Overhead conveyance vehicle

Abstract

This overhead conveyance vehicle comprises: a holding unit for holding articles that is provided to a main body so as to be able to be raised and lowered; a raising / lowering drive unit that raises and lowers the holding unit; and a recognition device that recognizes the horizontal position and vertical position of the holding unit.

Description

Ceiling transport vehicle

[0001] The present disclosure relates to an overhead transport vehicle.

[0002] As a technology related to ceiling transport vehicles, Patent Document 1 describes a transport vehicle that includes a lifting platform (holding unit) that is movable up and down relative to a main body and has a gripper, and a lifting drive unit that raises and lowers the lifting platform. The transport vehicle described in Patent Document 1 is provided with a vibration detection sensor in the lifting drive unit. This vibration detection sensor emits laser light toward a reflector on the top surface of the lifting platform and detects vibration of the lifting platform based on whether or not the reflected light (return light) is detected.

[0003] International Publication No. 2020 / 121765

[0004] In an overhead transport vehicle, when raising or lowering a holding unit, for example, an obstacle may be present at a specific height, and therefore it is desirable to be able to accurately grasp the amount of sway of the holding unit as well as the height at which the holding unit is located. In this regard, the above-mentioned overhead transport vehicle only detects whether the amount of sway of the holding unit is within a predetermined range (with return light) or whether it is greater than or equal to the predetermined range (without return light), and therefore there is a risk that it will not be possible to accurately grasp the amount of sway of the holding unit, and will not be able to grasp the height at which the holding unit is located.

[0005] Therefore, an object of the present disclosure is to provide a ceiling transport vehicle that can accurately grasp the amount of sway of a holding unit as well as the height at which the holding unit is located.

[0006] (1) The ceiling transport vehicle according to the present disclosure includes a holding unit that is movable up and down relative to a main body and holds items, a lifting drive unit that raises and lowers the holding unit, and a recognition device that recognizes the horizontal and vertical positions of the holding unit.

[0007] In this ceiling transport vehicle, when the holding unit is raised or lowered, the recognition result of the recognition device makes it possible to quantify the sway of the holding unit while grasping the height position of the holding unit. In other words, it becomes possible to accurately grasp the amount of sway of the holding unit along with the height at which the holding unit is located.

[0008] (2) In the overhead transport vehicle described in (1) above, the holding unit may be provided with a reflecting member, and the recognition device may include a sensor that irradiates light at multiple irradiation angles toward the reflecting member within a monitoring range that includes the reflecting member and detects multiple return lights reflected by the reflecting member in response to the irradiation, and a processing unit that determines the horizontal position and the vertical position of the holding unit based on the detection results of the multiple return lights detected by the sensor. In this case, the horizontal position and the vertical position of the holding unit can be easily detected using the return light.

[0009] (3) In the overhead transport vehicle described in (2) above, when the traveling direction of the overhead transport vehicle is the X direction and the horizontal direction perpendicular to the X direction is the Y direction, the sensor may irradiate light so as to scan in the Y direction toward the reflective member within the monitoring range, and the processing unit may calculate an average angle and an average distance for the optical axes of the detected multiple return lights, and calculate the position of the holding unit in the Y direction based on the average angle and the average distance. In this case, it is possible to accurately grasp the amount of shaking of the holding unit in the Y direction.

[0010] (4) In the ceiling transport vehicle described in (3) above, the shape of the reflective member may include a shape in which the width in the Y direction varies as the position in the X direction increases, and the processing unit may determine the position of the holding unit in the X direction based on the number of returned lights stored in advance and the number of the plurality of returned lights detected. In this case, it is possible to accurately determine the amount of swing of the holding unit in the X direction together with its height.

[0011] (5) The ceiling transport vehicle according to any one of (1) to (4) above may further include a determination unit that determines whether the horizontal position of the support unit recognized by the recognition device is within an allowable range. In this case, it becomes possible to determine whether the amount of sway of the support unit is allowable.

[0012] (6) The ceiling transport vehicle according to any one of (1) to (5) above may include a lateral transfer mechanism that moves the lifting drive unit laterally relative to the main body unit. This makes it possible to accurately grasp the amount of sway of the holding unit and the height at which the holding unit is located, for example, when lifting or lowering an article between the main body unit and a placement unit located to the side of the main body unit.

[0013] (7) In the ceiling transport vehicle described in (6) above, when the lifting drive unit is moved laterally by the lateral transfer mechanism, the recognition device may correct the horizontal position of the holding unit based on a pre-stored correction value corresponding to the inclination of the lifting drive unit. This makes it possible to accurately grasp the amount of sway of the holding unit as well as its height, even if the irradiation direction of the sensor is tilted due to the inclination of the lifting drive unit when the lifting drive unit is moved laterally by the lateral transfer mechanism.

[0014] (8) The ceiling transport vehicle according to any one of (1) to (7) above may include a storage unit that stores the horizontal and vertical positions of the support unit recognized by the recognition device in chronological order for a predetermined period of time. In this case, the behavior of the support unit can be grasped, and the grasped behavior of the support unit can be utilized for, for example, maintenance.

[0015] According to the present disclosure, it is possible to accurately grasp the amount of shaking of the holding unit as well as the height at which the holding unit is located.

[0016] FIG. 1 is a side view showing an overhead transport vehicle according to one embodiment. FIG. 2 is a front view showing a sensor and a reflector in an initial state. FIG. 3(a) is a schematic plan view showing the reflector of FIG. 2. FIG. 3(b) is a schematic perspective view showing the sensor and the reflector of FIG. 2. FIG. 4 is a block diagram showing a transport vehicle controller. FIG. 5 is a front view showing the sensor and the reflector during transfer. FIG. 6(a) is a schematic plan view showing the reflector of FIG. 5. FIG. 6(b) is a schematic perspective view showing the sensor and the reflector of FIG. 5.

[0017] Hereinafter, the embodiments will be described in detail with reference to the drawings. In the description of the drawings, the same or corresponding elements are designated by the same reference numerals, and redundant description will be omitted.

[0018] As shown in FIG. 1 , an overhead transport vehicle 1 according to the embodiment travels along a track 20 installed near the ceiling of a clean room where semiconductor devices are manufactured. The track 20 forms a travel path for the overhead transport vehicle 1. The overhead transport vehicle 1 is a transport vehicle capable of transporting an item 200 and transferring the item 200 to a load port 300. The item 200 is, for example, a front-opening unified pod (FOUP) that accommodates multiple semiconductor wafers. The load port 300 is, for example, a placement unit provided in a processing device that performs various processes on semiconductor wafers. The item 200 and the load port 300 are not particularly limited. In this example, the load port 300 is located away from the track 20 in the lateral direction (to the side of the traveling direction of the overhead transport vehicle 1).

[0019] In the following description, the terms "upper" and "lower" correspond to the upper and lower vertical directions, respectively. The term "front" corresponds to the front side in the traveling direction of the overhead transport vehicle 1, and the term "rear" corresponds to the rear side in the traveling direction of the overhead transport vehicle 1. The X direction corresponds to the traveling direction, the Z direction corresponds to the up-down direction, and the Y direction corresponds to the lateral direction (the horizontal direction perpendicular to the traveling direction).

[0020] The ceiling transport vehicle 1 includes a frame unit 2, a traveling unit 3, a lateral unit 4, a theta unit 5, a lifting drive unit 6, a holding unit 7, and a transport vehicle controller 8. The frame unit 2 has a center frame 15, a front frame 16, and a rear frame 17. The frame unit 2 constitutes a main body. The front frame 16 extends downward from the front end of the center frame 15. The rear frame 17 extends downward from the rear end of the center frame 15.

[0021] The traveling unit 3 is disposed above the center frame 15. The traveling unit 3 travels along the track 20 by, for example, receiving a contactless supply of power from a high-frequency current line laid along the track 20. The lateral unit 4 is disposed below the center frame 15. The lateral unit 4 moves the theta unit 5, the lifting drive unit 6, and the holding unit 7 in the Y direction (horizontal direction) relative to the frame unit 2. The lateral unit 4 slides the theta unit 5, the lifting drive unit 6, and the holding unit 7 in the Y direction relative to the frame unit 2, for example, by the driving force of a driving mechanism (e.g., a drive motor, pulleys, belts, etc.) not shown. The lateral unit 4 constitutes a lateral transfer mechanism. The theta unit 5 is disposed below the lateral unit 4. The theta unit 5 rotates the lifting drive unit 6 and the holding unit 7 in a horizontal plane.

[0022] The lifting drive unit 6 is disposed below the theta unit 5. The lifting drive unit 6 raises and lowers the holding unit 7 in the Z direction by unwinding and winding up hanging members B, such as multiple belts, connected to the holding unit 7. The hanging members B are flexible. The lifting drive unit 6 constitutes a lifting drive section. The holding unit 7 is disposed below the lifting drive unit 6. The holding unit 7 is arranged so that it can be raised and lowered relative to the frame unit 2 by the lifting drive unit 6. The holding unit 7 has holding parts 12, such as a pair of grippers, that can be opened and closed horizontally. The holding unit 7 holds the flange 201 of the item 200 with the pair of holding parts 12.

[0023] The transport vehicle controller 8 is disposed on the center frame 15. The transport vehicle controller 8 is an electronic control unit configured with a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc. The transport vehicle controller 8 is a control unit that controls each part of the ceiling transport vehicle 1. The transport vehicle controller 8 may be configured with multiple electronic control units. When configured with multiple electronic control units, these may be connected via a communication network such as the Internet or an intranet to logically construct a single unit. The transport vehicle controller 8 may be disposed on the front frame 16, etc.

[0024] The overhead transport vehicle 1 configured as described above operates, for example, as follows during lateral transfer of the article 200 from the load port 300. When the overhead transport vehicle 1 is stopped at a position corresponding to the load port 300, it drives the lateral unit 4 to move the holding unit 7 in the forward direction relative to the frame unit 2. At the same time, if necessary, it adjusts the orientation of the holding unit 7 by driving the theta unit 5. The forward direction is the lateral direction in which the holding unit 7 advances so as to protrude from the frame unit 2. Next, the overhead transport vehicle 1 drives the lifting drive unit 6 to lower the holding unit 7, thereby holding the flange 201 of the article 200 on the load port 300 with the holding unit 7. The overhead transport vehicle 1 drives the lifting drive unit 6 to raise the holding unit 7 to the upper end. Then, the overhead transport vehicle 1 drives the lateral unit 4 to move the holding unit 7 in the retreat direction, which is the opposite direction to the forward direction, and positions the holding unit 7 between the front frame 16 and the rear frame 17.

[0025] On the other hand, the ceiling transport vehicle 1 operates, for example, as follows during lateral transfer of the article 200 to the load port 300. At a stop position corresponding to a position laterally of the load port, the ceiling transport vehicle 1 drives the lateral unit 4 to move the holding unit 7 holding the article 200 in the forward direction relative to the frame unit 2. At the same time, if necessary, the theta unit 5 is driven to adjust the orientation of the holding unit 7. Next, the ceiling transport vehicle 1 drives the lifting drive unit 6 to lower the holding unit 7, placing the article 200 on the load port 300, and the holding unit 7 releases its hold on the flange 201 of the article 200. The ceiling transport vehicle 1 drives the lifting drive unit 6 to raise the holding unit 7 to the upper end. Then, the ceiling transport vehicle 1 drives the lateral unit 4 to move the holding unit 7 in the retreat direction, positioning the holding unit 7 between the front frame 16 and the rear frame 17.

[0026] As shown in Figures 1, 2, 3(a), and 3(b), the ceiling transport vehicle 1 includes a sensor 10 and a reflector 11. The sensor 10 is provided in the lifting drive unit 6. The sensor 10 is, but is not limited to, a laser range finder, for example. The sensor 10 irradiates a laser beam (light) L toward the reflector 11 at multiple irradiation angles within a monitoring range Z including the reflector 11, and detects multiple return beams RL reflected by the reflector 11 in response to the irradiation. The sensor 10 irradiates the laser beam L toward the reflector 11 within the monitoring range Z so as to scan in the Y direction. The monitoring range Z is an isosceles triangular region with the sensor 10 as its vertex, as viewed from the X direction. The sensor 10 is connected to the transport vehicle controller 8. The return beam is also referred to as reflected beam.

[0027] The reflector 11 is provided on the holding unit 7. As an example, the reflector 11 is provided in the center of the upper part of the holding unit 7. The reflector 11 is capable of reflecting the laser light L from the sensor 10. The reflector 11 is arranged with its reflective surface facing upward, and is capable of reflecting the laser light L from above upward. The reflector 11 is arranged directly below the sensor 10 when the lifting drive unit 6 is in a horizontal state. The reflector 11 is not particularly limited, and various reflective materials can be used.

[0028] The reflector 11 has a shape in which the width in the Y direction varies from the center to the outside in the X direction. For example, the reflector 11 is a rectangular plate member, and is arranged with its diagonal line aligned with the Y direction in a plan view. The reflector 11 has a shape that is line-symmetrical with respect to an axis that passes through the center and extends along the X direction. The reflector 11 may include a shape with a constant width in the Y direction in a part thereof. The reflector 11 may be made of reflective tape, or may be made of various materials capable of reflecting the laser light L.

[0029] 4, the transport vehicle controller 8 has, as its functional configuration, a processing unit 8A, a determination unit 8B, and a memory unit 8C. The processing unit 8A determines (recognizes) the horizontal position and the vertical position of the holding unit 7 based on the detection results of the multiple return lights RL detected by the sensor 10.

[0030] The processing unit 8A calculates the average angle and average distance for the optical axes of the detected plurality of return beams RL, and calculates the Y-direction position of the holding unit 7 based on the average angle and average distance. The processing unit 8A calculates the X-direction position of the holding unit 7 based on the pre-stored number of return beams RL and the number of the detected plurality of return beams RL. The processing unit 8A corrects the horizontal position of the holding unit 7 based on a pre-stored correction value corresponding to the inclination of the lifting drive unit 6 during lateral transfer in which the lateral unit 4 moves the lifting drive unit 6 laterally. Details of each process of the processing unit 8A will be described later.

[0031] The determination unit 8B determines whether the horizontal position of the holding unit 7 recognized by the processing unit 8A is within an allowable range. The determination unit 8B may determine whether at least one of the X-direction position and the Y-direction position of the holding unit 7 recognized by the processing unit 8A is within an allowable range. The allowable range may be a predetermined fixed width. The allowable range may be defined by an angle or width according to the height direction position of the holding unit 7. The allowable range may be a range in the X direction, a range in the Y direction, or a range including both.

[0032] When the determination unit 8B determines that the horizontal position of the holding unit 7 recognized by the processing unit 8A is not within the allowable range, the determination unit 8B may cause an alarm unit (not shown) to issue a vibration detection error, indicating that vibration of the holding unit 7 has exceeded the allowable range. The determination result by the determination unit 8B may be transmitted to an external higher-level controller. The storage unit 8C stores the horizontal and vertical positions of the holding unit 7 recognized by the processing unit 8A in chronological order for a predetermined period of time. The predetermined period is not particularly limited and may be a fixed period set in advance or a period that can be changed by the user.

[0033] Next, we will explain the pre-processing step before determining the horizontal and vertical positions of the holding unit 7. As shown in Figure 2, in the initial state where the lateral unit 4 is not tilted, the elevation drive unit 6 is not shaking, and the reflector 11 is located directly below the sensor 10, the sensor 10 irradiates laser light L so as to scan in the Y direction toward the reflector 11, and detects multiple return beams RL reflected by the reflector 11 in response to the irradiation.

[0034] The processing unit 8A calculates the average angle of the optical axes of the detected multiple return lights RL as the initial average angle α0. The average angle may be, for example, the average of the angle of the optical axis of the first return light RL1 detected first among the detected multiple return lights RL and the angle of the optical axis of the first return light RL2 detected last among the detected multiple return lights RL. The first return light RL1 corresponds to the return light RL detected when the return light RL is switched from a non-detected state to a detected state. The second return light RL2 corresponds to the return light RL detected when the return light RL is switched from a detected state to a non-detected state. The initial average angle α0 corresponds to the angle of the optical axis of the laser light L0 irradiated onto the center of the reflector 11 in the scanning direction of the optical axis in the initial state.

[0035] 3A and 3B, the processing unit 8A determines the number of detected return light beams RL as the initial number of return light beams. The initial number of return light beams corresponds to the detection range H0 of the reflector 11, which is the range within which the return light beam RL is detected in the initial state (where the laser beam L is incident). The number of detected return light beams RL corresponds to the number of optical axes of the detected return light beams RL. The processing unit 8A stores the determined initial angle average α0 and initial number of return light beams in the memory unit 8C.

[0036] Note that the above-described pre-processing step may be unnecessary if the initial angle average α0 and the initial return light count are acquired in advance using some method such as simulation and stored in the memory unit 8C. The reference angle is not particularly limited, and the point directly below the sensor 10 (vertically downward) may be set to 0°. The reference positions of the holding unit 7 in the X and Y directions are not particularly limited, and the position of the holding unit 7 (sensor 10) in the initial state may be set to 0°. The reference position of the holding unit 7 in the height direction (Z direction) is not particularly limited, and the position of the sensor 10 in the height direction may be set to 0°.

[0037] Next, a case will be described in which the horizontal and vertical positions of the holding unit 7 are determined during lateral transfer, for example, when transferring an article 200 between the holding unit 7 and a load port 300 located to the side of the track 20 in a plan view. As shown in Figure 5, in this example, the holding unit 7 swings in the Y direction, and the reflector 11 is shifted in the Y direction from directly below the sensor 10.

[0038] First, the sensor 10 irradiates the reflector 11 with a laser beam L so as to scan in the Y direction, and detects multiple beams of return light RL reflected by the reflector 11 in response to the irradiation. The processing unit 8A calculates the average angle and average distance for the optical axes of the detected multiple beams of return light RL as the transfer angle average α1 and the transfer distance average B1. The average distance may be, for example, the average distance of each optical axis of the multiple beams of return light RL. The distance of the return light RL can be obtained, for example, based on the intensity of the return light RL. The transfer angle average α1 corresponds to the angle of the optical axis of the laser beam L1 irradiated to the center of the reflector 11 in the scanning direction of the optical axis during transfer.

[0039] The processing unit 8A calculates the difference β between the initial angle average α0 and the transfer-time angle average α1, and determines the Y-direction position of the holding unit 7 according to the following equation (1) relating the difference β and the transfer-time distance average B1. The Y-direction position of the holding unit 7 corresponds to the amount of shaking of the holding unit 7 in the Y direction. Y-direction position of holding unit 7=B1·sin β (1)

[0040] At this time, the processing unit 8A corrects the horizontal position of the holding unit 7 based on a correction value previously stored in the memory unit 8C. The correction value is a value corresponding to the inclination (posture) of the lifting drive unit 6. The correction value is a value for correcting the initial angle average α0 according to the inclination of the lifting drive unit 6. For example, since the inclination of the lifting drive unit 6 depends on whether or not the lateral unit 4 is driven, the drive amount of the lateral unit 4, the type of load port 300 to be transferred, the inclination of the track 20, etc., a correction value associated with at least any of these factors is set in the correction value table. As an example, the processing unit 8A obtains a correction value corresponding to the inclination of the lifting drive unit 6 from the drive amount of the lateral unit 4 from the correction value table, and adds or subtracts the correction value to or from the initial angle average α0 when calculating the Y-direction position of the holding unit 7 using the above equation (1).

[0041] Furthermore, the processing unit 8A calculates the height position of the holding unit 7 based on the transfer distance average B1 and the difference β, for example, according to the following formula (2): Height position of the holding unit 7=B1·cos β (2)

[0042] As shown in FIGS. 6A and 6B, the processor 8A determines the number of detected return beams RL as the number of return beams during transfer. The number of return beams during transfer corresponds to the detection range H1, which is the range of the reflector 11 within which the return beam RL is detected during transfer. When the scanning position of the laser beam L deviates from the initial state in the X direction, the number of return beams during transfer differs from (is reduced in this case) the initial number of return beams, depending on the shape of the reflector 11 (see FIGS. 3A and 6A). Therefore, the processor 8A determines the X-direction position of the holding unit 7 from the difference between the initial number of return beams and the number of return beams during transfer, for example, using a conversion coefficient Gx, according to the following equation (3): The conversion coefficient Gx is a coefficient for converting the difference between the initial number of return beams and the number of return beams during transfer into a deviation in the X direction, and may be stored in advance in the memory unit 8C. The X-direction position of the holding unit 7 corresponds to the amount of shaking of the holding unit 7 in the X direction. Position of holding unit 7 in X direction=(initial return light number−transfer return light number)·Gx (3)

[0043] As described above, when the ceiling transport vehicle 1 raises and lowers the holding unit 7, the swing of the holding unit 7 can be quantified from the positions of the holding unit 7 in the X and Y directions while grasping the height position of the holding unit 7. In other words, it is possible to accurately grasp the amount of swing of the holding unit 7 along with the height at which the holding unit 7 is located. The amount of swing of the holding unit 7 can be numerically managed.

[0044] In the ceiling transport vehicle 1, a reflector 11 is provided on the holding unit 7, and a sensor 10 irradiates laser light L toward the reflector 11 at multiple irradiation angles and detects multiple return beams RL reflected by the reflector 11 in response to the irradiation. Then, based on the detection results of the sensor 10, a processing unit 8A determines the horizontal position and height position of the holding unit 7. In this case, the horizontal position and height position of the holding unit 7 can be easily detected using the return beam RL.

[0045] In the ceiling transport vehicle 1, the sensor 10 irradiates the laser light L so as to scan in the Y direction toward the reflector 11 within the monitoring range Z. The processing unit 8A calculates the average angle and average distance for the optical axes of the detected multiple return lights RL, and calculates the position of the holding unit 7 in the Y direction based on the average angle and average distance. In this case, it is possible to accurately grasp the amount of swing of the holding unit 7 in the Y direction together with its height.

[0046] In the ceiling transport vehicle 1, the shape of the reflector 11 includes a shape in which the width in the Y direction varies as it moves in the X direction. The processing unit 8A determines the position of the holding unit 7 in the X direction based on the pre-stored initial return light count and the transfer return light count. In this case, it is possible to accurately grasp the amount of shaking of the holding unit 7 in the X direction.

[0047] The ceiling transport vehicle 1 further includes a determination unit 8B that determines whether the recognized horizontal position of the holding unit 7 is within an allowable range. In this case, it becomes possible to determine whether the amount of shaking of the holding unit 7 is allowable.

[0048] The ceiling transport vehicle 1 is equipped with a lateral unit 4 that moves the lifting drive unit 6 laterally relative to the frame unit 2. This makes it possible to accurately grasp the amount of sway of the holding unit 7 as well as the height at which the holding unit 7 is located, for example, during lateral transfer.

[0049] In the ceiling transport vehicle 1, when the lifting drive unit 6 is moved laterally by the lateral unit 4, the processing unit 8A corrects the horizontal position of the holding unit 7 based on a pre-stored correction value. This makes it possible to accurately grasp the amount of sway of the holding unit 7 as well as its height, even if the irradiation direction of the sensor 10 is tilted due to the tilt of the lifting drive unit 6 when the lifting drive unit 6 is moved laterally by the lateral unit 4. Furthermore, in the ceiling transport vehicle 1, the horizontal position of the holding unit 7 may be corrected based on a correction value corresponding to the tilt of the lifting drive unit 6 due to the tilt of the track 20. In this case, it is possible to accurately grasp the amount of sway of the holding unit 7 as well as its height, even if the irradiation direction of the lifting drive unit 6 and the sensor 10 is tilted due to the tilt of the track 20.

[0050] The ceiling transport vehicle 1 includes a memory unit 8C that stores, in chronological order for a predetermined period, the recognized horizontal and vertical positions of the holding unit 7. In this case, the behavior of the holding unit 7 can be grasped, and the grasped behavior of the holding unit 7 can be utilized for, for example, maintenance.

[0051] Furthermore, the ceiling transport vehicle 1 has the following advantageous effects. That is, the behavior of the holding unit 7 (horizontal position corresponding to the vertical position) can be accurately grasped. The absolute position (three-dimensional position) of the holding unit 7 can be accurately grasped. Appropriate control can be performed according to the behavior of the holding unit 7. For example, even if the transfer of the item 200 is stopped due to shaking beyond the allowable range, control such as automatic recovery when the shaking decreases is possible. The size of the reflecting plate 11 is no longer related to the allowable amount of shaking. The size of the reflecting plate 11 can be increased. The amount of shaking of the reflecting plate 11 can be calculated in real time. It is preferable that the angular resolution of the sensor 10 be fine. By performing calculations that take into account the inclination of the lifting drive unit 6 during lateral transfer and due to the inclination of the track 20, etc., the influence of the inclination is reduced.

[0052] Although the embodiments have been described above, one aspect of the present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of one aspect of the invention.

[0053] In the above embodiment, the shape of the reflector 11 is not particularly limited. The shape of the reflector 11 may include a shape in which the width in the Y direction varies as the distance increases in the X direction. The shape of the reflector 11 may include a polygonal shape, an elliptical shape, an oval shape, or a shape that is a combination of these, as long as the width in the Y direction varies as the distance increases in the X direction.

[0054] In the above embodiment, the recognition device has the sensor 10, but may have an imaging device such as a stereo camera instead of the sensor 10. In the above embodiment, the transport vehicle controller 8 has the processing unit 8A, the determination unit 8B, and the memory unit 8C, but some or all of the processing unit 8A, the determination unit 8B, and the memory unit 8C may be mounted on an external computer that can communicate with the ceiling transport vehicle 1.

[0055] The components in the above embodiments and modifications are not limited to the materials and shapes described above, and various materials and shapes can be applied. The components in the above embodiments or modifications can be arbitrarily applied to the components in other embodiments or modifications. Parts of the components in the above embodiments or modifications can be omitted as appropriate without departing from the spirit of one aspect of the present invention. In the above, the sensor 10 and the processing unit 8A constitute a recognition device that recognizes the horizontal and vertical positions of the holding unit 7.

[0056] 1...ceiling transport vehicle, 2...frame unit (main body), 4...lateral unit (lateral transfer mechanism), 6...lifting drive unit (lifting drive section), 7...holding unit, 8A...processing section (recognition device), 8B...determination section, 8C...memory section, 10...sensor, 11...reflector (reflecting member), 200...article, 300...load port (placing section), L...laser light (light), RL...return light.

Claims

1. A holding unit is provided so as to be able to move up and down relative to the main body and for holding articles, A lifting drive unit for raising and lowering the holding unit, A recognition device that recognizes the horizontal position and the vertical position of the holding unit, An overhead transport vehicle comprising: a determination unit that determines whether the horizontal position of the holding unit recognized by the recognition device is within an acceptable range corresponding to the vertical position of the holding unit recognized by the recognition device.

2. The holding unit is provided with a reflector, The aforementioned recognition device is A sensor provided in the lifting drive unit irradiates light toward the reflector at multiple irradiation angles within a monitoring range including the reflector, and detects multiple retrograde light reflected by the reflector in response to the irradiation, The overhead transport vehicle according to claim 1, further comprising: a processing unit that determines the horizontal position and the vertical position of the holding unit based on the detection results of a plurality of retrograde lights detected by the sensor.

3. When the direction of travel of the overhead transport vehicle is defined as the X direction, and the horizontal direction perpendicular to the X direction is defined as the Y direction, The sensor irradiates light so as to scan toward the reflector in the Y direction within the monitoring range. The overhead transport vehicle according to claim 2, wherein the processing unit calculates the angle average and distance average of the optical axes of the detected plurality of regression lights, and determines the position of the holding unit in the Y direction based on the angle average and the distance average.

4. The shape of the reflector includes a shape in which the width in the Y direction differs as you move towards the X direction, The overhead transport vehicle according to claim 3, wherein the processing unit determines the position of the holding unit in the X direction based on the number of retrograde lights stored in advance and the number of retrograde lights detected.

5. (delete)

6. The overhead transport vehicle according to claim 1 or 2, further comprising a lateral transfer mechanism for moving the lifting drive unit laterally relative to the main body.

7. The aforementioned recognition device is The overhead transport vehicle according to claim 6, wherein when the lifting drive unit is moved laterally by the lateral transfer mechanism, the horizontal position of the holding unit is corrected based on a correction value stored in advance and corresponding to the inclination of the lifting drive unit.

8. The overhead transport vehicle according to claim 1 or 2, further comprising a storage unit that stores the horizontal position and the vertical position of the holding unit recognized by the recognition device in a time series for a predetermined period of time.