Wireless communication system and wireless communication control method

Abstract

A transport carriage (10) comprises a communication unit (11) that performs interlock communication for delivery of an article between the transport carriage (10) and a communication device (22) by wireless communication, a measurement unit (12) that uses the communication unit (11) to measure the reception signal intensity of background noise when the transport carriage (10) is moving upstream of a delivery position at which the article is to be delivered to an installation port (20), and a control unit (15) that controls the interlock communication performed by the communication unit (11). The control unit (15) determines whether the reception signal intensity measured by the measurement unit (12) is lower than a reference value and (a) upon determining that the reference signal intensity is lower than the reference value, performs control that starts the interlock communication while the transport carriage (10) is moving upstream of the delivery position but (b) upon determining that the reference signal intensity is not lower than the reference value, performs control that starts the interlock communication when the transport carriage (10) is stopped at the delivery position.

Description

Wireless communication system and wireless communication control method

[0001] The present invention relates to a wireless communication system and a wireless communication control method.

[0002] There is a transport vehicle that transports items while moving on a track. The transport vehicle can deliver items to and from a loading port, which is a location where the items are loaded. In other words, the transport vehicle can deliver an item to the loading port, thereby loading the item onto the loading port, and can also receive an item from the loading port.

[0003] When the transport vehicle transfers an article to or from a loading port, an interlock sequence is used, which employs interlock communication using wireless communication.

[0004] Patent document 1 shows a wireless communication system including a communication unit provided on a transport vehicle and a communication device connected to a loading port where items are delivered by the transport vehicle and which performs wireless communication with the communication unit.

[0005] Patent No. 6854498

[0006] The transport vehicle is required to transport a large number of articles, in other words, to improve the efficiency of article transport. To improve the efficiency of article transport, it is required to reduce the stop time of the transport vehicle.

[0007] An object of the present invention is to provide a wireless communication system and the like that can improve the transport efficiency of a transport vehicle.

[0008] Hereinafter, examples of inventions that can be obtained from the disclosure of this specification will be given, and the effects and the like that can be obtained from these inventions will be explained.

[0009] (1) A wireless communication system comprising a transport vehicle that moves along a track and transports an item, and a communication device connected to a port to which the item is delivered by the transport vehicle, wherein the transport vehicle comprises a communication unit that performs interlock communication between the transport vehicle and the communication device via wireless communication for the delivery of the item, a measurement unit that measures the received signal strength of background noise using the communication unit when the transport vehicle is moving upstream of a delivery position where the item is delivered to the port, and a control unit that controls the interlock communication performed by the communication unit, wherein the control unit determines whether the received signal strength measured by the measurement unit is smaller than a reference value, and (a) if it determines that the received signal strength is smaller than the reference value, controls to start the interlock communication while the transport vehicle is moving upstream of the delivery position, and (b) if it determines that the received signal strength is not smaller than the reference value, controls to start the interlock communication while the transport vehicle is stopped at the delivery position.

[0010] According to the above aspect, in the wireless communication system, if the received signal strength of the background noise received by the transport vehicle is smaller than a reference value, it can be determined that the noise level is such that wireless interference can be ignored even if interlock communication using a similar wireless communication is occurring nearby. Therefore, the transport vehicle can start interlock communication at a position upstream from the item transfer position, thereby shortening the time the transport vehicle is stopped at the transfer position. Furthermore, if the received signal strength of the background noise is not smaller than the reference value, it can be determined that interlock communication using a similar wireless communication is occurring nearby and that wireless interference is at a level that cannot be ignored. Therefore, by starting stable interlock communication after the transport vehicle stops at the transfer position, it is possible to prevent interlock communication from failing due to wireless communication interference. This allows the wireless communication system to improve the transport efficiency of the transport vehicle. Furthermore, the wireless communication system can improve the quality of wireless communication in interlock communication.

[0011] (2) In the wireless communication system described in (1), even if the control unit determines in (b) that the received signal strength is not smaller than the reference value, when the control unit determines that the length of the period during which the received signal strength is smaller than the reference value is longer than a threshold value, the control unit controls to start the interlock communication while the transport vehicle is moving upstream of the transfer position.

[0012] According to the above aspect, in the wireless communication system, if the duration of the period during which the received signal strength of the background noise received by the transport vehicle is smaller than a reference value is longer than a threshold, it is determined that there is an available time slot for time division communication, and the transport vehicle can start interlock communication using time division wireless communication while moving at a position upstream from the transfer position, thereby shortening the time the transport vehicle is stopped at the transfer position. As a result, even if the received signal strength of the background noise received by the transport vehicle is not smaller than the reference value, if the duration of the period during which the received signal strength of the background noise is smaller than the reference value is longer than the threshold, the transport vehicle can start interlock communication within that period, thereby shortening the time the transport vehicle is stopped at the transfer position. In this way, the wireless communication system can improve the transport efficiency of the transport vehicle.

[0013] (3) The wireless communication system according to (1) or (2), wherein the reference value is smaller than the transmission strength of the radio waves transmitted by the communication unit in the wireless communication.

[0014] According to the above aspect, in the wireless communication system, the transporting vehicle can easily determine the reference value using the transmission strength of the radio waves from the communication unit, and can start interlock communication after making a judgment using the determined reference value. In this way, the wireless communication system can more easily improve the transport efficiency of the transporting vehicle.

[0015] (4) The wireless communication system further includes a first memory unit that stores, for each of one or more communication devices including the communication device, the transmission strength of the radio waves of the communication unit when communicating with the communication device, in association with the communication device, and the control unit reads out the transmission strength of the radio waves stored in the first memory unit in association with the communication device with which the communication unit is to perform the interlock communication, and controls the communication unit to perform the interlock communication using the read transmission strength of the radio waves, a wireless communication system described in any of (1) to (3).

[0016] According to the above aspect, in the wireless communication system, the transport vehicle can perform interlock communication at a radio wave transmission strength appropriate for each communication device. If the radio wave transmission strength is less than the required strength, communication loss may occur, resulting in a failure of the interlock communication. Furthermore, if the radio wave transmission strength is greater than required, it may interfere with the wireless communication of other communication devices. By having the transport vehicle perform interlock communication at a radio wave transmission strength appropriate for each communication device, it is possible to prevent failure of interlock communication while also preventing interference with the wireless communication of other communication devices, thereby improving the communication efficiency of the wireless communication system as a whole. Therefore, the wireless communication system can improve the transport efficiency of the transport vehicle. Note that in the above aspect, the first memory unit included in the wireless communication system refers to a memory unit included in one or more of the transport vehicle and communication devices, including the communication device, that constitute the wireless communication system.

[0017] (5) A wireless communication system as described in (4), wherein the transmission strength of the radio waves stored in the first memory unit includes the transmission strength of the radio waves when the interlock communication is performed while the transport vehicle is moving and the transmission strength of the radio waves when the interlock communication is performed while the transport vehicle is stopped.

[0018] According to the above aspect, in the wireless communication system, the transporting vehicle can more easily perform interlock communication at a radio wave transmission strength appropriate for each communication device by using the radio wave transmission strength when interlock communication is performed while the transporting vehicle is moving and the radio wave transmission strength when interlock communication is performed while the transporting vehicle is stopped. This allows the transporting vehicle to improve the communication efficiency of the wireless communication system as a whole. Therefore, the wireless communication system can improve the transport efficiency of the transporting vehicle.

[0019] (6) The wireless communication system according to (4), wherein the control unit stores the transmission strength of the radio waves of the communication unit in the first memory unit when the interlock communication ends.

[0020] According to the above aspect, in the wireless communication system, the transporting vehicle can more easily perform interlock communication at a radio wave transmission strength appropriate for each communication device by using the radio wave transmission strength of the communication unit stored in the first storage unit at the time of ending the interlock communication. This allows the transporting vehicle to improve the communication efficiency of the wireless communication system as a whole. Therefore, the wireless communication system can improve the transport efficiency of the transporting vehicle.

[0021] (7) A wireless communication system as described in (4), in which, when the control unit cannot read out the radio wave transmission strength stored in the first memory unit in association with the communication device with which the communication unit is performing the interlock communication, the control unit controls the communication unit to perform the interlock communication using a default strength, which is a predetermined transmission strength, as the radio wave transmission strength.

[0022] According to the above aspect, in the wireless communication system, when the transporting vehicle cannot read out the radio wave transmission strength appropriate for each communication device from the first storage unit, the transporting vehicle can perform interlock communication using a default strength. This appropriately avoids a situation where the transporting vehicle cannot determine the radio wave transmission strength to be used for interlock communication. Therefore, the wireless communication system can more appropriately improve the transport efficiency of the transporting vehicle.

[0023] (8) The control unit causes the communication unit to perform wireless communication at a second intensity, which is a transmission intensity lower than a first intensity, which is a transmission intensity used by the communication unit for wireless communication, and if the wireless communication performed at the second intensity is successful, sets the transmission intensity of the radio waves of the communication unit to the second intensity and stores the second intensity in the first memory unit as the transmission intensity of the radio waves. This is a wireless communication system described in (4) or (5).

[0024] According to the above aspect, in the wireless communication system, when the transporting vehicle can perform wireless communication at a lower strength than the strength currently used for wireless communication, the transporting vehicle can perform wireless communication at the lowered strength. This allows the transporting vehicle to suppress wireless communication failures while suppressing interference with wireless communication of other communication devices, thereby improving the communication efficiency of the wireless communication system as a whole. Therefore, the wireless communication system can improve the transport efficiency of the transporting vehicle.

[0025] (9) The wireless communication system further includes a second memory unit that stores, for each of one or more communication devices including the communication device, the transmission strength of the radio waves of the communication device when the communication device communicates with the communication unit, in association with the communication device; when the communication unit starts the interlock communication with the communication device, the control unit reads the transmission strength of the radio waves stored in the second memory unit in association with the communication device and transmits the read transmission strength of the radio waves to the communication device; the communication device receives the transmission strength of the transmitted radio waves and performs the interlock communication using the transmission strength of the received radio waves, a wireless communication system described in any of (1) to (8).

[0026] According to the above aspect, in the wireless communication system, the communication devices can perform interlock communication with the transport vehicle using radio wave transmission strength appropriate for each communication device. If the radio wave transmission strength is less than the required strength, communication loss may occur, resulting in a failure of the interlock communication. Furthermore, if the radio wave transmission strength is greater than required, it may interfere with the wireless communication of other communication devices. By having the communication devices perform interlock communication using radio wave transmission strength appropriate for each communication device, it is possible to prevent interlock communication failures while also preventing interference with the wireless communication of other communication devices, thereby improving the communication efficiency of the wireless communication system as a whole. Therefore, the wireless communication system can improve the transport efficiency of the transport vehicle. Note that in the above aspect, the second memory unit included in the wireless communication system refers to a memory unit included in one or more of the transport vehicle and the communication devices, including the communication device, that constitute the wireless communication system. Furthermore, as described above, the second memory unit has a function of storing information different from that of the first memory unit described in (4) and does not necessarily need to be realized using hardware separate from the first memory unit.

[0027] (10) The communication device performs wireless communication at a fourth intensity, which is a transmission intensity lower than a third intensity, which is the transmission intensity used by the communication device for wireless communication, and if the wireless communication performed by the communication device at the fourth intensity is successful, the control unit sets the transmission intensity of the radio waves to the fourth intensity and stores the fourth intensity in the second memory unit, and when new interlock communication starts after the interlock communication has ended, the control unit reads out the transmission intensity of the radio waves stored in the second memory unit in association with the communication device and transmits the read transmission intensity of the radio waves to the communication device, and the communication device receives the transmission intensity of the transmitted radio waves and performs the interlock communication using the transmission intensity of the received radio waves, in the wireless communication system described in (9).

[0028] According to the above aspect, in the wireless communication system, when the communication device can perform wireless communication at a lower strength than the strength currently used for wireless communication, the communication device can perform wireless communication at the lower strength. This allows the communication device to suppress wireless communication failures while suppressing interference with the wireless communication of other communication devices, thereby improving the communication efficiency of the wireless communication system as a whole. Therefore, the wireless communication system can improve the transport efficiency of the transport vehicle.

[0029] (11) The wireless communication system described in (10), wherein the communication device stores the fourth intensity in the second memory unit as the transmission intensity of the communication device when the interlock communication ends.

[0030] According to the above aspect, in the wireless communication system, the communication devices can more easily perform interlock communication at a radio wave transmission strength appropriate for each communication device by using the radio wave transmission strength of the communication device stored in the second storage unit at the time of ending the interlock communication. This allows the communication devices to improve the communication efficiency of the wireless communication system as a whole. Therefore, the wireless communication system can improve the transport efficiency of the transport vehicle.

[0031] (12) A wireless communication control method executed by a wireless communication system including a transport vehicle that moves along a track and transports an item, and a communication device connected to a port to which the item is delivered by the transport vehicle, wherein the transport vehicle includes a communication unit that performs interlock communication between the transport vehicle and the communication device via wireless communication for the delivery of the item between the transport vehicle and the communication device, a measurement unit that measures a received signal strength of background noise using the communication unit when the transport vehicle is moving upstream of a delivery position where the item is delivered to the port, and a control unit that controls the interlock communication performed by the communication unit, the wireless communication control method determining whether the received signal strength measured by the measurement unit is smaller than a reference value, and (a) if it is determined that the received signal strength is smaller than the reference value, controlling to start the interlock communication while the transport vehicle is moving upstream of the delivery position, and (b) if it is determined that the received signal strength is not smaller than the reference value, controlling to start the interlock communication while the transport vehicle is stopped at the delivery position.

[0032] According to the above aspect, the wireless communication control method provides the same effects as the above wireless communication system.

[0033] The present invention can be realized not only as an apparatus, but also as a method in which the processing means constituting the apparatus are steps, as a program that causes a computer to execute those steps, as a computer-readable recording medium such as a CD-ROM on which the program is recorded, or as information, data, or signals that represent the program.These programs, information, data, and signals may be distributed via a communication network such as the Internet.

[0034] According to the present invention, the wireless communication system can improve the transport efficiency of the transport vehicle.

[0035] FIG. 1 is a schematic diagram showing the configuration of a wireless communication system according to an embodiment. FIG. 2 is a block diagram showing the functional configuration of a wireless communication system according to an embodiment. FIG. 3 is an explanatory diagram showing an example of a table showing the transmission strength of a communication unit of a transporting platform according to an embodiment. FIG. 4 is a flow diagram showing processing of a transporting platform according to an embodiment. FIG. 5 is a flow diagram showing transmission strength adjustment processing of a transporting platform according to an embodiment. FIG. 6 is a flow diagram showing transmission strength adjustment processing of a communication device according to an embodiment. FIG. 7 is a schematic diagram showing a communication method when background noise is relatively small in a wireless communication system according to an embodiment. FIG. 8 is a schematic diagram showing a communication method when background noise is relatively large in a wireless communication system according to an embodiment. FIG. 9 is a schematic diagram showing a communication method in a wireless communication system according to a comparative example. FIG. 10 is an explanatory diagram showing time slots for communication according to a modified example of an embodiment. FIG. 11 is a flow diagram showing processing of a transporting platform according to a modified example of an embodiment.

[0036] Hereinafter, the embodiments will be specifically described with reference to the drawings.

[0037] The embodiments described below each illustrate a preferred specific example of the present invention. The numerical values, shapes, materials, components, component placement and connection configurations, steps, and step order shown in the following embodiments are merely examples and are not intended to limit the present invention. Furthermore, among the components in the following embodiments, components that are not described in the independent claims that represent the highest concept of the present invention will be described as optional components that constitute a more preferred embodiment. Note that the same components will be assigned the same reference numerals, and their description may be omitted.

[0038] (Embodiment) In this embodiment, a wireless communication system that can improve the transport efficiency of a transporting vehicle will be described.

[0039] FIG. 1 is a schematic diagram showing the configuration of a wireless communication system 1 according to the present embodiment.

[0040] As shown in FIG. 1 , the wireless communication system 1 includes a transport vehicle 10 , a loading port 20 , and a control server 30 .

[0041] The wireless communication system 1 is installed in a facility such as a semiconductor factory, and is a transport system in which an article 5 is transported by a transport vehicle 10, and is a system that performs SEMI Standard E84 interlock communication for the delivery of the article 5 between the transport vehicle 10 and a loading port 20. In this system, the SEMI Standard E84 interlock communication is performed wirelessly, and more specifically, is performed by storing a parallel I / O signal (8 bits) on the transport vehicle side and a parallel I / O signal (8 bits) on the device side in a communication frame (also simply referred to as a frame) and wirelessly transmitting and receiving the signals. The SEMI Standard E84 interlock communication of the transport vehicle 10 or the loading port 20 is also generally referred to as interlock processing.

[0042] The wireless communication system 1 may include one or more transport vehicles 10 and one or more loading ports 20. There may also be one or more articles 5. Here, the description will focus on a pair of transport vehicles 10 and loading ports 20 that transfer one article 5.

[0043] The transport vehicle 10 moves along the track 7 and transports the article 5. The transport vehicle 10 can deliver the article 5 to and from the loading port 20 while performing interlock communication with a communication device 22 provided in the loading port 20.

[0044] The track 7 is a track that is fixedly installed in a facility and is a travel path for the transport vehicle 10. The track 7 is installed, for example, on or near the ceiling of the facility. In this case, the movement of the transport vehicle 10 along the track 7 means that the transport vehicle 10 moves while suspended below the track 7, and this case will be described as an example, but the present invention is not limited to this. For example, if the track 7 is installed on the floor surface, the movement of the transport vehicle 10 along the track 7 may mean that the transport vehicle 10 moves along the track on the track installed on the floor surface.

[0045] At a plurality of positions on the track 7, for example, codes (e.g., barcodes or two-dimensional codes) indicating the positions are provided. The transport vehicle 10 is equipped with an encoder so that the travel distance can be measured after the code is read. The transport vehicle 10 can identify its position on the track 7 using the code provided on the track 7 and the encoder equipped thereon. The transport vehicle 10 delivers the article 5 while stopped at a position directly above the loading port 20 on the track 7.

[0046] The position on the track 7 directly above the loading port 20 is referred to as the delivery position. The position where the transport vehicle 10 moving toward the delivery position is located before reaching the delivery position is also referred to as the upstream position. The position where the transport vehicle 10 is located as it moves away from the delivery position after reaching the delivery position is also referred to as the downstream position. In FIG. 1 , it is assumed that the transport vehicle 10 moves from left to right, and in this case, the left is upstream and the right is downstream.

[0047] The loading port 20 is a loading port (also referred to as a load port or port) where the item 5 can be loaded. The loading port 20 is provided in a manufacturing device (e.g., a device that processes the item 5) installed in the facility, and can receive the item 5 from the transport vehicle 10 or pass the item 5 to the transport vehicle 10. The loading port 20 is equipped with at least a loading sensor that can detect whether or not the item 5 is loaded, and uses the loading sensor to obtain information indicating whether or not the item 5 is loaded. Note that the loading port 20 is specified by the SEMI standard to be, for example, 90 centimeters above the floor.

[0048] The loading port 20 is equipped with a communication device 22. The communication device 22 is connected to a connector of the loading port 20. The communication device 22 is disposed, for example, on the top surface of the semiconductor manufacturing equipment. The difference in elevation between the communication device 22 disposed on the top surface of the semiconductor manufacturing equipment and the track 7 is, for example, 3.5 meters. The communication device 22 can transfer the article 5 to and from the transport vehicle 10 while performing interlock communication with the transport vehicle 10.

[0049] The control server 30 is a computer that controls the overall operation of the transporting vehicle 10 of the wireless communication system 1. The control server 30 is connected to the transporting vehicle 10 via various wireless communication methods so as to be able to communicate with the transporting vehicle 10.

[0050] When the item 5 is to be moved to the loading port 20, the control server 30 identifies the loading port 20 to which the item 5 is to be moved, and identifies the transport vehicle 10 that will transport the item 5. The control server 30 then calculates a movement path along which the transport vehicle 10 will move toward the loading port 20. The control server 30 also controls the movement of the transport vehicle 10 along the calculated movement path, and controls the delivery of the item 5 between the transport vehicle 10 and the loading port 20.

[0051] The facility is, for example, a semiconductor manufacturing factory. In this case, the item 5 is, for example, a FOUP (Front Opening Unify Pod) that stores semiconductor wafers. The device installed in the facility is, for example, semiconductor manufacturing equipment. The loading port 20 is provided in the semiconductor manufacturing equipment and can receive the FOUP, which is the item 5, from the transport vehicle 10 and can transfer the FOUP, which is the item 5, to the transport vehicle 10. The track 7 is installed, for example, on the ceiling of the semiconductor manufacturing factory. The transport vehicle 10 is a ceiling-traveling transport vehicle that travels while suspended below the track 7.

[0052] FIG. 2 is a block diagram showing the functional configuration of the wireless communication system 1 according to this embodiment.

[0053] 2, the transporting vehicle 10 includes, as functional units, a communication unit 11, a measurement unit 12, a storage unit 13, a position sensor 14, and a control unit 15. At least some of the functional units included in the transporting vehicle 10 can be realized by a processor (e.g., a CPU (Central Processing Unit)) included in the transporting vehicle 10 executing a program using a memory.

[0054] The communication unit 11 has a wireless communication interface for communication between the transport vehicle 10 and the control server 30, and a wireless communication interface for interlock communication for the transfer of the article 5 between the transport vehicle 10 and the communication device 22. The communication unit 11 establishes a wireless communication link with the communication unit 23 of the communication device 22 and performs interlock communication using wireless communication. The wireless communication interface includes a communication antenna and a wireless circuit. Regarding the communication standards of the wireless communication interface, for example, for communication with the control server 30, wireless LAN interfaces such as the IEEE 802.11a, b, g, n, ac, or ax standards are supported, and for communication with the communication device 22, short-distance wireless interfaces with limited communication distances such as Bluetooth (registered trademark) or BLE (Bluetooth Low Energy) are supported. The same applies hereinafter.

[0055] The interlock process includes pre-transfer process, process during transfer process, and post-transfer process, in this order. The pre-transfer process is a process that is performed before the delivery of the article 5 between the transporting vehicle 10 and the loading port 20. Specifically, parallel I / O signals are sent and received between the transporting vehicle 10 and the loading port 20 via the communication device 22 connected to the transporting vehicle 10 and the loading port 20, to prepare for the transfer of the article 5.

[0056] The transfer process is a process that is carried out in parallel with the transfer of the item 5 between the transport cart 10 and the communication port 20. Specifically, parallel I / O signals are sent and received between the transport cart 10 and the loading port 20 via a communication device 22 connected to the transport cart 10 and the loading port 20, and the FOUP is lowered or raised between the transport cart 10 and the loading port 20.

[0057] The post-transfer processing is a process that is performed after the transfer of the item 5 between the transport cart 10 and the loading port 20. Specifically, parallel I / O signals are sent and received between the transport cart 10 and the loading port 20 via a communication device 22 connected to the transport cart 10 and the loading port 20, completing the transfer processing and completing the interlock processing between the transport cart 10 and the loading port 20.

[0058] Furthermore, the communication unit 11 transmits the value of the transmission strength when the interlock communication with the communication device 22 is successful to the communication device 22 and the control server 30 .

[0059] The measurement unit 12 measures the received signal strength (also referred to as RSSI (Received Signal Strength Indicator)) of the background noise using the communication unit 11. Specifically, the measurement unit 12 measures the RSSI of the background noise using the communication unit 11 while moving upstream from the transfer position. The transfer position is a position that is predetermined as a position where the transport vehicle 10 transfers the item 5 to the loading port 20. The transfer position is, for example, a position directly above the loading port 20. The position from which the measurement unit 12 starts measuring the RSSI is, for example, a position about 2 meters upstream from the transfer position. The measurement unit 12 provides the acquired RSSI of the background noise to the control unit 15.

[0060] The memory unit 13 is a storage device that can store information. The memory unit 13 corresponds to a first memory unit, and stores the transmission strength of radio waves of the communication unit 11. More specifically, the memory unit 13 stores, for each of one or more communication devices 22, the transmission strength of radio waves of the communication unit 11 when the transport vehicle 10 successfully communicates with the communication device 22, in association with the communication device 22. The memory unit 13 corresponds to an example of a first memory unit. Furthermore, the memory unit 13 may store, for each of one or more communication devices 22, a default value (also referred to as default strength) of the transmission strength of radio waves of the communication unit 11 in association with the communication device 22. Furthermore, when the transport vehicle 10 receives, through wireless communication with the control server 30, a default value (also referred to as default intensity) of the transmission strength of radio waves of the communication unit 11, which is stored in the memory unit 32 of the control server 30 in association with each of the one or more communication devices 22, the memory unit 13 may store the default value (also referred to as default intensity) of the transmission strength of radio waves of the communication unit 11. The default intensity may be used as the transmission strength of radio waves of the communication unit 11. Furthermore, the memory unit 13, which serves as a memory unit corresponding to a second memory unit, may store the radio wave transmission strength of each communication device 22 when each communication device 22 communicates with its own device.

[0061] The storage unit 13 may be a volatile storage device such as a dynamic random access memory (DRAM), or a non-volatile storage device such as a hard disk drive (HDD) or a solid state drive (SSD).

[0062] The position sensor 14 is a sensor that measures the position of the transporting vehicle 10. The position sensor 14 can acquire multiple reference positions of the transporting vehicle 10, for example, by reading a code that indicates the position on the track 7. The position sensor 14 provides the acquired reference positions of the transporting vehicle 10 to the control unit 15. An encoder that is part of the control unit 15 calculates position information of the transporting vehicle 10 by measuring the movement distance from the reference position provided by the position sensor 14.

[0063] The control unit 15 controls the interlock communication performed by the communication unit 11. The control unit 15 controls the communication unit 11 to perform the interlock communication while synchronizing with the communication device 22.

[0064] Specifically, the control unit 15 uses the position of the transport vehicle 10 calculated by the position sensor 14 and the encoder of the control unit 15 to control whether to start interlock communication while the transport vehicle 10 is moving upstream from the delivery position or while the transport vehicle 10 is stopped at the delivery position. Starting interlock communication can also be considered as starting pre-transfer processing. Thereafter, the control unit 15 controls the transport vehicle 10 to perform during-transfer processing and post-transfer processing while stopped at the delivery position.

[0065] Specifically, the control unit 15 determines whether the RSSI of the background noise measured by the measurement unit 12 when the transporting vehicle 10 is located upstream of the transfer position is smaller than a reference value. If the control unit 15 determines that the RSSI is smaller than the reference value, it controls to start interlock communication while the transporting vehicle 10 is moving upstream of the transfer position. If the control unit 15 determines that the RSSI is not smaller than the reference value, it controls to start interlock communication while the transporting vehicle 10 is stopped at the transfer position. More specifically, the control to start interlock communication includes an interlock communication process for transmitting and receiving parallel I / O signals between the transporting vehicle 10 and the communication device 22 connected to the loading port 20.

[0066] Furthermore, even if the control unit 15 determines that the RSSI of the background noise is not smaller than the reference value, if the control unit 15 determines that the duration of the period during which the RSSI is smaller than the reference value is longer than a threshold value, the control unit 15 may perform control to start interlock communication while the transporting vehicle 10 is moving upstream of the transfer position. This control will be described in a modified example of the embodiment below.

[0067] The control unit 15 can use a value of about -78 dBm as the reference value. The control unit 15 can use a value that is smaller than the transmission strength of the radio waves transmitted by the communication unit 11 in wireless communication as the reference value. The control unit 15 can use, for example, a value that is a predetermined value smaller than the transmission strength of the radio waves transmitted by the communication unit 11 in wireless communication. The predetermined value can be, for example, about 9 dBm.

[0068] When communication unit 11 performs interlock communication, control unit 15 reads the radio wave transmission strength stored in memory unit 13, memory unit 24, or memory unit 32 (corresponding to a first memory unit) in association with communication device 22, which is the other party in the interlock communication, and controls communication unit 11 to perform interlock communication using the read radio wave transmission strength. The radio wave transmission strength stored in memory unit 13, memory unit 24, or memory unit 32 is, for example, the radio wave transmission strength of communication unit 11 when the previous interlock communication was successful. At this time, control unit 15 can obtain the transmission strength by referring to a table stored in memory unit 13, memory unit 24, or memory unit 32 (see FIG. 3 ).

[0069] Furthermore, the control unit 15 can associate two types of radio wave transmission strengths, namely, the radio wave transmission strength of the communication unit 11 when the interlock communication is successful by communicating with the communication device 22 while the transporting vehicle 10 is moving at a position upstream from the delivery position, and the radio wave transmission strength of the communication unit 11 when the interlock communication is successful by communicating with the communication device 22 while the transporting vehicle 10 is stopped at the delivery position, with the communication device 22 with which the communication is being performed, and store these in the storage unit 13, the storage unit 24, or the storage unit 32 via the communication unit 11. The control unit 15 can then read out the radio wave transmission strength when the previous interlock communication was successful, which is stored in the storage unit 13, the storage unit 24, or the storage unit 32, and control the communication unit 11 to perform interlock communication using the read radio wave transmission strength.

[0070] In addition, at the end of the interlock communication (when the handover with the transport cart 10 is completed), the control unit 15 can associate the transmission strength of the radio waves of the communication unit 11 when the interlock communication is successful with each communication device 22 and store it in the memory unit 13, memory unit 24 or memory unit 32 via the communication unit 11.

[0071] If the control unit 15 cannot read out the radio wave transmission strength stored in the storage unit 13, the storage unit 24, or the storage unit 32 in association with the communication device 22 that is the other party in the interlock communication, the control unit 15 controls the communication unit 11 to perform the interlock communication using a default strength, which is a predetermined transmission strength, as the radio wave transmission strength. The control unit 15 can obtain the default strength by reading out the default strength stored in the storage unit 13, the storage unit 24, or the storage unit 32.

[0072] The control unit 15 can also adjust the transmission strength of the radio waves of the communication unit 11. For example, the control unit 15 causes the communication unit 11 to perform wireless communication at a transmission strength (also referred to as a second strength) that is lower than the transmission strength (also referred to as a first strength) currently used by the communication unit 11 for wireless communication. If the wireless communication performed at the second strength is successful, the control unit 15 sets the transmission strength of the radio waves of the communication unit 11 to the second strength and stores the second strength as the transmission strength of the radio waves in the memory unit 13, the memory unit 24, or the memory unit 32. When the communication unit 11 subsequently performs new interlock communication, the control unit 15 reads out the stored transmission strength (i.e., the second strength) and controls the communication unit 11 to perform the interlock communication using the read transmission strength. Note that whether the wireless communication performed at the second strength is successful can be determined by whether the RSSI of the communication device 22 that received the communication frame transmitted at the second strength is equal to or greater than a reference value and whether the reachability when the communication frame is transmitted at the second strength is higher than a threshold. Here, the arrival rate is the ratio of the number of frames including response data transmitted by the communication device 22 to the number of frames transmitted by the transport vehicle 10 during a predetermined period. The threshold value of the arrival rate can be set, and is, for example, 90%.

[0073] Furthermore, the control unit 15 may adjust the second intensity to be as low as possible among the transmission intensities at which the wireless communication is successful, in order to suppress influence on communications outside the wireless communication system 1.

[0074] Furthermore, when the communication unit 11 performs interlock communication, the control unit 15 reads the radio wave transmission strength stored in the memory unit 13, the memory unit 24, or the memory unit 32 (corresponding to the second memory unit) in association with the communication device 22 that is the other party in the interlock communication, transmits the read radio wave transmission strength to the communication device 22, and controls the communication unit 23 to perform the interlock communication using this transmission strength. As a result, when the radio wave transmission strength of the communication unit 23 is adjusted in interlock communication, when new interlock communication is started thereafter, the radio waves can be transmitted to the transport vehicle 10 at the radio wave transmission strength from the communication device 22 that is stored in the memory unit 13, the memory unit 24, or the memory unit 32 (corresponding to the first memory unit) in association with the communication device 22. At this time, the control unit 15 can obtain the transmission strength by referring to the table stored in the memory unit 13, the memory unit 24, or the memory unit 32.

[0075] 2, the communication device 22 includes, as functional units, a communication unit 23, a storage unit 24, and a control unit 25. At least a part of the functional units included in the communication device 22 can be realized by a processor (e.g., a CPU (Central Processing Unit)) included in the communication device 22 executing a program using a memory.

[0076] The communication unit 23 has a wireless communication interface that performs interlock communication by wireless communication for the delivery of the article 5 between the transporting vehicle 10 and the communication device 22. The communication unit 23 establishes a wireless communication link with the communication unit 11 of the transporting vehicle 10 and performs interlock communication by wireless communication. The configuration and example of the wireless communication interface are the same as those of the communication unit 11. Furthermore, the communication unit 23 transmits the value of the transmission strength when the interlock communication with the transporting vehicle 10 is successful to the transporting vehicle 10 and the control server 30.

[0077] The memory unit 24 is a storage device that can store information. The memory unit 24 serves as a second memory unit and stores the transmission strength of radio waves transmitted by the communication unit 23 to the transporting vehicle 10 when communicating with the transporting vehicle 10, and may also serve as a first memory unit and receive and store the transmission strength of radio waves from the communication unit 11 when the transporting vehicle 10 communicates with its own device. The configuration and examples of the memory unit 24 are the same as those of the memory unit 13 described above.

[0078] The control unit 25 controls the interlock communication performed by the communication unit 23. When the communication unit 23 receives a signal to start interlock communication transmitted by the communication unit 11, the control unit 25 starts interlock communication in synchronization with the transporting vehicle 10 (specifically, the communication unit 11) in accordance with the signal. If the RSSI of the background noise at a position upstream from the transfer position is smaller than a reference value, the control unit 15 of the transporting vehicle 10 starts interlock communication while the transporting vehicle 10 is moving upstream from the transfer position, and if the RSSI is not smaller than the reference value, starts interlock communication while the transporting vehicle 10 is stopped at the transfer position.

[0079] At the end of the interlock communication, the control unit 15 controls the transmission strength of the radio waves of the communication unit 11 when the interlock communication is successful to be stored in the memory unit 13, the memory unit 24 or the memory unit 32, corresponding to each communication device 22.

[0080] In addition, when the communication unit 23 receives the intensity information transmitted by the communication unit 11, the control unit 15 controls the communication unit 23 to perform interlock communication with the communication unit 11 using the transmission intensity of the radio waves indicated in the received intensity information.

[0081] The control unit 15 can adjust the transmission strength of radio waves from the communication unit 11. For example, the communication unit 11 causes the communication unit 11 to perform wireless communication at a transmission strength (also referred to as a fourth strength) that is lower than the transmission strength (also referred to as a third strength) currently used by the communication unit 11 for wireless communication. If the wireless communication performed at the fourth strength is successful, the control unit 25 sets the transmission strength of the radio waves to the fourth strength and, upon completion of interlock communication, controls the fourth strength to be associated with the communication device 22 and stored in the memory unit 13, the memory unit 24, or the memory unit 32. At this time, the control unit 15 transmits strength information indicating the fourth strength to the communication device 22 to store the fourth strength in the memory unit 24 of the communication device 22, or transmits strength information indicating the fourth strength to the control server 30 to store the fourth strength in the memory unit 32 of the control server 30. Whether or not the wireless communication performed at the fourth intensity is successful can be determined by whether or not the RSSI of the communication device 22 that received the communication frame transmitted at the fourth intensity is equal to or greater than a reference value.

[0082] 2, the control server 30 includes, as functional units, a communication unit 31 and a storage unit 32. At least some of the functional units included in the control server 30 can be realized by a processor (e.g., a CPU (Central Processing Unit)) included in the control server 30 executing a program using a memory.

[0083] The communication unit 31 has a communication interface for communicating with the transporting vehicle 10. The communication interface may be a wireless communication interface.

[0084] The storage unit 32 is a storage device that can store information. The configuration and examples of the storage unit 32 are similar to those of the storage unit 13. The storage unit 32 stores the transmission strength of each device when the transport vehicle 10 and the communication device 22 communicate with each other. For example, the storage unit 32 stores strength information indicating a fourth strength transmitted from the control unit 15. Furthermore, the storage unit 32 may store a default strength that is a predetermined transmission strength.

[0085] The control or processing performed by the control unit 15 may be performed by the control unit 25, and the control or processing performed by the control unit 25 may be performed by the control unit 15. Furthermore, the control or processing performed by the control unit 15 or 25 may be performed by both the control units 15 and 25 working together. In this case, communication via the communication units 11 and 23 may be used.

[0086] The table showing the transmission strength of the communication unit 11 of the transporting vehicle 10 will be described below.

[0087] 3 is an explanatory diagram showing an example of a table showing the transmission strength of the communication unit 11 of the transporting platform 10 according to this embodiment. The table shown in FIG. 3 is stored in the storage unit 13, is referred to when the control unit 15 starts interlock communication, and is used to determine the transmission strength of the radio waves of the communication unit 11.

[0088] The table shown in FIG. 3 shows, for each communication device 22, the transmission strength of the radio waves of the communication unit 11 when communicating with that communication device 22, in association with that communication device 22.

[0089] 3, a transmission strength of "-40 dBm" is associated with communication device A, which is an example of communication device 22. By referring to this entry, control unit 15 can determine the transmission strength of radio waves of communication unit 11 to be "-40 dBm" when performing interlock communication with communication device A. The same applies to other communication devices.

[0090] The processing of the wireless communication system 1 configured as above will be described.

[0091] First, the processing of the transport vehicle 10 will be described.

[0092] 4 is a flow diagram showing the processing of the transporting vehicle 10 according to this embodiment. Fig. 4 shows the overall processing flow when the transporting vehicle 10 performs interlock processing (i.e., pre-transfer processing, processing during transfer, and post-transfer processing). The transporting vehicle 10 starts execution of step S101 while moving from an upstream position on the track 7 toward the delivery position.

[0093] In step S101 , the position sensor 14 and the encoder of the control unit 15 calculate the current position of the transporting vehicle 10 .

[0094] In step S102, the control unit 15 determines whether the current position of the transporting vehicle 10 calculated in step S101 by the position sensor 14 and the encoder of the control unit 15 is a position upstream of the transfer position by a predetermined distance. If it is determined that the current position of the transporting vehicle 10 is a position upstream of the transfer position by a predetermined distance (Yes in step S102), the process proceeds to step S103; if not (No in step S102), step S101 is executed again.

[0095] In step S103 , the measurement unit 12 uses the communication unit 11 to measure the RSSI of the background noise.

[0096] In step S104, the control unit 15 determines whether the RSSI of the background noise acquired by the measurement unit 12 in step S103 is smaller than the reference value. If it is determined that the RSSI is smaller than the reference value (Yes in step S104), the process proceeds to step S105. If not (No in step S104), the process proceeds to step S111.

[0097] In step S105, the control unit 15 controls the start of the pre-transfer process when the transport vehicle 10 is moving upstream of the delivery position. The state in which the transport vehicle 10 is moving upstream of the delivery position is a state in which the transport vehicle 10 is moving toward the delivery position, and can also be said to be a state before the transport vehicle 10 reaches the delivery position. The transport vehicle 10 acquires its current position while performing the pre-transfer process while moving, and stops when it reaches the delivery position.

[0098] In step S106, the transport vehicle 10 reaches the delivery position and stops. Here, it is assumed that the transport vehicle 10 continues to perform the pre-transfer process when it reaches the delivery position and stops. Note that if the time required for the pre-transfer process is relatively short, the transport vehicle 10 may reach the delivery position and stop after completing the pre-transfer process.

[0099] In step S107, the control unit 15 ends the pre-transfer process started in step S105.

[0100] In step S108, the control unit 15 executes a transfer process, which is a process following the pre-transfer process executed in steps S105 to S107 in interlock communication.

[0101] In step S109, the control unit 15 executes post-transfer processing. The during-transfer processing is processing following the during-transfer processing executed in step S108 in interlock communication.

[0102] In step S111, the transporting vehicle 10 acquires its current position while moving, and stops when it reaches the delivery position.

[0103] In step S112, the control unit 15 controls the start of pre-transfer processing when the transport vehicle 10 is stopped at the delivery position. The state when the transport vehicle 10 is stopped at the delivery position can also be said to be a state when the transport vehicle 10 has finished moving toward the delivery position.

[0104] In step S113, the control unit 15 ends the pre-transfer process started in step S112.

[0105] 4, in the wireless communication system 1, when the RSSI of the background noise is smaller than a reference value, the transport vehicle 10 can start interlock communication at a position upstream from the transfer position, thereby shortening the time the transport vehicle 10 is stopped at the transfer position. Furthermore, when the received signal strength of the background noise is not smaller than the reference value, the transport vehicle 10 can stop at the transfer position and start interlock communication. This prevents interlock communication from failing due to wireless communication loss caused by the background noise, and contributes to preventing unnecessary wireless communication, such as retransmissions. This allows the wireless communication system 1 to improve the transport efficiency of the transport vehicle 10.

[0106] Fig. 5 is a flow diagram showing the transmission intensity adjustment process of the transporting vehicle 10 according to this embodiment. The transmission intensity adjustment process shown in Fig. 5 is an example of a process that can be performed in the pre-transfer process (step S105 or step S112 in Fig. 4) of the interlock process. Note that the transmission intensity adjustment process shown in Fig. 5 may also be performed in the process during transfer or the process after transfer.

[0107] The transmission intensity of the radio waves transmitted by the communication unit 11 before the processing of FIG. 5 is performed corresponds to the first intensity.

[0108] In step S201, the control unit 15 reduces the transmission intensity of the radio waves transmitted by the communication unit 11. The reduction amount is, for example, −4 dBm to −12 dBm. The reduced transmission intensity corresponds to the second intensity.

[0109] In step S202, the control unit 15 causes the communication unit 11 to transmit one or more frames related to wireless communication at the transmission intensity (i.e., the second intensity) reduced in step S201. The frames transmitted by the communication unit 11 are, for example, frames used for interlock communication. This case will be described as an example, but the frames may also be frames unrelated to interlock communication. The frames transmitted by the communication unit 11 in step S202 are received by the communication device 22 (communication unit 23). Upon receiving the frames, the communication device 22 acquires the RSSI of the received frames (step S211). Then, the communication device 22 transmits response data, which is a response to the received frames, and the RSSI of the acquired frames to the transport vehicle 10 (step S212).

[0110] In step S203, the control unit 15 receives the RSSI transmitted in step S212 via the communication unit 11. The RSSI received by the transporting vehicle 10 is the RSSI of the frame transmitted by the communication device 22 in step S202.

[0111] In step S204, the control unit 15 determines whether the transmission of the frame in step S202 was successful. Specifically, the control unit 15 determines whether the RSSI received in step S203 is equal to or greater than a reference value and whether the arrival rate is equal to or greater than a threshold. Here, the arrival rate is the ratio of the number of frames including response data transmitted by the communication device 22 to the number of frames transmitted by the transport vehicle 10 during a predetermined period. If the control unit 15 determines that the RSSI is equal to or greater than the reference value and the arrival rate is equal to or greater than the threshold (in other words, the frame transmission was successful), the control unit 15 proceeds to step S205; otherwise, the control unit 15 ends the series of processes shown in FIG. 5 .

[0112] In step S205, the control unit 15 stores the transmission intensity (i.e., the second intensity) reduced in step S201 in the storage unit (storage unit 13 or storage unit 32).

[0113] Through the series of processes shown in Figure 5, the transport cart 10 can appropriately adjust the transmission strength of the radio waves transmitted by the communication unit 11, thereby suppressing failures in interlock communication while suppressing interference with wireless communication of other communication devices, and improving the communication efficiency of the wireless communication system 1 as a whole.

[0114] 6 is a flow diagram showing a transmission intensity adjustment process of the communication device 22 according to the present embodiment. The transmission intensity adjustment process shown in FIG. 6 is an example of a process that can be performed in the pre-transfer process of the interlock process. Note that the transmission intensity adjustment process shown in FIG. 6 may also be performed in the process during transfer or the process after transfer.

[0115] The transmission intensity of the radio waves transmitted by the communication unit 23 before the processing of FIG. 6 is performed corresponds to the third intensity.

[0116] In step S301, the communication device 22 reduces the transmission strength of the radio waves transmitted by the communication unit 23 from the transmission strength stored in the storage unit 24. The reduction amount is, for example, −4 dBm to −12 dBm. The reduced transmission strength corresponds to a fourth strength.

[0117] In step S302, the communication unit 23 transmits one or more frames related to wireless communication at the transmission intensity reduced in step S301 (i.e., the fourth intensity). The frames transmitted by the communication unit 23 are, for example, frames used for interlock communication, and this case will be described as an example, but the frames may also be frames unrelated to interlock communication. The frames transmitted by the communication unit 23 in step S302 are received by the transporting vehicle 10 (communication unit 11). Upon receiving the frames, the transporting vehicle 10 acquires the RSSI of the received frames (step S311) and transmits the acquired RSSI to the communication device 22 (step S312).

[0118] In step S303, the communication device 22 receives the RSSI transmitted in step S312. The RSSI received by the communication device 22 is the RSSI of the frame transmitted in step S302.

[0119] In step S304, it is determined whether the RSSI received in step S303 is equal to or greater than a reference value. If it is determined that the RSSI is equal to or greater than the reference value, the process proceeds to step S305; if not, the series of processes shown in FIG. 6 is terminated.

[0120] In step S305, the communication device 22 stores the transmission intensity (i.e., the fourth intensity) reduced in step S301 in the memory unit 24. The transmission intensity stored in the memory unit 24 is stored in the memory unit 32 in the post-transfer processing of the interlock, and can be used in the pre-transfer processing of a new interlock communication that is performed thereafter.

[0121] By the series of processes shown in Figure 6, the communication device 22 can appropriately adjust the transmission strength of the radio waves it transmits, thereby preventing failures in interlock communication and preventing interference with the wireless communication of other communication devices, thereby improving the communication efficiency of the wireless communication system 1 as a whole.

[0122] Hereinafter, a description will be given of a communication method in the wireless communication system 1 while comparing it with a comparative example. The comparative example is an example of a technology in which communication for pre-transfer processing, communication for processing during transfer, and communication for post-transfer processing are performed with the communication device 922 while the transport vehicle 910 is stopped at the delivery position.

[0123] 7 and 8 show a communication method in the wireless communication system 1 according to this embodiment.

[0124] In the wireless communication system 1 according to this embodiment, when the background noise upstream of the transfer position is relatively small, the transport vehicle 10 and the communication device 22 communicate with each other for pre-transfer processing while moving upstream of the transfer position, and then communicate with each other for processing during transfer and post-transfer processing while stopped at the transfer position (see Figure 7).

[0125] In addition, when the background noise at the transfer position is relatively large, the transport vehicle 10 and the communication device 22 communicate with each other regarding pre-transfer processing, processing during transfer, and post-transfer processing while stopped at the transfer position (see Figure 8).

[0126] Fig. 9 is a schematic diagram showing a communication method in a wireless communication system 91 according to a comparative example. A transport vehicle 910 in Fig. 9 is a transport vehicle in the comparative example. A loading port 920 is a location where an article 5 can be loaded in the comparative example. A communication device 922 is connected to the loading port 920, and transfers the article 5 between the transport vehicle 910 and the transport vehicle 910 while performing interlock communication with the transport vehicle 910.

[0127] In the wireless communication system 91 according to the comparative example, the transport cart 910 and the communication device 922 communicate for pre-transfer processing, during-transfer processing, and post-transfer processing while stopped at the transfer position, regardless of the level of background noise (see Figure 9).

[0128] In this way, the transport vehicle 10 of the present embodiment switches between performing communication for the pre-transfer process while moving upstream of the transfer position or while stopped at the transfer position, depending on the level of background noise at a position upstream of the transfer position. As a result, when the background noise at a position upstream of the transfer position is relatively small, communication for the pre-transfer process can be performed while moving upstream of the transfer position, so that in the above case, the time that the transport vehicle 10 is stopped at the transfer position can be shortened compared to the wireless communication system 91 of the comparative example. As a result, overall, the transport vehicle 10 of the present embodiment can shorten the time that it is stopped at the transfer position compared to the wireless communication system 91 of the comparative example, thereby improving transport efficiency.

[0129] (Modification of the embodiment) In this modification, another example of a wireless communication system that can improve the transport efficiency of a transporting vehicle will be described.

[0130] The configuration of the wireless communication system of this modified example is similar to the configuration of the wireless communication system 1 of the above embodiment, but the processing of the transporting vehicle 10 (control unit 15) is partially different. The differences from the wireless communication system 1 of the above embodiment will be described below.

[0131] In this modification, a case will be described in which the transporting vehicle 10 and the communication device 22 perform interlock communication using time-division communication based on time slots.

[0132] FIG. 10 is an explanatory diagram showing time slots for communication according to this modification.

[0133] FIG. 10 shows, with the horizontal axis representing time, wireless channels and time slots that can be used for wireless communication between the transport vehicle 10 and the communication device 22.

[0134] In this modification, the transport vehicle 10 and the communication device 22 perform wireless communication using three wireless channels. The time during which each of the three wireless channels is used for wireless communication is illustrated as "1st ch," "2nd ch," and "3rd ch." The time during which each of the three wireless channels is used for wireless communication is, for example, 10 milliseconds. Furthermore, the usage time of each channel is divided into a plurality of time slots (#1, #2, #3, ...). The time width of one time slot is, for example, 1 millisecond.

[0135] The three channels are selected in a cyclical manner and used for wireless communication. For example, the three channels are selected in the order of "1st ch," "2nd ch," and "3rd ch," and after "3rd ch," "1st ch" is selected again. In this case, the three channels are selected in a cyclical manner and used for wireless communication at a cycle of 30 milliseconds.

[0136] When a pair of transporting vehicles 10 and a communication device 22 perform interlock communication, the time slot to be used for the interlock communication can be determined by the communication performed between the transporting vehicle 10 and the communication device 22.

[0137] For example, the communication device 22 cyclically selects the three channels in order at a predetermined timing for wireless communication. The transport vehicle 10 that is to perform interlock communication with the communication device 22 first transmits frames (also called synchronization frames) continuously on one fixed channel (here, "1st ch") among the three channels.

[0138] When the communication device 22 selects "1st ch" while cyclically using the above three channels, it can receive a synchronization frame transmitted by the transporting vehicle 10. Thereafter, the communication device 22 and the transporting vehicle 10 can periodically communicate in time slots in which the transmission and reception of the synchronization frame was successful. For example, if the communication device 22 receives a synchronization frame transmitted in time slot #1 of the transporting vehicle 10 in time slot #3, thereafter, they can periodically communicate using time slot #1 of the transporting vehicle 10 and time slot #3 of the communication device 22.

[0139] In the wireless communication system 1 that performs time-division communication based on such time slots, even if the RSSI of background noise over a relatively long period of time (more specifically, the average value of the RSSI of background noise over a relatively long period of time) is not smaller than the reference value, if there is a time slot that is not used for other communications, the transport vehicle 10 and the communication device 22 can use the unused time slot to perform interlock communication. The time slot that is not used for other communications can be detected as a period in which the RSSI of background noise is smaller than the reference value.

[0140] Therefore, even if the transport vehicle 10 according to this modification determines that the RSSI of the background noise is not smaller than the reference value, if the transport vehicle 10 determines that the duration of the period during which the RSSI is smaller than the reference value is longer than a threshold value, the transport vehicle 10 performs control to start interlock communication while moving upstream from the transfer position. The threshold value of the duration is, for example, the time width of one time slot (for example, 1 millisecond).

[0141] FIG. 11 is a flowchart showing the processing of the transporting vehicle 10 according to this modified example.

[0142] In FIG. 11, the same processes as those in the above embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0143] In this modified example, when the control unit 15 determines that the RSSI of the background noise measured by the transport cart 10 at a position a predetermined distance upstream from the transfer position is not smaller than the reference value (No in step S104), it determines whether the length of the period during which the RSSI is smaller than the reference value is longer than a threshold value (step S104A).

[0144] If the control unit 15 determines that the length of the period during which the RSSI is smaller than the reference value is longer than the threshold value (Yes in step S104A), it starts the pre-transfer processing while the transport cart 10 is moving upstream (step S105); if not (No in step S104A), it starts the pre-transfer processing while the transport cart 10 is stopped at the delivery position (step S111).

[0145] In this way, even if the RSSI of the background noise received by the transporting vehicle 10 is not smaller than the reference value, if the length of the period during which the RSSI of the background noise is smaller than the reference value is longer than the threshold, the wireless communication system 1 of this modification can start interlock communication within that period, thereby shortening the time that the transporting vehicle is stopped at the delivery position. Thus, the wireless communication system 1 can improve the transport efficiency of the transporting vehicle.

[0146] As described above, in the wireless communication systems of the above-described embodiment and the above-described modification, when the received signal strength of the background noise received by the transport vehicle is smaller than a reference value, it can be determined that the noise level is negligible even if interlock communication using a similar wireless communication is occurring nearby. Therefore, the transport vehicle can start interlock communication at a position upstream from the item transfer position, thereby shortening the time the transport vehicle remains stopped at the transfer position. Furthermore, when the received signal strength of the background noise is not smaller than the reference value, it can be determined that interlock communication using a similar wireless communication is occurring nearby and that the wireless interference is at a level that cannot be ignored. Therefore, by starting stable interlock communication after the transport vehicle stops at the transfer position, it is possible to prevent interlock communication from failing due to wireless communication interference. This allows the wireless communication system to improve the transport efficiency of the transport vehicle. Furthermore, the wireless communication system can improve the quality of wireless communication in interlock communication.

[0147] Furthermore, in the wireless communication system, if the duration of the period during which the received signal strength of the background noise received by the transport vehicle is smaller than a reference value is longer than a threshold, it is determined that there is an available time slot for time division, and the transport vehicle can start interlock communication by time division wireless communication while moving at a position upstream from the transfer position, thereby shortening the time the transport vehicle is stopped at the transfer position. As a result, even if the received signal strength of the background noise received by the transport vehicle is not smaller than the reference value, if the duration of the period during which the received signal strength of the background noise is smaller than the reference value is longer than the threshold, the transport vehicle can start interlock communication within that period, thereby shortening the time the transport vehicle is stopped at the transfer position. In this way, the wireless communication system can improve the transport efficiency of the transport vehicle.

[0148] In addition, in the wireless communication system, the transport vehicle can easily determine the reference value using the transmission strength of the radio waves from the communication unit, and can start interlock communication after making a judgment using the determined reference value. In this way, the wireless communication system can more easily improve the transport efficiency of the transport vehicle.

[0149] Furthermore, in the wireless communication system, the transport vehicle can perform interlock communication at a radio wave transmission strength appropriate for each communication device. If the radio wave transmission strength is less than the required strength, communication loss may occur, causing the interlock communication to fail. Furthermore, if the radio wave transmission strength is greater than required, it may interfere with the wireless communication of other communication devices. By having the transport vehicle perform interlock communication at a radio wave transmission strength appropriate for each communication device, it is possible to prevent failure of interlock communication while also preventing interference with the wireless communication of other communication devices, thereby improving the communication efficiency of the wireless communication system as a whole. Therefore, the wireless communication system can improve the transport efficiency of the transport vehicle.

[0150] Furthermore, in the wireless communication system, the transporting vehicle can more easily perform interlock communication at a radio wave transmission strength appropriate for each communication device by using the radio wave transmission strength when interlock communication is performed while the transporting vehicle is moving and the radio wave transmission strength when interlock communication is performed while the transporting vehicle is stopped. This allows the transporting vehicle to improve the communication efficiency of the wireless communication system as a whole. Therefore, the wireless communication system can improve the transport efficiency of the transporting vehicle.

[0151] Furthermore, in the wireless communication system, the transporting vehicle can more easily perform interlock communication at a radio wave transmission strength appropriate for each communication device by using the radio wave transmission strength of the communication unit stored in the first storage unit at the time of ending the interlock communication. This allows the transporting vehicle to improve the communication efficiency of the wireless communication system as a whole. Therefore, the wireless communication system can improve the transport efficiency of the transporting vehicle.

[0152] Furthermore, in the wireless communication system, when the transport vehicle cannot read out the radio wave transmission strength appropriate for each communication device from the first storage unit, the transport vehicle can perform interlock communication using a default strength. This appropriately avoids a situation where the transport vehicle cannot determine the radio wave transmission strength to be used for interlock communication. Therefore, the wireless communication system can more appropriately improve the transport efficiency of the transport vehicle.

[0153] Furthermore, in the wireless communication system, when the transporting vehicle can perform wireless communication at a lower intensity than the intensity currently used for wireless communication, the transporting vehicle can perform wireless communication at the lowered intensity. This allows the transporting vehicle to suppress wireless communication failures while suppressing interference with wireless communication of other communication devices, thereby improving the communication efficiency of the wireless communication system as a whole. Therefore, the wireless communication system can improve the transport efficiency of the transporting vehicle.

[0154] Furthermore, in the wireless communication system, the communication devices can perform interlock communication with the transport vehicle using radio wave transmission strength appropriate for each communication device. If the radio wave transmission strength is less than the required strength, communication loss may occur, causing the interlock communication to fail. Furthermore, if the radio wave transmission strength is greater than required, it may interfere with the wireless communication of other communication devices. By having the communication devices perform interlock communication using radio wave transmission strength appropriate for each communication device, it is possible to prevent failure of interlock communication while also preventing interference with the wireless communication of other communication devices, thereby improving the communication efficiency of the wireless communication system as a whole. Therefore, the wireless communication system can improve the transport efficiency of the transport vehicle.

[0155] Furthermore, in the wireless communication system, when a communication device can perform wireless communication at a lower strength than the strength currently used for wireless communication, the communication device can perform wireless communication at the lower strength. This allows the communication device to suppress wireless communication failures while suppressing interference with the wireless communication of other communication devices, thereby improving the communication efficiency of the wireless communication system as a whole. Therefore, the wireless communication system can improve the transport efficiency of the transport vehicle.

[0156] Furthermore, in the wireless communication system, the communication devices can more easily perform interlock communication at a radio wave transmission strength appropriate for each communication device by using the radio wave transmission strength of the communication device stored in the second storage unit at the end of the interlock communication. This allows the communication devices to improve the communication efficiency of the wireless communication system as a whole. Therefore, the wireless communication system can improve the transport efficiency of the transport vehicle.

[0157] Although the wireless communication system and the like of the present invention have been described above based on the embodiments, the present invention is not limited to these embodiments. As long as they do not deviate from the spirit of the present invention, various modifications that a person skilled in the art can make to the present embodiments and configurations constructed by combining components of different embodiments are also included within the scope of the present invention.

[0158] The present invention can be applied to a wireless communication system for controlling a transport vehicle that transports articles.

[0159] 1, 91 Wireless communication system 5 Article 7 Track 10, 910 Transporting vehicle 11, 23, 31 Communication unit 12 Measurement unit 13, 24, 32 Storage unit 14 Position sensor 15, 25 Control unit 20, 920 Placement port 22, 922 Communication device 30 Control server

Claims

1. A wireless communication system comprising a transport vehicle that moves along a track to transport an article, and a communication device connected to a port to which the article is delivered by the transport vehicle, wherein the transport vehicle comprises: a communication unit that performs interlock communication between the transport vehicle and the communication device via wireless communication for the delivery of the article between the transport vehicle and the communication device; a measurement unit that measures a received signal strength of background noise using the communication unit when the transport vehicle is moving upstream of a delivery position where the article is delivered to the port; and a control unit that controls the interlock communication performed by the communication unit, wherein the control unit determines whether the received signal strength measured by the measurement unit is smaller than a reference value, and (a) when it determines that the received signal strength is smaller than the reference value, controls to start the interlock communication while the transport vehicle is moving upstream of the delivery position, and (b) when it determines that the received signal strength is not smaller than the reference value, controls to start the interlock communication while the transport vehicle is stopped at the delivery position.

2. The wireless communication system described in claim 1, wherein the control unit, even if it determines in (b) that the received signal strength is not smaller than the reference value, when it determines that the length of time during which the received signal strength is smaller than the reference value is longer than a threshold value, controls to start the interlock communication while the transport vehicle is moving upstream of the transfer position.

3. The wireless communication system according to claim 1, wherein the reference value is smaller than the transmission strength of the radio waves transmitted by the communication unit in the wireless communication.

4. The wireless communication system according to any one of claims 1 to 3, further comprising a first memory unit which stores, for each of one or more communication devices including the communication device, a transmission strength of radio waves of the communication unit when communicating with the communication device, in association with the communication device; and the control unit reads out the transmission strength of radio waves stored in the first memory unit in association with the communication device with which the interlock communication of the communication unit is conducted, and controls the communication unit to conduct the interlock communication using the transmission strength of radio waves which has been read out.

5. The wireless communication system described in claim 4, wherein the radio wave transmission strength stored in the first memory unit includes the radio wave transmission strength when the interlock communication is performed while the transport cart is moving and the radio wave transmission strength when the interlock communication is performed while the transport cart is stopped.

6. The wireless communication system according to claim 4, wherein the control unit causes the first memory unit to store the transmission strength of the radio waves from the communication unit when the interlock communication is terminated.

7. The wireless communication system described in claim 4, wherein when the control unit is unable to read out the radio wave transmission strength stored in the first memory unit corresponding to the communication device with which the communication unit is conducting the interlock communication, the control unit controls the communication unit to perform the interlock communication using a default strength, which is a predetermined transmission strength, as the radio wave transmission strength.

8. The wireless communication system described in claim 4, wherein the control unit causes the communication unit to perform wireless communication at a second intensity which is a transmission intensity lower than a first intensity which is a transmission intensity used by the communication unit for wireless communication, and when the wireless communication performed at the second intensity is successful, sets the transmission intensity of the radio waves of the communication unit to the second intensity, and stores the second intensity in the first memory unit as the transmission intensity of the radio waves.

9. The wireless communication system according to claim 1, further comprising a second memory unit which, for each of one or more communication devices including the communication device, stores, in association with the communication device, the transmission strength of the radio waves of the communication device when the communication device communicates with the communication unit; and when the communication unit starts the interlock communication with the communication device, the control unit reads out the transmission strength of the radio waves stored in the second memory unit in association with the communication device and transmits the read transmission strength of the radio waves to the communication device; and the communication device receives the transmission strength of the transmitted radio waves and performs the interlock communication using the transmission strength of the received radio waves.

10. The wireless communication system described in claim 9, wherein the communication device performs wireless communication at a fourth intensity which is a transmission intensity lower than a third intensity which is a transmission intensity used by the communication device for wireless communication, and if the wireless communication performed by the communication device at the fourth intensity is successful, the control unit sets the transmission intensity of the radio waves to the fourth intensity and stores the fourth intensity in the second memory unit, and when new interlock communication is to be started after the interlock communication has ended, the control unit reads out the transmission intensity of the radio waves stored in the second memory unit in association with the communication device and transmits the read transmission intensity of the radio waves to the communication device, and the communication device receives the transmission intensity of the transmitted radio waves and performs the interlock communication using the transmission intensity of the received radio waves.

11. The wireless communication system according to claim 10, wherein the communication device stores the fourth intensity in the second memory unit as the transmission intensity of the communication device when the interlock communication ends.

12. A wireless communication control method executed by a wireless communication system including a transport vehicle that moves along a track and transports an article, and a communication device connected to a port to which the article is delivered by the transport vehicle, wherein the transport vehicle includes: a communication unit that performs interlock communication between the transport vehicle and the communication device by wireless communication for the delivery of the article between the transport vehicle and the communication device; a measurement unit that measures a received signal strength of background noise using the communication unit when the transport vehicle is moving upstream of a delivery position where the article is delivered to the port; and a control unit that controls the interlock communication performed by the communication unit, wherein the wireless communication control method determines whether the received signal strength measured by the measurement unit is smaller than a reference value, and (a) when it is determined that the received signal strength is smaller than the reference value, controls to start the interlock communication while the transport vehicle is moving upstream of the delivery position, and (b) when it is determined that the received signal strength is not smaller than the reference value, controls to start the interlock communication while the transport vehicle is stopped at the delivery position.

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