Patent Publication Number: US-2019185265-A1

Title: Method and system for automated transport of items

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. Non-Provisional patent application Ser. No. 14/972,722, filed on Dec. 17, 2015 (now U.S. Pat. No. 10,214,354, issued Feb. 26, 2019), which claims priority from and the benefit of U.S. provisional patent application No. 62/093,786, filed on Dec. 18, 2014, the disclosures of which are incorporated by reference herein in their entirety. 
    
    
     BACKGROUND 
     1. Field 
     The exemplary embodiments generally relate to transportation of items, more particularly, to the automated transportation of items between multiple points. 
     2. Brief Description of Related Developments 
     Generally, conventional large scale automated distribution centers that fulfill orders including one or more items (where each item is called an “each” and the picking process of an “each” is referred to as an “each pick”) have a customized storage structures in which automated guided vehicles operate. These customized storage structures are generally expensive, require lengthy installation times and are not easily changed or moved once constructed. In addition, the automated guided vehicles operating within the customized storage structures are generally constrained by the walls or other structure of the customized storage structure. As may be realized, the automated guided vehicles pick cases of items from storage locations of the customized storage structure, as specified in an order, and bring the picked items, as needed, to picking stations where a human picker grabs the required number of items from the cases carried by the automated guided vehicles for fulfilling the order. The automated guided vehicles then return the cases of items to the storage locations of the customized storage structure. 
     Generally there are many conventional automated transportation and storage systems that utilize motorized autonomous transport vehicles to transport products between two or more locations in a warehouse. However, those vehicles may not be fully autonomous in the sense that the customized storage structure contains the automated guided vehicles from leaving the customized storage structure, provides mechanical or other means (e.g. lines on the floor, etc.) of simplifying and/or constraining vehicle motion to one certain areas/directions, and provides alignment between the automated guided vehicle and a product container to make picking/placing of the product container reliable. Those vehicles also may not be safe enough to operate in the presence of humans and/or other equipment, requiring a structure to contain the vehicles or a defined “robot only” area of operation that is away from humans and/or other equipment, decreasing flexibility, efficiency and ease of maintainability/serviceability of the system. As noted above, a customized storage structure that provides these features may be cost prohibitive and may prevent distribution systems from adopting a large scale automated transportation/picking system. These conventional systems may also preclude workers from fulfilling orders using traditional picker-to-goods methods in the same space occupied by the automated guided vehicles in order to best optimize the system for order fulfillment efficiency. 
     It would be advantageous to have a low cost, retrofitable automated transportation system for transferring items between multiple locations in a distribution center that also allows, if desired, for simultaneous picker-to-goods methods in the same space as the automated transportation system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing aspects and other features of the disclosed embodiment are explained in the following description, taken in connection with the accompanying drawings, wherein: 
         FIG. 1A  is a schematic illustration of a distribution center in accordance with aspects of the disclosed embodiment; 
         FIG. 1B  is a schematic illustration of a portion of the distribution center of  FIG. 1A  in accordance with aspects of the disclosed embodiment; 
         FIG. 1C  is a schematic illustration of a portion of the distribution center of  FIG. 1A  in accordance with aspects of the disclosed embodiment; 
         FIG. 2  is a schematic illustration of an automated guided vehicle in accordance with aspects of the disclosed embodiment; 
         FIG. 3  is a schematic illustration of a portion of the distribution center of  FIG. 1A  in accordance with aspects of the disclosed embodiment; 
         FIG. 3A  is a schematic illustration of a portion of the distribution center of  FIG. 1A  in accordance with aspects of the disclosed embodiment; 
         FIG. 4  is a schematic illustration of a portion of the distribution center of  FIG. 1A  in accordance with aspects of the disclosed embodiment; 
         FIG. 4A  is a schematic illustration of a portion of the distribution center of  FIG. 1A  in accordance with aspects of the disclosed embodiment; 
         FIG. 5  is a schematic illustration of a portion of the distribution center of  FIG. 1A  in accordance with aspects of the disclosed embodiment; 
         FIG. 6  is a schematic illustration of automated guided vehicle navigation in accordance with aspects of the disclosed embodiment; 
         FIG. 7  is a schematic illustration of automated guided vehicle navigation in accordance with aspects of the disclosed embodiment; 
         FIG. 8  is a schematic illustration of automated guided vehicle navigation in accordance with aspects of the disclosed embodiment; 
         FIG. 9  is a schematic illustration of automated guided vehicle navigation in accordance with aspects of the disclosed embodiment; and 
         FIG. 10  is a flow diagram in accordance with aspects of the disclosed embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1A  is a schematic illustration of a distribution center or warehouse  1  in accordance with aspects of the disclosed embodiment. Although the aspects of the disclosed embodiment will be described with reference to the drawings, it should be understood that the aspects of the disclosed embodiment can be embodied in many forms. In addition, any suitable size, shape or type of elements or materials could be used. 
     The aspects of the disclosed embodiment described herein provide a system for automating order fulfillment, replenishment, and/or returns in a warehouse  1  without requiring large changes in the physical infrastructure of an existing warehouse  1 . The aspects of the disclosed embodiment include one or more automated guided vehicles  10  that pick, place or otherwise move storage containers  40  (which hold any suitable products or goods and are configured for placement in a storage space on a storage rack/shelf) from one place to another within the warehouse  1 . In one instance, the aspects of the disclosed embodiment are retrofit to an existing warehouse structure (e.g. the aspects of the disclosed embodiment utilize an existing storage structure which includes at least storage racks with storage spaces and a floor). The automated guided vehicles  10  are deployed in the existing warehouse structure to move throughout the warehouse  1  for moving the storage containers  40  according to instructions from any suitable controller  2  that is in communication with the automated guided vehicles  10  in any suitable manner (such as for example, through a wireless or wired communication connection). The automated guided vehicles are deployed on a single level of the warehouse  1  (as illustrated in  FIG. 1A ) or on multiple levels of the warehouse  1  where mezzanine platforms  70  are connected to the existing warehouse structure to form the multiple levels (as illustrated in  FIG. 1B ). Automated guided vehicle access to each of the multiple levels, as will be described in greater detail below is provided through an automated guided vehicle vertical transport system. In other aspects, the vertical transport system could be used to only move the storage containers  40  between levels where containers  40  are transferred between the automated guided vehicles  10  and the vertical transport system. In another instance the aspects of the disclosed embodiment are implemented during construction of a new warehouse so that automation of the existing or new warehouse is achieved with common low cost structures compared to conventional automated warehouse systems having customized storage structures. 
     As can be seen in  FIG. 1A  the warehouse  1  includes a storage array  20  including one or more stacked racks  30 . Each of the stacked racks  30  includes one or more (e.g. at least one) storage locations positioned on the rack in a predetermined location (e.g. predetermined storage locations  30 S) such that each of the predetermined storage locations  30 S is configured to hold or store at least one storage container  40 . The one or more stacked racks  30  are arranged so as to form aisles  50  between the racks  30  where the predetermined storage locations  30 S (and hence the storage containers  40 ) are arranged along the aisles  50 . 
     Referring also to  FIG. 1B , each of the aisles  50  includes a base or floor  60 . One or more mezzanine platforms  70  are disposed above the floor  60  and are connected to the stacked racks  30  in any suitable manner (e.g. by mechanical fasteners, clips, etc.) such that at least the stacked racks support the mezzanine platforms  70 . In other aspects, columns or other support structure are provided for supporting the mezzanine platforms  70 . The mezzanine platforms  70  are spaced apart from each other and with the floor by a distance D to form multiple levels of storage and to provide human picker access to the predetermined storage locations  30 S of each of the racks  30  along the one or more aisles  50 . In other words the levels of storage or mezzanines  70  are separated by a height D that makes human access into at least the aisles  50  of each level of storage comfortable for manual picker-to-goods order fulfillment tasks (e.g. a human picking goods from storage containers located substantially directly in the storage spaces  30 S) and for servicing or maintaining one or more of the automated guided vehicles  10  located within the rack array  20 . As will be described in greater detail below, the one or more automated guided vehicles  10  are provided and configured to traverse the floor  60  and the one or more mezzanine platforms  70  to access each of the predetermined storage locations  30 S of the storage array  20 . As will also be described in greater detail below the one or more automated guided vehicles  10  are configured to hold and transport one or more storage containers  40  to and from the predetermined storage locations  30 S. As may be realized, referring to  FIGS. 1B and 1C , any suitable vertical transport system VTS is provided that connects the floor  60  to the mezzanine platforms  70  and that connects the mezzanine platforms  70  to other ones of the stacked mezzanine platforms  70 . In one aspect the vertical transport system VTS includes one or more of vertical lifts VTSL and ramps VTSR. In one aspect the vertical lifts VTSL are configured for automated guided vehicle  10  roll on and roll off (in a manner similar to an elevator that stops at each floor to allow the vehicles to roll onto an elevator platform and to roll off of the elevator platform). In other aspects the vertical lifts VTSL have any suitable configuration for transporting the automated guided vehicles  10  and/or the containers  40  between the storage levels formed by the floor  60  and mezzanine platforms  70 . In one aspect one or more ramps VTSR having any suitable configuration are provided between the storage levels so that the automated guided vehicles  10  traverse the ramp(s) VTSR between the storage levels. In one aspect each of the ramps VTSR includes a surface SS substantially similar to surfaces  60 S and  70 S of the floor  60  and mezzanine platforms  70  (as will be described below). In other aspects, the storage containers  40  are transferred from a storage location  30 S to a level (such as the floor  60  and/or a mezzanine platform  70 ) on which the automated guided vehicle  10  is located by a storage container transport system  99  that only moves the storage containers  40 . For example, the storage container transport system  99  includes one or more of a ramp, conveyor, lift or any other suitable vertical transport that interfaces with the storage locations  30 S for picking and placing storage containers from and to the storage locations  30 S and that interfaces with the automated guided vehicles  10  for transferring the storage containers  40  to and from the automated guided vehicles  10 . In one aspect the storage container transport system  99  includes any suitable transfer unit for transferring containers  40  to and from the storage spaces  30 S while in other aspects the storage spaces  30 S/rack  30  include any suitable transfer unit for transferring containers  40  to and from the storage container transport system  99 . 
     The floor  60  and the one or more mezzanine platforms  70 , along which the one or more automated guided vehicles  10  travel, each include an undeterministic traverse surface  30 S,  70 S. The automated guided vehicle  10  is configured, as will be described below, so that the undeterministic traverse service  30 S,  70 S provides holonomic selectable paths  75  for the automated guided vehicle substantially everywhere on the respective undeterministic traverse surfaces  30 S,  70 S. Here the term holonomic selectable paths means that any path anywhere on the surface  30 S,  70 S is substantially equal to each other with respect to the surface  30 S,  70 S so that the automated guided vehicle  10  is free to select a path everywhere on the surface subject to other parameters such as obstacles, edges or the racks or walls of the warehouse, optimum pathway way points, etc. As will also be described in greater detail below, each of the holonomic selectable paths  75  is freely selectable by the automated guided vehicle  10  and/or a central controller  2  (which is in communication with the automated guided vehicle  10 ) for traverse along the aisles of the floor  60  and/or mezzanine platforms  70 . 
     Referring now to  FIGS. 2 and 4  each automated guided vehicle  10  includes a frame  10 F, a plurality of wheels  10 W (at least one of which is a drive wheel  252 D) and a gripper/manipulator or effector  10 A. In one aspect the gripper is movable (e.g. a movable container grip or container manipulator subsystem, see also  FIG. 2 ) that is configured to engage the storage containers  40  so as to pick and place one of the storage containers  40  to and from a storage location  30 S on the racks  30 . The gripper  10 A includes one or more degrees of freedom for effecting transfer of containers  40  to and from the automated guided vehicle  10  at one or more predetermined heights (e.g. such as a height of an order fill station, ergonomic human picker height, storage space height, etc.). In one aspect the gripper  10 A includes at least two degrees of freedom for effecting extension of the gripper  10 A along for example, a Y axis and a Z axis (e.g. where an X axis of the automated guided vehicle is coincident with a longitudinal path of travel of the automated guided vehicle and the Y axis is transverse to X axis—see  FIG. 1A ). The automated guided vehicle  10  is, in one aspect configured to extend the gripper  10 A along the Y axis for transferring containers to and from the storage spaces  30 S while in other aspects, the automated guided vehicle  10  is configured to extend the gripper  10 A along the X axis for transferring containers to and from the storage spaces  30 S. In one aspect the automated guided vehicle is configured to extend the gripper  10 A along the Z axis where the automated guided vehicle  10  moves along one or more of the X or Y axes for at least partially effecting positioning of the gripper  10 A relative to the container  40  (e.g. to engage and move the container  40  along one or more of the X and Y axes, in and out of the storage spaces  30 S). In one aspects the automated guided vehicle  10  rotates so that the X axis of the automated guided vehicle  10  faces the storage locations  30 S. In one aspect the gripper  10 A includes a storage container support  10 AG configured to pick and hold at least one storage container  40 . As may be realized, in one aspect, the automated guided vehicle  10  includes a mast  10 AM along which the gripper  10 A rides for accessing or otherwise reaching storage containers  40  at all heights on each level of storage (see  FIG. 1B  where each level of storage includes multiple levels of stacked storage spaces  30 S). In one aspect the mast  10 AM provides the gripper  10 A with a Z axis stroke range that positions a storage container  40  held by the gripper  10 A at a human picker upper ergonomic pick and place height so that the human picker picks and places items to and from the storage container  40  (or order fill container) substantially without ergonomic distress. In one aspect each of the storage containers  40  are substantially the same to other ones of the storage containers  40  while in other aspects each of the storage containers  40  is different (e.g. constructed of a different material, has different dimensions, has a different shape, etc.) than at least one other storage container  40 . In any event, the gripper  10 A is configured to pick and hold the storage containers  40  in any suitable manner. 
     Each automated guided vehicle  10  also includes a drive subsystem  252 , a guidance subsystem  254 , an obstacle detection subsystem  256 , a controller subsystem  258  and a power supply  250 . The subsystems of the automated guided vehicle  10  include sensors, as will be described below, that provide the automated guided vehicle awareness of (e.g. the ability to detect) the environment around the automated guided vehicle  10  so that the automated guided vehicle knows its position and orientation with respect to the warehouse substantially at all times. For example, the automated guided vehicles know their surrounding at a time where the automated guided vehicles receive a command from, for example, the controller  2  for picking and transporting a storage container  40  and prior to navigating. Based on the awareness of its surroundings the automated guided vehicle  10  selects a path  75  based on any suitable optimizing algorithm resident in, for example, controller subsystem  258  of the automated guided vehicle  10  and then iteratively updates the path (e.g. the path is changed from the selected path as needed) based on, for example, information obtained from the automated guided vehicle sensors and any detected obstacles, transients and waypoints. 
     As may be realized, the sensors provide alignment between the automated guided vehicles  10  and the storage containers  40  and/or storage spaces  30 S to or from which a storage container  40  is picked or placed. The sensors also prevent the automated guided vehicle  10  from colliding with other automated guided vehicles  10 , warehouse equipment (e.g. such as racks, forklifts, etc.), humans or other obstacles. As may be realized, although humans are not required to be in the storage aisles  50  while the automated guided vehicles  10  are moving storage containers  40  within the aisles  50  and other portions of the warehouse  1 , the aspects of the disclosed embodiment do not restrict human access within zones of movement of the automated guided vehicles  10  during operation of the automated guided vehicles  10 . The fully autonomous nature of the automated guided vehicles  10  does not require substantially any mechanical structure to contain the automated guided vehicles or in other words, the operation of the automated guided vehicles  10  does not hinder human access to the storage spaces and vice versa (the automated guided vehicles comingle with humans in a common space of the automated storage system). 
     The power supply is any suitable power supply, such as a rechargeable power supply, configured to provide power to the automated guided vehicle and all of its subsystems  252 ,  254 ,  256 ,  258 ,  260 . The controller subsystem  258  is any suitable control system such as a microprocessor-based controller subsystem configured to control operation of the automated guided vehicle  10  in performing programmed behaviors such as those described herein. The controller subsystem  258  is configured (e.g., programmed) to perform various functions, including effecting the transport of items with the automated guided vehicle  10  between endpoints. The controller subsystem  258  is connected to and responsive to the output of guidance subsystem  254  and the output of obstacle detection subsystem  256 . The controller subsystem  258  controls the drive subsystem  252  to maneuver the automated guided vehicle  10  (as described herein) to prescribed endpoint locations such as one or more predetermined storage spaces  30 S and order filling station  80 . The controller subsystem  258  is also connected to a manipulator subsystem  260  (of which the gripper  10 A is a part of) such that the manipulator subsystem  260  is commanded by the controller subsystem  258  to pick or place a container  40  with the gripper  10 A from any suitable container holding location. The controller subsystem  258  is connected to the controller  2  in any suitable manner such as through a wired or wireless connection for receiving storage container picking/placing and transport commands from the controller  2 . For example, in one aspect the controller  2  includes warehouse management system WMS configured to receive orders and to identify storage containers  40  (that include products associated with the orders) and the corresponding storage locations  30 S for the identified storage containers  40 . In one aspect the controller  2  also includes, or is otherwise connected to, an automated guided vehicle manager AVM that is configured to command the automated guided vehicles  10  so that the automated guided vehicles  10  traverse the floor  60  and/or mezzanine platform(s)  70  to the corresponding storage locations  30 S for picking at least one of the identified storage containers  40 . In one aspect, the automated guided vehicle manager AVM is in communication with the automated guided vehicles in any suitable manner, such as a wired or wireless connection. As may be realized, in response to a command from the controller  2  (or automated guided vehicle manager AVM) the automated guided vehicles  10  generate respective selected paths on the undeterministic traverse surface(s)  60 A,  70 S that corresponds to the storage location  30 S of the identified storage container  40  (e.g. one automated guided vehicle is commanded to pick or place at least one identified storage container) by selecting from the holonomic selectable paths  75 . As will be described below, the respective selected path is modified as by the automated guided vehicle  10  depending on a sensing or detection of transient features affecting the selected path so that changes to the selected path are effected. In one aspect, the controller  2  also includes an automated human picker manager HPM communicably connected with at least one human picker HP. The automated human picker manager HPM is in communication with the automated guided vehicle manager AVM and is configured to command the at least one human picker to work in concert with the at least one autonomous guided vehicle  10  in any suitable manner such as described in, for example, U.S. provisional patent application No. 62/063,825 filed on Oct. 14, 2014 and entitled “Storage Material Handling System”, the disclosure of which is incorporated herein by reference in its entirety. 
     The drive subsystem  252  is mounted to the frame (and which includes wheels, at least one of which is a drive wheel) for maneuvering the frame  10 F (and hence the automated guided vehicle  10 ). In one aspect the drive subsystem  252  is a differential drive system having two independently operable coaxial drive wheels  252 D and at least one roller wheel  10 W for balance or support of the frame  10 F. The drive wheels  252 D are driven together or independently by one or more motors and any suitable drive transmission controlled by, for example, the controller subsystem  258 . In other aspects, the drive subsystem  252  includes steered wheels or any other suitable drive configuration for effecting movement of the automated guided vehicle  10  through the warehouse  1 . 
     The guidance subsystem  254  is mounted to the frame  10 F for interacting with the drive subsystem  252  and is configured to effect navigation of the automated guided vehicle  10  in any suitable manner such as those described in U.S. Pat. No. 8,676,425 and U.S. patent application Ser. No. 13/285,511 filed on Oct. 31, 2011 the disclosures of which are incorporated herein by reference in their entireties. Referring also to  FIG. 6 , in one aspect the guidance subsystem includes a simultaneous location and mapping (SLAM) navigation system that provides the automated guided vehicle  10  a global coordinate or reference frame REF with respect to the warehouse  1 . Here the automated guided vehicle guidance is effected through a coordinate system that lacks physical markers or beacons. 
     Referring also to  FIGS. 7-9 , in one aspect, the guidance subsystem  254  includes one or more of a marker detecting sensor(s)  254 S 1  and/or a beacon sensor(s)  254 S 2 . In one aspect the marker detecting sensor(s)  254 S 1  are configured to detect the position of a marker such as a retro-reflective tape (or other suitable marker such as a capacitive or inductive marker or other optical marker including but not limited to barcodes) laid on the floor  60  (e.g. on the undeterministic traverse surfaces  60 S), on the mezzanine platform  70  (e.g. on the undeterministic traverse  70 S) and/or on any other suitable surface such as the walls of the warehouse  1  and/or on the racks  30 . In one aspect the marker detecting sensor(s)  254 S 2  include one or more of a photodiode-based sensor, one or more radiation sources (e.g., LEDs), inductive sensors, capacitive sensors, barcode reader, etc. to detect the marker. In one aspect the beacon sensor  254 S 2  includes any suitable transmitter and/or receiver configured to actively or passively detect any suitable radio frequency beacons  12  (or other suitable beacon such as an infrared, laser or other optical beacon). As can be seen in  FIG. 7 , for example, the guidance subsystem  254  includes a plurality of active (e.g. having a radio frequency or other (e.g., infrared) beacon transmitter) or passive (e.g. configured to passively return a signal) beacons or tags  12  that are located at any suitable location of the warehouse  1  (such as on the racks, on walls, on the floor  60 , on the mezzanine platform  70 , ceiling, etc.). In this case, the beacon sensor(s)  254 S 2  are configured to detect signals from beacons or detect the beacons themselves for locating the automated guided vehicle  10  relative to the storage spaces  30 S, the racks  30 , the order filling stations  80  and any other suitable structure of the warehouse  1 . By way of example, where beacons  12  are used, each automated guided vehicle  10  should secure a line of sight to one or more beacons  12 , for example, an origin and/or destination beacon could be visible (either optically or through radio waves) to the automated guided vehicle  10  for at least a period of time. The automated guided vehicle  10  moves directly from one beacon (e.g. the origin beacon) toward the other (e.g. the destination beacon) unless an obstacle intervenes as described herein. In one aspect each beacon  12  establishes a respective coordinate system, where the beacon is the origin of the respective coordinate system. Angular encoding (or any other suitable encoding) is employed to specify the axes of the beacon coordinate system. The beacon coordinate system enables robots to queue along a particular ray whose origin is the beacon. Angle encoding can also enable other useful properties. 
     Referring to  FIG. 8 , in one aspect, the guidance subsystem  254  includes shorter range active or passive beacons (which are substantially similar to those described above) and pathways established by any suitable markers  14  (such as those described above) attached to, for example, the floor and/or other suitable surface (e.g. walls, racks, etc.) so that the automated guided vehicles are provided with a rough global reference frame REF. Here the beacon  12  and marker  14  arrangement simplifies sensor range requirements compared to SLAM navigation. Referring also to  FIG. 9  the guidance subsystem  254  includes, in one aspect, an ad hoc marker system including one or more markers  16  laid on the floor and/or other suitable surface (e.g. walls, racks, etc.), in some cases temporarily. A route marker  14  indicating an automated guided vehicle  10  path is employed in situations where either a line of sight between beacons does not exist or traveling in a straight path between beacons is not desired. For example, a route marker enables an automated guided vehicle  10  to avoid a ditch at a construction site. As may be realized, the automated guided vehicle  10  can illuminate, for example, a tape or line using, e.g., conventional IR LEDs. In aspect the automated guided vehicle  10  detects the tape or line using a position-sensitive detector composed of discrete components (i.e., not a camera) to servo on the tape or line. The detector measures the degree of retro-reflectivity in view to eliminate false positives. In one aspect, the automated guided vehicle  10  servo on the line directly. In one aspect, the automated guided vehicle  10  can servo at any selected offset with respect to the line. Offset servoing enables two important properties. When placing the line to mark the automated guided vehicle  10  path, workers need not allow space between line and objects. Any time the automated guided vehicle  10  finds its path partially blocked by an object, the automated guided vehicle  10  will increase its offset from the line so that it can follow the line without colliding with the object. A second feature enabled by offset following allows two automated guided vehicles  10  that meet while traveling along the line in opposite directions to avoid collision. When the automated guided vehicles  10  determine that a collision is imminent, each can offset its position relative to the line. The automated guided vehicles  10  can thus pass without obstructing each other. 
     As may be realized, in one aspect the automated guided vehicle employs one or more of the navigation system described herein for navigating the warehouse  1  and transporting storage cases  40  from one location to another. In other aspects, the automated guided vehicles include any suitable locating system, such as internal GPS that locates the vehicle within the warehouse  1  space such that an automated guided vehicle  10  and/or controller  2  knows where the location and pose of automated guided vehicle  10  within the warehouse  1  as desired. 
     Referring again to  FIG. 1A , in one aspect, the automated guided vehicle is configured for navigation and path selection using one or more of the holonomic selectable paths  75  described above. For example, the controller subsystem  258  and/or controller  2  is configured to select one or more of the paths  75  based on parameters such as obstacles, edges or the racks or walls of the warehouse, optimum pathway way points, etc. It is noted that where the controller  2  selects the initial path  75  the controller  2  sends any suitable commands to the automated guided vehicle  10  to follow the initially selected path  75 . In one aspect, the automated guided vehicle maintains or modifies the initially selected path  75  by selecting other paths from the holonomically selectable paths available based on, for example, transient obstacles or other information indicating the initially selected path  75  is blocked or otherwise inaccessible. For example, the automated guided vehicle  10  may move to another minimally offset path offset from the originally selected path to avoid a transient obstacle. In one aspect, referring also to  FIG. 2  the controller subsystem  258  is connected to an obstacle detection subsystem  256  of the automated guided vehicle  10 . The obstacle detection subsystem  256  includes one or more optical, capacitive, inductive, etc. sensors  256 S configured to detect other robots and obstacles (e.g. such as walls, racks, human pickers, etc.) within the warehouse  1 . In one aspect the sensor  256 S includes an active IR emitter on one automated guided vehicle  10  that is detected by a receiver on another automated guided vehicle  10 . The components of this system on the two automated guided vehicles  10  is arranged such that the following automated guided vehicle  10  detects the automated guided vehicle  10  in front only when the two are physically close. In one aspect, the obstacle detection subsystem  256  includes one or more range sensors to detect transient features affecting path  75  passage where such transient features include but are not limited to other robots, humans and obstacles. In one aspect, the range sensor(s) is a wide-angle (120 degree) range sensor. Raw range sensor data (in the form of a list of angle and range readings) supplied by the sensor is registered with and processed by a computer processor (e.g., a processor in the controller subsystem  258 ) to return the position of the other robots, humans and obstacles. In response to the sensor data received from the obstacle detection subsystem  256  the controller subsystem  258  is configured to command (e.g. based on the path optimization algorithm noted above) the drive subsystem  252  so that the automated guided vehicle selects paths  75  (e.g. changes path from a selected path) that are unobstructed for transporting one or more storage containers  40  from one point to another. For exemplary purposes only, in one aspect a predetermined automated guided vehicle path  75 PD (which in one aspect is one of the holonomic selectable paths  75 ) is defined by any suitable waypoints (e.g. coordinates, markers, beacons, etc.) between each of the order filling stations  80  and each of the aisles  50  where the automated guided vehicles  10  are instructed by the controller subsystem  258  to follow the predetermined automated guided vehicle path  75 PD unless there is an obstruction in the path  75 PD. Where there is an obstruction in the path (e.g. as detected by the obstacle detection subsystem  256 ) the controller subsystem  258  selects any one of the holonomic selectable paths to avoid the obstacle and continue to a predetermined destination (e.g. storage location  30 S, order filling station  80 , etc.). 
     Referring to  FIGS. 1 and 3-5  the warehouse  1  also includes one or more order filling stations  80 . As will be described in greater detail below, the automated guided vehicles transport the storage containers to and from the order filling stations  80  so that one or more goods are picked from the storage containers (e.g. at the order filling stations  80 ) to fill an order. The order filling stations  80  are connected to the surface  60 S,  70 S of the floor  60  and mezzanine platforms  70  by an automated guided vehicle access way  90  which includes a surface that is substantially similar to surfaces  60 S,  70 S and also provides the holonomic selectable paths along which the automated guided vehicles  10  travel. 
     Referring to  FIG. 5 , each order filling station  80  includes a frame  80 F configured so that, in one aspect, a storage container  40  (e.g. a source container from which goods or SKUs are picked) carried by an automated guided vehicle  10  is positioned at least partly within the frame (e.g. at the human picker upper ergonomic pick and place height) to allow a human picker HP to at least pick goods or products from the storage container  40 . It is noted that where a human picker HP transfer goods at the order filling station  80  the order filling station  80  is be referred to herein as a manual fill station. One or more tables or order fill container supports  510 A,  510 B are disposed agent to or integrally formed with the frame  80 F so as to support one or more order fill containers  540  (e.g. an order container into which goods or SKUs are placed for order fulfillment) at the human picker upper ergonomic pick and place height. As may be realized, the tables  510 A,  510 B and the frame  80 F are arranged so that the human picker is substantially centrally located between the storage container  40  and the one or more order fill containers  540 . Any suitable picking indicator  500  is provided to instruct the human picker HP of, for example, which goods and how many of the goods are to be picked and into which order fill containers  540  the goods are to be placed. As may be realized, after the human picker HP picks the required goods from the storage container  40 , the automated guided vehicle  10  carrying that storage container  40  moves away from the order filling station  80  so that a new automated guided vehicle  10  with a different storage container  40  takes its place thereby providing the human picker HP with a continuously changing selection of goods or SKUs that are needed for fulfilling orders. As may also be realized, the order filling stations  80  are arranged in any suitable positions relative to each other and to the storage spaces that facilitates at least automated guided vehicle transport of storage containers  40  (which as described above are configured for insertion and removal from storage spaces of a shelf) between each of the order filling stations  80  and the storage spaces  30 S. 
     Referring to  FIG. 3 , in one aspect the tables  510 A,  510 B are replaced with one or more automated guided vehicles  10 ′ (which are substantially similar to automated guided vehicles  10 ) that support order fill containers  540  at the human picker upper ergonomic pick and place height. In this aspect, the human picker HP picks goods from a common storage container  40  for placement into multiple order fill container  540 . Here the automated guided vehicles  10 ′ (e.g. once one or more goods are transferred into the order fill container at the order filling station  80 ) wait at the order filling stations for additional goods to be placed in the order fill container (e.g. such as the next SKU to arrive at the order filling station), transport an order fill container to a shipping station (e.g. where the order fill containers are one or more of sealed, placed on pallets, loaded onto a shipping vehicle, etc.) or to another order filling station  80  for the receipt of additional goods (e.g. other SKUs) into the order fill container  540 . 
     As may be realized, referring to  FIG. 3A , in one aspect the locations of the storage container  40  and the order fill containers  540  are reversed. For example, the automated guided vehicles  10 ′ each support a storage container  40  and the automated guided vehicle  10  supports an order fill container. Here the human picker HP picks goods or SKUs from the storage containers  40  held on the automated guided vehicles  10 ′ for placing multiple SKUs into the order fill container held by automated guided vehicle  10 . In other words goods are picked from a plurality of storage containers  40  and placed into a common order fill container  540  at the order filling station  80 . Here after the human picker HP picks items from an automated guided vehicle&#39;s storage container  40 , the automated guided vehicle  10  moves away from the order filling station  80  so that a new automated guided vehicle  10  with a different storage container  40  takes its place thereby providing the human picker HP with a continuously changing selection of containers  40  each holding the same goods or SKUs that are needed for fulfilling orders (e.g. one container holds one or more pieces of a first item, one container holds one or more pieces of a second different item, etc.). 
     Referring to  FIGS. 4 and 4A , in one aspect the human picker HP is replaced with an automated pick/place robot  400  mounted to, or otherwise connected to, the frame  80 F to form an automatic fill station. The pick/place robot  400  is any suitable transfer robot configured to pick goods from one container for placement in another container. The pick/place robot  400  is connected to the controller  2  in any suitable manner, such as through a wired or wireless connection, for receiving pick/place commands effecting the transfer of goods for order fulfillment at the order filling stations  80 . As may be realized,  FIG. 3A  illustrates the pick/place robot  400  transferring multiple goods from a common storage container  40  for placement into multiple order fill containers  540  in a manner similar to that described above with respect to the human picker HP. Similarly,  FIG. 4A  illustrates the pick/place robot  400  transferring multiple goods from multiple storage containers for placement into a common order fill container  540  in a manner similar to that described above with respect to the human picker HP. As may be realized, the inclusion of a pick/place robot  400  in the order filling station  80  provides a completely automated picking system with little or no need for human intervention. In addition, any conveyors that are typically used to move containers around and through a robotic picking cell are replaced entirely or at least in part with the automated guided vehicles  10 . 
     As may be realized, once goods are removed from the storage containers  40  at the order filling stations  80  the automated guided vehicles  10  are configured to (or otherwise instructed to by, for example, controller  2 ) return the storage containers to a storage space  30 S (e.g. when goods remain in the storage container). In one aspect, the storage container  40  is returned to the storage space  30 S from which it was picked while in other aspects the storage container  40  is returned to a different storage space  30 S that is different from the storage space from which the storage container  40  was picked. In one aspect the automated guided vehicles  10  are configured to (or otherwise instructed to by, for example, controller  2 ) place an order fill container  540  loaded at the order filling station  80  to a storage space  30 S in the array  20  rather than transport the order fill container to a shipping station or to another order filling station  80 . 
     Referring now to  FIGS. 1A, 1B and 2  an exemplary operation of the automated distribution center described herein (e.g. that includes storage array  20  including stacked racks  30  with predetermined storage locations  30 S that are arranged along at least one aisle  50  having a floor  60 ) is provided. In one aspect, at least one of the aisles  50  is provided with at least one mezzanine platform  70  above the floor  60  ( FIG. 10 , Block  1000 ) where the floor  60  and the mezzanine platform allow human picker HP access to the predetermined storage locations  30 S of the racks  30  along the at least one aisle  50  however, it is noted that in other aspects (as illustrated in  FIG. 1 ) the automated distribution center includes a single level (e.g. floor  60 ). At least one automated guided vehicle is provided ( FIG. 10 , Block  1005 ) where the at least one automated guided vehicle is configured for traverse of the floor  60  and/or the mezzanine platform  70  for accessing the predetermined storage spaces  30 S and is configured for holding and transporting one of the storage containers  40  to and from the storage locations  30 S in a manner substantially similar to that described above. Transport of the storage containers is effected with the at least one automated guided vehicle ( FIG. 10 , Block  1010 ), in a manner substantially similar to that described above, on an undeterministic traverse surface  60 S,  70 S of each of the floor  60  and mezzanine platform  70  where the undeterministic traverse surface  60 S,  70 S provides holonomic selectable paths  75  for the at least one automated guided vehicle  10  substantially everywhere on the undeterministic traverse surface  60 S,  70 S and each of the paths  75  is freely selectable by the at least one automated guided vehicle  10 . At least one order filling station is provided ( FIG. 10 , Block  1015 ) where one or more goods are picked from the storage containers to fill an order. In one aspect, picking and transporting of the storage containers is effected with the at least one automated guided vehicle  10  ( FIG. 10 , Block  1020 ) from one of the storage locations  30 S to the order filling station where the at least one automated guided vehicle traverses the undeterministic traverse surface  60 A,  70 S. For example, upon receipt of an order from the controller  2 , the automated guided vehicle  10  traverses to the storage space  30 S within the storage array  20  where a predetermined storage container  40  (e.g. needed to fulfill the order) is located. The automated guided vehicle  10  picks the predetermined storage container  40 , which contains one or more stock keeping units (e.g. SKUs or goods). The automated guided vehicle  10  is commanded, by for example controller  2  or controller subsystem  258 , to transport the predetermined storage container  40  to a predetermined order filling station  80  where a human picker HP or an automated robot  400  (see e.g.  FIGS. 3 and 4 ) is instructed in any suitable manner (such as described above) to pick a certain number of goods from the predetermined storage container  40  and place those goods into one or more order fill containers  540  disposed adjacent the picker HP or robot  400 . It is noted that the order fill containers  540  are, in one aspect, substantially similar to the storage containers  40  while in other aspects the order fill containers  540  are any suitable container configured for the shipping/transport of goods using any suitable transport carrier (e.g. automobile, aircraft, marine vessel, courier, etc.). As may be realized, returns or replenishment of goods into the storage array  20  is accomplished in a manner substantially opposite that of the order fulfillment process described above. In other aspects, the automated guided vehicles  10  deliver the containers  40  to any suitable conveyors CONV ( FIG. 1 ) that transport the containers  40  to and from the order filling stations  80  so that the human picker HP or the automated robot  400  (see e.g.  FIGS. 3 and 4 ) picks a certain number of goods from the predetermined storage container  40  and place those goods into one or more order fill containers  540  disposed adjacent the picker HP or robot  400 . Here once the goods are removed from the containers  40  the conveyors CONV transfer the containers  40  from the order filling stations  80  to, for example, the automated guided vehicles  10  for returning the containers  40  to the storage spaces  30 S or any other suitable location. 
     As can be seen from the above description, the aspects of the disclosed embodiment provide an autonomous order fulfillment system for use in a warehouse  1  without the typical infrastructure of custom racks/shelving. The aspects of the disclosed embodiment provide for a transportable system (e.g. the system can be easily transported between facilities) that allows for expansion of the system both horizontally and vertically by adding additional racks and/or mezzanine platforms to existing racks. The automated guided vehicles described herein provide for the continual rearrangement of the location of goods within the warehouse based on, for example, any suitable factors such as a demand for a particular good. The automated guided vehicles also eliminate conventional conveyors within the warehouse, including downstream of the picker operation as noted above, where the automated guided vehicles carry and transport the order fill containers  540  from the picking stations  80 . The automated guided vehicles carrying storage containers  40  also provide for batch picking of high demand items such that the automated guided vehicle remains in the area of the order filling stations  80  while travelling between the order filling stations  80  for delivering the high demand items to multiple order filling stations  80 . The autonomous order fulfillment system described herein further provides for unrestricted human access throughout the storage structure while the autonomous guided vehicles remain operative when humans enter areas in which the autonomous guided vehicles operate. In other words, the autonomous guided vehicles work alongside (e.g. comingle with) human pickers allowing simultaneous manual picker-to-goods order fulfillment and robot goods-to-picker order fulfillment for managing peak loads and other order fulfillment efficiency considerations. 
     In accordance with one or more aspects of the disclosed embodiment an automated distribution center includes a storage array including stacked racks with predetermined storage locations, for storage containers, arranged along at least one aisle; at least one of the aisles having a base or floor, and a mezzanine platform above the base or floor, the base or floor and mezzanine platform being configured for human picker access to the predetermined storage locations of the racks along the at least one aisle; at least one automated guided vehicle configured for traverse of the base or floor and the mezzanine platform to the predetermined storage locations along the at least one aisle, and configured for holding and transporting one of the storage containers to and from the storage locations; the base or floor and mezzanine platform each having an undeterministic traverse surface for the automated guided vehicle, and the automated guided vehicle is configured so that the undeterministic traverse surface provides holonomic selectable paths for the automated guided vehicle substantially everywhere on the undeterministic traverse surface, each of the paths being freely selectable by the automated guided vehicle for traversing along the aisle on the base or floor; and an order filling station, where one or more goods are picked from one or more of the storage containers to fill one or more orders; wherein the automated guided vehicle is configured to pick the one of the storage containers from one of the storage locations along the at least one aisle and transport the one of the storage containers on the undeterministic traverse surface between the storage array and the order filling station. 
     In accordance with one or more aspects of the disclosed embodiment the automated guided vehicle is configured for navigation and path selection by simultaneous location and mapping. 
     In accordance with one or more aspects of the disclosed embodiment the automated guided vehicle is configured for navigation and path selection by detecting beacons or passive tags. 
     In accordance with one or more aspects of the disclosed embodiment the automated guided vehicle is configured for navigation and path selection by detecting one or more of beacons, passive tags and markers provided within the automated distribution center. 
     In accordance with one or more aspects of the disclosed embodiment the automated guided vehicle is configured for navigation and path selection by detecting markers provided on the undeterministic traverse surface. 
     In accordance with one or more aspects of the disclosed embodiment the automated distribution center further includes a controller configured to effect one or more of selection and creation of one or more of the holonomic selectable paths by automated guided vehicle. 
     In accordance with one or more aspects of the disclosed embodiment the automated guided vehicle is configured to return the one of the storage containers from the order filling station to one of the storage locations. 
     In accordance with one or more aspects of the disclosed embodiment the one of the storage containers is returned to the same location the one of the storage containers was picked. 
     In accordance with one or more aspects of the disclosed embodiment the one of the storage containers is returned to a different location than the one of the storage containers was picked. 
     In accordance with one or more aspects of the disclosed embodiment the automated distribution center further includes a vertical transport system connecting the mezzanine platform and the base or floor. 
     In accordance with one or more aspects of the disclosed embodiment the vertical transport system configured for automated guided vehicle lift roll on and roll off. 
     In accordance with one or more aspects of the disclosed embodiment the vertical transport system comprises automated guided vehicle ramps. 
     In accordance with one or more aspects of the disclosed embodiment the vertical transport system is configured for automated transport of the storage containers between base or floor and mezzanine platform, where the at least one automated guided vehicle transfers the storage containers to and from the vertical transport system. 
     In accordance with one or more aspects of the disclosed embodiment the automated guided vehicle includes a processor and at least one sensor configured to sense transient features affecting path passage and register such path passage with the processor, in response to which automated guided vehicle changes path from a selected path. 
     In accordance with one or more aspects of the disclosed embodiment the at least one automated guided vehicle is configured to manipulate the one of the storage containers at one or more predetermined heights. 
     In accordance with one or more aspects of the disclosed embodiment the order filling station is connected to the undeterministic traverse surface of the base or floor and mezzanine platform at least in part by an automated guided vehicle access way. 
     In accordance with one or more aspects of the disclosed embodiment the automated distribution center further includes a controller with a warehouse management system configured to receive orders and to identify containers and corresponding storage locations; an automated guided vehicle manager communicably connected with the at least one automated guided vehicle and commanding the at least one automated guided vehicle to the corresponding storage locations for picking at least one of the identified containers; and an automated human picker manager communicably connected with at least one human picker and commanding the at least one human picker to work in concert with the at least one autonomous guided vehicle. 
     In accordance with one or more aspects of the disclosed embodiment in response to a command, the at least one automated guided vehicle one or more of generates and follows a selected path on the undeterministic traverse surface to the corresponding location by one or more of selecting from and being commanded to follow the holonomic selectable paths, and on sensing transient features affecting the path, changes path from selected path. 
     In accordance with one or more aspects of the disclosed embodiment the at least one automated guided vehicle has a movable container manipulator configured to engage the storage containers so as to pick and place the one of the storage containers to and from a storage location on the racks, the movable container grip including at least two degrees of freedom, for effect extension along a y axis and a Z axis. 
     In accordance with one or more aspects of the disclosed embodiment the at least one automated guided vehicle has a movable container manipulator configured to engage the storage containers so as to pick and place the one of the storage containers to and from a storage location on the racks, the movable container grip including at least one degree of freedom, for effecting extension along a Z axis where the at least one automated guided vehicle rotates so that an X axis of the at least one automated guided vehicle faces the storage location. 
     In accordance with one or more aspects of the disclosed embodiment a Z axis stroke range of the movable container manipulator to pick the one of the storage containers located at the storage location is a height from the undeterministic traverse surface to a human picker upper ergonomic pick and place height. 
     In accordance with one or more aspects of the disclosed embodiment the order filling station is a manual fill station. 
     In accordance with one or more aspects of the disclosed embodiment the order filling station is an automatic fill station. 
     In accordance with one or more aspects of the disclosed embodiment an order fill container loaded at the order filling station is carried by the automated guided vehicle and the automated guided vehicle is configured to transport the order fill container to one of the storage locations in the storage array. 
     In accordance with one or more aspects of the disclosed embodiment an automated distribution center includes a storage array including stacked racks with predetermined storage locations, for storage containers, arranged along at least one aisle; at least one of the aisles having a base or floor, the base or floor being configured for human picker access to the predetermined storage locations of the racks along the at least one aisle; at least one automated guided vehicle configured for traverse of the base or floor to the predetermined storage locations along the at least one aisle, and configured for holding and transporting one of the storage containers to and from the storage locations; the base or floor having an undeterministic traverse surface for the automated guided vehicle, and the automated guided vehicle is configured so that the undeterministic traverse surface provides holonomic selectable paths for the automated guided vehicle substantially everywhere on the undeterministic traverse surface, each of the paths being freely selectable by the automated guided vehicle for traversing along the aisle on the base or floor; and an order filling station, where one or more goods are picked from one or more of the storage containers to fill one or more orders; wherein the automated guided vehicle is configured to pick the one of the storage containers from one of the storage locations along the at least one aisle and transport the one or the storage containers on the undeterministic traverse surface between the storage array and the order filling station. 
     In accordance with one or more aspects of the disclosed embodiment the automated guided vehicle is configured for navigation and path selection by one or more of simultaneous location and mapping, by detecting beacons or passive tags, by detecting one or more of beacons, passive tags and markers provided within the automated distribution center. 
     In accordance with one or more aspects of the disclosed embodiment the automated distribution center further includes a controller configured to effect one or more of selection and creation of one or more of the holonomic selectable paths by automated guided vehicle. 
     In accordance with one or more aspects of the disclosed embodiment the automated guided vehicle includes a processor and at least one sensor configured to sense transient features affecting path passage and register such path passage with the processor, in response to which automated guided vehicle changes path from a selected path. 
     In accordance with one or more aspects of the disclosed embodiment the automated distribution center further includes a controller with a warehouse management system or a controller configured to work with an existing warehouse management system, the controller being configured to receive orders and to identify containers and corresponding storage locations; and an automated guided vehicle manager communicably connected with the at least one automated guided vehicle and commanding the at least one automated guided vehicle to the corresponding storage locations for picking at least one of the identified containers. 
     In accordance with one or more aspects of the disclosed embodiment the at least one automated guided vehicle has a movable container manipulator configured to engage the storage containers so as to pick and place the one of the storage containers to and from a storage location on the racks, the movable container manipulator including at least one degree of freedom, for effecting transfer of containers to and from the at least one automated guided vehicle. 
     In accordance with one or more aspects of the disclosed embodiment the movable container manipulator includes at least two degrees of freedom, for effect extension of the movable container manipulator along a y axis and a Z axis. 
     In accordance with one or more aspects of the disclosed embodiment the order filling station is connected to the undeterministic traverse surface of the base or floor by an automated guided vehicle access way. 
     In accordance with one or more aspects of the disclosed embodiment a method for transporting items in a storage array including stacked racks with predetermined storage locations, for storage containers, arranged along at least one aisle having a base or floor, the method includes providing at least one of the aisles with a mezzanine platform above the base or floor, the base or floor and mezzanine platform allowing human picker access to the predetermined storage locations of the racks along the at least one aisle; providing at least one automated guided vehicle configured for traverse of the base or floor and the mezzanine platform to the predetermined storage locations along the at least one aisle, and configured for holding and transporting one of the storage containers to and from the storage locations; effecting transport of the one of the storage containers, with the at least one automated guided vehicle, on an undeterministic traverse surface of each of the base or floor and mezzanine platform where the undeterministic traverse surface provides holonomic selectable paths for the automated guided vehicle substantially everywhere on the undeterministic traverse surface and each of the paths is freely selectable by the automated guided vehicle for traversing along the aisle on the base or floor; providing an order filling station, where one or more goods are picked from one or more of the storage containers to fill one or more orders; and effecting, at least one automated guided vehicle, picking of the one of the storage containers from one of the storage locations along the at least one aisle and transporting the one of the storage containers on the undeterministic traverse surface to the order filling station. 
     In accordance with one or more aspects of the disclosed embodiment the method further includes connecting the order filling station to the undeterministic traverse surface of the base or floor and mezzanine platform with an automated guided vehicle access way. 
     In accordance with one or more aspects of the disclosed embodiment the method further includes effecting automated guided vehicle navigation and path selection by simultaneous location and mapping. 
     In accordance with one or more aspects of the disclosed embodiment the method further includes effecting automated guided vehicle navigation and path selection by detecting beacons or passive tags. 
     In accordance with one or more aspects of the disclosed embodiment the method further includes effecting automated guided vehicle navigation and path selection by detecting one or more of beacons, passive tags and markers provided on one or more of the undeterministic traverse surface and storage array. 
     In accordance with one or more aspects of the disclosed embodiment the method further includes effecting selection of one or more of the holonomic selectable paths with automated guided vehicle. 
     In accordance with one or more aspects of the disclosed embodiment the one of the storage containers from the order filling station is returned, the at least one automated guided vehicle, to one of the storage locations. 
     In accordance with one or more aspects of the disclosed embodiment the one of the storage containers is returned to the same location the one of the storage containers was picked. 
     In accordance with one or more aspects of the disclosed embodiment the one of the storage containers is returned to a different location than the one of the storage containers was picked. 
     In accordance with one or more aspects of the disclosed embodiment the method further includes providing a vertical transport system connecting the mezzanine platform and the base or floor. 
     In accordance with one or more aspects of the disclosed embodiment the method further includes effecting a change from a selected path of the automated guided vehicle with at least one sensor of the automated guided vehicle that senses transient features affecting path passage and registers such path passage with a processor of the automated guided vehicle, in response to which the automated guided vehicle changes path from a selected path. 
     In accordance with one or more aspects of the disclosed embodiment the method further includes transporting the one or more orders from the order filling station to a shipping station with the at least one automated guided vehicle. 
     It should be understood that the foregoing description is only illustrative of the aspects of the disclosed embodiment. Various alternatives and modifications can be devised by those skilled in the art without departing from the aspects of the disclosed embodiment. Accordingly, the aspects of the disclosed embodiment are intended to embrace all such alternatives, modifications and variances that fall within the scope of the appended claims. Further, the mere fact that different features are recited in mutually different dependent or independent claims does not indicate that a combination of these features cannot be advantageously used, such a combination remaining within the scope of the aspects of the invention.