Unmanned carrier vehicle

Abstract

An unmanned carrier vehicle (91) comprises: four wheels (2L, 2R, 3L, 3R) that include driving wheels (2L, 2R) and are in contact with a floor (FL); a first arm (61) that couples two wheels (2L, 3L) among the four wheels; a second arm (71) that couples the remaining two wheels (2R, 3R) among the four wheels; and a frame (12) that supports the first arm (61) in a manner incapable of oscillation, and that supports the second arm (71) in a manner capable of oscillation about an oscillation center (CL7) provided in between the remaining two wheels (2R, 3R).

Description

automated guided vehicle

[0001] The present invention relates to unmanned transport vehicles.

[0002] Patent Document 1 discloses a four-wheeled automated guided vehicle. This automated guided vehicle does not have a suspension structure, but has a wheel structure that allows all four wheels to always be in contact with the ground regardless of undulations on the ground surface. In this wheel structure, the center of gravity of the automated guided vehicle is set close to two drive wheels, and the remaining two driven wheels are connected by an eccentric shaft. In this wheel structure, even if the ground contact heights of the two driven wheels are different, the eccentric shaft rotates automatically to receive a ground contact reaction force from the two driven wheels. As a result, the height of the driven wheel shaft is automatically adjusted.

[0003] Japanese Patent Application Publication No. 10-338145

[0004] The wheel structure disclosed in Patent Document 1 connects two driven wheels with an eccentric shaft, making it impossible to place other components between the driven wheels. This reduces the degree of freedom in the layout of the components that make up the automated guided vehicle, which hinders the miniaturization and multi-functionalization of the automated guided vehicle, leaving room for improvement.

[0005] One aspect of one or more embodiments of the present invention provides an automated guided vehicle comprising: four wheels, including drive wheels, that are in contact with the floor; a first arm that connects two of the four wheels and supports the two wheels; a second arm that connects the remaining two of the four wheels and supports the remaining two wheels; and a frame that supports the first arm so that it cannot swing and supports the second arm so that it can swing around a swing center provided between the remaining two wheels.

[0006] According to an aspect of one or more embodiments of the present invention, an automated guided vehicle can be easily made smaller and more multifunctional.

[0007] FIG. 1 is a perspective view of an automated guided vehicle according to an embodiment. FIG. 2 is a bottom view of the automated guided vehicle. FIG. 3 is a right side view of the automated guided vehicle. FIG. 4 is a left side view of the automated guided vehicle. FIG. 5A is a schematic right side view for explaining the operation of the automated guided vehicle. FIG. 5B is a schematic left side view for explaining the operation of the automated guided vehicle. FIG. 6 is a schematic left side view for explaining the operation of an automated guided vehicle of a comparative example. FIG. 7 is a schematic front view for explaining the operation of the automated guided vehicle.

[0008] The configuration of an automated guided vehicle 91 according to this embodiment will be described with reference to Figures 1 to 4. For ease of explanation, the up, down, left, right, front, and rear directions are defined as the directions of the arrows shown in Figure 1. The up and down direction is the vertical direction.

[0009] As shown in Figures 1 and 2, the automated guided vehicle 91 has a main body 1 that is a thin rectangular parallelepiped in appearance. The main body 1 has a frame 12 inside as a main structural member. Drive wheels 2 driven by motors 5 are provided at each of the two lower front corners of the main body 1. Driven wheels 3 are provided at each of the lower rear corners of the main body 1. Specifically, the drive wheels 2L and 2R are driven by motors 5L and 5R, respectively, and are not steered. The drive wheels 2L and 2R are driven independently of each other. The driven wheels 3L and 3R are free swivel casters that steer automatically. Note that the appearance of the automated guided vehicle 91 shown in Figure 1 is a schematic diagram, and the shape and dimensions of the automated guided vehicle 91 in Figure 1 do not necessarily correspond to the shape and dimensions in the structural diagrams shown in Figures 2 to 4.

[0010] A control unit 11 is mounted inside the main body 1 to control the operation of the automated guided vehicle 91. The control unit 11 controls the rotation speed and direction of the motors 5L and 5R based on a pre-stored driving program, etc. The rotation of the motors 5L and 5R is controlled independently of each other.

[0011] The main body 1 has a horizontal slit cut in the vertical center. Openings (not shown) are formed at the left front and right rear of the slit. The left front opening is open to the front and sides, and the right rear opening is open to the rear and sides. Sensors 41 and 42 are respectively disposed inside the openings. The sensors 41 and 42 are optical sensors. As shown in FIG. 3 , the sensor 41 detects obstacles and the distance to the obstacles on a horizontal monitoring surface SF41 parallel to the floor FL through the opening and transmits the detection results to the control unit 11. The sensor 42 also detects obstacles and the distance to the obstacles on a horizontal monitoring surface SF42 parallel to the floor FL through the opening and transmits the detection results to the control unit 11. The control unit 11 controls the operation of the main body 1, including the avoidance of the detected obstacles, based on the detection results.

[0012] As shown in FIGS. 2 and 4 , the left drive wheel 2L and the driven wheel 3L are connected to and supported by a plate- or pipe-shaped left arm 61. The left arm 61 is attached to the frame 12 so as to be able to swing freely via a left shaft 62 located approximately in the center between the drive wheel 2L and the driven wheel 3L. However, as will be explained below, the left arm 61 is prevented from swinging. As shown in FIG. 4 , fixed plates 611 and 612 are fixed to the left side of the frame 12, sandwiching the left shaft 62 therebetween. The fixed plate 611 is located in front of the left shaft 62, and the fixed plate 612 is located behind the left shaft 62. The fixed plates 611 and 612 abut against the left arm 61, thereby preventing the left arm 61 from swinging around the left shaft 62. In other words, the left arm 61 is attached to the frame 12 so as not to be able to swing.

[0013] 2 and 3 , the right drive wheel 2R and driven wheel 3R are connected to and supported by a plate-shaped or pipe-shaped right arm 71. The right arm 71 is attached to the frame 12 so as to be swingable about an axis line CL7 by a right shaft portion 72 located approximately in the center between the drive wheel 2R and the driven wheel 3R. In other words, the right arm 71 is attached to the frame 12 so as to be swingable. The axis line CL7 is the central axis of the right shaft portion 72, and hereinafter will also be referred to as the swing center CL7.

[0014] As shown in FIG. 3 , swing stopper plates 712, 711 are fixed to the right side of the frame 12, sandwiching the right shaft 72. The swing stopper plate 711 is located in front of the right shaft 72, and the swing stopper plate 712 is located behind the right shaft 72. The swing stopper plates 711, 712 restrict the swing angle range of the right arm 71 about the axis CL7 by abutting against the right arm 71. Here, the reference position of the automated guided vehicle 91 is defined as a position in which the drive wheels 2R and the driven wheels 3R ​​are in contact with the floor FL and the loading section 1a of the main body 1 is parallel to the floor FL. In FIG. 3 , which shows the reference position, the allowable angle α of rotation about the axis CL7 is 1.5° both clockwise and counterclockwise. This allowable angle α is set appropriately based on the distance between the drive wheels 2 and the driven wheels 3 and the degree of unevenness of the floor FL where the automatic guided vehicle 91 travels.

[0015] With the above-described configuration, the automated guided vehicle 91 travels under the control of the control unit 11 with four wheels, namely, the drive wheels 2 and the driven wheels 3, in contact with the flat floor FL. The control unit 11 autonomously controls the automated guided vehicle 91 to move straight or turn based on a pre-stored travel program and real-time detection results of the sensors 41 and 42. The control unit 11 autonomously controls the automated guided vehicle 91 to move forward or backward.

[0016] In order for the automated guided vehicle 91 to accurately detect obstacles ahead in the traveling direction, it is desirable that the monitoring surfaces SF41, SF42 of the sensors 41, 42 be as parallel as possible to the surface of the floor FL. For example, it is desirable that the monitoring surfaces SF41, SF42 be maintained parallel or nearly parallel to the floor FL while being as little affected by unevenness of the floor FL as possible. In other words, it is desirable to minimize changes in the inclination of the frame 12 of the main body 1. This will be described with reference to FIGS. 5A and 5B.

[0017] For example, Fig. 5A shows the right side view of the automated guided vehicle 91 when the right drive wheel 2R runs over a step FLa in the floor FL, and Fig. 5B shows the left side view of the same case. The height of the step FLa that protrudes upward is set so that the rotation angle of the right arm 71 falls within the range of the allowable angle α.

[0018] 5A, when the driving wheel 2R side runs over a step FLa, the right arm 71 is lifted and tilted so that the driven wheel 3R is positioned downward. This allows not only the driving wheel 2R but also the driven wheel 3R to maintain contact with the floor FL. This tilt of the right arm 71 does not substantially affect the tilt of the frame 12.

[0019] 5B, the left drive wheel 2L and driven wheel 3L are both in contact with the floor FL, and the frame 12 maintains a posture in which the loading section 1a is generally parallel to the floor FL. As a result, the monitoring surfaces SF41 and SF42 of the sensors 41 and 42 are maintained generally parallel to the floor FL, and no problems occur in detecting obstacles while the automated guided vehicle 91 is traveling.

[0020] Furthermore, in the automated guided vehicle 91, one of the left or right arms is made non-swingable, and a sensor is disposed at the leading portion of the arm that is not swingable. In the example described above, the left arm 61 is made non-swingable, and the sensor 41 is disposed at the front left portion. The drive wheels 2L and driven wheels 3L supported by the non-swingable arm (left arm 61) contact the ground along the slope of the floor FL, even if the floor FL is inclined. This makes it easier for the monitoring surface SF41 of the sensor 41 to follow the slope of the floor FL, thereby maintaining a high level of accuracy in detecting obstacles on the floor FL while the automated guided vehicle 91 is traveling.

[0021] Furthermore, high obstacle detection accuracy is maintained regardless of the position of the center of gravity of the load loaded on the loading section 1a. A specific description will be given with reference to an automated guided vehicle P91 of a comparative example. FIG. 6 is a schematic left side view showing the automated guided vehicle P91 of the comparative example. In the comparative example, both the left and right arms of the automated guided vehicle 91 are swingable. That is, the drive wheel 2L and the driven wheel 3L are connected by a swingable left arm P61. The right arm (not shown) is also swingable.

[0022] In the comparative example of the automated guided vehicle P91 in which both the left and right arms are swingable, when the center of gravity of the load on the loading section 1a is G1, which is biased forward, the frame 12 tilts downward toward the front, as shown by the solid line. In this case, the monitoring surface SF41 of the sensor 41 becomes a plane that tilts downward toward the front with respect to the floor FL. On the other hand, when the center of gravity of the load on the loading section 1a is G3, which is biased backward, the frame 12 tilts downward toward the rear, as shown by the dashed-dotted line. In this case, the monitoring surface SF41 of the sensor 41 becomes a plane that tilts downward toward the rear with respect to the floor FL with respect to the center of gravity.

[0023] In contrast, in the automated guided vehicle 91 of this embodiment, the left arm 61 cannot swing. Therefore, even if the center of gravity of the load on the loading section 1a is shifted forward or backward (center of gravity G1 or G3 in FIG. 5B ), or even if it is at the corresponding position of the left shaft section 62 (center of gravity G2 in FIG. 5B ), the monitoring surface SF41 follows the inclination of the floor FL and remains generally parallel. Furthermore, because the sensor 41 is disposed on the side of the left arm 61, which cannot swing, maintaining the monitoring surface SF41 parallel to the floor FL is advantageous for obstacle detection. Therefore, high accuracy in detecting obstacles is maintained while the automated guided vehicle 91 is traveling, regardless of the position of the center of gravity of the load in the forward / backward direction.

[0024] FIG. 7 shows the state in which the drive wheel 2R of the automated guided vehicle 91 of this embodiment climbs onto a step FLa (the state shown in FIGS. 5A and 5B ). In this state, the frame 12 and the loading platform 1a are tilted at an angle β with respect to the floor FL so that their right sides are higher (see arrow DR7 in FIG. 7 ). Even in this state, because the sensor 41 is located near the front corner on the left side, where it cannot swing, the vertical displacement of the sensor 41 is significantly smaller than the vertical displacement on the right side (dashed line). Therefore, fluctuations in the height of the monitoring surface SF41 of the sensor 41 are extremely small, and the accuracy of obstacle detection while the automated guided vehicle 91 is traveling remains high, substantially unchanged from when the floor FL is flat.

[0025] As described above in detail, in the automated guided vehicle 91 of this embodiment, the pair of left and right (widthwise) driven wheels 3L, 3R are not connected by an eccentric shaft or the like, so components can be placed between the driven wheels 3L, 3R. In this embodiment, the control unit 11 is placed between the driven wheels 3L, 3R, but other components may also be placed therebetween. In this way, there is a high degree of freedom in the layout of the components that make up the automated guided vehicle 91, making it easy to reduce the size and make the automated guided vehicle 91 multifunctional.

[0026] Furthermore, in the automated guided vehicle 91 of this embodiment, one of the arms connecting the left and right drive wheels 2 and driven wheels 3 (the left arm 61 in this embodiment) is made non-swingable, while the other (the right arm 71 in this embodiment) is made swingable. This minimizes the effects of unevenness in the floor FL and the position of the center of gravity of the load in the front-to-rear direction in the automated guided vehicle 91, and effectively maintains the parallelism of the monitoring surface SF41 of the sensor 41 to the floor FL. As a result, a high level of accuracy is maintained in detecting obstacles while the automated guided vehicle 91 is traveling.

[0027] The present invention is not limited to the above-described embodiment, and may be modified within the scope of the present invention.

[0028] The non-swingable arm and the swingable arm may be arranged laterally inversely to those in the above embodiment. In this case, the sensor on the side of the vehicle that is primarily used for forward travel (the front side in the above embodiment) may be arranged closer to the non-swingable arm in the width direction than to the swingable arm. In-wheel motors may be used as the motors 5L and 5R, and any component may be arranged between the drive wheels 2L and 2R. In the above embodiment, the swing of the left arm 61 is prevented by the abutment of the fixed plates 611 and 612. However, the left arm 61 may be fixed to the frame 12 via the non-swingable left axle 62. Because the driven wheel 3 in the above embodiment is a swivel caster, the distance between the drive wheel 2 and the driven wheel 3 changes to some extent depending on its orientation. The fore-aft position of the right axle 72 is preferably such that the ground reaction force acting on the drive wheel 2R and the ground reaction force acting on the driven wheel 3R are as close as possible to each other. For example, it is preferable that the position of the right axle 72 be determined to match the orientation of the swivel caster during forward travel, which accounts for the majority of travel.

[0029] The unmanned guided vehicle 91 according to the above embodiment includes four wheels 2L, 2R, 3L, and 3R, each including drive wheels 2L and 2R, that are in contact with the floor FL; a first arm 61 that connects two of the four wheels 2L and 3L and supports the two wheels 2L and 3L; a second arm 71 that connects the remaining two of the four wheels 2R and 3R and supports the remaining two wheels 2R and 3R; and a frame 12 that supports the first arm 61 so that it cannot swing and supports the second arm 71 so that it can swing around a swing center CL7 that is provided between the remaining two wheels 2R and 3R.

[0030] Since the pair of left and right (widthwise) driven wheels 3L, 3R are not connected by an eccentric shaft or the like, parts, components, members, etc. can be placed between the pair of driven wheels 3L, 3R. In the above embodiment, the control unit 11 is placed between the driven wheels 3L, 3R, but other parts, etc. may also be placed between the driven wheels 3L, 3R. This allows for a high degree of freedom in the layout of the parts that make up the automated guided vehicle 91, making it easy to reduce the size and increase the number of functions.

[0031] In the above embodiment, the automatic guided vehicle 91 further includes a sensor 41 that detects surrounding obstacles. The sensor 41 is disposed closer to the first arm 61 than the second arm 71.

[0032] The monitoring surface SF41 of the sensor 41 tilts depending on the unevenness of the floor FL and the position of the center of gravity of the load. However, this tilt is suppressed by the above-described arrangement of the sensor 41, so that a high level of accuracy in detecting obstacles while the automatic guided vehicle 91 is traveling is maintained.

[0033] In the above embodiment, when the floor FL is flat, the sensor 41 detects an obstacle on a plane parallel to the floor FL.

[0034] This allows the automated guided vehicle 91 to quickly detect an obstacle that is far away in the traveling direction, thereby enabling the automated guided vehicle 91 to reliably perform an avoidance operation or a detour operation, improving the efficiency of transporting goods.

[0035] In the above embodiment, the first arm 61 is swingably supported by the frame 12. In addition, the automated guided vehicle 91 further includes fixing plates 611, 612 that come into contact with the first arm 61 so as to prevent the first arm 61 from swinging.

[0036] This configuration makes it possible to replace the fixed plates 611, 612 with the swing restriction plates 711, 712. This replacement allows the first arm 61 to swing and the second arm 71 to not swing, improving the versatility of the automated guided vehicle 91.

[0037] In the above embodiment, one of the two wheels 2L, 3L supported by the first arm 61 and one of the remaining two wheels 2R, 3R supported by the second arm 71 are drive wheels. The other two wheels are driven wheels.

[0038] This allows the automatic guided vehicle 91 to move smoothly in a straight line or turn, and also to move smoothly forward or backward.

[0039] The present invention is not limited to the above-described embodiments, and can be implemented in various forms by making appropriate modifications. The entire contents of Japanese Patent Application No. 2024-51800 (filed March 27, 2024) are incorporated herein by reference. Although the present invention has been described above with reference to embodiments of the present invention, the present invention is not limited to the above-described embodiments. The scope of the present invention is determined in light of the claims.

Claims

1. An automated guided vehicle comprising: four wheels, including drive wheels, that are in contact with the floor; a first arm that connects two of the four wheels and supports the two wheels; a second arm that connects the remaining two of the four wheels and supports the remaining two wheels; and a frame that supports the first arm so that it cannot swing and supports the second arm so that it can swing around a swing center located between the remaining two wheels.

2. An automated guided vehicle according to claim 1, further comprising a sensor for detecting obstacles around the automated guided vehicle, the sensor being positioned closer to the first arm than to the second arm.

3. An automated guided vehicle according to claim 2, wherein, when the floor is flat, the sensor detects an obstacle on a plane parallel to the floor.

4. An automated guided vehicle according to claim 1, wherein the first arm is supported by the frame so as to be swingable, and the automated guided vehicle further comprises a fixed plate that abuts against the first arm so as to prevent the first arm from swinging.

5. An automated guided vehicle according to any one of claims 1 to 4, wherein one of the two wheels supported by the first arm and one of the remaining two wheels supported by the second arm are drive wheels, and the other two wheels are driven wheels.

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