Unmanned transport device and control method thereof

Abstract

To simplify control when an unmanned transport device having a plurality of unmanned transport vehicles travels along a curved portion of a guide line.SOLUTION: An unmanned transport device 1 has a first unmanned transport vehicle 2 on the leading side and a second unmanned transport vehicle 3 on the trailing side, and controls each of the unmanned transport vehicles 2, 3 so that the distance between the two unmanned transport vehicles 2, 3 is constant. When the unmanned transport device 1 travels along a curved portion 22 of a guide line 20, the first unmanned transport vehicle 2 is controlled in a trace travel mode T that makes it follow the guide line 20, and the second unmanned transport vehicle 3 is controlled in an autonomous travel mode N that does not make it follow the guide line 20.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an automated guided vehicle and a control method thereof. [Background technology]

[0002] 2. Description of the Related Art As an automated guided vehicle (AGV) for transporting an object, there is known one that detects a guide line laid on a travel path and travels along the guide line (see, for example, Patent Document 1 below). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5561730 Summary of the Invention [Problem to be solved by the invention]

[0004] When transporting a large or long object, the object may be transported by multiple automated guided vehicles. In this case, it is necessary to control the speed and traveling direction of each automated guided vehicle so that the distance between the multiple automated guided vehicles is constant.

[0005] However, when multiple unmanned guided vehicles are used to transport objects along a curved guide line, it is necessary to keep each unmanned guided vehicle on the curved guide line while maintaining a constant distance between the two unmanned guided vehicles, making the control of each unmanned guided vehicle extremely complicated.

[0006] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to simplify the control of an automated guided vehicle having a plurality of automated guided vehicles when the automated guided vehicle travels along a curved guide line. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a method for controlling an automated guided vehicle having a first automated guided vehicle on a leading side and a second automated guided vehicle on a trailing side that can travel along a guide line provided on a travel path, the method comprising: controlling each of the first and second automated guided vehicles so that a distance between the first and second automated guided vehicles is constant; The present invention provides a method for controlling an unmanned transport device, in which, when the unmanned transport device travels along a curved portion of the guide line, the first unmanned transport vehicle is controlled in a trace travel mode that causes it to follow the guide line, and the second unmanned transport vehicle is controlled in an autonomous travel mode that does not cause it to follow the guide line.

[0008] The present invention also provides an automated guided vehicle having a first automated guided vehicle on a leading side and a second automated guided vehicle on a trailing side that can travel along a guide line provided on a travel path, a control unit provided in the first automated guided vehicle and the second automated guided vehicle controls each of the first automated guided vehicle and the second automated guided vehicle so that a distance between the first automated guided vehicle and the second automated guided vehicle is constant; When the unmanned transport device travels along the curved portion of the guide line, a control unit of the first unmanned transport vehicle controls it in a trace travel mode that causes it to follow the guide line, and a control unit of the second unmanned transport vehicle controls it in an autonomous travel mode that does not cause it to follow the guide line.

[0009] In this way, by controlling the leading first unmanned guided vehicle in a trace driving mode that makes it follow the guide line, while controlling the trailing second unmanned guided vehicle in an autonomous driving mode that does not make it follow the guide line, it is possible to simplify the control for keeping the distance between the two unmanned guided vehicles constant compared to when both unmanned guided vehicles are made to follow the guide line.

[0010] For example, if an unmanned guided vehicle has a connecting part connecting a first unmanned guided vehicle and a second unmanned guided vehicle, the first unmanned guided vehicle and the connecting part are connected to be freely rotatable around a first rotation axis in the vertical direction, and the second unmanned guided vehicle and the connecting part are connected to be freely rotatable around a second rotation axis in the vertical direction, when controlling the second unmanned guided vehicle in an autonomous driving mode, the direction of travel of the second unmanned guided vehicle can be controlled to be parallel to a line connecting the axis of the first rotation axis and the axis of the second rotation axis.

[0011] For example, when an automatic device such as a robot carries an object into or out of the unmanned transport device, it is necessary to stop the unmanned transport device accurately at a predetermined position on the guide line in a predetermined posture. As described above, when the unmanned transport device is made to travel along the curved portion of the guide line, if the second unmanned transport vehicle is made to travel autonomously without following the guide line, the second unmanned transport vehicle will deviate from the guide line, and it is necessary to return the second unmanned transport vehicle to the guide line before it reaches the stop position. For example, when a straight section is provided after the curved portion of the guide line, the first unmanned transport vehicle on the leading side is made to travel along the straight section of the guide line, so that the second unmanned transport vehicle on the trailing side gradually approaches the guide line. However, in order to place the second unmanned transport vehicle on the guide line, it is necessary to travel a considerable distance along the straight section, so that the stop position can only be set at a position away from the curved portion, which limits the layout of the facility.

[0012] Therefore, while the first unmanned guided vehicle is traveling along the straight section following the guide line, the control of the second unmanned guided vehicle can be switched from an autonomous driving mode to a tracing driving mode in which the second unmanned guided vehicle traces and follows the guide line, thereby enabling the second unmanned guided vehicle to return to the guide line quickly.

[0013] In this case, it is necessary to control both automated guided vehicles to keep the distance between them constant while making them follow the guide line, and the problem of complicated control resurfaces. Therefore, it is preferable to switch the control of the second automated guided vehicle from the autonomous driving mode to the trace driving mode after the automated guided vehicle starts to decelerate toward the stop position. In this way, when the automated guided vehicle travels at a low speed, it is relatively easy to control the distance between both automated guided vehicles to be constant even when both automated guided vehicles are made to follow the guide line. Effect of the Invention

[0014] As described above, according to the present invention, it is possible to simplify the control of an automatic guided vehicle having a plurality of automatic guided vehicles when the automatic guided vehicle travels along a curved guide line. [Brief description of the drawings]

[0015] [Figure 1] FIG. [Diagram 2] FIG. 2 is a side view of the unmanned transport device. [Diagram 3] 1 is a plan view showing a state in which the above-mentioned unmanned transport device travels along a straight portion on the upstream side of the guide line. FIG. [Figure 4] FIG. 4 is a plan view showing a state in which the above-mentioned unmanned transport device travels along a curved portion of a guide line. [Diagram 5] 10 is a plan view showing a state in which the above-mentioned unmanned transport device travels along a straight portion on the downstream side of the guide line. FIG. [Figure 6] 10 is a plan view showing a state in which the above-mentioned unmanned transport device travels along a straight portion on the downstream side of the guide line. FIG. [Figure 7] 4 is a plan view showing a state in which the unmanned transport device is stopped at a predetermined stop position. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0017] 1 and 2 includes a first automated guided vehicle 2, a second automated guided vehicle 3, and a carriage 4 as a connector that connects these vehicles. Each of the automated guided vehicles 2, 3 and the carriage 4 are connected via a vertical rotation shaft 5. This allows each of the automated guided vehicles 2, 3 to rotate freely around the rotation shaft 5 relative to the carriage 4. The rotation shaft 5 is fixed to the carriage 4 via a bracket 6, and is rotatably supported by bearings (not shown) provided on the automated guided vehicles 2, 3.

[0018] Each of the automated guided vehicles 2 and 3 has left and right wheels 8, a motor 9 that rotates and drives each wheel 8, a rotation speed detection unit (not shown) that detects the rotation speed of each wheel 8, a camera 10 as a line detection unit, an angle detection unit 11 that detects the rotation angle of the rotating shaft 5, a control unit 12 that controls the motor 9, and a battery (not shown) that supplies power to the motor 9, the rotation speed detection unit, the camera 10, the angle detection unit 11, and the control unit 12. The control unit 12 is connected to the motor 9, the rotation speed detection unit, the camera 10, and the angle detection unit 11.

[0019] The left and right wheels 8 are each independently controlled by a motor 9. The traveling speed of the automated guided vehicles 2, 3 can be controlled by adjusting the rotational speed of both wheels 8. In addition, the steering angle of each automated guided vehicle 2, 3, i.e., the rotation angle of each automated guided vehicle 2, 3 around the rotation axis 5 relative to the carriage 4, can be controlled by adjusting the difference in rotational speed between the left and right wheels 8 of each automated guided vehicle 2, 3.

[0020] The camera 10 detects the position of the guide line 20 (see FIG. 3) laid on the floor surface of the road. In this embodiment, the image captured by the camera 10 is transmitted to the control unit 12, and the position and posture of the guide line 20 are obtained from this image. The guide line 20 is made of a material that can be identified when captured in the image of the camera 10, for example, a light-reflecting tape. Alternatively, the guide line 20 may be made of magnetic tape, and the line detection unit that detects it may be configured with a magnetic detector.

[0021] The angle detection unit 11 detects the rotation angle of each of the automated guided vehicles 2, 3 relative to the cart 4. In this embodiment, the angle detection unit 11 detects the rotation angle of the rotation shaft 5 relative to the automated guided vehicles 2, 3. This detection result is transmitted to the control unit 12, whereby the attitude (steering angle) of the automated guided vehicles 2, 3 relative to the cart 4 can be obtained.

[0022] The control unit 12 of the first automated guided vehicle 2 and the control unit 12 of the second automated guided vehicle 3 are connected to each other so that they can communicate with each other. Therefore, for example, information detected by the camera 10 of the first automated guided vehicle 2 (for example, information on an event display unit installed on the floor surface) is transmitted not only to the control unit 12 of the first automated guided vehicle 2 but also to the control unit 12 of the second automated guided vehicle 3.

[0023] Next, a control method for transporting a vehicle body by the above-mentioned automated guided transport device 1 in an automobile assembly line will be described with reference to Figures 3 to 7. In this assembly line, a vehicle body is loaded onto the carriage 4 of the automated guided transport device 1, and various parts are assembled onto the vehicle body while the vehicle body is being transported by the automated guided transport device 1. Note that in Figures 3 to 7, the carriage 4 of the automated guided transport device 1 is simplified, and the vehicle body loaded onto it is omitted.

[0024] The guide line 20 has a straight section 21, a curved section 22 smoothly continuing on the downstream side thereof, and a straight section 23 smoothly continuing further downstream thereof (see FIG. 3). A plurality of event display units are provided near the guide line 20. In this embodiment, event display units 31-34 are provided at the boundary between the upstream straight section 21 and the curved section 22, the boundary between the curved section 22 and the downstream straight section 23, and at the deceleration start position and stop position Q of the automatic guided device 1 on the downstream straight section 23. Each of the event display units 31-34 is provided within the detectable range of the camera 10 of the automatic guided vehicles 2, 3 traveling along the guide line 20. The event display units 31-34 are formed of, for example, two-dimensional barcodes.

[0025] As shown in Figure 3, when both unmanned guided vehicles 2 and 3 are traveling on the straight section 21 upstream of the guide line 20, the first unmanned guided vehicle 2 on the leading side is controlled in trace driving mode T, and the second unmanned guided vehicle 3 on the trailing side is controlled in autonomous driving mode N.

[0026] In the trace travel mode T, an automatic guided vehicle (here, the first automatic guided vehicle 2) is controlled to follow the guide line 20 while traveling at a predetermined speed. Specifically, the control unit 12 of the first automatic guided vehicle 2 acquires the position of the width direction center of the guide line 20 from the image of the camera 10, and calculates the amount of deviation in the width direction (direction perpendicular to the guide line 20) between the width direction center of the guide line 20 and the center P1 (for example, the axis of the rotation shaft 5) of the first automatic guided vehicle 2. By controlling each motor 9 to adjust the difference in the number of rotations of the left and right wheels 8 so as to reduce the amount of deviation, the first automatic guided vehicle 2 can be made to always travel along the guide line 20.

[0027] In the autonomous driving mode, an autonomous guided vehicle (here, the second autonomous guided vehicle 3) is controlled to drive autonomously without following the guide line 20. In this embodiment, the control unit 12 of the second autonomous guided vehicle 3 controls the rotation speed of each motor 9 so as to maintain a constant distance between the second autonomous guided vehicle 3 and the first autonomous guided vehicle 2. In addition, the rotation speed of each motor 9 of the second autonomous guided vehicle 3 is controlled so that the traveling direction of the second autonomous guided vehicle 3 (the horizontal direction perpendicular to the axis of the wheels 8, 8) is parallel to the center line L of the carriage 4 (the straight line connecting the axis of the rotation shafts 5, 5 connecting the carriage 4 and the autonomous guided vehicles 2, 3).

[0028] On the straight portion 21 on the upstream side of the guide line 20, the first automated guided vehicle 2 runs linearly along the straight portion 21, so that the center line L of the carriage 4 and the running direction of the first automated guided vehicle 2 are parallel. Therefore, by controlling the traveling direction of the second automated guided vehicle 3 to be parallel to the center line L of the carriage 4, the second automated guided vehicle 3 also runs linearly along the straight portion 21. As a result, both automated guided vehicles 2, 3 run along the straight portion 21 of the guide line 20.

[0029] When the camera 10 of the first automated guided vehicle 2 detects the event display unit 31, this detection signal is transmitted to the control unit 12. At this time, each control unit 12 may control the motor 9 of each automated guided vehicle 2, 3 so as to change (e.g., slow down) the traveling speed of each automated guided vehicle 2, 3.

[0030] 4, when the first automated guided vehicle 2 travels following the curved section 22 of the guide line 20, if the second automated guided vehicle 3 were also made to travel following the guide line 20, the control for maintaining a constant distance between the two automated guided vehicles 2, 3 would become extremely complicated. In this embodiment, as described above, the second automated guided vehicle 3 is controlled in an autonomous travel mode that does not follow the guide line 20, and therefore the control for running the second automated guided vehicle 3 while maintaining a constant distance from the first automated guided vehicle 2 is simplified.

[0031] At this time, the first automated guided vehicle 2 curves to follow the curved portion 22 of the guide line 20, so that the center line L of the carriage 4 is inclined with respect to the straight portion 21. The second automated guided vehicle 3 is controlled to run parallel to the center line L of the carriage 4, so it runs off the straight portion 21 of the guide line 20 (see FIG. 4). In other words, the second automated guided vehicle 3 operates like the rear wheels of a normal vehicle, and runs inside the curved portion 22 of the guide line 20 (towards the center of curvature).

[0032] Thereafter, when the camera of the first automated guided vehicle 2 detects the event display unit 32, this detection signal is transmitted to the control unit 12. At this time, each control unit 12 may control the motor 9 of each automated guided vehicle 2, 3 so as to change (e.g., increase) the traveling speed of each automated guided vehicle 2, 3.

[0033] 5, as the first unmanned guided vehicle 2 travels along the straight section 23, the angle θ between the traveling direction of the first unmanned guided vehicle 2 (i.e., the extension direction of the straight section 23) and the center line L of the carriage 4 gradually decreases, and as a result, the second unmanned guided vehicle 3 approaches the straight section 23. However, in order for the center P2 of the second unmanned guided vehicle 3 to be located on the straight section 23, the second unmanned guided vehicle 3 needs to travel a fairly long distance along the straight section 23. In this case, the stopping position Q needs to be located quite far away from the curved section 22, which places restrictions on the layout of the facility.

[0034] Therefore, in this embodiment, while the first automated guided vehicle 2 is traveling on the straight section 23 on the downstream side of the guide line 20, the control of the second automated guided vehicle 3 is switched from the autonomous travel mode N to the trace travel mode T (see FIG. 6). The second automated guided vehicle 3 switched to the trace travel mode T is controlled to follow the guide line 20 while maintaining a constant distance from the first automated guided vehicle 2. Specifically, the control unit 12 of the second automated guided vehicle 3 calculates the amount of deviation in the width direction between the center of the width direction of the guide line 20 detected based on the image of the camera 10 and the center P2 of the second automated guided vehicle 3. By controlling each motor 9 to adjust the difference in the number of revolutions between the left and right wheels 8 so as to reduce the amount of deviation, the center P2 of the second automated guided vehicle 3 is placed on the guide line 20 early.

[0035] At this time, both unmanned guided vehicles 2, 3 are controlled to follow the guide line 20 while maintaining a constant distance between them, which re-emerges the problem of complicated control of these unmanned guided vehicles 2, 3 (especially the trailing unmanned guided vehicle 3).

[0036] Therefore, in this embodiment, as shown in Fig. 6, after the camera 10 of the first automated guided vehicle 2 detects the event display unit 33 and both automated guided vehicles 2 and 3 start to decelerate, the control of the second automated guided vehicle 3 is switched from the autonomous driving mode N to the trace driving mode T. In this embodiment, after the guide line 20 enters the detectable range of the camera 10 of the second automated guided vehicle 3 traveling in the autonomous driving mode N, the control of the second automated guided vehicle 3 is switched from the autonomous driving mode N to the trace driving mode T. In this way, when the automated guided device 1 travels at a low speed, the control for maintaining a constant distance between both automated guided vehicles 2 and 3 is relatively simple, even when both automated guided vehicles 2 and 3 are controlled in the trace driving mode.

[0037] Thereafter, the automated guided vehicle 1 continues to decelerate toward the stop position Q, and when the first automated guided vehicle 2 detects the event display unit 34, both automated guided vehicles 2, 3 stop at the stop position Q (see FIG. 7). At this time, since the centers P1, P2 of both automated guided vehicles 2, 3 are disposed on the guide line 20, the automated guided device 1 can be accurately stopped at the stop position Q in a predetermined posture. Thereafter, an automatic device such as a robot carries the transported object (vehicle body) into the cart 4, or carries the transported object (vehicle body) out of the cart 4.

[0038] Incidentally, when a plurality of unmanned guided vehicles transport an object, it is preferable to grasp the relative position and posture of one unmanned guided vehicle with respect to the other unmanned guided vehicle. For example, if an expensive detection device (e.g., Lidar) is provided in one unmanned guided vehicle for detecting the position and posture of the other unmanned guided vehicle, the cost of the unmanned guided vehicle increases. In contrast, in the unmanned guided vehicle 1 described above, the angle detection unit 11 detects the rotation angle of each of the unmanned guided vehicles 2 and 3 with respect to the carriage 4, and the relative angle (posture) of the unmanned guided vehicles 2 and 3 can be detected from these angles. This makes it possible to grasp the relative position and posture of the plurality of unmanned guided vehicles 2 and 3 without requiring an expensive detection device.

[0039] The present invention is not limited to the above embodiment. Other embodiments of the present invention will be described below, but redundant description of points similar to the above embodiment will be omitted.

[0040] The coupling part of the automated guided vehicle 1 is not limited to the cart 4. For example, the automated guided vehicles 2, 3 may be coupled by a coupling part that does not have wheels. Alternatively, each automated guided vehicle 2, 3 may be provided with a turntable that can rotate via a rotation shaft 5, and a transported object may be loaded so as to straddle the turntables provided on both automated guided vehicles 2, 3. In this case, the turntables of both automated guided vehicles 2, 3 and the transported object loaded on them serve as coupling parts.

[0041] The present invention can also be applied to the case where an object other than a vehicle body is transported by an unmanned transport device. [Explanation of symbols]

[0042] 1. Unmanned transport device 2. First automated guided vehicle 3. 2nd automated guided vehicle 4 Bogie (connecting part) 5 Rotation Axis 6 Bracket 8 wheels 9 Motor 10 Camera (line detection unit) 11 Angle detection unit 12 Control section 20 Guidance Line 21 Straight section 22 Curved section 23 Straight section 31~34 Event display section L Center line of connecting part (carriage) P1 Center of the first automated guided vehicle P2 Center of the second automated guided vehicle Q Stop position

Claims

1. A method for controlling an automated guided vehicle having a first automated guided vehicle on a leading side and a second automated guided vehicle on a trailing side capable of traveling along a guide line provided on a travel path, comprising: controlling each of the first and second automated guided vehicles so that a distance between the first and second automated guided vehicles is constant; A control method for an unmanned transport device, wherein, when the unmanned transport device travels along a curved portion of the guide line, the first unmanned transport vehicle is controlled in a trace travel mode that causes it to follow the guide line, and the second unmanned transport vehicle is controlled in an autonomous travel mode that does not cause it to follow the guide line.

2. the automated guided vehicle has a connection portion that connects the first automated guided vehicle and the second automated guided vehicle, The first automated guided vehicle and the connecting portion are connected to be rotatable about a first rotation axis in a vertical direction, and the second automated guided vehicle and the connecting portion are connected to be rotatable about a second rotation axis in a vertical direction, 2. The control method for an unmanned transport device according to claim 1, wherein, when controlling the second unmanned transport vehicle in the autonomous driving mode, the direction of travel of the second unmanned transport vehicle is controlled so as to be parallel to a straight line connecting the axis of the first rotation shaft and the axis of the second rotation shaft.

3. While the first automated guided vehicle is traveling along a straight portion following the curved portion of the guide line, 2. The method for controlling an automatic guided vehicle according to claim 1, further comprising the step of switching control of the second automatic guided vehicle from the autonomous travel mode to a trace travel mode in which the second automatic guided vehicle follows the guide line.

4. After the automated guided vehicle starts to decelerate toward a stop position, 2. The method for controlling an automatic guided vehicle according to claim 1, further comprising the step of switching control of the second automatic guided vehicle from the autonomous travel mode to a trace travel mode in which the second automatic guided vehicle follows the guide line.

5. An automated guided vehicle having a first automated guided vehicle on a leading side and a second automated guided vehicle on a trailing side that can travel along a guide line provided on a travel path, a control unit provided in the first automated guided vehicle and the second automated guided vehicle controls each of the first automated guided vehicle and the second automated guided vehicle so that a distance between the first automated guided vehicle and the second automated guided vehicle is constant; When the unmanned transport device travels along the curved portion of the guide line, a control unit of the first unmanned transport vehicle controls it in a trace travel mode that causes it to follow the guide line, and a control unit of the second unmanned transport vehicle controls it in an autonomous travel mode that does not cause it to follow the guide line.

Images