Moving body device

Abstract

This moving body device is provided with: a guide unit extending in a prescribed direction; a moving body that moves in the prescribed direction along the guide unit; and a drive unit that drives the moving body in the prescribed direction. The moving body device is provided with a control unit that controls the driving of the moving body by the drive unit on the basis of a predetermined pattern. The pattern is determined in advance such that, when a change in acceleration is started from a state in which the acceleration of the moving body is constant, a first acceleration change is performed and subsequently a second acceleration change is performed to generate a second vibration in a direction that cancels out a first vibration in the prescribed direction generated in the moving body due to the first acceleration change.

Description

Mobile device

[0001] The present disclosure relates to a mobile device.

[0002] As one type of mobile device, for example, a stacker crane can be cited. In the stacker crane described in Patent Document 1, a lifting platform is lifted and lowered by a lifting motor. In the lifting control of the lifting platform, dynamic vibration control (opposite phase control) is performed in which vibration of the opposite phase is applied to the lifting motor so as to cancel the vibration in the height direction of the lifting platform.

[0003] Japanese Patent Application Laid-Open No. 2007-276962

[0004] In the above-described conventional vibration control, vibration of the opposite phase of the actually generated vibration is applied to the lifting motor. Therefore, the control is complicated, such as the need to adjust the control amount of the opposite phase control.

[0005] The present disclosure describes a mobile device that can suppress vibration in a predetermined direction of a moving body with simple control.

[0006] [1] One aspect of the present disclosure is a mobile device including a guide portion extending in a specified direction, a moving body moving in the specified direction along the guide portion, and a driving portion for driving the moving body in the specified direction, the mobile device including a control portion for controlling the driving of the moving body by the driving portion based on a predetermined pattern, the pattern being predetermined such that when starting a change in acceleration from a state where the acceleration of the moving body is constant, a first acceleration change is performed, and subsequently, a second acceleration change is performed in a direction to cancel a first vibration in the specified direction generated in the moving body by the first acceleration change to generate a second vibration.

[0007] According to the mobile device of [1], first, a first vibration in the specified direction occurs due to the first acceleration change. Subsequently, a second vibration occurs due to the second acceleration change, and the first vibration is somewhat canceled. The control portion only needs to drive the moving body based on a predetermined pattern. According to the mobile device of [1], vibration in the specified direction can be suppressed with simple control.

[0008] [2] In the mobile device described in [1] above, the specified direction is the vertical direction, and the mobile body may be a lifting platform that moves vertically along the guide. With this configuration, vertical vibrations can be suppressed with simple control by driving the lifting platform based on a predetermined pattern.

[0009] [3] In the mobile device described in [2] above, the lifting platform may transport the article by moving it vertically while supporting the article. With this configuration, vertical vibrations can be suppressed with simple control even when transporting the article.

[0010] [4] In the mobile device described in [3] above, a first pattern corresponding to the case where an article is placed on the lifting platform and a second pattern corresponding to the case where no article is placed on the lifting platform are predetermined, and the control unit may control the driving of the lifting platform by the drive unit based on the first pattern when an article is placed on the lifting platform, and control the driving of the lifting platform by the drive unit based on the second pattern when no article is placed on the lifting platform. With this configuration, appropriate vibration suppression control can be performed according to the presence or absence of an article on the lifting platform, that is, according to the total weight of the mobile device including the article.

[0011] [5] In any one of the mobile device described in [1] to [4] above, multiple patterns are predetermined, each corresponding to the stopping position of the mobile body after movement. The control unit may select one of the multiple patterns according to the stopping position of the mobile body and control the driving of the mobile body by the drive unit based on that pattern. There is a correlation between the stopping position of the mobile body and its natural frequency. By configuring it as described above, vibrations in a specified direction can be efficiently suppressed with simple control that only requires selecting a pattern.

[0012] [6] In any one of the moving body devices described in [1] to [5] above, the pattern may include a section in which the maximum speed of the moving body within the pattern is maintained, and the first acceleration change and the second acceleration change may be set within the range of a deceleration section that includes the end of the section and follows the section. The moving body often performs some action at the end of the deceleration section, i.e., when it stops. If vibration suppression control is performed within the range of the deceleration section, the action when it stops can be performed smoothly.

[0013] According to this disclosure, vibrations in a specified direction can be suppressed with simple control.

[0014] Figure 1 is a front view of a mobile device according to one embodiment of the present disclosure. Figure 2 is a block diagram of the control unit and drive unit of the mobile device of Figure 1. Figure 3 is a diagram showing the range of the stopping position after movement, which serves as the basis for pattern selection. Figure 4 is a diagram showing one example pattern. Figure 5 is a diagram showing an enlarged view of the speed from the start of deceleration to the time of stopping in the pattern example of Figure 4. Figure 6 is a table showing the time difference between the first and second acceleration changes according to the stopping position after movement. Figure 7(a) is a diagram showing an example of speed control during acceleration, and Figure 7(b) is a diagram showing an example of speed control during deceleration. Figure 8(a) is a diagram showing an example of speed control at the start of deceleration, Figure 8(b) is a diagram schematically showing two examples of vibration waveforms generated by the first and second acceleration changes, and Figure 8(c) is a diagram schematically showing a composite waveform example of the two vibration waveform examples in Figure 8(b).

[0015] Embodiments of this disclosure will be described below with reference to the drawings. In the description of the drawings, the same elements will be denoted by the same reference numerals, and redundant descriptions will be omitted.

[0016] First, with reference to Figure 1, a stacker crane 1 as an example of a mobile device will be described. In some figures, mutually orthogonal X, Y, and Z axes may be shown together for convenience of explanation. In this embodiment, the X direction corresponds to the travel direction (horizontal direction) of the stacker crane 1, the Y direction corresponds to the transfer direction (horizontal direction) of the stacker crane 1 by the transfer device 23, and the Z direction corresponds to the lifting direction of the lifting platform 20 of the stacker crane 1. In the following description, the lifting platform 20 will be used as an example of the "mobile body" described in the claims, the lifting direction of the lifting platform 20 will be used as an example of the "specified direction," and vibration suppression of the lifting platform 20 in that direction will be described. Also, the terms "front and back" are used with reference to the X direction, and the terms "left and right" are used with reference to the Y direction.

[0017] If we consider the stacker crane 1 as an example of a moving body, the direction of travel of the stacker crane 1 corresponds to the "specified direction." If we consider the transfer device 23 as an example of a moving body, the direction of transfer by the transfer device 23 corresponds to the "specified direction." In either case, vibration of the moving body can be suppressed by performing speed control according to a predetermined speed pattern (speed control pattern according to time or position) based on the concept described below.

[0018] The stacker crane 1 is applied, for example, to an automated warehouse. The stacker crane 1 transfers goods (articles) W to shelves (not shown) of a rack in the automated warehouse. The rack extends in both the X and Z directions. The stacker crane 1 is movable in the X direction along a lower rail 100 laid on the floor and extending in the X direction, and an upper rail 101 supported by a fixed object at a high place such as the ceiling and extending in the X direction. The stacker crane 1 has two masts (guide parts) 3 that extend in the Z direction between the lower rail 100 and the upper rail 101. A base 2 connects the lower ends of the two masts 3. The base 2 is fitted or engaged with the lower rail 100 via a plurality of drive wheels 8, etc. On the other hand, a support beam 4 connects the upper ends 3a of the two masts 3 via a plurality of brackets 10. The support beam 4 is fitted or engaged with the upper rail 101 via a plurality of upper wheels 9, etc. The stacker crane 1 is equipped with two travel motors 5 fixed to the front and rear of the base 2. Each travel motor 5 drives the stacker crane 1 in the travel direction by rotating a drive wheel 8. The upper wheel 9 is, for example, a driven wheel, but an upper travel motor may also be provided on the upper bracket 10, and the upper wheel 9 may be rotated by the upper travel motor.

[0019] The stacker crane 1 includes a lifting platform 20 provided between two masts 3 spaced apart in the X direction. The lifting platform 20 has a horizontal frame 21 that is rectangular in plan view, and a pair of vertical frames 22 integrated with the front and rear ends of the horizontal frame 21. A transfer device 23 for transferring loads W is mounted on the horizontal frame 21. Each vertical frame 22 is fitted with a plurality of first guide rollers 27 arranged vertically and a plurality of second guide rollers 26 arranged horizontally. Each first guide roller 27 sandwiches a guide portion 3b that protrudes from the left and right sides of each mast 3 and extends in the Z direction. Each second guide roller 26 abuts against the guide portion 3b of each mast 3. The lifting platform 20 may be provided with other guide rollers or other members that abut against the masts 3, etc.

[0020] Each bracket 10 is fitted with a plurality of pulleys 11 that are rotatable around an axis extending, for example, in the Y direction. Each pulley 11 is located near the upper end of the mast 3. Two lifting motors 6 and a drum (not shown) are fixed to the front and rear of the base 2 described above. The base ends of at least one timing belt 15 is provided at the front and rear, and the ends of the timing belts 15 are fixed to the drum, and the tips of the timing belts 15 are fixed to the vertical frame 22 of the lifting platform 20. Each timing belt 15 is wrapped around the drum and also around the pulleys 11, suspending and supporting the lifting platform 20. The lifting platform 20 is able to maintain a position substantially parallel to the XY plane (horizontal position) by the various rollers described above.

[0021] The lifting platform 20 is movable up and down in the Z direction along the two masts 3. The lifting platform 20 transports goods by moving up and down while supporting the load W. Each lifting motor (drive unit) 6 drives the lifting platform 20 up and down by rotating the drum. For example, the lifting motor 6 can rotate in both forward and reverse directions, allowing the lifting platform 20 to be raised freely and lowered freely. In addition, other known mechanisms other than those described above may be used as the mechanism for supporting and guiding (guiding in the Z direction) the lifting platform 20, and the mechanism for driving the lifting platform 20 up and down.

[0022] The transfer device 23 also has similar configurations, although it is not shown in the illustration. Specifically, the transfer device 23 comprises a guide section such as a slide bar or slide guide extending in the Y direction, a movable body such as a mounting table that moves (extends or retracts) in the Y direction along the guide section, and a drive unit such as a motor that drives the movable body.

[0023] Next, the configuration related to the speed control of the lifting platform 20 will be described with reference to Figures 2 and subsequent figures. As shown in Figure 2, the stacker crane 1 is equipped with a control unit 30. The control unit 30 is a computer or electronic control unit that includes, for example, a processor such as a CPU (Central Processing Unit), ROM (Read Only Memory), and RAM (Random Access Memory). The control unit 30 is housed, for example, inside a suitable enclosure attached to the base 2. The control unit 30 controls the driving of the stacker crane 1 by the travel motor 5 and the driving of the lifting platform 20 by the lifting motor 6. The control unit 30 has an information acquisition unit 31, a pattern determination unit 32, a motor control unit 33, and a storage unit 36. The information acquisition unit 31 acquires information related to transport commands from, for example, a higher-level controller (not shown). The transport command includes information relating to the location (From position) of the shelf or transfer port or station where the load W to be transported by the stacker crane 1 is stored, and information relating to the location (To position) of the destination shelf or transfer port or station to which the load W will be transported. The pattern determination unit 32 selects one of a plurality of patterns relating to the moving body (details will be described later) that are stored in advance in the storage unit 36. The motor control unit 33 controls the lifting motor 6 (or the travel motor 5 if the moving body is the stacker crane 1) according to the pattern selected by the pattern determination unit 32. In this embodiment, "pattern" means a speed control pattern relating to the transport operation of a moving body to which a certain transport command has been assigned.

[0024] Figure 4 shows an example of a pattern. As shown in Figure 4, the pattern generally includes an initial stopping section, an acceleration section, a maximum speed maintenance section, a deceleration section, and a final stopping section in this order. In the example shown in Figure 4, the initial stopping section is until time t1a, the acceleration section is from time t1a to t2b, the maximum speed maintenance section is from time t2b to t3a, the deceleration section is from time t3a to t4b, and the final stopping section is from time t4b onward. Thus, all transport operations fit into this roughly trapezoidal pattern. Note that in Figure 4 (and Figures 5 and 8), an example of the lifting platform 20 descending is shown, so the direction in which the vertical axis (speed) decreases corresponds to the direction of movement of the lifting platform 20. That is, "Va" in "-Va" shown on the vertical axis is a positive value and is the absolute value of the speed. Therefore, the speed during processing is a negative value. The above maximum speed means that the absolute value of the speed is at its maximum.

[0025] The memory unit 36 ​​stores multiple patterns. The pattern selection in this embodiment is provided based on two perspectives. From the first perspective, multiple patterns are predetermined, each corresponding to the stopping position of the lifting platform 20 after movement. As shown in Figure 3, three ranges (regions) are defined as the stopping position after movement, starting from the one closest to the pulley 11 (the higher one, i.e., the one with the shortest hanging length from the pulley 11): upper range RC, middle range RB, and lower range RA. The upper range RC, middle range RB, and lower range RA are set, for example, between the upper limit position PH and the lower limit position PL.

[0026] The "position of the lifting platform 20" can be determined based on any specific point on the lifting platform 20 in the Z direction. For example, the "position of the lifting platform 20" may be the height position of the mounting surface on the transfer device 23. Alternatively, the "position of the lifting platform 20" may be the height position of the bottom surface of the horizontal frame 21 on the transfer device 23. Regardless of which point is set as the reference, the control unit 30 can determine the current position of the lifting platform 20 through calculation. As shown in Figure 1, at least two laser distance meters 28 are mounted on the side of the base 2, spaced apart in the X direction, and at least two reflectors 29 are mounted on the bottom surface of the horizontal frame 21 at positions corresponding to the X-direction positions of each laser distance meter 28.

[0027] In the multiple patterns prepared to correspond to the stopping position after the movement of the lifting platform 20, as shown in Figure 4, the timing of the acceleration change in each acceleration change control, specifically the time difference, is different when switching from the stopping section to the acceleration section (hereinafter referred to as acceleration start), when switching from the acceleration section to the maximum speed maintenance section (hereinafter referred to as constant speed arrival), when switching from the maximum speed maintenance section to the deceleration section (hereinafter referred to as deceleration start), and when switching from the deceleration section to the final stopping section (hereinafter referred to as stopping).

[0028] In all four of the above scenarios, the pattern is predetermined to perform a first acceleration change when the acceleration of the lifting platform 20 starts to change from a state where the acceleration is constant, followed by a second acceleration change to generate a second vibration in a direction that cancels out the first vibration in a predetermined direction that was generated in the moving body by the first acceleration change. The time difference mentioned above is the difference between the time when the second acceleration change occurs and the time when the first acceleration change occurs. A more detailed explanation follows.

[0029] In this embodiment, as an example, it is assumed that in a given pattern, the same amount of time is applied at the start of acceleration, when a constant speed is reached, when deceleration begins, and when stopping. An example will be described with reference to Figures 3, 5, 6 and 8(a) to 8(c). In the following description, the "position of the lifting platform 20" will be described as the height position of the mounting surface on the transfer device 23. Now, let's assume that the From position is included in the upper range RC and the To position is included in the lower range RA. In that case, the pattern determination unit 32 selects a frequency corresponding to the lower range RA from a predetermined table shown in Figure 6, based on the information related to the transport command acquired by the information acquisition unit 31.

[0030] Here, a second perspective is also necessary (and is incorporated) when selecting the frequency. From this second perspective, two patterns are predetermined: a first pattern corresponding to the case where a load W is placed on the lifting platform 20 (loaded) and a second pattern corresponding to the case where a load W is not placed on the lifting platform 20 (unloaded). Now, let's assume that a load W is not placed on the lifting platform 20. The pattern determination unit 32 selects the "13 Hz" pattern, which corresponds to the lower range RA and the case where there is no load.

[0031] The difference between times t3a and t3b shown in Figure 8(a) is half the reciprocal of 13 Hz. As shown in Figure 8(b), the motor control unit 33 controls the lifting motor 6 to perform a first acceleration change at time t3a, with a time difference of half the reciprocal of 13 Hz (a time difference based on the reciprocal), and then controls the lifting motor 6 to perform a second acceleration change at time t3b. Through this two-stage acceleration change control with a predetermined time difference, as shown in Figure 8(c), the second vibration acts in a direction that cancels out the first vibration. As a result, the amplitude is gradually attenuated. Note that the velocity is constant (unchanged) at -Va until time t3a, so the acceleration is zero. From time t3b onward, the velocity increases with a constant acceleration.

[0032] As shown in Figure 6, the longer the stopping position of the lifting platform 20 after movement (lower when viewed from the ground), the lower the frequency is set. In other words, the longer the stopping position of the lifting platform 20 after movement, the longer the time difference is set. Also, the frequency is set lower when there is a load compared to when there is no load. In other words, the time difference is set longer when there is a load than when there is no load. Note that this is not limited to the three ranges (regions) of upper range RC, middle range RB, and lower range RA. The vertical length separating each range and the number of ranges may be adjusted as appropriate.

[0033] As described above, the pattern determination unit 32 selects one of several patterns according to the stopping position of the lifting platform 20, and the motor control unit 33 controls the driving of the lifting platform 20 by the lifting motor 6 based on the selected pattern. There is a correlation between the stopping position of the lifting platform 20 and its natural frequency. With the above configuration, vibrations in a specified direction can be efficiently suppressed with simple control that only requires selecting a pattern.

[0034] Furthermore, if a load W is placed on the lifting platform 20, the pattern determination unit 32 selects the first pattern (the pattern with a load shown in Figure 6), and the motor control unit 33 controls the driving of the lifting platform 20 by the lifting motor 6 based on the first pattern. If no load W is placed on the lifting platform 20, the pattern determination unit 32 selects the second pattern (the pattern without a load shown in Figure 6), and the motor control unit 33 controls the driving of the lifting platform 20 by the lifting motor 6 based on the second pattern. With this configuration, appropriate vibration suppression control can be performed according to the presence or absence of a load W on the lifting platform 20, that is, according to the total weight of the moving body including the load W. Although the control unit 30 is aware of the presence or absence of a load W, it is not aware of its weight. Nevertheless, speed control and vibration suppression control can be performed without any problems.

[0035] In actual speed control, as shown in Figure 7(a), a pattern is determined for acceleration based on time, and speed control is performed accordingly. On the other hand, as shown in Figure 7(b), a pattern is determined for deceleration based on the remaining distance to the To position (remaining distance), and speed control is performed accordingly. In Figures 7(a) and 7(b), the vertical axis is defined differently from (reversed from) Figure 4 (Figures 5 and 8), and the direction in which the vertical axis (speed) increases corresponds to the direction of movement of the lifting platform 20, even when descending.

[0036] In the stacker crane 1 of this embodiment, a first vertical vibration occurs due to a first change in acceleration, followed by a second vibration due to a second change in acceleration, which somewhat cancels out the first vibration. The control unit 30 only needs to drive the lifting platform 20 based on a predetermined pattern. With the stacker crane 1, vertical vibrations can be suppressed with simple control.

[0037] Even when transporting the load W using the lifting platform 20, vertical vibrations can be suppressed with simple control.

[0038] Furthermore, the pattern includes a section within the pattern where the elevator platform 20 maintains its maximum speed, and the first and second acceleration changes are set within the range of the deceleration section that includes the end point of the maximum speed maintenance section (time t3a shown in Figure 5) and follows the maximum speed maintenance section. At the end point of the deceleration section, i.e., when stopping (time t4b shown in Figure 5), the elevator platform 20 often performs some kind of operation. If vibration suppression control is performed within the range of the deceleration section, the operation when stopping can be performed smoothly.

[0039] Although embodiments of the present disclosure have been described above, the present invention is not limited to the above embodiments. For example, the speed control of the present disclosure may be applied to the speed control of each moving body in an overhead transport vehicle, not limited to the stacker crane 1. For example, the X direction corresponds to the travel direction (horizontal direction) of the overhead transport vehicle, and the Y direction corresponds to the lateral transfer direction (horizontal direction) of the overhead transport vehicle. If the overhead transport vehicle is considered as an example of a moving body, the travel direction of the overhead transport vehicle corresponds to the "specified direction". If the lateral transfer device is considered as an example of a moving body, the transfer direction by the lateral transfer device corresponds to the "specified direction". In either case, vibration of the moving body can be suppressed by performing speed control according to a predetermined speed pattern (speed control pattern according to time or position) based on the above concept.

[0040] 1...Stacker crane (moving device), 3...Mast (guide unit), 20...Lifting platform (moving unit), 6...Lifting motor (drive unit), 30...Control unit.

Claims

1. A mobile body device comprising a guide portion extending in a specified direction, a mobile body moving along the guide portion in the specified direction, and a drive unit for driving the mobile body in the specified direction, wherein the device comprises a control unit that controls the driving of the mobile body by the drive unit based on a predetermined pattern, the pattern being predetermined to perform a first acceleration change when the acceleration of the mobile body starts to change from a state where the acceleration is constant, and then perform a second acceleration change to generate a second vibration in a direction that cancels out the first vibration in the specified direction generated in the mobile body by the first acceleration change.

2. The specified direction is the vertical direction, and the moving body is a lifting platform that moves vertically along the guide portion, as described in claim 1.

3. The mobile device according to claim 2, wherein the lifting platform transports an article by moving it vertically while supporting the article.

4. The mobile device according to claim 3, wherein a first pattern corresponding to the case where an article is placed on the lifting platform and a second pattern corresponding to the case where no article is placed on the lifting platform are predetermined, and the control unit controls the driving of the lifting platform by the drive unit based on the first pattern when an article is placed on the lifting platform, and controls the driving of the lifting platform by the drive unit based on the second pattern when no article is placed on the lifting platform.

5. The mobile body device according to any one of claims 1 to 4, wherein a plurality of patterns are predetermined, each corresponding to the stopping position of the mobile body after movement, and the control unit selects one of the plurality of patterns according to the stopping position of the mobile body, and controls the driving of the mobile body by the drive unit based on that pattern.

6. The mobile device according to any one of claims 1 to 4, wherein the pattern includes a section in which the maximum speed of the mobile body within the pattern is maintained, and the first acceleration change and the second acceleration change are set within the range of a deceleration section that includes the end point of the section and follows the section.

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