interval to a shorter period than usual, which in turn can prompt the transport vehicle to perform the switching process. Consequently, this configuration makes it easier to maintain good communication between the control device and the transport vehicle. [Industrial applicability]

[0058] The technology relating to this disclosure can be used in an article transport system comprising a transport vehicle that moves along a predetermined route to transport articles, a control device that controls the transport vehicle, and a plurality of access points, each of which communicates wirelessly with the transport vehicle. [Explanation of Symbols]

[0059] 100: Goods handling equipment 1: Transport vehicle 2: Control device 8: Route A1: Area 1 A2: Area 2 AP: Access Point V: Movement speed Va: average moving speed X: Switching threshold

Claims

1. A transport vehicle that moves along a predetermined route to carry goods, A control device for controlling the transport vehicle, An article transporting system comprising a plurality of access points, each of which communicates wirelessly with the transport vehicle, The transport vehicle is configured to communicate with the control device by switching the access point to which it is connected while moving along the aforementioned route. When the radio signal strength between the transport vehicle and the access point falls below a predetermined switching threshold, the transport vehicle performs a switching process to switch its connection destination to another access point with a stronger signal strength. The switching threshold is set to a different value depending on the movement conditions of the transport vehicle. The aforementioned route includes at least a first area and a second area. The second area is an area where the average movement speed of the transport vehicle is higher compared to the first area. The aforementioned movement condition is that the transport vehicle moves between the first area and the second area. An article transporting system wherein the switching threshold of the transport vehicle moving in the second area is set to a higher value than the switching threshold of the transport vehicle moving in the first area.

2. A transport vehicle that moves along a predetermined route to carry goods, A control device for controlling the transport vehicle, An article transporting system comprising a plurality of access points, each of which communicates wirelessly with the transport vehicle, The transport vehicle is configured to communicate with the control device by switching the access point to which it is connected while moving along the aforementioned route. When the radio signal strength between the transport vehicle and the access point falls below a predetermined switching threshold, the transport vehicle performs a switching process to switch its connection destination to another access point with a stronger signal strength. The switching threshold is set to a different value depending on the movement conditions of the transport vehicle. The transport vehicle is further configured to perform the switching process at a predetermined set interval. The aforementioned setting cycle is changed according to the aforementioned movement conditions in the goods transport equipment.

3. The aforementioned movement condition is a change in the movement speed of the transport vehicle. The article transport equipment according to claim 1 or 2, wherein the switching threshold is set to increase continuously or in stages as the travel speed of the transport vehicle increases.

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