Automated Guided Vehicle (AGV) Driving System and Automated Guided Vehicle Driving Control Method

Abstract

Even if wireless communication between the control device and the automated guided vehicle (AGV) is interrupted, the system allows multiple AGVs to smoothly pass through the intersection of the travel lines without stopping before the intersection. [Solution] In the automated guided vehicle (AGV) travel system Sy, the first and second AGVs 31 and 32 request the management device 50 to transmit a semaphore indicating permission to pass through the intersection point G before reaching the intersection point G. The management device 50, for example, transmits a semaphore to the first AGV 31, allowing the first AGV 31 to pass through the intersection point G, while the other AGV temporarily stops at the first position P1 before the intersection point G. If the management device 50 cannot receive semaphore return information from the first AGV 31, the management device 50 transmits a semaphore to the second AGV 32 when an invalidation instruction for the semaphore is input to the operation unit 57, allowing the second AGV 32 to pass through the intersection point G.

Description

Technical Field

[0001] The present invention relates to an automated guided vehicle traveling system and an automated guided vehicle traveling control method that detect a traveling line laid on a road surface and cause an automated guided vehicle to travel along the traveling line. Background Art

[0002] Some automated guided vehicles include a sensor that detects a traveling line laid on a road surface, control the traveling direction of the automated guided vehicle according to the position of the traveling line detected by the sensor to cause the automated guided vehicle to travel along the traveling line, and also control the traveling, stopping, turning, and the like of the automated guided vehicle.

[0003] For example, in the automated guided vehicle described in Patent Document 1, a track line (traveling line) is provided on a floor, a plurality of magnetic marks are sequentially arranged along the track line, the automated guided vehicle is caused to travel along the track line while the track line is detected by a track line detection sensor of the automated guided vehicle, and each time the automated guided vehicle sequentially approaches each magnetic mark, the approaching magnetic mark is detected by one of two mark detection sensors provided on both sides of the automated guided vehicle, the number of marks is counted up, and traveling control of the automated guided vehicle is performed based on a command corresponding to the counted-up number. Prior Art Literature Patent Literature

[0004] Patent Document 1 Japanese Unexamined Patent Application Publication No. 2016-115207 Summary of the Invention Problems to be Solved by the Invention

[0005] In this scenario, where multiple travel lines intersect at a point, and each automated guided vehicle (AGV) travels along its respective line, it is necessary to prevent the AGVs from coming into contact or colliding at the intersection. Therefore, for each AGV, it was temporarily stopped before the intersection, and only after detecting that no other AGV had passed the intersection was the stopped AGV allowed to resume its journey and pass the intersection.

[0006] However, if the wireless communication between the control device and the automated guided vehicle (AGV) is lost even after the AGV has passed the intersection, the control device will not be notified by the AGV that it has passed the intersection and will not be able to permit another AGV to pass the intersection. As a result, an AGV that was not permitted to pass the intersection may become stuck before reaching the intersection.

[0007] This invention has been made in view of the above circumstances, and aims to enable multiple automated guided vehicles to pass smoothly through the intersection of the travel lines without stopping the automated guided vehicles before the intersection, even if wireless communication between the control device and the automated guided vehicles is interrupted. [Means for solving the problem]

[0008] An automated guided vehicle (AGV) travel system according to one aspect of the present invention comprises: a plurality of travel lines laid on the road surface that intersect each other at intersection points; marks provided at positions spaced apart from the intersection points along each travel line; each AGV that travels along the plurality of travel lines; and a management device that transmits a semaphore indicating permission to pass through the intersection points to each AGV, wherein the AGV includes a first communication unit that wirelessly communicates information with the management device, a mark detection unit that detects the marks, and a driving unit for the AGV The system comprises a driving unit that drives the vehicle and a first control unit that controls the driving unit, wherein when the automated guided vehicle is traveling along the travel line and the mark at the second position is detected by the mark detection unit, the first control unit transmits a request for the semaphore from the first communication unit to the management device, and when the semaphore is received by the first communication unit, it continues to drive the automated guided vehicle using the driving unit, and when the automated guided vehicle passes the intersection, it transmits return information indicating the return of the semaphore from the first communication unit to the management device. If the semaphore is not received by the first communication unit, the driving unit stops the automated guided vehicle, and after the semaphore is received by the first communication unit, the driving of the automated guided vehicle is resumed. The management device includes an operation unit into which user instructions are input, a second communication unit for wirelessly communicating information between each of the automated guided vehicles, and when the second communication unit receives a request for a semaphore transmitted from each of the automated guided vehicles, it sends the semaphore to the automated guided vehicle that transmitted the semaphore that was received first among the requests for each semaphore. The system includes a second control unit which transmits a semaphore from the second communication unit, and transmits the semaphore to the other automated guided vehicle when (1) the second communication unit receives the return information from the automated guided vehicle that transmitted the semaphore, or (2) the second communication unit has not received the return information from the automated guided vehicle that transmitted the semaphore, and the wireless communication between the second communication unit and the wireless guided vehicle that transmitted the semaphore has been disconnected, and an instruction to disable the semaphore of the automated guided vehicle that transmitted the semaphore is input to the operation unit.

[0009] Furthermore, an automated guided vehicle (AGV) travel control method according to one aspect of the present invention includes the steps of: driving each AGV along a plurality of travel lines laid on the road surface that intersect each other at intersection points; requesting a semaphore from a management device indicating permission to pass the intersection point when the AGV reaches a predetermined position separated from the intersection point along the travel line; continuing the AGV's movement when the semaphore is received from the management device, and transmitting return information indicating the return of the semaphore to the management device when the AGV passes the intersection point; and stopping the AGV if the semaphore is not received from the management device, and then receiving confirmation that the semaphore is valid. The process includes: restarting the movement of the automated guided vehicle at that point; the management device transmitting the semaphore to the automated guided vehicle that first requested the semaphore, and when the management device receives return information indicating the return of the semaphore, the management device transmitting the semaphore to another automated guided vehicle that has requested the semaphore; and the management device transmitting the semaphore to the other automated guided vehicle when it has not received the return information from the automated guided vehicle that first transmitted the semaphore, and the wireless communication between the management device and the wireless guided vehicle that transmitted the semaphore has been disconnected, and an instruction to disable the semaphore of the automated guided vehicle that transmitted the semaphore is input to the operation unit. [Effects of the Invention]

[0010] According to the present invention, even if wireless communication between the control device and the automated guided vehicle (AGV) is interrupted, multiple AGVs can be smoothly passed through the intersection of the travel line without being stopped before the intersection. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram showing an automated guided vehicle (AGV) travel system according to one embodiment of the present invention. [Figure 2] This is a close-up diagram of an automated guided vehicle (AGV). [Figure 3]This is a plan view showing an enlarged view of the travel line and magnetic mark in the automated guided vehicle travel system of this embodiment. [Figure 4] (A) is a diagram showing the rotation of each drive wheel when the automated guided vehicle (AGV) is moving forward, (B) is a diagram showing the rotation of each drive wheel when the AGV is moving backward, (C) is a diagram showing the rotation of each drive wheel when the AGV is changing direction to the right, and (D) is a diagram showing the rotation of each drive wheel when the AGV is changing direction to the left. [Figure 5] (A) is a diagram showing the rotation of each drive wheel when the automated guided vehicle (AGV) is turned to the right, and (B) is a diagram showing the rotation of each drive wheel when the AGV is turned to the left. [Figure 6] This is a block diagram showing the configuration of an automated guided vehicle and its management system. [Figure 7] This is a map showing the coordinates of the first and second running lines and each magnetic mark. [Figure 8] This figure shows the data table used by the automated guided vehicle (AGV) for its control. [Figure 9] This diagram shows a data table used by a control device for controlling automated guided vehicles (AGVs). [Figure 10] This flowchart shows the control system for smoothly navigating the first and second automated guided vehicles at the intersection. [Figure 11] This diagram shows three or more travel lines intersecting at each intersection point, and each automated guided vehicle traveling along each travel line. [Modes for carrying out the invention]

[0012] Embodiments of the present invention will be described below with reference to the drawings. In the following, directions of rotation or left / right and up / down directions may be indicated, but unless otherwise specified, these indicate directions as examples in each drawing.

[0013] Figure 1 is a schematic diagram showing an automated guided vehicle (AGV) travel system according to one embodiment of the present invention. The AGV travel system Sy shown in Figure 1 comprises a first travel line 11 and a second travel line 12 laid on the road surface and intersecting each other at intersection point G, a plurality of marks 20 arranged on one side of the first travel line 11 and the second travel line 12, a first AGV 31 that travels back and forth along the first travel line 11, a second AGV 32 that travels back and forth along the second travel line 12, and a management device 50. The type of marks 20 is not particularly limited, but in this embodiment, the case in which the marks 20 are magnetic marks will be described as an example. When the marks 20 are not magnetic marks, a sensor capable of detecting the applicable marks will be appropriately used instead of the magnetic sensor 15 described later.

[0014] Figure 2 is a magnified view of the automated guided vehicle (AGV). The AGV is either the first AGV 31 or the second AGV 32 (also simply referred to as the AGV), and both vehicles have the same configuration. The first and second AGVs 31 and 32 are equipped with line sensors 14 that are positioned facing the road surface and detect the first travel line 11 and the second travel line 12 (also simply referred to as the travel line), and magnetic sensors 15 that detect magnetic mark 20. The line sensor 14 includes, for example, an optical sensor such as a CCD (Charge Coupled Device). In this embodiment, an example in which the line sensor 14 includes a CCD will be described.

[0015] Further, as systems in which the automatic guided vehicle travels by reading the first travel line 11 and the second travel line 12 with the line sensor 14 in this manner, there are a magnetic induction system and an optical induction system. In the magnetic induction system, a travel line is formed by attaching a magnetic tape to a floor surface or embedding a magnetic bar, and the automatic guided vehicle travels along the course indicated by the travel line in accordance with the magnetic field of the travel line detected by a magnetic sensor. Also, in the optical induction system, similar to the magnetic induction system, a guide tape (e.g., a vinyl tape) is attached to the floor surface to form a course, and the automatic guided vehicle travels along the course indicated by the travel line detected by light reflection from an optical sensor in response to a semaphore request. In the present embodiment, an example adopting the optical induction system is described. The first travel line 11 and the second travel line 12 are formed of a guide tape such as a vinyl tape.

[0016] In the main body 30A of the first and second automatic guided vehicles 31, 32, the line sensor 14 and the magnetic sensor 15 are arranged side by side along the traveling direction A of the automatic guided vehicle at the center in the width direction of the main body 30A of the automatic guided vehicle. The traveling of the first and second automatic guided vehicles 31, 32 is controlled, for example, in a state where the first travel line 11 or the second travel line 12 is positioned at the center in the width direction thereof. At this time, the position where the magnetic sensor 15 is disposed in the first and second automatic guided vehicles 31, 32 is set such that regardless of whether the vehicle travels in one direction along the first travel line 11 or the second travel line 12 or the opposite direction, any of the marks 20 arranged on both sides of the line at each position of the first travel line 11 and the second travel line 12 can be read. Here, the line sensor 14 is arranged closer to the traveling direction side of the automatic guided vehicle than the magnetic sensor 15, but the arrangement order of the line sensor 14 and the magnetic sensor 15 may be reversed.

[0017] In the first and second automatic guided vehicles 31, 32, steering control is performed according to the position of the travel line detected by the line sensor 14, and controls such as traveling, stopping, and turning of the automatic guided vehicle are performed according to the number of magnetic marks 20 sequentially detected by the magnetic sensor 15.

[0018] Fig. 3 is an enlarged view showing the first and second traveling lines 11, 12 and the magnetic mark 20. As shown in Fig. 3, the first and second traveling lines 11, 12 are belt-shaped and sheet-shaped non-magnetic bodies having a uniform width, and are black or gray. The color or density of the first and second traveling lines 11, 12 has a sufficient difference from the color or density of the road surface.

[0019] The magnetic mark 20 is a sheet-shaped magnetic body. When the automated guided vehicle travels in both one direction along the first and second traveling lines 11, 12 and the opposite direction thereof, the magnetic marks 20 are disposed on both sides of the first and second traveling lines 11, 12. Further, when the automated guided vehicle travels only in one direction along the first and second traveling lines 11, 12, the magnetic mark 20 is disposed on one side of the first and second traveling lines 11, 12. In the present embodiment, a case where the automated guided vehicle travels in both one direction along the first and second traveling lines 11, 12 and the opposite direction thereof will be described. It is preferable that the color or density of the magnetic mark 20 is clearly different from the color or density of the first and second traveling lines 11, 12.

[0020] As shown in Fig. 2, casters (universal casters) 33 are respectively provided at four corners of the bottom of the first and second automated guided vehicles 31, 32, and four driving wheels 34 are spaced apart from each other in a direction orthogonal to the traveling direction A of the automated guided vehicle on the inner side of the bottom of the first and second automated guided vehicles 31, 32, and the shafts of the respective driving wheels 34 are arranged in a straight line. Under the control of a control unit 45 (Fig. 6) described later, each driving wheel 34 is rotationally driven by a respective traveling drive motor, so that the automated guided vehicle travels and each caster 33 is driven to rotate.

[0021] Here, with each drive wheel 34 in contact with the floor, the control unit 45 controls the drive motor of each drive wheel 34, adjusting the rotation speed of the drive wheels 34 and switching the rotation direction of the drive wheels 34, causing the first and second automated guided vehicles 31 and 32 to travel. Steering control is also performed on the first and second automated guided vehicles 31 and 32, thereby changing the direction of travel of the first and second automated guided vehicles 31 and 32, and consequently causing each caster 33 to rotate in response and change its orientation.

[0022] The rotational control of each drive wheel 34 when the first and second automated guided vehicles 31 and 32 are driven will be explained. Figures 4(A) to (D) and 5(A) and (B) show the rotational direction and rotational speed of each drive wheel 34 for each direction of travel of the first and second automated guided vehicles 31 and 32. As mentioned above, the directions shown in the explanation referring to Figures 4 and 5 are for the examples shown in Figures 4 and 5. The rotational control of each drive wheel 34 shown below is performed by the control unit 45.

[0023] As shown in Figure 4(A), when the first and second automated guided vehicles 31 and 32 are moved forward, the four drive wheels 34 are rotated at the same rotational speed in the direction in which the automated guided vehicles move forward (hereinafter referred to as the forward direction).

[0024] As shown in Figure 4(B), when the first and second automated guided vehicles 31 and 32 are moved in reverse, the four drive wheels 34 are rotated at the same rotational speed in the direction in which the automated guided vehicles are moving in reverse (hereinafter referred to as the reverse direction).

[0025] As shown in Figure 4(C), when turning the first and second automated guided vehicles 31 and 32 to the right, the two left drive wheels 34 are rotated in the forward direction, while the two right drive wheels 34 are rotated in the forward direction at a slower rotational speed than each of the left drive wheels 34, or are stopped. At this time, the rotational speed of the left outer drive wheel 34 may be set to be the fastest, the rotational speed of the left inner drive wheel 34 to be the second fastest, the rotational speed of the right inner drive wheel 34 to be the third fastest, and the rotational speed of the right outer drive wheel 34 to be the slowest or stopped. By appropriately setting the rotational speeds of the four drive wheels 34, the turning radius of the automated guided vehicle can be changed.

[0026] As shown in Figure 4(D), when turning the first and second automated guided vehicles 31 and 32 to the left, the two right drive wheels 34 are rotated in the forward direction, while the two left drive wheels 34 are rotated in the forward direction at a slower rotational speed than each of the right drive wheels 34, or are stopped. At this time, the rotational speed of the right outer drive wheel 34 may be set to be the fastest, the rotational speed of the right inner drive wheel 34 to be the second fastest, the rotational speed of the left inner drive wheel 34 to be the third fastest, and the rotational speed of the left outer drive wheel 34 to be the slowest or stopped. By appropriately setting the rotational speeds of the four drive wheels 34, the turning radius of the automated guided vehicle can be changed.

[0027] Furthermore, as shown in Figure 5(A), when the first and second automated guided vehicles 31 and 32 are turned to the right (spin turn) around the pivot center Q of the automated guided vehicles, the two left drive wheels 34 are rotated in the forward direction, while the two right drive wheels 34 are rotated in the opposite direction at the same rotational speed as the two left drive wheels 34. Also, as shown in Figure 5(B), when the first and second automated guided vehicles 31 and 32 are turned to the left (spin turn) around the pivot center Q of the automated guided vehicles, the two right drive wheels 34 are rotated in the forward direction, while the two left drive wheels 34 are rotated in the opposite direction at the same rotational speed as the two right drive wheels 34.

[0028] In this way, the control unit 45 controls the rotational speed and rotational direction of the four drive wheels 34, respectively, thereby enabling the first and second automated guided vehicles 31 and 32 to move forward, backward, change direction to the right or left, and rotate to the right or left. In addition, the four casters 33 change their orientation according to the direction of travel of the first and second automated guided vehicles 31 and 32, stably supporting the first and second automated guided vehicles 31 and 32 so that they can move freely. As a result, despite the simple configuration, it is possible to stably change the orientation of the first and second automated guided vehicles 31 and 32 while they are in motion.

[0029] Although four drive wheels 34 are shown as an example here, it is also possible to configure the system by distributing two drive wheels 34 from the center of the width direction of the main body 30A of the automated guided vehicle (AGV) to the left and right, and controlling the rotation speed and rotation direction of the left and right drive wheels 34 respectively to drive the AGV as described above.

[0030] Figure 6 is a block diagram showing the configuration of the first and second automated guided vehicles 31 and 32 and the management device 50. As shown in Figure 6, the first and second automated guided vehicles 31 and 32 are equipped with a line sensor 14, a magnetic sensor 15, each drive motor 42 that rotates each drive wheel 34, a short-range communication unit 43, a storage unit 44, a control unit 45, a display unit 46, and an operation unit 47 operated by the user.

[0031] As shown in Figure 2, the line sensor 14 is positioned approximately perpendicular to the travel line during the transport of the first and second automated guided vehicles 31 and 32, and optically detects the position of the travel line in the longitudinal direction of the line sensor 14 (the width direction of the main body 30A).

[0032] Furthermore, as shown in Figure 2, the magnetic sensor 15 is positioned in the center of the main body 30A of the first and second automated guided vehicles 31 and 32, and is aligned with the line sensor 14 along the travel direction A of the automated guided vehicle. The magnetic sensor 15 magnetically detects the magnetic mark 20 that is placed on top of the travel line.

[0033] The near-field communication unit 43 is a communication module that transmits and receives control information to and from the management device 50 using a near-field communication method, such as Bluetooth Low Energy (BLE), or Bluetooth®. Alternatively, the near-field communication method used by the near-field communication unit 43 may be WiFi® Direct, a method compliant with the IEEE 802.11 standard, or other methods.

[0034] The memory unit 44 is a volatile memory capable of temporary storage, such as RAM. The memory unit 44 stores control information for the first and second automated guided vehicles 31 and 32, associated with the number of magnetic marks 20 sequentially detected by the magnetic sensor 15. The memory unit 44 also stores either "enabled" or "inactive" information for the semaphore. "Enabled" indicates that the automated guided vehicle is permitted to pass through the intersection point G of the first and second travel lines 11 and 12. "Inactive" indicates that the automated guided vehicle is not permitted to pass through the intersection point G of the first and second travel lines 11 and 12. The control unit 45 receives the control information and the enabled or disabled information from the management device 50 via the short-range communication unit 43 at a predetermined timing before the automated guided vehicle starts traveling, and stores them in the RAM. This control information stored in the memory unit 44 is erased after the power to the automated guided vehicle is turned off.

[0035] Alternatively, instead of this configuration, an HDD or SSD may be used as the storage unit 44, and the control information and the valid information or invalid information may be stored in the storage unit 44 at all times. In this case, the control information and the valid information or invalid information are stored in the storage unit 44 from the time the automated guided vehicle is put into use, and this information continues to be stored even after the power to the automated guided vehicle is turned off.

[0036] The control unit 45 is comprised of a processor, RAM (Random Access Memory), ROM (Read Only Memory), and dedicated hardware circuitry. The processor is, for example, a CPU (Central Processing Unit), an ASIC (Application Specific Integrated Circuit), or an MPU (Micro Processing Unit).

[0037] The control unit 45 executes the above-described controls and processes, including the control of the travel drive motor 42 (an example of a travel drive unit) for moving the first automated guided vehicle 31 or the second automated guided vehicle 32, by operation of the processor according to the control program stored in the memory unit 44. In other words, the control unit 45 comprehensively controls the first automated guided vehicle 31 or the second automated guided vehicle 32. However, the control unit 45 may be configured by hardware circuits such as ASICs instead of operation by a processor according to a control program.

[0038] For example, the control unit 45 controls the rotation speed and direction of each drive motor 42 to adjust the rotation speed and direction of each drive wheel 34. The control unit 45 also transmits and receives control information to and from the management device 50 via the short-range communication unit 43.

[0039] Furthermore, the management device 50 is, for example, a computer or workstation, and includes a short-range communication unit 53, a storage unit 54, a control unit 55, a display unit 56, and an operation unit 57 into which various instructions are input from the user.

[0040] The short-range communication unit 53 is a communication module that transmits and receives control information between the first and second unmanned transport vehicles 31 and 32 using a short-range communication method.

[0041] The storage unit 54 includes an HDD or SSD, etc. The storage unit 54 stores the status of the first and second automated guided vehicles 31 and 32. In addition, the storage unit 54 stores either "enabled" information indicating the semaphore status or "inactive" information indicating the semaphore status separately for the first and second automated guided vehicles 31 and 32.

[0042] The control unit 55 is comprised of a processor, RAM (Random Access Memory), ROM (Read Only Memory), and dedicated hardware circuitry. The processor is, for example, a CPU (Central Processing Unit), an ASIC (Application Specific Integrated Circuit), or an MPU (Micro Processing Unit).

[0043] The control unit 55 comprehensively controls the management device 50 through the operation of the processor in accordance with the control program stored in the memory unit 54. However, the control unit 55 may be configured by hardware circuits such as ASICs instead of relying on the operation of a processor in accordance with the control program.

[0044] For example, the control unit 55 transmits and receives control information between the first and second automated guided vehicles 31 and 32 via the short-range communication unit 53.

[0045] Furthermore, the magnetic mark 20 corresponds to the mark in the claims, and the magnetic sensor 15 corresponds to the mark detection unit in the claims. In addition, the short-range communication unit 43 corresponds to the first communication unit in the claims, and the control unit 45 corresponds to the first control unit in the claims. Also, the short-range communication unit 53 corresponds to the second communication unit in the claims, the control unit 55 corresponds to the second control unit in the claims, and the operation unit 57 corresponds to the operation unit in the claims.

[0046] In the first and second automated guided vehicles 31 and 32 configured as described above, the control unit 45 determines the amount of deviation between the position of the travel line in the longitudinal direction of the line sensor 14 (the width direction of the main body 30A of the automated guided vehicle) detected by the line sensor 14 and the center position of the line sensor 14 (the center position of the main body 30A). The control unit 45 controls the drive motors 42 of each drive wheel 34 to drive so that this amount of deviation becomes "0", thereby changing the orientation of the automated guided vehicle and controlling the automated guided vehicle to travel along the travel line.

[0047] As a result, the center of the main body 30A of the automated guided vehicle (AGV) aligns with the position of the travel line and the magnetic mark 20, and the AGV travels along the travel line and the magnetic mark 20.

[0048] Furthermore, when the automated guided vehicle (AGV) is traveling along the travel line, a magnetic sensor 15 positioned in the center of the width direction of the AGV's main body 30A magnetically detects each magnetic mark 20 superimposed on the travel line in sequence. After the control unit 45 starts the AGV 30 from a preset starting position, each time the magnetic sensor 15 sequentially detects each magnetic mark 20, it counts the number of detected magnetic marks 20, reads the AGV processing corresponding to this counted number of magnetic marks 20 from the storage unit 44, and controls the operation of the AGV based on this read processing. For example, based on the read processing, the control unit 45 controls the rotation speed and rotation direction of the drive motor 42 of each drive wheel 34 to adjust the rotation speed and rotation direction of the drive wheels 34, causing the AGV to move forward, backward, stop, and increase or decrease the AGV's travel speed.

[0049] Here, each magnetic mark 20 is placed on top of the travel line, but it is also possible to place each magnetic mark 20 along the travel line at a certain distance away from the travel line, and place the magnetic sensor 15 at the same certain distance from the center of the main body 30A of the automated guided vehicle, so that when the automated guided vehicle travels along the travel line, the magnetic sensor 15 sequentially detects each magnetic mark 20 arranged along the travel line.

[0050] Figure 7 illustrates a map MP of the road surface on which the first and second automated guided vehicles 31 and 32 travel. In Figure 7 and Figure 11 described later, for the sake of simplicity, the position of the mark 20 is shown as being on the travel line, and the position of the magnetic sensor 15 on the automated guided vehicle is shown as the position corresponding to the mark 20 at that position. As shown in Figure 7, the map MP is in a Cartesian coordinate system, and the coordinates of one end (X1, Y5) and the other end (XA, Y5) of the first travel line 11, the coordinates of one end (X5, Y1) and the other end (X5, YA) of the second travel line 12, and the coordinates of the intersection position G of the first travel line 11 and the second travel line 12 (X5, Y5) are determined by the combination of each position X1 to XA in the X direction and each position Y1 to YA in the Y direction.

[0051] Six coordinates (X1,Y5), (X3,Y5), (X4,Y5), (X6,Y5), (X7,Y5), and (XA,Y5) that overlap with the first travel line 11 have magnetic mark 20s placed there. Similarly, six coordinates (X5,Y1), (X5,Y3), (X5,Y4), (X5,Y6), (X5,Y7), and (X5,YA1) that overlap with the second travel line 12 have magnetic mark 20s placed there.

[0052] As shown in map MP, two coordinates (X4, Y5) and (X6, Y5) located on either side of the intersection point G along the first travel line 11 are designated as first positions P1, and two coordinates (X3, Y5) and (X7, Y5) located further apart from the first positions P1 on either side of the intersection point G are designated as second positions P2. Each first position P1 and each second position P2 is assigned a magnetic mark 20.

[0053] Similarly, two coordinates (X5, Y4) and (X5, Y6) located on either side of the intersection point G along the second travel line 12 are designated as first positions P1, and two coordinates (X5, Y3) and (X5, Y7) located further apart from the first positions P1 on either side of the intersection point G are designated as second positions P2. Each first position P1 and each second position P2 is positioned with its respective magnetic mark 20.

[0054] For example, the first automated guided vehicle 31 starts traveling from coordinates (X1, Y5) at one end of the first travel line 11 under the control of the control unit 45. The control unit 45 of the first automated guided vehicle 31 controls the drive motors 42 of each drive wheel 34 to drive along the first travel line 11 so that the amount of deviation between the position of the first travel line 11 detected by the line sensor 14 and the center position of the line sensor 14 becomes "0". At this time, the control unit 45 of the first automated guided vehicle 31 counts up the number of magnetic marks 20 each time the magnetic sensor 15 detects five coordinates (X3,Y5), (X4,Y5), (X6,Y5), (X7,Y5), and (XA,Y5) that overlap the first travel line 11. When this number reaches "5", that is, when the first automated guided vehicle 31 reaches the other end of the first travel line 11, it reads the control information associated with the number "5" from the storage unit 44. According to this control information, it drives the travel drive motors 42 of each drive wheel 34 to stop the first automated guided vehicle 31, rotate it 180°, make the first automated guided vehicle 31 move forward, and initializes the counted number of magnetic marks 20 "5" to "0".

[0055] After the 180° rotation described above, the control unit 45 of the first automated guided vehicle 31 causes the first automated guided vehicle 31 to travel along the first travel line 11 in the opposite direction to the above, based on the position of the first travel line 11 detected by the line sensor 14. At this time, the control unit 45 of the first automated guided vehicle 31 counts up the number of magnetic marks 20 each time the magnetic sensor 15 detects five coordinates (X7,Y5), (X6,Y5), (X4,Y5), (X3,Y5), and (X1,Y5) that overlap the first travel line 11. When this number reaches "5", that is, when the first automated guided vehicle 31 reaches one end of the first travel line 11, it reads the control information associated with the number "5" from the storage unit 44. According to this control information, it drives the travel drive motors 42 of each drive wheel 34 to stop the first automated guided vehicle 31, rotate it 180°, make the first automated guided vehicle 31 move forward, and initializes the counted number of magnetic marks 20 "5" to "0".

[0056] In this manner, the first automated guided vehicle 31 repeatedly travels back and forth between coordinates (X1, Y5) and coordinates (XA, Y5) along the first travel line 11 under the control of the control unit 45.

[0057] Similarly, the second automated guided vehicle 32 starts traveling from coordinates (X5, Y1) at one end of the second travel line 12 under the control of the control unit 45. The control unit 45 of the second automated guided vehicle 32 makes the second automated guided vehicle 32 travel along the second travel line 12 based on the position of the second travel line 12 detected by the line sensor 14. At this time, the control unit 45 of the second automated guided vehicle 32 counts up the number of magnetic marks 20 each time the magnetic sensor 15 detects five coordinates (X5,Y3), (X5,Y4), (X5,Y6), (X5,Y7), and (X5,YA) that overlap the second travel line 12. When this number reaches "5", and the second automated guided vehicle 32 reaches the other end of the second travel line 12, it reads the control information associated with the number "5" from the storage unit 44. According to this control information, it drives the travel drive motors 42 of each drive wheel 34 to stop the second automated guided vehicle 32, rotate it 180°, make the second automated guided vehicle 32 move forward, and initializes the counted number of magnetic marks 20 "5" to "0".

[0058] After the 180° turn described above, the control unit 45 of the second automated guided vehicle 32 moves the second automated guided vehicle 32 along the second travel line 12 in the opposite direction from before the turn, and each time the magnetic sensor 15 detects one of the five magnetic marks 20 at coordinates (X5,Y7), (X5,Y6), (X5,Y4), (X5,Y3), and (X5,Y1) that overlap the second travel line 12, it counts up the number of magnetic marks 20, and when this number reaches "5" Therefore, when the second automated guided vehicle 32 reaches one end of the second travel line 12, the control information associated with the number "5" is read from the storage unit 44, and according to this control information, the travel drive motors 42 of each drive wheel 34 are driven to stop the second automated guided vehicle 32, rotate it 180°, move the second automated guided vehicle 32 forward, and initialize the counted number of magnetic marks 20 from "5" to "0".

[0059] In this manner, the second automated guided vehicle 32 repeatedly travels back and forth between coordinates (X5, Y1) and coordinates (X5, YA) along the second travel line 12 under the control of the control unit 45.

[0060] As described above, when the first and second automated guided vehicles 31 and 32 are made to travel back and forth along the first and second travel lines 11 and 12, it is necessary to ensure that the first and second automated guided vehicles 31 and 32 do not come into contact or collide at the intersection point G. If the control system is such that the first and second automated guided vehicles 31 and 32 are made to temporarily stop before the intersection point G, and only resume travel after confirming that no other automated guided vehicles have passed the intersection point G, the operational efficiency of each automated guided vehicle will be reduced by temporarily stopping the first and second automated guided vehicles 31 and 32 before the intersection point G.

[0061] Therefore, in this embodiment, when the control units 45 of the first and second automated guided vehicles 31 and 32 that are about to pass through the same intersection point G reach the second position P2 before the intersection point G, they cause the short-range communication unit 43 to send a semaphore request indicating permission to pass through the intersection point G to the management device 50. When the control unit 55 of the management device 50 receives the semaphore request in the short-range communication unit 53, it causes one of the first and second automated guided vehicles 31 or 32, in this case the automated guided vehicle that received the request first, to send a semaphore from the short-range communication unit 53. The control unit 45 of the automated guided vehicle that sent the request first, on the condition that the semaphore is received by the short-range communication unit 43 from the management device 50, drives the travel drive motor 42 to maintain travel without stopping the automated guided vehicle and pass through the intersection point G, and after passing through the intersection point G, it causes the short-range communication unit 43 to send return information indicating the return of the semaphore to the management device 50.

[0062] When the control unit 55 of the management device 50 receives the return information from one of the automated guided vehicles (AGVs) via the short-range communication unit 53, it then instructs the other AGV to transmit a semaphore from the short-range communication unit 53. The control unit 45 of the other AGV temporarily stops it at the first position P1 before the intersection point G until the semaphore is received by the short-range communication unit 43. When the semaphore is received by the short-range communication unit 43 (the above condition is met), the control unit 45 of the other AGV drives the drive motor 42 to move the other AGV and pass through the intersection point G. This allows the AGV that previously requested the semaphore to pass through the intersection point G without being stopped, thus improving the operating efficiency of each AGV.

[0063] However, if short-range communication between the management device 50 and one of the automated guided vehicles (AGVs) is interrupted while the AGV is passing through intersection point G, the control unit 55 of the management device 50 cannot receive return information indicating the return of the semaphore from the AGV using the short-range communication unit 53. Therefore, it cannot transmit the semaphore to the other AGV that is waiting. As a result, the other AGV will remain stopped and stagnant before reaching intersection point G.

[0064] Therefore, in this embodiment, the control unit 55 of the management device 50 selectively executes, depending on the conditions, the following: (1) when the short-range communication unit 53 receives semaphore return information transmitted from one of the automated guided vehicles that is about to pass through the same intersection point, the control unit 55 to transmit the semaphore from the short-range communication unit 53 to the other automated guided vehicle; and (2) when the short-range communication unit 53 has not received return information from the automated guided vehicle that transmitted the semaphore, and wireless communication between the short-range communication unit 53 and the one automated guided vehicle has been disconnected, and an instruction to disable the semaphore of one of the automated guided vehicles is input to the operation unit 57, the control unit 55 to transmit the semaphore from the short-range communication unit 53 to the other automated guided vehicle.

[0065] For example, when the control unit 55 of the management device 50 loses short-range communication with one of the automated guided vehicles and the semaphore return information is not received by the short-range communication unit 53, it first displays information on the display unit 56 indicating the status of the one automated guided vehicle, including that the semaphore status is "enabled," that short-range communication has been lost, and information indicating the identification information of the one automated guided vehicle. At this time, the control unit 45 of the one automated guided vehicle, upon realizing that short-range communication has been lost and the semaphore return information is not transmitted from the short-range communication unit 43, controls the drive motor 42 to stop the one automated guided vehicle.

[0066] The user recognizes the stationary automated guided vehicle (AGV) by visually confirming the semaphore status ("enabled"), the disconnection of short-range communication, and the identification information of one of the AGVs displayed on the display unit 56 of the management device 50. The user can then locate this AGV on the travel line 11 or 12 and perform tasks such as moving it to another location. The user can also input a disable command to the operation unit 57 of the management device 50 to disable the semaphore of the AGV.

[0067] When the user inputs the invalidation instruction to the operation unit 57 of the management device 50, the control unit 55 transmits a semaphore from the short-range communication unit 53 to the other automated guided vehicle (AGV) in accordance with the invalidation instruction. When the control unit 45 of the other AGV receives the semaphore at the short-range communication unit 43, it controls the drive motor 42 to restart the movement of the other AGV and allows it to pass the intersection point G. This prevents the other AGV from becoming stuck and stagnating before reaching the intersection point G.

[0068] Here, as described above, the first and second automated guided vehicles 31 and 32 receive semaphores from the management device 50 and, in order to enable them to travel according to the semaphores, the storage units 44 of the first and second automated guided vehicles 31 and 32 have data tables used for controlling the automated guided vehicles pre-stored. In addition, the storage unit 54 of the management device 50 has another data table used for controlling the automated guided vehicles pre-stored.

[0069] Figure 8 shows a data table pre-stored in the memory unit 44 of the first and second automated guided vehicles 31 and 32 and used for controlling the automated guided vehicles. The data table DT1 shown in Figure 8 stores control information corresponding to the number of magnetic marks 20 detected by the magnetic sensor 15, from "1" to "5". The data table DT1 also stores "enabled" or "disabled" information indicating the semaphore status assigned to its own automated guided vehicle. Furthermore, the data table DT1 stores an intersection position ID indicating the intersection point where the automated guided vehicle crosses another automated guided vehicle on the travel line it is traveling on. In this embodiment, the data table DT1 stores information indicating the intersection position G(X5,Y5) as the intersection position ID. In this embodiment, when the control unit 45 of the first and second automated guided vehicles 31 and 32 starts travel control of the first and second automated guided vehicles 31 and 32, it receives the data table DT1 from the management device 50 via the short-range communication unit 43 and stores it in the memory unit 44.

[0070] For example, the first automated guided vehicle 31 starts traveling from one end (X1, Y5) of the first travel line 11 towards the intersection point G. At this point, the count of magnetic marks 20 by the control unit 45 is reset to "0". When the first automated guided vehicle 31 reaches the coordinates (X3, Y5) of the second position P2, the magnetic marks 20 located at that position are detected by the magnetic sensor 15, and the control unit 45 counts the number of magnetic marks 20 as "1". Similarly, when the second automated guided vehicle 32 starts traveling from one end (X5, Y1) of the second travel line 12 towards the intersection point G and reaches the coordinates (X5, Y3) of the second position P2, the control unit 45 counts the number of magnetic marks 20 detected by the magnetic sensor 15 as "1".

[0071] The data table DT1 stores control information associated with the number of magnetic mark 20, namely "1," including a semaphore request and the transmission of an intersection position ID. The intersection position ID is information indicating the intersection position corresponding to the second position P2 at the location of the automated guided vehicle when the number of marks is counted as "1." In this embodiment, the intersection position information is (X5, Y5).

[0072] When the first automated guided vehicle 31 continues traveling along the first travel line 11 and reaches the coordinates of the first position P1 (X4, Y5) from (X3, Y5), the control unit 45 counts up the number of magnetic marks 20 to "2" due to further detection of magnetic marks 20 by the magnetic sensor 15. Similarly, when the second automated guided vehicle 32 continues traveling along the second travel line 12 and reaches the coordinates of the first position P1 (X5, Y4), the number of magnetic marks 20 detected by the magnetic sensor 15 and counted up by the control unit 45 becomes "2".

[0073] Data table DT1 stores two pieces of control information associated with the number of magnetic mark 20s, which is "2". The two pieces of control information are: (1) "Continue driving" when a semaphore is received, and (2) "Stop driving temporarily and resume driving when a semaphore is received" when a semaphore is not received.

[0074] When the first automated guided vehicle 31 travels along the first travel line 11, passes the intersection point G from (X4, Y5) to (X5, Y5), and reaches the coordinates (X6, Y5) of the next first position P1, the magnetic sensor 15 detects magnetic marks 20, and the control unit 45 counts up the number of detected magnetic marks 20 to "3". Similarly, when the second automated guided vehicle 32 travels along the second travel line 12, passes the intersection point G, and reaches the coordinates (X5, Y6) of the next first position P1, the magnetic sensor 15 detects magnetic marks 20, and the control unit 45 counts up the number of detected magnetic marks 20 to "3".

[0075] The data table DT1 stores the transmission of the semaphore return as control information associated with the number "3" of magnetic mark 20 detected by the magnetic sensor 15.

[0076] When the first automated guided vehicle 31 travels along the first travel line 11 and reaches (X7, Y5), the magnetic sensor 15 detects magnetic marks 20, and the control unit 45 counts up the number of detected magnetic marks 20 to "4". When the second automated guided vehicle 32 travels along the first travel line 12 and reaches (X5, Y7), the magnetic sensor 15 detects magnetic marks 20, and the control unit 45 counts up the number of detected magnetic marks 20 to "4". The data table DT1 does not store control information associated with the number of magnetic marks 20 "4".

[0077] As described above, when the first automated guided vehicle 31 reaches the coordinates (XA, Y5) at the other end of the first travel line 11, the magnetic sensor 15 detects the magnetic marks 20, and the control unit 45 counts up the number of detected magnetic marks 20 to "5". Similarly, when the second automated guided vehicle 32 reaches the coordinates (X5, YA) at the other end of the second travel line 12, the magnetic sensor 15 detects the magnetic marks 20, and the control unit 45 counts up the number of detected magnetic marks 20 to "5". The data table DT1 stores control information associated with the number of magnetic marks 20 "5", including "stopping the automated guided vehicle, turning 180°, traveling (forward), and initializing the number of magnetic marks 20".

[0078] In this manner, magnetic marks 20 are successively detected by the magnetic sensors 15 of each automated guided vehicle (AGV), and control information corresponding to the number of detected magnetic marks 20 is read from the data table DT1. The control units 45 of each AGV then control the movement of the AGV according to the contents indicated by the control information.

[0079] Furthermore, when the first automated guided vehicle 31 starts traveling from the other end (XA, Y5) of the first travel line 11 toward the intersection point G, and the second automated guided vehicle 32 starts traveling from the other end (X5, YA) of the second travel line 12 toward the intersection point G, the magnetic marks 20 are detected sequentially by the magnetic sensors 15 of both automated guided vehicles in the same manner as described above. Control information corresponding to the number of detected magnetic marks 20 is read from the data table DT1, and the control unit 45 controls the movement of the automated guided vehicles according to the contents indicated by the control information.

[0080] Figure 9 shows a data table pre-stored in the storage unit 54 of the management device 50 and used for controlling automated guided vehicles (AGVs). The data table DT2 shown in Figure 9 stores, separately for the first and second AGVs 31 and 32, an intersection position ID indicating the intersection position, the semaphore status ("enabled" or "disabled"), and the operating status of the AGV. The control unit 55 stores the semaphore status in the storage unit 54 in two patterns: (1) all semaphores of the AGVs are "disabled", and (2) the semaphore of one AGV is "enabled" and the semaphores of all other AGVs are "disabled". In other words, the control unit 55 controls the transmission of semaphores to each AGV so that the semaphore status is either (1) or (2) above.

[0081] In the data table DT2 shown in Figure 9, the first and second automated guided vehicles 31 and 32 are used as examples. However, as will be described later, when three or more automated guided vehicles are operated along their respective travel lines, the intersection position ID indicating the intersection point, the semaphore status ("enabled" or "disabled"), and the operating status of the automated guided vehicle are stored separately for each vehicle. The data table DT2 also stores identification information for the first and second automated guided vehicles 31 and 32.

[0082] Next, the control for smoothly moving the first and second automated guided vehicles 31 and 32 at the intersection point G will be explained with reference to the flowchart shown in Figure 10. In the flowchart, the processing of the first and second automated guided vehicles 31 and 32 is shown in S101 to S111, and the processing of the second automated guided vehicle 32 is shown in S201 to S211.

[0083] Assume that the first automated guided vehicle 31 travels back and forth along the first travel line 11, and the second automated guided vehicle 32 travels back and forth along the second travel line 12.

[0084] Here, the first automated guided vehicle 31 is assumed to start traveling from either end of the first travel line 11. At this point, the number of magnetic marks 20 detected by the magnetic sensor 15 stored in the memory unit 44 is assumed to be "0" after being initialized by the control unit 45 (S101).

[0085] As described above with reference to Figures 7 and 8, the configuration of the automated guided vehicle (AGV) travel system Sy is as described above. When the first AGV 31 reaches either end of the first travel line 11, the control unit 45 of the first AGV 31 counts up the number of magnetic marks 20 to "5" based on the detection of magnetic marks 20 by the magnetic sensor 15. The control unit 45 reads the control information associated with the number "5" from the data table DT1, and according to this control information, drives the travel drive motors 42 of each drive wheel 34 to stop the first AGV 31, rotate it 180°, make the first AGV 31 travel forward, and initializes the number of magnetic marks 20 stored in the memory unit 44 to "0". At this time, the semaphore state in the data table DT1 is "inactive".

[0086] Under similar control, the second automated guided vehicle 32 will begin traveling from either end of the second travel line 12. At this point, the number of magnetic marks 20 detected by the magnetic sensor 15 stored in the memory unit 44 will be initialized to "0" by the control unit 45 (S201). The semaphore state in the data table DT1 is "invalid".

[0087] Then, for example, when the first automated guided vehicle 31 starts traveling from one end (X1, Y5) of the first travel line 11 and reaches the coordinates (X3, Y5) of the second position P2, the control unit 45 of the first automated guided vehicle 31 counts up the number of magnetic marks 20 detected by the magnetic sensor 15, reads the control information associated with the number "1" from the data table DT1, and, according to this control information, has the short-range communication unit 43 transmit a semaphore request and an intersection position ID (information indicating (X5, Y5) in this example) along with identification information indicating the first automated guided vehicle 31 to the management device 50 (S102 "Yes"). After this, the control unit 45 determines whether the semaphore has been received by the short-range communication unit 43 (S103).

[0088] Similarly, when the second automated guided vehicle 32 starts traveling from one end (X5, Y1) of the second travel line 12 and reaches the coordinates (X5, Y3) of the second position P2, the control unit 45 of the second automated guided vehicle 32 counts up the number of magnetic marks 20 detected by the magnetic sensor 15 to "1", reads the control information associated with the number "1" from the data table DT1, and, according to this control information, has the short-range communication unit 43 transmit a semaphore request and an intersection position ID (information indicating (X5, Y5) in this example) along with the identification information of the second automated guided vehicle 32 to the management device 50 (S202 "Yes"). After this, the control unit 45 determines whether the semaphore has been received by the short-range communication unit 43 (S203).

[0089] Meanwhile, when the first automated guided vehicle 31 and the second automated guided vehicle 32 start traveling, the control unit 55 of the management device 50 initializes the state of the semaphores of the first and second automated guided vehicles 31 and 32 stored in the data table DT2 to "disabled" (S301). The control unit 55 then determines whether the semaphore request, the crossing position ID, and the identification information of the automated guided vehicles have been received by the short-range communication unit 53 (S302).

[0090] Here, the control unit 55 of the management device 50, if it receives the semaphore request, the intersection position ID, and the identification information of the first automated guided vehicle 31 first (S302 "Yes"), stores the intersection position ID in the data table DT2 in association with the first automated guided vehicle 31, and determines whether there is an automated guided vehicle that has transmitted an intersection position ID that indicates the same intersection position G(X5,Y5) as the intersection position G(X5,Y5) indicated by the said intersection position ID, along with the semaphore request and the identification information of the automated guided vehicle (S303).

[0091] Here, it is assumed that in the management device 50, after the semaphore request, the intersection position ID, and the identification information of the first automated guided vehicle 31 are received by the short-range communication unit 53 from the first automated guided vehicle 31, the semaphore request, the intersection position ID, and the identification information of the second automated guided vehicle 32 are received from the second automated guided vehicle 32.

[0092] In this case, when the control unit 55 receives the semaphore request from the first automated guided vehicle 31, it has not received a semaphore request from the second automated guided vehicle 31, and therefore determines that there is no automated guided vehicle that has sent the semaphore request and identification information along with the intersection position ID indicating the same intersection position G(X5,Y5) (NO in S303). The control unit 55 rewrites the semaphore status of the first automated guided vehicle 31, which sent the semaphore request first, to "enabled" in the data table DT2, and has the short-range communication unit 53 send the semaphore and the intersection position ID indicating the intersection position G(X5,Y5) to the first automated guided vehicle 31 (S305). After this, the process returns to S302.

[0093] On the other hand, when the control unit 55 receives a semaphore request from the second automated guided vehicle 31 after receiving a semaphore request from the first automated guided vehicle 31 (YES in S302), it determines that there is an automated guided vehicle, i.e., the first automated guided vehicle 31, that has transmitted the semaphore request and the identification information of the automated guided vehicle, along with an intersection position ID indicating the same intersection position G(X5,Y5) as the intersection position ID indicated by the intersection position ID (YES in S303).

[0094] At this point, the control unit 55, noting that the semaphore state of the first automated guided vehicle 31, which sent the semaphore request first, is "active" in the data table DT2, and the semaphore state of the second automated guided vehicle 32 is "inactive," rewrites the semaphore state of the second automated guided vehicle 32 to "waiting state" and stores it in the data table DT2 (S306). After this, the process returns to S302.

[0095] Furthermore, in S302, if the control unit 55 determines that it has not received any requests for the semaphore from any of the automated guided vehicles (S302 "No"), it determines whether short-range communication is being performed normally with the automated guided vehicle whose semaphore state is "enabled" (S351). For example, the control unit 55 of the management device 50 communicates periodically with the first automated guided vehicle 31 and the second automated guided vehicle 32 via the short-range communication unit 53 at predetermined short intervals (e.g., 100 msec), and determines that short-range communication is not being performed normally when this communication is interrupted.

[0096] If short-range communication is established between the first and second automated guided vehicles 31 and 32 (S351 "Yes"), the control unit 55 of the management device 50 stores "connected" in the data table DT2, associating it with the first and second automated guided vehicles 31 (S356). If the control unit 55 determines that the semaphore return information and the identification information of the automated guided vehicles have not been received by the short-range communication unit 53 (S307 "No"), the process moves to S302.

[0097] In the first automated guided vehicle 31, when the control unit 45 receives a semaphore and an intersection position ID indicating the intersection position G(X5,Y5) from the management device 50 via the short-range communication unit 43 (S103 "Yes"), it rewrites the semaphore state in the data table DT1, that is, the semaphore state for the intersection position G(X5,Y5), to "enabled" and stores it (S104).

[0098] When the first automated guided vehicle 31 reaches the coordinates (X4, Y5) of the first position P1 on the first travel line 11, the control unit 45 counts up the number of magnetic marks 20 to "2" because the magnetic sensor 15 has detected a second magnetic mark 20, and reads the control information associated with the number "2" from the data table DT1.

[0099] In this case, the control information associated with the number "2" when a semaphore is received is "Continue driving". In this situation, the semaphore state for the intersection position G(X5,Y5) in the data table DT1 of the first automated guided vehicle 31 is "active" and a semaphore has been received. Therefore, the control unit 45 continues driving the first automated guided vehicle 31 according to the control information for when a semaphore is received (S105).

[0100] In contrast, in the second automated guided vehicle 32, when the second automated guided vehicle 32 reaches the coordinates (X5, Y4) of the first position P1 of the second travel line 12, the control unit 45 counts up the number of magnetic marks 20 to "2" because the magnetic sensor 15 detects the second magnetic mark 20, and reads the control information associated with the number "2" from the data table DT1. The control information associated with the number "2" when a semaphore has not been received is "Stop until a semaphore is received, and travel when a semaphore is received". In this situation, since the second automated guided vehicle 32 has not received a semaphore, the control unit 45 controls the travel drive motor 42 according to the control information to temporarily stop the second automated guided vehicle 32 at the coordinates (X5, Y4) of the first position P1 of the second travel line 12 before the intersection position G (S207). In other words, when the second automated guided vehicle 32 reaches the coordinates (X5, Y4) of the first position P1 on the second travel line 12 just before the intersection point G, the management device 50 transmits the semaphore and the intersection point ID (indicating the intersection point G (X5, Y5)) only to the first automated guided vehicle 31, and does not transmit the semaphore and the intersection point ID to the second automated guided vehicle 32.

[0101] Furthermore, when the first automated guided vehicle 31 passes the intersection point G before the second automated guided vehicle 32, which is stopped as described above, and reaches the coordinates (X6, Y5) of the next first position P1 on the first travel line 11, and the magnetic sensor 15 detects the third magnetic mark 20, the control unit 45 counts up the number of magnetic marks 20 to "3" and reads the control information (semaphore return) associated with the number "3" from the data table DT1. According to the control information read, the control unit 45 has the short-range communication unit 43 transmit the return information indicating the semaphore return for the intersection point G (X5, Y5), which is currently "enabled", to the management device 50, along with the identification information of the first automated guided vehicle 31. Then, the control unit 45 rewrites the semaphore state for the intersection point G (X5, Y5) stored in the data table DT1 from "enabled" to "invalid" (S106). After this, the process returns to S102.

[0102] As the first automated guided vehicle 31 continues to move, the magnetic sensor 15 detects the fourth magnetic mark 20 at position (X7, Y5). Subsequently, when the first automated guided vehicle 31 reaches the other end (XA, Y5) of the first travel line 11, the control unit 45 counts up the number of magnetic marks 20 to "5" because the magnetic sensor 15 has detected the fifth magnetic mark 20, and reads the control information associated with the number "5" from the data table DT1. In accordance with the read control information, the control unit 45 stops the first automated guided vehicle 31, rotates it 180°, and makes the first automated guided vehicle 31 move forward. The control unit 45 rewrites (initializes) the stored number of magnetic marks 20 "5" to "0".

[0103] The control unit 55 of the management device 50 repeats the processes of S302, S351, S356, and S307. When the short-range communication unit 53 receives return information and intersection position ID indicating the return of the semaphore (S307 "Yes"), it rewrites the state of the semaphore associated with the received first unmanned transport vehicle 31 in the data table DT2 from "enabled" to "disabled" (S308).

[0104] Then, the control unit 55 of the management device 50 determines whether there is an automated guided vehicle (AGV) whose "operating status" in the data table DT2 is in a waiting state (S309). In this situation, the control unit 55 determines that the "operating status" of the second AGV 32 is in a waiting state (S309 "Yes"), so it deletes the waiting state, which is the "operating status" of the second AGV 32, from the data table DT2 and rewrites the state of the semaphore associated with the second AGV 32 in the data table DT2 to "enabled" (S310). Furthermore, the control unit 45 has the semaphore and the intersection position ID indicating the intersection position G(X5,Y5) transmitted from the short-range communication unit 43 to the second AGV 32 (S310). After this, the process returns to S302.

[0105] After the second automated guided vehicle 32 has come to a complete stop as described above, the control unit 45 of the second automated guided vehicle 32 continues the stopped state of the second automated guided vehicle 32 until it receives a semaphore and an intersection position ID indicating the intersection position G(X5,Y5) from the management device 50 (NO in S208, S207). When the semaphore and the above-mentioned intersection position information transmitted from the management device 50 are received by the short-range communication unit 43 in S310 (YES in S208), the semaphore state in the data table DT1 is rewritten to "enabled" and stored (S209). Upon receiving the semaphore in this manner, the control unit 45 resumes the movement of the second automated guided vehicle 32 based on the control information associated with the number "2" (different control information from the one used in S207) (S210).

[0106] When the second automated guided vehicle 32 passes the intersection point G and reaches the coordinates (X5, Y6) of the next first position P1 on the second travel line 12, the control unit 45 detects that the magnetic sensor 15 has detected the third magnetic mark 20, increments the number of magnetic marks 20 to "3", and reads the control information associated with the number "3" from the data table DT1. In accordance with the read control information, the control unit 45 has the short-range communication unit 43 transmit return information indicating the return of the semaphore, along with the identification information of the second automated guided vehicle 32, to the management device 50, and rewrites the semaphore state in the data table DT1 from "enabled" to "disabled" (S211). After this, the process returns to S202.

[0107] As the second automated guided vehicle 32 continues to move, the magnetic sensor 15 detects the fourth magnetic mark 20 at position (X5, Y7). Subsequently, when the vehicle reaches the other end (X5, YA) of the second travel line 12, the control unit 45 counts up the number of magnetic marks 20 to "5" because the magnetic sensor 15 has detected the fifth magnetic mark 20, and reads the control information associated with the number "5" from the data table DT1. The control unit 45 controls the travel drive motor 42 according to the read control information to stop the second automated guided vehicle 32, rotate it 180°, and make the second automated guided vehicle 32 move forward. The control unit 45 rewrites the stored number of magnetic marks 20 "5" to "0" and initializes it.

[0108] The control unit 55 of the management device 50 repeats steps S302, S351, S356, and S307, and when the short-range communication unit 53 receives return information indicating the return of the semaphore and identification information of the second automated guided vehicle 32 (S307 "Yes"), it rewrites the semaphore status of the second automated guided vehicle 32 in the data table DT2 from "enabled" to "disabled" (S308).

[0109] Then, the control unit 55 of the management device 50 determines whether there are any automated guided vehicles (AGVs) whose "operating status" is "waiting" in the data table DT2 (S309). At this point, there are no AGVs whose "operating status" is "waiting" in the data table DT2, so the control unit 55 determines that there are no AGVs whose "operating status" is "waiting" (S309 "No"). If this determination is made, the process returns to S302.

[0110] Furthermore, if the second automated guided vehicle 32 reaches the second position P2 of the second travel line 12 and sends a semaphore request (YES in S202), and then the first automated guided vehicle 31 reaches the second position P2 of the first travel line 11 and sends a semaphore request, the control device 50 sends a semaphore to the second automated guided vehicle 32 using the same control as described above (S305), and the second automated guided vehicle 32 continues traveling without stopping before the intersection position G based on the reception of the semaphore and passes through the intersection position G (S207~S211). On the other hand, in this case, the first automated guided vehicle 31 does not receive a semaphore from the management device 50 (NO in S103), so it stops temporarily at the first position P1 of the first travel line 11 before the intersection point G (S107). When the second automated guided vehicle 32 passes the intersection point G and transmits return information indicating the return of the semaphore to the management device 50 (S206), the management device 50 transmits a semaphore to the first automated guided vehicle 31 (S310). Based on the reception of the semaphore, the first automated guided vehicle 31 resumes travel (YES in S108, S109, S110) and passes the intersection point G. After passing the intersection point G, the control unit 45 has the short-range communication unit 43 transmit the return information indicating the return of the semaphore, along with the identification information of the first automated guided vehicle 31, to the management device 50, and rewrites the semaphore status in the data table DT1 from "enabled" to "disabled" (S111). After this, the process returns to S102.

[0111] In this embodiment, according to the rules described above, the management device 50 transmits a semaphore to either the first or second automated guided vehicle (AGV) 31 or 32, allowing only one AGV to pass through to the intersection point G, while the other AGV is temporarily stopped at the first position P1 before the intersection point G. When the AGV that has passed through the intersection point G transmits semaphore return information to the management device 50, the management device 50 transmits a semaphore to the other AGV, which then resumes travel and passes through the intersection point G based on the reception of the semaphore. Thus, the first and second AGVs 31 and 32 can pass through the intersection point G without contact or collision, thereby improving the operational efficiency of the first and second AGVs 31 and 32.

[0112] In the above embodiment, the first and travel lines 11 and 12 intersect at an intersection point, and the first and second automated guided vehicles 31 and 32 travel along the first and travel lines 11 and 12. However, the above-described travel control for each automated guided vehicle can also be applied when three or more travel lines intersect at a single intersection point, and three or more wireless transport vehicles travel along each travel line. In this case, when the control unit 55 of the management device 50 receives each semaphore request transmitted from each automated guided vehicle at the short-range communication unit 53, the short-range communication unit 53 transmits a semaphore to the automated guided vehicle that transmitted the semaphore request that was received first. When the short-range communication unit 53 receives return information indicating the return of the semaphore from the automated guided vehicle that transmitted the semaphore in this way, the short-range communication unit 53 transmits the semaphore to one of the other two automated guided vehicles. For example, the control unit 55 of the management device 50 stores the order in which semaphore requests were received for each automated guided vehicle (AGV), and transmits semaphores to each AGV via the short-range communication unit 53 in the order in which the semaphore requests were sent. As described above, the control unit 45 of each AGV transmits the return information from the short-range communication unit 43 to the management device 50 after the AGV has passed the intersection point G.

[0113] Next, the control procedure for the case where, as described above, one automated guided vehicle (AGV) passes through intersection point G, but short-range communication between the management device 50 and the AGV is disconnected, and return information indicating the return of the semaphore is not transmitted from the AGV to the management device 50, will be explained with reference to Figure 10.

[0114] As described above, when the control unit 45 of the first automated guided vehicle 31 receives the semaphore and the identification information of the first automated guided vehicle 31 via the short-range communication unit 43 (S103 "Yes", S104), it controls the drive motor 42 to continue the movement of the first automated guided vehicle 31 (S105). At this time, if the control unit 45 determines that the short-range communication between the management device 50 and the first automated guided vehicle 31 has been disconnected, it controls the drive motor 42 to stop the movement of the first automated guided vehicle 31 at the timing after the first automated guided vehicle 31 has passed the intersection point G. The control unit 45 of the first automated guided vehicle 31 stops the movement of the first automated guided vehicle 31 because it is unable to transmit the semaphore return information and is unable to perform movement control based on communication with the management device 50. For example, the control unit 45 of the first automated guided vehicle 31 communicates periodically with the management device 50 at predetermined short intervals via the short-range communication unit 43, and determines that the short-range communication is not functioning properly when this communication is interrupted.

[0115] Then, the control unit 45 of the first automated guided vehicle 31 displays a warning message indicating that the first automated guided vehicle 31 has stopped moving, as well as identification information of its own automated guided vehicle, on the display unit 46 (S106). For example, when the number of magnetic marks 20 detected by the magnetic sensor 15 is counted to be either "3" or "5", the control unit 45 of the first automated guided vehicle 31 controls the drive motor 42 to stop the first automated guided vehicle 31.

[0116] At this time, the control unit 45 of the second automated guided vehicle 32, which had sent a semaphore request after the first automated guided vehicle 31 had sent the semaphore request, is stopped at the first position P1 of the second travel line 12 just before the intersection position G (S207).

[0117] After the first automated guided vehicle 31 and the second automated guided vehicle 32 start traveling, the control unit 55 of the management device 50 determines in S351 whether communication between the first automated guided vehicle 31 and the second automated guided vehicle 32 is being performed normally. If the control unit 55 determines, for example, that short-range communication with the first automated guided vehicle 31 has been interrupted (S351 "No"), it determines, based on the data table DT2, whether the semaphore state of the automated guided vehicle for which communication is not being performed normally, in this case the first automated guided vehicle 31, is "enabled" (S352). When the control unit 55 determines that the semaphore state of the unmanned transport vehicle (first unmanned transport vehicle 31) whose communication is not functioning properly is "active" (YES in S352), it sets the short-range communication connection status of the unmanned transport vehicle (first unmanned transport vehicle 31) whose communication is not functioning properly to "disconnected" and stores it in the data table DT2 in association with the first unmanned transport vehicle 31 (S353). The control unit 55 of the management device 50 then displays on the display unit 56 a message indicating that the semaphore state of the unmanned transport vehicle (first unmanned transport vehicle 31) whose communication is not functioning properly is "active" and that the short-range communication connection status is "disconnected," for example, identification information indicating the unmanned transport vehicle that sent the semaphore and a message indicating that the semaphore return information is not received due to the communication disconnection (S354).

[0118] Furthermore, if the control unit 55 of the management device 50 determines that the semaphore state of the unmanned transport vehicle (first unmanned transport vehicle 31) for which the above communication is not functioning properly is not "enabled" (NO in S352), it stores "disconnected," indicating that short-range communication has been disconnected, in the data table DT2, associating it with the unmanned transport vehicle (first unmanned transport vehicle 31) for which the above communication is not functioning properly (S356). In this case, the next process is S307.

[0119] In this example, the first automated guided vehicle 31, which is receiving the semaphore signal, is experiencing a communication failure, and the second automated guided vehicle 32 has temporarily stopped while waiting to pass the intersection point G. The control unit 55 may further display a message on the display unit 56 indicating that the first automated guided vehicle 31 has stopped moving, or that both the first and second automated guided vehicles 31 and 32 have stopped.

[0120] This allows the user to visually recognize the malfunction of the first automated guided vehicle (AGV) 31, and furthermore, the fact that both the first and second AGVs 31 and 32 on the travel lines 11 and 12 are stopped. In addition, by looking at the display content of the display unit 56 of the management device 50, the user can identify the AGV that is showing a "semaphore enabled" status and has lost short-range communication with the management device 50, in this case the first AGV 31. The control unit 55 of the management device 50 may highlight the display of the AGV associated with the "semaphore enabled" status and the loss of short-range communication by flashing or other means.

[0121] Furthermore, if the first automated guided vehicle 31 stops as described above, the control unit 45 causes the display unit 46 of the first automated guided vehicle 31 to display a warning message indicating that it is unable to transmit the semaphore return information and that it has stopped moving, as well as identification information of its own automated guided vehicle (S106).

[0122] Since the user can recognize the identification information of the first automated guided vehicle 31 from the display content of the display unit 56 of the management device 50, by comparing the recognized identification information with the identification information displayed on the display unit 46 of the first automated guided vehicle 31, it becomes possible to determine that the automated guided vehicle that is stopped with the semaphore state "enabled" is the first automated guided vehicle 31.

[0123] At this time, for example, the user operates the control unit 47 of the first automated guided vehicle 31 to input a change instruction to change the semaphore state from "enabled" to "disabled". The control unit 45 of the first automated guided vehicle 31 rewrites the semaphore state stored in the data table DT1 from "enabled" to "disabled" in response to the change instruction.

[0124] The user then operates the control unit 57 of the management device 50 to input a disable command to disable the semaphore of the first automated guided vehicle 31. When the disable command is input to the control unit 57 of the management device 50 (S355), the control unit 55 of the management device 50 rewrites the semaphore state associated with the identification information of the first automated guided vehicle 31 in the data table DT2 from "enabled" to "disabled" (S308).

[0125] At this point, the "operating state" associated with the identification information of the second automated guided vehicle 32 in data table DT2 is "waiting state". Therefore, the control unit 55 determines that there are no automated guided vehicles with a "enabled" semaphore state and that the second automated guided vehicle 32 is in a "waiting state" (S309 "Yes"). It then deletes the "waiting state" in the "operating state" associated with the identification information of the second automated guided vehicle 32 in data table DT2, rewrites the semaphore state to "enabled", and further transmits the semaphore and intersection position ID from the short-range communication unit 53 to the second automated guided vehicle 32 (S310). After this, the process moves to S302.

[0126] Upon receiving the above semaphore, the second automated guided vehicle 32's control unit 55 controls the drive motor 42 to resume its movement (YES in S208, S209, S210). After this, the processes described above from S211 onwards are carried out.

[0127] As a result, even if one automated guided vehicle (AGV) is traveling through intersection point G based on semaphore reception and communication with the management device 50 is interrupted, preventing it from sending semaphore return information to the management device 50, the semaphore state of that first AGV can be invalidated. This allows the other AGV, which had been in a standby state, to receive the semaphore from the management device 50 and resume travel, thus preventing the other AGV from stalling before intersection point G. This allows both AGVs to travel smoothly through the intersection point.

[0128] Furthermore, even if the other automated guided vehicle (AGV) receives the semaphore signal before the other AGV, the same control mechanism can be used to prevent the other AGV from becoming stuck before the intersection point G, allowing both AGVs to move smoothly through the intersection point.

[0129] Furthermore, in the case of an unmanned transport vehicle that has stopped moving due to a loss of short-range communication with the management device 50, when short-range communication is restored, it is possible to return the vehicle to the desired position on the travel line, resume movement along the travel line from that position, and perform the control shown in Figure 10.

[0130] Furthermore, when an automated guided vehicle (AGV) stops due to a loss of short-range communication, a warning message and the AGV's identification information are displayed on its display unit 46. However, it is also acceptable to simply display the AGV's identification information on the AGV's main body. Users can see the "enabled" status of the semaphore, the loss of short-range communication, and the AGV's identification information displayed on the display unit 56 of the management device 50 to confirm which AGVs have the same identification information displayed on the display unit 56.

[0131] Furthermore, although the above embodiment illustrates first and second automated guided vehicles 31 and 32, the above-described travel control for each automated guided vehicle can also be applied to a configuration where, as shown in Figure 11, three or more first travel lines 11 and three or more second travel lines 12 intersect at their respective intersection points G, with each first automated guided vehicle 31 traveling along each first travel line 11 and each second automated guided vehicle 32 traveling along each second travel line 11. In this case, the data table DT2 of the management device 50 shown in Figure 9 stores identification information for each first automated guided vehicle 31 and each second automated guided vehicle 32, as well as the semaphore status ("enabled" or "disabled") and the operating status of each automated guided vehicle. Then, at each intersection point G of the first travel line 11 and the second travel line 12, the first automated guided vehicle 31 traveling on the first travel line 11, the first automated guided vehicle 32 traveling on the second travel line 12, and the control device 50 perform travel control of each automated guided vehicle as described above.

[0132] Furthermore, in the above embodiment, a semaphore is transmitted to either the first or second automated guided vehicle (AGV) 31 or 32 to activate the semaphore state, allowing that AGV to pass through the intersection point G, while the other AGV is temporarily stopped at the first position P1 before the intersection point G. When one AGV passes through the intersection point G and the semaphore return information is received by the management device 50, a semaphore is transmitted to the other AGV to resume its movement and allow it to pass through the intersection point G. However, the above-described control of each AGV's movement can also be applied to the configuration shown below.

[0133] For example, even if the system is configured such that both the first and second automated guided vehicles 31 and 32 are temporarily stopped at the first position P1 before the intersection point G, a semaphore is transmitted to one of the automated guided vehicles to activate its state, allowing that vehicle to proceed to the intersection point G, while the other automated guided vehicle is temporarily stopped at the first position P1 before the intersection point G, and when one of the automated guided vehicles passes the intersection point G and the semaphore return information is received by the management device 50, a semaphore is transmitted to the other automated guided vehicle to resume its movement and allow it to pass the intersection point G, the above-described driving control for each automated guided vehicle can still be applied.

[0134] Furthermore, the configuration and processing of the above embodiment described with reference to Figures 1 to 11 are merely one embodiment of the present invention, and the present invention is not intended to be limited to such configuration and processing. [Explanation of Symbols]

[0135] 11. First running line 12. Second running line 14 line sensors 15 Magnetic Sensor 20 Magnetic mark 31. First Automated Transport Vehicle 32. Second Automated Transport Vehicle 33 Casters 34 drive wheels 42. Drive motor 43 Near Field Communication Department 44 Storage section 45 Control Unit 46 Display section 47 Control section 50 Management device 53 Near Field Communication Department 54 Memory section 55 Control Unit 56 Display section 57 Operation section Sy Automated Guided Vehicle Driving System

Claims

1. Multiple driving lines laid on the road surface that intersect each other at intersections, For each of the aforementioned travel lines, a mark is provided at a first position spaced apart from the intersection along the travel line, a second position sandwiching the first position between the intersection and the second position and spaced apart from the intersection along the travel line, and a third position sandwiching the intersection with the second position and spaced apart from the intersection along the travel line. Each of the automated guided vehicles that travels along the aforementioned multiple travel lines, The system includes a management device that transmits a semaphore indicating permission to pass through the aforementioned intersection to each of the automated guided vehicles, The aforementioned unmanned transport vehicle is A first communication unit that wirelessly transmits information to the aforementioned management device, A mark detection unit for detecting the aforementioned mark, A drive unit for moving the aforementioned unmanned transport vehicle, The system includes a first control unit that controls the aforementioned driving unit, The first control unit is, When the automated guided vehicle is traveling along the travel line, and the mark at the second position is detected by the mark detection unit, the semaphore request is transmitted from the first communication unit to the management device. When the semaphore is received by the first communication unit, the driving unit continues to drive the automated guided vehicle, and when the automated guided vehicle passes the intersection and the mark at the third position is detected by the mark detection unit, the first communication unit transmits return information indicating the return of the semaphore to the management device. If the mark at the first position is detected by the mark detection unit without the semaphore being received by the first communication unit, the driving unit stops the movement of the automated guided vehicle, and after the semaphore is received by the first communication unit, the movement of the automated guided vehicle is resumed. When the semaphore is received by the first communication unit and the automated guided vehicle continues to move, if the wireless communication between the first communication unit and the management device is disconnected, the driving unit will stop the movement of the automated guided vehicle when the mark at the third position is detected by the mark detection unit. The aforementioned control device is An operating unit into which user instructions are input, A second communication unit that wirelessly transmits information to each of the aforementioned unmanned transport vehicles, When the second communication unit receives a semaphore request transmitted from each of the aforementioned automated guided vehicles, the second communication unit causes the automated guided vehicle that transmitted the semaphore request that was received first among the aforementioned semaphore requests to transmit the semaphore from the second communication unit. When the second communication unit receives the return information from the automated guided vehicle that sent the semaphore, it transmits the semaphore to another automated guided vehicle that sent the request for the semaphore. An automated guided vehicle (AGV) system comprising: a second control unit that transmits the semaphore to another AGV when the return information from the AGV that transmitted the semaphore has not been received by the second communication unit, and wireless communication between the second communication unit and the AGV that transmitted the semaphore has been disconnected, and an instruction to disable the semaphore of the AGV that transmitted the semaphore is input to the operation unit.

2. The management device includes a display unit, The automated guided vehicle system according to claim 1, wherein the second control unit of the management device causes the display unit to display a state in which the return information has not been received by the second communication unit and the wireless communication between the second communication unit and the automated guided vehicle that transmitted the semaphore has been disconnected.

3. The aforementioned automated guided vehicle is equipped with a display unit, The automated guided vehicle system according to claim 1, wherein the first control unit of the automated guided vehicle causes the first communication unit to display the situation on the display unit when the wireless communication between the first communication unit and the management device is disconnected.

4. A step of driving each automated guided vehicle along multiple driving lines laid on the road surface that intersect each other at intersection points, The steps include: when the automated guided vehicle reaches a predetermined second position separated from the intersection along the travel line, requesting a semaphore from the management device indicating permission to pass the intersection; The steps include: when the automated guided vehicle receives the semaphore from the management device, the automated guided vehicle continues to travel, and when the automated guided vehicle passes the intersection point and reaches a preset third position that is separated from the intersection point along the travel line, flanking the intersection point with the second position, the vehicle transmits return information indicating the return of the semaphore to the management device; The steps include: stopping the movement of the automated guided vehicle when it reaches a preset first position between the intersection point and the second position, separated from the intersection point along the travel line, without receiving the semaphore from the management device, and then resuming the movement of the automated guided vehicle when it receives the semaphore thereafter; When the automated guided vehicle (AGV) has received the semaphore from the management device and is continuing to move, if the wireless communication between the AGV and the management device is disconnected, the AGV stops moving when it reaches the preset third position. The management device transmits the semaphore to the automated guided vehicle that first requested the semaphore, and when the management device receives return information indicating the return of the semaphore, the management device transmits the semaphore to another automated guided vehicle that has requested the semaphore; An automated guided vehicle (AGV) travel control method comprising the step of transmitting the semaphore to another AGV when the management device has not received the return information from the AGV that transmitted the semaphore, and the wireless communication between the management device and the AGV that transmitted the semaphore has been disconnected, and an instruction to disable the semaphore of the AGV that transmitted the semaphore is input to the operation unit.

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