Material handling system

Abstract

To provide a material handling and / or storage and recovery process.SOLUTION: A material handling system may comprise transportation vehicles 100 for transporting items and a plurality of storage racks 800 having a plurality of storage places. The storage racks may be arranged so as to form one or more passages. Each transportation vehicle may be configured to be horizontally driven along a route, and this route may extend along a route below the storage racks parallel to the passage(s). Further, each transportation vehicle may be operated so as to rotate while arranged under one of the storage racks. Each transportation vehicle may move under the storage racks, cross the one or more passages, and reach one specified vertical row of the passages. Each transportation vehicle moves upward in the specified vertical row, and recovers the item(s) from the storage place in the vertical row.SELECTED DRAWING: Figure 8

Description

REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority under 35 U.S.C. § 119 to U.S. Provisional Patent Application No. 62 / 886,602, filed August 14, 2019. The entire disclosure of US Patent Application No. 62 / 886,602 is incorporated herein by reference. [Technical Field]

[0002] The present invention relates generally to automated material and article handling systems that may be used in warehouse, storage, and / or distribution environments. [Background technology]

[0003] Modern material handling systems, such as those used in mail order warehouses, supply chain distribution centers, and custom manufacturing facilities, face significant challenges in meeting inventory requests. Typically, companies invest in automation in their early stages to a level that is sufficient for at least their current needs. However, as the size of an inventory control system expands to accommodate a greater number and variety of items, the cost and complexity of operating the inventory control system to simultaneously complete the packing, storing, replenishment, and other inventory control tasks for which it is intended increases.

[0004] Inefficient utilization of resources such as space, equipment, and labor in inventory management facilities results in slower throughput, longer response times, and a growing backlog of uncompleted tasks. Temporary increases in efficiency may often be achieved by gradually increasing the capacity of a facility's existing automation infrastructure, especially if this increase follows a well-thought-out growth plan. But sooner or later, you hit a point of diminishing returns. That is, achieving further increases in capacity and / or functionality, if such increases are feasible at all, becomes prohibitively expensive compared to available alternatives. A point of diminishing returns may be reached, forcing facility operators to retire their existing material handling infrastructure and replace it with an entirely new automation platform. Summary of the Invention

[0005] The present invention provides a number of inventions relating to material handling and / or storage and retrieval processes.

[0006] According to one aspect, the present invention provides a method for transporting items to and retrieving items from a storage location. The method may include providing a plurality of storage racks spaced apart from one another to form a plurality of aisles. Each storage rack may include multiple vertical rows, and each vertical row may include multiple storage locations. The method may include providing a plurality of haul vehicles, each including a horizontal drive mechanism operable to drive the haul vehicle along a horizontal plane. The transport vehicle may then include a vertical drive mechanism operable to drive the transport vehicle vertically, and a loading and unloading mechanism operable to move items between the transport vehicle and one of the storage locations. The method may include driving a first one of the transport vehicles to drive the first transport vehicle to a storage rack. The method includes driving a first transport vehicle along a first path beneath one of the storage racks, the first storage rack being adjacent to a first aisle of one of the aisles, the first path extending away from the first aisle in a direction parallel to the first aisle. The method may include rotating the first transport vehicle while the first transport vehicle is beneath the first storage rack. The method further includes driving a first transport vehicle into a first aisle and driving the first transport vehicle up the aisle to a first storage location of one of the storage locations. The items may be moved between the first transport vehicle and the first storage location. The first transport vehicle may then be driven downwardly within the aisle until it is positioned at a horizontal surface. The first transport vehicle may then traverse the first aisle and then exit from under the storage rack after the step of driving the first transport vehicle across the first aisle.

[0007] According to another aspect, a method of transporting items may include a plurality of vertical columns forming a first vertical row of a first storage rack, and a first transport vehicle having a first width extending from a first side of the first transport vehicle to a second side of the first transport vehicle. The first transport vehicle may include a vertical drive mechanism that protrudes outward from the first and second sides to have a second width corresponding to the distance between outer edges of the vertical drive mechanism, the second width being greater than the first width, and the vertical columns of the first vertical row are spaced apart by a distance greater than the first width and less than the second width.

[0008] According to yet another aspect, a method of transporting items may include a plurality of vertical track sections attached to a plurality of vertical posts in a first vertical row, and may include aligning a vertical drive mechanism of a first transport vehicle with the vertical track sections.

[0009] According to another aspect, the present invention may provide a method of transporting items, including driving a first portion of a vertical drive mechanism of a first transport vehicle through a vertical track section and driving a second portion of the vertical drive mechanism into operative engagement with the vertical track section.

[0010] According to a further aspect, a method of transporting items may include driving a first transport vehicle along a first path by driving the first transport vehicle along a path spaced from the vertical post by a distance greater than half the length of the first transport vehicle.

[0011] According to yet another aspect, a method of transporting an item may include driving a first transport vehicle out from under a storage rack, and then driving the first transport vehicle to a work site to hand over the item to an operator.

[0012] According to a further aspect, a method of transporting items may include driving a first transport vehicle across a first aisle by driving the first transport vehicle under a second storage rack of the storage racks.

[0013] According to another aspect, a method of transporting items may include rotating a first transport vehicle by rotating the first transport vehicle about a vertical axis extending through the first transport vehicle. The vertical axis may extend through a first path.

[0014] According to a further aspect, a method of transporting items may include driving a second transport vehicle under a first storage rack along a second path parallel to the first path such that the second transport vehicle passes the first transport vehicle as the first transport vehicle travels along the first path.

[0015] According to a further aspect, a material handling system for transporting items to and retrieving items from a storage location is provided. The material handling system may include a first storage rack extending longitudinally and having a plurality of vertical rows, each row including a plurality of storage locations, and a second storage rack extending longitudinally and having a plurality of vertical rows, each row including a plurality of storage locations. The second storage rack may be spaced apart from the first storage rack to provide a passageway between the first and second storage racks. Additionally, the material handling system may include a plurality of transport vehicles. Each transport vehicle has a length and a width, and each transport vehicle may have a horizontal drive mechanism operable to drive the transport vehicle along a horizontal plane, a vertical drive mechanism operable to drive the transport vehicle vertically, and a loading and unloading mechanism operable to move items between the transport vehicle and one of the storage locations. And, the material handling system may include a track disposed in the aisle. Additionally, the vertical drive mechanism may be configured to drive the transport vehicle vertically upward in cooperation with the track. The material handling system may include a first horizontal path extending below the first storage rack in a direction parallel to the aisle, and a second horizontal path extending below the first storage rack in a direction parallel to the aisle. The horizontal drive mechanism may be configured to rotate the transport vehicle under the first storage rack by rotating the transport vehicle about a vertical axis extending through the transport vehicle. Additionally, the first storage rack may include a plurality of vertical posts, and the first horizontal path and the second horizontal path may each be spaced apart from the vertical posts by a distance greater than half the length of the transport vehicle. Additionally, the first horizontal path beneath the first storage rack may be spaced apart from the second horizontal path by a distance greater than the width of the transport vehicle.

[0016] According to a further aspect, a material handling system for transporting items may include a vertical drive mechanism having a plurality of rotating members each rotating about a horizontal axis. Additionally, the material handling system may include a horizontal drive mechanism including a plurality of rotating members each rotating about a horizontal axis transverse to the axis of rotation of the vertical drive member.

[0017] According to yet another aspect, the present invention may provide a material handling system for transporting items, including a plurality of vertical columns forming a first vertical row of a first storage rack, and a transport vehicle having a first width extending from a first side of the transport vehicle to a second side of the transport vehicle. The vertical drive mechanism of the transport vehicle may protrude outward from the first side and the second side so that the transport vehicle has a second width corresponding to the distance between the outer edges of the vertical drive mechanism, the second width being greater than the first width. The vertical posts in the first vertical row are spaced apart by a distance greater than a first width and less than a second width.

[0018] According to a further aspect, a material handling system for transporting items may include a track including a plurality of drive members configured to cooperate with a vertical drive mechanism such that rotation of the vertical drive mechanism about a horizontal axis functions to drive a transport vehicle upwardly along the track. The track then includes an upper portion and a lower portion, with the drive members being spaced further apart at the lower portion than at the upper portion to provide clearance at the lower portion.

[0019] The gap is configured to facilitate the vertical drive mechanism passing through the gap without contacting the underside as the transport vehicle drives past the underside.

[0020] According to an additional aspect, the present invention may provide a method for transporting items to and retrieving items from a storage location. The method may include providing a transport vehicle having a horizontal drive mechanism and a vertical drive mechanism including a front rotating member adjacent a front end of the transport vehicle and a rear rotating member adjacent a rear end of the transport vehicle, and providing a first vertical track on a first side of a first vertical row. The first vertical track may include a drive member configured to cooperate with the front rotating member to drive the transport vehicle upwardly. The method may include providing a second vertical track on a second side of the first vertical row having a drive member configured to cooperate with the rear rotating member to drive the transport vehicle upwardly. The vertical drive mechanism and the first and second vertical tracks may be configured such that when the vertical drive mechanism is rotated misaligned, the vertical tracks impede displacement of the transport vehicle along the horizontal tracks. Further, the method may include a step of aligning the vertical drive mechanism, the step of aligning the vertical drive mechanism may include a step of rotating a front rotating member about a horizontal axis that is substantially parallel to the horizontal path to align the front rotating member with the gaps in the first vertical track and the second vertical track, and a step of rotating a rear rotating member about a horizontal axis that is substantially parallel to the horizontal path to align the rear rotating member with the gaps in the first vertical track and the second vertical track. After the step of aligning the vertical drive mechanism, the method may include driving a transport vehicle along the horizontal path toward a first vertical track. Driving the transport vehicle may include driving the transport vehicle so that a front rolling member passes through a gap in a second vertical track. The method may include continuing to drive the transport vehicle along the horizontal path such that the front rotating member is operably engaged with the first track and the rear rotating member is operably engaged with the second track. The front and rear rotating members may be rotated to drive the transport vehicle upwardly toward a first storage location. Further, the first item may be transported from the first storage location to a transport vehicle, which may be driven downwardly with the first item loaded thereon, and the transport vehicle may be driven along a horizontal path with the first item loaded thereon such that the rear rotating member passes through a gap in the first vertical track.

[0021] According to yet another aspect, a method of transporting items may include synchronously driving a front rotating member and a rear rotating member to rotate the front rotating member and the rear rotating member to drive the transport vehicle vertically upward while maintaining the orientation of the transport vehicle relative to the horizontal.

[0022] According to yet another aspect, a method of transporting an item may include driving a transport vehicle carrying the first item along a horizontal path, and then driving the transport vehicle out from under a storage rack.

[0023] According to another aspect, a method of transporting items may include steering a transport vehicle along a path that is perpendicular to a horizontal path along which the transport vehicle is traveling. The step of directing the transport vehicle may occur while the transport vehicle is located beneath one of a plurality of storage racks.

[0024] According to a further aspect, a method of transporting items may include driving a transport vehicle along a horizontal path. Driving the transport vehicle along the horizontal path may include rotating a plurality of horizontal drive members about horizontal axes generally perpendicular to the horizontal path.

[0025] According to an additional aspect, a method of transporting items may include providing a plurality of storage racks and providing a plurality of transport vehicles. The storage racks may be spaced apart to form a plurality of aisles, each storage rack may include a plurality of vertical columns, and each vertical column may include a plurality of storage locations. And, each transport vehicle may include a horizontal drive mechanism operable to drive the transport vehicle along a horizontal plane. Each transport vehicle may also include a vertical drive mechanism operable to drive the transport vehicle vertically. Additionally, the aforementioned transfer mechanism may be operable to move items between the transport vehicle and one of the storage locations. The method may include driving a first one of the transport vehicles under one or more storage racks along a path that intersects one or more aisles. And, driving the first transport vehicle may include driving the first transport vehicle into a first vertical row of vertical rows in a first aisle of the aisles. The first transport vehicle may also be driven vertically upward in the first aisle until the first transport vehicle is adjacent to a first storage location of one of the storage locations. The items may be transported from the first storage location to the first transport vehicle. The first transport vehicle may then be driven vertically downward within the first aisle and then driven through a path extending under at least one of the storage racks and expelled from the first aisle.

[0026] According to yet another aspect, a method for transporting items may include a path that passes under one of the storage racks and includes a portion that extends parallel to one of the aisles. The second transport vehicle may pass the first transport vehicle under one of the storage racks as the first transport vehicle drives along the portion of the path under the one of the storage racks.

[0027] According to a further aspect, a method of transporting items may include rotating a first transport vehicle while the first transport vehicle is beneath one of the storage racks. And, the step of rotating the first transport vehicle may include rotating the first transport vehicle to align the first transport vehicle with an aisle perpendicular to the first aisle. The step of rotating the first transport vehicle may include rotating the first transport vehicle about a vertical axis passing through the first transport vehicle. [Brief explanation of the drawings]

[0028] For a more detailed understanding of the invention, briefly summarized above, a more particular description of the invention may be made by reference to the embodiments illustrated in the drawings. However, the accompanying drawings merely show typical embodiments of the present invention, and the present invention may allow other embodiments, so the scope of the present invention is not limited thereto.

[0029] FIG. 1 is a perspective view of a material handling system.

[0030] FIG. 2 is a perspective view of an automated guided vehicle of the material handling system shown in FIG.

[0031] FIG. 3 is a rear view of the automated guided vehicle shown in FIG.

[0032] FIG. 4 is a side view of the automated guided vehicle shown in FIG.

[0033] FIG. 5 is a plan view of the automated guided vehicle shown in FIG.

[0034] 6 is an enlarged, partial perspective view of the rack portion of the material handling system shown in FIG.

[0035] 7 is a front view of an aisle of the rack system of the material handling system shown in FIG. 1. FIG.

[0036] FIG. 8 is a side view of the passage shown in FIG.

[0037] FIG. 9 is a plan view of the passage shown in FIG.

[0038] FIG. 10 is an enlarged partial side view of the passage shown in FIG.

[0039] FIG. 11 is a block diagram illustrating subsystems of multiple automated guided vehicles according to one or more embodiments.

[0040] FIG. 12 is a simplified block diagram of the controller for the material handling system shown in FIG.

[0041] Materials handling systems and methods are described herein by way of example in the drawings. However, the material handling systems and methods for performing each subset of inventory control tasks using functional accessory modules are not limited to the embodiments and drawings. The drawings and their detailed description are not intended to limit the particular embodiments. Rather, it covers all modifications, equivalents, and alternatives falling within the scope of material handling systems and methods for performing each subset of inventory control tasks with corresponding functionally associated modules as defined by the claims. The headings used herein are for organizational purposes only and are not intended to limit the scope of the claims. As used herein, the word "may" is used in a permissive sense (i.e., meaning having the potential) rather than a mandatory sense (i.e., meaning required). Similarly, the word "comprises" means inclusive of elements, not exclusive of elements. DETAILED DESCRIPTION OF THE INVENTION

[0042] Various embodiments of a method and apparatus for performing inventory control tasks in an inventory control system are described. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of claimed subject matter. However, claimed subject matter may be practiced without these specific details. In other instances, methods, apparatus, or systems known to those skilled in the art have not been described in detail so as not to obscure claimed subject matter.

[0043] Some portions of the detailed descriptions which follow are presented in terms of algorithms or symbolic representations of operations on binary digital signals stored in a memory of a particular apparatus, special purpose computing device or special purpose computing platform. In this specification, the term specific apparatus or the like includes a general-purpose computer that is programmed to perform particular functions pursuant to instructions from program software. Algorithmic descriptions or symbolic representations are examples of techniques used by those skilled in the signal processing or related arts to convey the substance of their work to others skilled in the art. An algorithm is hereby conceived to be a self-consistent sequence of operations or similar signal processing leading to a desired result. In this context, operations or processing involve physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. Principally for reasons of common usage, these signals are referred to as bits, data, values, members, symbols, characters, terms, numbers, numerals, or the like. However, all of these and similar terms are to be associated with appropriate physical quantities and are merely convenient labels.

[0044] Unless otherwise specified, discussions herein using terms such as "processing," "computing," and "determining" refer to the actions or processes of a particular device, such as a special purpose computer or similar special purpose electronic computing device. Thus, in the context of this specification, a special purpose computer or similar special purpose electronic computing device is capable of processing or converting signals that are normally represented as physical electronic or magnetic quantities in the memory, registers, or other information storage devices, transmission devices, or displays of the special purpose computer or similar special purpose electronic computing device.

[0045] Reference will now be made in detail to the present invention, which is illustrated in the drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

[0046] Referring now to FIG. 1, a material handling system, which is a facility for storing and retrieving items, is shown at 10. The material handling system 10 includes one or more transport mechanisms for transporting items to and / or retrieving items from one of a plurality of storage locations, such as storage areas arranged in a storage rack 800 or a flow rack 600. The transport mechanism may then include one or more vehicles 100 for transporting the items. For example, the vehicle 100 may retrieve items from storage locations 820 in storage racks 800 and transport the items to a work station 500 where an operator can retrieve the items from the vehicle 100 . The vehicle 100 may then return to the storage area within the storage rack 800 to store any remaining items not retrieved by the operator. The vehicle 100 can then proceed to another storage area to retrieve the next item to be collected. Thus, material handling system 10 may include mechanisms for storing and retrieving items from various storage areas so that the items can be delivered to an operator. A guide, such as a track, may be positioned adjacent to the storage rack 800 to allow the vehicle 100 to vertically climb the storage rack 800 to retrieve items from the storage rack 800. And, the material handling system 10 may include a movable rack 700 configured to be carried by the vehicle 100 . The vehicle 100 may bring the movable rack 700 into position adjacent to the storage rack 800 . Additionally, the vehicle 100 may then vertically climb the movable rack 700 to transport items between the vehicle 100 and storage locations 820 within the storage rack 800 .

[0047] The various items and subassemblies throughout this material handling system 10 can be used alone or in combination with material handling systems having a different structure or operation than the material handling system 10 shown in the drawings and described below.

[0048] As shown in FIGS. 1 and 7, the material handling system 10 may incorporate one or more storage racks 800. Each storage rack 800 may include multiple storage locations 820 . The storage locations 820 may be arranged in one or more vertical columns 810 . For example, FIG. 1 shows a plurality of storage racks 800 , and each storage rack 800 may include a plurality of vertical columns 810 , each of which includes a plurality of storage locations 820 . Additionally, items handled by the material handling system 10 may be stored directly in storage location 820 . The items may be stored in containers or totes 55, and the storage location 820 may be configured to store totes 55, as shown in Figures 1 and 6-9. Therefore, in the following description, unless otherwise specified, when referring to a tote, the term tote is broad enough to include a container for holding one or more items, as well as items that are not necessarily contained in a container. And, although the material handling system 10 is described as using totes 55, any of a variety of storage mechanisms, such as pallets or similar platforms, may be used. <Vehicle>

[0049] FIG. 2 shows a detail of one of the vehicles 100 shown in FIG. As mentioned above, when material handling system 10 incorporates vehicle 100, the configuration of vehicle 100 may vary. Thus, each of the features of vehicle 100 described below are optional features that may be modified or removed depending on the application.

[0050] The vehicle 100 may also be an autonomous system that includes an on-board power source for powering the vehicle 100 . Vehicles 100 may also include a communications system, such as a central controller 450, for wirelessly receiving and transmitting control signals between each vehicle 100 and control members. In this manner, the vehicle 100 may receive control signals regarding the location to pick up the item and the location to which the vehicle 100 will deliver the item.

[0051] The vehicle 100 shown in FIG. 2 may include a horizontal drive assembly 120 for driving the vehicle 100 in a horizontal direction. The horizontal drive assembly 120 may then be configured to drive the vehicle 100 along a track or along an open horizontal surface, such as a floor. For example, one option for the horizontal drive assembly 120 includes a plurality of rotating members, such as wheels or rollers. One or more drive mechanisms may then be provided to change the orientation of the rotating member. Additionally, the rotating member may be steered left or right to steer the vehicle 100 .

[0052] As shown in Figures 3-5, the vehicle 100 may have a horizontal drive assembly 120 formed from a plurality of rollers 122, 123, 124 rotatable about a first axis, such as about an axle. Additionally, each roller 122, 123, 124 may be limited to rotation about a single axis. For example, in the embodiment shown in FIGS. 3-5, the horizontal drive assembly 120 includes a pair of center rollers 124 and first and second sets of outer rollers 122, 123. The first set of outer rollers 122 are positioned in front of the central roller 124, and the second set of outer rollers 123 are positioned behind the central roller 124. As shown in FIG. 3, the outer rollers 122, 123 may include outer rollers spaced apart along the length of the horizontal axis such that each set of outer rollers 122, 123 includes a first outer roller 122a on one side of the vehicle 100 and a second outer roller 122b on the opposite side of the vehicle 100. Additionally, as shown in FIG. 3, each set of outer rollers 122, 123 may include a pair of rollers 122b on each side of the vehicle 100.

[0053] As mentioned above, the vehicle 100 may have any of a number of steering mechanisms to control the direction of travel of the vehicle 100 . For example, any steering mechanism may be a zero turn mechanism that allows the vehicle 100 to change direction without substantially moving forward. The zero turn mechanism then provides a means for rotating the vehicle 100 about a vertical axis extending through the vehicle 100 .

[0054] The zero turn mechanism includes a linkage that allows the wheels or rollers on one side of the vehicle 100 to rotate at a different speed than the wheels or rollers on the other side of the vehicle 100 . The linkage then allows the wheels or rollers on one side of the vehicle 100 to rotate in a different direction than the wheels or rollers on the other side of the vehicle 100 . In this manner, by changing the speed and / or direction of rotation of the wheels or rollers on one side of the vehicle 100 relative to the speed and / or direction of rotation of the wheels or rollers on the opposite side of the vehicle 100, the zero turn mechanism changes direction and steers the vehicle 100.

[0055] And, the material handling system 10 may include one or more guides 880 that guide or align the vehicle 100 as it moves forward. For example, with reference to FIG. 9, the guide 880 may include a route or groove, and the vehicle 100 may include corresponding guide members that cooperate with the guide 880 to control the movement of the vehicle 100. An example of a guide member is the follower 126 . The follower 126 may then be any member configured to engage or cooperate with the guide 880 . The vehicle 100 includes a central follower 126 that includes a rotating member, such as a bearing, that rotates about a vertical axis. This central follower 126 engages a route within the guide 880 to restrain the vehicle 100 from moving horizontally.

[0056] Additionally, the vehicle 100 may include one or more side guide members 127 . The side guide member 127 may cooperate with the outer surface of the guide 880 to restrict movement of the vehicle 100 . For example, guide 880 may include a circular guide having a periphery for guiding the rotation of vehicle 100 . The vehicle 100 may also have a pair of side guide members 127 spaced apart by a distance equal to the diameter of the periphery of the guide 880 . In this way, the side guide member 127 engages with the circumferential surface of the guide 880 and prevents the vehicle 100 from rotating.

[0057] In addition to the horizontal drive mechanism 120 of the horizontal drive assembly described above, the vehicle 100 may include a vertical drive mechanism 140 for driving the vehicle 100 vertically within the storage rack 800 . In particular, as mentioned above, material handling system 10 may include a vertical guide mechanism, such as track 840 , positioned adjacent storage rack 800 . The vertical drive mechanism 140 may work in conjunction with a vertical guide mechanism 840 to drive the vehicle 100 vertically.

[0058] 2-3 show vertical drive mechanism 140 including multiple rotatable vertical drive gears 145, but vertical drive mechanism 140 may include any of multiple drive mechanisms for driving vehicle 100 vertically. Referring to FIG. 3, vertical drive mechanism 140 may include a vertical drive gear 145 that rotates about a horizontal axis that is transverse to the horizontal axis of rotation of horizontal drive mechanism 120 . In particular, as shown in FIG. 3, vehicle 100 includes a pair of vertical drive gears 145 spaced apart from one another such that teeth of a first vertical drive gear of one of vertical drive gears 145b protrude outward from a first side of vehicle 100 and teeth of a second vertical drive gear of one of vertical drive gears 145d protrude outward from a second side of vehicle 100. The first vertical drive gear 145b and the second vertical drive gear 145d are driven in synchronization with each other. Additionally, as shown in FIG. 2, the vehicle 100 may include two pairs of vertical drive members spaced apart along the length of the vehicle 100. In particular, vehicle 100 includes a pair of vertical drive members 145a, a first pair of vertical drive members 145c at a first end of vehicle 100, and a pair of vertical drive members 145b, a second pair of vertical drive members 145d at a second end of vehicle 100.

[0059] 1 and 6-7, storage rack 800 may be configured such that tracks 840a on the first storage rack are spaced apart from tracks 840b on the second storage rack by a distance corresponding to the spacing between first set of vertical drive members 145a and second set of vertical drive members 145b. In this manner, the first vertical drive member 145a cooperates with the first track 840a to drive the vehicle 100 up the first track 840a, and the second vertical drive member 145b cooperates with the second track 840b to drive the vehicle 100 up the second track 840b. The two vertical drive members 145a and 145b are driven synchronously so that the vehicle 100 maintains the horizontal direction when changing from horizontal movement to vertical movement.

[0060] As described in U.S. Provisional Patent Application No. 62 / 886,602, the entire disclosure of which is set forth therein, the vertical drive mechanism 140 may be configured such that the vertical drive mechanism 140 has a width that remains approximately constant as the vehicle 100 transitions from horizontal to vertical movement. In this way, the vertical drive mechanism 140 does not have to freely telescope outward to transition from horizontal to vertical drive. For example, referring to Figures 2-3, the front lift vertical drive gears 145b and 145d each have a horizontal rotation axis, and while the vehicle 100 is moving horizontally and while the vehicle 100 is ascending, the spacing between the horizontal rotation axes of the vertical drive gears 145b is fixed relative to the horizontal rotation axis of the vertical drive gears 145d.

[0061] The vehicle 100 may then include an optional transfer mechanism for moving items between the vehicle 100 and a destination, such as a storage location 820 .

[0062] For example, the loading and unloading mechanism 150 may be operable to move items between a platform surface of the vehicle 100 and one of a number of destination areas 820 . As shown in FIG. 2, the platform surface is defined by the outer surfaces of a number of rollers.

[0063] The transfer mechanism 150 may then be any of a variety of mechanisms for loading items onto the vehicle 100 and unloading items from the vehicle 100 into one of the storage areas 820 . Additionally, the loading and unloading mechanism 150 may be specifically tailored to a particular application. The loading and unloading mechanism 150 includes one or more displaceable members configured to engage items stored in the storage locations 820 and load the items onto the vehicle 100 . More specifically, vehicle 100 includes one or more displaceable members configured to move toward and releasably engage tote 55 at storage location 820 . Then, after the displaceable members engage the tote 55 , each displaceable member is displaced away from the storage location 820 , thereby loading the tote 55 onto the vehicle 100 .

[0064] And, the displaceable member of the loading / unloading mechanism 150 may be any of a variety of items, such as a bar, rod, or other member configured to engage an item, such as a tote 55, for example. For example, with reference to FIGS. 2-3, the loading mechanism 150 may include one or more displaceable pins 152 . Furthermore, the loading / unloading mechanism 150 may include a drive member that displaces the pin 152 . For example, the loading and unloading mechanism 150 includes two drive members in the form of an endless conveyor such as a drive belt or drive chain 154 as shown. Each pin 152 projects or extends inwardly toward the longitudinal centerline of the vehicle 100 . The loading and unloading mechanism 150 is preferably configured to be associated with one of the totes 55 and to removably engage the tote 55 . For example, pin 152 is configured to connect with a recess on tote 55 so that loading mechanism 150 can engage tote 55 . However, it should be appreciated that the loading and unloading mechanism 150 may include any of a variety of members for moving and engaging items to be loaded onto and unloaded from the vehicle 100 .

[0065] The vehicle 100 includes one or more drive members for driving the loading / unloading mechanism 150 . The vehicle 100 includes one or more motors that drive the loading / unloading mechanism 150 . For example, one or more motors in the vehicle drive system may drive the drive chain 154 to move the drive chain 154 and pin 152 towards or from the storage location 820 .

[0066] Then, as the vehicle 100 approaches the storage location 820 to retrieve the tote 55, the drive chain 154 may drive the displaceable pin 152 toward the storage location 820 so that the pin 152 is under a groove or notch in the bottom surface of the tote 55. The vehicle 100 moves upward a short distance until the pin 152 is located in the groove or notch. The drive chain 154 then reverses until the pin 152 clears the storage location 820 . As the pin 152 moves away from the storage location 820 , the pin 152 engages the tote 55 within the notch, thereby placing the tote 55 on the surface of the vehicle 100 . In this manner, the loading and unloading mechanism 150 is operable to retrieve items from the storage location 820 . Similarly, to store an item in a storage location, such as storage location 820, drive chain 154 of loading / unloading mechanism 150 drives pin 152 toward storage location 820 until the item is located at storage location 820. The vehicle 100 then moves downward to disengage the pin 152 from the tote 55, thereby releasing the tote 55.

[0067] As seen in FIG. 7, two or more totes, such as tote 55, may each be connected and separated from one another using a mating connector. The totes 55 may then be connected and separated from one another through a series of lifting and separating actions performed by the movement of the vehicle 100 . The loading mechanism 150 may operate to load the forward-facing (“leading”) tote 55 onto the surface of the vehicle 100 so that it is fully supported by the vehicle 100 . If the totes 55 are detachably connected, this loading action will cause the facing totes 55 (ie, those immediately following the lead tote 55) to move to a location facing the aisle. The vertical drive mechanism 140 of the vehicle 100 is then actuated to cause the vehicle 100 to travel a vertical distance sufficient to separate the leading tote 55 from the trailing tote 55 . Once separation is complete, the drive system is reactivated, placing the lead tote 55 at the center of the vehicle 100 .

[0068] The vehicle 100 may also include a separate drive member for driving the loading / unloading mechanism 150 . Alternatively, the loading and unloading mechanism 150 may be interconnected with one of the horizontal or drive members of the vehicle 100 . Specifically, the loading and unloading mechanism 150 may be connected to one of the drive systems such that the drive system is operable between driving the vehicle 100 and driving the loading and unloading mechanism 150 .

[0069] For example, the loading and unloading mechanism 150 may be connected to one of the horizontal drive mechanisms having a selectable connection such that in a first orientation the drive system drives the vehicle 100 horizontally and in a second orientation the drive system drives the loading and unloading mechanism 150. An optional clutch mechanism can be engaged and disengaged to respectively start and end the transmission of power from the motor of the horizontal drive mechanism to the transfer mechanism 150, thereby allowing the second drive system to operate independently of the transfer mechanism 150. In this example, the clutch mechanism may be configured as two clutch assemblies positioned symmetrically about the longitudinal centerline of the vehicle 100.

[0070] Vehicle 100 may be semi-autonomous or alternatively fully autonomous. Regarding the latter point, a number of non-contact systems have been proposed for the purpose of continuously determining the actual position of the automated guided vehicle 100 in absolute coordinates and initializing the navigation parameters (e.g., X, Y, and heading) to null out any accumulated errors, thereby re-referencing the vehicle. Any of these may be utilized to implement location referencing for automated guided vehicles 100 in an inventory management system consistent with embodiments of the present disclosure. Such referencing systems can be ultrasonic, radio frequency (RF) or optical in nature, with ultrasonic and optical being particularly suitable for indoor situations. In these latter two categories, optical systems are generally more accurate and are more widely adopted in commercial practice.

[0071] The location detection system utilizes a scanning mechanism that operates in conjunction with fixed locations placed in a predetermined, measured field. Such scanning mechanisms may include scanning detectors with fixed active beacon emitters, scanning emitter / detectors with passive retroreflective targets, scanning emitter / detectors with active transponder targets, and rotating emitters with fixed detector targets.

[0072] The vehicle 100 may then provide position updates to its on-board autonomous navigation system via a scanning laser triangulation scheme (SLTS). For example, a laser emitter rotating at 2 revolutions per minute illuminates a passive retroreflective barcode target affixed to a wall or post at a known location approximately 15 meters from the vehicle 100 . This bar code is used to positively identify the reference target and eliminate ambiguity due to spurious returns from other reflective surfaces within the field of operation. The on-board computer of each vehicle 100 calculates the XY position updates by simple triangulation and nulls the accumulated error.

[0073] Alternatively, each vehicle 100 may utilize retroreflective targets distributed throughout the operating area in a manner that allows each vehicle 100 to determine both range and angular orientation. For example, a servo-controlled rotating mirror on the vehicle 100 may sweep the near-infrared laser beam through a 90 degree horizontal arc at an update rate of, for example, 20 Hz. As the laser beam sweeps across a target of known size, a return signal of finite duration is sensed by the detector. If the retroreflective targets are all the same size, the signal produced by a closer target will have a longer duration than that from a more distant target. Angle measurements begin as the scanner begins to pan from the right to the left where detection of a reflected signal ends the timing sequence.

[0074] Yet another location referencing technology that may be employed by the vehicle 100 is a laser-based scanning beacon system that uses cooperative electronic transponders with reflectors to calculate vehicle position and heading. Such a scanning mechanism includes a rotating mirror mounted at an angle of, for example, 45 degrees to the vertical axis of the incremental optical encoder. To improve azimuth accuracy, a timer interpolates between encoder counts. The fan-shaped laser beam diverges vertically at a 4 degree spread angle to ensure long-range target detection while traversing uneven floor surfaces. Each target is uniquely coded and many (eg, 32) targets can be processed in a single scan, with the XY position of the vehicle 100 being calculated every 100 milliseconds.

[0075] Each vehicle 100 may also maintain in memory a built-in map of its location within the facility. Additionally, each vehicle 100 provides signals to the central controller 450 containing data such as position on the driving plane, speed, angular orientation, and selected route of driving data to other vehicles within the facility. Vehicles 100 may include receivers so that they can receive such data regarding other vehicles 100 . Vehicles 100 may receive such data regarding other vehicles 100 either directly from the other vehicles 100 or from central controller 450 . Using the vehicle data, each vehicle 100 maintains a dynamically updated map that reflects the location of all vehicles 100 in the particular area within the inventory control facility to which that vehicle 100 is assigned. When dynamically updated location data is made available locally to each vehicle 100, tasks may be assigned to the vehicles 100 by the central controller 450, and route sections to be traversed by the vehicles 100 to reach locations where components of the assigned tasks are to be performed may be selected by the vehicles 100.

[0076] Each vehicle 100 may include a processor configured to execute a number of steps of a navigation process stored in memory, the steps directing the vehicle 100 along the shortest path from the current location of the vehicle 100 to a destination where the next subtask of the assigned task is to be performed. Although the central controller 450 need not be configured to perform traffic control and collision avoidance functions (unless a backup control scheme is desired), this central controller 450 may be configured to transmit signals representing instructions identifying the next tasks to be assigned to each vehicle 100 and specifying various locations within the facility where those tasks are to be performed. Alternatively, vehicle 100 may be configured to send signals to central controller 450 representing task assignment acknowledgements, location updates, status updates (e.g., completed or ongoing subtasks, current power status, etc.), and other information required by central controller 450 to assess the relative capabilities of vehicle 100 to perform tasks awaiting assignment.

[0077] In a fully autonomous manner, each vehicle 100 may utilize a local processor to sense indicia attached to underlying support surfaces in one or more areas of the inventory control facility to determine speed and direction of movement, exchange its location data with other vehicles 100 in the facility, and maintain dynamically updated local maps to implement a form of distributed traffic control in a manner similar to that described above using other location detection techniques.

[0078] In semi-autonomous configurations of vehicles 100, also known as automated guided vehicles (AGVs), a central controller such as controller 450 provides traffic control functions needed to, for example, prevent collisions between vehicles 100 and / or with any potential obstacles to the movement of vehicles 100 that may exist in one or more areas of the facility to which some of vehicles 100 are assigned. Such a central controller 450 receives current position and heading data in the form of update signals transmitted from the vehicles 100 . The received position and heading data is compared to estimates derived by the central controller 450 from previous speed and heading commands communicated by the central controller 450 to the vehicle 100 . Based on this comparison, the central controller 450 determines corrections to one or more of the speeds and directions of one or more of the vehicles 100 that are required to prevent a collision, and, if so, communicates these instructions to the vehicles 100.

[0079] In one or more semi-autonomous embodiments, each vehicle 100 may include a reader that reads indicia attached to the underlying support surface on which the vehicle 100 travels and / or located in an access queue aligned with the arrangement of storage areas 820 (see FIG. 1 ). Each indicia of the first group of indicia corresponds to a unique location forming a grid position. These locations may be stored in a data table in memory accessible to the processor in vehicle 100, the processor in central controller 450, or both processors. By traveling along a path designed to intersect with a particular arrangement of these indicia, each vehicle 100 may pass the indicia and, upon verifying the indicia, transmit the indicia's identifier to the central controller 450, as soon as semi-autonomous guidance of the vehicle 100 is achieved by commands transmitted to the vehicle 100 by the central controller 450. From this information and other data conveyed by each vehicle 100, the central controller 450 is able to ascertain the speed, direction and route of travel of each vehicle 100. This central controller 450 uses speed and direction data to implement collision avoidance strategies, assign inventory management tasks to each vehicle 100 according to its location and power reserve status, and maintain an appropriate distance from any authorized personnel in the area for safety reasons.

[0080] Additional indicia may be affixed adjacent to each storage location 820, in the access queue, or on the stored tote 55 itself. Here, each indicia may have or include a unique barcode, and a reader on each vehicle 100 may scan the area around the storage location 820 where the item is to be delivered or retrieved. The data held by the central processor 450 regarding the route the vehicle 100 must take and the distance traveled by the vehicle 100 based on data regarding the rotation of the first drive motor 230 may then be sufficient to determine whether the vehicle 100 should be placed in an appropriate storage location 820 within the storage area. Even in such cases, indicia adjacent to the storage area permit redundant checking of the location of the vehicle 100 before items are dropped off at or retrieved from the appropriate storage location 820 . Thus, the scanner may be operated to scan and read information regarding the storage location 820 at which the vehicle 100 is parked. If the scanned data indicates that storage location 820 is an appropriate storage location, vehicle 100 drops off the item at storage location 820 . Similarly, the vehicle 100 may have a second reader that reads indicia adjacent the rear end of the vehicle 100 . This second reader may be used in applications where the system is configured to utilize a series of first storage locations along the front of the access queue and a series of second storage locations along the back of the access queue, as shown in Figure 1.

[0081] The functionality for autonomous or semi-autonomous guidance of the vehicle 100 may then be incorporated into the functional accessory, the movable rack 700. Such an approach may be useful where accurate location detection is required in some areas of an inventory control facility, but a less accurate location technique may be acceptable in other areas. For example, in FIG. 1, functional accessory, namely, movable rack 700, is shown as playing a supporting role in maintaining the necessary supply of items to operators in work station 500.

[0082] In the above description, vehicle 100 has vertical drive mechanism 140 that is sized and positioned to interact with track 840 located adjacent storage area 820 of storage rack 800. The vertical drive gear 145 of the vertical drive mechanism 140 raises or lowers the vehicle 100 depending on the direction of rotation of the first drive motor 230. Additionally, the functional accessory movable rack 700 may incorporate a track 840 that interfaces with the vertical drive mechanism 140 to allow the vehicle 100 to raise and lower the associated functional accessory 700.

[0083] The central processor in each vehicle 100 controls the operation of the vehicle 100 in response to signals received from central processor 450 . Additionally, vehicle 100 includes a wireless transceiver so that it can continuously communicate with central processor 450 as it travels along track 840 . In some applications, it may be desirable to incorporate multiple sensors or signs along the route that the vehicle 100 may travel. The vehicle 100 may include a reader that senses the sensor signals and / or indicators, as well as a central processor 450 that controls the operation of the vehicle 100 in response to the sensors or indicators.

[0084] As shown in FIG. 1, material handling system 10 may include many different work stations or areas. For example, material handling system 10 may include multiple storage locations 820 arranged on multiple storage racks 800 . The storage rack 800 may then contain thousands or tens of thousands of storage locations 820 . <Autonomous storage>

[0085] 1 and 6, the material handling system 10 may include a plurality of storage racks 800 that may be arranged to form rows or aisles 850. For example, a first storage rack 800a may be spaced apart from a second storage rack 800b such that an aisle 850a is formed between the two storage racks 800. In particular, the first storage rack 800a may form an aisle 850 with the second storage rack 800b that is generally parallel and has a generally uniform width. Additionally, material handling system 10 may include multiple storage racks 800 forming multiple aisles 850 . And, although the aisles 850 are shown as parallel in FIG. 6, if the material handling system 10 incorporates multiple storage racks 800, the storage racks 800 may be arranged in a variety of configurations, and if the material handling system 10 includes multiple aisles 850, the aisles 850 need not be parallel. One of the inventory control tasks assigned to vehicle 100 may be to retrieve items from storage location 820 . This inventory management task can be viewed as a series of subtasks, including leaving the current or starting location of the vehicle 100, traversing a route that carries the vehicle 100 between the starting location and an intermediate destination adjacent to an entry point into the array of storage locations 820, and aligning the vehicle 100 at the entry point at the intermediate destination. As a further subtask of the retrieval task, the aligned vehicle 100 enters the array of storage locations 820 and maintains its alignment until it reaches the row in which the vehicle 100 is aligned, and according to yet another subtask, is actuated to ascend until it reaches the target area of ​​the storage area 820. As a further subtask of the retrieve task, the loading and unloading mechanism 150 of the vehicle 100 is operated to retrieve the item, move down the vertical row 810 until the vehicle 100 rests on a lower support surface, and then exit the array of storage locations 820. As a final subtask of the recovery task, the vehicle 100 proceeds along route 860 to a work site 500 where an operator can recover the item from the vehicle 100 .

[0086] And, the material handling system 10 includes automated components for storing and retrieving totes 55 from storage locations 820 . Such an autonomous component is an autonomous vehicle 100. For example, the automated component may include multiple autonomous vehicles 100. Additionally, the autonomous vehicle 100 may be configured to transport the tote 55 to the work site 500 . At work station 500, one or more items may be removed from a tote 55 on one of the vehicles 100. A human operator may remove the item from the vehicle 100. However, an automated mechanism may also remove items from the vehicle 100 . Thus, the operators handling the items at work station 500 may be human operators or automated mechanisms or a combination of the two.

[0087] The material handling system 10 and / or various components of the material handling system 10 may then be controlled by a central controller 450, such as a microcomputer. This central controller 450 may then receive signals from various components, such as sensors, and control various aspects of the material handling system 10 based on the signals received from the various components. This central controller 450 may store data regarding the location of various items retrieved from the material handling system 10 . Additionally, central controller 450 may include data regarding the identity of the items received, such as the number of items fulfilling the customer's order and the quantity of those items. In this manner, central controller 450 may control and coordinate the operation of various components and schedule the retrieval and processing of various items from storage location 820 .

[0088] FIG. 6 is a partial perspective view of a portion of an inventory control system that forms part of the material handling system 10 shown in FIG. 1 and utilizes autonomous vehicles 100 to move containers 55 of inventory items back and forth between a pickup area and a vertical array of storage locations 820. The inventory control system may incorporate an array of vehicles 100 and storage locations 820 as part of an automated storage / retrieval system (AS / RS). The vehicle 100 may be configured in the manner of the vehicle 100 described above. However, this vehicle 100 may have modifications for other tasks within a material handling system.

[0089] 1 and 6-10, a material handling system for storing and retrieving items within an array of storage locations 820 will now be described. Referring initially to FIGS. 1 and 6, a plurality of automatically transported vehicles 100a-100f are shown operating within or around a storage rack 800. As shown in FIG. As in the previous embodiments, vehicles 100a-100f perform various item replenishment and / or item retrieval tasks, some of which in this example involve retrieving containers 55 from storage locations 820 or returning containers (or totes) 55 to storage locations 820.

[0090] As mentioned above, the material handling system 10 may include multiple storage racks 800 spaced apart to form one or more aisles 850 . And, the tracks 840 may be arranged along one or more storage racks 800 . For example, the track 840 may be fixedly connected to the storage rack 800 . Additionally, the track 840 may be configured to guide the vehicle 100 vertically so that the vehicle 100 can be transported up and down the vertical row 810 to a storage location 820 within the vertical row 810. Additionally, it may be desirable to position the first track 840a along the storage racks 800 on one side of the aisle 850, such as along the first storage rack 800a, and the second track 840b along the storage racks 800 on the opposite side of the aisle 850, such as along the second storage rack 800b. Vehicle 100 may be configured such that one side of vehicle 100 moves vertically along track 840 of first storage rack 800a while vehicle 100 travels along moving aisle 850a, and simultaneously, a second side of vehicle 100 moves vertically along track 840 of second storage rack 800b.

[0091] Each vertical column 810 may be formed by a plurality of vertical posts 815 . As shown in Figures 7-10, the vertical columns may be arranged such that multiple vertical columns 815 are aligned in parallel relationship on one side of the vertical column 810 and multiple vertical columns 815 are aligned in parallel relationship on a second side of the vertical column 810 opposite the vertical columns 815 on the first side. As shown in FIG. 7, the vertical posts 815 on each side may be interconnected by a plurality of horizontal support members 817 that extend the depth of the vertical column 810 .

[0092] This horizontal support member 817 may be a separate member that provides structural support to the vertical columns 810 . This horizontal support member 817 may also support items stored in storage locations 820 . For example, horizontal support member 817 may be a planar member that forms a shelf such that the shelf forms storage location 820 . However, the horizontal support member 817 may be in any of a variety of configurations. For example, in FIG. 8, the horizontal support member 817 is an L-shaped bracket 817 that forms a long horizontal shelf and supports the edge of the tote 55 across the depth of the storage location 820. The horizontal support members 817 may then be spaced apart from one another up to the height of the vertical columns 815 to form vertical rows 810 of horizontally spaced apart storage locations 820 .

[0093] 7. And, the vertical row 810 of storage racks 800 has a depth similar to the length of the horizontal support members 817 as viewed in FIG. Additionally, vertical column 810 has a depth that is similar to or greater than the length of tote 55 . For example, vertical column 810 may have a depth sufficient to accommodate at least one tote 55 . However, the totes 55 may overhang the aisles 850, resulting in the vertical rows 810 having a depth slightly less than the length of the totes 55. As shown in FIG. 7, vertical column 810 may be deep enough to accommodate multiple totes 55 arranged end-to-end. In FIG. 7, the storage rack 800 is deep enough so that each storage location 820 can accommodate three totes 55 aligned end to end, with each tote 55 approximately the length of the vehicle 100.

[0094] As mentioned above, the vehicle 100 has a length and a width. As shown in FIG. 5, the vehicle 100 has a length "L" that is significantly longer than its width "W2". 6-10, storage rack 800 is configured so that each vertical column 810 has a width that is significantly less than its depth. Specifically, the width of each vertical column 810 is similar to the width of the vehicle 100 , and the depth of the vertical columns 810 is significantly greater than the width of the vehicle 100 . As shown in FIGS. 7 and 10, the vertical columns 810 have a depth that is more than twice the width of the vehicle 100. Additionally, the depth of the vertical column 810 may be greater than the length of the vehicle 100 .

[0095] FIG. 7 shows multiple vehicles 100 at different orientations relative to a storage rack 800 and storage location 820. For example, the first vehicle 100 a is oriented for horizontal movement along a path 860 c that traverses the length of the passageway 850 . A second vehicle 100 b,c is oriented for horizontal movement below the storage rack 800 along a path 860 b, 860 b ′ parallel to the length of the aisle 850 . Additionally, a third vehicle 100d is positioned within aisle 850 and travels up a vertical track along storage racks 800 on either side of aisle 850. A fourth vehicle 100e is also positioned in the aisle 850 and travels up the tracks 840a,b to the storage location 820 at the top of the vertical column 810. Finally, the fifth vehicle 100f is positioned below the storage rack 800 and is oriented in a position midway between the direction of vehicles 100a and 100b. In particular, the storage rack 800 may be configured to facilitate horizontal rotation of the vehicle 100 underneath the storage rack 800 . The fifth vehicle 100f shows the vehicle 100 in the process of rotating under the storage rack 800 from the first path to the second path.

[0096] As mentioned above, the storage racks 800 are sized and positioned to allow vehicles 100 to enter and exit at various locations below the storage locations 820, allowing flexibility in the location of collection and / or replenishment stations. Where the material handling system 10 utilizes one or more storage racks 800 and one or more storage racks 800, the storage racks 800 may be configured such that the vehicle 100 can travel under the storage racks 800 as well as through or along one or more aisles 850 that may be incorporated into the material handling system 10. For example, with reference to FIG. 6, vehicle 100 may follow a path 860 that travels along one or more path segments that may be parallel to or cross path 850 . A first such path is represented by path 860a. The first path 860a is within and parallel to the length of the passageway 850a. Such a second path is represented by path 860b, which is parallel to the length of passage 850a but spaced apart from it. Specifically, the second path 860b is located below the second storage rack 800b. The second storage rack 800b may be configured to provide clearance for movement of the vehicle 100 below the lowest storage location 820 so that the vehicle 100 can pass under the storage rack 800b along a path 860b parallel to the length of the aisle 850a. The third path is represented by path 860c, which traverses paths 860a and 860b. As shown in FIG. 6, path 860c is parallel to the depth of vertical column 810.

[0097] 7 and 9, the storage racks 800 are configured such that the vertical rows 810 of the storage racks 800 have a depth sufficient to provide multiple paths 860 under each vertical row 810 generally parallel to the length of the aisles 850. Specifically, as shown in FIG. 7 , vertical pillars 815 adjacent to aisle 850 may be spaced apart from vertical pillars 815 away from aisle 850 to form openings having widths greater than twice the width of vehicle 100.

[0098] FIG. 9 shows a second vehicle 100b traveling along a path 860b parallel to the passageway 850, and a third vehicle 100c traveling along a path 860b' parallel to the path 860b. Preferably, the path 860b' has a centerline that is spaced more than half the length "L" of the vehicle 100 from the vertical post 815 adjacent the aisle 850 (see FIG. 5). Similarly, preferably, path 860b has a centerline that is spaced from the rearmost vertical post 815 of vertical column 810 away from aisle 850 by a distance greater than half the length of vehicle 100.

[0099] And, the paths 860b, 860b' under the storage rack 800 parallel to the aisle 850 may be spaced apart to provide a gap that allows a vehicle 100b traveling along path 860b to pass a vehicle 100c arranged along path 860b', such as a vehicle traveling in the opposite direction along path 860b'. For example, path 860b may be separated from path 860b' by a distance greater than width "W2" of vehicle 100 (see FIG. 5).

[0100] Additionally, as discussed above, the vehicle 100 may change direction by rotating about a vertical axis of rotation that passes through the vehicle 100 . In particular, the vertical axis of rotation may pass through the center of the vehicle 100. Vertical row 810 desirably has a depth sufficient to facilitate rotation of vehicle 100 about a vertical axis of rotation while vehicle 100 is arranged in vertical row 810 under storage rack 800 . Specifically, each of the paths 860b, 860b' is desirably spaced from the vertical post 815 by a distance that exceeds the distance from the vertical axis of rotation to each of the corners of the vehicle 100.

[0101] As the vehicle 100 rotates under the storage rack 800, the vehicle 100 may rotate to any of a variety of angles. The vehicle 100 may rotate in 90 degree increments. In particular, after the vehicle 100 ascends the track 840 within the aisle 850, the vehicle 100 rotates either 90 degrees or 270 degrees after exiting the aisle 850 so that the vehicle 100 travels parallel to the aisle 850 under the storage rack 800.

[0102] FIG. 8 is a side view of a storage rack 800 including multiple vertical rows 810a-810f loaded with multiple containers or totes including totes Ta, Tb, Tc, and Td. A plurality of vehicles 100 operate as part of an inventory management system to perform various item replenishment and / or item retrieval tasks. Here, vehicle 100a is shown entering the leftmost vertical drive train 810a. Referring to FIG. 9, a storage rack 800 may incorporate an arrangement of parallel guide rails, such as rails R1 and R2, that define a gap gG between the rails. The gap is sized and positioned to receive corresponding alignment structures of the vehicles 100 to allow the vehicles 100 to enter, exit, and reorient without damaging each other and, as discussed further below, the storage racks 800.

[0103] The material handling system 10 may include one or more guides 880 that guide or align the vehicle 100 as it travels. For example, with reference to FIG. 9, guide 880 may include a route or groove, and vehicle 100 may include a corresponding guide member 126 that cooperates with guide 880 to control movement of vehicle 100. An example of the guide member 126 is a follower 126 . The follower 126 may be any member configured to engage or cooperate with the guide 880 . The vehicle 100 includes a central follower 126 that includes a rotating member, such as a bearing, that rotates about a vertical axis. The central follower 126 includes a shaft such that the follower 126 projects away from the surface of the vehicle 100, such as downward from the underside of the vehicle 100. This central follower 126 then engages with the route within the guide 880 to restrain the horizontal movement of the vehicle 100 .

[0104] The vehicle 100 may include one or more side guide members 127 . The side guide member 127 may cooperate with the outer surface of the guide 880 to restrict movement of the vehicle 100 . For example, guide 880 may include a circular guide having a periphery for guiding the rotation of vehicle 100 . The vehicle 100 may have a pair of side guide members 127 spaced apart by a distance equal to the diameter of the periphery of the guide 880 . In this way, the side guide member 127 engages with the circumferential surface of the guide 880 and prevents the vehicle 100 from moving in a rotational manner.

[0105] Referring to FIG. 9, guide 880 includes multiple intersecting guideways. For example, the guide 880 may include a first guideway 882 in the form of a groove or route having walls spaced apart a distance substantially similar to the width of the center follower 126 of the vehicle 100 . The first guideway 882 may be oriented to extend parallel to the pathway 860 . Additionally, the guide 880 may include a second guideway 884 in the form of a groove or route having walls spaced apart a distance substantially similar to the width of the follower 126 of the vehicle 100 . The second guideway 884 may be oriented to extend across the pathway 860 . In this example, the second guideway 884 extends substantially perpendicular to the path 860 . Thus, the first guideway 882 and the second guideway 884 of the guide 880 preferably extend in a linear direction parallel to or perpendicular to the passageway 850 .

[0106] And, guide 880 includes a guide path that is not linear. For example, the periphery of guide 880 may form a non-linear guide surface identified at 886 in FIG. Specifically, the guide 880 may have a generally circular profile that defines an annular bearing surface. The diameter of the circular outer shape may have a diameter corresponding to the distance between the side guide members 127 of the vehicle 100 (see FIG. 3).

[0107] Additionally, the guideways of guide 880 intersect to facilitate vehicle 100 turning. For example, first guideway 882 may intersect with second guideway 884 to facilitate vehicle 100 changing direction from parallel to aisle 850 to perpendicular to aisle 850 or vice versa. The first guideway 882 and the second guideway 884 may then intersect at the center point of the guide 880 . In this manner, guide 880 facilitates rotation of vehicle 100 around a vertical axis, rotating vehicle 100 from a direction of travel along first guideway 882 to a second direction of travel along second guideway 884.

[0108] Guidance 880 may guide and turn vehicle 100 as follows: The vehicle 100 may then travel along the linear path with the central follower 126 engaging the first guideway 882 or the second guideway 884 to prevent lateral displacement away from the linear path. With the side guide members 127 of the vehicle 100 engaged in the circular guideway 886 , the vehicle 100 travels horizontally along the linear path until the center follower 126 is positioned at the center point of the guide 880 . The vehicle 100 rotates about a vertical axis to change direction. For example, the drive wheels 124 on one side of the vehicle 100 may rotate in a first direction, and the drive wheels 124 on the opposite side of the vehicle 100 may rotate in a second direction opposite to the first direction to perform a zero-radius turn. While the drive wheels 124 rotate the vehicle 100 about the rotation axis, the side guide members 127 prevent the vehicle 100 from displacing laterally off the rotation path.

[0109] The guide 880 is then aligned with the vertical column 810 while adjusting the width of the vehicle 100 to fit into the opening between the vertical pillars 815 in front of the vertical column 810 (adjacent to the aisle 850) or behind the vertical column 810 (away from the aisle 850), thereby facilitating the rotation of the vehicle 100 within the vertical column 810.

[0110] As shown in FIG. 9, the material handling system 10 may include a floor-mounted side alignment system 890 that comprises a pair of plate-like members spaced apart by a gap gG. The gaps defined by lateral alignment system 890 are oriented to match the gaps defined by alignment system 895 so that vehicle 100 can quickly and easily traverse the entire width of the structure while maintaining a generally constant rotation angle within drive trains D1-D6.

[0111] As mentioned above, a plurality of guide members, such as track members 840, are attached to the storage rack 800 to guide and align the vehicles 100 with the storage locations 820 located above the floor surface. For example, track 840 may include multiple vertical track segments. Specifically, a vertical track section may be attached to each vertical post 815 within the passageway 850 . Referring to FIG. 10, the vertical track section may be configured to engage the vertical drive mechanism 140 of the vehicle 100 . For example, the track 840 may have a plurality of teeth that form a storage rack 800 that extends the height of the vertical post 815 .

[0112] As shown in FIG. 7, the tracks 840 may span the passageway 850 such that a first track 840a extends vertically upward along a first side of the vertical column 810 and a second track 840b extends upward along a second side of the vertical column 810. For example, the pillar D1 and vehicle 100e of FIG. 7 are shown in FIG. Pillar D1 has two spaced apart vertical pillars 815 that form an opening having a width. Specifically, the first pillar has a first vertical end E1 and a second vertical end E2, and the second pillar has a first vertical end E3 and a second vertical end E4. The distance between the second vertical end E2 and the first vertical end E3 exceeds the width W1 of the vehicle 100 (see FIG. 5). The distance between the second vertical end E2 and the first vertical end E3 is less than the width W2 of the vehicle 100 (see FIG. 5). In this manner, the width of the vertical column 810 may be less than the distance between the outer vertices of the vertical drive gears 145 of the vertical drive mechanism 140 of the vehicle 100 . Thus, most of the vertical columns 810 may be narrower than the widest portion of the vehicle 100 .

[0113] The track 840 may be configured such that a first vertical end E1 of the track 840 protrudes toward a first vertical column to provide a guide surface for the first vertical column, and a second vertical end E2 of the track 840 protrudes toward a second vertical column to provide a guide surface for an adjacent vertical column. For example, track 840 may provide a first set of teeth projecting toward drive train D1 and a second set of teeth projecting toward drive train D2.

[0114] Additionally, vertical posts 815 may be configured to provide stopping positions that prevent lateral displacement of vehicle 100 as vehicle 100 ascends track 840 . For example, referring to FIG. 10, the vertical post 815 overlaps the teeth of the track 840 such that the first vertical end E3 of the vertical post 815 extends beyond the base of the teeth of the track 840 and preferably toward the top of the track 840. In this manner, the teeth of vertical track mechanism 140 mesh with track 840 while vertical post 815 prevents vertical drive mechanism 140 from displacing laterally parallel to the depth of vertical column 810 .

[0115] The vertical drive mechanism 140 of the vehicle 100 may be configured so that the vertical drive gears 145 can be displaced inward to reduce the distance between the vertical drive gears 145 . In this manner, the vertical drive gear 145 can move inward to provide spacing between the track 840 and the vertical drive gear 145 as the vehicle 100 enters the vertical row 810 . As mentioned above, the vertical drive gears 145 may be mounted on a drive shaft such that the axis of rotation of each vertical drive gear 145 is approximately parallel to the horizontal direction of travel. Additionally, the axes of rotation of the vertical drive gears 145 may be substantially constant so that the lateral distance between each set of vertical drive gears 145 is substantially constant. The teeth of vertical drive gear 145 are aligned with the teeth of track 840 so that the teeth of vertical drive gear 145 pass through the teeth of track 840 to enter vertical post 815 .

[0116] Referring to FIG. 10, the track 840 and the vertical drive gear 145 may be aligned so that the vertical drive gear 145 does not collide with or contact the track 840 when moved relative to the track 840 . For example, the spacing between the teeth of this track 840 provides sufficient spacing for the teeth of the vertical drive gear 145 to pass through the gaps between the teeth of the track 840 when the vertical drive gear 145 moves horizontally along a line parallel to the axis of rotation of the vertical drive gear 145. More specifically, vertical drive gear 145 and track 840 may be configured and arranged such that the addendum circle of vertical drive gear 145 overlaps with the addendum line of the teeth of track 840. The teeth of the vertical drive gear 145 are configured and oriented to pass through the gaps between the teeth in the track 840 while the addendum circle of the vertical drive gear 145 overlaps with the addendum line of the track 840.

[0117] Referring to FIG. 10, the vertical drive gear 145 and track 840 may be configured and oriented to increase the spacing so that the vertical drive gear 145 passes through the track 840 when the vehicle 100 enters the opening between the vertical posts 815 that form the width of the vertical column 810 (i.e., when the vertical drive gear 145 moves so that the axis of rotation of the vertical drive gear 145 moves in a horizontal direction perpendicular to the passageway 850). For example, the track 840 may have an upper and lower portion 842 . This upper portion may then have a tooth pitch and configuration that mates with the teeth of the vertical drive gear 145 . The lower portion 842 may have a tooth pitch that is approximately the same as the tooth pitch of the upper portion, but the tooth profile of the lower portion 842 may be significantly different from that of the upper portion. For example, the teeth on the lower portion 842 may be significantly narrower than the teeth on the upper portion. For example, the teeth of the lower portion 842 may be at least 10% narrower, and preferably 20% narrower. Additionally, the teeth on the lower portion 842 may have a dedendum that is significantly greater than the dedendum on the upper portion. For example, the dedendum of the lower portion 842 may be greater than the dedendum of the upper portion such that the root of the tooth extends inward away from the vertical drive gear 145 a greater distance than the root of the upper portion. For example, the root depth of the lower portion 842 may be 10% greater, and preferably 20% greater.

[0118] Additionally, the lower portion 842 may have a tapered pitch line such that the spacing between adjacent teeth becomes increasingly smaller as the teeth progress up the height of the lower portion 842. In other words, the spacing 845 between adjacent teeth below the lower portion 842 is greatest, the spacing 728 between adjacent teeth above the lower portion 842 is least, and the spacing gets progressively smaller from greatest to least.

[0119] And, the vertical posts 815 have a variable width that facilitates passage of the vertical drive gear 145 through the openings between the vertical posts 815 . For example, as described above, the vertical post 815 may have a first width such that a first vertical end E3 of the vertical post 815 extends beyond the roots of the teeth of the track 840. Additionally, the lower portions 816 a , 816 b of the vertical post 815 may have a narrowed width relative to the upper portion of the vertical post 815 . Specifically, the vertical post 815 may have a narrowed width such that the end of the vertical post 815 terminates below the root of the tooth. Thus, the lower portions 816 a , 816 b of the vertical post 815 have a narrower width than the upper portion of the vertical post 815 . Similarly, the distance between the lower vertical post 816a and the lower vertical post 816b exceeds the distance between the second vertical end E2 and the first vertical end E3. Furthermore, the opening of vertical column 810 between lower portions 816a and 816b of vertical pillar 815 exceeds the widest width W2 of vehicle 100.

[0120] Configured as described above, vertical drive mechanism 140 may be configured to pass through an opening in track 840 such that vertical drive mechanism 140 is aligned with track 840 . As further described above, after the vertical drive mechanism 140 is aligned with the track 840, the vertical drive mechanism 140 is positioned to cooperate with the track 840 to lift or / and ascend the track 840.

[0121] As mentioned above, the central controller 450 may provide control signals that control the vehicle 100 . For example, central controller 450 may control the movement of vehicle 100 through storage rack 800 following path 860 to retrieve tote 55 from storage location 820 in one of vertical columns 810 within storage rack 800 . The vehicle 100 may follow a path 860 along the ground, aligning the width of the vehicle 100 with the path 860 extending through an opening between two vertical posts 815 of the storage rack 800 . Vehicle 100 may travel along a path 860 that traverses through multiple vertical rows 810 within storage rack 800 . The central controller 450 may then provide a signal to control vehicle 100c to travel along a second path parallel to the first path and to pass vehicle 100b under the same storage rack 800 as vehicle 100b.

[0122] After the vehicle 100 passes through a number of vertical rows 810 under the storage rack 800, the vehicle 100 reaches the vertical row 810 within the storage rack 800 where the selected storage location 820 is located. The central controller 450 then provides a signal to stop the vehicle 100 from moving forward along the path 860 . This central controller 450 provides signals to rotate the vehicles 100 under the storage racks 800 and align the vehicles 100 with the openings in the vertical rows 810 . After turning, the vehicle 100 moves forward along a path 860 parallel to the depth of the vertical column 810 so as to enter the aisle 850 through an opening in the vertical column 810 . Advancing vehicle 100 into aisle 850 includes aligning vertical drive members with gaps of openings in vertical column 810 . Then, once in aisle 850 , vehicle 100 drives vertically upward until vehicle 100 is aligned with the desired storage location 820 . The vehicle 100 activates the transfer mechanism 210 to move the item from the storage location 820 onto the vehicle 100 . The storage location 820 may contain items at the front end of the storage location 820, separating the vehicle 100 from the desired items at the storage location 820. Thus, vehicle 100 moves the item at the front end of storage location 820 onto vehicle 100, which in turn places the desired item at the front end of storage location 820. The vehicle 100 then drives vertically to a storage location 820 which has an open area to receive the items. The vehicle 100 then moves the items toward the open location. The vehicle 100 then moves vertically to the storage location 820 containing the desired item and activates the loading / unloading mechanism 140 to move the desired item onto the vehicle 100 . After retrieving the desired item, the vehicle 100 activates the vertical drive mechanism 140 to move down the vertical row 810 until the vehicle 100 engages a horizontal drive surface, such as a floor surface. The horizontal drive of vehicle 100 is engaged to drive vehicle 100 across aisle 850 and through openings in vertical row 810 . After exiting aisle 850 , vehicle 100 continues driving horizontally and exits storage rack 800 . For example, vehicle 100 continues along path 860 across aisle 850 , passes under one or more additional storage racks 800 , and crosses one or more additional aisles 850 . Following such a path 860, the path 860 of the vehicle 100 is controlled so that the width of the vehicle 100 is aligned with the opening of each vertical row 810 that the vehicle 100 passes through. Alternatively, while the vehicle 100 remains under the storage rack 800, the vehicle 100 rotates about a vertical axis that rotates the vehicle 100 while being aligned with a path 860 along the aisle 850. The vehicle 100 then passes under one or more vertical rows 810 of storage racks 800 until the vehicle 100 exits from under the storage racks 800 .

[0123] After the vehicle 100 leaves the storage rack 800 , the central controller 450 may control the vehicle 100 to move the vehicle 100 to one of a number of work sites 500 . At the work station 500, the vehicle 100 is presented to an operator who removes one or more items from the vehicle 100. The central controller 450 then controls the vehicle 100 to move along a route 860, store the item it is carrying in an open storage location 820 within the storage rack 800, and retrieve the next item from another storage location 820. In this manner, the central controller 450 provides control signals to the multiple vehicles 100 to cause the vehicles 100 to move along one of the multiple routes 860, retrieve multiple items from the storage location 820, and transport the items to the work site 500. <Control Process>

[0124] FIG. 11 is a block diagram showing the subsystems of the plurality of transport vehicles 100-1 to 100-n. Each vehicle 100, like delivery vehicle 100-1, may include a central processing unit (CPU) 286, a memory 287, and a communication interface 284. The communication interface 284 comprises one or more wireless transceivers conforming to a corresponding wireless transmission protocol such as IEEE 802.11, and the communication interface 284 of the vehicle 100 is used to communicate with other vehicles 100, such as in a peer-to-peer topology, or with the central control unit 450. In the latter regard, delivery vehicles 100-1 through 100-n include position sensors 280 and object sensors 282 and use communications interfaces 284 to communicate sensed information to a master controller, such as central controller 450. The position sensor 280, in one or more embodiments, includes an on-board image sensor that determines when the vehicle 100 passes over a fiducial mark located on the underlying support surface. However, delivery vehicles 100-1 through 100-n may utilize signal triangulation and / or other conventional techniques to determine, or allow central controller 450 to determine, their respective positions relative to one another.

[0125] Each delivery vehicle 100-1 includes a power source 288, which may be, for example, a rechargeable power source comprising an ultracapacitor, one or more batteries, or a combination thereof. The power supply 288 then drives the first drive motor 230 of the first drive system. The first drive system is driven by the first drive motor 230 and may further include gears used, for example, to drive the vehicle 100 vertically. In this example, power supply 288 also provides power to a second drive system, which includes a second drive motor 250a and a third drive motor 250b.

[0126] CPU 286 may include one or more commercially available microprocessors or microcontrollers that facilitate data processing and storage. Various support circuits facilitate the operation of CPU 286 and may include one or more clock circuits, power supplies, cache, input / output circuits, etc. The memory 287 includes at least one of read-only memory (ROM), random access memory (RAM), disk drive storage, optical storage, removable storage, and the like.

[0127] FIG. 12 is a simplified block diagram of a central controller 450 capable of coordinating the assignment and execution of inventory control task activities by multiple vehicles 100 and subassemblies (e.g., mobile racks 700 or flow racks 600), such as those assigned to AGV task groups 902-1, 904-1, 906-1, and 908-1, in response to instructions received from a warehouse automation system (WMS) 940. The central controller 450 comprises a central processing unit (CPU) 951, support circuits 955, memory 952, user interface components 954 (e.g., a display with a touch screen or a separate keyboard), and a communications interface 953. Server 450 includes one or more wireless transceivers conforming to a corresponding wireless transmission protocol, such as IEEE 802.11.

[0128] The CPU 951 may include one or more commercially available microprocessors or microcontrollers that facilitate data processing and storage. Various support circuits 955 facilitate the operation of CPU 951 and may include one or more clock circuits, power supplies, cache, input / output circuits, etc. The memory 952 includes at least one of read-only memory (ROM), random access memory (RAM), disk drive storage, optical storage, removable storage, and the like. This memory 952 includes an operating system 956 and one or more inventory control applications. The inventory management application includes a task agent manager module 960 , an AGV traffic management module 970 , a condition / event monitoring module 980 , and a data repository 990 .

[0129] The task agent manager module 960 is composed of an inventory control task processor 961, a dynamic inventory input analysis program 962, a subtask order identifier 963, a task priority manager 964, an event notification detector 965, a state transition detector 966, and an AGV selector 967. Additionally, inventory control task processor 961 processes inventory control task requests received from WMS 940 through execution of instructions by CPU 951 .

[0130] Traffic management of the AGVs is performed by a traffic management module 470 of the central controller 450 . In such a case, position, speed and direction data is collected from the vehicle 100 by the central controller 450 at regular intervals. The position data is analyzed and a route section selector 974 selects a route for each vehicle 100 over the next control interval to ensure there are no collisions with other vehicles 100, personnel or fixed structures. Updated instructions for route selection, including course and heading, are communicated back to the vehicle 100 by the central controller 450 . However, the vehicle 100 does not rely on the central controller 450 for relative positioning commands, but rather only for orientation and task assignment; the vehicle 100 instead relies on its internal data collection and spatial analysis capabilities.

[0131] To facilitate the aforementioned operations, the central controller 450 of FIG. 12 includes a data repository that reflects the up-to-date locations of all inventory items for which management and placement responsibility has been assigned by the WMS, as well as a map of vehicle locations within the facility. Additionally, to facilitate scheduling preventative maintenance procedures, operational statistics are collected for all AGVs with moving parts so that parts can be inspected, lubricated, and / or replaced at regular intervals.

[0132] The methods described herein may be reordered and various elements may be added, rearranged, combined, omitted, or otherwise modified. All examples described herein are offered in a non-limiting manner. Various modifications and variations may be made. Implementations of several embodiments have been described in the context of specific embodiments. These embodiments are illustrative and not meant to be limiting. Many variations, modifications, additions and improvements are possible. Therefore, multiple examples of components described herein as one example may apply. Boundaries between various components, operations and data stores are somewhat arbitrary, and particular operations are illustrated in particular contexts. Different allocations of functionality are contemplated and may fall within the scope of the claims set forth below. Finally, structures and functions presented as separate components in the illustrative examples may be implemented as a combined structure or component. These and other variations, modifications, additions, and improvements may fall within the scope of the embodiments as defined in the claims that follow.

[0133] Accordingly, while the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, which scope is determined by the following claims.

Claims

1. 1. A method of transporting items to a storage location and retrieving items from said storage location, comprising: providing the transport vehicle having a horizontal drive mechanism and a vertical drive mechanism including a front rotating member adjacent a front end of the transport vehicle and a rear rotating member adjacent a rear end of the transport vehicle; providing a first vertical track on a first side of the first vertical row having a drive member configured to cooperate with the front rotating member to drive the transport vehicle upward; providing a second vertical track on a second side of the first vertical row having a drive member configured to cooperate with the rear rotating member to drive the transport vehicle upward; the vertical drive mechanism and the first and second vertical tracks are configured such that when the vertical drive mechanism is rotated and misaligned, the vertical tracks impede displacement of the transport vehicle along the horizontal tracks; further comprising the step of aligning the vertical drive mechanism, wherein the step of aligning the vertical drive mechanism comprises: rotating the front rotating member about a horizontal axis substantially parallel to the horizontal path to align the front rotating member with gaps in the first and second vertical tracks; rotating the rear rotating member about a horizontal axis substantially parallel to the horizontal path to align the rear rotating member with gaps in the first and second vertical tracks; after the step of aligning the vertical drive mechanism, driving the transport vehicle along the horizontal path toward the first vertical track; driving the transport vehicle includes driving the transport vehicle such that the front rotating member passes through the gap in the second vertical track; continuing to drive the transport vehicle along the horizontal path until the front rolling member is in operative engagement with the first track and the rear rolling member is in operative engagement with the second track; rotating the front and rear rotating members to drive the transport vehicle upward toward a first storage location; transferring a first item from the first storage location to the transport vehicle; driving the transport vehicle carrying the first item downward; driving the transport vehicle carrying the first item along the horizontal path so that the rear rolling member passes through a gap in the first vertical track.

2. 2. The method of claim 1, wherein the step of rotating the front and rear rotating members includes the step of synchronously driving the front and rear rotating members to drive the transport vehicle vertically upward while maintaining the orientation of the transport vehicle relative to the horizontal.

3. 3. The method of claim 1 or claim 2, further comprising, after the step of driving the transport vehicle carrying the first item along the horizontal path, driving the transport vehicle out from under a storage rack.

4. 4. The method of claim 1 or claim 3, further comprising, after the step of driving the transport vehicle carrying the first item along the horizontal path, driving the transport vehicle out from under a storage rack.

5. The method of claim 1 , further comprising driving the transport vehicle carrying the first item to a work site and delivering the first item to an operator.

6. 6. The method of claim 1, wherein the step of driving the transport vehicle along the horizontal path includes rotating the plurality of horizontal drive members about horizontal axes that are substantially perpendicular to the horizontal path.

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